The Role of Exosomes and Exosomal Noncoding RNAs From Different Cell Sources in Spinal Cord Injury

Multiple strategies enhance the efficacy of MSC-Exos transplantation for spinal cord injury

Spinal cord injury (SCI) is a relatively common and lethal dangerous disease of the central nervous system, for which there is a lack of effective clinical treatments. It has been found that mesenchymal stem cell-derived exosomes (MSC-Exos) play a key role in alleviating SCI through mechanisms such as regulating the microenvironment, promoting angiogenesis, and facilitating axonal regeneration. However, the drawbacks of natural exosomes, such as low yield, weak activity, and low targeting ability, limit their clinical applications. In recent years, MSCs-Exos have gradually become a research hotspot for treating SCI through miRNA modulation, combined hydrogel, and preculture. In addition, exosomes as good biocompatible drugs, nucleic acid, and other delivery carriers have shown a broad application prospect in treating SCI. This article summarizes the pathogenesis of SCI and the research progress of MSC-Exos in the treatment of SCI in recent years, and provides a systematic review of the mechanisms of MSC exosomes and their combination with different modalities in the treatment of SCI.

The role of exosomes derived from stem cells in nerve regeneration: A contribution to neurological repair

Stem cell-derived exosomes have gained attention in regenerative medicine for their role in encouraging nerve regeneration and potential use in treating neurological diseases. These nanosized extracellular vesicles act as carriers of bioactive molecules, facilitating intercellular communication and enhancing the regenerative process in neural tissues. This comprehensive study explores the methods by which exosomes produced from various stem cells contribute to nerve healing, with a particular emphasis on their role in angiogenesis, inflammation, and cellular signaling pathways. By examining cutting-edge developments and exploring the potential of exosomes in delivering disease-specific miRNAs and proteins, we highlight their versatility in tailoring personalized therapeutic strategies. The findings presented here highlight the potential of stem cell-produced exosomes for use in neurological diseases therapy, establishing the door for future research into exosome-based neurotherapies.

Repair of spinal cord injury by bone marrow mesenchymal stem cell-derived exosomes: a systematic review and meta-analysis based on rat models

Objective

This study aims to systematically evaluate the efficacy of bone marrow mesenchymal stem cell-derived exosomes (BMSCs-Exo) in improving spinal cord injury (SCI) to mitigate the risk of translational discrepancies from animal experiments to clinical applications.

Methods

We conducted a comprehensive literature search up to March 2024 using PubMed, Embase, Web of Science, and Scopus databases. Two researchers independently screened the literature, extracted data, and assessed the quality of the studies. Data analysis was performed using STATA16 software.

Results

A total of 30 studies were included. The results indicated that BMSCs-Exo significantly improved the BBB score in SCI rats (WMD = 3.47, 95% CI [3.31, 3.63]), inhibited the expression of the pro-inflammatory cytokine TNF-α (SMD = -3.12, 95% CI [-3.57, -2.67]), and promoted the expression of anti-inflammatory cytokines IL-10 (SMD = 2.76, 95% CI [1.88, 3.63]) and TGF-β (SMD = 3.89, 95% CI [3.02, 4.76]). Additionally, BMSCs-Exo significantly reduced apoptosis levels (SMD = -4.52, 95% CI [-5.14, -3.89]), promoted the expression of axonal regeneration markers NeuN cells/field (SMD = 3.54, 95% CI [2.65, 4.42]), NF200 (SMD = 4.88, 95% CI [3.70, 6.05]), and the number of Nissl bodies (SMD = 1.89, 95% CI [1.13, 2.65]), and decreased the expression of astrogliosis marker GFAP (SMD = -5.15, 95% CI [-6.47, -3.82]). The heterogeneity among studies was primarily due to variations in BMSCs-Exo transplantation doses, with efficacy increasing with higher doses.

Conclusion

BMSCs-Exo significantly improved motor function in SCI rats by modulating inflammatory responses, reducing apoptosis, inhibiting astrogliosis, and promoting axonal regeneration. However, the presence of selection, performance, and detection biases in current animal experiments may undermine the quality of evidence in this study.

Exosomes derived from umbilical cord-mesenchymal stem cells inhibit the NF-κB/MAPK signaling pathway and reduce the inflammatory response to promote recovery from spinal cord injury

Spinal cord injury (SCI) is a serious traumatic disease of the central nervous system and leads to incomplete or complete loss of the body's autonomous motor and sensory functions, seriously endangering human health. Recently, exosomes have been proposed as important substances in cell-to-cell interactions. Mesenchymal stem cell (MSC)-derived exosomes exert good therapeutic effects and play a crucial role in neurological damage repair. However, the detailed mechanisms underlying their effects remain unknown. Herein, we found that compared to SCI rats, those subjected to umbilical cord MSC (UC-MSC)-derived exosomes injection showed an improved motor ability. Nevertheless, the transcriptome of BV2 microglia in different treatment groups indicated that the action pathway of exosomes might be the NF-κB/MAPK pathway. Additionally, exosomes from UC-MSCs could inhibit P38, JNK, ERK, and P65 phosphorylation in BV2 microglia and SCI rat tissues. Moreover, exosomes could inhibit apoptosis and inflammatory reaction and reactive oxygen species (ROS) production of BV2 microglia in vitro and in vivo. In conclusion, UC-MSCs-derived exosomes might protect SCI in rats by inhibiting inflammatory response via the NF-κB/MAPK signaling pathway, representing novel treatment targets or approaches for SCI.

Remyelinating effect driven by transferrin-loaded extracellular vesicles

Extracellular vesicles (EVs) are involved in diverse cellular functions, playing a significant role in cell-to-cell communication in both physiological conditions and pathological scenarios. Therefore, EVs represent a promising therapeutic strategy. Oligodendrocytes (OLs) are myelinating glial cells developed from oligodendrocyte progenitor cells (OPCs) and damaged in chronic demyelinating diseases such as multiple sclerosis (MS). Glycoprotein transferrin (Tf) plays a critical role in iron homeostasis and has pro-differentiating effects on OLs in vivo and in vitro. In the current work, we evaluated the use of EVs as transporters of Tf to the central nervous system (CNS) through the intranasal (IN) route. For the in vitro mechanistic studies, we used rat plasma EVs. Our results show that EVTf enter OPCs through clathrin-caveolae and cholesterol-rich lipid raft endocytic pathways, releasing the cargo and exerting a pro-maturation effect on OPCs. These effects were also observed in vivo using the animal model of demyelination induced by cuprizone (CPZ). In this model, IN administered Tf-loaded EVs isolated from mouse plasma reached the brain parenchyma, internalizing into OPCs, promoting their differentiation, and accelerating remyelination. Furthermore, in vivo experiments demonstrated that EVs protected the Tf cargo and significantly reduced the amount of Tf required to induce remyelination as compared to soluble Tf. Collectively, these findings unveil EVs as functional nanocarriers of Tf to induce remyelination.

Clinical applications of stem cell-derived exosomes

Although stem cell-based therapy has demonstrated considerable potential to manage certain diseases more successfully than conventional surgery, it nevertheless comes with inescapable drawbacks that might limit its clinical translation. Compared to stem cells, stem cell-derived exosomes possess numerous advantages, such as non-immunogenicity, non-infusion toxicity, easy access, effortless preservation, and freedom from tumorigenic potential and ethical issues. Exosomes can inherit similar therapeutic effects from their parental cells such as embryonic stem cells and adult stem cells through vertical delivery of their pluripotency or multipotency. After a thorough search and meticulous dissection of relevant literature from the last five years, we present this comprehensive, up-to-date, specialty-specific and disease-oriented review to highlight the surgical application and potential of stem cell-derived exosomes. Exosomes derived from stem cells (e.g., embryonic, induced pluripotent, hematopoietic, mesenchymal, neural, and endothelial stem cells) are capable of treating numerous diseases encountered in orthopedic surgery, neurosurgery, plastic surgery, general surgery, cardiothoracic surgery, urology, head and neck surgery, ophthalmology, and obstetrics and gynecology. The diverse therapeutic effects of stem cells-derived exosomes are a hierarchical translation through tissue-specific responses, and cell-specific molecular signaling pathways. In this review, we highlight stem cell-derived exosomes as a viable and potent alternative to stem cell-based therapy in managing various surgical conditions. We recommend that future research combines wisdoms from surgeons, nanomedicine practitioners, and stem cell researchers in this relevant and intriguing research area.

Mesenchymal stem cell-derived extracellular vesicles therapy in traumatic central nervous system diseases: a systematic review and meta-analysis

Although there are challenges in treating traumatic central nervous system diseases, mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have recently proven to be a promising non-cellular therapy. We comprehensively evaluated the efficacy of mesenchymal stem cell-derived extracellular vesicles in traumatic central nervous system diseases in this meta-analysis based on preclinical studies. Our meta-analysis was registered at PROSPERO (CRD42022327904, May 24, 2022). To fully retrieve the most relevant articles, the following databases were thoroughly searched: PubMed, Web of Science, The Cochrane Library, and Ovid-Embase (up to April 1, 2022). The included studies were preclinical studies of mesenchymal stem cell-derived extracellular vesicles for traumatic central nervous system diseases. The Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE)'s risk of bias tool was used to examine the risk of publication bias in animal studies. After screening 2347 studies, 60 studies were included in this study. A meta-analysis was conducted for spinal cord injury (n = 52) and traumatic brain injury (n = 8). The results indicated that mesenchymal stem cell-derived extracellular vesicles treatment prominently promoted motor function recovery in spinal cord injury animals, including rat Basso, Beattie and Bresnahan locomotor rating scale scores (standardized mean difference [SMD]: 2.36, 95% confidence interval [CI]: 1.96-2.76, P < 0.01, I² = 71%) and mouse Basso Mouse Scale scores (SMD = 2.31, 95% CI: 1.57-3.04, P = 0.01, I² = 60%) compared with controls. Further, mesenchymal stem cell-derived extracellular vesicles treatment significantly promoted neurological recovery in traumatic brain injury animals, including the modified Neurological Severity Score (SMD = -4.48, 95% CI: -6.12 to -2.84, P < 0.01, I² = 79%) and Foot Fault Test (SMD = -3.26, 95% CI: -4.09 to -2.42, P = 0.28, I² = 21%) compared with controls. Subgroup analyses showed that characteristics may be related to the therapeutic effect of mesenchymal stem cell-derived extracellular vesicles. For Basso, Beattie and Bresnahan locomotor rating scale scores, the efficacy of allogeneic mesenchymal stem cell-derived extracellular vesicles was higher than that of xenogeneic mesenchymal stem cell-derived extracellular vesicles (allogeneic: SMD = 2.54, 95% CI: 2.05-3.02, P = 0.0116, I² = 65.5%; xenogeneic: SMD: 1.78, 95%CI: 1.1-2.45, P = 0.0116, I² = 74.6%). Mesenchymal stem cell-derived extracellular vesicles separated by ultrafiltration centrifugation combined with density gradient ultracentrifugation (SMD = 3.58, 95% CI: 2.62-4.53, P < 0.0001, I² = 31%) may be more effective than other EV isolation methods. For mouse Basso Mouse Scale scores, placenta-derived mesenchymal stem cell-derived extracellular vesicles worked better than bone mesenchymal stem cell-derived extracellular vesicles (placenta: SMD = 5.25, 95% CI: 2.45-8.06, P = 0.0421, I² = 0%; bone marrow: SMD = 1.82, 95% CI: 1.23-2.41, P = 0.0421, I² = 0%). For modified Neurological Severity Score, bone marrow-derived MSC-EVs worked better than adipose-derived MSC-EVs (bone marrow: SMD = -4.86, 95% CI: -6.66 to -3.06, P = 0.0306, I² = 81%; adipose: SMD = -2.37, 95% CI: -3.73 to -1.01, P = 0.0306, I² = 0%). Intravenous administration (SMD = -5.47, 95% CI: -6.98 to -3.97, P = 0.0002, I² = 53.3%) and dose of administration equal to 100 μg (SMD = -5.47, 95% CI: -6.98 to -3.97, P < 0.0001, I² = 53.3%) showed better results than other administration routes and doses. The heterogeneity of studies was small, and sensitivity analysis also indicated stable results. Last, the methodological quality of all trials was mostly satisfactory. In conclusion, in the treatment of traumatic central nervous system diseases, mesenchymal stem cell-derived extracellular vesicles may play a crucial role in promoting motor function recovery.

Stem Cell Therapy in Spinal Cord Injury-Induced Neurogenic Lower Urinary Tract Dysfunction

Spinal cord injury (SCI) is a devastating condition that enormously affects an individual's health and quality of life. Neurogenic lower urinary tract dysfunction (NLUTD) is one of the most important sequelae induced by SCI, causing complications including urinary tract infection, renal function deterioration, urinary incontinence, and voiding dysfunction. Current therapeutic methods for SCI-induced NLUTD mainly target on the urinary bladder, but the outcomes are still far from satisfactory. Stem cell therapy has gained increasing attention for years for its ability to rescue the injured spinal cord directly. Stem cell differentiation and their paracrine effects, including exosomes, are the proposed mechanisms to enhance the recovery from SCI. Several animal studies have demonstrated improvement in bladder function using mesenchymal stem cells (MSCs) and neural stem cells (NSCs). Human clinical trials also provide promising results in urodynamic parameters after MSC therapy. However, there is still uncertainty about the ideal treatment window and application protocol for stem cell therapy. Besides, data on the therapeutic effects regarding NSCs and stem cell-derived exosomes in SCI-related NLUTD are scarce. Therefore, there is a pressing need for further well-designed human clinical trials to translate the stem cell therapy into a formal therapeutic option for SCI-induced NLUTD.

The role of exosomes in central nervous system tissue regeneration and repair

Exosomes are membrane-bound vesicles secreted by various cell types into the extracellular environment and contain kinds of bioactive molecules. These molecules can mediate various biological processes such as cell differentiation, proliferation, and survival, making them attractive for tissue regeneration and repair. Owing to their nanoscale size, bilayer membrane structure, and receptor-mediated transcytosis, exosomes can cross the blood-brain barrier (BBB) and reach the central nervous system (CNS) tissue. Additionally, exosomes can be loaded with exogenous substances after isolation. It has been suggested that exosomes could be used as natural drug carriers to transport therapeutic agents across the BBB and have great potential for CNS disease therapy by promoting tissue regeneration and repair. Herein, we discuss perspectives on therapeutic strategies to treat neurodegenerative disease or spinal cord injury using a variety of cell types-derived exosomes with kinds of exosomal contents, as well as engineering strategies of specific functional and exosome administration routes.

Recent advances in endogenous neural stem/progenitor cell manipulation for spinal cord injury repair

Traumatic spinal cord injury (SCI) can cause severe neurological impairments. Clinically available treatments are quite limited, with unsatisfactory remediation effects. Residing endogenous neural stem/progenitor cells (eNSPCs) tend to differentiate towards astrocytes, leaving only a small fraction towards oligodendrocytes and even fewer towards neurons; this has been suggested as one of the reasons for the failure of autonomous neuronal regeneration. Thus, finding ways to recruit and facilitate the differentiation of eNSPCs towards neurons has been considered a promising strategy for the noninvasive and immune-compatible treatment of SCI. The present manuscript first introduces the responses of eNSPCs after exogenous interventions to boost endogenous neurogenesis in various SCI models. Then, we focus on state-of-art manipulation approaches that enhance the intrinsic neurogenesis capacity and reconstruct the hostile microenvironment, mainly consisting of pharmacological treatments, stem cell-derived exosome administration, gene therapy, functional scaffold implantation, inflammation regulation, and inhibitory element delineation. Facing the extremely complex situation of SCI, combined treatments are also highlighted to provide more clues for future relevant investigations.

The potential use of mesenchymal stem cells-derived exosomes as microRNAs delivery systems in different diseases

MicroRNAs (miRNAs) are a group of small non-coding RNAs that regulate gene expression by targeting mRNA. Moreover, it has been shown that miRNAs expression are changed in various diseases, such as cancers, autoimmune disease, infectious diseases, and neurodegenerative Diseases. The suppression of miRNA function can be easily attained by utilizing of anti-miRNAs. In contrast, an enhancement in miRNA function can be achieved through the utilization of modified miRNA mimetics. The discovery of appropriate miRNA carriers in the body has become an interesting subject for investigators. Exosomes (EXOs) therapeutic efficiency and safety for transferring different cellular biological components to the recipient cell have attracted significant attention for their capability as miRNA carriers. Mesenchymal stem cells (MSCs) are recognized to generate a wide range of EXOs (MSC-EXOs), showing that MSCs may be effective for EXO generation in a clinically appropriate measure as compared to other cell origins. MSC-EXOs have been widely investigated because of their immune attributes, tumor-homing attributes, and flexible characteristics. In this article, we summarized the features of miRNAs and MSC-EXOs, including production, purification, and miRNA loading methods of MSC-EXOs, and the modification of MSC-EXOs for targeted miRNA delivery in various diseases. Video abstract.