The oligometastatic prostate cancer state is defined as the presence of a number of lesions ≤ 5 and has been significantly correlated with better survival if compared to a number of metastases > 5. In particular, patients in an oligometastatic setting could benefit from a metastates directed therapy, which could control the disease delaying the start of systemic therapies. For this reason, the selection of true-oligometastatic patients who could benefit from such approach is particularly important in this setting. The aim of the present narrative review is to report the current state of the art on the liquid biopsy-derived analytes and their reliability as biomarkers in the clinics for the identification of true-oligometastatic patients. This kind of molecular profiling could refine current developments in the era of precision oncology allowing patients’ stratification and leading to more refined therapeutic strategies.In recent years, a growing interest has been directed towards oligometastatic prostate cancer (OMPC), as patients with three to five metastatic lesions have shown a significantly better survival as compared with those harboring a higher number of lesions. The efficacy of local ablative treatments directed on metastatic lesions (metastases-directed treatments) was extensively investigated, with the aim of preventing further disease progression and delaying the start of systemic androgen deprivation therapies. Definitive diagnosis of prostate cancer is traditionally based on histopathological analysis. Nevertheless, a bioptic sample—static in nature—inevitably fails to reflect the dynamics of the tumor and its biological response due to the dynamic selective pressure of cancer therapies, which can profoundly influence spatio-temporal heterogeneity. Furthermore, even with new imaging technologies allowing an increasingly early detection, the diagnosis of oligometastasis is currently based exclusively on radiological investigations. Given these premises, the development of minimally-invasive liquid biopsies was recently promoted and implemented as predictive biomarkers both for clinical decision-making at pre-treatment (baseline assessment) and for monitoring treatment response during the clinical course of the disease. Through liquid biopsy, different biomarkers, commonly extracted from blood, urine or saliva, can be characterized and implemented in clinical routine to select targeted therapies and assess treatment response. Moreover, this approach has the potential to act as a tissue substitute and to accelerate the identification of novel and consistent predictive analytes cost-efficiently. However, the utility of tumor profiling is currently limited in OMPC due to the lack of clinically validated predictive biomarkers. In this scenario, different ongoing trials, such as the RADIOSA trial, might provide additional insights into the biology of the oligometastatic state and on the identification of novel biomarkers for the outlining of true oligometastatic patients, paving the way towards a wider ideal approach of personalized medicine. The aim of the present narrative review is to report the current state of the art on the solidity of liquid biopsy-related analytes such as CTCs, cfDNA, miRNA and epi-miRNA, and to provide a benchmark for their further clinical implementation. Arguably, this kind of molecular profiling could refine current developments in the era of precision oncology and lead to more refined therapeutic strategies in this subset of oligometastatic patients. Prostate cancer (PCa) is the most commonly diagnosed solid-organ malignancy and the second leading cause of cancer death in men worldwide . Despiteoligometastatic concept was introduced for the first time by Hellman and Weichselbaum in 1995 to describe an intermediate phase between localized disease and extensive metastatic state [Recently, a growing interest is directed towards oligometastatic prostate cancer (OMPC), as the presence of a number of lesions ≤ 5 has been significantly correlated with better survival if compared to a number of metastases > 5 . The oliic state . To dateic state . It is nThe efficacy of local ablative treatments directed towards metastatic lesions (metastases directed treatments—MDTs) in patients with OMPC was extensively investigated, with the aim of preventing the systemic spread of the disease and delaying the start of systemic androgen deprivation therapies (ADT) ,12,13,14With the emerging use of whole-body magnetic resonance imaging (WB-MRI) and Ga-prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT), it has become easier to detect the presence of metastases in patients with early biochemical recurrence ,22,23,24Since the oligometastatic state has a peculiar behavior as compared with heavy burden disease, the existence of distinct underlying biological and molecular mechanisms was hypothesized . The useFor these reasons, the identification of novel biomarkers could potentially improve the treatment of advanced PCa by identifying selected oligometastatic patients who could benefit from MDT. The aim of the present review, which represents an ancillary study of the RADIOSA trial , is to iThe burden of disease in metastatic PCa represents a fundamental prognostic factor , so the The distinction between high and low burden of disease in PCa comes from the CHAARTED trial , a prospBased on CHAARTED trial results, subsequent scientific research supported the initiation of systemic therapies in the case of high-burden disease and of local therapies in low-burden disease ,16. In fHowever, probably due to the underestimation of the real metastatic burden with the standard imaging methods, almost 30% of patients treated with MDT experiment a rapid progression to polymetastatic prostate cancer (PMPC) within 1 year .A first hypothesis argues for a molecular similarity between OMPC and PMPC, considering OMPC merely as an earlier detected metastatic disease state; an alternative hypothesis supports the dual clonal origin of OMPC and PMPC due to the existence of clones of tumor cells with heterogeneous genetic make-up. Recent available data seem to favor the latter, supporting intense efforts to distinguish true OMPC from PMPC based on the use of clinicopathological parameters and other biomarkers in combination with imaging methods already used in clinical practice ,33.The oligometastatic state is recently believed to be a phenotype with an underdeveloped metastatic potential and an inherently slow natural history. In particular, OMPC is considered as an intermediate state between localized PCa and PMPC, with probable differences in genetic and molecular background .The conversion to PMPC is a multistep process promoted by both genetic and epigenetic molecular alterations, involving a consequent series of well-known cellular events: (i) loss of cellular adhesion; (ii) increased motility and invasiveness; (iii) entering the circulation; (iv) invasion and proliferation in organs, a number of cellular adaptations that are part of the broader repertoire of epithelial-to-mesenchymal transition phenotypes ,36,37.Besides other factors such as cytokines and exosomes, metastatic progression seems to also rely on the communication between cancer cells and their local and distant environment through micro Ribo-Nucleic Acids (miRNAs), which post-transcriptionally control gene expression and regulate several steps in the metastatic cascade . FurtherAlthough OMPC represents a spread of tumor cells outside the primary localization, the clone of malignant cells probably does not have the biological requirements to disseminate in multiple sites throughout the body ,41. WhilIn consideration of these assumptions, it is reasonable to approach OMPC with local ablative treatments, avoiding aggressive systemic therapies. The stratification of metastatic PCa patients and the subsequent identification of the subset of patients who can really benefit from MDTs, using both new specific biomarkers and current imaging methods, could represent an intriguing future strategy.For newly diagnosed oligorecurrent PCa, recently available data suggest the administration of local ablative treatments to all the visible metastases. This therapeutic strategy aims to postpone the start of systemic therapy.As mentioned above, it was proven that the treatment of macrometastases reduces the risk of progressive metastasis-to-metastasis seeding, even in men with a controlled primary tumor ,45. HoweTo the best of our knowledge, data from three prospective studies on MDT for oligorecurrent PCa were available at the time of writing ,17,47.In addition, a recent metanalysis explored the role of SBRT in the setting of oligorecurrent PCa. The study comprehends six studies  and a total of 396 patients treated with SBRT. The results of the study showed that patients in an oligometastatic setting might benefit from SBRT both in terms of local and biochemical control.The rationale behind this benefit originates from the assumption that specifically hypofractionated treatments have some novel systemic cell mechanisms, including tumor vascular disruption and increased immune reactivity . Surgical resection represents an alternative approach to MDT. Between studies that explored the efficacy and the safeness of MDT in oligorecurrent PCa, some included surgery as a possible strategy. In particular, in the STOMP  trial, cPelvic lymph nodes are a very common site of recurrence, and lymph node dissection is an elective surgical procedure. In order to limit side effects correlated to this approach and thanks to the advent of next-generation imaging techniques, new surgical strategies are emerging, such as the use of pre-operative hook-wire localization under CT guidance of lymph node detected by PSMA PET .Despite progress, SBRT maintains many advantages over surgery, such as the less invasive procedure, lower side effects, and potentially more cost-effective. However, surgery may be preferred in relation to tumor location .In this scenario, the RADIOSA trial, a randomized phase II clinical trial, is currently ongoing in the recruiting phase . The priWith an estimated recruiting of 160 OCS-PCa patients in 3 years, a sufficient number of blood samples will be collected to perform comprehensive biological patient profiling and possibly provide further insights into the biology underlying oligometastatic state.Definitive diagnosis of PCa is traditionally based on histopathological analysis. Nevertheless, due to the multifocal nature of most PCas , as the Nowadays, even with new imaging technologies allowing an increasingly early detection, the diagnosis of oligometastasis is currently based exclusively on traditional radiological investigations. Nevertheless, objective categorization of true oligometastatic patients from the ones with a trend to progress to poly-metastatic patients relies on the profile of the biological behavior of the tumor; for this purpose, a minimally invasive real-time monitoring method could be beneficial for both patients and clinicians. This could avoid expensive treatments with limited clinical benefit and potential associated toxicity or, alternatively, provide a group of oligometastatic patients with curative treatment.Liquid biopsy has recently emerged as a promising minimally invasive approach allowing to overcome the static bioptic approach and to reflect the dynamic tumor modifications over time, specifically those involving its genomic evolution ,51. ThroHowever, the utility of tumor profiling is currently limited in MPC due to the lack of validated predictive biomarkers . In thisA significant advancement in the development of personalized treatments according to the tumor’s molecular profile was facilitated by the rapid development of next-generation sequencing (NGS) technologies.While Sanger sequencing in the past could satisfy the clinical request of single-gene testing, the advent of more innovative and sensitive approaches fostered the discovery of multiple genetic alterations to be implemented as predictive biomarkers for clinical use .NGS is a high-throughput technology based on a “sequence biosynthesis” principle  and, unlA typical NGS workflow requires the following steps: library preparation, amplification, sequencing, and data analysis. Of note, an in-house validation in any phase of sequencing workflow is required before implementation in a clinical diagnostic routine. This validation process is required not only for the development of different assays and gene panels but also for the bioinformatics pipeline. A more specialized review on NGS is recommended to the readers .Compared to other common transcript quantification methods, such as real-time polymerase chain reaction (PCR), the implementation of NGS in clinical practice brings an increased analytical and clinical sensitivity in the identification of single nucleotide polymorphisms (SNPs) and other genetic alteration in a wild type background.In addition, although PCR-based methods are sensitive and inexpensive, they can only screen for known genetic variants, while NGS has the possibility to screen for unknown variants.Another important consideration is related to the choice of different commercially available gene panels differentiated for clinical purposes, from clinical trials recruiting (10 to 50 genes panels) to the analysis of the whole spectrum of cancer-related genes (>400 genes panels) ,59.Among different NGS approaches, chromatin immunoprecipitation analysis (ChIP-seq) represents an area of emerging interest. A ChIP-seq analysis aims to locate the DNA binding site of any protein and, therefore, investigates epigenetic factors that affect gene expression. This can help uncover the interaction pattern of elements such as transcription factors, structural proteins, or any chromatin-associated protein and gives insights into the epigenetic mechanisms that guide cell differentiation and tumor or metastasis development.CTCs are cancer cells originating from macroscopic tumor sites (either primary or metastases) and released into the bloodstream. Here, CTCs could be found as single CTCs or CTC clusters, with the latter being more often associated with a higher metastatic potential ,61.Since CTCs may reflect the current tumor status, there is a growing interest in identifying genomic alterations in CTCs that could aid the decision workflow in targeted therapies.A recent study by Gkontela et al.  providedA 2020 study by Faugeroux et al.  emphasizA study by Mandel et al.  reportedA significant barrier in the study of CTCs is their relative rarity in the bloodstream with respect to other cells. Therefore, CTCs isolation results as a critical step for their validation as a candidate biomarker. One possible approach is based on immunomagnetic isolation: being CTCs mostly of epithelial origin, they express epithelial cellular adhesion molecule (EpCAM) antigens on the cell membrane, while the background of blood cells does not. A disadvantage of this method is that not all CTCs express EpCAM and that its expression is not always easily detectable and, therefore, part of the CTC population may be lost ,65. AnotAnother isolation method is based on background cell depletion by bead-antibodies against CD45 and CD15, which are not expressed by CTCs .An alternative method for CTCs detection is based on the fact that telomerase expression, characteristic of cancer, and, specifically, the catalytic subunit of human telomerase, namely telomerase reverse transcriptase (hTERT), is mutated in normal human somatic cells but is active in most cancers. This method uses replication-competent adenovirus regulated by hTERT promoter to detect CTCs .However, none of these approaches for CTCs enrichment guarantees a pure and complete population of tumor cells; therefore, a detection method to distinguish CTCs from the background is essential to consistently include CTCs as valuable predictive biomarkers in clinical routine .In this scenario, it was speculated that a combination of methods based on different properties could solve most of the aforementioned issues.Since each of the above-mentioned techniques has intrinsic limitations, and none is robust enough to be considered as the best one, it was proposed that the combination of different approaches can be helpful to solve most of the issues mentioned above . As of tcfDNA, or ctDNA, shed from apoptotic and necrotic cells, comprises both genomic and mitochondrial DNA and can be used as a biomarker to characterize the mutational and epigenomic status in advanced solid tumors . The ctDAs the total cfDNA increases with the tumor growth, it was hypothesized that cfDNA derives directly from living tumor cells and that CTCs could be an alternative cfDNA source .In the ongoing ORIOLE trial , ctDNA cAlthough it appears a promising biomarker, recent reports have shed light on some inaccuracies of commercial laboratory cfDNA testing in patients with PCa . TherefoIt was speculated that a better understanding of the determinants of oligometastases could come from molecular studies on the signaling between the primary tumor and its metastatic sites. Exosomes are nanoscale extracellular vesicles that have a role in the exchange of genetic material, implicated in tumor cell growth and invasion, favoring disease dissemination by creating a pro-tumor micro-environment and the creation of premetastatic niches ,79,80,81By analyzing the exosome proteins derived from PCa cells, the researchers found a high level of molecules stimulating tumor cell migration and metastases, such as the b4 and avb6 integrins, vinculin and the Trop-2 transmembrane glycoprotein ,83. In aOn the basis of these findings, the role of exosomes in the early phases of tumor metastatization seems to make them interesting and worth to be explored biomarkers for future diagnostic approaches in the oligometastatic setting.Among emerging analytes to define disease biology, RNA-based biomarkers display several advantages over those relying on DNA. Firstly, the expression of RNA molecules is highly tissue- and disease-specific. Therefore, modifications in RNA expression directly reflect the changes within the cancer cells. Secondly, an RNA-based approach allows for an investigation of the families of the non-coding RNAs .miRNAs are short non-coding transcripts of 17–25 nucleotides, which participate in gene regulation at a post-transcriptional level. Since a single miRNA can target hundreds to thousands of mRNAs , it is omiRNA genes are transcribed by RNA polymerase II-III into long primary transcripts (pri-miRNAs), which are further cleaved into shorter pre-miRNAs. Pre-miRNA is then exported out of the nucleus, processed by enzyme DICER (RNase III endonuclease) into a mature miRNA duplex. To guarantee the interaction with 3′ UTR of their targets mRNAs, mature miRNAs must be loaded onto the Argonaute proteins (AGO), forming the central core of the RNA-induced silencing complex (RISC). Within the RISC complex, miRNAs induce silencing by both target destabilization and/or translational repression. Imperfect binding to the 3′ untranslated region of mRNAs leads to repression of protein translation, while in case of perfect or near-perfect complementarity, miRNAs induce the endonuclease cleavage and mRNAs degradation  Figure .Among non-coding RNAs, miRNA have shown great potential as cancer biomarkers since their first report in the context of malignant diseases . miRNA dDue to their high stability in biological fluids and the possibility to be detected from a small sample volume, miRNAs are emerging as valuable biomarker candidates for tumor detection. Cheng et al. , in a 20As miRNAs have several target mRNAs and one mRNA can be regulated by different miRNAs, deregulated miRNA-mRNA networks were found in cancer and can participate in various carcinogenesis-related pathways ,95,96,97Several studies have investigated the role of miRNAs in PCa carcinogenesis and their relationship with the clinical course of the disease as well as their potential role as biomarkers ,100,101 Different research groups were focused on the correlation between differential expression of specific miRNAs and PCa metastatic burden and aggressiveness, with the ultimate goal to provide potential valuable tools to refine risk stratification and to reduce overtreatment. Bryant et al. reported a significant over-expression of miR-375 and miR-141 in a metastatic cohort compared with a non-metastatic one .Bidarra et al. , in a reThe differential expression of miR-141 was correlated with PCa progression  in the sHudson et al.  performeA distinctive miRNA signature was found in correlation with epidermal growth factor receptor (EGFR) signaling, which controls PCa aggressiveness and progression. In particular, a reduced expression of miR-133, miR-875-5p and miR-146a was significantly related to elevated EGFR signaling and PCa progression ,109,110.In a recent work, Bhagirath and colleagues  demonstrSince 2011, when miRNA-200c was shown as responsible for the transition from oligo to polymetastatic phenotype  in a mouThe study by Lussier et al.  tested mIn contrast to these findings, a 2019 study by Dhondt et al.  reportedTherefore, more data are needed to identify and validate a strong miRNA signature for the discrimination between PMPC patients and true oligometastatic patients who could effectively benefit from an MDT.Despite promising, an accurate measure of miRNAs in biological fluids is very challenging. Technical and pre-analytical factors may have a major influence on miRNA detected levels, thus inducing biases in accurate quantification in biological samples. Therefore, a standard in the procedures for sample collection, handling and storage is of major importance ,117.As previously underlined, miRNA are small non-coding RNAs with a major role in gene expression regulation. It was estimated that about 60% of human genes are under the regulatory control of miRNAs , and emeEpigenetics is the study of chromatin modifications, which does not involve alterations in the DNA sequence, but modifications at the level of DNA-scaffold proteins named histones and/or directly involving DNA, such as methylation or alkylation, thus affecting genetic expression. miRNAs can regulate these epigenetic mechanisms at the post-transcriptional level. In particular, the emerging concept of epi-miRNA  refers tThe first identified epi-miRNA is the miR-29 family, which seemed to have a direct impact on DNA (cytosine-5)-methyltransferase 3 (DNMT-3) A and B in lung cancer . Few othThese results demonstrate that the integration between miRNA and epigenetic data, with the help of technologies such as ChIP-seq, could unveil novel interactions between miRNA and methylation mechanisms, laying the foundations for the identification of brand new biological linkages and novel prognostic markers .Further research is needed to evaluate novel biomarkers as promising tools to be implemented in the therapeutic workflow in the oligometastatic setting. Overall scientific evidence analyzed in this narrative review will be applied to the prospective phase II RADIOSA trial . In partAdditional molecular biology research is also needed in order to establish and define consistent isolation and quantification methods for specific biomarkers assessment. In this scenario, different ongoing trials for biomarker identification in PCa  Table 2Table 2 o


According to the Global Cancer Statistics 2020, colorectal cancer (CRC) represents the third most frequent malignancy worldwide, and is the second in terms of mortality .Its higher prevalence in geographic areas with a high human development index is connected with dietary habits such as a high consumption of red meat and alcohol, and with a sedentary lifestyle . Since tOngoing scientific research, by increasing the knowledge of the pathogenetic mechanisms and identifying novel prognostic and predictive biomarkers, might lead to a further progressive reduction in the incidence and mortality of CRC.A relevant concept, which emerged in recent years, is the key role of inflammation in in the tumorigenesis, progression, and metastasization of CRC . The indEscherichia coli, Streptococcus gallolyticus, Bacteroides fragilis, Fusobacterium nucleatum, and Enterococcus faecalis, among others, were found in the stools of patients with colorectal adenoma or carcinoma, but not in heathy subjects [Notably, assessment of the gut microbiota could represent a non-invasive diagnostic tool for the early identification of CRC . Indeed,subjects . The likely role of inflammation in the progression of CRC is also suggested by the prognostic significance of the blood count of neutrophils in patients with this neoplasia . Of noteThe notion that a percentage of CRCs are inflammation-induced has prompted the investigation of the tumorigenic role of some pro-inflammatory proteins, such as the membrane-bound metalloproteinase ADAM17, which induces the release of TNF-α and regulates IL-6 signaling .In spite of the development of novel therapeutic strategies for CRC, there are still several open questions. A dilemma is whether and which patients with non-metastatic CRC could benefit from adjuvant post-surgical therapies. Indeed, the treatment decision regarding patients with CRC is currently based on the pTNM stage, which is regarded as the main prognostic factor. However, a percentage of non-metastatic CRCs unexpectedly progress ; therefoIf confirmed in other studies, H-NLR may also represent a prognostic biomarker of a higher risk of progression in patients with non-metastatic CRC and may therefore be used for the identification of subjects who may benefit from adjuvant treatments . Liquid biopsy might also be a promising tool for the identification of CRC patients at a high risk of progression ,15. ThisIn the last two decades, the discovery of molecular therapeutic targets in CRC allowed the development of several targeted therapies based on the use of monoclonal antibodies . AlthougAnother mechanism of drug resistance may also be related to the therapy-induced selection of cancer stem cells, which represent tumor cells that are able to self-renew and to generate tumor cells harboring different genetic alterations . TherefoIn conclusion, although the knowledge of the mechanisms underlying the pathogenesis, progression, and metastasization of CRC has greatly expanded in recent decades, many aspects still remain to be clarified. This Special Issue represents a collection of original and review articles focused on recent advances in CRC, providing new insights for future research in this field.


Low molecular weight heparin, enoxaparin, has been one of most used drugs to fight the SARS-CoV-2 pandemic. Pharmacological properties of heparin recognize its specific ability, as with other oligosaccharides and glycosaminoglycan, to bind several types of viruses during their pass through the extracellular matrix of the respiratory tract, as well as its anticoagulant activity to prevent venous thromboembolism. Antithrombotic actions of enoxaparin have been testified both for inpatients with COVID-19 in regular ward and for inpatients in Intensive Care Units (ICUs). Prophylactic doses seem to be able to prevent venous thromboembolism (VTE) in inpatients in the regular ward, while intermediate or therapeutic doses have been frequently adopted for inpatients with COVID-19 in ICU. On the other hand, although we reported several useful actions of heparin for inpatients with COVID-19, an increased rate of bleeding has been recorded, and it may be related to several conditions such as underlying diseases with increased risks of bleeding, increased doses or prolonged administration of heparin, personal trend to bleed, and so on. Heparin and heparan sulphate are complex, linear, acidic polysaccharides belonging to the glycosaminoglycan (GAG) family; their structure makes continuous alternating glucosamine and uronic acid units; for these reasons, they are considered polyanions . The conThe anticoagulant activity of heparin is due to its property to bind an anti-protease of the serpin family named antithrombin III (ATIII) ; this biFrom a pharmacological point of view, we distinguish two different types of heparins: unfractionated heparins (UFH) and low molecular weight heparins (LMWH) . UFH is On the other hand, heparan sulphate, the main component at cell surfaces and in the extracellular matrix of most animal tissues, can interact with a large variety of protein and cells, so takes a relevant role in disease processes. Most functions of heparan sulphate depend on ionic interactions, with a variety of proteins, including growth factors, cytokines, and their receptors . FurtherCoronaviruses (CoVs) are single-stranded RNA viruses which originate from a well-known family of viruses named Coronaviridae . UsuallySince the first epidemiological report from different cohorts of patients affected by COVID-19 in China, this infection has been associated to hypercoagulable state and thrombotic complications ,17. For Yet, before exerting its specific actions, SARS-CoV-2 binds several types of glycosaminoglycans and oligosaccharides, such as fucosylated acid, sialic acid and heparan sulphate .Heparan sulphate is abundant in the respiratory tract, and it plays a role as binding factor for coronaviruses with tropism to bronchitis and other respiratory infections . For thiAs previously reported, COVID-19 predisposes patients to venous thromboembolism (VTE), due to excessive inflammation, platelet activation, and endothelial dysfunction. The association between COVID-19 and VTE is well known since first reports from China, and this association took clinical relevance, because the association between these two conditions was associated to a worse prognosis in Chinese population .Yet, thrombotic risk seems to be different in patients with different intensity of care : patientFor this reason, pharmacological prophylaxis to prevent VTE has been suggested since the beginning of pandemic, to escape thrombotic complications for inpatients .Prophylactic doses of low molecular weight heparin have been reported as safe regarding the prevention of VTE in inpatients in regular ward . FurtherYet, the duration of thromboprophylaxis with standard doses of low molecular weight heparin after discharge is still matter of discussion; in particular, the administration of LMWH is considered to be safe, since the first signs and symptoms of the disease and during the hospitalization, while the long term prophylaxis also after hospital discharge did not report univocal consensus for the relevant outcomes , as far as for the duration of treatment. The high risk of developing VTE in patients with SARS-CoV-2 has raised hypotheses about the use of intermediate and therapeutic doses of LMWH, which have not yet developed events and therefore in primary prevention.As shown in literature by clinical trials as ATTACC , REMAP-CIn the HEP-COVID trial , in patiThe case for ICU patients is different, in which the treatment with therapeutic doses with LMWH appeared not superior to the usual-care doses, for primary prevention of the onset of VTE . In addiTo date, no doubts should be raised about the use of anticoagulant therapy in patients with COVID-19, having guaranteed a good safety profile in prophylactic and therapeutic doses.According to the literature , reducedThe depolymerization of heparin results not only in the development of LMWHs but also in the synthesis of fondaparinux, that is composed only of the pentasaccharidic sequence of heparin that is able to bind antithrombin III with a specific propensity to selective inhibition of Xa more than IIa ; from a The clinical utility of fondaparinux in VTE preventions has been reported in several clinical contexts as major orthopaedic surgery and acute medical illness ,39.So, as COVID-19 is an acute infection that required hospitalization in (majority) most of the cases of prolonged hospitalization, an adequate thromboprophylaxis with fondaparinux has been suggested and performed in several studies ,41. A reBecause these cohorts of patients were no larger, the benefit of the clinical utility of Fondaparinux 2.5 mg as thromboprophylaxis for inpatients with COVID-19 was postponed in all reported studies to other scientific research on a large population. The risk of bleeding should always be considered when an antithrombotic drug is administered to a patient, both if prophylactic or therapeutic doses are considered . SeveralAlthough the risk of VTE has been confirmed also by several scientific societies, the use of therapeutic doses to prevent VTE has been frequently discouraged by experts .In a multicenter study from the USA, in fact, for the first time, it has been reported that the rate of bleeding for inpatients with COVID-19 was really similar to the rate of VTE, so therapeutic doses were not suggested by Authors and a clinical input to a right surveillance of bleedings was suggested in their conclusion . RegardiIn another large series from the RIETE registry, the incidence of bleeding increased nearly 5.0%, and a great part of patients received thromboprophylaxis with intermediate or therapeutic doses of LMWH .These data testify that clinically, the risk of bleeding should be always considered, although prothrombotic diseases such as COVID-19 show an increased risk of fatal pulmonary embolism.Since WHO suggested the use of heparins during the pandemic of SARS-CoV-2, a large series of studies regarding protective action of low molecular weight heparin in inpatients has been reported. Standard doses, intermediated doses and therapeutic doses of low molecular weight heparin have been tested in several cohorts around the world, with positive outcomes regarding VTE.Yet, heparins may also exert their pharmacological activity in other ways. Besides its action toward serinproteases of clotting system as factor IIa and/or Xa by its pentasaccharide motif, heparin may exert its anti-inflammatory action toward other proteases nexin I, as far as human neutrophil elastases and others by its arginine residues, and mainly OSO3- groups . For theIn about 15% of COVID-19 patients, the clinical course of the disease may be complicated by the onset of severe interstitial pneumonia, with possible lung failure that may require hospitalization; however, many infected patients remain asymptomatic or paucisymptomatic, and are managed in outpatient settings ,56.Following the clinical indication of WHO , ItalianFurthermore, a following study on patients treated at home for COVID-19 revealed that LMWH was preferred by several experts for patients with associated cardiovascular comorbidities, with low rates of pulmonary complications, or need of hospitalization for lung failure .Moreover, a further study from another Italian group, that treated patients with COVID-19 at home with high flow nasal cannulae, revealed that thromboprophylaxis with standard doses of LMWH are suggested, in any case, to escape vascular complication as pulmonary embolism at home. The two-way link between the inflammation and clotting system is well established and based on several mechanisms, as reduction of the activity of natural anticoagulants as far as inhibition of fibrinolysis, and the pro-inflammatory and pro-coagulant action of cytokines by increasing expression of tissue factor on monocytes and endothelium is established, thus giving a hyperactivation of the clotting cascade ,60. The Together to its well know anti-thrombotic role, that is needed to reduce the rate of thrombotic complications, heparin showed further useful actions in vitro and in vivo.Anti-inflammatory effects have been reported in several series and in experimental model with the reduction of cytokines , and a sSo, the use of heparin is suggested, since the first clinical signs of confirmed infection by SARS-CoV-2, although the majority of positive effects have been demonstrated for inpatients vs. patients treated at home; furthermore, heparin use is suggested also after discharge from hospital as for other acute medical illnesses. Yet, overdose of heparin with intermediated or therapeutic doses in patients with COVID-19 are also associated to similar rates of thrombotic and hemorrhagic complications that may be associated with worse outcomes.


The vertebrate head is characterized by a complex craniofacial skeleton and paired sensory organs. These structures are derived from two adjacent embryonic cell populations, the neural crest and cranial placodes. The neural crest contributes to the craniofacial skeleton and a subset of cranial ganglia, while cranial placodes form the anterior pituitary, optic lens, inner ear, olfactory epithelium and several cranial ganglia. Defects in cranial neural crest and placode development can cause a wide array of human congenital malformations ranging from craniofacial disorders to hormone imbalance and sensory deficits. Throughout head development, reciprocal interactions between neural crest and placode cells are essential to drive the coordinated morphogenesis of multiple craniofacial structures. For this Research Topic, we have collected 14 research articles and reviews, analyzing and discussing at the cellular, molecular and genetic levels the role of the neural crest and cranial placodes in craniofacial development, and the importance of their interactions to organize the orofacial complex.York et al. discusses the origin of, and associations between, neural crest and placode cells in the jawed vertebrate head. Here, the authors delineate the gene regulatory networks (GRNs) that control neural crest and placode cell development and highlight how the coordinated movement and coalescence of neural crest and placode cells during embryogenesis is essential to yield functional sensory structures such as the cranial ganglia. These findings are reviewed in the context of jawed and jawless vertebrates, the latter relying on seminal results obtained from lamprey and hagfish. Importantly, recent studies demonstrate both evolutionary conservation and differences between jawed and jawless vertebrates with respect to the assembly of the cranial ganglia from neural crest and placode cells, generating a testable model for how these critical cell types appeared and worked in concert in ancestral vertebrates to pattern the craniofacial apparatus.Neural crest and placode cells are truly evolutionary marvels. Together, they build much of the peripheral nervous system and sense organs that reside in the vertebrate head. Notably, the intricate interactions that occur between these two cell types endow vertebrates with features that distinguish them from their invertebrate ancestors. Indeed, comparative studies between jawless and jawed vertebrates have revealed molecular signatures of neural crest and placode cells, shedding light on the gene products and developmental signaling pathways that are involved in mediating neural crest-placode cell interactions in these distinct vertebrate lineages. Thawani and Groves and Seal and Monsoro-Burq describe the major signaling molecules and transcription factors controlling the inductive and patterning events that elicit the development of these lineages at the neural plate border. Despite a growing understanding of the early GRN that controls the formation of the neural plate border during early embryonic stages, both reviews highlight important gaps in knowledge that will need to be resolved to understand how these two cell populations are established given their close proximity and similar developmental timeframe. The authors also consider outstanding questions in the field and how recent advances in transcriptomic analyses may help address these unresolved issues.At the end of gastrulation, neural crest and cranial placodes arise from a narrow domain of the embryonic ectoderm immediately adjacent to the prospective neural plate, the neural plate border. In a pair of reviews, Thawani and Groves and Seal and Monsoro-Burq, the neural plate border is defined by a unique signature of transcription factors among which Sox proteins are key players. Mutations in genes encoding SOX proteins have been linked to pathologies, often affecting multiple organ systems including the orofacial complex. Schock and LaBonne summarize the major classes of Sox factors and their role in the regulation of various aspects of neural crest development, including specification, multipotency retention, migration and differentiation. They highlight the importance of a subset of these genes in directing the development of neural crest- derived craniofacial structures through their unique ability to regulate craniofacial bone and cartilage formation, and drive palatogenesis, odontogenesis and salivary gland development. Finally they describe the clinical and molecular features of several SOXopathies, a group of rare multisystem developmental disorders. The prevalence of craniofacial defects in SOXopathies underscores the critical roles these factors have in the development and evolution of the vertebrate craniofacial complex.As discussed by Chong-Morrison and Sauka-Spengler discuss recent advances in the characterization of the cranial neural crest GRN through state-of-the-art multi-omics approaches. They summarize how parallel considerations of transcriptome, interactome, and epigenome data sets have substantially refined the roles of the key players identified during the pre-omics era. They also discuss key questions that can now be addressed through a multi-omics approach and the development of new, unbiased functional genomics integration tools.In the last decade, modules of the neural crest GRN have been characterized in multiple organisms. This information has significantly improved our understanding of the mechanisms underlying the complex developmental trajectory of the neural crest. In their review, Barriga and Theveneau, neural crest cells employ a variety of different mechanisms, or “mixotaxis,” to ensure successful migration. Using Xenopus cranial neural crest cells as an example, the authors discuss different strategies that may be used by neural crest cells to accomplish migration. These include chemotaxis, in which cells respond to a gradient of soluble guidance factors, or haptotaxis, in which the cue is a bound signal; durotaxis, whereby cells move from softer to stiffer substrates; ratchetaxis, in which migratory cells are confined to a local route due to the presence of physical and/or chemical barriers; and galvanotaxis, whereby electric fields can influence cell migration. It is important to note that, with the preceding types of migratory mechanisms, it is often challenging to obtain in vivo data to support their existence due to the complex nature of the environmental milieu in the embryo, which directly impacts the migratory capacity of neural crest cells.Neural crest cell migration is a process essential for the correct anatomical positioning of neural crest derivatives within the developing embryo. As highlighted in Manohar et al. and Mo et al. tackle the former in the neural crest, identifying roles for Cadherin-11 and Platelet-Derived Growth Factor Receptors (PDGFRa and PDGRFb), respectively. While Cadherin-11 function in Xenopus neural crest cells (migration) and cancer cells  has been well-documented, studies by Manohar et al. in the chick embryo reveal that Cadherin-11 acts during neural crest cell specification. Cadherin-11 is first expressed in the neural plate, and is maintained throughout the formed neural tube and later observed in migratory neural crest cells. Knockdown of Cadherin-11 reduces the number of premigratory cranial neural crest cells and negatively impacts neural crest cell survival, in part, through activation of p53-mediated apoptosis. Ultimately this influences neural crest cell migration, as fewer neural crest cells are available to migrate, and those that do migrate do so poorly due to the absence of filopodia and lamellipodia. Collectively, these data point to multiple functions for Cadherin-11 in the forming neural crest.The molecules that mediate the formation, migration and differentiation of neural crest and placode cells have been the subject of investigation by many groups. In this Research Topic, Mo et al. investigated the role of receptor tyrosine kinase signaling in murine craniofacial development by ablating both PDGFRa and PDGFRb from the cranial neural crest. Through these studies, a genetic interaction could be identified between the two receptors and, notably, the presence of additional conditional alleles exacerbated phenotypes exhibited by the mutants. These phenotypes included increased distance between the nasal pits, facial hemorrhaging, misshapen fore- and/or midbrain, facial blebbing, and facial clefting. Further experiments revealed that PDGRa regulates the size and shape of the cranial neural crest cell migratory stream, with PDGFRb only contributing minimally. Both receptors, however, augment neural crest cell proliferation earlier in development, while during mid-gestation, PDGFRb signaling predominates with respect to controlling the proliferation of the craniofacial neural crest-derived mesenchyme. Interestingly, neither receptor functions during mid-gestation to control the survival of the cranial neural crest-derived mesenchyme. Taken together, these data reveal the roles of each PDGFR in the cranial neural crest and, subsequently, craniofacial development.Hutchins et al. sought to identify novel downstream targets of canonical Wnt signaling. To this end, they performed RNA-seq on sorted chick cranial neural crest cells overexpressing Draxin, a potent Wnt antagonist, which also interferes with the cranial neural crest epithelial-mesenchymal transition (EMT). The authors identified and validated a novel Wnt-responsive gene, RHOB, a member of the Rho GTP-binding protein family. Because RHOB is a known BMP-responsive gene in the trunk neural crest, by electroporation of a BMP reporter construct they confirmed the lack of active BMP signaling in cranial neural crest post-EMT, and demonstrated RHOB activation by expression of a stabilized form of b-catenin. These results highlight the importance of crosstalk between signaling pathways and axial level-specific interactions in the regulation of cranial neural crest development and craniofacial morphogenesis.Canonical Wnt signaling is especially critical for neural plate border formation and craniofacial morphogenesis, and dysregulation of Wnt signaling has been linked to several craniofacial syndromes. To gain insights into these pathologies, Dash et al. identified a mutant they named snouty that exhibits abnormalities of the facial prominences, cranial nerves and vasculature. Surprisingly, rather than affecting a gene involved specifically in craniofacial development, snouty codes for Med23, a subunit of the Mediator complex of proteins required for the transcriptional control of genes in all tissues. The allele isolated in the study represents a partial loss of Med23 function that can be rescued, in part, by attenuating Wnt signaling. The results highlight the importance of undertaking forward genetic screens, even in systems such as the mouse. Furthermore, they reinforce the idea that so called housekeeping factors can have very specific developmental roles depending on the context.The complexity of the vertebrate head, containing as it does a wide variety of distinct neural crest and placodal derivatives, pleads for the importance of a multitude of specific molecular mechanisms in its development. In a genetic screen for regulators of craniofacial development, Hox genes based on their origin in the hindbrain. As they populate the pharyngeal arches (PA), neural crest cells respond to signals from the pharyngeal surface ectoderm and endoderm, which will determine their fate. Zhang et al. investigate the role of nested expression domains of Hox genes in the pharyngeal epithelium in the control of PA morphogenesis and differentiation. Transgenic mouse embryos with ectopic expression of Hoxb3 in the ectoderm pharyngeal epithelium of PA2 have multiple cranial nerve and skeletal defects. This phenotype correlates with a regionalized up-regulation of Jag1 expression, a Notch ligand, in the ectoderm epithelium of PA2. The authors demonstrate through in vivo chromatin immunoprecipitation and in vitro luciferase reporter assays that Hoxb3 can directly bind to a cis-acting regulatory region at the Jag1 locus to transactivate its expression. The work highlights the importance of pharyngeal epithelial and cranial neural crest cell interactions and the interplay between Hox genes and signaling molecules to promote PA and craniofacial development.Cranial neural crest cells express specific combinations of LaMantia posits that neural crest cells act as “inductive ambassadors” to promote the differentiation of craniofacial tissue and to serve as an initial conduit between the former and the brain. Neural crest-derived mesenchymal cells participate in interactions with epithelia and also directly supply signals to orchestrate tissue morphogenesis and differentiation. Using examples from normal embryogenesis  and various diseases possessing physical anomalies, cardiovascular defects and behavioral deficits , data is put forth supporting the notion that the inductive cues provided by neural crest cells, along with neural crest-derived mesenchymal/epithelial interactions, are vital in driving tissue morphogenesis at sites outside of the face, such as the limbs and heart, and in forming proper neural circuits. Importantly, these studies have revealed signaling pathways and causative genes, the latter of which are expressed both in the brain and at sites of neural crest-derived mesenchymal/epithelial interactions in the developing embryo. Collectively, this review further underscores the intricate relationship and inherent cross-talk between the brain/neural tube, which initially possesses neural crest cells, and the face and other structures to which neural crest cells give rise.With the appearance of neural crest cells and placode cells in vertebrates, complex structures could be formed, such as the craniofacial skeleton, peripheral nerves, and paired sense organs. In his recent review, Taroc et al. document Isl1 expression, characterize the Isl1 lineage, and evaluate the phenotypes of GnRH neurons lacking Isl1. Isl1 is expressed in proliferating epithelial precursors that will give rise to neurons and later is noted in almost 90% of GnRH1-positive neurons in the olfactory pit. Lineage tracing of Isl1-expressing cells through the use of a tamoxifen inducible or constitutive Cre line results in the labeling of many different cell types. Finally, conditional knockout of Isl1 in GnRH1 neurons revealed that Isl1 is not required for the migration of GnRH1 neurons nor expression of GnRH itself. In summary, these results raise the question as to the role of Isl1 in GnRH neuron development and point to the need for additional postnatal studies to shed light on Isl1 function.The olfactory placodes form several cell types within the olfactory system such as gonadotropin releasing hormone-1 (GnRH-1) neurons, the first neuronal population present in the developing olfactory pit. However, the olfactory pit houses multiple neurons, including those expressing the transcription factor Islet1 (Isl1). To determine the role of Isl1 in GnRH development in the mouse, Cheung et al. present the characterization of a rare cell type in the olfactory epithelium of the zebrafish. Olfactory rod cells display a prominent actin-rich projection at their apical surface. While not previously described in zebrafish, these cells have already been reported in other teleost but whether they represent artifacts of fixation has until now remained a possibility. In the present study, live imaging was used to verify the presence of an actin-rich rod unequivocally. Although the function of these rare cells remains a mystery, possibilities range from odor-sensing to a role in immunity, in a manner similar to brush or tuft cells described in mammals. Future studies will be needed to address these possibilities, and to determine the developmental origin of this intriguing cell type.Finally, As illustrated by these contributions, cranial placode and neural crest cells are engaged in reciprocal interactions throughout their developmental history that influence their fate, behavior and ultimate differentiation. While much has been learned in the past decade on the importance of these interactions during vertebrate head development, it remains a burgeoning field. With the introduction of multi-omic and single cell analyses, the next decade is expected to bring a wealth of new information on the development of these two cell types. One important challenge moving forward is to further refine the hierarchy of signaling molecules and downstream transcriptional regulators that form the basis of the placode and neural crest GRNs in order to understand how these adjacent cell populations are independently established at the neural plate border. It is especially critical to validate functionally the direct vs. indirect regulations among these factors. Another unresolved question relates to the molecular bases of placode and neural crest multipotency, a topic that is still under active debate. Through deployment of a wide array of signaling cues, placode and neural crest cells cross-regulate their respective migration and differentiation, but how these cells integrate inputs from multiple sources, both spatially and temporally, to build the craniofacial complex remains obscure and is essential to investigate. These are just a handful of questions and challenges that the craniofacial biology community will likely face in the upcoming years. We are extremely grateful to all the authors and reviewers who made this collection possible. We hope these articles will stimulate further interest and inspire young scientists to tackle some of these and other outstanding questions in the field.All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Various nutrients can change cell structure, cellular metabolism, and cell function which is particularly important for cells of the immune system as nutrient availability is associated with the activation and function of diverse immune subsets. The most important nutrients for immune cell function and fate appear to be glucose, amino acids, fatty acids, and vitamin D. This perspective will describe recently published information describing the mechanism of action of prominent nutritional intervention agents where evidence exists as to their action and potency. The immune system protects the host against infection from pathological microorganisms and provides constant surveillance for malignant cells that arise over a lifetime. The immune system is able to develop appropriate tolerance to self-proteins, circulating macromolecules, self-cells, and tissues, and to harmless environmental molecules .Individual heterogeneity regarding the intensity of immunological responses exists, largely dependent on genetics, environment, lifestyle, nutrition, and the interaction of these factors. Nutritional immunology is a field of immunology that describes the influence of nutrition on the immune system, antiviral activity, and associated protective functions . DeficieThis perspective will describe recently published reports describing the mechanism of action of prominent nutritional intervention agents where evidence exists as to their action and potency . This perspective has concentrated on describing the molecular and/or metabolic basis of their immunological effect.Glutamine is the most abundant amino acid in the blood and in the free amino acid pool in various tissues . The con2, aspartate, alanine, and lactate in a process called glutaminolysis , whereas glutamine is converted into glutamate, aspartate, and alanine by undergoing partial oxidation in the TCA cycle to CO in ref. –7. Thus, in ref. .Different populations of macrophages have now been identified, including M1 and M2 macrophages –11. M1-lGlutamine metabolism and supply of metabolic intermediates have been proposed to be essential to the antiviral activity of the immune system, although many of the mechanisms are as yet unknown .l-arginine is 0.077 mM, approximately tenfold less than glutamine. Arginine is particularly important in the liver, where it is an intermediate in the urea cycle, thus is an intermediate in amino acid catabolism. Arginine is also very important in a number of immune cells, as a substrate for nitric oxide synthase (NOS), thus is a substrate for the production of nitric oxide, a potent immunoregulatory mediator that is cytotoxic to tumor cells and many microorganisms. Macrophages can produce relatively large amounts of nitric oxide, especially the M1 inflammatory macrophage, via increased concentrations of the enzyme inducible NOS (iNOS). The activated macrophage can actually release the enzyme arginase to deplete local concentrations of arginine (indeed arginine is required for tumor growth). It has been reported that mouse peritoneal resident and Bacillus Calmette–Guerin (BCG)-activated macrophages and human monocytes are capable of utilizing glutamine at high rates, contain sufficient activity of the enzymes required to convert glutamine to citrulline  to account for observed rates of nitrite synthesis (derived from NO) in the absence of extracellular l-arginine, and will release nitrite when exposed to intermediates of the proposed glutamine --> arginine pathway [l-arg and indeed may play a role in the suppression of the antitumor response [The plasma concentration of  pathway . Thus thresponse .Fatty acids (FAs) play several essential roles in the homeostasis and structure of the cell and various tissues and organs. FAs are the main components of all biological membranes and are built into sphingolipids, phospholipids, glycolipids, and lipoproteins. They are also the major source of energy stored in the triacylglycerols. In addition, various metabolites of FAs serve as essential intracellular and extracellular lipid mediators and hormones. Therefore, FAs have many possibilities to modulate immune cell function by influencing their structure, metabolism, and function, acting through surface proteins , nuclear receptors, or membrane transporters . Much haVesicular stomatitis virus [Many viruses, including coronaviruses, are enveloped viruses with a nucleocapsid mainly made of phosphorylated nucleocapsid protein embedded inside a phospholipid bilayer envelope. This envelope plays an important role in virus assembly and release from the host cell, and it is critical for viral pathogenesis. The viral surface consists of the spike protein of the virus, which is essential for the attachment to the host cell receptor and for initiating infection. Given the indispensable nature of lipids in multiple stages of viral replication, lipid synthesis and metabolism in host cells have been recognized as essential for the assembly of coronaviruses. Bioactive lipids with antiviral properties include certain long-chain monounsaturated fatty acids (MUFAs) and medium-chain fatty acids (MCFAs), specifically lauric acid (LA), the primary fatty acid of coconut oil. It is a saturated MCFA with potent antimicrobial properties . Long-chis virus .The active form of vitamin D  is usually abbreviated as vitamin D. Vitamin D receptors have been identified in most immune cells . MacrophA recent study reported for the first time the potential influence of vitamin D status on bioenergetics and metabolism in freshly isolated peripheral blood mononuclear cells. The data indicated a close relationship between Vitamin D levels and immune cell bioenergetic responses. Low vitamin D levels were clearly associated with a pattern consistent with increased oxidative metabolism and inflammatory activation that was reflected in altered bioenergetics of PBMCs .Studies on the effects of nutrient combinations, whole foods, and diets on human immune cell metabolism and function, in vivo and ex vivoNutritional supplementation and potential prevention or slowing of immunosenescence by altering immune cell metabolism and functionInvestigation of the role of obesity in altering immune cell metabolism and function in humans, including antiviral activityThe role of the gut microbiota in shaping host immune maturation, metabolism, and functional responses in animals and humans including antiviral activityDetermination of the role of glutamine metabolism and supply of glutamine derived metabolic intermediates in the essential antiviral activity of the immune system (adapted from ref. ).


Magnetorheological (MR) materials are classified as smart materials that can alter their rheological features once exposed to peripheral magnetic fields. MR materials have been a standard and one of the primary smart materials for the last few decades due to their outstanding vibration control performance in adaptive sandwich structures and systems. This paper reviews the vibration suppression investigations of flexible constructions using MR elastomers (MREs). In relations of field-dependent controllability, physical features such as stiffness and the damping of different geometrical structures integrated with the core layer of MREs are explored. The veracity of the knowledge is discussed in this article, whereby sandwich structures with different MR treatment configurations are analyzed for free and forced vibration, MRE sandwich structures are analyzed for stability under different working conditions, and the optimal positions of fully and partially treated MRE sandwich structures for improved vibration control are identified. MR materials′ field-dependent stiffness and damping characteristics are also discussed in this article. A few of the most noteworthy research articles over the last several years have been summarized. Sandwich structures are frequently employed in the design and fabrication of lightweight structural systems due to their ability to provide superior structural and thermal performance while requiring less material ,2. Such Magneto-rheological (MR) materials are smart materials whose rheological characteristics can be controlled by applying magnetic field externally . MR mateMRE is a kind of rubber-like solid material with a rubber or elastomer matrix and is also recognized as a magneto-sensitive elastomer. There are polarized magnetic particles, a natural or synthetic rubber matrix, and additives such as silicon oil . A non-mThere are many analogical mechanical behaviors, but MRE materials have one unique mechanical behavior: they have a field-dependent modulus in the pre-yield region, unlike MRF and MR foam, which have an MR effect in the post-yield region, which makes MREs more stable and extensively applicable in the semi-active control of flexible structures. According to research , the maxPrevious studies have looked at the applications of MREs in ATVAs ,19,20,21An elastic plastic material model can be used to explain the rheological properties of MRE material. There have been numerous models devised to determine the moduli of storage and loss of MRE in relation to induced field and frequency. It is worthwhile to note that no complete model of these smart materials′ pre-yield behavior has been created. Due to the complex constitutive relationship, different models should be utilized to explain the rheological characteristics of MR materials. The most generally used models to evaluate the rheological characteristics of the smart elastomer in the pre-yield area are viscoelastic models. The dynamic constitutive equation of viscoelastic materials has a noteworthy impact on the dynamic analysis of elastic–viscoelastic complex structures. Some typical viscoelastic models are thoroughly described.Suppose the viscoelastic material is linear, isothermal, homogeneous, and isotropic, and it can be expressed in the form of a Boltzmann solid integral . that isFor non-aging viscoelastic materials, the Equation (1) can be simplified as:H(t) is unit step function.Fourier transformation is applied to Equation (2), and the result is:Sign plus “^” indicates the Fourier transform of corresponding variable, and Under the action of harmonic external force, the strain of the viscoelastic material lags behind the stress, and the stress–strain curve is a hysteretic loop. Suppose ectively .(6)G′ = d on MRF , which iThe standard rheological model is more accurate and has been widely used in structural dynamic analysis and other aspects . There aGiven MRE′s viscoelastic behavior, all models illustrating the vibration features of viscoelastic sandwich structures are possibly relevant to MRE adaptable structures in the pre-yield zone. Ross et al.  develope modulus . The resf is Young′s modulus of respective surface/face layer, f is the moment of inertia at the elastic layer′s centroid. Additionally, b is the beam width, and h2 is the core layer thickness. Nayak investigated the dynamic characteristics of the MRE sandwich beam and developed the equation of vibration characteristics by using the extended Hamilton energy method. At the same time, the influences of parameters such as the magnetic field strength, the ratio of the ferromagnetic material, the length of the sandwich beam, and the center layer thickness of the magneto rheological elastomer on the natural frequency of the system were analyzed [However, the calculation amount of the RKU model is too large, restricting its application. So, in practical application, the finite element method (FEM) is the most extensively stated method in dynamic investigation of MRE sandwich structures. The finite element method is a more accurate approximation method, which can transform a continuous unlimited freedom problem into a discrete finite degree of freedom problem. There are too many analyses and experiments that show that the finite element method is an effective method which cannot be replaced. Jacques introduced a numerical analysis of the nonlinear vibration characteristics of a viscoelastic sandwich beam by using FEM . Anotherted. Sun  developeanalyzed . Aguib eanalyzed . The RitThe theoretical analysis methods of the calculation and modeling of the characteristics of the MRE and the dynamic characteristics of the sandwich structure are mostly carried out by the simplified object. However, it is necessary to conduct the experiment to verify the theoretical results. In the experimental study of the vibration characteristics of the MRE, the fabrication of the MRE is very important. The fabrication of MRE first appeared in 1995 in Shiga, from the Research and Development Laboratory of Japan′s TOYOTA center, which fabricated the prototype of MRE, a kind of magnetic gel mixed with silicone rubber and iron powder. In the fabrication process, typically the natural rubber and synthetic rubber as the elastic matrix, silicone rubber is the most common matrix. Jolly developed MRE based on silicone rubber, and the results show that the shear modulus of MRE in an applied magnetic field increases about 40% more than the original . BecauseIn most of the experimental studies, the elastic surface layer of the MRE sandwich beam is made of aluminum alloy material, because the aluminum alloy has lower damping properties and higher stiffness compared with MRE. Moreover, the relative permeability of aluminum alloy is almost 1, so the size and distribution of the applied magnetic field on the MRE will not be disturbed. Free vibration, impact test, and forced excitation are the main experiments that have been conducted in studies. Experimental methods include the experimental modal analysis technique, in which the main principle is using the real or mechanical structure model and the product as the object to execute dynamic experiments, data acquisition, signal analysis and processing, frequency response function estimation of response signal of test points of the exciting force and structure, and then dynamic modal parameter identification (curve fitting), which can achieve quite a high accuracy of modal frequencies, modal shapes and modal damping. The typical experimental setup is shown in The theoretical analysis and experimental studies of MRE are mainly focused on the effects of various parameters on the dynamic responses of the MRE sandwich beam. Most of the research studied the effect of an applied magnetic field on the frequency response, loss and storage moduli of the structure. However, some studies have reported the effect of the geometry, partial treatment of MRE, and nonlinear behavior of MRE on the dynamic characteristics of sandwich beams consisting of an MRE core layer. The magnetic/electric field increases as the natural frequencies of the structures increase. This effect, which has been seen in numerous investigations, is caused by an increase in the MRE′s complex shear modulus as the applied field is increased. Several investigations, however, found that when the applied magnetic field rose, the natural frequencies of MR-based sandwich beam structures decreased.A hybrid magnetic system and a self-sensing laminated MRE structure were used to build and test a self-sensing MRE vibration absorber in a study by Sun et al. . The finAccording to Deng et al. , a magneSun et al.  created Ke-Xiang et al.  investigHu et al.  studied Nayak et al.  investigKozlowska et al.  used an In terms of loss factor, the damping properties of adaptable sandwich structures have received a lot of attention. The ratio of imaginary-to-real components of complex eigenvalues is defined as the loss factor. The viscoelastic behavior of MRE composed of RTV silicone rubber and carbonyl iron powder (CIP) was studied by Bellan and Bossis . The appThe higher-order sandwich beam theory was used by Choi et al.  to analyWang et al.  examinedIn comparison to MRE beam structures, few studies on sandwich shells and plates with an MRE core layer have been reported. Yeh  used theAfter investigating the MRE sandwich plate under forced vibration, Aguib et al.  used comFewer studies are available on the application of the damping effect of an MRE; for example, Ulicny and Golden and Ottaviani et al. ,106 suggApart from the applied magnetic field, additional parameters, such as the material and layer thickness of the face layers, the layer thickness of the core layer, boundary conditions, external disturbances, modes of vibration, and temperature, may have an impact on the natural frequencies, loss factors, and vibration amplitude of the MRE-based sandwich structures. Some of the related studies are mentioned below.Mikhasev et al.  investigThe free vibrations of a rotating MR doubly tapered sandwich beam were investigated by Navazzi et al. , who preVemuluri and Rajamohan  used theNanoparticles are currently gaining popularity among researchers due to their high rigidity, low density aspect ratio, and damping characteristics. MR materials can benefit from the addition of nanoparticles or fillers, which boost their magnetic resonance effects, sedimentation stability, stiffness, and damping. Some scientists studied the magnetic resonance impacts of nanoparticles augmented with MR materials to see how they behaved. However, adjusting the quantity and size of nanoparticles in MR materials yielded the greatest effects. Nanoparticles have recently been shown to improve the mechanical and dynamic behavior of MR materials, according to new study. Chena et al.  examinedThe vibration responses for MRE sandwich beam composed of composite face sheets reinforced with functionally graded carbon nano tubes (CNT) were numerically analyzed by Fadaee and Talebitooti  using DQThe rheological characteristics of anisotropic MREs mixed with three types of carbon black  were investigated by Lu et al. . The resTo compare the viscoelastic characteristics of MRE with and without MWCNT reinforcement, Selvaraj and Ramamoorthy  utilizedNonlinear behaviors in MRE sandwich structures have been observed, despite the fact that previous research indicated that MRE sandwich structures had a core operating in the pre-yield zone. The first-order natural frequency of a geometrically flawed MRE sandwich rose in response to an increasing external magnetic field . Aguib oA study of the literature shows that the stiffness and damping characteristics of sandwich structures fully treated with the MRE layer increase significantly as the applied field rises. For their part, the MRE-layered sandwich structures are heavier due to their elastomer′s high weight density. Applying the same magnetic field throughout a whole structure is also a difficulty. In order to obtain extreme controllability with a relatively slight treatment area and minimal energy consumption, partial MRE treatments are highly desired, especially when administered in the most optimum places. MRE partial segments are used in the core layer of sandwich structures that have been partially treated.Regarding the characteristics of partly treated MRE sandwich constructions, different elastomer and structural factors, such as core layer thickness and complex shear modulus, have a significant impact. Furthermore, partial treatments, both in number and position, have a major impact on structural dynamics. No matter what the design, the end circumstances, or the modes of vibration are, partial treatments result in lower natural frequencies of the sandwich structure than untreated ones. Since the fully treated structure has a larger mass, this is a result of that. It is generally accepted that raising the applied field increases natural frequencies.According to popular belief, the loss factors of fully treated sandwich structures are generally higher than those of partially treated sandwich structures. This is due to the latter structure′s lower dissipated energy. However, under certain boundary conditions and geometries, some studies found that partially treated sandwich structures had a higher loss factor than fully treated sandwich structures.The benefit of partially treated sandwich structures over fully treated sandwich structures is that they can achieve a suitable layout with minimal treatments while providing nearly the same concert as fully treated sandwich structures. The design of a partially treated MRE sandwich structure necessitates determining a suitable treatment formation that yields the structure′s extreme controllability and vibration clampdown capability in terms of stiffness and damping. Several optimization problems in MRE sandwich structures have been developed for this purpose.Some numerical studies have been conducted to investigate the vibration characteristics of partially treated MRE sandwich structures. Zhou and Wang  investigFree vibration characteristics of a sandwich beam with conductive face sheets and a viscoelastic and MRE core were studied by Nayak et al. . When coThis review discusses the impact of several parameters on the dynamic responses of MRE-cored sandwich constructions, including the applied field, shape, material of the elastic layer, boundary conditions, excitation frequency, and external disturbances. Additionally, we reviewed mathematical models, manufacturing processes, experimentation methodologies, and solutions which yielded some amazing outcomes.When sandwich structures with an MRE core layer are under influence of a magnetic field, the natural frequency, vibration amplitude, and the stiffness and damping characteristics of the structures can be dramatically altered. Furthermore, the increase in the tapering ratio with respect to width and thickness enhances natural frequencies while reducing loss factors in MRE cored sandwich structures, according to the recent study. In addition, sandwich structures with carbon nanoparticle reinforcement in composite face layers were explored. As a result, the sandwich structures become stiffer and more dampened. In MR materials, adding nanoparticles or fillers improves sedimentation control and improves the rheological characteristics.Partially treated MRE sandwich constructions can sometimes outperform fully treated ones in terms of damping characteristics while weighting less. By designing semi-active/active controllers for the structures, the performance of partially and completely treated structures may be enhanced.The majority of current research examines the vibration properties of the MRE sandwich beam in a uniform magnetic field. However, research on the vibration properties of MRE sandwich beams in non-homogeneous magnetic fields is relatively rare. The application of the MRE sandwich beam structure, in particular, is in its infancy. This is incompatible with fully exploiting the MRE′s characteristics in order to develop the corresponding frequency damping device. As a result, future research on the application of MRE sandwich beams must be strengthened. Additionally, there is a dearth of work in the literature on the nonlinear behavior of MRE sandwich structures and numerical analysis of functionally graded (FG) composite face sheets with an MRE core layer, both of which require additional attention in the future.


Better understanding of these processes could help prevent propagation of the degeneration into the tissue surrounding the injury and stimulate repair. However, the scenario of nervous system regeneration is complex and requires activation of a cohort of cellular and extracellular cascades by molecules that play essential roles in nervous system development, e.g., by initiating neurogenesis, reorganization of synaptic contacts and remodeling of the extracellular matrix. This Research Topic includes studies on Paramount importance is laid on the understanding of the highly complex microenvironment within the core of and around the injury site, thus following the ultimate aim of design of novel therapeutic strategies centered on molecules which target specific pathways beneficial for regeneration. These are exemplified by studies of extracellular matrix components such as tenascin (TnC), insulin-like growth factor-1 (IGF-1), and the metalloproteinase ADAM10, all of which modulate signaling cascades underlying nervous system repair, in particular by stimulating neuronal plasticity and other morphogenic events required for regeneration after injury.Tucić et al.). Similarly to TnC, IGF-1 also increases neurogenesis after traumatic brain injury (TBI) and improves the long-term survival rate of the hippocampal newborn neurons by sustaining their functionality. As a potential mechanism for these effects the authors have considered the activation of the mammalian target of rapamycin (mTOR), which regulates proliferation, axonal and dendritic growth. Moreover, controlled cortical impact TBI triggers mTOR activation in the neurogenic niches in a time-, region-, and injury severity-dependent manner, and the effect is amplified with conditional overexpression of IGF-1. As shown by Littlejohn et al., IGF-1 overexpressing mice exhibit upregulated posttraumatic neurogenesis, with a higher density of post-trauma-born granule cell layer neurons at 10 days after injury. Intriguingly, IGF-1 does not affect delayed astrocytic activation of mTOR in the dentate gyrus.TnC has a key role in intercellular communication providing fine tuning of the balance between excitation and inhibition as well as in immunomodulation. The molecule orchestrates neurogenesis at early developmental and late postnatal stages  the authors have identified 541 up-regulated and 488 down-regulated genes . The up-regulated genes revealed a profile which is typically displayed by quiescent stem cells and astrocytes, and the majority of these genes is mapped to the subependymal layers on the striatal or callosal aspects of the SVZ. Of note, the substantial number of up-regulated genes in the ependymal layer suggests implication of ependyma into stem cell biology. Based on the transcriptome analysis, the authors have identified several novel markers for primate SVZ including the apelin receptor, which is strongly expressed upon ischemia.Another highlight of the current Research Topic is the work of Weninger et al. have suggested that the heat shock, which causes granule cell dispersion in patients with temporal lobe epilepsy, when applied to the slices, does not affect the reelin-expressing Cajal-Retzius cells in the dentate gyrus but rather evokes a massive microgliosis. These findings underpin microgliosis as a novel marker to distinguish pathological granule cell dispersion from normal morphological variation in pediatric patients with history of febrile seizures without suffering epilepsy.Further important observations on organotypic hippocampal slices made by Our Research Topic suggests that counteracting the complexity of nervous system injury needs either a molecule with pleiotropic functions or cocktails of bio components with specific roles in stimulating or inhibiting the multitude of signaling pathways modulating regeneration. To find an omnipotent therapeutic molecule, however, seems to be quite ambitious a task, giving the complex demands of the regenerating nervous system.Stoyanova and Lutz). Ghrelin exercises its cytoprotective and repair capacity through increasing autophagy, beta-oxidation, cell viability and through reducing apoptosis. It activates cell cycle and facilitates a variety of morphogenic and dynamic events such as neurite outgrowth, myelination, synaptogenesis, cell migration and extracellular matrix reorganization. Unclear is still how ghrelin could trigger all these events and the authors suggest that since recovery recapitulates ontogenesis, where ghrelin plays a significant role, one could conclude that the neuropeptide would stimulate developmentally related molecules, neurotrophic and transcription factors if applied as a therapeutic agent.Among the numerous candidates examined so far, the neuropeptide and hormone ghrelin displays very promising therapeutic potential with its ability to cross the blood-brain-barrier, to balance metabolic processes, and to stimulate neuroregeneration and neuronal activity (as reviewed by In conclusion, the Research Topic articles illustrate the complexity of the pathological microenvironment in the injured nervous system and its numerous players, ranging from neural components such as neurons and glial cells with their transmitters, modulators and receptors, the components of the extracellular matrix for vascularization and/or neovascularization, up to the microglia, macrophages and other cells of the immune system with their chemokines and cytokines. These players are equipollent in their contribution to the regeneration of the injured nervous system and demand complex multi-targeting therapeutic strategies which are understood to be much more etiology-oriented rather than symptoms-based.All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


A comprehensive understanding of urinary tract infections (UTIs), one of the most common human infections, is required as they are complex and poorly understood diseases. Periurethral and vaginal colonization by rectal flora, with the constant presence of pathogens in the urethra, is the initial step of the recurrent UTIs pathway. Current scientific data describe the genetic, etiological, biological, and behavioral risk factors for recurring UTIs, but they do not include the effect of intestinal barrier function on the disease. Although gut microbiota has been proposed as the main source for UTIs, the cross-talk between intestinal barrier dysfunction and the recurrence of UTIs has not yet been supported by scientific data. In this opinion review, based on published data and the results of our clinical studies, I aimed to outline the possible contribution of intestinal barrier dysfunction to the pathogenesis of recurrent UTIs. I believe that the unanswered questions raised by this review can guide further experimental and controlled studies to clarify the mechanisms underlying the role of intestinal barrier dysfunction in the pathogenesis of recurrent UTIs. Urinary tract infections (UTIs) are a worldwide weighty medical, economic, and social burden due to their high prevalence among sexually active women . About 7The normal functioning of the gastrointestinal tract is balanced between the microbiota composition and the maintenance of the permeability of the mucosal barrier . Under pEscherichia coli (UPEC) entry, leads to host inflammatory responses  strain 131 over 5 years in a woman with RUTIs, indicated the intestine as a reservoir for the recurrences  that can adapt to the competitive and volatile intestinal environment and colonize the urinary tract due to their numerous virulence factors and adhesive ability  have confidently filled the niche of UTIs pathogens (E. coli, Gram-positive bacteria are more often shed in complicated UTIs and associated with catheters, functional or anatomical abnormalities, comorbidities, immunosuppression, and nosocomial infections (How can we explain the significant spread of Gram-positive bacteria in uncomplicated RUTIs?Since 1885, when Theodor Escherich first identified E. coli , this paathogens . As statathogens , and up athogens . Accordiathogens . Howeverfections . TherefoLactobacillus spp. and Bifidobacteria, and an increased number of conditionally pathogenic enterobacteria, E. coli, Clostridium, and Staphylococcus spp. in feces samples (Should intestinal barrier dysfunction be considered a complicating factor for RUTIs? If yes, understanding the approaches that can improve intestinal barrier function may unlock new therapeutic strategies for the treatment and prevention of RUTIs. In addition, an honest answer to the question, How often do we prescribe an additional examination to exclude intestinal dysbiosis or barrier dysfunction in women without clinical manifestations? could significantly reduce the prevalence of uncomplicated RUTIs. In our experience, in the absence of clinical symptoms, the diagnosis of gut dysbiosis and/or intestinal barrier dysfunction is usually not carried out and remains unrecognized. I in no way urge readers to prescribe unreasonable, numerous, and expensive diagnostic methods, and do not underestimate the significance of other complicating factors for RUTIs. I simply call on readers to think about the diagnostic necessity and significance of intestinal barrier dysfunction in the pathogenesis of RUTIs.Again, the use of broad-spectrum antibiotics resulting in intestinal barrier dysfunction is the obvious explanation. However, unfortunately, in the current era of microbiome research, this issue has not been supported by scientific data. Based on comprehensive clinical examinations, we have previously demonstrated that all women with uncomplicated RUTIs were diagnosed with gut dysbiosis and decreased contents of  samples . It shou samples . Moreove samples . The pre samples . This leMultiple environmental, genetic, host-related, and virulence risk factors play a determining role in the development of uncomplicated RUTIs. However, whatever the trigger, impaired intestinal barrier function appears to play a central role in urinary tract, enteric, and/or systemic inflammation. Although cross-talk between intestinal barrier dysfunction and RUTIs is not yet thoroughly understood, in this opinion review, I have presented a scientific rationale and underlined the possible role of intestinal barrier dysfunction in the pathogenesis of RUTIs. I believe that addressing the questions posed and many other questions will fill the knowledge gap on how intestinal barrier dysfunction is caused and how it can be restored in patients with RUTIs. As more and more research focuses on intestinal barrier function and its modulation, further potential therapeutic targets will result in the expansion of existing strategies for the treatment and prevention of RUTIs and provide new options for minimizing the prescription of antibiotics.


The main purpose of English learning is to communicate and interact in global contexts. However, in English as a foreign language (EFL) contexts as in China, most of the students have limited interactional competence in contrast to their grammatical and structural competence. The reason is that Chinese classrooms mostly lack an interactional climate. This calls for an urgent need to develop interpersonal interaction skills by EFL teachers via appropriate strategies. To this end, this article presents an overview of nine interpersonal communication skills/strategies which are pivotal in L2 education. It also describes their definitions and related theories. Moreover, the outcomes of such strategies in aural skills are also explained. Finally, implications, research gaps, and future avenues for research are provided. Over the past couple of decades, the educational context of China has made strident advancing steps regarding English language teaching and learning . While COne of the most important tasks to be accomplished by L2 teachers and students in EFL settings, like China, is establishing a classroom climate based on positive interpersonal interaction skills. This necessitates a friendly rapport between the teacher and his/her students. Teachers must take into account the emotions and interests of their pupils in the class . With thNow the intention of EFL classes is way beyond the simple presentation of linguistic information, but a place where social, psychological, and emotional interactions are provoked . It is bverbal, non-verbal = body language, and para-verbal = tone, intonation) that occurs among students and their teachers, which seeks to convey meaning, perform academic tasks, and establish relationships  to display similarity, get approval from the listener, or develop the conversation , grew out of Speech Accommodation Theory (SAT) proposed by ersation . ConvergThe attachment theory (AT) was proposed by British psychiatrist Many interactional strategies may exist in English communication owing to its dynamic nature.care, clarity, credibility, rapport with students, stroke, immediacy, confirmation, humor, and praise. The concept of care was first proposed by However, the most popular and well-documented ones suitable for EFL classes are those proposed by The concept of stroke concerns one’s natural expectation of recognition by others. In the EFL classroom, teachers are the strokers and learners are strokees. By nature, students search for teachers’ stroke or recognition and when it is absent, they feel deprived in the learning process . As an iThe mentioned nine fundamental interpersonal communication strategies and other linguistic strategies apply to speaking and listening skills in that they can encourage learners to cooperate, engage in the class, and form a positive rapport that facilitates interactions. In aural skills which are more demanding for EFL students, immediacy, care, and clarity put learners at ease and inspire them to speak out without fear of being wrong. Similarly, these interpersonal strategies allow learners to make interpretations about listening tasks in a friendly atmosphere that gives positive feedback. As aural skills are full of hesitation, pauses, informal phrases, hedges, and redundancies, EFL students usually feel dubious to initiate an interaction of making interpretations. Consequently, these positive interpersonal interaction strategies can soothe the tension and help learners decode and encode language with great panache. Moreover, these strategies generate motivation, enthusiasm, interest, and willingness to engage in speaking and listening activities.In a global context, studies have been carried out on interactional strategies in the EFL setting, especially from the perspective of learners and teachers. The appropriate and purposed use of effective interactional strategies in teaching contributes to successful interaction and pedagogic qualities of competent teachers . BesidesIn EFL speaking or listening setting, effective engagement is the premise of interaction. It becomes the focus to motivate and guide low-level learners’ engagement through various communication strategies . FurtherThe current teaching technologies and social demands of language learning provide learners or instructors to reexamine and reflect the relationship between learners and instructors. With the aid of current various multi-media, EFL interaction typologies extend to learner-learner, learner-instructor, and learner-media-instructor style. Especially due to the severe spread of the COVID-19 pandemic in the global area, the flipped classroom or online teaching and learning becomes essential and presents a new tendency of knowledge inquiry and interpersonal interaction. Even though online teaching endows participants with more freedom and flexibility, it challenges effective interpersonal interaction. The purposed interpersonal interaction strategies illustrate the new technology-self and information-self to build a new balanced and rapport relationship to gain knowledge. Effective interpersonal communication skills are impellers of EFL practices. It seems new media and technologies provide other interaction patterns, besides learners-learners and learners-instructors. The learning materials and assistant technology have become part of the media of interaction. Thereby, another interactional pattern emerges, learner-media-instructor style, especially in an AI intelligent age and mask-wearing social interactions. Online learning or interaction in EFL becomes appropriate and necessary currently.In light of this review article, it can be argued that the use of effective interpersonal communication skills/strategies has implications for EFL teachers, students, teacher educators, and researchers. From the EFL teaching evaluation level, the judgment and evaluation of effective interactional strategies in the EFL setting lead to further reflection and exploration about the process of teaching and learning agents, processes and effects. The nine communicative strategies just provide more facets to conceptualize the effect of the interactional practice. EFL teachers can use the results to create a positive classroom climate in which these nine strategies are employed in the class, especially in aural skills courses. Moreover, their knowledge of the emotional aspects of L2 education will increase. Likewise, EFL students can play their part in forming a positive rapport in the class that encompasses the rest of interpersonal skills. From the teaching training or self-development aspect, teacher educators can run workshops and training courses on teaching interpersonal interaction strategies to pre-service and in-service EFL teachers offering practical techniques regarding each skill. L2 researchers can use the idea proposed in this article and run cross-cultural studies to see if such strategies vary across different level learners or contexts. From the research content and methods, there are various meaningful perspectives to be mentioned and focused on in learning and instruction of EFL settings. The emotional effect of interactional strategies is worthwhile to be further discussed, especially in the flipped or blending EFL setting. Due to the appearance of the new interactional facilities, personal communicative software and interactional platforms extend the manner and the content of the interaction. The compensation and scaffolding function of interactional strategies in media-assisted EFL settings extend the scope and content of effective teacher-student interaction. Most studies on these constructs have been quantitative and one-shot; hence, scholars can conduct qualitative, mixed-methods, and longitudinal studies. EFL teachers’ and students’ perceptions and practices of these strategies are also recommended to future researchers. The comparative studies and field researches of intercultural communication in EFL online learning about different learners, contents, and manners can be further explored. Finally, experimental studies can be done on teaching these nine interpersonal interaction skills in China and other contexts to see if they can be improved by appropriate intervention.The author confirms being the sole contributor of this work and has approved it for publication.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.