Introduction: Revision total hip arthroplasty in the setting of acetabular bone loss remains a challenging clinical entity. Deficiencies of the acetabular rim, walls, and/or columns may limit the bony surface area and initial acetabular construct stability necessary for osseointegration of cementless components. Press-fit acetabular components with supplemental acetabular screw fixation represent a common technique aimed to minimize implant micromotion and allow for definitive osseointegration. Although acetabular screw fixation is commonly practiced in revision hip arthroplasty, few studies to date have examined the screw properties associated with maximal acetabular construct stability. The purpose of the present report is to examine acetabular screw fixation in a pelvis model mimicking Paprosky IIB acetabular bone loss.Methods: Measuring bone-implant interface micromotion as a surrogate for initial implant stability, experimental models assessed the effect of screw number, screw length, and screw position on construct stability subject to a cyclic loading protocol designed to replicate joint reaction forces of two common daily activities.Results: Trends towards increasing stability were demonstrated with increasing screw number, increasing screw length, and concentrating screws in the supra-acetabular dome. All experimental constructs yielded micromotion levels sufficient for bone ingrowth, except when screws in the dome were moved to the pubis and ischium.Conclusions: When using a porous coated revision acetabular implant to treat Paprosky IIB defects, screws should be used, and furthermore, increasing number, length, and position within the acetabular dome may help further stabilize the construct. Porous-coated total hip acetabular components offer the advantage of stable, long-term fixation in primary and revision total hip arthroplasty. Osseointegration, the process of host subchondral bone incorporating into a porous metal surface, is required to establish enduring fixation of cementless acetabular implants. Successful osseointegration demands both intimate contact of the porous acetabular implant surface with host bone of sufficient quality and quantity as well as initial acetabular implant stability historically defined as micromotion of less than 150 µm . AcetabuUnfortunately, the use of supplemental acetabular screw fixation in the setting of acetabular bone loss does not eliminate aseptic cup loosening from the aftermath of surgery. This persistent threat of mechanical acetabular failure motivates orthopaedic surgeons to think critically about screw placement during the time of revision arthroplasty in order to optimize initial implant stability. The Paprosky type IIB acetabular defect, characterized by substantial loss of the superolateral acetabular rim with intact and supportive acetabular columns, is considered the most common yet severe bone defect in which an uncemented revision acetabular component can be utilized with strictly acetabular screw supplemental fixation . In an eIn this study, we used Sawbones fourth Generation Composite hemi-pelvis models  that were fashioned to simulate acetabular bone loss consistent with Paprosky type IIB acetabular defects. Models were created by sequentially over reaming the acetabulum, and removing the posterior-superior aspect of the acetabular rim with a sagittal saw Figure . A revisA two-by-two grid was drawn in the acetabular cavity using anatomic landmarks to map screw position safe zones Figure . Screw pHemi-pelvis specimens were then mounted into a linear load cell  using two custom machined mounts that were each fabricated to simulate an applied force vector consistent with previously defined joint reaction forces for two common daily activities: walking on flat ground, and descending stairs Figure . These fThe primary endpoint, micromotion at the bone-implant interface, was measured using a motion capture system  with a manufacturer’s reported precision of 5-10 mm. Motion capture reference markers were positioned on the rim of the component and on the acetabular bone to determine motion of the component in three planes: posterolateral rotation (XY) into the rim defect, anteromedial rotation (YZ), and horizontal rotation (XZ) around the rim equator of the component. Displacement over time was recorded in these three planes of motion using a custom MatLab equation, and force-displacement curves were created. After determining the displacement per load cycle in each of the three defined planes of motion, the total motion of a point on the spherical surface of the implant was estimated using a calculation for motion of a point on a sphere.Experimental specimens were divided into groups based on three screw variables: number, length, and position. Additionally, a control group in which no screws were implanted was created to assess motion without screw supplementation. Screw number was varied between two, three, and four 25 mm length screws in the supra-acetabular position. Screw length was varied utilizing two screws of 25- and 50-mm lengths used in the supra-acetabular position. Screw position was varied between three screws used in supra-acetabular, anterior (pubic), and posterior  positions. Three specimens were tested in each control and experimental group. Micromotion per load cycle was recorded in each plane of motion, and from these measurements, the total motion was calculated for each specimen.ANOVA comparative statistics were then run between each control and experimental group to establish statistical significance between differences in displacement, with a p<0.05. As previously defined and referenced in several studies, a threshold of >150 µm of motion was established as the point over which, fibrous ingrowth would be expected. A priori power analysis was not performed as no study has been published using this method of measurement of micromotion on the surface of an acetabular component, and therefore benchmark effect sizes are not available.With three specimens in each control and experimental group, a total of 36 models were tested. Table There was a trend towards decreased cup motion as screw number increased. This trend was observed in both the XY plane of motion and when total motion was calculated Figure ; howeverThere was a trend towards increased cup motion when screws were moved from the supra-acetabular position to either an anterior or posterior position. Again, this trend was observed in both the XY plane of motion and when total motion was calculated Figure . This trThere was a trend towards decreased cup motion as screw length was increased. In general, this trend was observed in both the XY plane and total motion; however, there was an unusually high average motion in the group with a 50 mm screw designated A and 25 mm screw designated P in the YZ plane, and this led to a higher total calculated motion in this group Figure . Once agWhile the trends observed in the experimental groups were not statistically significant between the experimental groups, there was a statistically significant decrease in micromotion from the control group with no screws to each of the experimental screw groups.Stable arthroplasty component fixation is paramount for the long-term survivorship of cementless implants in primary and revision hip arthroplasty. During hip arthroplasty, the absence of supportive acetabular bone secondary to osteolysis, overaggressive acetabular reaming, dysplastic acetabular morphology, previous acetabular fracture, and/or advanced avascular necrosis may jeopardize the surgeon’s ability to achieve stable non-augmented acetabular fixation. When full intrinsic stability of the acetabular shell cannot be obtained, options for supplemental fixation include acetabular screws, porous metal augments, allograft/autograft bone, cement, reconstruction cages, and custom triflange devices. Utilization of increasingly sophisticated reconstruction devices is not only costly but frequently requires larger surgical exposures and increased operative times, two variables that are undoubtedly associated with an increased risk of periprosthetic joint infection. Thus, multi-hole acetabular shells in combination with acetabular screws remain an attractive technique within the surgeon armamentarium. A paucity of objective evidence exists to guide surgeon placement of acetabular screws. Several previous studies have demonstrated the long-term reliability of porous coated implants using a press-fit technique and supplemental screw fixation in the revision setting as an alternative to implants with pegs, spikes, and dual geometries ,8-11. InIn this study, we were able to identify trends in decreasing micromotion, and therefore, increased initial stability of a cementless component with increasing screw length, screw number, and concentrating screws in a superior location within the acetabulum. Changing screw position , led to a decrease in stability, despite prior evidence to suggest that screw divergence can increase construct stability . Given oThe threshold of micromotion, which allows for ossoeintegration of the porous coated implant, varies by published historical report. In one of the earliest studies, Pilliar et al., evaluated the effect of micromotion on ingrowth of porous metal in a linear displacement model. This nascent report demonstrated that excess movement (>150 µm) results in fibrous ingrowth rather than bone ingrowth . ConsequSeveral weaknesses of our report are acknowledged. First, we elected to use sawbones models, as opposed to cadaveric specimens, in an effort to maximize the number of specimens and standardize experimental groups. While the biomechanical composite Sawbones models may provide a basis for better understanding bone implant interactions, sawbones models fail to replicate the pathologic state of acetabular bone frequently encountered during revision arthroplasty in the setting of bone loss and therefore these results may differ if studied in vivo. Additionally, although we focused on one acetabular bone loss pattern, understanding that in vivo bone loss patterns are neither predictable nor identical. Further study of additional bone loss patterns may further elucidate screw locations, which more effectively counter motion vectors corresponding to specific regions of acetabular bone deficiency. Second, our applied loading protocol established by Bergmann et al., relies upon simplified linear vectors, which may not accurately represent the physiologic joint reactive forces transmitted through the acetabular component-bone interface ,15. ThirThe data presented in this study supports the widely held belief that porous coated acetabular implants inserted with the press-fit technique in combination with supplemental screw fixation generate the initial stability necessary for long-term stability via osseointegration in Paprosky IIB acetabular defects. Furthermore, increasing the screw number, length, and position within the acetabular dome may help further stabilize the construct. Together, these findings warrant surgeon consideration during real-time placement of acetabular screws in Paprosky IIB defects.


Metal-on-polyethylene (MoP) is a common type of total hip arthroplasty. Trunnionosis is a rare but concerning complication of this type of implant. Trunnionosis involves wear and corrosion at the femoral component's head-neck interface and may cause a local inflammatory response referred to as an adverse reaction to metal debris (ARMD). We present a rare case of trunnionosis with concurrent calcium pyrophosphate deposition disease (CPPD) and amyloidosis in a MoP implant. ARMD can be linked to crystalline arthropathy and amyloidosis, possibly due to metal ion-induced acidosis. Clinicians should consider trunnionosis in patients with persistent post-surgical hip pain, and order metal ion tests and synovial fluid analysis to aid in the diagnosis of this condition if suspected. Timely recognition enables appropriate surgical revision. Nearly half a million hip replacements are performed in the United States annually. The modern system used for total hip arthroplasty (THA) often consists of 4 separate modular components: a femoral stem, femoral head, liner, and acetabular cup. In the past, a metal-on-metal (MoM) design was favored because a metallic cup and femoral head allow for greater stability, less wear, and theoretically lower rates of hardware failure. However, over time, MoM implants have been shown to wear at the cup-head interface and release metallic particles into the surrounding joint space. This causes adverse reaction to metal debris (ARMD), which is an umbrella term for soft tissue damage from metal particles. It is estimated that 20% of MoM implants will require revision surgery within 10-13 years MoM implants have largely been replaced by a metal-on-polyethylene (MoP) design, which has less than a 4% revision rate after 10 years A 79-year-old male residing at a skilled nursing facility was admitted to the hospital for altered mental status, abdominal pain, and a recent fall. He had a history of bilateral MoP THA, in addition to hypertension, hyperlipidemia, hypothyroidism, coronary artery disease, and aortic stenosis. His surgical history included coronary artery bypass grafting, aortic valve replacement, and total colectomy with ileostomy placement. The left THA was performed for a proximal femoral fracture approximately 20 years ago. He reported occasional left hip/groin pain.CT demonstrated a fluid collection along the patient's left iliopsoas bursa and left hip with foci of metallic debris –3. SubseThe trunnion is a metal-on-metal interface at the femoral head-neck junction that can wear and cause ARMD in MoP implants. Although the exact pathophysiology is unclear, trunnionosis is likely caused by a combination of fretting, chemical corrosion, and metallic ion release, resulting in a lymphocyte-driven inflammatory cascade. Several manifestations of ARMD or ALTR  have been reported: soft tissue necrosis, synovitis, aseptic lymphocyte-dominant vasculitis-associated lesion (ALVAL), and pseudotumor formation Crystalline arthropathy typically presents as sudden onset joint pain and swelling with overlying erythema. The pathophysiology involves monosodium urate (gout) or calcium pyrophosphate (pseudogout) crystal deposition in the articular and periarticular space, leading to inflammation. In the case of pseudogout, also known as calcium pyrophosphate deposition disease (CPPD), the diagnosis is indicated by identifying rhomboid-shaped crystals with weakly positive birefringence in the synovial joint aspirate. Some important risk factors include advanced age, obesity, alcohol consumption, osteoarthritis, acidosis, recent joint surgery, and diabetes mellitus Amyloidosis is a broad term that describes the deposition of misfolded proteins in soft tissue, leading to inflammation and organ dysfunction. It is most commonly associated with multiple myeloma and autoimmune diseases, notably rheumatoid arthritis. Amyloid is identified under polarized light after staining with Congo red. There has been one documented case of ARMD in a MoM implant associated with amyloid deposition, confirmed by Congo red staining It remains unclear whether ARMD causes crystalline arthropathy and amyloidosis, or whether they are involved in the pathophysiology of ARMD. One possible explanation is metal ion-induced acidosis in the local soft tissues. Acidosis is a known risk factor for crystalline arthropathy and is suspected to contribute to protein misfolding in amyloidosis Trunnionosis is a complication of MoP hip replacement surgery that can result in pain and hardware failure and may be associated with concomitant joint disease. Clinicians should include trunnionosis in the differential diagnosis for patients with MoP implants complaining of hip pain, especially if there is evidence of ARMD on imaging. In addition to checking for metal ions, clinicians should check for concomitant amyloid and crystal deposition when a joint aspiration is performed. The prevalence of amyloid and crystal deposition in ARMD is largely unknown due to inadequate screening. When identified, neither process should be treated in isolation. Definitive treatment involves surgical revision of the failed implant.Informed consent for this case was obtained from the patient.


Non-pharmacological treatment is essential for patients with major depressive disorder (MDD) that is medication resistant or who are unable to take medications. Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation method that manipulates neural oscillations. In recent years, tACS has attracted substantial attention for its potential as an MDD treatment. This review summarizes the latest advances in tACS treatment for MDD and outlines future directions for promoting its clinical application. We first introduce the neurophysiological mechanism of tACS and its novel developments. In particular, two well-validated tACS techniques have high application potential: high-definition tACS targeting local brain oscillations and bifocal tACS modulating interarea functional connectivity. Accordingly, we summarize the underlying mechanisms of tACS modulation for MDD. We sort out the local oscillation abnormalities within the reward network and the interarea oscillatory synchronizations among multiple MDD-related networks in MDD patients, which provide potential modulation targets of tACS interventions. Furthermore, we review the latest clinical studies on tACS treatment for MDD, which were based on different modulation mechanisms and reported alleviations in MDD symptoms. Finally, we discuss the main challenges of current tACS treatments for MDD and outline future directions to improve intervention target selection, tACS implementation, and clinical validations. The COVorldwide . Antideporldwide . Studiesorldwide . MoreoveNon-invasive brain stimulation methods, such as electroconvulsive treatment (ECT), transcranial magnetic stimulation (TMS), and transcranial direct current stimulation (tDCS) have been widely used for MDD treatment . In the Transcranial alternating current stimulation applies a weak, frequency-specific sine-wave alternating current to the cortex and modulates brain oscillations by entraining the intrinsic brain oscillations to the applied current, resulting in the phase alignment with external current and the increased power of neural oscillations with frequencies close to the applied current . In addiThe efficiency of conventional tACS, which uses two large electrodes immersed in saline-soaked sponges and guides their placements by the international 10–20 EEG system, was largely limited due to the poor current focus. Encouragingly, some recent advances have significantly improved the current focality of tACS , left. OIn addition, two other important technological developments are currently in the testing stages , right. Regarding the side effects of tACS, some mild symptoms such as temporal nausea, tinnitus, and dizziness have sometimes been reported during the stimulation , and higAccumulating studies have demonstrated both local oscillation abnormalities and interarea synchronization dysfunctions in MDD patients, and tACS may treat MDD by modulating such oscillatory abnormalities. To better understand the functional consequences of these abnormalities, we sorted out recent progress by functional networks, which could be responsible for different MDD symptoms . These fThe human reward network mainly includes the prefrontal cortex and the limbic system , and funAlpha band (8–12 Hz) power has been found to decrease with increasing brain activity . ResearcGamma band (30–100 Hz) power is closely linked to increased local neuronal activities , and accAbnormalities in theta band (4–7 Hz) power in MDD have also been reported. Early studies found increased frontal–midline theta power in the resting state in MDD patients; this increase was located in the anterior cingulate cortex (ACC) and reflected impaired emotion regulation . HoweverIn addition, beta band (14–30 Hz) abnormalities in MDD have also received increasing attention. Some studies using classifier methods reported that beta band features in the frontal lobe are the best at distinguishing MDD patients from healthy individuals . HoweverTo be note, a recent review has summarized the functional differences within the frontal–limbic reward network. For example, the ACC acts as a “control hub”; the medial orbitofrontal cortex (mOFC) and nucleus accumbens (NAc) act as “reward” hubs; and the lateral orbitofrontal cortex (lOFC), ventromedial prefrontal cortex (vmPFC), and amygdala act as “non-reward” hubs . BesidesRecent findings have extended our understanding of oscillation power abnormalities in MDD beyond the reward network. Furthermore, researchers have demonstrated functional connectivity abnormalities among critical MDD-related networks and correlated them with different MDD symptoms . We summThe default mode network (DMN) consists of a group of brain regions that exhibit decreased activity during attention-oriented and goal-directed tasks, with primary hubs of the medial prefrontal cortex (MPFC), posterior cingulate cortex (PCC), precuneus (PCu), and angular gyrus (AG) . ResearcThe central executive network (CEN) plays a pivotal role in tasks requiring executive control, with key nodes including the DLPFC and posterior parietal cortex (PPC) , and accIn recent MDD research, considerable attention has been devoted to abnormalities in the perception system, particularly in the visual system. Earlier studies noted that individuals with MDD demonstrate a significant perceptual bias toward negative information  and an iBesides, the hippocampal–medial temporal lobe (Hipp-MTL) network is known to play a pivotal role in human memory  and its In addition to oscillation power and interarea synchronization, recent studies have examined abnormal brain activity in MDD from a novel perspective of oscillation frequency and have reported important findings regarding individual alpha peak frequency (IAPF). Studies on healthy populations have found that higher IAPF is usually associated with better cognitive ability  and has As the quick developments in tACS techniques and extended understanding of the brain oscillation abnormities in MDD, using tACS to treat MDD has attracted increasing attention in recent years. We conducted a systematic search in a wide range of English databases, including PubMed, EMBASE, Web of Science, the Cochrane Library, Register of Controlled Trials and the Chinese database Zhiwang; we used the following search terms: (“depress*” OR “major depressive disorder” OR “MDD”) AND . Initially, we selected articles based on their titles and abstracts and excluded duplicate articles. Then, we assessed the abstracts and full texts of potentially eligible studies according to predefined inclusion criteria. Finally, we included a total of seven published articles  estimated the frontal tACS effects on MDD among three groups receiving 10 Hz, 40 Hz, and sham stimulation . The bilateral 10-Hz tACS group showed a significant decrease in alpha power in the left frontal and central areas, resulting in decreased FAA among frontal areas. Although no significant alleviation of MDD symptoms was observed in any group immediately after the intervention, the response rate [defined as a decrease in Montgomery-Asberg Depression Rating Scale (MADRS) score ≥50%] was significantly higher in the 10-Hz tACS group than in the 40-Hz tACS or sham groups 2 weeks later . Furthern = 100), the same tACS parameters were used. The results showed that there was a significant reduction in depressive symptoms and a higher response rate in the treatment group in both the immediate test and another test administered 4 weeks after the intervention. At week 4, the response rate (a decrease in HAMD-17 score ≥50%) and remission rate (HAMD-17 score ≤7) were higher than those in the sham group, and the difference in the response rate lasted until week 8  was targeted with 40-Hz tACS at 2 mA for 20 min per day in a pregnant woman with MDD. After receiving nine stimulation sessions within 2 weeks, the depressive symptoms  decreased, and cognitive performance [as assessed with the Trail-Making Test (TMT)] improved. These effects were sustained at 2-week and 3-month follow-up assessments . Subsequl week 8 . TogetheTargeting the abnormally increased theta synchronizations among the MDD-related networks, a recent RCT further tested if tACS desynchronizing theta oscillations could alleviate MDD symptoms. The researchers assigned 33 volunteers with depression and/or anxiety to either the tACS or tDCS group. Each participant received two 20-min stimulation sessions and two 20-min sham-stimulation sessions in a randomized order. In the tDCS group, F3 and FP2 were selected as the anodal and cathodal sites with a current of 2 mA. In contrast, in the tACS group, the strength of theta synchronizations among the whole brain was first calculated, and then a 6-Hz anti-phase current was passed between the two electrodes with the highest theta synchronizations. Although anxiety and depressive symptoms were improved in both groups, the degree of depressive symptom alleviation was more significant in the tACS theta desynchronization group. Further analysis also showed that participants who received the treatment first showed larger improvements than those who received the sham stimulation first . This reIn summary, clinical tACS studies have shown promising improvements in alleviating MDD symptoms. However, we should note that the underlying modulation mechanisms of these studies were various and resulted in different outcomes. For instance, only gamma tACS studies emphasized the enhancement of cognitive performance in MDD patients. Furthermore, while most clinical studies focused on modulating neural oscillations in the frontal cortex, there was a lack of consistency in tACS settings. Discrepancies in electrode placement, stimulated frequency, and dosages could account for the mixed modulation results across studies, particularly in high-frequency interventions. Besides, it is also crucial to conduct more high-quality RCTs that directly compare different categories and settings of tACS modulation effects.Although the significant progress in tACS technology, understanding of neural oscillations, and clinical practices in past decades, there are some challenges to the clinical translation of tACS. We suggest that in-depth interdisciplinary collaboration is necessary to optimize the efficacy of each intervention step and fundamentally promote the clinical application of tACS for MDD treatment. We summarize from three aspects: intervention target selection, stimulation implementation, and clinical validation .Selecting the targets for tACS intervention is fundamental to the success of intervention. Below, we summarize several challenges when choosing intervention candidates with the largest clinical values. First, the causal relationship between most neural oscillation abnormalities and MDD symptoms is unclear. We suggest that, at least three criteria should be satisfied for a tACS intervention candidate as follows: the neural oscillation differs in MDD patients compared to healthy individuals, the neural oscillation strength predicts the severity of MDD symptoms, and the neural oscillation strength returns to normal levels after treatment in case studies. Future studies should more focused on intervention evidence, especially for brain areas besides frontal cortex. Second, the relationship between neural oscillation abnormalities and information processing impairments should be further clarified. On the one hand, MDD studies have found that some neural oscillations exhibit opposite abnormal patterns between the resting state and functional states, suggesting that the functions of neural oscillations could be state-dependent. Therefore, future tACS interventions should consider neural states. On the other hand, the latest data-driven findings have revealed a series of neural features that can distinguish MDD patients from healthy individuals, decoding the mechanism of these abnormal neural features may greatly enlarge our pool of intervention candidates. Third, the correspondence between different symptoms of MDD and specific brain network abnormalities should be further explored. Researchers have summarized three main symptomatologic features of MDD . CurrentThe efficacy of tACS interventions cannot be guaranteed without a precise implementation procedure. Here, we summarize three main challenges for tACS implementation. Standardizing tACS intervention is the top priority. One of the most important aspects of an intervention protocol is determining key parameters, including stimulation sites, current intensities and frequency bands. To guarantee the implementation of a standardized procedure, it is also necessary to provide an operation manual as well as training for potential users. Another important aspect for developing a tACS treatment plan is knowledge of the effects of the number of stimulation sessions and intersession intervals, which should be explored more systematically. Moreover, overcoming critical technical challenges is essential for further improving tACS implementations, which requires more involvements of biomedical engineers. For example, it remains unclear how to effectively suppress (instead of increase) brain oscillations in a specific frequency , and how to modulate an abnormal oscillation pattern that consists of more than one targeted frequency or consists of signals from multiple brain areas . The advances in tACS intervention techniques can better meet various clinical needs for MDD treatment. Another challenge is the development of tACS technology that is compatible with non-invasive neural imaging techniques. Currently, direct measurements of the current distribution of tACS mainly obtained through invasive electrophysiological recordings, and for most application cases, the electrical current distribution of tACS can be determined only by simulations. Solving this technical problem would enable direct observation of the immediate and subsequent effects of tACS intervention and help us better understand its underlying mechanism, providing a gold standard to evaluate intervention efficacy.Clinical validation is vital in determining whether a specific tACS intervention is suitable for widespread use in MDD treatment, and there are several significant challenges in current clinical practice. First, the evidence for the effects of different tACS frequencies on psychiatric symptoms is inconclusive, and clear neurophysiological mechanisms are lacking. The immediate priority is conducting more confirmatory RCTs for several promising tACS intervention plans. The clinical value of tACS should be further emphasized to potential users such as psychiatrists. Second, the highly complex and dynamic nature of MDD symptoms, which require symptom-dependent intervention plans. Depression is highly comorbid with other psychiatric disorders, especially anxiety . AdditioIn the past decade, tACS has demonstrated unique clinical potential in precisely modulating both local and interarea abnormal brain rhythms. Accordingly, accumulating studies have significantly advanced our understanding of brain oscillation abnormalities in MDD from these two perspectives, providing a series of tACS intervention options for MDD treatment. Moreover, pioneering clinical trials have shown preliminary treatment effects of tACS, indicating its potential as a viable MDD treatment option. However, to facilitate the potential clinical application of tACS, further causality studies on neural abnormalities and MDD, research on standardized tACS intervention procedures, and additional RCTs are needed.YC and QC flameworked this review, wrote the future direction session, and generated the final manuscript. YZ, SY, and RP wrote the preliminary manuscript for the advances of tACS, neural abnormalities in MDD, and clinical studies. All authors contributed to the article and approved the submitted version.


Regenerative medicine is a complex discipline that is becoming a hot research topic. Skin, bone, and nerve regeneration dominate current treatments in regenerative medicine. A new type of drug is urgently needed for their treatment due to their high vulnerability to damage and weak self-repairing ability. A self-assembled peptide hydrogel is a good scaffolding material in regenerative medicine because it is similar to the cytoplasmic matrix environment; it promotes cell adhesion, migration, proliferation, and division; and its degradation products are natural and harmless proteins. However, fewer studies have examined the specific mechanisms of self-assembled peptide hydrogels in promoting tissue regeneration. This review summarizes the applications and mechanisms of self-assembled short peptide and peptide hydrogels in skin, bone, and neural healing to improve their applications in tissue healing and regeneration. The term regenerative medicine was first coined in 600 BC. The first surgical textbook in history records that an Indian physician described how to repair torn earlobes with skin from the cheeks and reconstruct a nose with a forehead flap, which can be regarded as the beginning of regenerative medicine in human history ,2,3. RegA self-assembled hydrogel is a good biological scaffold. It has roles in cell attachment and migration and the ability to promote cell–cell interactions, cell proliferation, and cell division ,11. TherUnlike conventional materials, SAP molecules assemble into stable structures through various non-covalent interactions that form from molecules to nanofibers to the final hydrogel network, often exhibiting a hierarchical microstructure . In addiTherefore, using SAP hydrogels in regenerative medicine is of great significance. In this article, we mainly review the progress of SAP and SASP hydrogels loaded with different drugs in tissue regeneration, intending to contribute to studying SAP hydrogels and advancing regenerative medicine.SASP hydrogels comprise alternating hydrophilic and hydrophobic amino acid sequences that are stimulated under certain conditions  to form a stable β-folded structure spontaneously and regularly through non-covalent bonding . These sAs the body’s largest organ in physical contact with the outside world, preventing the entry of foreign objects and pathogens and the loss of body fluids, amongst other functions, the skin is the body’s first direct line of defense against external damage. However, the skin’s repair capacity is poor due to its continual exposure to the external world, resulting in it having difficulty healing, with a long recovery cycle with traditional treatment, during which the patient will suffer much pain ,31. For + and platelet and endothelial cell adhesion molecule 1 [PECAM1/CD31]+ capillaries), cell proliferation , granulation tissue formation , and ECM deposition/modeling . In addition, the KGH hydrogel created a 3D microenvironment for skin cells in vitro that maintained the continuous growth of cell spheroids and increased the secretion of ECM proteins  and growth factors  by keratinocyte-forming cells in the skin, as compared to conventional dosage forms. Their results showed that the SAP hydrogel (KGH) could enhance ECM remodeling and angiogenesis, thereby promoting chronic wound healing in diabetic mice, and mechanistically, it may promote wound tissue regeneration by activating the Rho/Rho-associated coiled-coil containing protein kinase (Rho/ROCK) and TGF-β/mitogen-activated protein kinase (MEK)/mitogen-activated protein kinase (MAPK) pathways [Wound healing is a long-term, multi-stage biological process that includes hemostasis, inflammation, proliferation, and tissue remodeling, requiring specific novel therapeutic tools to provide comprehensive and convenient treatment . When thpathways . Lu et apathways . In addiThe SASP hydrogel has the excellent properties of traditional hydrogels but also has the advantages of drug transport, protein degradation products without toxic side effects on the human body, and using short peptides as raw materials, which is itself a kind of protein, for the final water-based hydrogel, ensuring its safety. Skin regeneration is a research hot spot and a complex area of regenerative medicine. SASPs in skin regeneration have broad applications, and increasing numbers of researchers are investing in this research .As an essential part of the body, bone tissue shows difficulty recovering from injuries and has a complex recovery process due to its recovery being affected by many factors. Therefore, the problem of bone regeneration has aroused a great deal of interest from researchers, and SASP hydrogel scaffolds have become a powerful alternative solution to the current tissue regeneration strategy ,42. As aCurrent treatments for bone defects include repairing soft tissues and reconstructing bone connections. However, the risk of recurrence due to the inability to accurately remove the infected foci leads to treatment failure . In thisSaha et al. hypothesized that combining an oligopeptide P11-4 hydrogel with human dental pulp stromal cells could promote bone regeneration in a rat cranial defect model in vivo. Their experimental results showed that the pH-sensitive self-assembled β-peptides could reversibly switch between fluid and gel phases in response to environmental triggers, resulting in them being potentially useful injectable scaffolds for skeletal tissue engineering applications. The ability of SAPs to self-assemble when triggered by environmental cues and their potential to modulate cell adhesion, mechanical stiffness, and biodegradation by altering peptide sequences result in them being a cellular tissue repair system . In addiCurrently, bone defects have been widely repaired in clinical practice. However, both autologous and allogeneic grafts have certain limitations, and artificial bone suffers from poor biocompatibility and other problems. Therefore, bone tissue engineering technology is expected to become a new therapeutic tool. SASP hydrogels are emerging biomaterials widely used in biomedical applications due to their programmability, low cost, good biocompatibility, and non-toxic degradation products. However, their poor stability, biocompatibility, and mechanical properties mean their degradation rate fails to keep pace with tissue growth, leading to the early release of seed cells, resulting in them failing to reach their intended location and a tendency to cause inflammation. Its weaker mechanical strength limits its ability to be applied to relatively rigid tissues, such as cartilage and bone tissues, which is its main problem in clinical bone tissue engineering applications .Neural regeneration, also known as “neural redifferentiation,” is the process in which neurons or glial cells are wholly or partially replaced or repaired at the injury site, restoring their normal function. This regeneration may occur by producing new neurons, glia, axons, myelin sheaths, or synapses ,53,54. NAutologous nerve grafts are the current gold standard of treatment for long segmental nerve deficits. However, the lack of donor tissue and nerves means they can cause secondary neuromas and painful peripheral neuropathies, resulting in suboptimal prognoses for patients . TherefoWhile SASPs have been shown to promote neural tissue regeneration, research in this area is still in its infancy, and most systematic studies have focused on in vitro cell culture and in vivo combined stem cell transplantation for more than a decade . The SASSome polypeptide sequences can self-assemble to form supramolecular structures under intra- and inter-molecular forces. Peptide-based materials can respond to the physiological environment by self-assembling to form microstructures with functionality for trauma repair . SAP hydSAP hydrogels can bionically mimic the ECM and play a facilitating role in cell adhesion and migration. They also have low immunogenicity and suitable mechanical properties and have shown good osteogenic properties in vivo and in vitro . DeliverResearchers hope to explore whether BMSCs can differentiate into cartilage using in vitro chondrogenic cultures of SAP hydrogels containing BMSCs. An injectable SAP hydrogel encapsulating BMSCs has shown excellent cartilage regeneration ,76. A noHUVECs were cultured with a novel SAP hydrogel (RATEA16) scaffold containing vascular endothelial growth factor (VEGF) to investigate its effect in promoting the proliferation of human umbilical vein endothelial cells (HUVEC) and angiogenesis. The HUVECs encapsulated in the RATEA16 hydrogels were round and proliferated efficiently and continuously . The RADThe SAP hydrogel can be loaded with cells to promote bone tissue regeneration and osteogenic active factors to promote bone tissue repair. Incorporating osteogenic active agents into bone filler materials can accelerate bone tissue regeneration. SAP hydrogels can control the slow release of osteogenic active agents locally and are widely used to deliver active bone regeneration agents . One stuSAPs have important applications in repairing traumatized skin, where they can be used as scaffolds for skin cells and reservoirs for active compounds to accelerate wound healing . The RADStudies have explored the role of an SAP (SCIBIOIII) hydrogel with a unique nanofiber structure mimicking the natural ECM in chronic diabetic wound repair . Their rRegeneration of neuronal tissue and its repair is complex since nerve cells are incapable of regeneration or have a very weak regenerative capacity. SAP hydrogels can repair peripheral nerve injury by promoting cell proliferation or the slow release of loaded drugs . When a After spinal cord injury, a fluid-filled sac develops, and there is an inflammatory response and gliosis at the injury site that limits nerve regeneration . HoweverOne study evaluated the effects of various scaffolds on cell adhesion, proliferation, and expression of functional genes using rat stem cells, finding that nanocomposite structures of peptide co-electrospun scaffolds with cellular recognition function could effectively improve the cells’ proliferation ability, accelerating the growth of axons and promoting the repair of functional nerves to treat peripheral nerve defects . RAD-RGISelf-assembled hydrogels have attracted attention in regenerative medicine due to their biocompatibility, injectability, low immunogenicity, and flexibility in loading cells, proteins, and small molecule drugs . HoweverSAP hydrogels have good functional support for tissue defects but are less than ideal for extensive defects and/or load-bearing bone defects. When treating large bone defects, SAPs can be functionalized and combined with 3D printing and other technologies to mimic better the bone tissue’s regenerative microenvironment, which is rich in stem cells and activating factors, while being cultured in hydrogels before transplantation to improve regeneration . In concWhile tissue engineering is developing rapidly, many problems remain, such as the mechanization of hydrogels with 3D structures being unstable. In addition, we need to explore how to set up a comprehensive monitoring system for this new biomaterial. Moreover, we need to investigate integrating self-assembled hydrogels with other materials or drugs to provide new therapeutic approaches to control their repair of damaged targets in tissue regeneration. For example, we need to examine whether it is possible to add other peptides with different functions of small polypeptide fragments and/or growth factors to a major repair bone regeneration peptide to give it osteogenic and other properties. Consequently, the resulting composite would have controllable biotargeting characteristics when applied in tissue regeneration. These difficulties and challenges will push forward developments in this field.


Understanding proprioceptive functions in human motor control by applying novel signal processing techniques is essential for sports biomechanics, performance, and kinesiology research. There is even an association between proprioceptive dysfunction and neurological disorders. Researchers with expertise across various disciplines should understand the physiological markers of proprioceptive functions at various levels. This Research Topic aimed to integrate cutting-edge biosignal processing methods from kinesiology, biomechanics, and computational modeling to explore new biomarkers of proprioception.Montull et al. proposed an objective measure of proprioception by showing that assessment of Proprioception and motor training effect (before and after) through wearable accelerometry signals was made possible. They showed that Hurst (H)-exponents of accelerometer signals (from legs and center of mass) estimated by Detrended Fluctuation Analysis were significantly lower in the highly trained group after training.As Proprioception relates to movement stability and balance, Mayer et al. examined leg muscle activity and kinematics in response to a single-leg stance on the two sides of the TJ and the floor. They found greater activation in almost all muscles when balancing on either TJ side compared to the floor. However, no differences were found 1) between the two sides in any muscles or 2) in the equilibrium procedures at the pelvis level.Unstructured surfaces are widely used in proprioceptive training to improve balance and joint stability. Considering that there have been no studies that have varied the two sides of the Togu Jumper (TJ) and simultaneously monitored leg muscle activation and kinematics around the ankle, knee, and hip joints, Ivusza et al. showed that random variation in movement patterns during practice training compared to blocked organization of lower-extremity proprioceptive motor practice did not improve balance and postural adjustments. However, Postural adjustment improved only in the sagittal plane, indicating variations in individual adjustment strategies.Hu et al. examined their test-retest reliability as well as corticospinal modulation during such task. They showed that TMS and H-reflex measurements were reliable for different delays between- and within sessions following perturbation, indicating that these methods can be used to measure corticospinal excitability during balance perturbation.Although corticospinal and spinal level mechanisms may underlie balance control during balance perturbation tasks, the excitatory modulation of responses and voluntary activation is still unclear. Given that the reliability of neither transcranial magnetic stimulation (TMS) nor Hoffmann’s reflex (H-reflex) measurements during high-amplitude balance perturbation tasks is unknown, Sun et al. also examined the relationship between posture and H-reflex. However, they compared the neuromodulatory processes of participants with and without peripheral neuropathy (PN) during prone, standing, and the heel-contact phase of walking. Their results indicated that plantar sensory input is important in maintaining standing postural control in the healthy population. The type I afferent fiber reflex loop (H-reflex) contributed more to standing postural control in participants with PN. These results indicate that the H-index parameter may be an excellent method for detecting PN. Still, it is unsuitable for discriminating the severity of PN with impaired foot sole sensitivity.Nagano et al. investigated if gait retraining through biofeedback technique could reduce their fall risk by changing the strategies in gait control. The study showed that the post-stroke group’s affected limb demonstrated lower mean, higher variability, and lower kurtosis of minimum foot clearance (MFC), the minimum of the foot’s vertical margin from the walking surface. Mid-swing MFC was associated with a risk of falls in the elderly. Post-stroke gait was also characterised by shorter step length, larger step width, and increased double support time. However, future studies should further check if free walking MFC features could be more interesting than that in the treadmill protocols they applied.Because post-stroke individuals have such a high risk of falling during walking with cautious gait adaptations, Négyesi et al.) examined the effects of side-dominance on standing stability in healthy young adults using ground reaction force, motion capture (MoCap), and electromyography data, since it appears that central and peripheral functional asymmetry may differ between left- and right-side dominant individuals. This was accomplished by analyzing a multitude of biosignals, including 23 Center of Pressure-related variables, six MoCap variables, and 39 time- and frequency-domain features of Electromyography data from five muscles. It was found that both left- and right-sided participants had a more stable balance when standing unilaterally on their right leg, suggesting that side dominance affects neuromuscular and biomechanical control strategies.Additionally, we  continuously and daily for better assessment of human neurological activities such as Proprioception. Advancements in data science and processing must complement this multidisciplinary research initiative. Future follow-up research topics in this area should be targeted.


Tumor metastasis is an important factor that contributes to the poor prognosis of patients with tumors. Therefore, to solve this problem, research on the mechanism of metastasis is essential. Ferroptosis, a new mode of cell death, is characterized by membrane damage due to lipid peroxidation caused by iron overload. Many studies have shown that excessive ferroptosis can affect tumor metastasis and thus inhibit tumor progression. Recently, circular RNA (circRNA), a type of non-coding RNA, has been shown to be associated with the progression of ferroptosis, thus influencing tumor development. However, the specific mechanisms by which circRNAs affect the progression of ferroptosis and their roles in tumor metastasis are not known. In this review, we systematically discuss the role of circRNAs in regulating tumor ferroptosis and their mechanism of action through sponging miRNAS in various tumors, thereby impacting metastasis. This review helps elucidate the relationship and role of ferroptosis-related circRNAs in tumor metastasis and may provide future researchers with new ideas and directions for targeted therapies. Tumor metastasis is strongly associated with patient prognosis, contributing to more than 90% of cancer-related deaths . CompareMetastasis is a basic feature of malignant tumors . During Ferroptosis is a novel form of regulated cell death proposed by Dixon et al., in 2012 . The occCircRNAs are circular single-stranded RNAs formed by covalent closure; they are stable, conserved, and widely present across species . In addiFerroptosis plays an inhibitory role in tumor metastasis and suppresses tumor progression, mainly affecting both tumor cells and the TME . In tumoCircRNAs and ferroptosis are both closely related to cancer development and metastasis; however, the links and mechanisms between them are not well understood . By reviCircRNAs can not only regulate miRNAs in the circRNA–miRNA–mRNA network but also interact with proteins and even play a role in the occurrence and development of cancer as exosomes. Exosomal circLPAR1 and methyltransferase-like 3 (METTL3) competitively bind RBP eIF3h, effectively reducing the translation of brominated protein 4 (BRD4) and subsequently inhibiting the proliferation, invasion, and migration of colorectal cancer cells . MoreoveIn the mechanism of tumor development and metastasis in the digestive system, ferroptosis-related circRNAs interacts with miRNA to regulate downstream target substances and changes GSH content through the Xc-system to affect GPX4 or directly change GPX4 activity. This, in turn, creates an imbalance in the antioxidants of tumor cells, thus regulating the occurrence or inhibition of ferroptosis in tumor cells. This mechanism occurs in several digestive system tumors, including HCC, GC, oral squamous cell carcinoma (OSCC), and esophageal squamous cell carcinoma (ESCC).in vivo.Lyu et al.  found thin vivo.In the GC, Jiang et al.  found thAmong oral and esophageal tumors, OSCC is a widespread head and neck malignancy of the oropharynx and oral cavity . OSCC isEsophageal cancer (EC), originating from esophageal epithelial cells , includein vivo. CircLMO1 silencing promoted the proliferation and invasion of cervical cancer cells. To explore the related cellular molecular mechanisms, the authors further explored the death pattern induced by circLMO1, and the results showed that it promoted cervical cancer cell death by triggering ferroptosis and apoptosis. In addition, circLMO1 was an important mode of cervical cancer cell death, which was observed by monitoring the response of circLMO1 to the effects of erastin (an activator of ferroptosis) in cervical cancer cells. Thus, by regulating ferroptosis, circLMO1 accelerates cervical cancer cell death.Among reproductive system tumors, cervical cancer is the fourth most common malignancy in the world and the fourth leading cause of cancer death in women, with extremely high morbidity and mortality rates . CircRNAIn endocrine system tumors, including thyroid and breast cancer, ferroptosis-related circRNAs can regulate tumor metastasis by acting as sponges for miRNAs.Based on cancer statistics worldwide, thyroid cancer is the fifth most common malignancy . There aBreast cancer is the most common fatal cancer in women worldwide, and despite advances in various treatments, it remains the second leading cause of tumor-related death in women . CircRNAHER-2 gene plays an important role in tumor biology -positive breast cancer. HER-2-positive tumors account for 20% of all breast cancers . Tumors  biology . Bazhaba biology  report tCDK14 of circCDK14 is a cell cycle-dependent kinase involved in the occurrence and development of gliomas, further examination of the level of circCDK14 in gliomas revealed that the level of circCDK14 in human glioma cells was significantly increased, and circCDK14 was expressed at higher levels in grade II–IV gliomas than grade I–II gliomas. CircCDK14 is predominantly expressed in the cytoplasm. The author further evaluated the biological activity of circCDK14 in gliomas and found that circCDK14 overexpression significantly increased the proliferation, migration, and invasion of glioma cells in vitro. In addition, Kaplan-Meier analysis revealed that circCDK14 levels were negatively correlated with overall survival in patients with glioma. Because circCDK14 is mostly localized in the cytoplasm, the authors speculated that circCDK14 may be a glioma-chelating miRNA. Subsequently, they predicted four miRNAs and showed that miR-3938 and circCDK14 interact in the cytoplasm of glioma cells by luciferase reporter gene testing. CircCDK14 plays a sponging role for miR-3938, and miR-3938 can reverse the biological role of circCDK14 in gliomas. Moreover, PDGFAR was shown to be a direct target gene for miR-3938, and circCDK14 regulated PDGFAR expression by sponging miR-3938. To further verify the role of PDGFRA and circCDK14 in cell ferroptosis, the authos further observed the mitochondrial morphology of glioma cells using transmission electron microscopy, and the results demonstrated that PDGFRA expression was negatively correlated with glioma cell ferroptosis. CircCDK14 can reduce the sensitivity of glioma cells to ferroptosis by regulating PDGFRA expression, thereby promoting the formation and metastasis of gliomas in vivo.Glioma is a highly prevalent and aggressive malignancy of the central nervous system, with a poor prognosis. Despite the availability of advanced chemotherapy, radiation therapy, and surgery, patients with glioma have poor median survival rates. In addition to accelerated proliferation, invasiveness, and treatment resistance, the poor prognosis of severe glioma stems from a limited understanding of the potential pathways as well as a lack of early diagnosis and effective treatments . The cirMany studies have shown that circRNAs can regulate iron death in tumor tissues and cells and that most circRNAs promote or inhibit the occurrence of iron death and cancer progression by affecting miRNAs, providing potential therapeutic methods for cancer treatment. Certain cancers may be affected by a complex circRNA functional network rather than a single circRNA; therefore, the logical progression is to screen for circRNAs and then study the function of a set of significantly differentially expressed circRNAs or a single circRNA. To reveal the role of circRNAs in tumor progression, their potential targets should be explored in further studies. CircRNAs can not only regulate miRNAs in the circRNA–miRNA–mRNA network but also interact with proteins and even play a role in the development of cancer as exosomes.Exploring the mechanism of ferroptosis-related circRNAs in tumor metastasis provides alternative pathways and targets for the further exploration of cancer therapies. Ferroptosis is a metabolic form of oxidative stress-induced cell death, and tumor cells are more metabolically active and have higher ROS loads than normal cells; therefore, cancer cells may have a higher tendency toward ferroptosis than normal cells, which has been confirmed by some studies. Initially, the chemical compounds that induce ferroptosis were identified as novel treatments for cancer. Subsequent mechanistic studies have shown that many cancer-related genes and signaling pathways regulate ferroptosis. Some experiments have shown that mesenchymal and dedifferentiated cancer cells, which are generally resistant to apoptosis and common therapies, as well as so-called “therapeutic persistence” cancer cells, are highly sensitive to ferroptosis inducers, further emphasizing the potential of ferroptosis induction as a novel cancer therapy. CircRNAs have diverse functions in the regulation of cancer metastasis. In addition to influencing ferroptosis-related mechanisms, they also play a role in modulating a range of processes, including apoptosis and cancer immunity. This review summarizes the effects of ferroptosis-related circRNAs on cancer metastasis. Although the regulatory mechanisms of these circRNAs are still not fully understood, they provide promising new targets for cancer therapy. Future research should aim to identify the specific mechanisms by which ferroptosis-related circRNAs regulate cancer metastasis in different types of cancers. Notably, circRNAs are only one type of non-coding RNA associated with tumors, and long non-coding RNAs have a much wider range of tumor-related studies. As such, investigating the effects of other non-coding RNAs alongside ferroptosis-related circRNAs may offer new insights into cancer progression. Although studies on ferroptosis-related circRNAs in certain cancers remain limited, there is a strong rationale for further exploration in a wider range of cancer types. Such investigations can drive innovation and potentially uncover new therapeutic options for the treatment of cancer.


A key challenge in the clinical management and cause of treatment failure of prostate cancer (PCa) is its molecular, cellular and clinical heterogeneity. Modelling systems that fully recapitulate clinical diversity and resistant phenotypes are urgently required for the development of successful personalised PCa therapies. The advent of the three-dimensional (3D) organoid model has revolutionised preclinical cancer research through reflecting heterogeneity and offering genomic and environmental manipulation that has opened up unparalleled opportunities for applications in disease modelling, high-throughput drug screening and precision medicine. Despite these remarkable achievements of organoid technology, several shortcomings in emulating the complex tumor microenvironment and dynamic process of metastasis as well as the epigenome profile limit organoids achieving true in vivo functionality. Technological advances in tissue engineering have enabled the development of innovative tools to facilitate the design of improved 3D cancer models. In this review, we highlight the current in vitro 3D PCa models with a special focus on organoids and discuss engineering approaches to create more physiologically relevant PCa organoid models and maximise their translational relevance that ultimately will help to realise the transformational power of precision medicine. Prostate cancer (PCa) is the second commonest cancer and the fifth leading cause of cancer death among men worldwide, accounting for 1.4 million new cases and 375,000 deaths in 2020 [Despite their limitations, current available in vitro, in vivo and ex vivo PCa preclinical models have yielded important insights into our understanding of the pathogenesis of prostate disease. Due to their infinite growth, cost-effectiveness and capacity for high throughput screening and genome editing, two-dimensional (2D) monolayer cancer cell lines have been widely utilised in PCa research . HoweverIn this review, we outline the current in vitro 3D PCa models with a special focus on organoids and discuss engineering approaches to create more physiologically relevant PCa organoid models and maximise their translational relevance that ultimately will help to realise the transformational power of precision medicine.Spheroids are 3D cell aggregates generated from cancer cell lines and patient-derived cancer cells cultured in suspension using scaffolds, hydrogels or by hanging drop method  Fig. 1)1). OvercOrganoids are self-organising, 3D in vitro structures derived from pluripotent stem cells (PSCs) and adult stem cells (ASCs) that faithfully mimic, through provision with biochemical and biophysical cues, the in vivo epithelial architecture, genetics and function of the organ of origin . PSC-derTo overcome the challenges faced by PDOs, iPSCs have enabled the generation of human prostate organoids , 18. UsiPDX-derived organoids (PDX-Os) are 3D organoid cultures derived from PDXs. Beshiri et al first reported generation of PDX-Os from the LuCaP PDX model demonstrating their utility for drug testing . PDX-Os Organs-on-chips (OoCs) are microsystems designed to recapitulate tissue-specific functions such as cancer metastasis, inflammation, and infection . Human c3D bioprinting is an automated high-throughput system capable to construct multi-layered organoids with tissue architecture in a controlled environment using computer-aided design . Living Current in vitro PCa organoid models still lack an intact TME, which undergoes complex changes as the tumor develops that hugely impact primary tumor growth, metastasis and treatment response. The prostate TME consists of stromal cells, immune cells, vascular cells and also extracellular matrix (ECM) proteins that interact with the tumor cells through a complex network of multiple soluble factors and signalling pathways . TherefoIn vitro 3D systems are often cultured in biologically derived matrices that support cell growth, proliferation, and differentiation. These matrices, termed hydrogels, are 3D networks of hydrophilic polymers that can absorb large amounts of fluids. Due to their permeability, composition and density, hydrogels resemble living tissues and have a strong effect on cell activity and fate .Matrigel, an ECM-based hydrogel, purified from Engelbreth-Holm-Swarm (EHS) mouse sarcoma, has been a popular choice to support 3D organoid growth, especially after the seminal work carried out by Yoshiki Sasai showing the formation of optic cups and stratified neuro retina from ESCs cultured in media supplemented with matrigel and differentiation factors . StudiesDespite its versatility, matrigel is overly complex and undefined. More than 1800 unique proteins have been identified by proteomic analysis, including laminin, collagen, entactin, perlecan and multiple growth factors . The batGiven these limitations, other matrices have been developed as alternatives to matrigel. Decellularized ECM from several human organs have been shown to support 3D cultures –42. HoweIn this space, synthetic hydrogels have emerged as a solution for controlled organoid generation by enabling manipulation of physical and chemical matrix properties. Polyethylene glycol (PEG)-based hydrogels can be adapted to control and enhance stemness and differentiation of organoids, whilst their viscoelasticity has been shown to govern organoid growth and shape , 48. In Organoids can also be made from suspended 3D cell aggregates in ultra-low-attachment plates, coated with hydrophobic hydrogels, to prevent cell attachment . Plates These examples, amongst others, demonstrate the need for better matrices, tailored for specific in vitro applications. The knowledge of biomaterials can also be used to provide more control over in vitro models, as well as raising questions about the indiscriminate use of exogenous ECM for organoid cultures.Reciprocal epithelial-stromal interactions are not only fundamental to prostate organogenesis and function but also central to prostate carcinogenesis and progression. Key differences exist in stromal cells between the normal prostate and prostatic tumors. The healthy prostate consists primarily of smooth muscle cells, whereas prostate tumors tend to predominantly contain fibroblasts and activated myofibroblasts forming a reactive stroma responsible for the deposition of ECM. There is now a growing body of evidence that cancer-associated fibroblasts (CAFs) are key drivers of PCa progression , 54. CAFCell populations which make up prostatic stromal compartments are highly plastic and responsive to their surroundings. Selecting the correct culture media, tissue culture plasticware, ECM and nutrients is especially important when culturing them. All of these factors have been shown to alter stromal cell phenotypes in culture, and as such they may not fully recapitulate the stromal compartment of patients. This, taken alongside the heterogeneous nature of PCa has made modelling the stromal compartment difficult.Early prostate organoid and co-culture studies highlighted an important role for stromal cells in promoting epithelial organisation which is crucial for the formation of prostate organoids , 58. RecTaking a different approach to modelling the prostate stroma in 3D in vitro cultures, the prostate iDO model demonstrated that the iPSCs also have ability to generate and maintain a stromal compartment . In the Prostate tumors are commonly thought to be immunologically ‘cold’ characterised by low numbers of infiltrating cytotoxic lymphocytes and an abundance of suppressive myeloid populations , 65. TheDue to the immunosuppressive and poorly immunogenic nature of the prostate TIME, immune checkpoint blockade has failed to elicit a robust anti-tumor response in most PCa patients , 68. ThoMuch of the current work investigating the interplay between tumor cells and immune cells have utilised simple 2D culture models. Often these studies have focussed on a specific immune cell type either cultured in conditioned media from PCa cell lines or directly co-cultured with PCa cells. To model the immune compartment, studies have used immortalised lymphocyte lines, such as Jurkat cells, or primary immune cells isolated from peripheral blood mononuclear cells (PBMCs) isolated from the blood of healthy human donors . These 2Studies on solid TIMEs have utilised a range of 3D systems including PDOs, PDEs and microfluidic systems . When stTo overcome time constraints when studying retained immune compartments, co-cultures with PBMC-derived cells, or tissue isolated immune cells, which are autologous to the PDO, have been established. These models are particularly important for the study of immune subsets, such as T cells, which need to be Human leukocyte antigens (HLA)-matched to the epithelial compartment. There are fewer complications when studying innate immune subsets, such as mononuclear phagocytes (MNPs), where HLA-matching is not necessary, and cells from unmatched donors are sufficient. These models allow users to optimise culture conditions for an immune population of interest, and to study their function in the presence of tumor cells in vitro. Whilst allowing for longer studies focussed on immune cell phenotype and interaction, these studies are limited when attempting to study many immune cell compartments together. Optimal culture conditions to maintain immune cell viability or polarisation may include immunostimulatory conditions which may not allow for the co-culture of certain immune cell types together.Currently, studies utilising these more complex tumor-immune systems for the study of PCa are lacking, but insights can be drawn from research into other solid malignancies. Immune profiling studies on non-small cell lung cancer (NSCLC), renal cancer and melanoma PDOs demonstrated retention of CD8+ and CD4 + T cells, CD14/CD69+ macrophages, NK and NKT cells and B cells . These sThe lack of organoid vascularisation still remains a major challenge in the field and limits a broader application and impact. The incorporation of a functional vasculature in organoid systems to provide a sufficient supply of oxygen and nutrients as well as metabolic wastes disposal is essential for their growth and maturation . Fluid fStrategies being explored to overcome current limitations and incorporate a vasculature within organoids include introduction of endothelial cells (ECs), microfluidic organ-on-chip devices and 3D microfabrication technologies . The mosCurrently for men with metastatic disease there are limited treatment options that target the metastases themselves. PCa primarily metastasises to the lymph nodes (LNs) and bone, but also to liver, lungs and brain . HoweverLNs are the first site of spread for most cancers, including prostate. During metastasis, PCa cells escape the primary tumor and invade the sentinel LN parenchyma before further dissemination through the bloodstream. Developing models of the LN and lymphatic system is essential to further understand the key factors and processes that lead to metastatic spread with potential for identification of early biomarkers for high-risk patients.Models of LNs have included ex vivo tissue slices, microfluidic chips and engineered tissues, including organoids . Due to PCa patients with bone metastasis harbour osteoblast lesions and suffer from skeletal related events including multifocal pain, fractures and hypercalcemia. Invasion of PCa cells in the bone results in disruption of normal homeostasis of bone formation and resorption. The bone is composed of osteoblasts, osteocytes, osteoclasts and osteogenic cells and their interaction with PCa cells leads to a ‘vicious cycle’’ of bone matrix remodelling whereby through secretion of chemokines and growth factors osteoblasts stimulate formation of bone with poorly organised collagen fibrils and reduced mechanical strength .The bone microenvironment comprises bone marrow mesenchymal and hematopoietic stem cells, ECM, and a vascular network . In vitrCompared to other metastatic sites for PCa, liver metastasis occurs at similar frequencies to lung metastasis and is associated with the worst clinical outcomes for PCa patients . DissemiHepatocyte organoids have been successfully generated, whilst iPSC technology has enabled development of multilineage liver organoids incorporating many non-parenchymal cells and also a vasculature , 97. MicPCa lung metastases are also associated with shorter overall survival times compared to bone and LN metastases and are less responsive to treatments . There hThough metastasis to the brain is uncommon and usually detected post-mortem, development of such models is still vital for translational utility. To metastasize to the brain, PCa cells must first cross the blood-brain barrier before disseminating into the brain parenchyma where interactions with microglial and astroglia cells lead to seeding of lesions . Given tOver the last decade, advances in next-generation sequencing technologies have markedly improved our understanding of the PCa genome, transcriptome and also epigenome. Epigenetic alterations, such as DNA methylation and histone modification, affect the accessibility of DNA and chromatin structure and can influence gene expression. It is now widely reported that during initiation and progression of PCa, large-scale epigenetic changes occur, though how to recapitulate these in 3D in vitro models pose challenges for researchers. Targeted epigenome editing technologies hold promise for manipulation of the 3D genome.APC, Ras-associated domain family member 2, RASSF2, and glutathione-S-transferase, GSTP1, have been consistently demonstrated to be robust biomarkers in detecting PCa [et al uncovered the DNA methylation landscape of mCRPC, highlighting differences with early-stage PCa [Aberrant DNA methylation has been identified across many cancers, including PCa, with distinct methylation patterns reported in benign and tumor tissues . Hypermeting PCa . In additing PCa . Followitage PCa . Interestage PCa , 110. Retage PCa , 112. Sitage PCa . Dysregutage PCa , 115. Tatage PCa .Emerging evidence suggests that changes in metabolite levels may modulate the activity of chromatin-modifying enzymes . TherefoCo-culture systems integrating organoids and OcC engineering to incorporate the multiple cell types of the TME would allow development of a more physiologically relevant PCa model amenable for clinical translation.Design and use of defined synthetic ECM-based matrices, made from tuneable biomaterials that recapitulate the dimensionality and biochemical and biomechanical properties of tumor tissues and are also tailored for specific in vitro applications, will enable the spatiotemporal and shape control of organoid growth, long-term expansion of PCa organoids, increase reproducibility and provide experimental control.Further advancement of the prostate iDO model, with a focus on the generation and maintenance of the stromal compartment will be invaluable for studying PCa epithelial-mesenchymal interactions.Development of more complex 3D models utilising the retained immune compartment or matched PBMC cultures in PDO systems should be a priority to study the immunomodulatory capacity of therapies for PCa.To overcome the obstacle of nutrient supply and emulate mechanobiological features, such as fluid shear stress and hydrodynamic pressure, microfluidic strategies utilising 3D bioprinting and biomaterial-based matrices should be undertaken to build perfusable vascular networks enabling precise spatiotemporal control and modelling of the tumor-vascular interactions that will allow insights into metastasis, immune cell trafficking and delivery of anticancer therapeutics.To model metastasis, biomaterial-based microfluid platforms incorporating both the primary and secondary tumors, vasculature and immune compartment should be developed to bioengineer the pre-metastatic and metastatic niche, creating a ‘metastasis-on-chip’ system for investigation of the biology of organ-specific metastasis and screening of personalized organ-specific therapeutics.Use of targeted editing technologies would allow modelling of the 3D PCa epigenome.To maximise the translational relevance and applicability of the current in vitro PCa organoid model, its limitations need to be addressed by engineering approaches Fig. :Co-cultuPCa is difficult to treat due to its complex heterogeneity which poses a challenge for current preclinical models to recapitulate and a roadblock in development of effective treatments. The crucial breakthrough in 3D organoid culture has now provided a platform to model cancer heterogeneity in vitro and an opportunity for the clinical translation of precision medicine. Despite this immense progress, current organoid culture approaches have not achieved true in vivo-like function, in turn preventing a broader impact. However, progress in tissue engineering using co-cultures, biomaterials, 3D bioprinting techniques and microfluidic devices is enabling the design of more physiologically relevant engineered 3D models. New engineering approaches are addressing recreation of the dynamic and heterogeneous TME and metastatic process through incorporating the various cellular compartments, developing designer ECMs and integrating biophysical and biochemical parameters. Overcoming organoid size and phenotypic variability also needs addressing to also enable reaching their full potential for high-throughput drug screening. Furthermore, genome and epigenome editing technologies hold promise for manipulation of the 3D genome to recreate the alterations seen in PCa. Integration of these engineering strategies and technologies would revolutionise the PCa organoid model and accelerate clinical translation of precision medicine treatments for PCa patients.


Inflammation-dependent changes in gene expression programs in innate immune cells, such as macrophages, involve extensive reprogramming of metabolism. This reprogramming is essential for the production of metabolites required for chromatin modifications, such as acetyl-CoA, and regulate their usage and availability impacting the macrophage epigenome. One of the most transcriptionally induced proinflammatory mediator is nitric oxide (NO), which has been shown to inhibit key metabolic enzymes involved in the production of these metabolites. Recent evidence indicates that NO inhibits mitochondrial enzymes such as pyruvate dehydrogenase (PDH) in macrophages induced by inflammatory stimulus. PDH is involved in the production of acetyl-CoA, which is essential for chromatin modifications in the nucleus, such as histone acetylation. In addition, acetyl-CoA levels in inflamed macrophages are regulated by ATP citrate lyase (ACLY) and citrate transporter SLC25A1. Interestingly, acetyl-CoA producing enzymes, such as PDH and ACLY, have also been reported to be present in the nucleus and to support the local generation of cofactors such as acetyl-CoA. Here, we will discuss the mechanisms involved in the regulation of acetyl-CoA production by metabolic enzymes, their inhibition by prolonged exposure to inflammation stimuli, their involvement in dynamic inflammatory expression changes and how these emerging findings could have significant implications for the design of novel therapeutic approaches. During the inflammatory response, specific cells of the innate immune system, such as macrophages, serve as an internal defense mechanism against infection and tissue damage.By recognizing pathogen-associated molecular patterns, macrophages undergo significant changes in gene expression programs and activate an extensive reprogramming of their metabolism –3. RecenIn this Mini Review, we aim to discuss emerging concepts related to metabolic reprogramming and transcriptional activation in macrophages induced by inflammatory stimuli. Specifically, we will focus on how nitric oxide, produced by macrophages upon prolonged exposure to LPS, affects metabolic remodeling and consequently regulates the transcription of inflammatory genes. Recent studies have revealed the mechanism by which NO blocks the activity of mitochondrial TCA cycle enzymes, including pyruvate dehydrogenase (PDH), which impacts acetyl-CoA production –29. acetCentral to the inflammatory response in macrophages is the transcriptional induction of inducible nitric oxide synthase (iNOS), which produces significant amounts of nitric oxide (NO) and reactive nitrogen species (RNS). One of the essential steps for iNOS transcriptional activation is the binding of transcription factors induced by inflammatory stimuli on iNOS promoter region, such as NF-kB, AP1, IRFs and STATs family members . InflammFirst of all, the generation of NO plays a key role in the pro-inflammatory switch of macrophages by inhibiting mitochondrial respiration. This is achieved through nitrosation of NADH dehydrogenase (Complex I) and reversible inhibition of cytochrome c oxidase (Complex IV) –39, withSecondly, in addition to its effects on mitochondrial respiration, NO also modulates metabolic remodeling in inflammatory macrophages by regulating the TCA cycle. Specifically, NO has been shown to inhibit pyruvate dehydrogenase (PDH) , 28 Fi.Mechanisms targeting different subunits of PDH have been recently proposed to regulate its activity Figure 1In this manner, NO plays a unique and fundamental role in regulating the balance of the key metabolites for macrophage function such as acetyl-CoA, itaconate, succinate and citrate. Thus, NO takes center stage not only as an orchestrator of changes in macrophage mitochondrial metabolism during prolonged stimulation, but also a potential regulator of downstream epigenomic changes.During the early stages of an inflammatory response, there is an upregulation of glycolysis, leading to an increased production of pyruvate. This pyruvate is then utilized by PDH to enter the TCA cycle . SimultaAn additional layer of regulation of acetyl-CoA levels in inflammatory macrophages involves citrate transport. In this regard, the mitochondrial citrate carrier (CIC), also known as SLC25A1, plays crucial role in exporting citrate/isocitrate from the mitochondria in exchange for the entry of cytosolic malate  Figure.Recent discoveries have highlighted the significance of exported citrate and cytosolic acetyl-CoA generation as signaling metabolites that govern metabolite reprogramming to support inflammatory responses . In actiAcetyl-CoA, a molecule that faces difficulty in crossing cellular membranes, has two possible ways to enter the nucleus: either through nuclear pores or by being produced directly within the nucleus. Similarly, citrate, which has the ability to diffuse across nuclear pores, can be utilized within the nucleus to generate acetyl-CoA specifically for histone acetylation.Interestingly, the cytosolic enzyme ACLY is present in the nucleus and plays a role in enhancing histone acetylation, thereby promoting the transcriptional activation of specific genes . AlthougBesides ACLY, also the other acetyl-CoA producing enzyme PDH has been extensively demonstrated to be present and functional in the nucleus. Despite its primary localization in the mitochondria, PDH has been reported to undergo translocation from the mitochondria to the nucleus in response to specific stimuli, thereby playing a role in histone acetylation regulation , 48–52.The challenge lies in understanding how this large macromolecular enzyme complex, which can reach sizes up to 10 MDa, is able to traverse from the mitochondria to the nucleus, considering its inability to pass through nuclear pores. As it lacks a nuclear localization signal (NLS), the mechanism behind PDH’s translocation remains unclear. Recent studies have proposed a non-canonical nuclear import pathway that does not involve the nuclear pore complex . In thisInterestingly, a recent biochemical study utilizing mass spectrometry has provided intriguing findings regarding the flexibility of PDH’s structure. It was discovered that under physiological ionic strength, PDH exhibits pliability, allowing it to change its size and dissociate into sub-megadalton individual components . These fFurther exploration into the mechanisms underlying the translocation of metabolic enzymes into the nucleus, as well as their involvement in epigenetic regulation in activated macrophages, holds the potential to unveil novel insights into the intricate interplay between metabolism and gene expression.The existence of such an intricate interplay between cellular metabolism and macrophage transcriptional response has led to the exploration of metabolic reprogramming as a novel therapeutic strategy for controlling macrophage activity in inflammatory diseases. Indeed, the possibility to modulate the intracellular metabolic pathways has recently emerged as a potential novel strategy to reshape dysfunctional macrophage functions, offering new therapeutic opportunities –58.For example, several ACLY inhibitors have shown promising results in various therapeutic areas, including the modulation of inflammation and the reduction of atherosclerotic disease progression. , 31. UsiAlternatively, enhancing mitochondrial function, such as through the inhibition of iNOS or through the inhibition of the RNS species generated in inflamed macrophages, could be a valuable strategy to improve the reprogramming of the TCA cycle and effectively control inflammatory diseases. By restoring mitochondrial function, it may be possible to promote metabolic adaptations that can regulate inflammation and restore cellular homeostasis. Van den Bossche et al. demonstrated that inhibition of iNOS in mouse macrophages effectively mitigated the decrease in mitochondrial respiration caused by LPS and IFNg stimuli . ConsequMR: Conceptualization, Writing – original draft. FP: Visualization, Writing – review & editing. SG: Conceptualization, Writing – original draft.


This Research Topic synthesizes different contributions highlighting the role of crop wild relatives (CWRs) that possess valuable traits for improving and enhancing the adaptation of current commercial crop cultivars to the fast-changing climate. However, their optimal utilization is challenged at the very basic level because of a lack of essential information on CWR accessions in genebanks and subsequent lack of their utilization in respective crop breeding programs. To fully employ CWRs, the public and private sectors need to be better coordinated with enabling policies, proper funding support, and adequate capability building. In addition, there is a need for the execution of systematic data-driven and informed germplasm collection and management. Furthermore, breeding, genomics, and gene-editing innovations present fascinating opportunities for the timely employment of CWRs in breeding programs. Ultimately, climate-smart crops will ensure food and nutrition security and the proper use of CWRs will especially benefit farmers in tropical and subtropical countries.Our concern is that climate change will very likely affect crop productivity, especially that of staple crops . Wheat iYang et al., has provided valuable insight into the diversity and evolution of transcription factor (TF) genes in wheat, which can be used for its genetic improvements. Specific TF genes regulate gene expression, which ultimately determines the related phenotype. The authors successfully identified a total of 6,023 TF genes grouped into 59 gene families and performed a comprehensive genome search, followed by a classification process. A major finding from their study was the significance of these genes for the agronomical traits of wheat crop. The related characteristics and dN/dS values of these TF genes are linked to their selective effects. Interestingly, using information based on selective signals and known quantitative trait loci (QTLs), 21 TF genes were eventually linked with yield-related traits. An important insight was that selective pressure due to domestication on the A and D sub-genomes could potentially be responsible for a genetic bottleneck in TF genes. Wheat breeding programs aim to increase gene diversity while developing climate-smart cultivars. These programs now have these TF genes and their accompanying haplotypes linked to critical characteristics.The first article included in this Research Topic, by Balla et al. They focused on identifying heat stress tolerant wild emmer wheat germplasm and associated QTLs. Multiple derivative lines of nine wild parents from different heat stress environments and genome-wide association analysis using SNP markers identified strong marker-trait associations (MTAs). Interestingly, various MTAs on 1A, 3A, 3B, and 5B chromosomes revealed an association with useful traits, such as chlorophyll content at plant maturity (1A and 5B chromosomes), traits related to grain yield (3A and 3B), biomass (3A and 3B), days to maturity (3A), thousand kernel weight (3A), and heat tolerance efficiency  under different heat stress levels. Importantly, now we know that some of the heat stress tolerance-linked favorable alleles are missing or are rare in the elite durum wheat germplasm. Therefore, the work of these authors highlighted the potential of using the identified lines, MTAs, and QTLs from wild emmer wheat in breeding programs to improve wheat adaptation to heat stress. Furthermore, the identified germplasm lines hold promise for enhancing tolerance to other stressors leading to the development of multiple stress-resistant, climate-smart crops.The valuable insights into the potential of utilizing CWRs of wheat for trait discovery in developing climate-smart cultivars are further strengthened by Christiansen et al. on the perennial halophytic shrubs Atriplex nummularia and Rhagodia preissii. These shrubs can potentially be grown on saline land in Australia as feed for sheep and cattle during autumn. These researchers filled the critical knowledge gap on optimal germination conditions, which up until now had seen limited adoption of direct seeding techniques. The research showed that these shrubs can be optimally germinated at 10°C, whereas Atriplex nummularia seeds seem more tolerant to higher levels of stressors . The study recommended the use of these underutilized shrubs through direct seeding and by sowing them during the cold winter months  or in autumn and spring (temperate regions) for their successful establishment in the saline lands of Australia.Sustaining crop production also includes climate-smart cropping options for animal feed. In this context, important work published in this Research Topic included a study by Charles et al., who provide insights into sustainable and efficient climate-smart crop production systems using semi-transparent organic solar cells (ST-OSCs) in greenhouses. Three different ST-OSC filters with varying light spectra affected both the power generation and crop growth of lettuce and tomato plants. Integration of ST-OSCs into greenhouses offers opportunities for energy-neutral and climate-protected crop production. Such benefits go beyond energy considerations; they could potentially enhance the nutritional value of crops and influence their growth and development patterns, such as flowering initiation in tomatoes.The next research on this Research Topic is presented by Rajpal et al., focuses on the lentil crop, one of the less-known and researched crops. Modern lentil varieties, similar to other staple crops, also struggle with a narrow genetic base due to the loss of their genes during recurrent selections and genetic bottlenecks. However, recent advances in the collection and characterization of lentil CWRs have provided useful avenues for developing improved lentil cultivars that possess tolerance to various stresses, including being climate smart. To have an efficient and effective breeding program for the identification and introgression of desirable traits from distant and CWRs in lentils requires the selection of such traits using related QTL identification and marker-assisted selection (MAS). Recent advancements in genetic diversity studies, genome mapping, and high-throughput sequencing have facilitated the identification of stress-responsive adaptive genes, QTLs, and other favorable traits in CWRs of lentils. Integration of genomic technologies with conventional plant breeding technologies has paved the way for developing dense genomic linkage maps, global genotyping, and large transcriptomic datasets, enabling MAS and breeding in lentils. The lentil genome assembly and exploration of its wild species have provided novel insights into the genomic architecture and evolution of this less researched and understood legume crop.While the first and second studies included in this Research Topic focused on the wheat crop, one of the main and well-researched staple crops, the final study, by In the context of climate change and the compelling race to develop climate-smart cultivars, it is critical to note the advancements made in characterizing wild genetic resources, developing high-density genetic maps, carrying out precise QTL mapping, performing genome-wide association analyses, and applying genomics technologies for lentil improvement.These developments support climate resilience in different crops to fulfill future food demand and secure sustainable crop yields. Researchers and breeders can combine genetic traits and rare genes and alleles from wild crop relatives to create climate-smart crops that could guarantee food security.We hope readers will find this Research Topic and published research papers critical in filling the existing knowledge gaps in utilizing CWRs in crop improvement through data-informed germplasm collection and their utilization for developing climate-smart crops.DG and KB contributed to the editorial write up. DG wrote the first draft and KB edited the draft. Both the authors read, and approved the submitted version.