Exosomes from human adipose-derived stem cells promote sciatic nerve regeneration via optimizing Schwann cell function

The limelight of adipose-derived stem cells in the landscape of neural tissue engineering for peripheral nerve injury

BACKGROUND AND AIMS

Challenges in treating peripheral nerve injury include prolonged repair time and insufficient functional recovery. Stem cell therapy coupled with neural tissue engineering has been shown to induce nerve regeneration following peripheral nerve injury. Among these stem cells, adipose-derived stem cells (ADSCs) are preferred due to their accessibility, expansion, multidirectional differentiation, and production of essential nutrient factors for nerve growth. In recent years, ADSC-laden nerve guide conduit has been utilized to enhance the therapeutic effects of tissue-engineered nerve grafts. This review explores existing research that recognizes the roles played by ADSCs in inducing peripheral nerve regeneration following injury and summarizes the different methods of application of ADSC-laden nerve conduit in neural tissue engineering.

Beyond boundaries: The therapeutic potential of exosomes in neural microenvironments in neurological disorders

Neurological disorders are a diverse group of conditions that can significantly impact individuals' quality of life. The maintenance of neural microenvironment homeostasis is essential for optimal physiological cellular processes. Perturbations in this delicate balance underlie various pathological manifestations observed across various neurological disorders. Current treatments for neurological disorders face substantial challenges, primarily due to the formidable blood-brain barrier and the intricate nature of neural tissue structures. These obstacles have resulted in a paucity of effective therapies and inefficiencies in patient care. Exosomes, nanoscale vesicles that contain a complex repertoire of biomolecules, are identifiable in various bodily fluids. They hold substantial promise in numerous therapeutic interventions due to their unique attributes, including targeted drug delivery mechanisms and the ability to cross the BBB, thereby enhancing their therapeutic potential. In this review, we investigate the therapeutic potential of exosomes across a range of neurological disorders, including neurodegenerative disorders, traumatic brain injury, peripheral nerve injury, brain tumors, and stroke. Through both in vitro and in vivo studies, our findings underscore the beneficial influence of exosomes in enhancing the neural microenvironment following neurological diseases, offering promise for improved neural recovery and management in these conditions.

Advances in Exosome-Based Therapies for the Repair of Peripheral Nerve Injuries

Peripheral nerve injuries (PNIs) are the term used to describe injuries that occur to the nerve fibers of the peripheral nervous system (PNS). Such injuries may be caused by trauma, infection, or aberrant immunological response. Although the peripheral nervous system has a limited capacity for self-repair, in cases of severe damage, this process is either interrupted entirely or is only partially completed. The evaluation of variables that promote the repair of peripheral nerves has consistently been a focal point. Exosomes are a subtype of extracellular vesicles that originate from cellular sources and possess abundant proteins, lipids, and nucleic acids, play a critical role in facilitating intercellular communication. Due to their modifiable composition, they possess exceptional capabilities as carriers for therapeutic compounds, including but not limited to mRNAs or microRNAs. Exosome-based therapies have gained significant attention in the treatment of several nervous system diseases due to their advantageous properties, such as low toxicity, high stability, and limited immune system activation. The objective of this review article is to provide an overview of exosome-based treatments that have been developed in recent years for a range of PNIs, including nerve trauma, diabetic neuropathy, amyotrophic lateral sclerosis (ALS), glaucoma, and Guillain-Barre syndrome (GBS). It was concluded that exosomes could provide favorable results in the improvement of peripheral PNIs by facilitating the transfer of regenerative factors. The development of bioengineered exosome therapy for PNIs should be given more attention to enhance the efficacy of exosome treatment for PNIs.

Exosomes From Muscle-Derived Stem Cells Repair Peripheral Nerve Injury by Inhibiting Ferroptosis via the Keap1-Nrf2-Ho-1 Axis

Currently, the clinical outcomes of peripheral nerve injuries are suboptimal, highlighting the urgent need to understand the mechanisms of nerve injury to enhance treatment strategies. Muscle-derived stem cells (MDSCs) are a diverse group of multipotent cells that hold promise for peripheral nerve regeneration due to their strong antioxidant and regenerative properties. Our research has revealed that severe ferroptosis occurs in the sciatic nerve and ipsilateral dorsal root ganglion following sciatic nerve injury. Interestingly, we have observed that MDSC-derived exosomes effectively suppress cell ferroptosis and enhance cell viability in Schwann cells and dorsal root ganglion cells. Treatment with exosomes led to increased expression of BDNF and P62 in Schwann cells, decreased expression of Keap1, Nrf2, and HO-1 in Schwann cells, and upregulated dorsal root ganglion cells. Rats treated with exosomes exhibited improvements in sciatic nerve function, sensitivity to stimuli, and reduced muscle atrophy, indicating a positive impact on post-injury recovery. In conclusion, our findings demonstrate the occurrence of ferroptosis in the sciatic nerve and dorsal root ganglion post-injury, with MDSC exosomes offering a potential therapeutic strategy by inhibiting ferroptosis, activating the Keap1-Nrf2-HO-1 pathway, and optimizing the post-injury repair environment.

Exosomes repairment for sciatic nerve injury: a cell-free therapy

Sciatic nerve injury (SNI) is a common type of peripheral nerve injury typically resulting from trauma, such as contusion, sharp force injuries, drug injections, pelvic fractures, or hip dislocations. It leads to both sensory and motor dysfunctions, characterized by pain, numbness, loss of sensation, muscle atrophy, reduced muscle tone, and limb paralysis. These symptoms can significantly diminish a patient's quality of life. Following SNI, Wallerian degeneration occurs, which activates various signaling pathways, inflammatory factors, and epigenetic regulators. Despite the availability of several surgical and nonsurgical treatments, their effectiveness remains suboptimal. Exosomes are extracellular vesicles with diameters ranging from 30 to 150 nm, originating from the endoplasmic reticulum. They play a crucial role in facilitating intercellular communication and have emerged as highly promising vehicles for drug delivery. Increasing evidence supports the significant potential of exosomes in repairing SNI. This review delves into the pathological progression of SNI, techniques for generating exosomes, the molecular mechanisms behind SNI recovery with exosomes, the effectiveness of combining exosomes with other approaches for SNI repair, and the changes and future outlook for utilizing exosomes in SNI recovery.

Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes as Nanomedicine for Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a complex and protracted process, and existing therapeutic approaches struggle to achieve effective nerve regeneration. Recent studies have shown that mesenchymal stem cells (MSCs) may be a pivotal choice for treating peripheral nerve injury. MSCs possess robust paracrine capabilities, and exosomes, as the primary secretome of MSCs, are considered crucial regulatory mediators involved in peripheral nerve regeneration. Exosomes, as nanocarriers, can transport various endogenous or exogenous bioactive substances to recipient cells, thereby promoting vascular and axonal regeneration while suppressing inflammation and pain. In this review, we summarize the mechanistic roles of exosomes derived from MSCs in peripheral nerve regeneration, discuss the engineering strategies for MSC-derived exosomes to improve therapeutic potential, and explore the combined effects of MSC-derived exosomes with biomaterials (nerve conduits, hydrogels) in peripheral nerve regeneration.

Adipose Tissue Derivatives in Peripheral Nerve Regeneration after Transection: A Systematic Review

INTRODUCTION

Peripheral nerve injury (PNI) is increasingly prevalent and challenging to treat despite advances in microsurgical techniques. In this context, adipose tissue derivatives, such as adipose-derived stem cells, nanofat, and stromal vascular fraction have been gaining attention as potential allies in peripheral nerve regeneration.

OBJECTIVES

This study aims to explore the use of adipose tissue derivatives in nerve regeneration following peripheral nerve transection in murine models. Thus, we assess and synthesize the key techniques and methods used for evaluating the obtained nerve regeneration to guide future experimental research and clinical interventions.

METHODOLOGY

A systematic review was conducted in February 2024, adhering to the Cochrane and PRISMA 2020 guidelines, using the PubMed, SciELO, and LILACS databases. The focus was on experimental studies involving adipose tissue derivatives in nerve regeneration in animal models post-transection. Only experimental trials reporting nerve regeneration outcomes were included; studies lacking a comparator group or evaluation methods were excluded.

RESULTS

Out of 273 studies initially identified from MEDLINE, 19 were selected for detailed analysis. The average study included 32.5 subjects, with about 10.2 subjects per intervention subgroup. The predominant model was the sciatic nerve injury with a 10 mm gap. The most common intervention involved unprocessed adipose-derived stem cells, utilized in 14 articles.

CONCLUSIONS

This review underscores the significant potential of current methodologies in peripheral nerve regeneration, particularly highlighting the use of murine models and thorough evaluation techniques.

Therapeutic Potential and Challenges of Mesenchymal Stem Cell-Derived Exosomes for Peripheral Nerve Regeneration: A Systematic Review

Gap injuries to the peripheral nervous system result in pain and loss of function, without any particularly effective therapeutic options. Within this context, mesenchymal stem cell (MSC)-derived exosomes have emerged as a potential therapeutic option. Thus, the focus of this study was to review currently available data on MSC-derived exosome-mounted scaffolds in peripheral nerve regeneration in order to identify the most promising scaffolds and exosome sources currently in the field of peripheral nerve regeneration. We conducted a systematic review following PRISMA 2020 guidelines. Exosome origins varied (adipose-derived MSCs, bone marrow MSCs, gingival MSC, induced pluripotent stem cells and a purified exosome product) similarly to the materials (Matrigel, alginate and silicone, acellular nerve graft [ANG], chitosan, chitin, hydrogel and fibrin glue). The compound muscle action potential (CMAP), sciatic functional index (SFI), gastrocnemius wet weight and histological analyses were used as main outcome measures. Overall, exosome-mounted scaffolds showed better regeneration than scaffolds alone. Functionally, both exosome-enriched chitin and ANG showed a significant improvement over time in the sciatica functional index, CMAP and wet weight. The best histological outcomes were found in the exosome-enriched ANG scaffold with a high increase in the axonal diameter and muscle cross-section area. Further studies are needed to confirm the efficacy of exosome-mounted scaffolds in peripheral nerve regeneration.

Recent advances in the use of extracellular vesicles from adipose-derived stem cells for regenerative medical therapeutics

Adipose-derived stem cells (ADSCs) are a subset of mesenchymal stem cells (MSCs) isolated from adipose tissue. They possess remarkable properties, including multipotency, self-renewal, and easy clinical availability. ADSCs are also capable of promoting tissue regeneration through the secretion of various cytokines, factors, and extracellular vesicles (EVs). ADSC-derived EVs (ADSC-EVs) act as intercellular signaling mediators that encapsulate a range of biomolecules. These EVs have been found to mediate the therapeutic activities of donor cells by promoting the proliferation and migration of effector cells, facilitating angiogenesis, modulating immunity, and performing other specific functions in different tissues. Compared to the donor cells themselves, ADSC-EVs offer advantages such as fewer safety concerns and more convenient transportation and storage for clinical application. As a result, these EVs have received significant attention as cell-free therapeutic agents with potential future application in regenerative medicine. In this review, we focus on recent research progress regarding regenerative medical use of ADSC-EVs across various medical conditions, including wound healing, chronic limb ischemia, angiogenesis, myocardial infarction, diabetic nephropathy, fat graft survival, bone regeneration, cartilage regeneration, tendinopathy and tendon healing, peripheral nerve regeneration, and acute lung injury, among others. We also discuss the underlying mechanisms responsible for inducing these therapeutic effects. We believe that deciphering the biological properties, therapeutic effects, and underlying mechanisms associated with ADSC-EVs will provide a foundation for developing a novel therapeutic approach in regenerative medicine.

A quick and innovative pipeline for producing chondrocyte-homing peptide-modified extracellular vesicles by three-dimensional dynamic culture of hADSCs spheroids to modulate the fate of remaining ear chondrocytes in the M1 macrophage-infiltrated microenvironment

BACKGROUND

Extracellular vesicles (EVs) derived from human adipose-derived mesenchymal stem cells (hADSCs) have shown great therapeutic potential in plastic and reconstructive surgery. However, the limited production and functional molecule loading of EVs hinder their clinical translation. Traditional two-dimensional culture of hADSCs results in stemness loss and cellular senescence, which is unfavorable for the production and functional molecule loading of EVs. Recent advances in regenerative medicine advocate for the use of three-dimensional culture of hADSCs to produce EVs, as it more accurately simulates their physiological state. Moreover, the successful application of EVs in tissue engineering relies on the targeted delivery of EVs to cells within biomaterial scaffolds.

METHODS AND RESULTS

The hADSCs spheroids and hADSCs gelatin methacrylate (GelMA) microspheres are utilized to produce three-dimensional cultured EVs, corresponding to hADSCs spheroids-EVs and hADSCs microspheres-EVs respectively. hADSCs spheroids-EVs demonstrate excellent production and functional molecule loading compared with hADSCs microspheres-EVs. The upregulation of eight miRNAs (i.e. hsa-miR-486-5p, hsa-miR-423-5p, hsa-miR-92a-3p, hsa-miR-122-5p, hsa-miR-223-3p, hsa-miR-320a, hsa-miR-126-3p, and hsa-miR-25-3p) and the downregulation of hsa-miR-146b-5p within hADSCs spheroids-EVs show the potential of improving the fate of remaining ear chondrocytes and promoting cartilage formation probably through integrated regulatory mechanisms. Additionally, a quick and innovative pipeline is developed for isolating chondrocyte homing peptide-modified EVs (CHP-EVs) from three-dimensional dynamic cultures of hADSCs spheroids. CHP-EVs are produced by genetically fusing a CHP at the N-terminus of the exosomal surface protein LAMP2B. The CHP + LAMP2B-transfected hADSCs spheroids were cultured with wave motion to promote the secretion of CHP-EVs. A harvesting method is used to enable the time-dependent collection of CHP-EVs. The pipeline is easy to set up and quick to use for the isolation of CHP-EVs. Compared with nontagged EVs, CHP-EVs penetrate the biomaterial scaffolds and specifically deliver the therapeutic miRNAs to the remaining ear chondrocytes. Functionally, CHP-EVs show a major effect on promoting cell proliferation, reducing cell apoptosis and enhancing cartilage formation in remaining ear chondrocytes in the M1 macrophage-infiltrated microenvironment.

CONCLUSIONS

In summary, an innovative pipeline is developed to obtain CHP-EVs from three-dimensional dynamic culture of hADSCs spheroids. This pipeline can be customized to increase EVs production and functional molecule loading, which meets the requirements for regulating remaining ear chondrocyte fate in the M1 macrophage-infiltrated microenvironment.

Clinical Applications of Adipose-Derived Stem Cell (ADSC) Exosomes in Tissue Regeneration

Adipose-derived stem cells (ADSCs) are mesenchymal stem cells with a great potential for self-renewal and differentiation. Exosomes derived from ADSCs (ADSC-exos) can imitate their functions, carrying cargoes of bioactive molecules that may affect specific cellular targets and signaling processes. Recent evidence has shown that ADSC-exos can mediate tissue regeneration through the regulation of the inflammatory response, enhancement of cell proliferation, and induction of angiogenesis. At the same time, they may promote wound healing as well as the remodeling of the extracellular matrix. In combination with scaffolds, they present the future of cell-free therapies and promising adjuncts to reconstructive surgery with diverse tissue-specific functions and minimal adverse effects. In this review, we address the main characteristics and functional properties of ADSC-exos in tissue regeneration and explore their most recent clinical application in wound healing, musculoskeletal regeneration, dermatology, and plastic surgery as well as in tissue engineering.

Applications of Stem Cell-Derived Extracellular Vesicles in Nerve Regeneration

Extracellular vesicles (EVs), including exosomes, microvesicles, and other lipid vesicles derived from cells, play a pivotal role in intercellular communication by transferring information between cells. EVs secreted by progenitor and stem cells have been associated with the therapeutic effects observed in cell-based therapies, and they also contribute to tissue regeneration following injury, such as in orthopaedic surgery cases. This review explores the involvement of EVs in nerve regeneration, their potential as drug carriers, and their significance in stem cell research and cell-free therapies. It underscores the importance of bioengineers comprehending and manipulating EV activity to optimize the efficacy of tissue engineering and regenerative therapies.

Mesenchymal stem cells' "garbage bags" at work: Treating radial nerve injury with mesenchymal stem cell-derived exosomes

Unlike central nervous system injuries, peripheral nerve injuries (PNIs) are often characterized by more or less successful axonal regeneration. However, structural and functional recovery is a senile process involving multifaceted cellular and molecular processes. The contemporary treatment options are limited, with surgical intervention as the gold-standard method; however, each treatment option has its associated limitations, especially when the injury is severe with a large gap. Recent advancements in cell-based therapy and cell-free therapy approaches using stem cell-derived soluble and insoluble components of the cell secretome are fast-emerging therapeutic approaches to treating acute and chronic PNI. The recent pilot study is a leap forward in the field, which is expected to pave the way for more enormous, systematic, and well-designed clinical trials to assess the therapeutic efficacy of mesenchymal stem cell-derived exosomes as a bio-drug either alone or as part of a combinatorial approach, in an attempt synergize the best of novel treatment approaches to address the complexity of the neural repair and regeneration.

The Rejuvenation and Functional Restoration of Aged Adipose Stem Cells by DUXAP10 Knockdown via the Regulation of the miR-214-3p/RASSF5 Axis

Adipose stem cell (ASC)-based therapies provide an encouraging option for tissue repair and regeneration. However, the function of these cells declines with aging, which limits their clinical transformation. Recent studies have outlined the involvement of long non-coding RNAs in stem cell aging. Here, we reanalyzed our published RNA sequencing (RNA-seq) data profiling differences between ASCs from young and old donors and identified a lncRNA named double homeobox A pseudogene 10 (DUXAP10) as significantly accumulated in aged ASCs. Knocking down DUXAP10 promoted stem cell proliferation and migration and halted cell senescence and the secretion of proinflammatory cytokines. In addition, DUXAP10 was located in the cytoplasm and functioned as a decoy for miR-214-3p. miR-214-3p was downregulated in aged ASCs, and its overexpression rejuvenated aged ASCs and reversed the harm caused by DUXAP10. Furthermore, Ras Association Domain Family Member 5 (RASSF5) was the target of miR-214-3p and was upregulated in aged ASCs. Overexpressing DUXAP10 and inhibiting miR-214-3p both enhanced RASSF5 content in ASCs, while DUXAP10 knockdown promoted the therapeutic ability of aged ASCs for skin wound healing. Overall, this study offers new insights into the mechanism of age-related ASC dysfunction and names DUXAP10 and miR-214-3p as potential targets for energizing aged stem cells.

The effects of exosomes originating from different cell sources on the differentiation of bone marrow mesenchymal stem cells into schwann cells

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs) can differentiate into Schwann cells (SCs) during peripheral nerve injury; in our previous research, we showed that SC-derived exosomes (SC-exos) played a direct induction role while fibroblast-derived exosomes (Fb-exos) had no obvious induction role. The induction role of neural stem cell (NSC)-derived exosomes (NSC-exos) has also been widely confirmed. However, no studies have compared the induction effects of these three types of cells at the same time. Therefore, by investigating the effect of these three cell-derived exosomes upon the induction of BMSCs to differentiate into SCs, this study explored the role of different exosomes in promoting the differentiation of stem cells into SCs cells, and conducted a comparison between the two groups by RNA sequencing to further narrow the range of target genes and related gene pathways in order to study their related mechanisms.

MATERIALS AND METHODS

We extracted exosomes from SCs, fibroblasts (Fb) and neural stem cells (NSC) and then investigated the ability of these exosomes to induce differentiation into BMSCs under different culture conditions. The expression levels of key proteins and gene markers were detected in induced cells by fluorescence immunoassays, western blotting and polymerase chain reaction (PCR); then, we statistically compared the relative induction effects under different conditions. Finally, we analyzed the three types of exosomes by RNA-seq to predict target genes and related gene pathways.

RESULTS

BMSCs were cultured by three media: conventional (no induction), pre-induction or pre-induction + original induction medium (ODM) with exosomes of the same cell origin under different culture conditions. When adding the three different types of exosomes separately, the overall induction of BMSCs to differentiate into SCs was significantly increased (P < 0.05). The induction ability was ranked as follows: pre-induction + ODM + exosome group > pre-induction + exosome group > non-induction + exosome group. Using exosomes from different cell sources under the same culture conditions, we observed the following trends under the three culture conditions: RSC96-exos group ≥ NSC-exos group > Fb-exos group. The overall ability to induce BMSCs into SCs was significantly greater in the RSC96-exos group and the NSC-exos group. Although there was no significant difference in induction efficiency when comparing these two groups, the overall induction ability of the RSC96-exos group was slightly higher than that of the NSC-exos group. By combining the differentiation induction results with the RNA-seq data, the three types of exosomes were divided into three comparative groups: RSC vs. NSC, RSC vs. Fb and NSC vs. Fb. We identified 203 differentially expressed mRNA target genes in these three groups. Two differentially expressed genes were upregulated simultaneously, namely riboflavin kinase (RFK, ENSRNOG00000022273) and ribosomal RNA processing 36 (Rrp36, ENSRNOG00000017836). We did not identify any co-upregulated target genes for the miRNAs, but did identify one target gene of the lncRNAs, namely ENSRNOG00000065005. Analysis identified 90 GO terms related to nerves and axons in the mRNAs; in addition, KEGG enrichment and GASA analysis identified 13 common differential expression pathways in the three groups.

CONCLUSIONS

Our analysis found that pre-induction + ODM + RSC96/NSC-exos culture conditions were most conducive with regards to induction and differentiation. RSC96-exos and NSC-exos exhibited significantly greater differentiation efficiency of BMSCs into SCs. Although there was no statistical difference, the data indicated a trend for RSC96-exos to be advantageous We identified 203 differentially expressed mRNAs between the three groups and two differentially expressed target mRNAs were upregulated, namely riboflavin kinase (RFK, ENSRNOG00000022273) and ribosomal RNA processing 36 (Rrp36, ENSRNOG00000017836). 90 GO terms were related to nerves and axons. Finally, we identified 13 common differentially expressed pathways across our three types of exosomes. It is hoped that the efficiency of BMSCs induction differentiation into SCs can be improved, bringing hope to patients and more options for clinical treatment.

Platelet-rich plasma-derived exosomes boost mesenchymal stem cells to promote peripheral nerve regeneration

Peripheral nerve injury (PNI) remains a severe clinical problem with debilitating consequences. Mesenchymal stem cell (MSC)-based therapy is promising, but the problems of poor engraftment and insufficient neurotrophic effects need to be overcome. Herein, we isolated platelet-rich plasma-derived exosomes (PRP-Exos), which contain abundant bioactive molecules, and investigated their potential to increase the regenerative capacity of MSCs. We observed that PRP-Exos significantly increased MSC proliferation, viability, and mobility, decreased MSC apoptosis under stress, maintained MSC stemness, and attenuated MSC senescence. In vivo, PRP-Exo-treated MSCs (pExo-MSCs) exhibited an increased retention rate and heightened therapeutic efficacy, as indicated by increased axonal regeneration, remyelination, and recovery of neurological function in a PNI model. In vitro, pExo-MSCs coculture promoted Schwann cell proliferation and dorsal root ganglion axon growth. Moreover, the increased neurotrophic behaviour of pExo-MSCs was mediated by trophic factors, particularly glia-derived neurotrophic factor (GDNF), and PRP-Exos activated the PI3K/Akt signalling pathway in MSCs, leading to the observed phenotypes. These findings demonstrate that PRP-Exos may be novel agents for increasing the ability of MSCs to promote neural repair and regeneration in patients with PNI.

MiR-145-5p overexpression rejuvenates aged adipose stem cells and accelerates wound healing

Adipose-derived stem cells (ADSCs) have been widely applied in translational and regenerative medicine. During aging, there is a recognized functional decline in ADSCs, which compromises their therapeutic effectiveness. Currently, the mechanisms of aging-induced stem cell dysfunction remain unclear, hence there is a need to elucidate these mechanisms and propose strategies for reversing this functional impairment. In this study, we found that ADSCs isolated from old donors (O-ADSCs) presented inferior phenotypes and decreased miR-145-5p levels compared to those from young donors (Y-ADSCs). To interrogate the role of miR-145-5p in ADSCs, gain- and loss-of-function assays were performed. The results indicated that miR-145-5p overexpression in O-ADSCs promoted cellular proliferation and migration, while reducing cell senescence. Further study demonstrated that miR-145-5p could regulate ADSCs function by targeting bone morphogenetic protein binding endothelial cell precursor-derived regulator (BMPER), which is a crucial modulator in angiogenesis. Moreover, in vivo experiments showed that miR-145-5p-overexpressing O-ADSCs accelerated wound healing by promoting wound re-epithelialization and angiogenesis. Collectively, this study indicates that miR-145-5p works as a positive regulator for optimizing O-ADSCs function, and may be a novel therapeutic target for restoring aging-associated impairments in stem cell function.

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.

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.

Enhancing Functional Recovery after Segmental Nerve Defect Using Nerve Allograft Treated with Plasma-Derived Exosome

BACKGROUND

Nerve injuries can result in detrimental functional outcomes. Currently, autologous nerve graft offers the best outcome for segmental peripheral nerve injury. Allografts are alternatives, but do not have comparable results. This study evaluated whether plasma-derived exosome can improve nerve regeneration and functional recovery when combined with decellularized nerve allografts.

METHODS

The effect of exosomes on Schwann cell proliferation and migration were evaluated. A rat model of sciatic nerve repair was used to evaluate the effect on nerve regeneration and functional recovery. A fibrin sealant was used as the scaffold for exosome. Eighty-four Lewis rats were divided into autograft, allograft, and allograft with exosome groups. Gene expression of nerve regeneration factors was analyzed on postoperative day 7. At 12 and 16 weeks, rats were subjected to maximum isometric tetanic force and compound muscle action potential. Nerve specimens were then analyzed by means of histology and immunohistochemistry.

RESULTS

Exosomes were readily taken up by Schwann cells that resulted in improved Schwann cell viability and migration. The treated allograft group had functional recovery (compound muscle action potential, isometric tetanic force) comparable to that of the autograft group. Similar results were observed in gene expression analysis of nerve regenerating factors. Histologic analysis showed no statistically significant differences between treated allograft and autograft groups in terms of axonal density, fascicular area, and myelin sheath thickness.

CONCLUSIONS

Plasma-derived exosome treatment of decellularized nerve allograft may provide comparable clinical outcomes to that of an autograft. This can be a promising strategy in the future as an alternative for segmental peripheral nerve repair.

CLINICAL RELEVANCE STATEMENT

Off-the-shelf exosomes may improve recovery in nerve allografts.

Schwann Cell-Derived Exosomes Ameliorate Paclitaxel-Induced Peripheral Neuropathy Through the miR-21-Mediated PTEN Signaling Pathway

Paclitaxel-induced peripheral neuropathy (PIPN) is a neurological disorder resulting from paclitaxel (PTX) treatment for cancer patients. There are currently no drugs available that can definitively prevent or treat PIPN. Exosomes are cell-secreted nanoscale vesicles that mediate communication between neurons and glial cells. We found that Schwann cell-derived exosomes (SC-EXOs) robustly improved PIPN both in vitro and in vivo. In vivo studies showed that SC-EXOs were able to alleviate PTX-induced mechanical nociceptive sensitization in rats. Pathomorphological analysis showed that SC-EXOs ameliorated PTX-induced plantar intraepidermal nerve fiber loss and dorsal root ganglion (DRG) injury. Additionally, the results of in vitro studies showed that SC-EXOs had significant protective effects on the DRG cells damaged by PTX, and did not affect the antitumor effect of PTX against Hela cells. Further, mechanism research revealed that SC-EXOs promoted axonal regeneration and protected damaged neurons by upregulating miR-21 to repress the phosphatase and tensin homolog (PTEN) pathway, which could improve PIPN. Taken together, these findings suggest that SC-EXOs ameliorate PTX-induced peripheral neuropathy via the miR-21-mediated PTEN signaling pathway, which provides a novel strategy for the treatment of PIPN.

Ultrasound-Targeted Microbubble Destruction Assisted Delivery of Platelet-Rich Plasma-Derived Exosomes Promoting Peripheral Nerve Regeneration

Peripheral nerve injury is prevalent and has a high disability rate in clinical settings. Current therapeutic methods have not achieved satisfactory efficacy, underscoring the need for novel approaches to nerve restoration that remains an active area of research in neuroscience and regenerative medicine. In this study, we isolated platelet-rich plasma-derived exosomes (PRP-exos) and found that they can significantly enhance the proliferation, migration, and secretion of trophic factors by Schwann cells (SCs). In addition, there were marked changes in transcriptional and expression profiles of SCs, particularly via the upregulation of genes related to biological functions involved in nerve regeneration and repair. In the rat model of sciatic nerve crush injury, ultrasound-targeted microbubble destruction (UTMD) enhanced the efficiency of PRP-exos delivery to the injury site. This approach ensured a high concentration of PRP-exos in the injured nerve and improved the therapeutic outcomes. In conclusion, PRP-exos may promote nerve regeneration and repair, and UTMD may increase the effectiveness of targeted PRP-exos delivery to the injured nerve and enhance the therapeutic effect.

White adipose tissue-derived small extracellular vesicles: A new potential therapeutic reagent for accelerating diabetic wound healing

Small extracellular vesicles (sEVs) from adipose-derived stem cells (ADSCs) have gained great attention and have been widely used in cell-free therapies for treating diabetic non-healing wounds in recent years. However, further clinical application of ADSC-sEVs have been limited due to their unsolvable defects, including cumbersome extraction procedure, high cost, low yield, etc. Thus, we urgently need to find one therapeutic reagent that could not only accelerate diabetic wound healing as ADSC-sEVs but also overcome these shortcomings. As the extraction process of adipose tissue-derived sEVs (AT-sEVs) is quite simple and labor saving, we put our focus on the efficiencies of white adipose tissue-derived sEVs (WAT-sEVs) and brown adipose tissue-derived sEVs (BAT-sEVs) in diabetic wound repair. After successfully isolating WAT-sEVs and BAT-sEVs by ultracentrifugation, we thoroughly characterized them and compared their diabetic wound healing capabilities both in vitro and in vivo. According to our study, AT-sEVs possess similar competence in diabetic wound healing as compared with ADSC-sEVs. While the effect of BAT-sEVs is not as stable as WAT-sEVs and ADSC-sEVs, the repair efficiency is also slightly lower than the other two sEVs in some cases. In summary, we are the first to discover that WAT-sEVs show great potential in diabetic wound repair. With advantages that are specific to tissue-derived sEVs (Ti-sEVs) such as time- and cost-saving, high-yield, and simple isolation procedure, we believe WAT-sEVs could serve as a novel reliable cell-free therapy for clinical diabetic wound treatment.

Deciphering the role of extrachromosomal circular DNA in adipose stem cells from old and young donors

BACKGROUND

The functional impairment of adipose stem cells (ASCs) during aging limits their clinical transformation. Studies have shown that extrachromosomal circular DNAs (eccDNAs) are associated with tumor progression and cell aging, but the roles of eccDNAs in ASCs remain unknown.

METHOD

We conducted Circle sequencing (Circle-seq) to identify eccDNAs in ASCs isolated from young and old donors. The differentially expressed eccDNAs were calculated, annotated and validated via polymerase chain reaction.

RESULTS

Thousands of eccDNAs were identified and comprehensively characterized. Most of them were GC-rich, < 1000 base pairs in size, and were enriched on chromosome 19 and 17 with a high density of Alu elements and genes, 2 kb upstream/downstream of genes and satellites. In total, 3025 eccDNAs were differentially expressed among the two ASC groups. Conjoint analysis of the Circle-seq results and previous RNA-seq results revealed that 73 eccDNAs and 55 genes exhibited the same differential expression between the two groups. KEGG and GO analyses revealed that genes encoding differentially expressed eccDNAs were enriched for cell adhesion, cellular senescence and TGF-β receptor signaling pathway. We also found that aged ASCs exhibited loss of eccDNAs, including CAMK2G (chr10: 75577899-75578176), TRABD2B (chr1: 48305638-48307008) and TRABD2B (chr1: 48305425-48307091).

CONCLUSION

In this study, we elucidated the first eccDNA profile relating to ASCs and demonstrated that three eccDNAs are lost in aged ASCs, which may be potential biomarkers of stem cell aging and valuable targets for stem cell rejuvenation.

Mesenchymal stem cell-derived extracellular vesicles in skin wound healing: roles, opportunities and challenges

Skin wounds are characterized by injury to the skin due to trauma, tearing, cuts, or contusions. As such injuries are common to all human groups, they may at times represent a serious socioeconomic burden. Currently, increasing numbers of studies have focused on the role of mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) in skin wound repair. As a cell-free therapy, MSC-derived EVs have shown significant application potential in the field of wound repair as a more stable and safer option than conventional cell therapy. Treatment based on MSC-derived EVs can significantly promote the repair of damaged substructures, including the regeneration of vessels, nerves, and hair follicles. In addition, MSC-derived EVs can inhibit scar formation by affecting angiogenesis-related and antifibrotic pathways in promoting macrophage polarization, wound angiogenesis, cell proliferation, and cell migration, and by inhibiting excessive extracellular matrix production. Additionally, these structures can serve as a scaffold for components used in wound repair, and they can be developed into bioengineered EVs to support trauma repair. Through the formulation of standardized culture, isolation, purification, and drug delivery strategies, exploration of the detailed mechanism of EVs will allow them to be used as clinical treatments for wound repair. In conclusion, MSC-derived EVs-based therapies have important application prospects in wound repair. Here we provide a comprehensive overview of their current status, application potential, and associated drawbacks.

Stem cells and extracellular vesicles to improve preclinical orofacial soft tissue healing

Orofacial soft tissue wounds caused by surgery for congenital defects, trauma, or disease frequently occur leading to complications affecting patients' quality of life. Scarring and fibrosis prevent proper skin, mucosa and muscle regeneration during wound repair. This may hamper maxillofacial growth and speech development. To promote the regeneration of injured orofacial soft tissue and attenuate scarring and fibrosis, intraoral and extraoral stem cells have been studied for their properties of facilitating maintenance and repair processes. In addition, the administration of stem cell-derived extracellular vesicles (EVs) may prevent fibrosis and promote the regeneration of orofacial soft tissues. Applying stem cells and EVs to treat orofacial defects forms a challenging but promising strategy to optimize treatment. This review provides an overview of the putative pitfalls, promises and the future of stem cells and EV therapy, focused on orofacial soft tissue regeneration.

Current aspects of small extracellular vesicles in pain process and relief

Small extracellular vesicles (sEVs) have been identified as a noteworthy paracrine mechanism of intercellular communication in diagnosing and managing neurological disorders. Current research suggests that sEVs play a pivotal role in the pathological progression of pain, emphasizing their critical function in the pathological progression of pain in acute and chronic pain models. By facilitating the transfer of diverse molecules, such as proteins, nucleic acids, and metabolites, sEVs can modulate pain signaling transmission in both the central and peripheral nervous systems. Furthermore, the unique molecules conveyed by sEVs in pain disorders indicate their potential as diagnostic biomarkers. The application of sEVs derived from mesenchymal stem cells (MSCs) in regenerative pain medicine has emerged as a promising strategy for pain management. Moreover, modified sEVs have garnered considerable attention in the investigation of pathological processes and therapeutic interventions. This review presents a comprehensive overview of the current knowledge regarding the involvement of sEVs in pain pathogenesis and treatment. Nevertheless, additional research is imperative to facilitate their clinical implementation. Schematic diagram of sEVs in the biogenesis, signal transmission, diagnosis, and treatment of pain disorders. Small extracellular vesicles (sEVs) are secreted by multiple cells, loading with various biomolecules, such as miRNAs, transmembrane proteins, and amino acids. They selectively target other cells and regulating pain signal transmission. The composition of sEVs can serve as valuable biomarkers for pain diagnosis. In particular, mesenchymal stem cell-derived sEVs have shown promise as regenerative medicine for managing multiple pain disorders. Furthermore, by modifying the structure or contents of sEVs, they could potentially be used as a potent analgesic method.

Stem cell-derived extracellular vesicle-based therapy for nerve injury: A review of the molecular mechanisms

Recent evidence suggests that stem cell therapy has beneficial effects on nerve damage. These beneficial effects were subsequently found to be exerted in part in a paracrine manner by the release of extracellular vesicles. Stem cell-secreted extracellular vesicles have shown great potential to reduce inflammation and apoptosis, optimize the function of Schwann cells, regulate genes related to regeneration, and improve behavioral performance after nerve damage. This review summarizes the current knowledge on the effect of stem cell-derived extracellular vesicles on neuroprotection and regeneration along with their molecular mechanisms after nerve damage.

Chitosan Nerve Grafts Incorporated with SKP-SC-EVs Induce Peripheral Nerve Regeneration

BACKGROUND

Repair of long-distance peripheral nerve defects remains an important clinical problem. Nerve grafts incorporated with extracellular vesicles (EVs) from various cell types have been developed to bridge peripheral nerve defects. In our previous research, EVs obtained from skin-derived precursor Schwann cells (SKP-SC-EVs) were demonstrated to promote neurite outgrowth in cultured cells and facilitate nerve regeneration in animal studies.

METHODS

To further assess the functions of SKP-SC-EVs in nerve repair, we incorporated SKP-SC-EVs and Matrigel into chitosan nerve conduits (EV-NG) for repairing a 15-mm long-distance sciatic nerve defect in a rat model. Behavioral analysis, electrophysiological recording, histological investigation, molecular analysis, and morphometric assessment were carried out.

RESULTS

The results revealed EV-NG significantly improved motor and sensory function recovery compared with nerve conduits (NG) without EVs incorporation. The outgrowth and myelination of regenerated axons were improved, while the atrophy of target muscles induced by denervation was alleviated after EVs addition.

CONCLUSION

Our data indicated SKP-SC-EVs incorporation into nerve grafts represents a promising method for extended peripheral nerve damage repair.

Biological nerve conduit model with de-epithelialized human amniotic membrane and adipose-derived mesenchymal stem cell sheet for repair of peripheral nerve defects

In this study, a biological conduit, consisting of an adipocyte-derived mesenchymal stem cell (AdMSCs) sheet and amniotic membrane (AM), was designed for the reconstruction of peripheral nerve defects. To evaluate the effect of the produced conduit on neural regeneration, a 10-mm sciatic nerve defect was created in rats, and experiments were carried out on six groups, i.e., sham control group (SC), negative control group (NC), nerve autograft group (NG), the biological conduit (AdMSCs + AM) group, the commercial PGA tube conduit (PGA) group, and the conduit only consisting of AM (AM) group. The effects of different nerve repair methods on the peripheral nerve and gastrocnemius muscle were evaluated by functional, histological, and immunohistochemical tests. When the number of myelinated axons was compared between the groups of AdMSCs + AM and PGA, it was higher in the AdMSCs + AM group (p < 0.05). The percentage of gastrocnemius collagen bundle area of AdMSCs + AM group was found to be statistically lower than the PGA group (p < 0.05). The muscle fiber diameter of AdMSCs + AM group was lower than that of the NG group, but significantly higher than that of the PGA group and the AM group (p < 0.001). Muscle weight index was significantly higher in the AdMSCs + AM group compared to the PGA group (p < 0.05). It was observed that nerve regeneration was faster in the AdMSCs + AM group, and there was an earlier improvement in pin-prick score and sciatic functional index compared to the PGA group and the AM group. In conclusion, the biological conduit prepared from the AdMSCs sheet and AM is regarded as a new biological conduit that can be used as an alternative treatment method to nerve autograft in clinical applications.

Benefit of Adjuvant Mesenchymal Stem Cell Transplantation to Critical-Sized Peripheral Nerve Defect Repair: A Systematic Review and Meta-Analysis of Preclinical Studies

Critically sized nerve defects cause devastating life-long disabilities and require interposition for reconstruction. Additional local application of mesenchymal stem cells (MSCs) is considered promising to enhance peripheral nerve regeneration. To better understand the role of MSCs in peripheral nerve reconstruction, we performed a systematic review and meta-analysis of the effects of MSCs on critically sized segment nerve defects in preclinical studies. 5146 articles were screened following PRISMA guidelines using PubMed and Web of Science. A total of 27 preclinical studies (n = 722 rats) were included in the meta-analysis. The mean difference or the standardized mean difference with 95% confidence intervals for motor function, conduction velocity, and histomorphological parameters of nerve regeneration, as well as the degree of muscle atrophy, was compared in rats with critically sized defects and autologous nerve reconstruction treated with or without MSCs. The co-transplantation of MSCs increased the sciatic functional index (3.93, 95% CI 2.62 to 5.24, p < 0.00001) and nerve conduction velocity recovery (1.49, 95% CI 1.13 to 1.84, p = 0.009), decreased the atrophy of targeted muscles (gastrocnemius: 0.63, 95% CI 0.29 to 0.97 p = 0.004; triceps surae: 0.08, 95% CI 0.06 to 0.10 p = 0.71), and promoted the regeneration of injured axons (axon number: 1.10, 95% CI 0.78 to 1.42, p < 0.00001; myelin sheath thickness: 0.15, 95% CI 0.12 to 0.17, p = 0.28). Reconstruction of critically sized peripheral nerve defects is often hindered by impaired postoperative regeneration, especially in defects that require an autologous nerve graft. This meta-analysis indicates that additional application of MSC can enhance postoperative peripheral nerve regeneration in rats. Based on the promising results in vivo experiments, further studies are needed to demonstrate potential clinical benefits.

Exosomes from Hair Follicle Epidermal Neural Crest Stem Cells Promote Acellular Nerve Allografts to Bridge Rat Facial Nerve Defects

Previous studies showed that acellular nerve allografts (ANAs) have been successfully utilized in repairing peripheral nerve defects, and exosomes produced by stem cells are useful in supporting axon regrowth after peripheral nerve injury. In this study, exosomes from hair follicle epidermal neural crest stem cells (EPI-NCSCs-Exos) combined with ANAs were used to bridge facial nerve defects. EPI-NCSCs-Exos were isolated by ultracentrifuge, and were identified. After coculture, EPI-NCSCs-Exos were internalized into dorsal root ganglions (DRGs) and schwann cells (SCs) in vitro, respectively. EPI-NCSCs-Exos elongate the length of axons and dendrites of DRGs, and accelerated the proliferation and migration of SCs, and increased neurotrophic factor expression of SCs as well. The next step was to assign 24 Sprague Dawley male rats randomly and equally into three groups: the autograft group, the ANA group, and the ANA + EPI-NCSCs-Exos group. Each rat manufactured a 5-mm gap of facial nerve defect and immediately bridged by the corresponding transplants, respectively. After surgery, behavioral changes and electrophysiological testing of each rat were observed and assessed. At 90 days postoperatively, the retrogradely fluorescent tracer-labeled neurons were successfully observed on the injured side in the three groups. Morphological changes of facial nerve regeneration were evaluated by transmission electron microscopy and semithin toluidine blue staining. The results showed that nerve fiber density, nerve fiber diameter, and myelin sheath thickness in the ANA group were significantly worse than those in the other two groups (P < 0.05). No significant difference in nerve fiber density and myelin sheath thickness was observed between the autograft group and the ANA + EPI-NCSCs-Exos group (P = 0.14; P = 0.23). Our data indicated that EPI-NCSCs-Exos facilitate ANAs to bridge facial nerve defects and have the potential to replace autograft therapy in clinic.

Neural grafts containing exosomes derived from Schwann cell-like cells promote peripheral nerve regeneration in rats

Background

Schwann cell-like cells (SCLCs), differentiated from mesenchymal stem cells, have shown promising outcomes in the treatment of peripheral nerve injuries in preclinical studies. However, certain clinical obstacles limit their application. Hence, the primary aim of this study was to investigate the role of exosomes derived from SCLCs (SCLCs-exo) in peripheral nerve regeneration.

Methods

SCLCs were differentiated from human amniotic mesenchymal stem cells (hAMSCs) in vitro and validated by immunofluorescence, real-time quantitative PCR and western blot analysis. Exosomes derived from hAMSCs (hAMSCs-exo) and SCLCs were isolated by ultracentrifugation and validated by nanoparticle tracking analysis, WB analysis and electron microscopy. A prefabricated nerve graft was used to deliver hAMSCs-exo or SCLCs-exo in an injured sciatic nerve rat model. The effects of hAMSCs-exo or SCLCs-exo on rat peripheral nerve injury (PNI) regeneration were determined based on the recovery of neurological function and histomorphometric variation. The effects of hAMSCs-exo or SCLCs-exo on Schwann cells were also determined via cell proliferation and migration assessment.

Results

SCLCs significantly expressed the Schwann cell markers glial fibrillary acidic protein and S100. Compared to hAMSCs-exo, SCLCs-exo significantly enhanced motor function recovery, attenuated gastrocnemius muscle atrophy and facilitated axonal regrowth, myelin formation and angiogenesis in the rat model. Furthermore, hAMSCs-exo and SCLCs-exo were efficiently absorbed by Schwann cells. However, compared to hAMSCs-exo, SCLCs-exo significantly promoted the proliferation and migration of Schwann cells. SCLCs-exo also significantly upregulated the expression of a glial cell-derived neurotrophic factor, myelin positive regulators (SRY-box transcription factor 10, early growth response protein 2 and organic cation/carnitine transporter 6) and myelin proteins (myelin basic protein and myelin protein zero) in Schwann cells.

Conclusions

These findings suggest that SCLCs-exo can more efficiently promote PNI regeneration than hAMSCs-exo and are a potentially novel therapeutic approach for treating PNI.

Exosomes derived from miR-338-3p-modified adipose stem cells inhibited inflammation injury of chondrocytes via targeting RUNX2 in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a chronic degenerative disease that is one of the main causes of disability in middle-aged and elderly people. Adipose stem cell (ASC)-derived exosomes (ASC-Exo) could repair cartilage damage and treat OA. MiRNA-338-3p expression was confirmed to play a role in inhibiting proinflammatory cytokines. Herein, we aimed to explore the mechanism by which exosomes derived from miR-338-3p overexpressing ASCs protects chondrocytes from interleukin (IL)-1β-induced chondrocyte change.

METHODS

Exosomes were extracted from ASCs transfected with miR-338-3p or its antisense inhibitor. The ASC-Exos (miR-338-3p silencing/overexpression) were incubated with IL-1β-induced ATDC5 cells, followed by evaluation of the chondrocyte proliferation, degradation, and inflammation injury.

RESULTS

In vitro results revealed that ASC-Exos inhibited the expression of prostaglandin E2 (PGE2), IL-6, IL-1β, and TNF-α, as well as promoted the proliferation of ATDC5 cells. Moreover, ASC-Exos inhibited inflammation injury and degradation of ATDC5 cells by transferring miR-338-3p. Luciferase reporter assays showed that RUNX2 was a target gene of miR-338-3p. Additionally, RUNX2 overexpression in ATDC5 cells reversed the protective effect of miR-338-3p on chondrocytes. Taken together, this study demonstrated that exosomes secreted from miR-338-3p-modified ASCs were effective in the repair of IL-1β-induced chondrocyte change by inhibiting RUNX2 expression.

CONCLUSIONS

Our result provided valuable data for understanding the mechanism of ASC-Exos in OA treatment.

Evaluation and Comparison of the Effects of Mature Silkworm (Bombyx mori) and Silkworm Pupae Extracts on Schwann Cell Proliferation and Axon Growth: An In Vitro Study

Background

Silkworm products were first used by physicians more than 8500 years ago, in the early Neolithic period. In Persian medicine, silkworm extract has several uses for treating and preventing neurological, cardiac, and liver diseases. Mature silkworms (Bombyx mori) and their pupae contain a variety of growth factors and proteins that can be used in many repair processes, including nerve regeneration.

Objectives

The study aimed to evaluate the effects of mature silkworm (Bombyx mori), and silkworm pupae extract on Schwann cell proliferation and axon growth.

Methods

Silkworm (Bombyx mori) and silkworm pupae extracts were prepared. Then, the concentration and type of amino acids and proteins in the extracts were evaluated by Bradford assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and liquid chromatograph-mass spectrometer (LC-MS/MS). Also, the regenerative potential of extracts for improving Schwann cell proliferation and axon growth was examined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay, electron microscopy, and NeuroFilament-200 (NF-200) immunostaining.

Results

According to the results of the Bradford test, the total protein content of pupae extract was almost twice that of mature worm extract. Also, SDS-PAGE analysis revealed numerous proteins and growth factors, such as bombyrin and laminin, in extracts that are involved in the repair of the nervous system. In accordance with Bradford's results, the evaluation of extracts using LC-MS/MS revealed that the number of amino acids in pupae extract was higher than in mature silkworm extract. It was found that the proliferation of Schwann cells at a concentration of 0.25 mg/mL in both extracts was higher than the concentrations of 0.01 and 0.05 mg/mL. When using both extracts on dorsal root ganglion (DRGs), an increase in length and number was observed in axons.

Conclusions

The findings of this study demonstrated that extracts obtained from silkworms, especially pupae, can play an effective role in Schwann cell proliferation and axonal growth, which can be strong evidence for nerve regeneration, and, consequently, repairing peripheral nerve damage.

Thermosensitive hydrogel carrying extracellular vesicles from adipose-derived stem cells promotes peripheral nerve regeneration after microsurgical repair

Peripheral nerve injuries are commonly occurring traumas of the extremities; functional recovery is hindered by slow nerve regeneration (<1 mm/day) following microsurgical repair and subsequent muscle atrophy. Functional recovery after peripheral nerve repair is highly dependent on local Schwann cell activity and axon regeneration speed. Herein, to promote nerve regeneration, paracrine signals of adipose-derived stem cells were applied in the form of extracellular vesicles (EVs) loaded in a thermosensitive hydrogel (PALDE) that could solidify rapidly and sustain high EV concentration around a repaired nerve during surgery. Cell experiments revealed that PALDE hydrogel markedly promotes Schwann-cell migration and proliferation and axon outgrowth. In a rat sciatic nerve repair model, the PALDE hydrogel increased repaired-nerve conduction efficacy; contraction force of leg muscles innervated by the repaired nerve also recovered. Electromicroscopic examination of downstream nerves indicated that fascicle diameter and myeline thickness in the PALDE group (1.91 ± 0.61 and 1.06 ± 0.40 μm, respectively) were significantly higher than those in PALD and control groups. Thus, this EV-loaded thermosensitive hydrogel is a potential cell-free therapeutic modality to improve peripheral-nerve regeneration, offering sustained and focused EV release around the nerve-injury site to overcome rapid clearance and maintain EV bioactivity in vivo.

Exosomes from Adipose Stem Cells Promote Diabetic Wound Healing through the eHSP90/LRP1/AKT Axis

Oxidative damage is a critical cause of diabetic wounds. Exosomes from various stem cells could promote wound repair. Here, we investigated the potential mechanism by which exosomes from adipose-derived stem cells (ADSC-EXOs) promote diabetic wound healing through the modulation of oxidative stress. We found that ADSC-EXOs could promote proliferation, migration, and angiogenesis in keratinocytes, fibroblasts, and endothelial cells. Furthermore, ADSC-EXOs reduced the reactive oxygen species (ROS) levels in these cells and protected them against hypoxic and oxidative stress damage. Finally, the local injection of ADSC-EXOs at wound sites significantly increased collagen deposition and neovascularization while reducing ROS levels and cell death; thus, it led to accelerated diabetic wound closure. The mechanism underlying ADSC-EXO functions involved heat-shock protein 90 (HSP90) expressed on the cell surface; these functions could be inhibited by an anti-HSP90 antibody. Exosomal HSP90 could bind to the low-density lipoprotein receptor-related protein 1 (LRP1) receptor on the recipient cell membrane, leading to activation of the downstream AKT signaling pathway. Knockdown of LRP1 and inhibition of the AKT signaling pathway by LY294002 in fibroblasts was sufficient to impair the beneficial effect of ADSC-EXOs. In summary, ADSC-EXOs significantly accelerated diabetic wound closure through an exosomal HSP90/LRP1/AKT signaling pathway.

Adipose-Derived Stem Cell Exosomes and Related microRNAs in Atherosclerotic Cardiovascular Disease

Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of death from noncommunicable diseases worldwide. The pathological development of ASCVD begins with atherosclerosis, followed by the narrowing and occlusion of the vascular lumen and, subsequently, ischemic necrosis in coronary arteries. Preventing atherosclerosis development and delaying ischemia progression may be effective ways of pre-diagnosing and treating ASCVD. Studies have demonstrated that exosomes from adipose-derived stem cells play an increasingly important role in basic research on cardiovascular diseases in terms of the impact of macrophage polarization and the endothelial, anti-apoptosis, and angiogenesis effects. The related microRNAs play a significant role in ASCVD. This study was novel in reviewing the role of exosomes from adipose-derived stem cells and related microRNAs in ASCVD. Therapeutic potentials of adipose-derived stem cell exosomes in terms of their impact on macrophage polarization, endothelial effect, anti-apoptosis intervention, and angiogenesis.

Exosomes Derived from Adipose Mesenchymal Stem Cells Carrying miRNA-22-3p Promote Schwann Cells Proliferation and Migration through Downregulation of PTEN

Peripheral nerve injury (PNI) is often resulting from trauma, which leads to severe and permanently disability. Schwann cells are critical for facilitating the regeneration process after PNI. Adipose-derived mesenchymal stem cells (ADSCs) exosomes have been used as a novel treatment for peripheral nerve injury. However, the underlying mechanism remains unclear. In this study, we isolated ADSCs and extracted exosomes, which were verified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blot (WB). Cocultured with Dorsal Root Ganglion (DRG) and Schwann cells (SCs) to evaluate the effect of exosomes on the growth of DRG axons by immunofluorescence, and the proliferation and migration of SCs by CCK8 and Transwell assays, respectively. Through exosomal miRNA sequencing and bioinformatic analysis, the related miRNAs and target gene were predicted and identified by dual luciferase assay. Related miRNAs were overexpressed and inhibited, respectively, to clarify their effects; the downstream pathway through the target gene was determined by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) and WB. Results found that ADSC-exosomes could promote the proliferation and migration of SCs and the growth of DRG axons, respectively. Exosomal miRNA-22-3p from ADSCs directly inhibited the expression of Phosphatase and Tensin Homolog deleted on Chromosome 10 (PTEN), activated phosphorylation of the AKT/mTOR axis, and enhanced SCs proliferation and migration. In conclusion, our findings suggest that ADSC-exosomes could promote SCs function through exosomal miRNA-22-3p, which could be used as a therapeutic target for peripheral nerve injury.

Tailored Extracellular Vesicles: Novel Tool for Tissue Regeneration

Extracellular vesicles (EVs) play an essential part in multiple pathophysiological processes including tissue injury and regeneration because of their inherent characteristics of small size, low immunogenicity and toxicity, and capability of carrying a variety of bioactive molecules and mediating intercellular communication. Nevertheless, accumulating studies have shown that the application of EVs faces many challenges such as insufficient therapeutic efficacy, a lack of targeting capability, low yield, and rapid clearance from the body. It is known that EVs can be engineered, modified, and designed to encapsulate therapeutic cargos like proteins, peptides, nucleic acids, and drugs to improve their therapeutic efficacy. Targeted peptides, antibodies, aptamers, magnetic nanoparticles, and proteins are introduced to modify various cell-derived EVs for increasing targeting ability. In addition, extracellular vesicle mimetics (EMs) and self-assembly EV-mimicking nanocomplex are applied to improve production and simplify EV purification process. The combination of EVs with biomaterials like hydrogel, and scaffolds dressing endows EVs with long-term therapeutic efficacy and synergistically enhanced regenerative outcome. Thus, we will summarize recent developments of EV modification strategies for more extraordinary regenerative effect in various tissue injury repair. Subsequently, opportunities and challenges of promoting the clinical application of engineered EVs will be discussed.

Role of exosomes in the pathogenesis, diagnosis, and treatment of central nervous system diseases

Central nervous system (CNS) diseases, such as multiple sclerosis, Alzheimer's disease (AD), and Parkinson’s disease (PD), affect millions of people around the world. Great efforts were put in disease related research, but few breakthroughs have been made in the diagnostic and therapeutic approaches. Exosomes are cell-derived extracellular vesicles containing diverse biologically active molecules secreted by their cell of origin. These contents, including nucleic acids, proteins, lipids, amino acids, and metabolites, can be transferred between different cells, tissues, or organs, regulating various intercellular cross-organ communications and normal and pathogenic processes. Considering that cellular environment and cell state strongly impact the content and uptake efficiency of exosomes, their detection in biological fluids and content composition analysis potentially offer a multicomponent diagnostic readout of several human diseases. Recently, studies have found that aberrant secretion and content of exosomes are closely related to the pathogenesis of CNS diseases. Besides, loading natural cargoes, exosomes can deliver drugs cross the blood brain barrier, making them emerging candidates of biomarkers and therapeutics for CNS diseases. In this review, we summarize and discuss the advanced research progress of exosomes in the pathological processes of several CNS diseases in regarding with neuroinflammation, CNS repair, and pathological protein aggregation. Moreover, we propose the therapeutic strategies of applying exosomes to the diagnosis, early detection, and treatment of CNS diseases.

Research Progress on Transorgan Regulation of the Cardiovascular and Motor System through Cardiogenic Exosomes

The heart is the core organ of the circulatory system. Through the blood circulation system, it has close contact with all tissues and cells in the body. An exosome is an extracellular vesicle enclosed by a phospholipid bilayer. A variety of heart tissue cells can secrete and release exosomes, which transfer RNAs, lipids, proteins, and other biomolecules to adjacent or remote cells, mediate intercellular communication, and regulate the physiological and pathological activities of target cells. Cardiogenic exosomes play an important role in regulating almost all pathological and physiological processes of the heart. In addition, they can also reach distant tissues and organs through the peripheral circulation, exerting profound influence on their functional status. In this paper, the composition and function of cardiogenic exosomes, the factors affecting cardiogenic exosomes and their roles in cardiovascular physiology and pathophysiology are discussed, and the close relationship between cardiovascular system and motor system is innovatively explored from the perspective of exosomes. This study provides a reference for the development and application of exosomes in regenerative medicine and sports health, and also provides a new idea for revealing the close relationship between the heart and other organ systems.

Adipose stem cells-released extracellular vesicles as a next-generation cargo delivery vehicles: a survey of minimal information implementation, mass production and functional modification

OBJECTIVES

To investigate current situation of minimal information implementation highlighted by minimal information for studies of extracellular vesicles 2018 (MISEV2018) guidelines, and explore technological advances towards mass production and functional modification in aesthetic, plastic and reconstructive surgery.

METHODS

Original articles on extracellular vesicles (EVs) of adipose stem cells (ASCs) were identified. Statistics upon minimal information for EVs research, such as species, cell types, culture conditions, conditioned media harvesting parameters, EVs isolation/storage/identification/quantification, functional uptake and working concentration, were analyzed.

RESULTS

The items of cell culture conditions such as passage number, seeding density, conditioned media harvesting time, functional uptake and working concentration were poorly documented, with a reporting percentage of 47.13%, 54.02%, 29.89%, 62.07% and 36.21%, respectively. However, there were some studies not reporting information of ASCs origin, culture medium, serum, EVs isolation methods, quantification and identification of EVs, accounting for 3.45%, 10.34%, 6.90%, 3.45%, 18.39% and 4.02%, respectively. Serum deprivation and trophic factors stimuli were attempted for EVs mass production. Several technological advances towards functional modification included hypoxia pre-condition, engineering EVs and controlled release. Presently, ASCs EVs have been applied in multiple fields, including diabetic/non-diabetic wound healing, angiogenesis, inflammation modulation, fat grafting, hair regeneration, antiaging, and healing and regeneration of cartilage/bone/peripheral nerve/tendon.

CONCLUSION

Our results highlight normative reporting of ASCs EVs in functional studies to increase reliability and reproducibility of scientific publications. The advances towards mass production and functional modification of ASCs EVs are also recommended to enhance therapeutic effects.

The Therapeutic Potential of Exosomes in Soft Tissue Repair and Regeneration

Soft tissue defects are common following trauma and tumor extirpation. These injuries can result in poor functional recovery and lead to a diminished quality of life. The healing of skin and muscle is a complex process that, at present, leads to incomplete recovery and scarring. Regenerative medicine may offer the opportunity to improve the healing process and functional outcomes. Barriers to regenerative strategies have included cost, regulatory hurdles, and the need for cell-based therapies. In recent years, exosomes, or extracellular vesicles, have gained tremendous attention in the field of soft tissue repair and regeneration. These nanosized extracellular particles (30-140 nm) can break the cellular boundaries, as well as facilitate intracellular signal delivery in various regenerative physiologic and pathologic processes. Existing studies have established the potential of exosomes in regenerating tendons, skeletal muscles, and peripheral nerves through different mechanisms, including promoting myogenesis, increasing tenocyte differentiation and enhancing neurite outgrowth, and the proliferation of Schwann cells. These exosomes can be stored for immediate use in the operating room, and can be produced cost efficiently. In this article, we critically review the current advances of exosomes in soft tissue (tendons, skeletal muscles, and peripheral nerves) healing. Additionally, new directions for clinical applications in the future will be discussed.

Melatonin Engineered Adipose-Derived Biomimetic Nanovesicles Regulate Mitochondrial Functions and Promote Myocardial Repair in Myocardial Infarction

Myocardial infarction (MI), one type of ischemic heart disease, is a major cause of disability and mortality worldwide. Currently, extracellular vesicles (EVs) derived from adipose-derived stem cells (ADSC) have been proven to be a potentially promising therapeutic treatment for MI. However, the inconvenience of isolation, the low productivity, and the high cost of EVs greatly limits their application in clinic. In this study, we constructed novel biomimetic ADSC-derived nanovesicles (ADSC NVs) to achieve cell-free therapy for MI. Here, we firstly developed a novel Mel@NVs delivery system consisting of engineered ADSC NVs with melatonin (Mel). Then, the characterization and properties of Mel@NVs were performed. The effect of Mel@NVs on cellular oxidative stress and myocardial infarction repair was conducted. The results showed that Mel@NVs treatment under ischemia mimic condition reduced cell apoptosis from 42.59 ± 2.69% to 13.88 ± 1.77%. Moreover, this novel engineered Mel@NVs could ameliorate excessive ROS generation, promote microvessel formation, and attenuate cardiac fibrosis, which further alleviates mitochondrial dysfunction and finally enhance myocardial repair. Hence, the engineered NVs show a potential strategy for MI therapy.

Tissue-engineered in vitro modeling of the impact of Schwann cells in amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disease affecting upper and lower motor neurons (MN). To investigate whether Schwann cells could be involved in the disease pathogenesis, we developed a tissue-engineered 3D in vitro model that combined MNs cocultured with astrocytes and microglia seeded on top of a collagen sponge populated with epineurium fibroblasts to enable 3D axonal migration. C2C12 myoblasts were seeded underneath the sponge in presence or absence of Schwann cells. To reproduce an ALS cellular microenvironment, MNs, astrocytes and microglia were extracted from SOD1^G93A mice recapitulating many aspects of the human disease. This 3D ALS in vitro model was compared with a 3D control made of cells isolated from SOD1^WT mice. We showed that normal Schwann cells strongly enhanced MN axonal migration in the 3D control model but had no effect in the ALS model. However, ALS-derived Schwann cells isolated from SOD1^G93A mice failed to significantly improve axonal migration in both models. These results suggest that a cell therapy using healthy Schwann cells may not be effective in promoting axonal regeneration in ALS. In addition, this 3D ALS model could be used to study the impact of other cell types on ALS by various combinations of normal and diseased cells. This article is protected by copyright. All rights reserved.

Fat obtained from plastic surgery procedures—stem cells derived from adipose tissue and their potential in technological innovation: a narrative literature review and perspective on dissociative methods

Background

Throughout its illustrious history, plastic surgery has searched for novel regenerative therapies and procedures. Recently, interest has emerged in using adipose tissue-derived stem cells (ASCs) in an ethical, easy, and reproducible manner. ASCs are generally not administered alone but as a constituent of the stromal vascular fraction (SVF) in clinical practice. Herein, we searched for innovative fat collection and ASC isolation technologies and applications and evaluated each study’s relevance to plastic surgery.

Methods

A narrative literature review was carried out using the MEDLINE/PubMed databases. Studies published from January 1993 to August 2020 and written in English, Portuguese, or Spanish were considered.

Results

The selection process yielded 33 articles for subsequent review, involving exploratory, selective, and interpretive reading, material choice, and text analysis. Twenty-three articles employed enzymatic dissociation methods to isolate ASCs, and 25 employed liposuction as the plastic surgery technique. Moreover, articles describing new devices (n = 2), techniques (n = 4), computational models (n = 1), tissue scaffolds (n = 21), and therapies and/or treatments (n = 5) were identified.

Conclusions

Given the importance of fat tissue for plastic surgery purposes, innovative ASC isolation and liposuction technologies could change how the surgeon conducts surgeries and improve surgical outcomes. Furthermore, many articles investigating tissue scaffolds demonstrate the importance of this area of research and development in plastic surgery and regenerative medicine. Continued efforts in the identified research areas will eventually bring in vivo human plastic surgery applications and regenerative medicine into the operating room. Level of evidence: Not gradable.

Tumor necrosis factor receptor-1 is selectively sequestered into Schwann cell extracellular vesicles where it functions as a TNFα decoy

Schwann cells (SCs) are known to produce extracellular vesicles (EV) that participate in cell-cell communication by transferring cargo to target cells, including mRNAs, microRNAs, and biologically active proteins. Herein, we report a novel mechanism whereby SC EVs may regulate PNS physiology, especially in injury, by controlling the activity of TNFα. SCs actively sequester tumor necrosis factor receptor-1 (TNFR1) into EVs at high density, accounting for about 2% of the total protein in SC EVs (~1000 copies TNFR1/EV). Although TNFR2 was robustly expressed by SCs in culture, TNFR2 was excluded from SC EVs. SC EV TNFR1 bound TNFα, decreasing the concentration of free TNFα available to bind to cells and thus served as a TNFα decoy. SC EV TNFR1 significantly inhibited TNFα-induced p38 MAPK phosphorylation in cultured SCs. When TNFR1 was proteolytically removed from SC EVs using tumor necrosis factor-α converting enzyme (TACE) or neutralized with antibody, the ability of TNFα to activate p38 MAPK in the presence of these EVs was restored. As further evidence of its decoy activity, SC EV TNFR1 modified TNFα activities in vitro including: (1) regulation of expression of other cytokines; (2) effects on SC morphology; and (3) effects on SC viability. SC EVs also modified the effects of TNFα on sciatic nerve morphology and neuropathic pain-related behavior in vivo. By sequestering TNFR1 in EVs, SCs may buffer against the potentially toxic effects of TNFα. SC EVs provide a novel mechanism for the spatial and temporal regulation of neuro-inflammation.