Therapeutic Potential of Mesenchymal Stem Cells (MSCs) and MSC-Derived Extracellular Vesicles for the Treatment of Spinal Cord Injury

Therapeutic advances in neural regeneration for Huntington's disease

Huntington's disease is a neurodegenerative disease caused by the expansion mutation of a cytosine-adenine-guanine triplet in the exon 1 of the HTT gene which is responsible for the production of the huntingtin (Htt) protein. In physiological conditions, Htt is involved in many cellular processes such as cell signaling, transcriptional regulation, energy metabolism regulation, DNA maintenance, axonal trafficking, and antiapoptotic activity. When the genetic alteration is present, the production of a mutant version of Htt (mHtt) occurs, which is characterized by a plethora of pathogenic activities that, finally, lead to cell death. Among all the cells in which mHtt exerts its dangerous activity, the GABAergic Medium Spiny Neurons seem to be the most affected by the mHtt-induced excitotoxicity both in the cortex and in the striatum. However, as the neurodegeneration proceeds ahead the neuronal loss grows also in other brain areas such as the cerebellum, hypothalamus, thalamus, subthalamic nucleus, globus pallidus, and substantia nigra, determining the variety of symptoms that characterize Huntington's disease. From a clinical point of view, Huntington's disease is characterized by a wide spectrum of symptoms spanning from motor impairment to cognitive disorders and dementia. Huntington's disease shows a prevalence of around 3.92 cases every 100,000 worldwide and an incidence of 0.48 new cases every 100,000/year. To date, there is no available cure for Huntington's disease. Several treatments have been developed so far, aiming to reduce the severity of one or more symptoms to slow down the inexorable decline caused by the disease. In this context, the search for reliable strategies to target the different aspects of Huntington's disease become of the utmost interest. In recent years, a variety of studies demonstrated the detrimental role of neuronal loss in Huntington's disease condition highlighting how the replacement of lost cells would be a reasonable strategy to overcome the neurodegeneration. In this view, numerous have been the attempts in several preclinical models of Huntington's disease to evaluate the feasibility of invasive and non-invasive approaches. Thus, the aim of this review is to offer an overview of the most appealing approaches spanning from stem cell-based cell therapy to extracellular vesicles such as exosomes in light of promoting neurogenesis, discussing the results obtained so far, their limits and the future perspectives regarding the neural regeneration in the context of Huntington's disease.

Exosomes isolated from TNF-α-treated bone marrow mesenchymal stem cells ameliorate pelvic floor dysfunction in rats

Exosomes derived from bone marrow-derived mesenchymal stem cells (BMSCs) can alleviate the symptoms of pelvic floor dysfunction (PFD) in rats. However, the potential therapeutical effects of exosomes derived from BMSCs treated with tumour necrosis factor (TNF)-α on the symptoms of PFD in rats are unknown. Exosomes extracted from BMSCs treated with or without TNF-α were applied to treat PFD rats. Our findings revealed a significant elevation in interleukin (IL)-6 and TNF-α, and matrix metalloproteinase-2 (MMP2) levels in the vaginal wall tissues of patients with pelvic organ prolapse (POP) compared with the control group. Daily administration of exosomes derived from BMSCs, treated either with or without TNF-α (referred to as Exo and TNF-Exo), resulted in increased void volume and bladder void pressure, along with reduced peak bladder pressure and leak point pressure in PFD rats. Notably, TNF-Exo treatment demonstrated superior efficacy in restoring void volume, bladder void pressure and the mentioned parameters compared with Exo treatment. Importantly, TNF-Exo exhibited greater potency than Exo in restoring the levels of multiple proteins (Elastin, Collagen I, Collagen III, IL-6, TNF-α and MMP2) in the anterior vaginal walls of PFD rats. The application of exosomes derived from TNF-α-treated BMSCs holds promise as a novel therapeutic approach for treating PFD.

The Main Mechanisms of Mesenchymal Stem Cell-Based Treatments against COVID-19

BACKGROUND

Coronavirus disease 2019 (COVID-19) has a clinical manifestation of hypoxic respiratory failure and acute respiratory distress syndrome. However, COVID-19 still lacks of effective clinical treatments so far. As a promising potential treatment against COVID-19, stem cell therapy raised recently and had attracted much attention. Here we review the mechanisms of mesenchymal stem cell-based treatments against COVID-19, and provide potential cues for the effective control of COVID-19 in the future.

METHODS

Literature is obtained from databases PubMed and Web of Science. Key words were chosen for COVID- 19, acute respiratory syndrome coronavirus 2, mesenchymal stem cells, stem cell therapy, and therapeutic mechanism. Then we summarize and critically analyze the relevant articles retrieved.

RESULTS

Mesenchymal stem cell therapy is a potential effective treatment against COVID-19. Its therapeutic efficacy is mainly reflected in reducing severe pulmonary inflammation, reducing lung injury, improving pulmonary function, protecting and repairing lung tissue of the patients. Possible therapeutic mechanisms might include immunoregulation, anti-inflammatory effect, tissue regeneration, anti-apoptosis effect, antiviral, and antibacterial effect, MSC - EVs, and so on.

CONCLUSION

Mesenchymal stem cells can effectively treat COVID-19 through immunoregulation, anti-inflammatory, tissue regeneration, anti-apoptosis, anti-virus and antibacterial, MSC - EVs, and other ways. Systematically elucidating the mechanisms of mesenchymal stem cell-based treatments for COVID-19 will provide novel insights into the follow-up research and development of new therapeutic strategies in next step.

Biomaterials targeting the microenvironment for spinal cord injury repair: progression and perspectives

Spinal cord injury (SCI) disrupts nerve pathways and affects sensory, motor, and autonomic function. There is currently no effective treatment for SCI. SCI occurs within three temporal periods: acute, subacute, and chronic. In each period there are different alterations in the cells, inflammatory factors, and signaling pathways within the spinal cord. Many biomaterials have been investigated in the treatment of SCI, including hydrogels and fiber scaffolds, and some progress has been made in the treatment of SCI using multiple materials. However, there are limitations when using individual biomaterials in SCI treatment, and these limitations can be significantly improved by combining treatments with stem cells. In order to better understand SCI and to investigate new strategies for its treatment, several combination therapies that include materials combined with cells, drugs, cytokines, etc. are summarized in the current review.

Epigenetic mechanism of miR-26b-5p-enriched MSCs-EVs attenuates spinal cord injury

Mesenchymal stem cells (MSCs) and extracellular vesicles (EVs) are promising therapies for the treatment of spinal cord injury (SCI). This study sought to explore the epigenetic mechanism of miR-26b-5p-enriched MSCs-EVs in SCI. MSCs and MSCs-EVs were isolated and characterized. The SCI rat model was established, followed by Basso-Beattie-Bresnahan scoring and H&E staining. In vitro cell models were established in PC12 cells with lipopolysaccharide (LPS) treatment, followed by cell viability evaluation using CCK-8 assay. The levels of miR-26b-5p, lysine demethylase 6A (KDM6A), NADPH oxidase 4 (NOX4), reactive oxygen species (ROS), and inflammatory factors (TNF-α/IL-1β/IL-6) in tissues and cells were detected. The levels of cy3-lablled miR-26b-5p in tissues and cells were observed by confocal microscopy. The binding of miR-26b-5p to KDM6A 3'UTR and the enrichments of KDM6A and H3K27me3 at the NOX4 promoter were analyzed. MSCs-EVs attenuated motor dysfunction, inflammation, and oxidative stress in SCI rats. MSCs-EVs delivered miR-26b-5p into PC12 cells to reduce LPS-induced inflammation and ROS production and enhance cell viability. miR-26b-5p inhibited KDM6A, and KDM6A reduced H3K27me3 at the NOX4 promoter to promote NOX4. Overexpression of KDM6A or NOX4 reversed the alleviative role of MSCs-EVs in SCI or LPS-induced cell injury. Overall, MSCs-EVs delivered miR-26b-5p into cells to target the KDM6A/NOX4 axis and facilitate the recovery from SCI.

The acute spinal cord injury microenvironment and its impact on the homing of mesenchymal stem cells

Spinal cord injury (SCI) is a highly debilitating condition that inflicts devastating harm on the lives of affected individuals, underscoring the urgent need for effective treatments. By activating inflammatory cells and releasing inflammatory factors, the secondary injury response creates an inflammatory microenvironment that ultimately determines whether neurons will undergo necrosis or regeneration. In recent years, mesenchymal stem cells (MSCs) have garnered increasing attention for their therapeutic potential in SCI. MSCs not only possess multipotent differentiation capabilities but also have homing abilities, making them valuable as carriers and mediators of therapeutic agents. The inflammatory microenvironment induced by SCI recruits MSCs to the site of injury through the release of various cytokines, chemokines, adhesion molecules, and enzymes. However, this mechanism has not been previously reported. Thus, a comprehensive exploration of the molecular mechanisms and cellular behaviors underlying the interplay between the inflammatory microenvironment and MSC homing is crucial. Such insights have the potential to provide a better understanding of how to harness the therapeutic potential of MSCs in treating inflammatory diseases and facilitating injury repair. This review aims to delve into the formation of the inflammatory microenvironment and how it influences the homing of MSCs.

Therapeutic potential of mesenchymal stem cells for cerebral small vessel disease

Cerebral small vessel disease (CSVD), as the most common, chronic and progressive vascular disease on the brain, is a serious neurological disease, whose pathogenesis remains unclear. The disease is a leading cause of stroke and vascular cognitive impairment and dementia, and contributes to about 20% of strokes, including 25% of ischemic strokes and 45% of dementias. Undoubtedly, the high incidence and poor prognosis of CSVD have brought a heavy economic and medical burden to society. The present treatment of CSVD focuses on the management of vascular risk factors. Although vascular risk factors may be important causes or accelerators of CSVD and should always be treated in accordance with best clinical practice, controlling risk factors alone could not curb the progression of CSVD brain injury. Therefore, developing safer and more effective treatment strategies for CSVD is urgently needed. Recently, mesenchymal stem cells (MSCs) therapy has become an emerging therapeutic modality for the treatment of central nervous system disease, given their paracrine properties and immunoregulatory. Herein, we discussed the therapeutic potential of MSCs for CSVD, aiming to enable clinicians and researchers to understand of recent progress and future directions in the field.

Understanding exosomes: Part 2-Emerging leaders in regenerative medicine

Exosomes are the smallest subset of extracellular signaling vesicles secreted by most cells with the ability to communicate with other tissues and cell types over long distances. Their use in regenerative medicine has gained tremendous momentum recently due to their ability to be utilized as therapeutic options for a wide array of diseases/conditions. Over 5000 publications are currently being published yearly on this topic, and this number is only expected to dramatically increase as novel therapeutic strategies continue to be developed. Today exosomes have been applied in numerous contexts including neurodegenerative disorders (Alzheimer's disease, central nervous system, depression, multiple sclerosis, Parkinson's disease, post-traumatic stress disorders, traumatic brain injury, peripheral nerve injury), damaged organs (heart, kidney, liver, stroke, myocardial infarctions, myocardial infarctions, ovaries), degenerative processes (atherosclerosis, diabetes, hematology disorders, musculoskeletal degeneration, osteoradionecrosis, respiratory disease), infectious diseases (COVID-19, hepatitis), regenerative procedures (antiaging, bone regeneration, cartilage/joint regeneration, osteoarthritis, cutaneous wounds, dental regeneration, dermatology/skin regeneration, erectile dysfunction, hair regrowth, intervertebral disc repair, spinal cord injury, vascular regeneration), and cancer therapy (breast, colorectal, gastric cancer and osteosarcomas), immune function (allergy, autoimmune disorders, immune regulation, inflammatory diseases, lupus, rheumatoid arthritis). This scoping review is a first of its kind aimed at summarizing the extensive regenerative potential of exosomes over a broad range of diseases and disorders.

Schwann Cell-Derived Exosomal Vesicles: A Promising Therapy for the Injured Spinal Cord

Exosomes are nanoscale-sized membrane vesicles released by cells into their extracellular milieu. Within these nanovesicles reside a multitude of bioactive molecules, which orchestrate essential biological processes, including cell differentiation, proliferation, and survival, in the recipient cells. These bioactive properties of exosomes render them a promising choice for therapeutic use in the realm of tissue regeneration and repair. Exosomes possess notable positive attributes, including a high bioavailability, inherent safety, and stability, as well as the capacity to be functionalized so that drugs or biological agents can be encapsulated within them or to have their surface modified with ligands and receptors to imbue them with selective cell or tissue targeting. Remarkably, their small size and capacity for receptor-mediated transcytosis enable exosomes to cross the blood-brain barrier (BBB) and access the central nervous system (CNS). Unlike cell-based therapies, exosomes present fewer ethical constraints in their collection and direct use as a therapeutic approach in the human body. These advantageous qualities underscore the vast potential of exosomes as a treatment option for neurological injuries and diseases, setting them apart from other cell-based biological agents. Considering the therapeutic potential of exosomes, the current review seeks to specifically examine an area of investigation that encompasses the development of Schwann cell (SC)-derived exosomal vesicles (SCEVs) as an approach to spinal cord injury (SCI) protection and repair. SCs, the myelinating glia of the peripheral nervous system, have a long history of demonstrated benefit in repair of the injured spinal cord and peripheral nerves when transplanted, including their recent advancement to clinical investigations for feasibility and safety in humans. This review delves into the potential of utilizing SCEVs as a therapy for SCI, explores promising engineering strategies to customize SCEVs for specific actions, and examines how SCEVs may offer unique clinical advantages over SC transplantation for repair of the injured spinal cord.

Macrophage polarization in spinal cord injury repair and the possible role of microRNAs: A review

The prevention, treatment, and rehabilitation of spinal cord injury (SCI) have always posed significant medical challenges. After mechanical injury, disturbances in microcirculation, edema formation, and the generation of free radicals lead to additional damage, impeding effective repair processes and potentially exacerbating further dysfunction. In this context, inflammatory responses, especially the activation of macrophages, play a pivotal role. Different phenotypes of macrophages have distinct effects on inflammation. Activation of classical macrophage cells (M1) promotes inflammation, while activation of alternative macrophage cells (M2) inhibits inflammation. The polarization of macrophages is crucial for disease healing. A non-coding RNA, known as microRNA (miRNA), governs the polarization of macrophages, thereby reducing inflammation following SCI and facilitating functional recovery. This study elucidates the inflammatory response to SCI, focusing on the infiltration of immune cells, specifically macrophages. It examines their phenotype and provides an explanation of their polarization mechanisms. Finally, this paper introduces several well-known miRNAs that contribute to macrophage polarization following SCI, including miR-155, miR-130a, and miR-27 for M1 polarization, as well as miR-22, miR-146a, miR-21, miR-124, miR-223, miR-93, miR-132, and miR-34a for M2 polarization. The emphasis is placed on their potential therapeutic role in SCI by modulating macrophage polarization, as well as the present developments and obstacles of miRNA clinical therapy.

Tauroursodeoxycholic Acid Inhibited Apoptosis and Oxidative Stress in H2O2-Induced BMSC Death via Modulating the Nrf-2 Signaling Pathway: the Therapeutic Implications in a Rat Model of Spinal Cord Injury

Spinal cord injury (SCI) is a prevalent and significant injury to the central nervous system, resulting in severe consequences. This injury is characterized by motor, sensory, and excretory dysfunctions below the affected spinal segment. Transplantation of bone marrow mesenchymal stem cells (BMSCs) has emerged as a potential treatment for SCI. However, the low survival as well as the differentiation rates of BMSCs within the spinal cord microenvironment significantly limit their therapeutic efficiency. Tauroursodeoxycholic acid (TUDCA), an active ingredient found in bear bile, has demonstrated its neuroprotective, antioxidant, and antiapoptotic effects on SCI. Thus, the present study was aimed to study the possible benefits of combining TUDCA with BMSC transplantation using an animal model of SCI. The results showed that TUDCA significantly enhanced BMSC viability and reduced apoptosis (assessed by Annexin V-FITC, TUNEL, Bax, Bcl-2, and Caspase-3) as well as oxidative stress (assessed by ROS, GSH, SOD, and MDA) both in vitro and in vivo. Additionally, TUDCA accelerated tissue regeneration (assessed by HE, Nissl, MAP2, MBP, TUJ1, and GFAP) and improved functional recovery (assessed by BBB score) following BMSC transplantation in SCI. These effects were mediated via the Nrf-2 signaling pathway, as evidenced by the upregulation of Nrf-2, NQO-1, and HO-1 expression levels. Overall, these results indicate that TUDCA could serve as a valuable adjunct to BMSC transplantation therapy for SCI, potentially enhancing its therapeutic efficacy.

Exosome-loaded degradable polymeric microcapsules for the treatment of vitreoretinal diseases

The therapeutic benefits of many cell types involve paracrine mechanisms. Inspired by the paracrine functions of exosomes and the sustained degradation properties of microcapsules, here we report the therapeutic benefits of exosome-loaded degradable poly(lactic-co-glycolic acid) microcapsules with micrometric pores for the treatment of vitreoretinal diseases. On intravitreal injection in a mouse model of retinal ischaemia-reperfusion injury, microcapsules encapsulating mouse mesenchymal-stem-cell-derived exosomes settled in the inferior vitreous cavity, released exosomes for over one month as they underwent degradation and led to the restoration of retinal thickness to nearly that of the healthy retina. In mice and non-human primates with primed mycobacterial uveitis, intravitreally injected microcapsules loaded with exosomes from monkey regulatory T cells resulted in a substantial reduction in the levels of inflammatory cells. The exosome-encapsulating microcapsules, which can be lyophilised, may offer alternative treatment options for vitreoretinal diseases.

microRNAs delivered by small extracellular vesicles in MSCs as an emerging tool for bone regeneration

Bone regeneration is a dynamic process that involves angiogenesis and the balance of osteogenesis and osteoclastogenesis. In bone tissue engineering, the transplantation of mesenchymal stem cells (MSCs) is a promising approach to restore bone homeostasis. MSCs, particularly their small extracellular vesicles (sEVs), exert therapeutic effects due to their paracrine capability. Increasing evidence indicates that microRNAs (miRNAs) delivered by sEVs from MSCs (MSCs-sEVs) can alter gene expression in recipient cells and enhance bone regeneration. As an ideal delivery vehicle of miRNAs, MSCs-sEVs combine the high bioavailability and stability of sEVs with osteogenic ability of miRNAs, which can effectively overcome the challenge of low delivery efficiency in miRNA therapy. In this review, we focus on the recent advancements in the use of miRNAs delivered by MSCs-sEVs for bone regeneration and disorders. Additionally, we summarize the changes in miRNA expression in osteogenic-related MSCs-sEVs under different microenvironments.

Berberine-loaded MSC-derived sEVs encapsulated in injectable GelMA hydrogel for spinal cord injury repair

After spinal cord injury (SCI), local inflammatory response and fibrous scar formation severely hinder nerve regeneration. Berberine (Ber) has a powerful regulatory effect on the local microenvironment, but its limited solubility and permeability through the blood-brain barrier severely limit its systemic efficacy. Human umbilical cord mesenchymal stem cells (hUC-MSCs)-derived small extracellular vesicles (sEVs) are natural nanocarriers with high cargo loading capacity, and can cross the blood-brain barrier. Most importantly, sEVs can improve drug solubility and drug utilization. Therefore, they can overcome many defects of Ber application. This experiment aimed to design a Ber-carrying hUC-MSCs-derived sEVs and GelMA hydrogel. Ber was loaded into sEVs (sEVs-Ber) by ultrasonic co-incubation with a drug loading capacity (LC) of 15.07%. The unhindered release of up to 80% of sEVs-Ber from GelMA hydrogel was accomplished for up to 14 days. And they could be directly absorbed by local cells of injury, allowing for direct local delivery of the drug and enhancing its efficacy. The experimental results confirmed injecting GelMA-sEVs-Ber into spinal cord defects could exert anti-inflammatory effects by regulating the expression of inflammatory factors. It also demonstrated the anti-fibrotic effect of Ber in SCI for the first time. The modulatory effects of sEVs and Ber on the local microenvironment significantly promoted nerve regeneration and recovery of motor function in post-SCI rats. These results demonstrated that the GelMA-sEVs-Ber dual carrier system is a promising therapeutic strategy for SCI repair.

Mesenchymal stem cell-derived extracellular vesicles: emerging concepts in the treatment of spinal cord injury

Spinal cord injury (SCI) is a prevalent central nervous system disease with a high disability rate, leading to the loss of motor and sensory nerve function. Due to the complex pathophysiology of SCI, more effective clinical treatment strategies are needed. Research has indicated the considerable potential of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSC-EVs) as a cell-free therapy in SCI repair and regeneration due to their ability to regulate immune cell activity and stimulate damaged neuron regeneration. Moreover, applying MSCs and engineered EVs can fully exploit the potential of MSC-EVs in spinal cord repair. Here, we outline the pathological process of SCI and its current clinical treatment status, summarize the latest MSC-EVs research and its pretreatment and engineering strategies in SCI treatment, and explore MSC-EVs application prospects.

Exosomes combined with biomaterials in the treatment of spinal cord injury

Spinal cord injury (SCI) is a serious and disabling disease with a high mortality rate. It often leads to complete or partial sensory and motor dysfunction and is accompanied by a series of secondary outcomes, such as pressure sores, pulmonary infections, deep vein thrombosis in the lower extremities, urinary tract infections, and autonomic dysfunction. Currently, the main treatments for SCI include surgical decompression, drug therapy, and postoperative rehabilitation. Studies have shown that cell therapy plays a beneficial role in the treatment of SCI. Nonetheless, there is controversy regarding the therapeutic effect of cell transplantation in SCI models. Meanwhile exosomes, as a new therapeutic medium for regenerative medicine, possess the advantages of small size, low immunogenicity, and the ability to cross the blood-spinal cord barrier. Certain studies have shown that stem cell-derived exosomes have anti-inflammatory effects and can play an irreplaceable role in the treatment of SCI. In this case, it is difficult for a single treatment method to play an effective role in the repair of neural tissue after SCI. The combination of biomaterial scaffolds and exosomes can better transfer and fix exosomes to the injury site and improve their survival rate. This paper first reviews the current research status of stem cell-derived exosomes and biomaterial scaffolds in the treatment of SCI respectively, and then describes the application of exosomes combined with biomaterial scaffolds in the treatment of SCI, as well as the challenges and prospects.

Regenerative Effects of Exosomes-Derived MSCs: An Overview on Spinal Cord Injury Experimental Studies

Spinal cord injury (SCI) is a devastating condition usually induced by the initial mechanical insult that can lead to permanent motor and sensory deficits. At present, researchers are investigating potential therapeutic strategies to ameliorate the neuro-inflammatory cascade that occurs post-injury. Although the use of mesenchymal stromal/stem (MSCs) as a potential therapy in application to regenerative medicine promoted anti-inflammatory and neuroprotective effects, several disadvantages limit their use. Therefore, recent studies have reported the effects of exosomes-derived MSCs (MSC-EXOs) as an innovative therapeutic option for SCI patients. It is noteworthy that MSC-EXOs can maintain the integrity of the blood-spinal cord barrier (BSCB), promoting angiogenic, proliferative, and anti-oxidant effects, as well as immunomodulatory, anti-inflammatory, and antiapoptotic properties. Therefore, in this study, we summarized the preclinical studies reported in the literature that have shown the effects of MSC-EXOs as a new molecular target to counteract the devastating effects of SCI.

Crosstalk between exosomes and autophagy in spinal cord injury: fresh positive target for therapeutic application

Spinal cord injury (SCI) is a very serious clinical traumatic illness with a very high disability rate. It not only causes serious functional disorders below the injured segment, but also causes unimaginable economic burden to social development. Exosomes are nano-sized cellular communication carriers that exist stably in almost all organisms and cell types. Because of their capacity to transport proteins, lipids, and nucleic acids, they affect various physiological and pathological functions of recipient cells and parental cells. Autophagy is a process that relies on the lysosomal pathway to degrade cytoplasmic proteins and organelles and involves a variety of pathophysiological processes. Exosomes and autophagy play critical roles in cellular homeostasis following spinal cord injury. Presently, the coordination mechanism of exosomes and autophagy has attracted much attention in the early efficacy of spinal cord injury. In this review, we discussed the interaction of autophagy and exosomes from the perspective of molecular mechanisms, which might provide novel insights for the early therapeutic application of spinal cord injury.

Mesenchymal stem cells in the treatment of spinal cord injury: Mechanisms, current advances and future challenges

Spinal cord injury (SCI) has considerable impact on patient physical, mental, and financial health. Secondary SCI is associated with inflammation, vascular destruction, and subsequent permanent damage to the nervous system. Mesenchymal stem cells (MSCs) have anti-inflammatory properties, promoting vascular regeneration and the release neuro-nutrients, and are a promising strategy for the treatment of SCI. Preclinical studies have shown that MSCs promote sensory and motor function recovery in rats. In clinical trials, MSCs have been reported to improve the American Spinal Injury Association (ASIA) sensory and motor scores. However, the effectiveness of MSCs in treating patients with SCI remains controversial. MSCs promote tumorigenesis and ensuring the survival of MSCs in the hostile environment of SCI is challenging. In this article we examine the evidence on the pathophysiological changes occurring after SCI. We then review the underlying mechanisms of MSCs in the treatment of SCI and summarize the potential application of MSCs in clinical practice. Finally, we highlight the challenges surrounding the use of MSCs in the treatment of SCI and discuss future applications.

Multiple strategies enhance the efficacy of MSCs transplantation for spinal cord injury

Spinal cord injury (SCI) is a serious complication of the central nervous system (CNS) after spine injury, often resulting in severe sensory, motor, and autonomic dysfunction below the level of injury. To date, there is no effective treatment strategy for SCI. Recently, stem cell therapy has brought hope to patients with neurological diseases. Mesenchymal stem cells (MSCs) are considered to be the most promising source of cellular therapy after SCI due to their immunomodulatory, neuroprotective and angiogenic potential. Considering the limited therapeutic effect of MSCs due to the complex pathophysiological environment following SCI, this paper not only reviews the specific mechanism of MSCs to facilitate SCI repair, but also further discusses the research status of these pluripotent stem cells combined with other therapeutic approaches to promote anatomical and functional recovery post-SCI.

Therapeutic potential of small extracellular vesicles derived from mesenchymal stem cells for spinal cord and nerve injury

Neural diseases such as compressive, congenital, and traumatic injuries have diverse consequences, from benign mild sequelae to severe life-threatening conditions with associated losses of motor, sensory, and autonomic functions. Several approaches have been adopted to control neuroinflammatory cascades. Traditionally, mesenchymal stem cells (MSCs) have been regarded as therapeutic agents, as they possess growth factors and cytokines with potential anti-inflammatory and regenerative effects. However, several animal model studies have reported conflicting outcomes, and therefore, the role of MSCs as a regenerative source for the treatment of neural pathologies remains debatable. In addition, issues such as heterogeneity and ethical issues limited their use as therapeutic agents. To overcome the obstacles associated with the use of traditional agents, we explored the therapeutic potentials of extracellular vesicles (EVs), which contain nucleic acids, functional proteins, and bioactive lipids, and play crucial roles in immune response regulation, inflammation reduction, and cell-to-cell communication. EVs may surpass MSCs in size issue, immunogenicity, and response to the host environment. However, a comprehensive review is required on the therapeutic potential of EVs for the treatment of neural pathologies. In this review, we discuss the action mechanism of EVs, their potential for treating neural pathologies, and future perspectives regarding their clinical applications.

Molecular Mechanisms and Clinical Application of Multipotent Stem Cells for Spinal Cord Injury

Spinal Cord Injury (SCI) is a common neurological disorder with devastating psychical and psychosocial sequelae. The majority of patients after SCI suffer from permanent disability caused by motor dysfunction, impaired sensation, neuropathic pain, spasticity as well as urinary complications, and a small number of patients experience a complete recovery. Current standard treatment modalities of the SCI aim to prevent secondary injury and provide limited recovery of lost neurological functions. Stem Cell Therapy (SCT) represents an emerging treatment approach using the differentiation, paracrine, and self-renewal capabilities of stem cells to regenerate the injured spinal cord. To date, multipotent stem cells including mesenchymal stem cells (MSCs), neural stem cells (NSCs), and hematopoietic stem cells (HSCs) represent the most investigated types of stem cells for the treatment of SCI in preclinical and clinical studies. The microenvironment of SCI has a significant impact on the survival, proliferation, and differentiation of transplanted stem cells. Therefore, a deep understanding of the pathophysiology of SCI and molecular mechanisms through which stem cells act may help improve the treatment efficacy of SCT and find new therapeutic approaches such as stem-cell-derived exosomes, gene-modified stem cells, scaffolds, and nanomaterials. In this literature review, the pathogenesis of SCI and molecular mechanisms of action of multipotent stem cells including MSCs, NSCs, and HSCs are comprehensively described. Moreover, the clinical efficacy of multipotent stem cells in SCI treatment, an optimal protocol of stem cell administration, and recent therapeutic approaches based on or combined with SCT are also discussed.

A Comparative Study of Mesenchymal Stem Cell-Derived Extracellular Vesicles' Local and Systemic Dose-Dependent Administration in Rat Spinal Cord Injury

Spinal cord injury (SCI) is a serious neurological condition that causes severe disability. One of the approaches to overcoming the complications of SCI is stem cell-derived extracellular vesicle (EV) therapy. In this research, we performed a comparative evaluation of rat spinal cord post-traumatic regeneration efficacy using different methods of mesenchymal stem cell-derived EV transplantation (local vs. systemic) followed by evaluation of their minimal therapeutic dose. The results suggested that MSC-EV therapy could improve locomotor activity over 60 days after the SCI, showing a dose-dependent effect on the recovery of spinal cord motor pathways. We also established the possibility of maintaining a population of mature oligodendrocytes by MSC-EVs. It was observed that in the spinal cord injury area, intravenous transplantation of MSC-EVs showed more pronounced therapeutic effects compared to the treatment of fibrin matrix-encapsulated MSC-EVs.

Mesenchymal stem cell-based therapy as a new therapeutic approach for acute inflammation

Acute inflammatory diseases such as acute colitis, kidney injury, liver failure, lung injury, myocardial infarction, pancreatitis, septic shock, and spinal cord injury are significant causes of death worldwide. Despite advances in the understanding of its pathophysiology, there are many restrictions in the treatment of these diseases, and new therapeutic approaches are required. Mesenchymal stem cell-based therapy due to immunomodulatory and regenerative properties is a promising candidate for acute inflammatory disease management. Based on preclinical results, mesenchymal stem cells and their-derived secretome improved immunological and clinical parameters. Furthermore, many clinical trials of acute kidney, liver, lung, myocardial, and spinal cord injury have yielded promising results. In this review, we try to provide a comprehensive view of mesenchymal stem cell-based therapy in acute inflammatory diseases as a new treatment approach.

KCC2 overexpressed exosomes meditated spinal cord injury recovery in mice

Exosomes show great potential in treating diseases of the central nervous system including spinal cord injury (SCI), still better engineered exosomes have more advantages. In this study, we purified exosomes from K⁺-Cl^-co-transporter (KCC2) overexpressed bone marrow mesenchymal stem cells (Exo_KCC2), to investigate the effect of Exo_KCC2on neural differentiationin vitroand the repairing function of Exo_KCC2in SCI micein vivo. Compared to bone marrow mesenchymal stem cells (BMSC)-derived exosomes (Exo), Exo_KCC2could better promote neural stem cell differentiated into neurons, ameliorate the function recovery of SCI mice, and accelerate the neural regeneration at the lesion site. Altogether, engineered Exo_KCC2may prove to be an advantageous strategy for SCI treatment.

Implantation of adipose-derived mesenchymal stem cell sheets promotes axonal regeneration and restores bladder function after spinal cord injury

BACKGROUND

Cell-based therapy using adipose-derived mesenchymal stem cells (ADSCs) is a promising treatment strategy for neurogenic bladder (NB) associated with spinal cord injury (SCI). However, therapeutic efficacy is low because of inefficient cell delivery. Cell sheets improve the efficacy of cell transplantation. Therefore, this study was conducted to investigate the therapeutic efficacy of transplanting ADSC sheets into an SCI rat model and focused on the function and pathological changes of the bladder.

METHODS

ADSC sheets were prepared from adipose tissue of Sprague-Dawley (SD) rats using temperature-responsive cell culture dishes. Adult female SD rats were subjected to SCI by transection at the T10 level and administered ADSC sheets or gelatin sponge (the control group). Four and 8 weeks later, in vivo cystometrograms were obtained for voiding function assessment. Rats were sacrificed and the expression of various markers was analyzed in spinal and bladder tissues.

RESULTS

The number of β-tubulin III-positive axons in the ADSC sheet transplantation group was higher than that in the control group. Conversely, expression of glial fibrillary acidic protein in the ADSC sheet transplantation group was lower than that in the control group. Cystometry showed impairment of the voiding function after SCI, which was improved after ADSC sheet transplantation with increased high-frequency oscillation activity. Furthermore, ADSC sheet transplantation prevented disruption of the bladder urothelium in SCI rats, thereby maintaining the intact barrier. Compared with fibrosis of the bladder wall in the control group, the ADSC sheet transplantation group had normal morphology of the bladder wall and reduced tissue fibrosis as shown by downregulation of type 1 collagen. ADSC sheet transplantation also resulted in strong upregulation of contractile smooth muscle cell (SMC) markers (α-smooth muscle actin and smoothelin) and downregulation of synthetic SMC markers (MYH10 and RBP1).

CONCLUSION

ADSC sheet transplantation significantly improved voiding function recovery in rats after SCI. ADSC sheet transplantation is a promising cell delivery and treatment option for NB related to SCI.

Bone marrow mesenchymal stem cells and exercise restore motor function following spinal cord injury by activating PI3K/AKT/mTOR pathway

Although many therapeutic interventions have shown promise in treating spinal cord injury, focusing on a single aspect of repair cannot achieve successful and functional regeneration in patients following spinal cord injury . In this study, we applied a combinatorial approach for treating spinal cord injury involving neuroprotection and rehabilitation, exploiting cell transplantation and functional sensorimotor training to promote nerve regeneration and functional recovery. Here, we used a mouse model of thoracic contusive spinal cord injury to investigate whether the combination of bone marrow mesenchymal stem cell transplantation and exercise training has a synergistic effect on functional restoration. Locomotor function was evaluated by the Basso Mouse Scale, horizontal ladder test, and footprint analysis. Magnetic resonance imaging, histological examination, transmission electron microscopy observation, immunofluorescence staining, and western blotting were performed 8 weeks after spinal cord injury to further explore the potential mechanism behind the synergistic repair effect. In vivo, the combination of bone marrow mesenchymal stem cell transplantation and exercise showed a better therapeutic effect on motor function than the single treatments. Further investigations revealed that the combination of bone marrow mesenchymal stem cell transplantation and exercise markedly reduced fibrotic scar tissue, protected neurons, and promoted axon and myelin protection. Additionally, the synergistic effects of bone marrow mesenchymal stem cell transplantation and exercise on spinal cord injury recovery occurred via the PI3K/AKT/mTOR pathway. In vitro, experimental evidence from the PC12 cell line and primary cortical neuron culture also demonstrated that blocking of the PI3K/AKT/mTOR pathway would aggravate neuronal damage. Thus, bone marrow mesenchymal stem cell transplantation combined with exercise training can effectively restore motor function after spinal cord injury by activating the PI3K/AKT/mTOR pathway.

Extracellular Vesicles: The Next Generation Theranostic Nanomedicine for Inflammatory Bowel Disease

The recent rapid development in the field of extracellular vesicles (EVs) based nanotechnology has provided unprecedented opportunities for nanomedicine platforms. As natural nanocarriers, EVs such as exosomes, exosome-like nanoparticles and outer membrane vesicles (OMVs), have unique structure/composition/morphology characteristics, and show excellent physical and chemical/biochemical properties, making them a new generation of theranostic nanomedicine. Here, we reviewed the characteristics of EVs from the perspective of their formation and biological function in inflammatory bowel disease (IBD). Moreover, EVs can crucially participate in the interaction and communication of intestinal epithelial cells (IECs)-immune cells-gut microbiota to regulate immune response, intestinal inflammation and intestinal homeostasis. Interestingly, based on current representative examples in the field of exosomes and exosome-like nanoparticles for IBD treatment, it is shown that plant, milk, and cells-derived exosomes and exosome-like nanoparticles can exert a therapeutic effect through their components, such as proteins, nucleic acid, and lipids. Moreover, several drug loading methods and target modification of exosomes are used to improve their therapeutic capability. We also discussed the application of exosomes and exosome-like nanoparticles in the treatment of IBD. In this review, we aim to better and more clearly clarify the underlying mechanisms of the EVs in the pathogenesis of IBD, and provide directions of exosomes and exosome-like nanoparticles mediated for IBD treatment.

Significant Therapeutic Effects of Adult Human Neural Stem Cells for Spinal Cord Injury Are Mediated by Monocyte Chemoattractant Protein-1 (MCP-1)

The limited capability of regeneration in the human central nervous system leads to severe and permanent disabilities following spinal cord injury (SCI) while patients suffer from no viable treatment option. Adult human neural stem cells (ahNSCs) are unique cells derived from the adult human brain, which have the essential characteristics of NSCs. The objective of this study was to characterize the therapeutic effects of ahNSCs isolated from the temporal lobes of focal cortical dysplasia type IIIa for SCI and to elucidate their treatment mechanisms. Results showed that the recovery of motor functions was significantly improved in groups transplanted with ahNSCs, where, in damaged regions of spinal cords, the numbers of both spread and regenerated nerve fibers were observed to be higher than the vehicle group. In addition, the distance between neuronal nuclei in damaged spinal cord tissue was significantly closer in treatment groups than the vehicle group. Based on an immunohistochemistry analysis, those neuroprotective effects of ahNSCs in SCI were found to be mediated by inhibiting apoptosis of spinal cord neurons. Moreover, the analysis of the conditioned medium (CM) of ahNSCs revealed that such neuroprotective effects were mediated by paracrine effects with various types of cytokines released from ahNSCs, where monocyte chemoattractant protein-1 (MCP-1, also known as CCL2) was identified as a key paracrine mediator. These results of ahNSCs could be utilized further in the preclinical and clinical development of effective and safe cell therapeutics for SCI, with no available therapeutic options at present.

Effects of astrocytes and microglia on neuroinflammation after spinal cord injury and related immunomodulatory strategies

Spinal cord injury (SCI) is a catastrophic event which is still without adequate therapies. Neuroinflammation is the main pathogenesis of secondary damage post-SCI, leading to tissue loss and neurological dysfunction. Previous studies have shown that microglia and astrocytes are the major immune cells in the central nervous system (CNS) and play a crucial role in modulating neuroinflammatory responses. In this study, we mainly review the effects of neuroinflammation in SCI, focusing on the contributions of microglia and astrocytes and their cross-talk. Furthermore, we will also discuss therapeutic strategies on how to regulate their immunophenotype to suppress robust inflammation and facilitate injury prognosis.