Mesenchymal stem cells in the treatment of spinal cord injuries: A review

Treatment of spinal cord injury with biomaterials and stem cell therapy in non-human primates and humans

Spinal cord injury results in the loss of sensory, motor, and autonomic functions, which almost always produces permanent physical disability. Thus, in the search for more effective treatments than those already applied for years, which are not entirely efficient, researches have been able to demonstrate the potential of biological strategies using biomaterials to tissue manufacturing through bioengineering and stem cell therapy as a neuroregenerative approach, seeking to promote neuronal recovery after spinal cord injury. Each of these strategies has been developed and meticulously evaluated in several animal models with the aim of analyzing the potential of interventions for neuronal repair and, consequently, boosting functional recovery. Although the majority of experimental research has been conducted in rodents, there is increasing recognition of the importance, and need, of evaluating the safety and efficacy of these interventions in non-human primates before moving to clinical trials involving therapies potentially promising in humans. This article is a literature review from databases (PubMed, Science Direct, Elsevier, Scielo, Redalyc, Cochrane, and NCBI) from 10 years ago to date, using keywords (spinal cord injury, cell therapy, non-human primates, humans, and bioengineering in spinal cord injury). From 110 retrieved articles, after two selection rounds based on inclusion and exclusion criteria, 21 articles were analyzed. Thus, this review arises from the need to recognize the experimental therapeutic advances applied in non-human primates and even humans, aimed at deepening these strategies and identifying the advantages and influence of the results on extrapolation for clinical applicability in humans.

Regenerative medicine approaches for the treatment of spinal cord injuries: Progress and challenges

Spinal cord injury (SCI) is a profound medical condition that significantly hampers motor function, imposing substantial limitations on daily activities and exerting a considerable financial burden on patients and their families. The constrained regenerative capacity of endogenous spinal cord tissue, exacerbated by the inflammatory response following the initial trauma, poses a formidable obstacle to effective therapy. Recent advancements in the field, stem cells, biomaterials, and molecular therapy, show promising outcomes. This review provides a comprehensive analysis of tissue engineering and regenerative medicine approaches for SCI treatment, including cell transplantation, tissue-engineered construct implantation, and other potential therapeutic strategies. Additionally, it sheds light on preclinical animal studies and recent clinical trials incorporating these modalities, providing a glimpse into the evolving landscape of SCI management. STATEMENT OF SIGNIFICANCE: The investigation into spinal cord injury (SCI) treatments focuses on reducing long-term impacts by targeting scar inhibition and enhancing regeneration through stem cells, with or without growth factors. Induced pluripotent stem cells (iPSCs) show promise for autologous use, with clinical trials confirming their safety. Challenges include low cell viability and difficulty in targeted differentiation. Biomaterial scaffolds hold potential for improving cell viability and integration, and extracellular vesicles (EVs) are emerging as a novel therapy. While EV research is in its early stages, stem cell trials demonstrate safety and potential recovery. Advancing tissue engineering approaches with biomaterial scaffolds is crucial for human trials.

Synergistic effects of human umbilical cord mesenchymal stem cells/neural stem cells and epidural electrical stimulation on spinal cord injury rehabilitation

Spinal cord injury (SCI) is a severe neurological condition marked by a complex pathology leading to irreversible functional loss, which current treatments fail to improve. Epidural electrical stimulation (EES) shows promise in alleviating pathological pain, regulating hemodynamic disturbances, and enhancing motor function by modulating residual interneurons in the lower spinal cord. Cell transplantation (CT), especially using human umbilical cord mesenchymal stem cells (hUCMSCs) and neural stem cells (NSCs), has significantly improved sensory and motor recovery in SCI. However, the limitations of single treatments have driven the exploration of a multifaceted strategy, combining various modalities to optimize recovery at different stages. To comprehensively investigate the effectiveness of in situ transplantation of hUCMSCs/NSCs combined with subacute epidural electrical stimulation in a murine spinal cord crush injury model, providing valuable references for future animal studies and clinical research. In this study, we first examined neural stem cell changes via mRNA sequencing in an in vitro Transwell co-culture model. We then explored cell interaction mechanisms using proliferation assays, differentiation assays, and neuron complexity analysis. For animal experiments, 40 C57BL/6 mice were assigned to four groups (Injury/EES/CT/Combination). Histological evaluations employed HE and immunofluorescence staining, while electrophysiological and behavioral tests assessed motor recovery. Quantitative data were reported as mean ± standard error, with statistical analyses performed using GraphPad Prism and SPSS. Initially, we found that NSCs in the in vitro co-culture model showed a unique expression profile of differentially expressed genes (DEGs) compared to controls. GO/KEGG analysis indicated these DEGs were mainly linked to cell differentiation and growth factor secretion pathways. Neuronal and astrocytic markers further confirmed enhanced NSC differentiation and neuronal maturation in the co-culture model. In vivo, live imaging and human nuclei immunofluorescence staining revealed that transplanted cells persisted for some time post-transplantation. Histological analysis showed that during acute inflammation, both the stem cell and combined therapy groups significantly inhibited microglial polarization. In the chronic phase, these groups reduced fibrotic scar formation and encouraged astrocytic bridging. Behavioral tests, including swimming and gait analysis, demonstrated that combined CT and EES therapy was more effective than either treatment alone. In summary, the combined therapy offers a promising approach for spinal cord injury treatment, providing superior outcomes over individual treatments. Our findings underscore the potential of a combined treatment approach utilizing stem cells transplantation and EES as an effective strategy for the comprehensive management of spinal cord crush injury in mice. This integrated approach holds promise for enhancing functional recovery and improving the quality of life for individuals with spinal cord injury (SCI).

Influential factors on stem cell therapy success in canine model of spinal cord Injury: A systematic review and meta-analysis

Spinal cord injury (SCI) is a serious medical condition. The search for an effective cure remains a persistent challenge. Current treatments, unfortunately, are unable to sufficiently improve neurological function, often leading to lifelong disability. This systematic review and meta-analysis evaluated the effectiveness of stem cell therapy for SCI using canine models. It also explored the optimal protocol for implementing stem cell therapy. A comprehensive search of studies was conducted from 2000 to October 2022. This study focused on five outcomes: motor function score, histopathology, IHC, western blot, and SEP. The results demonstrated a significant improvement in locomotion post-SCI in dogs treated with stem cell therapy. The therapy also led to an average increase of 3.15 points in the Olby score of the treated dogs compared to the control group. These findings highlights stem cell therapy's potential as a promising SCI treatment. The meta-analysis suggests that using bone marrow stem cells, undergoing neural differentiation in vitro, applying a surgical implantation or intrathecal route of administration, associating matrigel in combination with stem cells, and a waiting period of two weeks before starting treatment can enhance SCI treatment effectiveness.

Adipose-Derived Stem Cell Therapy in Spinal Cord Injury

Spinal cord injury (SCI) is a serious condition accompanied by severe adverse events that affect several aspects of the patient's life, such as motor, sensory, and functional impairment. Despite its severe consequences, definitive treatment for these injuries is still missing. Therefore, researchers have focused on developing treatment strategies aimed at ensuring full recovery post-SCI. Accordingly, attention has been drawn toward cellular therapy using mesenchymal stem cells. Considering their wide availability, decreased immunogenicity, wide expansion capacity, and impressive effectiveness in many therapeutic approaches, adipose-derived stem cell (ADSC) injections in SCI cases have been investigated and showed promising results. In this review, SCI pathophysiology and ADSC transplantation benefits are discussed independently, together with SCI animal models and adipose stem cell preparation and application techniques. The mechanisms of healing in an SCI post-ADSC injection, the outcomes of this therapeutic approach, and current clinical trials are also deliberated, in addition to the challenges and future perspectives, aiming to encourage further research in this field.

Distinct biological characteristics of mesenchymal stem cells separated from different components of human placenta

Mesenchymal stem cells (MSCs) have tremendous potential in cell therapy and regenerative medicine. The placenta-derived MSCs (PMSCs) are becoming favorable sources as they are ethically preferable and rich in MSCs. Although several subgroups of PMSCs have been identified from human term placenta, optimal sources for specific clinical applications remain to be elucidated. This study aimed to isolate MSCs from various components of the placenta, and compare their biological characteristics, including morphology, proliferation, immunophenotype, differentiation potential, growth factor and cytokine secretion, and immunomodulatory properties. Finally, four distinct groups of PMSCs were isolated from the placenta: amniotic membrane-derived MSCs (AM-MSCs), chorionic membrane-derived MSCs (CM-MSCs), chorionic plate-derived MSCs (CP-MSCs), and chorionic villi-derived MSCs (CV-MSCs). The results showed that CV-MSCs had good proliferation ability, and were easier to induce osteogenic and chondrogenic differentiation; CP-MSCs exhibited the strongest inhibitory effect on the proliferation of activated T cells, secreted high levels of EGF and IL-6, and could well differentiate into osteoblasts, adipocytes, and chondroblasts; AM-MSCs showed good growth dynamics in the early generations, were able to grow at high density, and tended to induce differentiation into osteogenic and neural lineages. These findings may provide novel evidence for the selection of seed cells in clinical application.

The effect of thyme essential oil and endothelial progenitor stem cells on lipopolysaccharide-induced sepsis in C57BL/6 mice

Sepsis is a potentially fatal syndrome related to severe systemic inflammation developed by infection. Despite different antimicrobial therapies, morbidity and mortality rates remain high. Herbs along with cell therapy have been introduced as a promising option to improve the symptoms of sepsis. The present study aimed to evaluate the therapeutic effect of simultaneous administration of thyme essential oil (TEO) and endothelial progenitor stem cells (EPCs) on lipopolysaccharide (LPS)-induced sepsis in C57BL/6 mice. Sepsis was induced in C57Bl/6J mice by intraperitoneal injection of LPS, followed 2 h later by an intravenous injection of EPCs or oral administration of TEO or simultaneous administration of TEO and EPCs. After 10 days, the complete blood cell, renal and liver factors, serum levels of inflammatory cytokines, and angiogenic factors were measured. Simultaneous treatment with EPCs and TEO significantly increased the survival of mice with sepsis and modulated the inflammatory response by reducing the serum levels of pro-inflammatory cytokines. Moreover, this treatment significantly reduced the level of white blood cells and neutrophils and increased the number of red blood cells, the percentage of hematocrit, and hemoglobin. The combination of TEO with EPCs decreased organ injuries and was assessed by lower levels of the liver enzymes alanine aminotransferase and aspartate aminotransferase compared to the sepsis group. Administration of EPCs and TEO also significantly improved angiogenic factors, lung function, and toll-like receptor 4 expression. EPCs in combination with TEO increase survival in the LPS-induced sepsis mice model by acting on several targets. Thus, the combination of TEO with EPCs can be a feasible approach for the future clinical treatment and control of sepsis.

The Effect of Aligned and Random Electrospun Fibers Derived from Porcine Decellularized ECM on Mesenchymal Stem Cell-Based Treatments for Spinal Cord Injury

The impact of traumatic spinal cord injury (SCI) can be extremely devastating, as it often results in the disruption of neural tissues, impeding the regenerative capacity of the central nervous system. However, recent research has demonstrated that mesenchymal stem cells (MSCs) possess the capacity for multi-differentiation and have a proven track record of safety in clinical applications, thus rendering them effective in facilitating the repair of spinal cord injuries. It is urgent to develop an aligned scaffold that can effectively load MSCs for promoting cell aligned proliferation and differentiation. In this study, we prepared an aligned nanofiber scaffold using the porcine decellularized spinal cord matrix (DSC) to induce MSCs differentiation for spinal cord injury. The decellularization method removed 87% of the immune components while retaining crucial proteins in DSC. The electrospinning technique was employed to fabricate an aligned nanofiber scaffold possessing biocompatibility and a diameter of 720 nm. In in vitro and in vivo experiments, the aligned nanofiber scaffold induces the aligned growth of MSCs and promotes their differentiation into neurons, leading to tissue regeneration and nerve repair after spinal cord injury. The approach exhibits promising potential for the future development of nerve regeneration scaffolds for spinal cord injury treatment.

Enhancing regenerative potential: A comprehensive review of stem cell transplantation for sports-related neuronal injuries, with a focus on spinal cord injuries and peripheral nervous system damage

Neuronal injuries, as one of the consequences of sports-related incidents, exert a profound influence on the athletes' future, potentially leading to complete immobility and impeding their athletic pursuits. In cases of severe damage inflicted upon the spinal cord (SC) and peripheral nervous systems (PNS), the regenerative process is notably compromised, rendering it essentially inefficient. Among the pivotal therapeutic approaches for the enhancement and prevention of secondary SC injuries (SCI), stem cell transplantation (SCT) stands out prominently. Stem cells, whether directly involved in replacement and reconstruction or indirectly through modification and secretion of crucial bioenvironmental factors, engage in the intricate process of tissue regeneration. Stem cells, through the secretion of neurotrophic factors (NTFs) (aiming to modulate the immune system), reduction of inflammation, axonal growth stimulation, and myelin formation, endeavor to facilitate the regeneration of damaged SC tissue. The fundamental challenges of this approach encompass the proper selection of suitable stem cell candidates for transplantation and the establishment of an appropriate microenvironment conducive to SC repair. In this article, an attempt has been made to explore sports-related injuries, particularly SCI, to comprehensively review innovative methods for treating SCI, and to address the existing challenges. Additionally, some of the stem cells used in neural injuries and the process of their utilization have been discussed.

Neurological recovery and neurogenesis by curcumin sustained-release system cross-linked with an acellular spinal cord scaffold in rat spinal cord injury: Targeting NLRP3 inflammasome pathway

In the context of treating spinal cord injury (SCI), the modulation of inflammatory responses, and the creation of a suitable region for tissue regeneration may present a promising approach. This study aimed to evaluate the effects of curcumin (Cur)-loaded bovine serum albumin nanoparticles (Cur-BSA NPs) cross-linked with an acellular spinal cord scaffold (ASCS) on the functional recovery in a rat model of SCI. We developed an ASCS using chemical and physical methods. Cur-BSA, and blank (B-BSA) NPs were fabricated and cross-linked with ASCS via EDC-NHS, resulting in the production of Cur-ASCS and B-ASCS. We assessed the properties of scaffolds and NPs as well as their cross-links. Finally, using a male rat hemisection model of SCI, we investigated the consequences of the resulting scaffolds. The inflammatory markers, neuroregeneration, and functional recovery were evaluated. Our results showed that Cur was efficiently entrapped at the rate of 42% ± 1.3 in the NPs. Compared to B-ASCS, Cur-ASCS showed greater effectiveness in the promotion of motor recovery. The implantation of both scaffolds could increase the migration of neural stem cells (Nestin- and GFAP-positive cells) following SCI with the superiority of Cur-ASCS. Cur-ASCS was successful to regulate the gene expression and protein levels of NLRP3, ASC, and Casp1in the spinal cord lesion. Our results indicate that using ASCS can lead to the entrance of cells into the scaffold and promote neurogenesis. However, Cur-ASCS had greater effects in terms of inflammation relief and enhanced neurogenesis.

Remarkable recovery of lower extremity motor impairment in degenerative disc disease after percutaneous laser disc decompression combined with umbilical cord-derived mesenchymal stem cells implantation: A case report

INTRODUCTION AND IMPORTANCE

Degenerative disc disease (DDD) is a common cause of low back pain, often leading to significant discomfort for patients. Current treatment options such as spinal fusion and physical therapy focus on symptom management rather than addressing the underlying degeneration. Percutaneous laser disc decompression (PLDD) has shown efficacy in treating radicular pain associated with disc herniation. However, there is a growing interest in utilizing tissue engineering approaches to reverse the pathological process of DDD. While results in larger vertebrates have been inconsistent, mesenchymal stem cells (MSCs) have demonstrated promise in small animal models.

CASE PRESENTATION

A 46-year-old male presented with low back pain as well as urinary and fecal incontinence. Magnetic resonance imaging revealed disc bulging and foraminal stenosis at the L2-L4 levels. The patient underwent PLDD combined with umbilical cord-derived mesenchymal stem cells (UC-MSCs) injection, which later resulted in significant pain reduction and improved motor function. At six months of follow-up, the patient reported sustained pain relief and functional improvement.

CLINICAL DISCUSSION

Percutaneous decompression techniques not only substantially reduce intradiscal pressure and facilitate the implosion of herniation inward but also concurrently expedite the degeneration of the intervertebral disc. Therefore, in addition to performing PLDD, stem cell injection is also carried out. This report underscores the importance of integrating mechanical and biological interventions for degenerative disc diseases, suggesting PLDD combined with MSC therapy as a promising strategy for managing DDD and potentially reversing its progression. We found that the patient had decreased pain postoperatively; he no longer complained of pain after six months of follow-up.

CONCLUSION

PLDD combined with UC-MSCs might be an alternative treatment for patients with DDD. In addition to mechanical treatment, biological treatment with MSC injections is believed to be a potent combination for treating degenerative diseases such as DDD.

Extracellular vesicles released by transforming growth factor-beta 1-preconditional mesenchymal stem cells promote recovery in mice with spinal cord injury

Spinal cord injury (SCI) causes neuroinflammation, neuronal death, and severe axonal connections. Alleviating neuroinflammation, protecting residual cells and promoting neuronal regeneration via endogenous neural stem cells (eNSCs) represent potential strategies for SCI treatment. Extracellular vesicles (EVs) released by mesenchymal stem cells have emerged as pathological mediators and alternatives to cell-based therapies following SCI. In the present study, EVs isolated from untreated (control, C-EVs) and TGF-β1-treated (T-EVs) mesenchymal stem cells were injected into SCI mice to compare the therapeutic effects and explore the underlying mechanisms. Our study demonstrated for the first time that the application of T-EVs markedly enhanced the proliferation and antiapoptotic ability of NSCs in vitro. The infusion of T-EVs into SCI mice increased the shift from the M1 to M2 polarization of reactive microglia, alleviated neuroinflammation, and enhanced the neuroprotection of residual cells during the acute phase. Moreover, T-EVs increased the number of eNSCs around the epicenter. Consequently, T-EVs further promoted neurite outgrowth, increased axonal regrowth and remyelination, and facilitated locomotor recovery in the chronic stage. Furthermore, the use of T-EVs in Rictor-/- SCI mice (conditional knockout of Rictor in NSCs) showed that T-EVs failed to increase the activation of eNSCs and improve neurogenesis sufficiently, which suggested that T-EVs might induce the activation of eNSCs by targeting the mTORC2/Rictor pathway. Taken together, our findings indicate the prominent role of T-EVs in the treatment of SCI, and the therapeutic efficacy of T-EVs for SCI treatment might be optimized by enhancing the activation of eNSCs via the mTORC2/Rictor signaling pathway.

Mesenchymal stem cell-based therapies for treating well-studied neurological disorders: a systematic review

Background

Millions of people across the globe are affected by conditions like Amyotrophic Lateral Sclerosis (ALS), Parkinson's Disease (PD), Multiple Sclerosis (MS), Spinal Cord Injury (SCI), and Traumatic Brain Injury (TBI), although most occurrences are common in the elderly population. This systematic review aims to highlight the safety of the procedures, their tolerability, and efficacy of the available therapies conducted over the years using mesenchymal stem cells (MSCs) in treating the neurological conditions mentioned above.

Methods

PubMed was used to search for published data from clinical trials performed using mesenchymal stem cells. Studies that provided the necessary information that mentioned the efficacy and adverse effects of the treatment in patients were considered for this review.

Results

In total, 43 manuscripts were selected after a strategic search, and these studies have been included in this systematic review. Most included studies reported the safety of the procedures used and the treatment's good tolerability, with mild adverse events such as fever, headache, mild pain at the injection site, or nausea being common. A few studies also reported death of some patients, attributed to the progression of the disease to severe stages before the treatment. Other severe events, such as respiratory or urinary infections reported in some studies, were not related to the treatment. Different parameters were used to evaluate the efficacy of the treatment based on the clinical condition of the patient.

Conclusion

Mesenchymal stem cells transplantation has so far proven to be safe and tolerable in select studies and patient types. This systematic review includes the results from the 43 selected studies in terms of safety and tolerability of the procedures, and several adverse events and therapeutic benefits during the follow-up period after administration of MSCs.

Transplantation of Heat-Shock Preconditioned Neural Stem/Progenitor Cells Combined with RGD-Functionalised Hydrogel Promotes Spinal Cord Functional Recovery in a Rat Hemi-Transection Model

BACKGROUND

Neural stem/progenitor cell (NSPC) transplantation in spinal cord injury (SCI) is a potential treatment that supports regeneration by promoting neuroprotection, remyelination, and neurite outgrowth. However, glial scarring hinders neuroregeneration and reduces the efficiency of cell transplantation. The present study aimed to enhance this neuroregeneration by surgically removing the glial scar and transplanting heat-shock (HS) preconditioned NSPCs in combination with Arg-Gly-Asp (RGD)-functionalised hydrogel in a rat spinal cord hemi-transection model.

METHODS

Twelve Sprague-Dawley rats underwent spinal cord hemi-transection and were randomly divided into three treatment groups: hydrogel implantation (control group), NSPC-encapsulated hydrogel implantation, and HS-NSPC-encapsulated hydrogel implantation. HS preconditioning was applied to the NSPCs to reinforce cell retention and an RGD-functionalised hydrogel was used as a biomatrix.

RESULTS

In vitro culture showed that preconditioned NSPCs highly differentiated into neurons and oligodendrocytes and exhibited higher proliferation and neurite outgrowth in hydrogels. Rats in the HS-NSPC-encapsulated hydrogel implantation group showed significantly improved functional recovery, neuronal and oligodendrocyte differentiation of transplanted cells, remyelination, and low fibrotic scar formation.

CONCLUSIONS

The surgical removal of the glial scar in combination with HS-preconditioning and RGD-functionalised hydrogels should be considered as a new paradigm in NSPC transplantation for spinal cord regeneration treatment.

Traumatic Human Spinal Cord Injury: Are Single Treatments Enough to Solve the Problem?

Traumatic spinal cord injury (SCI) results in partial or complete motor deficits, such as paraplegia, tetraplegia, and sphincter control, as well as sensory disturbances and autonomic dysregulation such as arterial hypotension, lack of sweating, and alterations in skin lability. All this has a strong psychological impact on the affected person and his/her family, as well as costs to healthcare institutions with an economic burden in the short, medium, and long terms. Despite at least forty years of experimental animal studies and several clinical trials with different therapeutic strategies, effective therapy is not universally accepted. Most of the published works on acute and chronic injury use a single treatment, such as medication, trophic factor, transplant of a cell type, and so on, to block some secondary injury mechanisms or promote some mechanisms of structural/functional restoration. However, despite significant results in experimental models, the outcome is a moderate improvement in muscle strength, sensation, or eventually in sphincter control, which has been considered non-significant in human clinical trials. Here we present a brief compilation of successful individual treatments that have been applied to secondary mechanisms of action. These studies show limited neuroprotective or neurorestorative approaches in animal models and clinical trials. Thus, the few benefits achieved so far represent a rationale to further explore other strategies that seek better structural and functional restoration of the injured spinal cord.

Mesenchymal Stem Cell Transplantation: Neuroprotection and Nerve Regeneration After Spinal Cord Injury

Spinal Cord Injury (SCI), with its morbidity characteristics of high disability rate and high mortality rate, is a disease that is highly destructive to both the physiology and psychology of the patient, and for which there is still a lack of effective treatment. Following spinal cord injury, a cascade of secondary injury reactions known as ischemia, peripheral inflammatory cell infiltration, oxidative stress, etc. create a microenvironment that is unfavorable to neural recovery and ultimately results in apoptosis and necrosis of neurons and glial cells. Mesenchymal stem cell (MSC) transplantation has emerged as a more promising therapeutic options in recent years. MSC can promote spinal cord injury repair through a variety of mechanisms, including immunomodulation, neuroprotection, and nerve regeneration, giving patients with spinal cord injury hope. In this paper, it is discussed the neuroprotection and nerve regeneration components of MSCs' therapeutic method for treating spinal cord injuries.

Breaking the graft-versus-host-disease barrier: Mesenchymal stromal/stem cells as precision healers

Mesenchymal Stromal/Stem Cells (MSCs) are multipotent, non-hematopoietic progenitor cells with a wide range of immune modulation and regenerative potential which qualify them as a potential component of cell-based therapy for various autoimmune/chronic inflammatory ailments. Their immunomodulatory properties include the secretion of immunosuppressive cytokines, the ability to suppress T-cell activation and differentiation, and the induction of regulatory T-cells. Considering this and our interest, we here discuss the significance of MSC for the management of Graft-versus-Host-Disease (GvHD), one of the autoimmune manifestations in human. In pre-clinical models, MSCs have been shown to reduce the severity of GvHD symptoms, including skin and gut damage, which are the most common and debilitating manifestations of this disease. While initial clinical studies of MSCs in GvHD cases were promising, the results were variable in randomized studies. So, further studies are warranted to fully understand their potential benefits, safety profile, and optimal dosing regimens. Owing to these inevitable issues, here we discuss various mechanisms, and how MSCs can be employed in managing GvHD, as a cellular therapeutic approach for this disease.

How can clinical safety and efficacy concerns in stem cell therapy for spinal cord injury be overcome?

INTRODUCTION

Spinal cord injury (SCI) can lead to severe neurological dysfunction. Despite scientific and medical advances, clinically effective regenerative therapies including stem cells are lacking for SCI.

AREAS COVERED

This paper discusses translational challenges related to the safe, effective use of stem cells for SCI, with a focus on mesenchymal stem cells (MSCs), neural stem cells (NSCs), Schwann cells (SCs), olfactory ensheathing cells (OECs), oligodendrocyte precursor cells (OPCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iPSCs). We discuss approaches to enhance the efficacy of cell-based strategies by i) addressing patient heterogeneity and enhancing patient selection; ii) selecting cell type, cell source, cell developmental stage, and delivery technique; iii) enhancing graft integration and mitigating immune-mediated graft rejection; and iv) ensuring availability of cells. Additionally, we review strategies to optimize outcomes including combinatorial use of rehabilitation and discuss ways to mitigate potential risks of tumor formation associated with stem cell-based strategies.

EXPERT OPINION

Basic science research will drive translational advances to develop stem cell-based therapies for SCI. Genetic, serological, and imaging biomarkers may enable individualization of cell-based treatments. Moreover, combinatorial strategies will be required to enhance graft survival, migration and functional integration, to enable precision-based intervention.

Mesenchymal Stem Cells: Generalities and Clinical Significance in Feline and Canine Medicine

Mesenchymal stem cells (MSCs) are multipotent cells: they can proliferate like undifferentiated cells and have the ability to differentiate into different types of cells. A considerable amount of research focuses on the potential therapeutic benefits of MSCs, such as cell therapy or tissue regeneration, and MSCs are considered powerful tools in veterinary regenerative medicine. They are the leading type of adult stem cells in clinical trials owing to their immunosuppressive, immunomodulatory, and anti-inflammatory properties, as well as their low teratogenic risk compared with pluripotent stem cells. The present review details the current understanding of the fundamental biology of MSCs. We focus on MSCs' properties and their characteristics with the goal of providing an overview of therapeutic innovations based on MSCs in canines and felines.

Macromolecule-based hydrogels nanoarchitectonics with mesenchymal stem cells for regenerative medicine: A review

The role of regenerative medicine in clinical therapies is becoming increasingly vital. Under specific conditions, mesenchymal stem cells (MSCs) are capable of differentiating into mesoblastema (i.e., adipocytes, chondrocytes, and osteocytes) and other embryonic lineages. Their application in regenerative medicine has attracted a great deal of interest among researchers. To maximize the potential applications of MSCs, materials science could provide natural extracellular matrices and provide an effective means to understand the various mechanisms of differentiation for the growth of MSCs. Pharmaceutical fields are represented among the research on biomaterials by macromolecule-based hydrogel nanoarchitectonics. Various biomaterials have been used to prepare hydrogels with their unique chemical and physical properties to provide a controlled microenvironment for the culture of MSCs, laying the groundwork for future practical applications in regenerative medicine. This article currently describes and summarizes the sources, characteristics, and clinical trials of MSCs. In addition, it describes the differentiation of MSCs in various macromolecule-based hydrogel nanoarchitectonics and highlights the preclinical studies of MSCs-loaded hydrogel materials in regenerative medicine conducted over the past few years. Finally, the challenges and prospects of MSC-loaded hydrogels are discussed, and the future development of macromolecule-based hydrogel nanoarchitectonics is outlined by comparing the current literature.

Recent advances in the combination of cellular therapy with stem cells and nanoparticles after a spinal cord injury

Background

Currently, combined therapies could help to reduce long-term sequelae of spinal cord injury (SCI); stem cell therapy at the site of injury in combination with other therapies has shown very promising results that can be transferred to the clinical field. Nanoparticles (NPs) are versatile technologies with applications to medical research for treatments of SCI since they could deliver therapeutic molecules to the target tissue and may help to reduce the side effects of non-targeted therapies. This article's purpose is to analyze and concisely describe the diverse cellular therapies in combination with NPs and their regenerative effect after SCI.

Methods

We reviewed the literature related to combinatory therapy for motor impairment following SCI that has been published by Web of Science, Scopus, EBSCO host, and PubMed databases. The research covers the databases from 2001 to December 2022.

Result

Animal models of SCI have shown that the combination of NPs plus stem cells has a positive impact on neuroprotection and neuroregeneration. Further research is required to better understand the effects and benefits of SCI on a clinical level; therefore, it is necessary to find and select the most effective molecules that are capable of exacerbating the neurorestorative effects of the different stem cells and then try them out on patients after SCI. On the other hand, we consider that synthetic polymers such as poly [lactic-co-glycolic acid] (PLGA) could be a candidate for the design of the first therapeutic strategy that combines NPs with stem cells in patients with SCI. The reasons for the selection are that PLGA has shown important advantages over other NPs, such as being biodegradable, having low toxicity levels, and high biocompatibility; In addition, researchers could control the release time and the biodegradation kinetics, and most importantly, it could be used as NMs on other clinical pathologies (12 studies on www.clinicaltrials.gov) and has been approved by the Federal Food, Drug, and Cosmetic Act (FDA).

Conclusion

The use of cellular therapy and NPs may be a worthwhile alternative for SCI therapy; however, it is expected that the data obtained from interventions after SCI reflect an important variability of molecules combined with NPs. Therefore, it is necessary to properly define the limits of this research to be able to continue to work on the same line. Consequently, the selection of a specific therapeutic molecule and type of NPs plus stem cells are crucial to evaluate its application in clinical trials.

Multipotent Mesenchymal Stem Cell-Based Therapies for Spinal Cord Injury: Current Progress and Future Prospects

Spinal cord injury (SCI) represents a significant medical challenge, often resulting in permanent disability and severely impacting the quality of life for affected individuals. Traditional treatment options remain limited, underscoring the need for novel therapeutic approaches. In recent years, multipotent mesenchymal stem cells (MSCs) have emerged as a promising candidate for SCI treatment due to their multifaceted regenerative capabilities. This comprehensive review synthesizes the current understanding of the molecular mechanisms underlying MSC-mediated tissue repair in SCI. Key mechanisms discussed include neuroprotection through the secretion of growth factors and cytokines, promotion of neuronal regeneration via MSC differentiation into neural cell types, angiogenesis through the release of pro-angiogenic factors, immunomodulation by modulating immune cell activity, axonal regeneration driven by neurotrophic factors, and glial scar reduction via modulation of extracellular matrix components. Additionally, the review examines the various clinical applications of MSCs in SCI treatment, such as direct cell transplantation into the injured spinal cord, tissue engineering using biomaterial scaffolds that support MSC survival and integration, and innovative cell-based therapies like MSC-derived exosomes, which possess regenerative and neuroprotective properties. As the field progresses, it is crucial to address the challenges associated with MSC-based therapies, including determining optimal sources, intervention timing, and delivery methods, as well as developing standardized protocols for MSC isolation, expansion, and characterization. Overcoming these challenges will facilitate the translation of preclinical findings into clinical practice, providing new hope and improved treatment options for individuals living with the devastating consequences of SCI.

Current progress of mesenchymal stem cell membrane-camouflaged nanoparticles for targeted therapy

Nanodrug delivery systems have been widely used in disease treatment. However, weak drug targeting, easy to be cleared by the immune system, and low biocompatibility are great obstacles for drug delivery. As an important part of cell information transmission and behavior regulation, cell membrane can be used as drug coating material which represents a promising strategy and can overcome these limitations. Mesenchymal stem cell (MSC) membrane, as a new carrier, has the characteristics of active targeting and immune escape of MSC, and has broad application potential in tumor treatment, inflammatory disease, tissue regeneration and other fields. Here, we review recent progress on the use of MSC membrane-coated nanoparticles for therapy and drug delivery, aiming to provide guidance for the design and clinical application of membrane carrier in the future.

Clinical Trials Targeting Secondary Damage after Traumatic Spinal Cord Injury

Spinal cord injury (SCI) often causes loss of sensory and motor function resulting in a significant reduction in quality of life for patients. Currently, no therapies are available that can repair spinal cord tissue. After the primary SCI, an acute inflammatory response induces further tissue damage in a process known as secondary injury. Targeting secondary injury to prevent additional tissue damage during the acute and subacute phases of SCI represents a promising strategy to improve patient outcomes. Here, we review clinical trials of neuroprotective therapeutics expected to mitigate secondary injury, focusing primarily on those in the last decade. The strategies discussed are broadly categorized as acute-phase procedural/surgical interventions, systemically delivered pharmacological agents, and cell-based therapies. In addition, we summarize the potential for combinatorial therapies and considerations.

Hydrogen Promotes the Effectiveness of Bone Mesenchymal Stem Cell Transplantation in Rats with Spinal Cord Injury

Although bone mesenchymal stem cell (BMSC) transplantation has been applied to the treatment of spinal cord injury (SCI), the effect is unsatisfactory due to the specific microenvironment (inflammation and oxidative stress) in the SCI area, which leads to the low survival rate of transplanted cells. Thus, additional strategies are required to improve the efficacy of transplanted cells in the treatment of SCI. Hydrogen possesses antioxidant and anti-inflammatory properties. However, whether hydrogen can enhance the effect of BMSC transplantation in the treatment of SCI has not yet been reported. This study was aimed at investigating whether hydrogen promotes the therapeutic effect of BMSC transplantation in the treatment of SCI in rats. In vitro, BMSCs were cultured in a normal medium and a hydrogen-rich medium to study the effect of hydrogen on the proliferation and migration of BMSCs. BMSCs were treated with a serum-deprived medium (SDM), and the effects of hydrogen on the apoptosis of BMSCs were studied. In vivo, BMSCs were injected into the rat model of SCI. Hydrogen-rich saline (5 ml/kg) and saline (5 ml/kg) were given once a day via intraperitoneal injection. Neurological function was evaluated using the Basso, Beattie, and Bresnahan (BBB) and CatWalk gait analyses. Histopathological analysis, oxidative stress, inflammatory factors (TNF-α, IL-1β, and IL-6), and transplanted cell viability were detected at 3 and 28 days after SCI. Hydrogen can significantly enhance BMSC proliferation and migration and tolerance to SDM. Hydrogen and BMSC codelivery can significantly enhance neurological function recovery by improving the transplant cell survival rate and migration. Hydrogen can enhance the migration and proliferation capacity of BMSCs to repair SCI by reducing the inflammatory response and oxidative stress in the injured area. Hydrogen and BMSC codelivery is an effective method to improve BMSC transplantation in the treatment of SCI.

Therapeutic Efficacy of Human Mesenchymal Stem Cells With Different Delivery Route and Dosages in Rat Models of Spinal Cord Injury

Recent studies have shown that the use of mesenchymal stem/stromal cells (MSCs) may be a promising strategy for treating spinal cord injury (SCI). This study aimed to explore the effectiveness of human umbilical cord-derived MSCs (hUC-MSCs) with different administration routes and dosages on SCI rats. Following T10-spinal cord contusion in Sprague-Dawley rats (N = 60), three different dosages of hUC-MSCs were intrathecally injected into rats (SCI-ITH) after 24 h. Intravenous injection of hUC-MSCs (SCI-i.v.) and methylprednisolone reagent (SCI-PC) were used as positive controls (N = 10/group). A SCI control group without treatment and a sham operation group were injected with Multiple Electrolyte Injection solution. The locomotor function was assessed by Basso Beattie Bresnahan (BBB) rating score, magnetic resonance imaging (MRI), histopathology, and immunofluorescence. ELISA was conducted to further analyze the nerve injury and inflammation in the rat SCI model. Following SCI, BBB scores were significantly lower in the SCI groups compared with the sham operation group, but all the treated groups showed the recovery of hind-limb motor function, and rats receiving the high-dose intrathecal injection of hUC-MSCs (SCI-ITH-H) showed improved outcomes compared with rats in hUC-MSCs i.v. and positive control groups. Magnetic resonance imaging revealed significant edema and spinal cord lesion in the SCI groups, and significant recovery was observed in the medium and high-dose hUC-MSCs ITH groups. Histopathological staining showed that the necrotic area in spinal cord tissue was significantly reduced in the hUC-MSCs ITH-H group, and the immunofluorescence staining confirmed the neuroprotection effect of hUC-MSCs infused on SCI rats. The increase of inflammatory cytokines was repressed in hUC-MSCs ITH-H group. Our results confirmed that hUC-MSC administered via intrathecal injection has dose-dependent neuroprotection effect in SCI rats.

Integrated Neuroregenerative Techniques for Plasticity of the Injured Spinal Cord

On the slow path to improving the life expectancy and quality of life of patients post spinal cord injury (SCI), recovery remains controversial. The potential role of the regenerative capacity of the nervous system has led to numerous attempts to stimulate the SCI to re-establish the interrupted sensorimotor loop and to understand its potential in the recovery process. Numerous resources are now available, from pharmacological to biomolecular approaches and from neuromodulation to sensorimotor rehabilitation interventions based on the use of various neural interfaces, exoskeletons, and virtual reality applications. The integration of existing resources seems to be a promising field of research, especially from the perspective of improving living conditions in the short to medium term. Goals such as reducing chronic forms of neuropathic pain, regaining control over certain physiological activities, and enhancing residual abilities are often more urgent than complete functional recovery. In this perspective article, we provide an overview of the latest interventions for the treatment of SCI through broad phases of injury rehabilitation. The underlying intention of this work is to introduce a spinal cord neuroplasticity-based multimodal approach to promote functional recovery and improve quality of life after SCI. Nonetheless, when used separately, biomolecular therapeutic approaches have been shown to have modest outcomes.

Cultivation of Cryopreserved Human Dental Pulp Stem Cells—A New Approach to Maintaining Dental Pulp Tissue

Human dental pulp stem cells (hDPSCs) are multipotent mesenchymal stem cells (MSCs) that are capable of self-renewal with multilineage differentiation potential. After being cryopreserved, hDPSCs were reported to maintain a high level of proliferation and multi-differentiation abilities. In order to optimize cryopreservation techniques, decrease storage requirements and lower contamination risks, the feasibility of new whole-tooth cryopreservation and its effects on hDPSCs were tested. The survival rates, morphology, proliferation rates, cell activity, surface antigens and differentiation abilities of hDPSCs isolated from fresh teeth were compared with those of one-month cryopreserved teeth in 5% and 10% DMSO. The data of the present study indicated that the new cryopreservation approach did not reduce the capabilities or stemness of hDPSCs, with the exception that it extended the first appearance time of hDPSCs in the teeth that were cryopreserved in 10% DMSO, and reduced their recovery rate. With the novel strategy of freezing, the hDPSCs still expressed the typical surface markers of MSCs and maintained excellent proliferation capacity. Three consecutive weeks of osteogenic and adipogenic induction also showed that the expression of the key genes in hDPSCs, including lipoprotein lipase (LPL), peroxisome proliferator-activated receptor-γ (PPAR-γ), alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), type I collagen (COL I) and osteocalcin (OSC) was not affected, indicating that their differentiation abilities remained intact, which are crucial parameters for hDPSCs as cell-therapy candidates. These results demonstrated that the new cryopreservation method is low-cost and effective for the good preservation of hDPSCs without compromising cell performance, and can provide ideas and evidence for the future application of stem-cell therapies and the establishment of dental banks.

Multimodal Repair of Spinal Cord Injury With Mesenchymal Stem Cells

Spinal cord injury (SCI) is a result of a devastating injury to the central nervous system. Currently, there is no effective treatment available for these patients. The possible use of mesenchymal stem cell (MSC)-based treatment for SCI has been the focus of extensive investigations and is increasingly moving from the bench to bedside. Both experimental observations and clinical studies have shown the safety and efficacy of MSCs in managing SCI. However, the exact mechanism by which MSCs contribute to the repair of the injured spinal cord remains to be elucidated. In this review, we aim to summarize current research findings about the role of MSCs in improving complex pathology after SCI. MSCs exert a multimodal repair mechanism targeting multiple events in the secondary injury cascade. Our recent results showing the perineurium-like differentiation of surviving MSCs in the injured spinal cord may further the understanding of the fate of transplanted MSCs. These findings provide fundamental support for the clinical use of MSCs in SCI patients. Under experimental conditions, combining novel physical, chemical, and biological approaches led to significant improvements in the therapeutic efficacy of MSCs. These findings hold promise for the future of cell-based clinical treatment of SCI.

Recent Advances in Cell and Functional Biomaterial Treatment for Spinal Cord Injury

Spinal cord injury (SCI) is a devastating central nervous system disease caused by accidental events, resulting in loss of sensory and motor function. Considering the multiple effects of primary and secondary injuries after spinal cord injury, including oxidative stress, tissue apoptosis, inflammatory response, and neuronal autophagy, it is crucial to understand the underlying pathophysiological mechanisms, local microenvironment changes, and neural tissue functional recovery for preparing novel treatment strategies. Treatment based on cell transplantation has become the forefront of spinal cord injury therapy. The transplanted cells provide physical and nutritional support for the damaged tissue. At the same time, the implantation of biomaterials with specific biological functions at the site of the SCI has also been proved to improve the local inhibitory microenvironment and promote axonal regeneration, etc. The combined transplantation of cells and functional biomaterials for SCI treatment can result in greater neuroprotective and regenerative effects by regulating cell differentiation, enhancing cell survival, and providing physical and directional support for axon regeneration and neural circuit remodeling. This article reviews the pathophysiology of the spinal cord, changes in the microenvironment after injury, and the mechanisms and strategies for spinal cord regeneration and repair. The article will focus on summarizing and discussing the latest intervention models based on cell and functional biomaterial transplantation and the latest progress in combinational therapies in SCI repair. Finally, we propose the future prospects and challenges of current treatment regimens for SCI repair, to provide references for scientists and clinicians to seek better SCI repair strategies in the future.

Combination Therapy Using Nanomaterials and Stem Cells to Treat Spinal Cord Injuries

As a part of the central nervous system, the spinal cord (SC) provides most of the communications between the brain and other parts of the body. Any damage to SC interrupts this communication, leading to serious problems, which may remain for the rest of their life. Due to its significant impact on patients' quality of life and its exorbitant medical costs, SC injury (SCI) is known as one of the most challengeable diseases in the world. Thus, it is critical to introduce highly translatable therapeutic platforms for SCI treatment. So far, different strategies have been introduced, among which utilizing various types of stem cells is one of the most interesting ones. The capability of stem cells to differentiate into several types of cell lines makes them promising candidates for the regeneration of injured tissues. One of the other interesting and novel strategies for SCI treatment is the application of nanomaterials, which could appear as a carrier for therapeutic agents or as a platform for culturing the cells. Combining these two approaches, stem cells and nanomaterials, could provide promising therapeutic strategies for SCI management. Accordingly, in this review we have summarized some of the recent advancements in which the applications of different types of stem cells and nanomaterials, alone and in combination forms, were evaluated for SCI treatment.

Human Adipose-Derived Stem Cells Combined with Nano-Hydrogel Promote Functional Recovery after Spinal Cord Injury in Rats

Simple Summary

Nerve regeneration and functional recovery after spinal cord injury (SCI) are worldwide problems. Scientists have achieved encouraging results in the repair of spinal cord injuries using natural or synthetic materials. In this paper, we report that nano-hydrogel combined with human adipose-derived stem cells regulate the inflammatory microenvironment, protect neurons and axons, and promote motor function recovery. In addition, three proteins related to neuronal and axonal growth were screened by Liquid chromatography-mass spectrometry. These results provide evidence for clinical treatment of spinal cord injury.

Abstract

The treatment of spinal cord injury aims to reconstruct the fiber connection and restore the interrupted neural pathways. Adipose mesenchymal stem cells (ADSCs) can promote the recovery of motor functions in spinal cord injury. However, poor survival of ADSCs and leakage outside of the injury site after local transplantation reduce the number of cells, which seriously attenuates the cumulative effect. We performed heterotopic transplantation on rats with severe spinal cord injury using human ADSCs loaded within self-assembly hydrogel RADA16-RGD (R: arginine; A: alanine; D: aspartic acid; G: glycine). Our results indicate that the combined transplantation of human ADSCs with RADA16-RGD improved the survival of ADSCs at the injured site. The inflammatory reaction was inhibited, with improved survival of the neurons and increased residual area of nerve fibers and myelin protein. The functional behaviors were promoted, as determined by the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale score and electrophysiological measurements. ADSCs can promote the repair of spinal cord injury. This study provides new ideas for the treatment of spinal cord injury.

Curcumin Improves Human Umbilical Cord-Derived Mesenchymal Stem Cell Survival via ERK1/2 Signaling and Promotes Motor Outcomes After Spinal Cord Injury

Human umbilical cord-derived mesenchymal stem cell (hUC-MSC) transplantation is thought to be a promising strategy for treating spinal cord injury (SCI). However, the low survival rate of transplanted hUC-MSCs limits their clinical application in cell replacement therapy. Curcumin can suppress inflammation after SCI; however, it remains unknown whether curcumin can modulate the survival of transplanted hUC-MSCs. In this study, to investigate whether curcumin could strengthen the therapeutic effects of hUC-MSC transplantation on SCI, we induced hUC-MSC apoptosis with TNF-α, transplanted hUC-MSC into SCI rats, and assessed the antiapoptotic effect and mechanism of curcumin. LDH release analysis and flow cytometry demonstrated that TNF-α led to hUC-MSC apoptosis and that curcumin increased the hUC-MSC survival rate in a dose-dependent manner. In addition, we showed that the phosphorylation levels of ERK1/2, JNK, and P38 were upregulated in apoptotic hUC-MSCs, while curcumin increased the phosphorylation of ERK1/2 but did not activate JNK or P38, and these effects were reversed by the p42/44 antagonist U0126. Furthermore, we found that the motor function scores and number of surviving HNA-positive cells were significantly increased after curcumin and hUC-MSC transplantation therapy 8 weeks post-SCI, while U0126 markedly attenuated these effects. These data confirmed that curcumin suppressed hUC-MSC apoptosis through the ERK1/2 signaling pathway and that combined curcumin and hUC-MSC treatment improved motor function in rats after SCI. The current research provides a strong basis for hUC-MSC replacement therapy in conjunction with curcumin in the treatment and management of SCI in humans.

A systematic review of large animal and human studies of stem cell therapeutics for acute adult traumatic spinal cord injury

Background: Traumatic spinal cord injury (TSCI) is a devastating condition and the search for a cure remains one of the most tenacious healthcare challenges to date. Current therapies are limited in their efficacy to restore full neurological function – resulting in lifelong disability and loss of autonomy. Whilst there remains a necessity to refine therapeutic protocols, stem cell (SC) studies have shown promise in the mending and re-establishment of the spinal cord neuroanatomy. Objectives: We conducted a systematic review of functional outcomes in stem cell therapeutics over the last three decades in large animals and humans. Methods: Medline, Embase, Cochrane and SCOPUS databases were searched for potentially pertinent articles from 1990 to 2020. Studies published in English were included if the stem cells were directly injected into the intraspinal, epidural or intrathecal compartments within two weeks of a traumatic mechanism of injury, including acute intervertebral disc prolapse. The participants were either large animals – defined as canine, porcine or non-human primate in-vivo models – or human patients. Results: Nine studies were included in this review. Statistically significant improvements in motor function and deep pain perception were seen at 8 weeks to 6 months post-SC injection compared to controls. Limitations: Functional outcomes are variably measured across studies. Almost all studies used experimentally induced trauma, which may not accurately represent the complexity of human spinal cord injury. Due to the exclusion criteria, there were no non-human primate studies included, yet these animal models are considered a closer anatomical match to humans than other large mammals. No human studies were included. Conclusions and Implications: Autologous and allogeneic stem cells have been trialled for the reconstitution of damaged and lost cells, remyelination of axons and remodelling of the pathophysiological microenvironment within the injured spinal cord, with some promising outcome data. This may translate to more successful future Phase I/II human clinical trials into the use of stem cells after TSCI in adults.

Design and Fabrication of Polymeric Hydrogel Carrier for Nerve Repair

Nerve regeneration and repair still remain a huge challenge for both central nervous and peripheral nervous system. Although some therapeutic substances, including neuroprotective agents, clinical drugs and stem cells, as well as various growth factors, are found to be effective to promote nerve repair, a carrier system that possesses a sustainable release behavior, in order to ensure high on-site concentration during the whole repair and regeneration process, and high bioavailability is still highly desirable. Hydrogel, as an ideal delivery system, has an excellent loading capacity and sustainable release behavior, as well as tunable physical and chemical properties to adapt to various biomedical scenarios; thus, it is thought to be a suitable carrier system for nerve repair. This paper reviews the structure and classification of hydrogels and summarizes the fabrication and processing methods that can prepare a suitable hydrogel carrier with specific physical and chemical properties. Furthermore, the modulation of the physical and chemical properties of hydrogels is also discussed in detail in order to obtain a better therapeutic effect to promote nerve repair. Finally, the future perspectives of hydrogel microsphere carriers for stroke rehabilitation are highlighted.

Progression in translational research on spinal cord injury based on microenvironment imbalance

Spinal cord injury (SCI) leads to loss of motor and sensory function below the injury level and imposes a considerable burden on patients, families, and society. Repair of the injured spinal cord has been recognized as a global medical challenge for many years. Significant progress has been made in research on the pathological mechanism of spinal cord injury. In particular, with the development of gene regulation, cell sequencing, and cell tracing technologies, in-depth explorations of the SCI microenvironment have become more feasible. However, translational studies related to repair of the injured spinal cord have not yielded significant results. This review summarizes the latest research progress on two aspects of SCI pathology: intraneuronal microenvironment imbalance and regenerative microenvironment imbalance. We also review repair strategies for the injured spinal cord based on microenvironment imbalance, including medications, cell transplantation, exosomes, tissue engineering, cell reprogramming, and rehabilitation. The current state of translational research on SCI and future directions are also discussed. The development of a combined, precise, and multitemporal strategy for repairing the injured spinal cord is a potential future direction.

Clinical Trials Using Mesenchymal Stem Cells for Spinal Cord Injury: Challenges in Generating Evidence

Spinal cord injury (SCI) remains an important public health problem which often causes permanent loss of muscle strength, sensation, and function below the site of the injury, generating physical, psychological, and social impacts throughout the lives of the affected individuals, since there are no effective treatments available. The use of stem cells has been investigated as a therapeutic approach for the treatment of SCI. Although a significant number of studies have been conducted in pre-clinical and clinical settings, so far there is no established cell therapy for the treatment of SCI. One aspect that makes it difficult to evaluate the efficacy is the heterogeneity of experimental designs in the clinical trials that have been published. Cell transplantation methods vary widely among the trials, and there are still no standardized protocols or recommendations for the therapeutic use of stem cells in SCI. Among the different cell types, mesenchymal stem/stromal cells (MSCs) are the most frequently tested in clinical trials for SCI treatment. This study reviews the clinical applications of MSCs for SCI, focusing on the critical analysis of 17 clinical trials published thus far, with emphasis on their design and quality. Moreover, it highlights the need for more evidence-based studies designed as randomized controlled trials and potential challenges to be addressed in context of stem cell therapies for SCI.

Human Epidural AD–MSC Exosomes Improve Function Recovery after Spinal Cord Injury in Rats

Spinal cord injury (SCI) interferes with the normal function of the autonomic nervous system by blocking circuits between the sensory and motor nerves. Although many studies focus on functional recovery after neurological injury, effective neuroregeneration is still being explored. Recently, extracellular vesicles such as exosomes have emerged as cell-free therapeutic agents owing to their ability of cell-to-cell communication. In particular, exosomes released from mesenchymal stem cells (MSCs) have the potential for tissue regeneration and exhibit therapeutic effectiveness in neurological disorders. In this study, we isolated exosomes from human epidural adipose tissue-derived MSCs (hEpi AD–MSCs) using the tangential flow filtration method. The isolated exosomes were analyzed for size, concentration, shape, and major surface markers using nanoparticle tracking analysis, transmission electron microscopy, and flow cytometry. To evaluate their effect on SCI recovery, hEpi AD–MSC exosomes were injected intravenously in SCI-induced rats. hEpi AD–MSC exosomes improved the locomotor function of SCI-induced rats. The results of histopathological and cytokine assays showed that hEpi AD–MSC exosomes regulated inflammatory response. Genetic profiling of the rat spinal cord tissues revealed changes in the expression of inflammation-related genes after exosome administration. Collectively, hEpi AD–MSC exosomes are effective in restoring spinal functions by reducing the inflammatory response.

Spinal Cord Injury: A Systematic Review and Network Meta-Analysis of Therapeutic Strategies Based on 15 Types of Stem Cells in Animal Models

Objective: The optimal therapeutic strategies of stem cells for spinal cord injury (SCI) are fully explored in animal studies to promote the translation of preclinical findings to clinical practice, also to provide guidance for future animal experiments and clinical studies.

Methods: PubMed, Web of Science, Embase, CNKI, Wangfang, VIP, and CBM were searched from inception to September 2021. Screening of search results, data extraction, and references quality evaluation were undertaken independently by two reviewers.

Results and Discussion: A total of 188 studies were included for data analysis. Results of traditional meta-analysis showed that all 15 diverse types of stem cells could significantly improve locomotor function of animals with SCI, and results of further network meta-analysis showed that adipose-derived mesenchymal stem cells had the greatest therapeutic potential for SCI. Moreover, a higher dose (≥1 × 106) of stem cell transplantation had better therapeutic effect, transplantation in the subacute phase (3–14 days, excluding 3 days) was the optimal timing, and intralesional transplantation was the optimal route. However, the evidence of current animal studies is of limited quality, and more high-quality research is needed to further explore the optimal therapeutic strategies of stem cells, while the design and implementation of experiments, as well as measurement and reporting of results for animal studies, need to be further improved and standardized to reduce the risk when the results of animal studies are translated to the clinic.

Systematic Review Registration: [website], identifier [registration number].

When stem cells meet COVID-19: recent advances, challenges and future perspectives

Coronavirus disease 2019 (COVID-19) caused by the novel severe acute respiratory coronavirus 2 is currently spreading throughout the world with a high rate of infection and mortality and poses a huge threat to global public health. COVID-19 primarily manifests as hypoxic respiratory failure and acute respiratory distress syndrome, which can lead to multiple organ failure. Despite advances in the supportive care approaches, there is still a lack of clinically effective therapies, and there is an urgent need to develop novel strategies to fight this disease. Currently, stem cell therapy and stem cell-derived organoid models have received extensive attention as a new treatment and research method for COVID-19. Here, we discuss how stem cells play a role in the battle against COVID-19 and present a systematic review and prospective of the study on stem cell treatment and organoid models of COVID-19, which provides a reference for the effective control of the COVID-19 pandemic worldwide.

OUP accepted manuscript

Traumatic injury of the central nervous system (CNS) is a worldwide health problem affecting millions of people. Trauma of the CNS, that is, traumatic brain injury (TBI) and spinal cord injury (SCI), lead to massive and progressive cell loss and axonal degeneration, usually with very limited regeneration. At present, there are no treatments to protect injured CNS tissue or to replace the lost tissue. Stem cells are a cell type that by definition can self-renew and give rise to multiple cell lineages. In recent years, therapies using stem and progenitor cells have shown promising effects in experimental CNS trauma, particularly in the acute-subacute stage, but also in chronic injuries. However, the therapeutic mechanisms by which transplanted cells achieve the structural and/or functional improvements are often not clear. Stem cell therapies for CNS trauma can be categorized into 2 main concepts, transplantation of exogenous neural stem cells and neural progenitor cells and recruitment of endogenous stem and progenitor cells. In this review, focusing on the advances during the last decade, we will discuss the major cell therapies, the pros and cons of these 2 concepts for TBI and SCI, and the treatment strategies we believe will be successful.

Study of the Diffusion Tensor Imaging for Preclinical Therapeutic Efficacy of Umbilical Cord Mesenchymal Stem Cell Transplantation in the Treatment of Spinal Cord Injury

Objective

In this study, umbilical cord mesenchymal stem cell (UC-MSC) transplantation was used to treat patients with spinal cord injury (SCI). The microstructural changes of the spinal cord before and after transplantation were observed by diffusion tensor imaging (DTI).

Methods

From January 2014 to May 2015, seven patients who met the inclusion criteria were enrolled in this study. In the experimental group, both UC-MSC transplantation and comprehensive rehabilitation treatment were applied, while the control group received only comprehensive rehabilitation treatment. American Spinal Injury Association (ASIA) sensory and motor scores and the degree of SCI, spasticity, and urine/defecation functions were measured and evaluated together with DTI before the treatment and again at two and six months after the first treatment.

Results

From the DTI, the changes in the fractional anisotropy (FA) value and the apparent diffusion coefficient (ADC) value were as follows: in the experimental group, there were significant differences in the FA and ADC values before and after treatment (P < 0.05) with a decreased ADC value and an increased FA value. The differences in the ADC and FA values of the normal layer and the lesion layer before and after treatment were compared. The differences in ADC and FA at the lesion layer before and after transplantation were greater than those of the normal layer, and the differences were statistically significant (P < 0.05). In the experimental group, one patient with incomplete SCI and one patient with a short course of complete SCI improved in terms of light touch, acupuncture sensation, and motor score. One patient with incomplete SCI achieved improvement in spasticity and urine/defecation functions.

Conclusion

The combination of UC-MSC transplantation and comprehensive rehabilitation therapy could help to promote the structural repair of the spinal nerve in patients with SCI.

Application and progress of three-dimensional bioprinting in spinal cord injury

Spinal cord injury (SCI) is a central nervous system disorder that can lead to sensory and motor dysfunction, which can seriously increase pressure and economic burden on families and societies. The current SCI treatment is mainly to stabilize the spine, prevent secondary damage, and control inflammation. Drug treatment is limited to early, large-scale use of steroids to reduce the effects of edema after SCI. In short, there is no direct treatment for SCI. Recent 3D bioprinting development provides a new solution for SCI treatment: a series of spinal cord bionic scaffolds are being developed to improve spinal cord function after injury. This paper reviews the pathophysiological characteristics of SCI, current treatment methods, and the progress of 3D bioprinting in SCI. Finally, its challenges and prospects in SCI treatment are summarized.

Therapeutic effects of stem cells in different body systems, a novel method that is yet to gain trust: A comprehensive review

Stem cell therapy has been used to treat several types of diseases, and it is expected that its therapeutic uses shall increase as novel lines of evidence begin to appear. Furthermore, stem cells have the potential to make new tissues and organs. Thus, some scientists propose that organ transplantation will significantly rely on stem cell technology and organogenesis in the future. Stem cells and its robust potential to differentiate into specific types of cells and regenerate tissues and body organs, have been investigated by numerous clinician scientists and researchers for their therapeutic effects. Degenerative diseases in different organs have been the main target of stem cell therapy. Neurodegenerative diseases such as Alzheimer's, musculoskeletal diseases such as osteoarthritis, congenital cardiovascular diseases, and blood cell diseases such as leukemia are among the health conditions that have benefited from stem cell therapy advancements. One of the most challenging parts of the process of incorporating stem cells into clinical practice is controlling their division and differentiation potentials. Sometimes, their potential for  uncontrolled growth will make these cells tumorigenic. Another caveat in this process is the ability to control the differentiation process. While stem cells can easily differentiate into a wide variety of cells,  a paracrine effect controlled activity, being in an appropriate medium will cause abnormal differentiation leading to treatment failure. In this review, we aim to provide an overview of the therapeutic effects of stem cells in diseases of various organ systems. In order to advance this new treatment to its full potential, researchers should focus on establishing methods to control the differentiation process, while policymakers should take an active role in providing adequate facilities and equipment for these projects. Large population clinical trials are a necessary tool that will help build trust in this method. Moreover, improving social awareness about the advantages and adverse effects of stem cell therapy is required to develop a rational demand in the society, and consequently, healthcare systems should consider established stem cell-based therapeutic methods in their treatment algorithms.

Diamond Concept as Principle for the Development of Spinal Cord Scaffold: A Literature Review

INTRODUCTION: Spinal cord injury (SCI) has been bringing detrimental impacts on the affected individuals. However, not only that, it also brings a tremendous effect on the socioeconomic and health-care system. Treatment regimen and strategy for SCI patient have been under further research. DISCUSSION: The main obstacles of regeneration on neuronal structure are the neuroinflammatory process and poor debris clearance, causing a longer healing process and an extensive inflammation process due to this particular inflammatory process. To resolve all of the mentioned significant issues in SCIs neuronal regeneration, a comprehensive model is necessary to analyze each step of progressive condition in SCI. In this review, we would like to redefine a comprehensive concept of the “Diamond Concept” from previously used in fracture management to SCI management, which consists of cellular platform, cellular inductivity, cellular conductivity, and material integrity. The scaffolding treatment strategy for SCI has been widely proposed due to its flexibility. It enables the physician to combine another treatment method such as neuroprotective or neuroregenerative or both in one intervention. CONCLUSION: Diamond concept perspective in the implementation of scaffolding could be advantageous to increase the outcome of SCI treatment.

Mesenchymal stem cell and endothelial progenitor cells coinjection improves LPS-induced lung injury via Tie2 activation and downregulation of the TLR4/MyD88 pathway

Sepsis is one of the most important complications of infection with a high mortality rate. Recently, cell therapy has been widely used to reduce the symptoms of sepsis. It has been previously reported that mesenchymal stem cell (MSC) and endothelial progenitor cells (EPC) therapy have beneficial effects in experimental models of sepsis. The effects of coculture of MSC and EPC have not yet been used to treat sepsis. Therefore, the aim of this study was to investigate the therapeutic potential of EPC + MSC coculture on the residual effects of sepsis in a lipopolysaccharide (LPS)-induced mice model. Coinjections of EPC + MSC significantly enhanced the survival rate of LPS-induced mice, decreased concentrations of pro-inflammatory cytokines, and increased the level of anti-inflammatory cytokine. The LPS-induced mice that were treated with EPC + MSC showed a notable reduction in pulmonary edema, hepatic enzymes, and C-reactive protein level compared with the control group. Our results showed that coinjection of EPC + MSC up and downregulates Tie2 and TLR4/MyD88 signaling pathways in LPS-induced mice, respectively. Also, in vitro study showed that viability, adhesion, and migration in coculture cells is significantly decreased after being induced with 10 μg/ml LPS. Our results showed that LPS impaired the functional activity of the cocultured EPC + MSC via upregulation of the TLR4/MyD88 signaling pathway, which may be associated with decreased pTie2/Tie2 expression. In conclusion, coinjection of EPC and MSC modulated the TLR4/MyD88 signaling pathway that leads to reduce the inflammatory response. This study may provide promising results for the introduction of cocultured cells to manage infectious diseases and balance the immune response through immune regulatory function.

Non-canonical Hedgehog signaling regulates spinal cord and muscle regeneration in Xenopus laevis larvae

Inducing regeneration in injured spinal cord represents one of modern medicine’s greatest challenges. Research from a variety of model organisms indicates that Hedgehog (Hh) signaling may be a useful target to drive regeneration. However, the mechanisms of Hh signaling-mediated tissue regeneration remain unclear. Here, we examined Hh signaling during post-amputation tail regeneration in Xenopus laevis larvae. We found that while Smoothened (Smo) activity is essential for proper spinal cord and skeletal muscle regeneration, transcriptional activity of the canonical Hh effector Gli is repressed immediately following amputation, and inhibition of Gli1/2 expression or transcriptional activity has minimal effects on regeneration. In contrast, we demonstrate that protein kinase A is necessary for regeneration of both muscle and spinal cord, in concert with and independent of Smo, respectively, and that its downstream effector CREB is activated in spinal cord following amputation in a Smo-dependent manner. Our findings indicate that non-canonical mechanisms of Hh signaling are necessary for spinal cord and muscle regeneration.

[Experimental study of endothelial progenitor cells derived small extracellular vesicles for spinal cord injury repair in mice]

Objective

To explore the potential therapeutic effects of endothelial progenitor cells derived small extracellular vesicles (EPCs-sEVs) on spinal cord injury in mice.

Methods

EPCs were separated from femur and tibia bone marrow of 20 C57BL/6 male mice, and identified by double fluorescence staining and flow cytometry. Then the EPCs were passaged and the cell supernatants from P2-P4 generations EPCs were collected; the EPCs-sEVs were extracted by ultracentrifugation and identified by transmission electron microscopy, nanoflow cytometry, and Western blot. Forty C57BL/6 female mice were randomly divided into 4 groups ( n=10). The mice were only removed T ₁₀ lamina in sham group, and prepared T ₁₀ spinal cord injury models in the model group and the low and high concentration intervention groups. After 30 minutes, 3 days, and 7 days of operation, the mice in low and high concentration intervention groups were injected with EPCs-sEVs at concentrations of 1×10 ⁹ and 1×10 ¹⁰cells/mL through the tail vein, respectively. The behavioral examinations [Basso Mouse Scale (BMS) score, inclined plate test, Von Frey test] , and the gross, HE staining, and immunohistochemical staining were performed to observe the structural changes of the spinal cord at 4 weeks after operation. Another 3 C57BL/6 female mice were taken to prepare T ₁₀ spinal cord injury models, and DiR-labeled EPCs- sEVs were injected through the tail vein. After 30 minutes, in vivo imaging was used to observe whether the EPCs-sEVs reached the spinal cord injury site.

Results

After identification, EPCs and EPCs-sEVs derived from mouse bone marrow were successfully obtained. In vivo imaging of the spinal cord showed that EPCs-sEVs were recruited to the spinal cord injury site within 30 minutes after injection. There was no significant difference in BMS scores and the maximum angle of the inclined plate test between two intervention groups and the model group within 2 weeks after operation ( P>0.05), while both were significantly better than the model group ( P<0.05) after 2 weeks. The Von Frey test showed that the mechanical pain threshold of the two intervention groups were significantly higher than that of model group and lower than that of sham group ( P<0.05); there was no significant difference between two intervention groups ( P>0.05). Compared with the model group, the injured segment of the two intervention groups had smaller spinal cord tissue defects, less mononuclear cells infiltration, more obvious tissue structure recovery, and more angiogenesis, and these differences were significant ( P<0.05); there was no significant difference between the two intervention groups.

Conclusion

EPCs-sEVs can promote the repair of spinal cord injury in mice and provide a new plan for the biological treatment of spinal cord injury.