Embryonic stem cells (ESCs) and adult stem cells (ASCs) possess the remarkable capacity to self-renew while remaining poised to differentiate into multiple progenies in the context of a rapidly developing embryo or in steady-state tissues, respectively. This ability is controlled by complex genetic programs, which are dynamically orchestrated at different steps of gene expression, including chromatin remodeling, mRNA transcription, processing, and stability. In addition to maintaining stem cell homeostasis, these molecular processes need to be rapidly rewired to coordinate complex physiological modifications required to redirect cell fate in response to environmental clues, such as differentiation signals or tissue injuries. Although chromatin remodeling and mRNA expression have been extensively studied in stem cells, accumulating evidence suggests that stem cell transcriptomes and proteomes are poorly correlated and that stem cell properties require finely tuned protein synthesis. In addition, many studies have shown that the biogenesis of the translation machinery, the ribosome, is decisive for sustaining ESC and ASC properties. Therefore, these observations emphasize the importance of translational control in stem cell homeostasis and fate decisions. In this review, we will provide the most recent literature describing how ribosome biogenesis and translational control regulate stem cell functions and are crucial for accommodating proteome remodeling in response to changes in stem cell fate. The development of high-throughput methods for studying gene expression has considerably improved our understanding of cellular regulatory networks and our insight into how a multitude of molecular processes are coordinated to adapt the proteome to specific cell functions and respond accurately to fluctuating environmental cues. These multi-omics approaches have allowed researchers to investigate large-scale changes in epigenetic status, chromatin structure, as well as RNA expression and stability. The fields of stem cell and developmental biology have also benefited from these technological breakthroughs. Many studies have characterized epigenetic regulations of chromatin structure in stem cells and during early embryonic development. RNA expression has been extensively explored in non-synchronized cell cultures but also at the single-cell level, either from in vitro models or dissociated tissues, therefore providing the scientific community with precious resources. However, multiple studies suggested that messenger RNA (mRNA) levels are poorly correlated with protein levels ,2,3. IndDuring the past decade, the translation process has been thoroughly investigated in stem cells and increasing evidence directly links regulations of translation and of ribosome biogenesis to the control of stem cell homeostasis and cell fate. In this review, we will discuss current knowledge on (i) the global regulation of translation in stem cells and its role during cell fate transition, on (ii) the contribution of ribosome biogenesis to the control of stem cell homeostasis, and (iii) we will finally present new emerging concepts proposing that ribosomes, largely considered to be devoid of regulatory activities so far, could directly control specific gene expression programs and potentially impact stem cell biology and early embryonic development.ESCs represent an interesting model to study gene expression due to an atypical molecular identity. Although they possess a relatively open chromatin structure and a highly permissive transcription, ESCs must establish and maintain the expression of specific pluripotent genetic programs while concomitantly silencing lineage-specific genes. In addition, ESCs need to maintain the capacity to respond to cues inducing changes in cell identity by quickly rewiring gene expression programs. Hence, the translation process, which occurs downstream of most mRNA maturation steps, could indeed rapidly regulate protein synthesis without demanding complex modulations of epigenetic and RNA expression pathways, and may therefore be a crucial regulatory step governing gene expression programs required for both stem cell identity and transitions in cell fate  6,7,8].,7,8.6,7,35S-methionine labeling clearly demonstrated that translational efficiency is two-fold lower in undifferentiated ESCs compared to differentiated EBs. In addition, the polysome density  was increased by 60% in EBs compared to undifferentiated ESCs, suggesting that mRNAs are more actively translated in EBs. This observation that translational efficiency is lower in ESCs than in differentiated progenies has been supported by other reports . I. I108]. Hence, in the context of ribosomal concentration deficiencies caused by ribosomopathies, mRNAs with low translation initiation rates will be more impacted than mRNAs translated with higher initiation rates. This hypothesis is supported by the translation impairment of GATA1 mRNAs, an important erythroid transcription factor in the context of Diamond–Blackfan anemia (DBA), which is characterized by a profound anemia associated with developmental defects, such as skeletal abnormalities . InteresWhile the “ribosome concentration” model has been proposed to explain tissue-specific phenotypes in the context of ribosomopathies, direct evidence that regulation of the ribosome concentration controls stem cell-specific gene expression and participates in cell identity transitions is lacking. However, some indirect observations support that stem cells are particularly sensitive to changes in ribosome concentration. First, there is evidence that RP expression varies while ESCs undergo differentiation, although whether these changes affect ribosome concentration or simply the free pool of RPs has not been rigorously addressed , Hebras and colleagues [O-Me. Interestingly, they observed that the expression of some snoRNAs, including SNORD78, is highly dynamic during development and is correlated with the methylation levels of specific sites. Additional evidence establishes that the expression of snoRNAs can be tissue specific, further supporting the possibility that specific rRNA modifications may be regulated and could generate heterogeneously modified rRNAs in physiological contexts [OMe-seq approach, Incarnato and colleagues [O-Me in a stem cell model (mouse ESCs). Interestingly, they revealed that 2’O-Me patterns are generally conserved between Hela cells and ESCs, although some differences in 2’O-Me levels were identified at specific sites. However, the functional impact of these site-specific variations has not yet been investigated, and whether the global 2’O-ME landscape is modulated upon ESC differentiation remains to be established.Very recently, using RiboMeth-seq profiling of rRNA 2’lleagues  describecontexts . Finallylleagues  providedAltogether, observations that rRNA is heterogeneously modified under specific conditions or in specific tissues suggest that ribosomes may show some degree of plasticity at the rRNA level. However, further studies should address whether rRNA modification fluctuations occur on bona fide mature and active ribosomes and impact ribosome functions or activity. S. cerevisiae has been an interesting model to address this question in eukaryotes. Recently, Ferretti and colleagues [Demonstrating the existence of “specialized” ribosomes is technically complex as it requires laborious biochemical purifications and characterizations of active ribosomes, and proofs that changes in composition specifically impact ribosome functions. In addition, many studies relied on artificial RPs or on the depletion of paralogs since physiological modulations of ribosome composition are difficult to identify. lleagues  providedRecent developments of sensitive and quantitative proteomic analyses as well as high-throughput methods to measure whole transcriptome translation, such as Ribo-seq, have significantly accelerated the identification of specialized ribosomes in mammals, and more precisely in ESCs. Hence, Slavov and colleagues  elegantlIn a very elegant study, the team of Maria Barna  recentlyO-Me, can provide ESCs with specific ribosome functions, either directly by influencing rRNA properties , or indirectly by modifying ribosome biogenesis and RP composition. Further studies should map rRNA modifications, in particular Ψ, in ESCs undergoing changes in cell identity and determine which rRNA modification sites provide ribosomes with specific properties important for cell identity and fate transitions.Many of the observations supporting ribosome plasticity have been made individually, either at the protein or rRNA levels. Of note, it is still unclear whether the heterogeneity of rRNA modifications, especially 2’Predicting translational regulation by the ribosome will therefore require additional efforts in order to combine both influences of ribosome concentration modulations (“concentration model”), which has only been studied at the scale of the tissue so far, and of ribosome composition (rRNA and RPs). Depending on the cellular model studied, one model might prevail over the other, or they might be tightly coordinated to support gene expression programs that ensure stem cell identity or changes in fate.The intrinsic properties of stem cells, which enable them to maintain a specific identity while remaining sufficiently flexible to rapidly transition towards different cellular fates, are fascinating and provide powerful models to investigate the coordination of gene expression processes. We propose that the translational process is a major actor of gene expression regulation in stem cells, which not only precisely sustains a specific proteome required for maintaining undifferentiated cell identity and stem cell multipotent properties but also rapidly rewires gene expression in response to fate transition cues or environmental insults. Thus, most signaling pathways known to regulate stemness and differentiation also control global translational efficiency . Future In addition to global translational regulation, stem cell properties also rely on a complex network of genes undergoing specific translational regulation that imply specific mRNA cis elements, such as uORFs or IRESs. Although not discussed herein but documented in many other reviews, many trans factors, including RNA-binding proteins  or non-coding RNA , regulate gene-specific translation and occupy an important part in the global control of stem cell-specific proteomes. Thus, translational control of stem cell identity and changes in fate require the complex integration of comprehensive translational regulatory inputs as well as gene-specific translational regulation, which comprise an extremely complex network of cis- and trans-acting elements. In addition, ribosome biogenesis and homeostasis play a crucial role in the translational regulation network controlling stem cell identity and proved to be central regulators of cell fate transitions as well as central hubs coordinating multiple gene expression processes and cellular programs . Finally, we presented emerging new concepts suggesting that ribosomes may carry out regulatory functions unlike previously appreciated . AlthougFinally, we propose that uncovering mechanisms governing translational control and ribosome biogenesis in stem cells represents a promising approach to investigate the contribution of these processes to pathological cancer stem cells (CSCs) and to design new therapeutic molecules targeting CSC translational regulatory pathways, CSC-specific ribosome biogenesis processes, or “specialized” CSC ribosomes.


Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disorder, predisposing to malignant ventricular arrhythmias leading to sudden cardiac death, particularly in young and athletic patients. Pathological features include a progressive loss of myocardium with fibrous or fibro-fatty substitution. During the last few decades, different clinical aspects of ACM have been well investigated but still little is known about the molecular mechanisms that underlie ACM pathogenesis, leading to these phenotypes. In about 50% of ACM patients, a genetic mutation, predominantly in genes that encode for desmosomal proteins, has been identified. However, the mutation-associated mechanisms, causing the observed cardiac phenotype are not always clear. Until now, the attention has been principally focused on the study of molecular mechanisms that lead to a prominent myocardium adipose substitution, an uncommon marker for a cardiac disease, thus often recognized as hallmark of ACM. Nonetheless, based on Task Force Criteria for the diagnosis of ACM, cardiomyocytes death associated with fibrous replacement of the ventricular free wall must be considered the main tissue feature in ACM patients. For this reason, it urges to investigate ACM cardiac fibrosis. In this review, we give an overview on the cellular effectors, possible triggers, and molecular mechanisms that could be responsible for the ventricular fibrotic remodeling in ACM patients. Arrhythmogenic cardiomyopathy (ACM) is a rare genetic cardiac disease, with an incidence estimated in 1:5000 , which aArrhythmogenic cardiomyopathy is a rare cardiac pathology characterized by cardiomyocytes (CM) death and replacement of myocardium with fibrotic or fibro-fatty tissue. The fibrotic and fibro-fatty substitution, regardless of the ventricular district, progresses from epicardium to endocardium provoking structural and functional myocardial alterations . GeneralPLN) than those mutated in desmosomes (DSP) or desmoglein 2 (DSG2) are often associated with LV-forms  involvement has also been reported either in advanced stages of the RV disease or in peculiar LV-dominant forms. Particularly, in the LV, myocardial remodeling mainly affects the posterolateral area and the original concept of “triangle of dysplasia,” has evolved to a new scenery of a “quadrangle of ACM” . It has smosomes . Among dLV-forms . MechaniThe presence of fibro-fatty substitution in ACM hearts could be evidenced through different diagnostic tools. Echocardiography is the standard imaging technique used to evaluate structural and functional abnormalities of the RV chamber, although it provides limited information on the presence and extent of fibrotic replacement. For these reasons, magnetic resonance imaging (MRI) is currently increasingly recommended for a definitive diagnosis . MRI allInvasive tissue characterization to confirm ACM diagnosis can be obtained by an endomyocardial biopsy (EMB). In this setting, an extensive application of EMB has been limited by the low sensitivity of biopsies usually obtained from the interventricular septum, not frequently involved by the disease. In the last few years, EMB is performed after a complete and detailed 3D electroanatomic mapping (EAM) of the ventricular chamber. EAM is used to detect bipolar and/or unipolar low potential areas, which, in ACM, mostly correspond to fibrotic or fibro-adipogenic scar tissue . Thus, aThe compromised heart of ACM patients undergoes a functional worsening when subject to intense physical exercise. The practice of physical activity at a competitive level represents one of the major triggers for life-threatening arrhythmias and sudden death in the ACM setting and therefore it is highly discouraged for ACM patients . EnduranIt has been reported that sympathetic dysinnervation characterize both the left  and the Moreover, the β-adrenergic system could regulate the extracellular matrix (ECM) protein turnover: norepinephrine could increase the expression of metalloproteinase-2 (MMP-2) and decrease the expression of tissue inhibitors of metalloproteinases 1 and 2 (TIMP-1/2) during cardiac remodeling .High-level sport activity also implies an excessive effort of the heart muscle.Excessive heart stimulation can cause mechanical stretch of fibers. It has been reported that athletes with a history of endurance sport have increased levels of plasmatic TGFβ1 and develop myocardial fibrosis in contrast to novice athletes . While tIn ACM patients, due to  the geneExcessive training is also associated with oxidative stress increase . UncontrAlthough numerous pieces of evidence concur to a role of oxidative stress in fibrosis, its implication in ACM fibrotic remodeling still to be investigated. Indeed, only one report described increased ROS levels in an ACM cell model .An important independent fibrosis cofactor in ACM hearts is inflammation. ACM hearts are characterized by progressive CM death that is replaced by non-contractile fibrotic tissue according to a reparative mechanism against myocardial loss .Cardiac fibroblasts and CM are in contact through soluble factors and cell–cell interactions. CM death may represent the initial phase in the remodeling process, by initiating an inflammatory response, myofibroblast activation, and myocardial scar formation . Moreovein vitro, different ACM phenotypic features as distribution of plakoglobin (PG), Cx43, and GSK3β, apoptotic rate, and inflammatory cytokines production. In vivo, the pharmacological inhibition of NFκB signaling improves contractile function, reduces the amount of ventricular myocardial necrosis and fibrosis and the number of apoptotic cells, and normalizes the ECG abnormalities , collagen type III (which forms thin fibers that ensure elasticity) and in a minor fraction by collagen type IV, V, and VI. Moreover, cardiac ECM contains glycosaminoglycans, glycoproteins, and proteoglycans . The ECMExtracellular matrix deposition is mostly associated with fibroblasts activation. Different proteinases such as matrix MMPs and TIMPs overall act to a fine regulated homeostatic balance between synthesis and degradation .Following cardiac injury, ECM degradation occurs and promotes inflammatory cell infiltration and fibroblast proliferation. The following fibroblasts to myofibroblasts differentiation represents the event responsible for consistent novel ECM deposition during scar formation.Alterations in ECM composition and turnover are involved in different cardiac diseases characterized by adverse remodeling with loss of myocardium integrity . PatientThe molecular basis of ECM organization and remodeling in ACM is still under-investigated. Recently few papers identified a signature of ACM cardiac cell microRNAs, known to be involved in ECM turnover and mechanosensing .Cardiac injury represents a trigger for the activation of immune cells that in turn stimulate fibroblasts proliferation and differentiation in myofibroblasts. During physiological cardiac repair, after the wound closure, myofibroblasts apoptosis occurs with consequent resolution of the process. On the contrary, during pathological conditions, myofibroblast secretory activity results extended, inducing the switch from reparative process to fibrotic scar formation .To date, the cellular source of myofibroblasts is still not fully defined. The most reliable hypothesis is that resident cardiac fibroblasts are activated during damage, as following pressure overload, with consequent differentiation into myofibroblasts. Notably, it has been reported that ventricular resident Tcf21 positive fibroblasts are a source of myofibroblasts involved in cardiac fibrosis after myocardial infarction .In this context, it is known that epicardial cells undergo epithelial-to-mesenchymal transition (EMT) to generated fibroblasts that could populate the cardiac injury area promoting fibrotic remodeling . NotablyRecently, a subset of resident adult cardiac stem cells characterized by the expression of PW1 has been identified as responsible for fibrosis after myocardial infarction. The amount of PW1 positive cells is increased in the ischemic damaged area. PW1 cells are characterized by the high expression of profibrotic genes and the ability to differentiate into fibroblasts .However, other studies indicate that cardiac fibroblasts could derive from resident cardiac mesenchymal cells (C-MSC). In the injured mouse heart, as during myocardial infarction, C-MSC resident population (not recruited from the bone marrow) express stem cell and fibroblast markers like collagen type I and DDR2, suggesting their involvement in scar formation . C-MSC hMoreover, the possible origin of cardiac fibroblasts from non-cardiac departments is still a matter of debate. It has been reported that bone marrow-derived cells could generate fibroblasts that are in turn involved in cardiac scar formation after myocardial infarction . Indeed,In addition, fibrocytes could be a further circulating source of cardiac fibroblasts as CD34/CD45 positive cells that expressed fibroblast markers and have been identified in a model of fibrotic ischemia/reperfusion cardiomyopathy .The most well-known pro-fibrotic cytokine involved in cardiac fibrosis is TGFβ . It partSpecifically, binding of TGFβ to its receptors is the starting point for the activation of downstream signaling cascade that involves different mediators of the canonical (SMADs proteins) or non-canonical  pathways.TGFB 3, responsible for the ARVD1 form  has been reported to contribute to the progression of fibrosis in an ACM animal model . The binThe ACM specific cardiac remodeling is characterized by the progressive substitution of ventricular myocardium of patients by non-contractile fibrotic or adipose tissue. While adipogenesis has been extensively studied in this pathological context, fibrosis, a cardiac phenotype common to most cardiac diseases, remains under-investigated.Myocardial fibrosis is a clinical feature shared by several heart diseases such as ischemic cardiomyopathy, dilated cardiomyopathy, hypertrophic cardiomyopathy, hypertensive heart disease, and heart failure. Ventricular fibrosis may develop different modality depending on disease progression and typically result in the formation of substrate vulnerable to arrhythmic events. The cardiac fibroblast activation and differentiation into myofibroblasts and the resulting scar formation commonly occur following a cardiac injury. This event represents a reparative process but during a pathological cardiac condition, it becomes a persistent status that leads to altered myocardial structure and function. As described in other cardiac diseases, the presence of fibroblasts and fibroblast progenitors, the excessive collagen deposition, and the following modification of mechanical stiffness may improve the tissue discontinuity occurring in the ACM hearts. Therefore, most of what is known about fibrotic processes and is summarized in this review is iterated from studies in other settings. However, it is expected that triggering agents, cellular effectors, and mechanisms are comparable to what previously described. Responsible cells are likely cardiac fibroblasts, either from FAP progenitors or C-MSC. ACM key pathogenic mechanisms such as Wnt and Hippo are playing direct roles, with the support of TGFβ-mediated mechanisms, which prompts fibrosis as an alternative to adipogenesis. The whole process is possibly triggered by genetically driven myocardial damage, and inflammation, oxidative stress, mechanical and neuro-hormonal signaling are magnifying factors , thus reNevertheless, ACM specific fibrosis remains a scientific gap of knowledge to be filled with further studies, in order to clarify specific pathways as target for novel specific therapeutic actions.All authors contributed to the writing of the paragraphs and to the critical review of them.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.


Community support services are an integral component of aging in place. In social housing, older adult tenants struggle to access these services due to the siloed nature of housing and health services. This study aims to describe the relationship between community support services and social housing for older adults and examine ways to optimize delivery. Data on government-funded community support services delivered to 74 seniors’ social housing buildings in Toronto, Ontario was analyzed. Neighbourhood profile data for each building was also collected, and correlational analyses were used to examine the link between neighbourhood characteristics and service delivery. Fifty-six community agencies provided 5,976 units of services across 17 service categories, most commonly mental health supports, case management and congregate dining. On average, each building was supported by nine agencies that provided 80 units of service across 10 service categories. Buildings in neighbourhoods with a higher proportion of low-income older adults had more agencies providing on-site services , while those in neighbourhoods with more immigrants , non-English speakers , and visible minorities  received fewer services. Findings point to a lack of coordination between service providers, with multiple agencies offering duplicative services within the same building. Vulnerable seniors from equity-seeking groups, including those who do not speak English and recent immigrants, may be excluded from many services, and future service delivery for seniors should strive to address disparities in availability and access.


Virus-mediated gene therapy has the potential to deliver exogenous genetic material into specific cell types to promote survival and counteract disease. This is particularly enticing for neuronal conditions, as the nervous system is renowned for its intransigence to therapeutic targeting. Administration of gene therapy viruses into skeletal muscle, where distal terminals of motor and sensory neurons reside, has been shown to result in extensive transduction of cells within the spinal cord, brainstem, and sensory ganglia. This route is minimally invasive and therefore clinically relevant for gene therapy targeting to peripheral nerve soma. For successful transgene expression, viruses administered into muscle must undergo a series of processes, including host cell interaction and internalization, intracellular sorting, long-range retrograde axonal transport, endosomal liberation, and nuclear import. In this review article, we outline key characteristics of major gene therapy viruses—adenovirus, adeno-associated virus (AAV), and lentivirus—and summarize the mechanisms regulating important steps in the virus journey from binding at peripheral nerve terminals to nuclear delivery. Additionally, we describe how neuropathology can negatively influence these pathways, and conclude by discussing opportunities to optimize the intramuscular administration route to maximize gene delivery and thus therapeutic potential. RPE65-associated retinal dystrophy (voretigene neparvovec marketed as Luxturna) and SMN1-linked spinal muscular atrophy , as well as non-neuronal conditions  also permits targeting of the peripheral (PNS) and central nervous systems (CNS). These two administration routes for neuronal delivery have been extensively covered in recent reviews , adeno-associated virus (AAV) and lentivirus LV; —with a fAdenoviridae encompasses more than 300 different vertebrate-infecting types, including seven human AdV (HAdV) species (A to G) currently comprised of ≈80 types classified by serology or sequencing. HAdVs primarily cause ocular, gastrointestinal, or respiratory infections  to replicate, AAVs are non-enveloped, single-stranded DNA viruses discovered as AdV preparation contaminants  are removed from the LV genome, and instead provided by separate expression plasmids for in vitro packaging  shows superior neuronal transduction and transport when injected into the rat striatum and spinal cord  or equine infectious anemia virus (EIAV)]. LV tropism is mediated by the viral envelope, which is engineered to include glycoproteins from other enveloped viruses in a process called pseudotyping  and hepatocyte growth factor receptor (HGFR) for both AAV2 and AAV3, platelet-derived growth factor receptor (PDGF) for AAV5, and epidermal growth factor receptor (EGFR) for AAV6  and, depending on the active co-receptor, can activate both pro-survival or pro-death signaling  with co-migration confirmed for p75NTR  at peripheral nerve terminals that can then be therapeutically targeted with a different virus, as has been demonstrated with AAV-mediated CAR expression for increased AdV binding and uptake (Larochelle et al., Unfortunately, many of these strategies are not currently a clinical possibility, for obvious reasons. Nonetheless, their implementation in the laboratory to deliver genes within the therapeutic range, along with the development of novel and improved tools to assess virus transduction and treatment efficacy (Han et al., via paracrine mechanisms. Moreover, some viruses can escape from the initially transduced neurons, resulting in widespread gene delivery throughout the spinal cord, brain stem, and sensory ganglia. Importantly, this indicates that not all muscles need to be injected to obtain broad cellular dosing. Unfortunately, neuropathology is likely to hinder the effectiveness of intramuscular gene therapy delivery (via this method. Also, the intramuscular administration could be combined with, for example, intrathecal delivery to further enhance CNS uptake. However, due to the immune response, repeated successful dosing is unlikely, and hence such treatments need to be given within a short time frame to circumvent this impediment. Nevertheless, by factoring in a detailed understanding of the dynamics of viruses and host cell receptors, especially in the context of peripheral nerve biology and neuromuscular pathology, perhaps this minimally invasive delivery method can contribute to successful gene therapy in the future.Gene therapy injected into the skeletal muscle for delivery to neurons holds therapeutic promise for peripheral nerve disorders. Motor and sensory nerve terminals located within muscles can act as therapeutic conduits not only for the innervating neurons  but alsodelivery ; but innAT and JS wrote the manuscript and have approved the submission of this work.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.


Despite technological and interpretative advances, the non-invasive modalities used for pre-surgical evaluation of patients with drug-resistant epilepsy (DRE), fail to generate a concordant anatomo-electroclinical hypothesis for the location of the seizure onset zone in many patients. This requires chronic monitoring with intracranial electroencephalography (EEG), which facilitates better localization of the seizure onset zone, and allows evaluation of the functional significance of cortical regions-of-interest by electrical stimulation mapping (ESM). There are two principal modalities for intracranial EEG, namely subdural electrodes and stereotactic depth electrodes (stereo-EEG). Although ESM is considered the gold standard for functional mapping with subdural electrodes, there have been concerns about its utility with stereo-EEG. This is mainly because subdural electrodes allow contiguous sampling of the dorsolateral convexity of cerebral hemispheres, and permit delineation of the extent of eloquent functional areas on the cortical surface. Stereo-EEG, while having relatively sparse sampling on the cortical surface, offers the ability to access the depth of sulci, mesial and basal surfaces of cerebral hemispheres, and deep structures such as the insula, which are largely inaccessible to subdural electrodes. As stereo-EEG is increasingly the preferred modality for intracranial monitoring, we find it opportune to summarize the literature for ESM with stereo-EEG in this narrative review. Emerging evidence shows that ESM for defining functional neuroanatomy is feasible with stereo-EEG, but probably requires a different approach for interpretation and clinical decision making compared to ESM with subdural electrodes. We have also compared ESM with stereo-EEG and subdural electrodes, for current thresholds required to evoke desired functional responses vs. unwanted after-discharges. In this regard, there is preliminary evidence that ESM with stereo-EEG may be safer than ESM with subdural grids. Finally, we have highlighted important unanswered clinical and scientific questions for ESM with stereo-EEG in the hope to encourage future research and collaborative efforts. A behavioral response to direct electrical stimulation of the human brain was first reported in 1874 from Cincinnati when Bartholow stimulated visible brain tissue in a 30-years-old woman whose parietal bone was eroded by a scalp epithelioma  who are being evaluated for neurosurgical treatment. The overarching goal of epilepsy surgery is to ensure long-term seizure freedom and avoid or minimize postoperative neurological deficits. Thus, in preparation for epilepsy surgery, a multi-modal approach is used to develop a patient-specific hypothesis for the location of the seizure onset zone and determine the functional significance of adjacent cortical regions, initially by using several non-invasive tests. However, these non-invasive modalities may not always converge on a single location of the seizure-onset zone and have a limited spatial resolution for defining functional neuroanatomy. Therefore, chronic intracranial electroencephalography (EEG) is required in several DRE patients and offers superior sensitivity for localization of seizure-onset zone mainly because of a higher signal-to-noise ratio compared to scalp EEG  and stereo-EEG (SEEG). Although SEEG was developed in the 1960s by Bancaud, Talairach, and others, it has made a resurgence in the last decade in the United States , probablHowever, compared to SDE which allows contiguous sampling from the dorsolateral convexity of the cerebral hemispheres, SEEG lacks cortical surface contiguity but allows sampling from deeper cortices, such as insula or depth of sulci, and medial and basal surfaces of cerebral hemispheres, which have minimal or no access with SDE . Given tESM consists of passing small currents through surgically implanted intracranial electrodes and recording behavioral and electrographic responses. Extra-operative ESM is a time and resource-intensive procedure, requiring one or more sessions of several hours each, sometimes spread over multiple days.Some providers choose to administer an anti-seizure medication before ESM to decrease the risks of after-discharges (AD’s) and iatrogenic seizures. However, there is no consensus on this practice, with scant data on its safety and effectiveness. A retrospective pediatric study found that the incidence of ESM-induced seizures was 23% in 40 patients pre-medicated with fosphenytoin, compared to 43% in 82 non-pre-medicated patients  or 60 Hz (in Europe). However, there is some evidence that stimulation of SDE at lower frequencies may result in reduced incidence of AD’s  with SEEG ESM . The guiding principle is that electrode(s) lying in the seizure-onset zone should be stimulated last, and only if it is considered essential to stimulate within the ictal core. With SEEG, we always stimulate from deep to superficial contacts, on individual electrodes. This is probably safer due to the lower risk of seizures on white matter stimulation and obviates the concern that deeper contacts may be refractory after stimulation of the superficial contacts in the cortex, because of preferential orthodromic conduction of the stimulation impulse  lying in the pre-central gyrus when trying to map the primary motor cortex and then move peripherally towards other electrodes to define the boundaries. This is less intuitive with SEEG compared to SDE. For language ESM, we prefer to stimulate the presumptive frontal language sites first, and then the posterior language regions in temporal and parietal lobes, based on some evidence for directional connectivity from temporal to frontal language regions in the perisylvian language network  scanners, and in some cases, even with 3T scanners. SDE consists of 3–5 mm metal discs, having 1–2 mm exposed surfaces, embedded in flexible, biocompatible sheets of polyurethane or Silastic, with 5–10 mm center-to-center distance. In comparison, SEEG electrode contacts are cylinders with 0.8–1.2 mm diameter, 1–3 mm length, and 5–10 mm inter-contact distance. While SDE rest on the cortical surface above pia, SEEG electrodes are implanted at an angle to the cortex along a carefully planned trajectory. Thus, it is possible with SEEG ESM that one contact of the stimulated pair may lie in gray matter and another in the white matter. Therefore, the geometry of current spread during SEEG ESM will have to incorporate differences in electrical properties of gray and white matter , pathologic excitation (AD’s and seizures), and inhibition (negative function). This has some regional specificity, for example, a majority of stimulations in the primary motor cortex result in activation-type behavior, while those in perisylvian language cortices are primarily inhibitory and are revealed when the patient is actively engaged in a linguistic task. There is evidence that stimulation at the same site can evoke both positive and negative responses , seizures were triggered in 35% of patients, with secondary generalization in 12% of seizures  SDE study that showed language response thresholds to be above AD thresholds throughout the included age range (1–26 years), while motor response thresholds were higher than AD thresholds below 8-years of age , left posterior superior temporal gyrus (STG), left anterior middle temporal gyrus (MTG), and bilateral premotor cortex and post-central gyrus , MTG, and amygdala , noxious , somatosensory , viscerosensory , and vestibular  has resulted in sensory , motor (various body parts), anticipatory (intention or urge to move), emotional , speech (arrest), and autonomic  responses , reported somatic motor responses in 138 (66%) and somatosensory responses in 32 (15%) patients respectively with SEEG ESM  to result in speech/language inhibition at 87/304 (29%) electrode contacts. SEEG ESM was a good classifier of anatomic language sites with high specificity (0.87) but limited sensitivity  was reported in 13/15 patients in one study (Hermann and Wyler, As far as chronic intracranial monitoring of DRE patients is concerned, the above studies are limited to SDE. A large-scale validation of SEEG ESM against post-operative language and neuropsychological outcomes remains an important unmet clinical need. It is also desirable to compare neuropsychological outcomes in cohorts of epilepsy surgery patients evaluated with SEEG vs. SDE, to identify subgroups where one intracranial modality may be preferable over another for ESM.This narrative review attests that SEEG is rapidly becoming the preferred modality for pre-surgical intracranial monitoring given its relative safety compared to SDE and avoidance of craniotomy . EvidencHowever, SEEG ESM requires a different clinical approach for interpretation compared to SDE ESM. While SDE affords surface contiguity and the ability to potentially map the extent of functional areas on the cortical surfaces, SEEG offers the ability to sample from areas typically inaccessible to SDE, including depth of sulci, medial and basal surfaces of cerebral hemispheres, and insula . At our Although early studies with SEEG ESM appear encouraging, several clinical and scientific questions remain unanswered. First, there is a need to better understand the physics of current propagation in the brain tissue after bipolar stimulation of SEEG contacts, which may sometimes lie respectively in white matter and gray matter (Koessler et al., We have mentioned that bipolar stimulation, at least with SDE, may result in the localized current spread. There is some evidence, based on studies of intraoperative motor evoked potentials, that bipolar stimulation may specifically limit current spread perpendicular to the cortical surface (Kombos and Suss, To better learn from clinical data, it will be important to develop relatively homogeneous protocols for SEEG ESM. An important consideration will be to develop a modular approach towards the selection of different language and cognitive tasks, particularly for pediatric ESM. Also, it may be desirable to routinely evaluate for interference with voluntary movements during ESM, to map for “negative” motor areas, which may require higher current strengths and sustained patient participation (Kanno et al., Finally, the most important unmet clinical need is to quantify the risk reduction in adverse post-operative outcomes achieved by pre-surgical SEEG ESM. The purpose of ESM is to help improve the safety of neurosurgical decisions, by offering a safe operative corridor between the seizure-onset zone and eloquent cortical regions. ESM can also help anticipate and prepare for post-operative deficits if there is an overlap between the seizure-onset zone and eloquent functional regions. With SDE, although earlier studies were somewhat discordant (Lendt et al., All authors participated in literature review, data extraction, and data interpretation. KG and SI drafted the manuscript that was critically reviewed and modified by RA. All authors contributed to the article and approved the submitted version.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.


Chronic Hepatitis B Virus (HBV) infection poses a significant global health burden. Although, effective treatment and vaccinations against HBV are available, challenges still exist, particularly in the development of curative therapies. The dynamic nature and unique features of HBV such as viral variants, integration of HBV DNA into host chromosomes, and extrahepatic reservoirs are considerations towards understanding the virus biology and developing improved anti-HBV treatments. In this review, we highlight the importance of these viral characteristics in the context of treatment and oncogenesis. Viral genotype and genetic variants can serve as important predictive factors for therapeutic response and outcomes in addition to oncogenic risk. HBV integration, particularly in coding genes, is implicated in the development of hepatocellular carcinoma. Furthermore, we will discuss emerging research that has identified various HBV nucleic acids and infection markers within extrahepatic sites (lymphoid cells). Intriguingly, the presence of hepatocellular carcinoma (HCC)-associated HBV variants and viral integration within the lymphoid cells may contribute towards the development of extrahepatic malignancies. Improved understanding of these HBV characteristics will enhance the development of a cure for chronic HBV infection. The Hepatitis B Virus (HBV) is a significant global viral pathogen. An estimated two billion individuals worldwide have been exposed to the virus with approximately 257 million living with chronic HBV infection (CHB) . HBV is The HBV is transmitted both horizontally and vertically into new human hosts. Horizontal transmission may occur through exposure to materials, such as blood or semen containing infectious HBV particles. However, horizontal transmission into adult immunocompetent hosts most frequently develops into a self-limiting acute infection with clearance of HBsAg and development of HBsAg antibodies (anti-HBs). CHB is defined by positive HBsAg in serum for greater than 6 months duration. The vast majority of CHB carriers are infected by transmission of the virus by mother-to-child transmission during childbirth or close contact with blood and body fluids of other family members in early childhood  [In this review, we will briefly discuss the natural history of CHB and the two main categories of therapeutics for CHB management . It is noteworthy that persistent HBV infection has unique viral aspects, which affect antiviral treatment choices as well as oncogenic risk. These viral features include HBV genotype/genetic variations, integration of HBV DNA into host chromosomes, and recent data suggesting role of viral lymphotropism. In addition, HBV genetic variants, integration, and lymphotropism will be discussed as a consideration in the development of new antiviral therapeutics.The natural history of CHB infection is complex and has been divided into distinct phases ,8,9. An Transition to the third stage occurs with the loss of viral HBeAg and the presence of antibodies targeting HBeAg (anti-HBe) . During Currently approved first-line antiviral therapies for CHB infection include pegylated-interferon alpha (PEG-IFNα) or potent NAs such as tenofovir disoproxil fumarate (TDF), tenofovir alafenamide (TAF), and entecavir (ETV). HBV is a weak inducer of innate immunity (type I IFNs), thereby evading efficient immune detection and elimination of the virus . Thus, tNAs inhibit the viral reverse transcriptase (RT) enzyme, an essential component in the viral life cycle, thereby attenuating production of new HBV particles. However, NAs do not directly target the HBV cccDNA and only a small minority of patients on therapy eventually develop HBsAg clearance (HBsAg negative/loss), which serves as a marker of viral suppression or functional cure ,26. TherCHB has a complex natural history, mediated by a dynamic interplay between the host immune response, susceptible host cells, and the virus. The outcome of HBV infections, response to treatment, and risk of HCC development, has been linked to viral heterogeneity. HBV genetic variants within the HBV preS1 or X/basal core promotor/pre-core (X/BCP/PC) regions are associated with treatment failure and varying risk of HCC. In addition, deletion of viral domains such as the HBV preS region may also contribute towards risks of HCC or recurrence of HCC, such as the recent reports by Teng et al.  HBV is cDue to the error-prone method of viral replication via the HBV polymerase, the HBV population within a host exists as quasi-species. Moreover, studies evaluating lymphoid cells ) in CHB carriers have reported different genotypes exist within the plasma and PBMCs ,55. ThesMutations in HBV have also been associated with resistance against NA therapy, especially first-generation NA, such as lamivudine . Most ofIn addition to influencing treatment response and outcomes, genetic variations within HBV are linked to HCC . Indeed,In addition to the preS mutations, genetic variants of HBV within the X/BCP/PC, have also been associated with an increased—and in some cases decreased—risk of developing cirrhosis and HCC. Some of the oncogenic variants in this region have been observed at higher frequencies in certain genotypes, which likely is reflected in the difference in HCC risks amongst HBV genotypes. For example, the double mutations A1762T and G1764A are more frequently observed in genotype C. Many variants in this region have been identified from large epidemiological studies generally from Asian populations . Most noAlterations in the HBx protein are associated with mutations within the X/BCP/PC region and can lead to HCC development. Due to the overlapping nature of the HBV genome, the mutations directly affect the genetic coding sequence of HBx. A research study by Yan and colleagues exploring the quadruple mutant of A1762T/G1764A/T1753A/T1768A showed an overall downregulation of p53 in comparison to wild-type HBV X . In addiIntegration of HBV DNA into the host genome arises with the incorporation of double stranded linear (dsl) variants of HBV . An estiIntegration of HBV is thought to occur at random sites and has been detected in a wide variety of genes, but preferential sites for HBV integration include host genomic regions prone to dsDNA breaks or fragile sites largely due to the use of NHEJ and MMEJ mechanism . FurtherHBV is a hepatotropic virus that infects and establishes reservoirs in hepatocytes. Studies in the woodchuck hepatitis virus (WHV) model of HBV show that WHV is also a lymphotropic virus ,113,114.The presence of HBV within the lymphoid cells may also contribute towards the development of hematological neoplasms. Indeed, a number of epidemiological studies have reported associations of CHB with higher risks of non-Hodgkin lymphoma, specifically diffuse large B-cell lymphoma (DLBCL) ,135,136.Despite, the recent advances in our understanding of HBV lymphotropism, numerous outstanding questions remain warranting additional research. Namely, the process of viral entry and the corresponding cellular receptor utilized for lymphoid cell infection remains elusive. Likely the HBV surface proteins mediate the interaction with a currently unknown host receptor. An intriguing possibility are the B-cell antigen receptors, which are specific for HBV surface proteins might serve as the mechanisms of lymphoid cell entry for HBV. Alternatively, non-specific receptors present on phagocytes may serve as a method of permitting HBV entry through the processes of phagocytosis, micropinocytosis, or endocytosis . These mUtilization of the woodchuck model and WHV could also serve to contribute towards a better understanding of hepadnaviridae lymphotropism including mechanism of viral entry, host cell restriction factors, and host factors beneficial towards viral persistence or infection. However, it is important to note that many aspects of WHV biology remains unclear including the entry mechanism into woodchuck hepatocytes. Another feature of this animal model, which is important to consider is the perceived increased lymphotropic nature of WHV in comparison to HBV. Potentially there exists certain host or viral factors, which are more permissible for WHV replication within the lymphoid cells of woodchucks. In line with this possibility, a prior study by Jin et al. have demonstrated that the WHV surface proteins, and more specifically the preS1 domain, was more efficient in interacting with woodchuck lymphoid cells in comparison to hepatocytes . This inhttps://www.hepb.org/treatment-and-management/drug-watch/ for more) [A wide variety of novel therapeutics are under development for CHB infection, hoping to achieve a functional (HBsAg loss) and/or sterilizing cure (clearance of HBV cccDNA). These include capsid assembly inhibitors, HBV entry inhibitors, and immunotherapies, such as checkpoint blockade inhibitors and RIG-1 agonists (see or more) . An impoDue to the nature of HBV integration and HBV cccDNA persistence, a sterilizing cure that eliminates all viral genomic material from infected hosts is extremely challenging. Instead, current and developing antiviral therapies focuses on achieving a “functional cure” in which viral activity is suppressed, transcriptional silencing of HBV cccDNA, with seroconversion of HBsAg  susceptible to WHV, is a highly valuable animal model for human HBV infection with closely related hepadnaviral infection. Numerous studies have demonstrated the lymphotropic nature of WHV, which can replicate and produce infectious virions within the woodchuck lymphatic system [HBV lymphotropism is an intriguing consideration in the natural history of HBV infection, particularly if lymphoid cells may serve as a viral reservoir capable of producing infectious HBV. Most pre-clinical studies of HBV therapeutics involve the in vitro use of immortalized cell lines  with and/or without the HBV entry receptor, sodium taurocholate cotransporting polypeptide (NTCP), as well as in vivo murine models  with humanized liver. However, it may be of interest to assess in vitro or in vivo systems for the effect of developing therapies on hepadnaviral infection within the lymphoid reservoir. The murine HBV models with humanized liver usually have defective immune systems and cells to allow for growth of xenograft liver tissue  and contc system ,113,114.In summary, there has been rapid development of direct acting antivirals and host targeting novel HBV agents. Increased understanding and development of tools to study the complex virology of HBV and the dynamic interplay with the host immune response is needed to ultimately achieve a HBV cure. Viral genetic variations can impact therapeutic development, such as refining the selection and monitoring of potential treatment responders. The role of HBV lymphoid reservoirs as a source of liver cell re-infection, especially in OBI, and extrahepatic complications remains controversial. Moreover, even patients who achieve a functional cure (HBsAg clearance) late in life, may harbor OBI and remain at risk for HCC and overt HBV reactivation with potent immunosuppression.


Tendons are collagenous musculoskeletal tissues that connect muscles to bones and transfer the forces necessary for movement. Tendons are susceptible to injury and heal poorly, with long-term loss of function. Mesenchymal stem cell (MSC)-based therapies are a promising approach for treating tendon injuries but are challenged by the difficulties of controlling stem cell fate and of generating homogenous populations of stem cells optimized for tenogenesis (differentiation toward tendon). To address this issue, we aim to explore methods that can be used to identify and ultimately separate tenogenically differentiated MSCs from non-tenogenically differentiated MSCs. In this study, baseline and tenogenically differentiating murine MSCs were characterized for dielectric properties (conductivity and permittivity) of their outer membrane and cytoplasm using a dielectrophoretic (DEP) crossover technique. Experimental results showed that unique dielectric properties distinguished tenogenically differentiating MSCs from controls after three days of tenogenic induction. A single shell model was used to quantify the dielectric properties and determine membrane and cytoplasm conductivity and permittivity. Together, cell responses at the crossover frequency, cell morphology, and shell models showed that changes potentially indicative of early tenogenesis could be detected in the dielectric properties of MSCs as early as three days into differentiation. Differences in dielectric properties with tenogenesis indicate that the DEP-based label-free separation of tenogenically differentiating cells is possible and avoids the complications of current label-dependent flow cytometry-based separation techniques. Overall, this work illustrates the potential of DEP to generate homogeneous populations of differentiated stem cells for applications in tissue engineering and regenerative medicine. Mesenchymal stem cells (MSCs) are multipotent cells that can self-renew and differentiate into various cell lineages such as adipocytes , chondroMSCs have also been explored in tissue engineering and regenerative approaches for treating musculoskeletal tissue injuries, including tendon injuries ,23,24,25Current stem cell separation techniques can be classified into two categories: techniques based on physical parameters such as size and density  and techniques based on affinity  such as fluorescence-activated cell sorting (FACS)  and magnThis article demonstrates the use of dielectrophoresis (DEP), an electrokinetic technique, to identify the unique dielectric properties of tenogenically differentiating MSCs from larger cell populations in a label-free way. DEP employs non-uniform electric fields and exploits the effects of the electric fields on cellular motion to characterize and separate them. DEP-based sorters are simple, cost-effective, label-free, accurate, and efficient, overcoming the limitations of current commercial stem cell separation methods. DEP was first used in stem cell research in the 1990s ,37,38 anThe work presented here is the primary step toward developing DEP as a novel, label-free sorting technique for baseline  and tenogenically differentiating MSCs, based on the dielectric characterization of both the cell membrane and cytoplasm at different stages of early differentiation. Stem cell therapy is seen as a potential method to heal tendon injuries and is capable of being clinically translated. However, due to the limited understanding of tenogenesis and post-culture processing limitations, clinical translation had been delayed for many years . Hence, DEP is the force observed acting on dielectric particles subjected to a non-uniform alternating current (AC) electric field due to the difference in the polarizability of the medium and the particles ,42. For zability ,43. Furtlsewhere ,45. In td is the thickness of the membrane, and the subscripts mem and cp refer to the cell membrane and cytoplasm, respectively.Stem cells’ cytoplasm and its contents, i.e., nucleus, DNA, organelles, etc., are considered one homogenous sphere surrounded by a plasma membrane to reduce complexity . For a sDEP force is dependent on the frequency of the applied electric field. As frequency is tuned by maintaining a fixed peak-to-peak voltage, cells exhibit distinct behavior based on their polarizability. When the cell’s polarizability is greater than the polarizability of the medium in which it is suspended, the cell is attracted toward the high field electrode; this is termed as positive dielectrophoresis (pDEP). When the cell’s polarizability is less than that of the medium, the cell moves away from the high field electrode, thus experiencing a force termed as negative dielectrophoresis (nDEP) . There eysiology . The higy medium , where cium  values . Figure To compare the accuracy of the theoretical model, the following plots  are incl9 cells) using at least four passages at 150,000 cells/h of sorting throughput per passage [Although prolonged exposure to electric fields affects cell viability, i.e., within the frequency range of 0.01–1 MHz for a prolonged duration (5–30 min) , shorter passage . Recent  passage ,68. TakeThis study has some limitations. While tenogenic initiation was evaluated based on changes in cell morphology that match those observed in prior studies ,69, prodFinally, this study did not directly compare an affinity-based sorting method, such as FACS or MACS, with DEP. As our goal was to establish the potential of using DEP as a future sorting technique for tenogenically differentiating MSCs, direct comparison was outside the scope of this study. Future work will use the DEP parameters established in this study to quantify the potential advantages of a DEP-based microfluidic sorting device over FACS or MACS for selecting MSCs with the highest tenogenic potential.Our results using a point-and-planar electrode DEP microwell device confirm the need for further exploration. Future studies based on these findings will develop a DEP-based microfluidic sorting device to isolate and enrich populations of tenogenically differentiating MSCs at 3 d and then explore impacts of DEP purification on tenogenic markers (scleraxis and tenomodulin) in longer-term culture. Further studies in vitro and in vivo are required to characterize cell viability following DEP and initial tenogenesis and later stages, when fully differentiated into tendon cells. Future studies are also needed to better understand the electrophysiology associated with changes in the cytoplasm and membrane throughout tenogenesis. For potential clinical translation, the dielectric properties of human primary MSCs undergoing tenogenesis will be evaluated in future studies.DEP has the potential to be developed into a label-free separation technique that can enrich and isolate stem cells effectively and enhance their efficacy for treating injuries and diseases. The distinct dielectric properties of murine MSCs identified in this study reveal their biophysical identities, which can be used to separate cells based on minute differences in their intrinsic electrical properties. Specifically, this study identified a difference in the membrane dielectric properties between day 3–no treatment (undifferentiated control) MSCs and day 3 tenogenically differentiating MSCs treated with TGFβ2. This study represents a significant contribution to DEP ultra-high frequency cytoplasmic characterization of MSCs. Since the higher frequency ranges are not easily accessible, the DEP second crossover regime remains largely unexplored. However, using DEP higher crossover frequency characterizations, cytoplasmic changes can be identified and further studied to enhance understanding of the subsequent changes within the cell nucleus and its content.Taken together, this study characterized MSCs and their tenogenically differentiating progeny to obtain the dielectric properties. The results and techniques described can be expanded to develop a stem cell sorter for the efficient sorting of differentiating/differentiated MSCs from non-viable cells and undifferentiated cells in a label-free and inexpensive way. The experiments demonstrated a significant difference in the dielectric properties between treatment groups, which further needs to be compared with another characterization technique other than dielectrophoresis, such as marker-based assay, cytometry, for further scale-up and viability studies. Ultimately, stem cell sorting by DEP has the potential for clinical applications because it can improve the homogeneity of stem cell populations and reduce the potential for aberrant tissue formation . Further studies will continue to develop DEP-based-stem cell sorting and scale it up to the cell numbers needed for regenerative therapies, transplantation, or engineered organs and tissues.


This Research Topic received contributions through two fields: Frontiers in Pharmacology and Frontiers in Neuroscience. We would like to thank all the authors who made possible the success of this topic with their contributions, which give us a glimpse of how productive and diversified is the basic research in neuropharmacology, targeted to drug discovery.Balbinot and Schuch) examines neuromodulatory systems involved in stroke recovery before, during or after rehabilitation and propose them as targets for novel drug treatments. Recovery from ischemic stroke relies on neuronal plasticity; in particular, cortical and striatal cellular mechanisms underlying motor learning also affect post-stroke compensatory relearning. Another review  examines immunomodulatory therapeutic approaches to reduce neurotoxicity and/or to promote neurorestoration and tissue repair. Drugs targeting innate immunity , are likely to counteract neuronal injury in the acute phase, while drugs targeting the adaptive immune response (regulatory T and B cells), are more suitable to affect the repair processes, and might be used over a longer therapeutic window. Furthermore, the observation that ischemic stroke itself induces alterations in immunity, potentially responsible for post-stroke dysbiosis and gut-induced neuroinflammation, points to immunomodulatory therapeutic strategies to counteract mechanisms out of central nervous system (CNS), capable of impacting on stroke outcome. Two experimental papers propose novel potential targets for vascular-dependent brain disorders; one points to the adiponectin receptor, showing that adiponectin and an adiponectin receptor agonist exert neuroprotective effects against oxygen/glucose deprivation , while the other points to endothelial progenitor cell-mediated angiogenesis after cerebral ischemia–reperfusion, a process stimulated by dichloroacetate . Obviously, both preclinical models need further validation, but at least they provide novel insights in the pathophysiology of brain ischemia.A first group of papers focused on stroke, neuroprotection, and recovery. Until recently, many experimental paradigms have tested the neuroprotective effects of treatments carried before the ischemic insult. However, though helpful in elucidating pathophysiological mechanisms, these studies provided very little hints for human therapy, because stroke patients are commonly seen and treated after the occurrence of brain ischemia. Thus, therapeutic strategies aiming at improving recovery might realistically have more translational potential. A review . The impact of drug treatments on cognition and memory relies on animal paradigms for drug testing, i.e. experimental models which provide functional  data predictive of human outcomes. Clinical developing treatments for AD requires the identification of biomarkers to identify an ongoing AD process before clinical presentation, refine clinical trial design and set meaningful endpoints. One perspective paper  examines the potential of exploiting “liquid biopsies,” e.g. neural exosome proteins and/or miRNAs. The significance of circulating miRNAs in sporadic AD needs further clarification, which may not only provide novel biomarkers but also offer new miRNA-targeted therapies. Based on data suggesting that antidepressants reduce the risk to develop AD and may even exert neuroprotective effects in AD, an experimental research paper  further explores the connection between AD and depression, testing the hypothesis that fluoxetine and vortioxetine may prevent memory deficits and depressive-like phenotype induced by intracerebroventricular injection of beta amyloid. The results indicate that fluoxetine and vortioxetine can prevent both cognitive deficits and depressive-like phenotype in this model, an effect that might be related to transforming growth factor β1 (TGF-β1). Improving cognitive functions, particularly those related to memory mechanisms, including long-term potentiation and long-term depression (LTD), is one of the approaches in drug discovery for neurodegenerative disorders. An original paper (Mango and Nistico) investigates the role of acid-sensing ion channel 1a in synaptic plasticity and demonstrates, in the LTD paradigm in mouse hippocampus, an interplay between them and glutamate N-methyl-d-aspartate receptors. These channels may become a therapeutic target for improving cognitive functions in neurodegenerative disorders. A review  examines the enzymes and receptors involved in sphingosine-1-phopshate production as potential drug target for different neurodegenerative diseases. Starting from the approved use of fingolimod in multiple sclerosis, the authors proceed to Alzheimer, Parkinson, and Huntington diseases. Besides some common mechanisms related to neuroinflammation, the authors consider specific genetic conditions in sphingolipid metabolism, where mutations of enzymes are responsible for pathological phenotypes, suggesting that they may serve as druggable targets. An original article examines the therapeutic potential of extracellular vesicles derived from mesenchymal stem cells in spinal cord injury . The results are encouraging, showing an improvement of blood-spinal cord barrier, with reduction of its permeability, as well as a neural protection. The study of extracellular vesicles as therapeutic agents has seen growing efforts in recent years, not only for their potential in CNS diseases, but also for other organs and systems. The translation of such experimental data, however, requires not only validation in human studies, but also to address problems related to large scale production, batch to batch reproducibility, and standards of quality. A mini review examines the role of microglia in the defense against brain tumors, in particular glioblastoma multiforme . The novel idea here is to target two-pore domain potassium channel expressed by microglia to modulate its motility (production of processes) and its release of cytokines, particularly IL-1beta.Another group of papers focus on neurodegenerative diseases, particularly Alzheimer disease (AD), and neuroinflammation. Despite intense efforts to understand the cellular and molecular mechanisms leading to neurodegeneration, disease modifying drugs for AD are still unavailable. One paper points to the usefulness of current animal models of AD, particularly discussing the translational potential of transgenic mice and transgenic rats . Bumetanide may lower cytosolic Cl− which facilitate GABA-induced hyperpolarization; based on this grounds, bumetanide has been studied in both preclinical and clinical settings, and seems promising for temporal lobe epilepsy, autism, and schizophrenia. The other paper is an original article testing the hypothesis that tribbles pseudokinase 3 (TRIB3) plays a key role in seizures and neuronal apoptosis . By using a kainic acid rat seizure model, the authors were able to demonstrate that TRIB3 upregulation inhibits AKT and induces neuronal apoptosis. They conclude that TRIB3 may represent a potential pharmacological target for the treatment of epilepsy.Two papers regard epilepsy. One is a review on the potential repurposing of bumetanide, a loop diuretic, related to its interaction with sodium–potassium–chloride (Na–K–Cl) cotransporters in neurons . Insula is a region of cerebral cortex recently implicated in several critical mechanisms of addiction. Originally studied for nicotine addiction, for which more data are available, recently insula has been also involved in other substance use disorders, including alcohol, opiates, cannabis. The authors not only review the role of insula, but also examine and discuss a recent technique, transcranial magnetic stimulation, which may offer potential benefits in addiction treatment. Two original articles provide novel insights into the therapeutic potential of cannabinoids. One paper examines the effect of systemic or intra-hippocampal administration of cannabidiol on hyperactivity shown by Gria1−/−, a mouse line deficient in AMPA-type glutamate receptor GluA1 subunit, and found that it is effective in dampening the activity of hyper excitable hippocampus . The role of selective inhibition of the dorsal hippocampal principal neurons in Gria1−/− mice was confirmed by inhibitory designer receptors activated by designer drug (DREADD). This paper suggests that cannabidiol holds potential for treating syndromes with hyper excitable hippocampus. The other paper explores the impact of pharmacological inhibition of the fatty acid amide hydrolase (FAAH), which increases endogenous levels of arachidonylethanolamide (anandamide), on cognitive functions. The authors provide evidence of attention enhancement in adolescent mice following FAAH inhibition . This finding supports further studies on FAAH inhibitors in human conditions, such attention-deficit/hyperactivity disorder (ADHD), where cannabis use as automedication provides some relief, but produces also adverse reactions. A brief research report examines the effects of non-competitive (receptor-inactivating) antagonists of kappa opioid receptors . The activation of these receptors has been related to anxiogenic, dysphoric, and cognitive disrupting effects of repeated stress, suggesting that their antagonists could be used for treating some stress-related disorders. Norbinaltorphimine produces cumulative kappa opioid receptor inactivation, at doses much lower of those required for achieving acute effective antagonism. Such a mechanism of cumulative inactivation may improve safety, selectivity, and clinical efficacy of kappa antagonism, which may be exploited for treating stress-related conditions, including anxiety, depression, and addiction.A group of papers deal with addiction and addiction-related substances  which hold therapeutic potential. One review focus on the role of the insula in addiction (Geerts and Barrett), proposing a computer model of biological processes, informed by preclinical and clinical data, which could be used as a tool to integrate a large amount of data to address key points in pharmacodynamics (PD), pharmacokinetics (PK), and PD–PK interactions and profiles. This kind of platform, named Quantitative Systems Pharmacology (QSP), aims at modeling, in silico, brain circuitry relevant for specific diseases and/or symptoms, to improve the success rate of CNS drug discovery programs, reduce cost and animal use, increase the speed of the processes. While this paper deals with the general paradigm of CNS drug discovery, two others examine the need of appropriate models for specific neuropsychiatric conditions. One specifically examines the conditions that should be fulfilled by preclinical models of post-traumatic stress disorder (PTSD), which should take into account and try to reproduce in the animal model the symptoms as classified for humans in Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) . Interestingly, the currently available criterions for human PTSD are consistent with impairment of dopaminergic mechanisms and points to potential dopaminergic-based pharmacotherapies for PTSD to address a yet unmet medical need. Another paper deals with a preclinical model of anorexia nervosa, the activity-based anorexia, where rodents are tested for their preference for feeding over performing exercise . This study reports sex-related differences in the preference for exercise over feeding in fed animals, but sex-independent preference for feeding in food-restricted animals. The authors conclude that this model is not adequate to discriminate and quantify running and feeding drives, which are critically affected in anorexia, and should be considered when testing experimental drug treatments.An interesting paradigm shift in drug discovery for CNS drugs is illustrated in a theoretical paper  models and/or critically re-examine the available ones. The validation of preclinical models is an absolute requirement to effectively test experimental hypothesis that may allow us to translate novel drug treatments in clinical settings.SS is the sole author of this editorial. He conceived and wrote this manuscript.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


Recently, racial and ethnic disparities within the current coronavirus disease-2019 (COVID-19) pandemic at the state level have received attention and notably highlight the ongoing issues surrounding health disparities within the United States. Among the discussions around health disparities lies a discussion on the role of psychosocial stress during this pandemic, especially with broadly applied social distancing and isolation recommendations. In nonpandemic times, psychosocial stressors have a significant association with physiological responses and behavioral responses. Within the current pandemic, increased attention on health-promoting behaviors, such as cooking and physical activity, has occurred. However, based on disparities from structural racism and socioeconomic effects on neighborhood environments, we may see a limiting value to the possible mitigating role of health behaviors within some disparate communities. We present in this perspective that there may be a role for behavioral interventions to mitigate psychosocial stressors and promote health behaviors. It may also be important to consider the use of multilevel behavioral interventions designed in the context of environmental and perceptual barriers during the COIVD-19 pandemic. Reasons for the disparity in COVID-19 affecting African Americans are likely multifactorial, including structural inequities and social injustice, misinformation about infection risk, limited testing availability and health care access, and disproportionate prevalence of preexisting conditions.Early data at the state level show that disparities within the case and mortality rate from coronavirus disease-2019 (COVID-19) likely exist and disproportionately affect African Americans.2 However, examining the expected disparity among African Americans may shed light on the role of health and socioeconomic inequities as well as identify areas for mitigating the devastating effects of COVID-19 on communities of color. It is important to note that calls for attention to health inequities affecting COVID-19 cases are not limited to the United States as similar concerns have been expressed within China.3 In addition, racial/ethnic minorities being disproportionately affected by pandemics are not unique to COVID-19, as during the 2009 H1N1 pandemic, hospitalization rates among minority groups were consistently disproportionate.4The downstream effects of the disparity, however, may be long lasting within the African American community beyond when the pandemic subsides and may mirror health consequences of known social determinants of health. African Americans are not the only racial/ethnic minority community in the United States that may become disproportionately affected by COVID-19.5 Psychosocial studies from the prior severe acute respiratory syndrome (SARS) outbreak between 2002 and 2004 in China showed disparities in psychosocial effects of that pandemic based on socioeconomic status.6 A unique factor that may lead to psychosocial disturbance from this pandemic versus others, such as Ebola, is that for COVID-19, it is difficult and challenging to detect and distinguish the infection from benign conditions. This may place additional psychosocial stress on individuals because social isolating recommendations such as distancing or self-quarantining may be more broadly applied.As seen in other pandemics within the past century, the current pandemic COVID-19 can create great psychosocial difficulties for affected individuals. Research from prior pandemics has found a wide range of psychosocial impacts, including feelings of helplessness and stigmatization, with negative emotions compounded with the closures of schools and businesses.8 For those studies that have occurred, attention has rightfully focused on the effect of psychological stressors on preventive or infection-related behaviors. In addition, less attention has been given to the role of health-promoting behaviors during pandemics.Most pandemics in the past century have received limited study by behavioral scientists.9 has led to a historical legacy of African Americans being the recipients of prejudicial, discriminatory, and racially based exclusionary practices. The ultimate culmination of these practices has led to many African Americans having life experiences rooted in racial injustice at individual, structural, and institutional levels. The consequences of these racial injustice experiences may impact and constrain health. Experiences with receiving care that is driven by implicit racial biases, explicit use of race in medical decision making, or perceptions of differential health care services have led to significant barriers surrounding trust when it comes to interactions in health care settings.10–12 Also, repeated exposure to microaggressions, discrimination, and racist practices, especially those of social exclusion, can stimulate physiological stress responses that, when occurring daily, or when occurring in an unpredictable pattern, can be akin to chronic stressors.In the United States, the biased social construct of race13 Consequences of these neighborhood environments can directly impact physical and mental health: less access to foods identified to prevent chronic diseases,14 increased exposure to violence,16 and less access to green space,17 a known mitigating factor of psychosocial stress. As a result, chronic physiological, psychosocial, and environmental stressors may overburden African Americans and, in an inequitable manner, influence poorer health outcomes.In addition, discriminatory and exclusionary practices have led to significant racial differences and inequities. Predominately, African American communities have fewer economic opportunities, including less home ownership and a disproportionate poverty concentration.19 Specifically in relation to COVID-19, interleukin-6 (IL-6), an inflammatory cytokine associated with chronic stress and with demonstrated racial/ethnic differences, appears to be a key mechanism involved in COVID-19 disease severity. In particular, an association between the sympathetic nervous system hormone adrenaline and IL-6 is found in conditions with increased COVID-19 mortality and underlying chronic diseases disproportionately found among African Americans, including cardiovascular disease,20 diabetes,21 and hypertension.22 Novel or unique stressors, as may be experienced during a pandemic, can lead to exaggerated sympathetic responses.23 Therefore, there may be a key reason to examine a role for psychosocial factors related to African Americans during this pandemic.Furthermore, immune responses to adverse psychosocial and environmental conditions may contribute to an increased risk of COVID-19 morbidity and mortality among African Americans.24–26 Hence these behaviors may help to restore some biological and psychological mechanisms negatively affected by psychosocial stress. But engagement in these behaviors may be encouraged or hindered by psychosocial stressors during a pandemic. In fact, a recent web-based survey involving the general population in China found a significant association with anxiety around COVID-19 and sleep disturbances.27 Since the start of the COVID-19 pandemic, two health-promoting behaviors have received specific attention: cooking and physical activity. Although there is emerging interest on the role of cooking in psychosocial health,28 in particular, physical activity may lead to positive effects on lowering IL-6 levels29 and on immunity and inflammation even in non-COVID-19 viral respiratory infections.30 Examination of reports on these and other COVID-19–related health behaviors may provide areas of investigation that are key to understanding the impact of this pandemic on health-promoting behaviors. For example, are socioeconomic factors, time availability, or psychosocial factors driving or limiting participation in healthy behaviors during the COVID-19 outbreak? What is the significance of having a history of health-promoting behavior before the COVID-19 pandemic? Do motivation and self-efficacy play a role in engagement in the healthy behavior during prolonged social distancing? And are interpersonal psychosocial changes occurring as a result of either starting or increasing the behavior? Most importantly, once the COVID-19 social restrictions are lifted, will this health-promoting behavior be maintained or cease, and what are the significant social determinants of such actions?As already stated, a key consideration within the pandemic is the role of health behaviors and how they impact psychosocial health. Health-promoting behaviors, those behaviors actively done by an individual for maintenance or improvement of one's health or to maintain a healthy lifestyle, typically include physical activity, sleep, and dietary behaviors. In nonpandemic situations, psychosocial factors are noted to have a significant association with health-promoting behaviors through physiological  and behavioral responses.31 These factors included social support, social exclusion, and psychological stress. This connection provides a context for understanding the importance of targeting different areas that influence psychosocial health and related health behaviors. We suggest work is urgently needed to not only elucidate mechanisms by which these psychosocial factors may be influenced by other social determinants such as an individual's physical environment, but also to develop interventions that might effectively reduce psychosocial stressors during the COVID-19 pandemic for the most vulnerable populations. For example, mindfulness-based stress-reduction interventions are shown to decrease blood pressure readings among low-income African American adults.32 And intervention studies shown to increase self-compassion33 and increase social cohesion34 may lead to decreased IL-6 levels. Notably, social cohesion and activities that promote such cohesion, including engaging in church services, are recognized psychosocial coping factors among African Americans,36 even within the context of psychosocially stressful events.37 Thus, these intervention approaches may allow for the leveraging of existing coping skills and resilience factors in African American communities. The use of sociocultural resilience skills may lead to compounded benefits through reinforcing a positive collective identity. The resultant social capital from this may help to propagate further the use of these skills among individuals.Identifying the role of COVID-19 on health behaviors could be especially important for certain populations that are affected by health disparities, such as African Americans. As COVID-19–related social distancing and quarantining conditions may influence involvement in health behaviors, there may be a limit to engaging in these behaviors among these communities due to known social determinants of health, such as type of employment, food access, and perceived or objective neighborhood environment conditions. Recognizing the connection of psychosocial experiences to broader social and environmental conditions, in 2005, the WHO Commission on Social Determinants of Health recognized psychosocial factors as social determinants to health outcomes.38 These interventions are uniquely effective at addressing minority health and disparities by providing interventions based on the interconnected levels involved in creating disparities. Examples of how multilevel interventions may be useful during this pandemic to address psychosocial health and health-promoting behaviors may include health communication and messaging interventions ; promotion and identification of locations within an area to engage in social distancing physical activities (neighborhood levels); family-based interventions around instrumental or emotional support ; and psychological interventions on perception and self-awareness of behaviors . Disciplines involved in these interventions may include health behavior research, positive psychology, and social science. Lastly leveraging technology, especially accessibility of smartphone-based platforms, may help to advance the use of multilevel interventions during the current pandemic.Multilevel interventions based on socioecological models including levels for institutional/policy, neighborhood, interpersonal relationships, and individual factors may be especially important to consider.In conclusion, to strategically and effectively address health disparity outcomes during the COVID-19 pandemic will require local, state, and federal public health resources with focused health behavior and public health research to address issues related to specific risks among communities of color, specifically African Americans. We suggest that deliberate and timely attention to psychosocial health among African Americans during the pandemic may also offer opportunities to mitigate expected disproportionate effects of COVID-19, may help to highlight the role of certain environmental factors on psychosocial health, and may additionally introduce novel health-promoting strategies to individuals, families, and their communities.