Intra-Articular Injections of Mesenchymal Stem Cell Exosomes and Hyaluronic Acid Improve Structural and Mechanical Properties of Repaired Cartilage in a Rabbit Model

Protective effects of mesenchymal stem cells-derived extracellular vesicles against ischemia-reperfusion injury of hearts donated after circulatory death: Preliminary study in a pig model

INTRODUCTION

Insufficient supply of cardiac grafts represents a severe obstacle in heart transplantation. Donation after Circulatory Death (DCD), in addition to conventional donation after brain death, is one promising option to overcome the organ shortage. However, DCD organs undergo an inevitable more extended period of warm unprotected ischemia between circulatory arrest and graft procurement. Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have shown remarkable protective effects against ischemia-reperfusion injury. Thus, we aimed to enhance grafts preservation from DCD donors, through treatment with MSC-EVs.

METHODS

Female pigs were euthanized by barbiturate overdose and after 20 min of a flat EKG, the chest was opened, the heart harvested and subsequently connected to an extracorporeal perfusion machine. MSC-EVs, isolated by ion exchange chromatography, were added to the perfusion solution (1×1011 particles) and the heart was perfused for 2 h. Then, heart tissue biopsies were taken to assess histological changes, mitochondrial morphology, antioxidant enzyme activity and inflammation mediators' expression. Biochemical parameters of myocardial viability were assessed in the perfusate.

RESULTS

The treatment with MSC-EVs significantly prevented mitochondria swelling, mitochondrial cristae loss and oxidative stress in cardiac tissue. The protective effect of MSC-EVs was confirmed by the delayed increase of the cardiac-specific enzymes CK and TnC in the perfusate and the reduction of caspase-3+ cells in tissue sections.

CONCLUSION

MSC-EVs improve graft quality by preserving the mitochondrial ultrastructure protecting the myocardium against oxidative stress, reducing apoptosis of cardiac cells and preventing the increase of pro-inflammatory cytokines.

The Therapeutic Effects of Blueberry-Treated Stem Cell-Derived Extracellular Vesicles in Ischemic Stroke

An ischemic stroke, one of the leading causes of morbidity and mortality, is caused by ischemia and hemorrhage resulting in impeded blood supply to the brain. According to many studies, blueberries have been shown to have a therapeutic effect in a variety of diseases. Therefore, in this study, we investigated whether blueberry-treated mesenchymal stem cell (MSC)-derived extracellular vesicles (B-EVs) have therapeutic effects in in vitro and in vivo stroke models. We isolated the extracellular vesicles using cryo-TEM and characterized the particles and concentrations using NTA. MSC-derived extracellular vesicles (A-EVs) and B-EVs were round with a lipid bilayer structure and a diameter of ~150 nm. In addition, A-EVs and B-EVs were shown to affect angiogenesis, cell cycle, differentiation, DNA repair, inflammation, and neurogenesis following KEGG pathway and GO analyses. We investigated the protective effects of A-EVs and B-EVs against neuronal cell death in oxygen-glucose deprivation (OGD) cells and a middle cerebral artery occlusion (MCAo) animal model. The results showed that the cell viability was increased with EV treatment in HT22 cells. In the animal, the size of the cerebral infarction was decreased, and the behavioral assessment was improved with EV injections. The levels of NeuN and neurofilament heavy chain (NFH)-positive cells were also increased with EV treatment yet decreased in the MCAo group. In addition, the number of apoptotic cells was decreased with EV treatment compared with ischemic animals following TUNEL and Bax/Bcl-2 staining. These data suggested that EVs, especially B-EVs, had a therapeutic effect and could reduce apoptotic cell death after ischemic injury.

Mesenchymal stem cells for cartilage regeneration: Insights into molecular mechanism and therapeutic strategies

The use of mesenchymal stem cells (MSCs) in cartilage regeneration has gained significant attention in regenerative medicine. This paper reviews the molecular mechanisms underlying MSC-based cartilage regeneration and explores various therapeutic strategies to enhance the efficacy of MSCs in this context. MSCs exhibit multipotent capabilities and can differentiate into various cell lineages under specific microenvironmental cues. Chondrogenic differentiation, a complex process involving signaling pathways, transcription factors, and growth factors, plays a pivotal role in the successful regeneration of cartilage tissue. The chondrogenic differentiation of MSCs is tightly regulated by growth factors and signaling pathways such as TGF-β, BMP, Wnt/β-catenin, RhoA/ROCK, NOTCH, and IHH (Indian hedgehog). Understanding the intricate balance between these pathways is crucial for directing lineage-specific differentiation and preventing undesirable chondrocyte hypertrophy. Additionally, paracrine effects of MSCs, mediated by the secretion of bioactive factors, contribute significantly to immunomodulation, recruitment of endogenous stem cells, and maintenance of chondrocyte phenotype. Pre-treatment strategies utilized to potentiate MSCs, such as hypoxic conditions, low-intensity ultrasound, kartogenin treatment, and gene editing, are also discussed for their potential to enhance MSC survival, differentiation, and paracrine effects. In conclusion, this paper provides a comprehensive overview of the molecular mechanisms involved in MSC-based cartilage regeneration and outlines promising therapeutic strategies. The insights presented contribute to the ongoing efforts in optimizing MSC-based therapies for effective cartilage repair.

Functional and Molecular Analysis of Human Osteoarthritic Chondrocytes Treated with Bone Marrow-Derived MSC-EVs

Osteoarthritis (OA) is a degenerative joint disease, causing impaired mobility. There are currently no effective therapies other than palliative treatment. Mesenchymal stromal cells (MSCs) and their secreted extracellular vesicles (MSC-EVs) have shown promise in attenuating OA progression, promoting chondral regeneration, and modulating joint inflammation. However, the precise molecular mechanism of action driving their beneficial effects has not been fully elucidated. In this study, we analyzed MSC-EV-treated human OA chondrocytes (OACs) to assess viability, proliferation, migration, cytokine and catabolic protein expression, and microRNA and mRNA profiles. We observed that MSC-EV-treated OACs displayed increased metabolic activity, proliferation, and migration compared to the controls. They produced decreased proinflammatory (Il-8 and IFN-γ) and increased anti-inflammatory (IL-13) cytokines, and lower levels of MMP13 protein coupled with reduced expression of MMP13 mRNA, as well as negative microRNA regulators of chondrogenesis (miR-145-5p and miR-21-5p). In 3D models, MSC-EV-treated OACs exhibited enhanced chondrogenesis-promoting features (elevated sGAG, ACAN, and aggrecan). MSC-EV treatment also reversed the pathological impact of IL-1β on chondrogenic gene expression and extracellular matrix component (ECM) production. Finally, MSC-EV-treated OACs demonstrated the enhanced expression of genes associated with cartilage function, collagen biosynthesis, and ECM organization and exhibited a signature of 24 differentially expressed microRNAs, associated with chondrogenesis-associated pathways and ECM interactions. In conclusion, our data provide new insights on the potential mechanism of action of MSC-EVs as a treatment option for early-stage OA, including transcriptomic analysis of MSC-EV-treated OA, which may pave the way for more targeted novel therapeutics.

Exosomes Derived from Bone Marrow Mesenchymal Stem Cells Alleviate Rheumatoid Arthritis Symptoms via Shuttling Proteins

Our prior investigations have evidenced that bone marrow mesenchymal stem cell (BMSC) therapy can significantly improve the outcomes of rheumatoid arthritis (RA). This study aims to conduct a comprehensive analysis of the proteomics between BMSCs and BMSCs-Exos, and to further elucidate the potential therapeutic effect of BMSCs-Exos on RA, so as to establish a theoretical framework for the prevention and therapy of BMSCs-Exos on RA. The 4D label-free LC-MS/MS technique was used for comparative proteomic analysis of BMSCs and BMSCs-Exos. Collagen-induced arthritis (CIA) rat model was used to investigate the therapeutic effect of BMSCs-Exos on RA. Our results showed that some homology and differences were observed between BMSCs and BMSCs-Exos proteins, among which proteins highly enriched in BMSCs-Exos were related to extracellular matrix and extracellular adhesion. BMSCs-Exos can be taken up by chondrocytes, promoting cell proliferation and migration. In vivo results revealed that BMSCs-Exos significantly improved the clinical symptoms of RA, showing a certain repair effect on the injury of articular cartilage. In short, our study revealed, for the first time, that BMSCs-Exos possess remarkable efficacy in alleviating RA symptoms, probably through shuttling proteins related to cell adhesion and tissue repair ability in CIA rats, suggesting that BMSCs-Exos carrying expressed proteins may become a useful biomaterial for RA treatment.

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.

Polyethylene glycol precipitation is an efficient method to obtain extracellular vesicle-depleted fetal bovine serum

Mesenchymal stromal/stem cell derived-extracellular vesicles (MSC-EVs) have gained interest as drug delivery nanoparticles, having immunoregulatory and potentiating tissue repair property. To maintain growth of MSCs and obtain pure MSC-derived EVs, the culture media should contain fetal bovine serum (FBS) devoid of EVs, as the presence of FBS EVs confounds the properties of MSC-EVs. Therefore, we tested three methods: 18h ultracentrifugation (UC) and ultrafiltration (UF), which are common FBS EV depletion methods in current MSC-EV research, and polyethylene glycol (PEG) precipitation to obtain three EV depleted FBS (EVdFBS) batches, and compared them to FBS and commercial (Com) EVdFBS on human adipose stem cell (hADSC) growth, differentiation, enrichment of EVs in hADSC supernatant and their biological function on collagen metabolism. Our comparative study showed UC and UF vary in terms of depletion efficiency and do not completely deplete EVs and affects the growth-promoting quality of FBS. Specifically, FBS EV depletion was comparable between PEG (95.6%) and UF (96.6%) but less by UC (82%), as compared to FBS. FBS protein loss was markedly different among PEG (47%), UF (87%), and UC (51%), implying the ratio of EV depletion over protein loss was PEG (2.03), UF (1.11), and UC (1.61). A significant decrease of TGFβ/Smad signaling, involving in MSC growth and physiology, was observed by UF. After 96 hours of exposure to 5% FBS or 5% four different EVdFBS cell growth media, the osteogenesis ability of hADSCs was not impaired but slightly lower mRNA expression level of Col2a observed in EVdFBS media during chondrogenesis. In consistent with low confluency of hADSCs observed by optical microscope, cell proliferation in response to 5% UF EVdFBS media was inhibited significantly. Importantly, more and purer ADSCs EVs were obtained from ADSCs cultured in 5% PEG EVdFBS media, and they retained bioactive as they upregulated the expression of Col1a1, TIMP1 of human knee synovial fibroblast. Taken together, this study showed that PEG precipitation is the most efficient method to obtain EV depleted FBS for growth of MSCs, and to obtain MSC EVs with minimal FBS EV contamination.

Exosomes loaded with chondrogenic stimuli agents combined with 3D bioprinting hydrogel in the treatment of osteoarthritis and cartilage degeneration

Osteoarthritis (OA) is a challenging joint inflammatory disease that often leads to disability. Immunoregulatory Exosomes (Exos) have shown promise in OA and cartilage degeneration treatment. Engineering Exos to deliver therapeutic agents like Kartogenin (KGN) has displayed potential for restoring cartilage regeneration. However, challenges include the uneven distribution of Exos at the injury site and the release of Exos cargo out of chondrocytes. Hydrogel-loaded uMSC-Exo has demonstrated significant therapeutic effects in wound healing and tissue regeneration. Recently, a new version of three-dimensional (3D) bioprinting of hydrogel significantly restored cartilage regeneration in OA joints. Combining immune regulatory Exos with 3D bioprinting hydrogel (3D-BPH-Exos) holds the potential for immunomodulating cartilage tissue and treatment of OA. It can reduce intracellular inflammasome formation and the release of inflammatory agents like IL-1β, TNF-α, and INF-γ, while also preventing chondrocyte apoptosis by restoring mitochondrial functions and enhancing chondrogenesis in synovial MSCs, osteoprogenitor cells, and osteoclasts. Loading Exos with chondrogenic stimuli agents in the 3D-BPH-Exos approach may offer a faster and safer strategy for cartilage repair while better inhibiting joint inflammation than high doses of anti-inflammatory drugs and cell-based therapies. This review provides a comprehensive overview of hydrogel bioprinting and exosome-based therapy in OA. It emphasizes the potential of 3D-BPH-Exos loaded with chondrogenic stimuli agents for OA treatment, serving as a basis for further research.

Effects of hydroxyapatite-coated porous titanium scaffolds functionalized by exosomes on the regeneration and repair of irregular bone

As a traditional bone implant material, titanium (Ti) and its alloys have the disadvantages of lack of biological activity and susceptibility to stress shielding effect. Adipose stem cells (ADSCs) and exosomes were combined with the scaffold material in the current work to effectively create a hydroxyapatite (HA) coated porous titanium alloy scaffold that can load ADSCs and release exosomes over time. The composite made up for the drawbacks of traditional titanium alloy materials with higher mechanical characteristics and a quicker rate of osseointegration. Exosomes (Exos) are capable of promoting the development of ADSCs in porous titanium alloy scaffolds with HA coating, based on experimental findings from in vitro and in vivo research. Additionally, compared to pure Ti implants, the HA scaffolds loaded with adipose stem cell exosomes demonstrated improved bone regeneration capability and bone integration ability. It offers a theoretical foundation for the combined use of stem cell treatment and bone tissue engineering, as well as a design concept for the creation and use of novel clinical bone defect repair materials.

Exosome-Laden Scaffolds for Treatment of Post-Traumatic Cartilage Injury and Osteoarthritis of the Knee: A Systematic Review

Mesenchymal stem cell (MSC)-based exosomes have garnered attention as a viable therapeutic for post-traumatic cartilage injury and osteoarthritis of the knee; however, efforts for application have been limited due to issues with variable dosing and rapid clearance in vivo. Scaffolds laden with MSC-based exosomes have recently been investigated as a solution to these issues. Here, we review in vivo studies and highlight key strengths and potential clinical uses of exosome-scaffold therapeutics for treatment of post-traumatic cartilage injury and osteoarthritis. In vivo animal studies were gathered using keywords related to the topic, revealing 466 studies after removal of duplicate papers. Inclusion and exclusion criteria were applied for abstract screening and full-text review. Thirteen relevant studies were identified for analysis and extraction. Three predominant scaffold subtypes were identified: hydrogels, acellular extracellular matrices, and hyaluronic acid. Each scaffold-exosome design showcased unique properties with relation to gross findings, tissue histology, biomechanics, and gene expression. All designs demonstrated a reduction in inflammation and induction of tissue regeneration. The results of our review show that current exosome-scaffold therapeutics demonstrate the capability to halt and even reverse the course of post-traumatic cartilage injury and osteoarthritis. While this treatment modality shows incredible promise, future research should aim to characterize long-term biocompatibility and optimize scaffold designs for human treatment.

3D Printing of Microenvironment-Specific Bioinspired and Exosome-Reinforced Hydrogel Scaffolds for Efficient Cartilage and Subchondral Bone Regeneration

In clinical practice, repairing osteochondral defects presents a challenge due to the varying biological properties of articular cartilages and subchondral bones. Thus, elucidating how spatial microenvironment-specific biomimetic scaffolds can be used to simultaneously regenerate osteochondral tissue is an important research topic. Herein, a novel bioinspired double-network hydrogel scaffold produced via 3D printing with tissue-specific decellularized extracellular matrix (dECM) and human adipose mesenchymal stem cell (MSC)-derived exosomes is described. The bionic hydrogel scaffolds promote rat bone marrow MSC attachment, spread, migration, proliferation, and chondrogenic and osteogenic differentiation in vitro, as determined based on the sustained release of bioactive exosomes. Furthermore, the 3D-printed microenvironment-specific heterogeneous bilayer scaffolds efficiently accelerate the simultaneous regeneration of cartilage and subchondral bone tissues in a rat preclinical model. In conclusion, 3D dECM-based microenvironment-specific biomimetics encapsulated with bioactive exosomes can serve as a novel cell-free recipe for stem cell therapy when treating injured or degenerative joints. This strategy provides a promising platform for complex zonal tissue regeneration whilst holding attractive clinical translation potential.

Placenta-Derived Products Demonstrate Good Safety Profile and Overall Satisfactory Outcomes for Treating Knee Osteoarthritis: A Systematic Review of Clinical Evidence

PURPOSE

To summarize the available evidence regarding the clinical application of placenta-derived products to treat knee osteoarthritis (OA), underlining the differences existing among products, their preparation methods, and the clinical results reported so far.

METHODS

A research on PubMed, Cochrane, and Google Scholar databases was performed. The following inclusion criteria for relevant articles were used: (1) randomized controlled trials (RCTs), prospective and retrospective studies, on humans; (2) written in English; (3) published in indexed journals in the last 10 years (2011-2022); and (4) dealing with the use of placenta-derived products for the treatment of knee OA. Exclusion criteria were articles written in other languages; animals or in vitro trials; reviews; and trials analyzing other applications of placenta-derived products not related to knee OA.

RESULTS

In total, 16 studies were included in the present systematic review. Five studies investigated placenta-derived products as an augmentation during surgical procedures, whereas 11 studies were focused on the injective approach only. Of these, only 4 were RCTs and were all from the injective approach group. Potential risk of bias was carried out using Cochrane Risk of Bias 2 tool for RCTs and a modified Coleman approach for nonrandomized studies, revealing for both an overall insufficient quality. Clinical outcomes reveal excellent safety profile and notable efficacy, despite the different types of products used and different administration methods adopted.

CONCLUSIONS

Placental products showed a good safety profile and overall satisfactory outcomes for the treatment of knee OA.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II, III and IV studies.

Small extracellular vesicles from mesenchymal stromal cells: the next therapeutic paradigm for musculoskeletal disorders

Musculoskeletal disorders are one of the biggest contributors to morbidity and place an enormous burden on the health care system in an aging population. Owing to their immunomodulatory and regenerative properties, mesenchymal stromal/stem cells (MSCs) have demonstrated therapeutic efficacy for treatment of a wide variety of conditions, including musculoskeletal disorders. Although MSCs were originally thought to differentiate and replace injured/diseased tissues, it is now accepted that MSCs mediate tissue repair through secretion of trophic factors, particularly extracellular vesicles (EVs). Endowed with a diverse cargo of bioactive lipids, proteins, nucleic acids and metabolites, MSC-EVs have been shown to elicit diverse cellular responses and interact with many cell types needed in tissue repair. The present review aims to summarize the latest advances in the use of native MSC-EVs for musculoskeletal regeneration, examine the cargo molecules and mechanisms underlying their therapeutic effects, and discuss the progress and challenges in their translation to the clinic.

A roadmap from research to clinical testing of mesenchymal stromal cell exosomes in the treatment of psoriasis

The most clinically trialed cells, mesenchymal stromal cells (MSCs), are now known to mainly exert their therapeutic activity through paracrine secretions, which include exosomes. To mitigate potential regulatory concerns on the scalability and reproducibility in the preparations of MSC exosomes, MSC exosomes were produced using a highly characterized MYC-immortalized monoclonal cell line. These cells do not form tumors in athymic nude mice or exhibit anchorage-independent growth, and their exosomes do not carry MYC protein or promote tumor growth. Unlike intra-peritoneal injections, topical applications of MSC exosomes in a mouse model of IMQ-induced psoriasis alleviate interleukin (IL)-17, IL-23 and terminal complement complex, C5b9 in psoriatic skin. When applied on human skin explants, fluorescence from covalently labeled fluorescent MSC exosomes permeated and persisted in the stratum corneum for about 24 hours with negligible exit out of the stratum corneum into the underlying epidermis. As psoriatic stratum corneums are uniquely characterized by activated complements and Munro microabscesses, we postulated that topically applied exosomes permeate the psoriatic stratum corneum to inhibit C5b9 complement complex through CD59, and this inhibition attenuated neutrophil secretion of IL-17. Consistent with this, we demonstrated that assembly of C5b9 on purified human neutrophils induced IL-17 secretion and this induction was abrogated by MSC exosomes, which was in turn abrogated by a neutralizing anti-CD 59 antibody. We thus established the mechanism of action for the alleviation of psoriatic IL-17 by topically applied exosomes.

Bone/cartilage organoid on-chip: Construction strategy and application

The necessity of disease models for bone/cartilage related disorders is well-recognized, but the barrier between ex-vivo cell culture, animal models and the real human body has been pending for decades. The organoid-on-a-chip technique showed opportunity to revolutionize basic research and drug screening for diseases like osteoporosis and arthritis. The bone/cartilage organoid on-chip (BCoC) system is a novel platform of multi-tissue which faithfully emulate the essential elements, biologic functions and pathophysiological response under real circumstances. In this review, we propose the concept of BCoC platform, summarize the basic modules and current efforts to orchestrate them on a single microfluidic system. Current disease models, unsolved problems and future challenging are also discussed, the aim should be a deeper understanding of diseases, and ultimate realization of generic ex-vivo tools for further therapeutic strategies of pathological conditions.

Arthroscopy and Musculoskeletal Biologics

Orthopaedic biologics holds great promise. Absent peer-reviewed clinical musculoskeletal research, orthobiologics indications and treatment recommendations will remain opaque. In a Call for Papers, Arthroscopy; Arthroscopy Techniques; and Arthroscopy, Sports Medicine, and Rehabilitation editors invite authors to submit clinical musculoskeletal biologics original scientific research, and technical notes with video. Each year, the top articles will be awarded inclusion in an annual Biologics Special Issue. Future investigators and current readers could follow the science while being mindful of the regulatory environment.

Orthopaedic Musculoskeletal Biologics Research Impacts Patient Care: The First Annual Arthroscopy Orthobiologics Virtual Special Issue

Orthobiologics can modify symptoms and improve healing in a variety of musculoskeletal conditions as a part of office-based care or as an adjunct to surgery. Orthobiologics harness the benefits of naturally derived blood components, autologous tissue, and growth factors to reduce inflammation and optimize the host-healing environment. The Arthroscopy family of journals seeks to positively influence evidence-based clinical decision-making by publishing peer-reviewed biologics research. This special issue contains recent influential articles strategically chosen to positively impact patient care.

Mesenchymal Stem Cell Exosomes as Immunomodulatory Therapy for Corneal Scarring

Corneal scarring is a leading cause of worldwide blindness. Human mesenchymal stem cells (MSC) have been reported to promote corneal wound healing through secreted exosomes. This study investigated the wound healing and immunomodulatory effects of MSC-derived exosomes (MSC-exo) in corneal injury through an established rat model of corneal scarring. After induction of corneal scarring by irregular phototherapeutic keratectomy (irrPTK), MSC exosome preparations (MSC-exo) or PBS vehicle as controls were applied to the injured rat corneas for five days. The animals were assessed for corneal clarity using a validated slit-lamp haze grading score. Stromal haze intensity was quantified using in-vivo confocal microscopy imaging. Corneal vascularization, fibrosis, variations in macrophage phenotypes, and inflammatory cytokines were evaluated using immunohistochemistry techniques and enzyme-linked immunosorbent assays (ELISA) of the excised corneas. Compared to the PBS control group, MSC-exo treatment group had faster epithelial wound closure (0.041), lower corneal haze score (p = 0.002), and reduced haze intensity (p = 0.004) throughout the follow-up period. Attenuation of corneal vascularisation based on CD31 and LYVE-1 staining and reduced fibrosis as measured by fibronectin and collagen 3A1 staining was also observed in the MSC-exo group. MSC-exo treated corneas also displayed a regenerative immune phenotype characterized by a higher infiltration of CD163+, CD206+ M2 macrophages over CD80+, CD86+ M1 macrophages (p = 0.023), reduced levels of pro-inflammatory IL-1β, IL-8, and TNF-α, and increased levels of anti-inflammatory IL-10. In conclusion, topical MSC-exo could alleviate corneal insults by promoting wound closure and reducing scar development, possibly through anti-angiogenesis and immunomodulation towards a regenerative and anti-inflammatory phenotype.

Tropoelastin-Pretreated Exosomes from Adipose-Derived Stem Cells Improve the Synthesis of Cartilage Matrix and Alleviate Osteoarthritis

Mesenchymal stem cells (MSCs) have recently been widely used to treat osteoarthritis (OA). Our prior research shows that tropoelastin (TE) increases MSC activity and protects knee cartilage from OA-related degradation. The underlying mechanism might be that TE regulates the paracrine of MSCs. Exosomes (Exos), the paracrine secretion of MSCs, have been found to protect chondrocytes, reduce inflammation, and preserve the cartilage matrix. In this study, we used Exos derived from TE-pretreated adipose-derived stem cells (ADSCs) (TE-Exo^ADSCs) as an injection medium, and compared it with Exos derived from unpretreated ADSCs (Exo^ADSCs). We found that TE-Exo^ADSCs could effectively enhance the matrix synthesis of chondrocytes in vitro. Moreover, TE pretreatment increased the ability of ADSCs to secrete Exos. In addition, compared with Exo^ADSCs, TE-Exo^ADSCs exhibited therapeutic effects in the anterior cruciate ligament transection (ACLT)-induced OA model. Further, we observed that TE altered the microRNA expression in Exo^ADSCs and identified one differentially upregulated microRNA: miR-451-5p. In conclusion, TE-Exo^ADSCs helped maintain the chondrocyte phenotype in vitro, and promoted cartilage repair in vivo. These therapeutic effects might be related with the altered expression of miR-451-5p in the Exo^ADSCs. Thus, the intra-articular delivery of Exos derived from ADSCs with TE pretreatment could be a new approach to treat OA.

Current knowledge and future perspectives on exosomes in the field of regenerative medicine: a bibliometric analysis

Objective: This study aimed to use bibliometric analysis to qualitatively and quantitatively evaluate the research of exosomes in the field of regenerative medicine and to provide research hotspots and trends in this field. Materials & methods: Bibliometric analysis and data presentation were performed by VOSviewer and Microsoft Excel. Results: China was the major contributor to research in this field and enjoys a high reputation in academia. The highest contributing institution is Shanghai Jiao Tong University. Research hotspots included exosome-mediated neurovascular regeneration, exosome mechanism research, exosome-mediated cartilage regeneration and repair and exosome-mediated cardiac regeneration. Research was trending in the treatment of osteoarthritis, knee disease and cartilage regeneration and repair. Conclusion: This study provides a panoramic view of the application of exosomes in regenerative medicine.

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.

Research advances and challenges in tissue-derived extracellular vesicles

Extracellular vesicles (EV) are vesicular vesicles with phospholipid bilayer, which are present in biological fluids and extracellular microenvironment. Extracellular vesicles serve as pivotal mediators in intercellular communication by delivering lipids, proteins, and RNAs to the recipient cells. Different from extracellular vesicles derived from biofluids and that originate from cell culture, the tissue derived extracellular vesicles (Ti-EVs) send us more enriched and accurate information of tissue microenvironment. Notably, tissue derived extracellular vesicles directly participate in the crosstalk between numerous cell types within microenvironment. Current research mainly focused on the extracellular vesicles present in biological fluids and cell culture supernatant, yet the studies on tissue derived extracellular vesicles are increasing due to the tissue derived extracellular vesicles are promising agents to reflect the occurrence and development of human diseases more accurately. In this review, we aimed to clarify the characteristics of tissue derived extracellular vesicles, specify the isolation methods and the roles of tissue derived extracellular vesicles in various diseases, including tumors. Moreover, we summarized the advances and challenges of tissue derived extracellular vesicles research.

Functional biomaterials for osteoarthritis treatment: From research to application

Osteoarthritis (OA) is a common disease that endangers millions of middle-aged and elderly people worldwide. Researchers from different fields have made great efforts and achieved remarkable progress in the pathogenesis and treatment of OA. However, there is still no cure for OA. In this review, we discuss the pathogenesis of OA and summarize the current clinical therapies. Moreover, we introduce various natural and synthetic biomaterials for drug release, cartilage transplantation, and joint lubricant during the OA treatment. We also present our perspectives and insights on OA treatment in the future. We hope that this review will foster communication and collaboration among biological, clinical, and biomaterial researchers, paving the way for OA therapeutic breakthroughs.

Osteoporosis treatment by mesenchymal stromal/stem cells and their exosomes: Emphasis on signaling pathways and mechanisms

Osteoporosis is the loss of bone density, which is one of the main problems in developed and developing countries and is more common in the elderly. Because this disease is often not diagnosed until a bone fracture, it can become a life-threatening disease and cause hospitalization. With the increase of older people in a population, this disease's personal and social costs increase year by year and affect different communities. Most current treatments focus on pain relief and usually do not lead to bone tissue recovery and regeneration. But today, the use of stem cell therapy is recommended to treat and improve this disease recovery, which helps restore bone tissue by improving the imbalance in the osteoblast-osteoclast axis. Due to mesenchymal stromal/stem cells (MSCs) characteristics and their exosomes, these cells and vesicles are excellent sources for treating and preventing the progression and improvement of osteoporosis. Due to the ability of MSCs to differentiate into different cells and migrate to the site of injury, these cells are used in tissue regenerative medicine. Also, due to their contents, the exosomes of these cells help regenerate and treat various tissue injuries by affecting the injury site's cells. In this article, we attempted to review new studies in which MSCs and their exosomes were used to treat osteoporosis.

Exosome-based strategy for degenerative disease in orthopedics: Recent progress and perspectives

BACKGROUND

Degenerative diseases in orthopaedics have become a significant global public health issue with the aging of the population worldwide. The traditional medical interventions, including physical therapy, pharmacological therapy and even surgery, hardly work to modify degenerative progression. Stem cell-based therapy is widely accepted to treat degenerative orthopaedic disease effectively but possesses several limitations, such as the need for strict monitoring of production and storage and the potential risks of tumorigenicity and immune rejection in clinical translation. Furthermore, the ethical issues surrounding the acquisition of embryonic stem cells are also broadly concerned. Exosome-based therapy has rapidly grown in popularity in recent years and is regarded as an ideal alternative to stem cell-based therapy, offering a promise to achieve 'cell-free' tissue regeneration.

METHODS

Traditionally, the native exosomes extracted from stem cells are directly injected into the injured site to promote tissue regeneration. Recently, several modified exosome-based strategies were developed to overcome the limitations of native exosomes, which include mainly exogenous molecule loading and exosome delivery through scaffolds. In this paper, a systematic review of the exosome-based strategy for degenerative disease in orthopaedics is presented.

RESULTS

Treatment strategies based on the native exosomes are effective but with several disadvantages such as rapid diffusion and insufficient and fluctuating functional contents. The modified exosome-based strategies can better match the requirements of the regeneration in some complex healing processes.

CONCLUSION

Exosome-based strategies hold promise to manage degenerative disease in orthopaedics prior to patients reaching the advanced stage of disease in the future. The timely summary and highlights offered herein could provide a research perspective to promote the development of exosome-based therapy, facilitating the clinical translation of exosomes in orthopaedics.

TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Exosome-based therapy is superior in anti-senescence and anti-inflammatory effects and possesses lower risks of tumorigenicity and immune rejection relative to stem cell-based therapy. Exosome-based therapy is regarded as an ideal alternative to stem cell-based therapy, offering a promise to achieve 'cell-free' tissue regeneration.

Recent Developments and Current Applications of Organic Nanomaterials in Cartilage Repair

Regeneration of cartilage is difficult due to the unique microstructure, unique multizone organization, and avascular nature of cartilage tissue. The development of nanomaterials and nanofabrication technologies holds great promise for the repair and regeneration of injured or degenerated cartilage tissue. Nanomaterials have structural components smaller than 100 nm in at least one dimension and exhibit unique properties due to their nanoscale structure and high specific surface area. The unique properties of nanomaterials include, but are not limited to, increased chemical reactivity, mechanical strength, degradability, and biocompatibility. As an emerging nanomaterial, organic nanocomposites can mimic natural cartilage in terms of microstructure, physicochemical, mechanical, and biological properties. The integration of organic nanomaterials is expected to develop scaffolds that better mimic the extracellular matrix (ECM) environment of cartilage to enhance scaffold-cell interactions and improve the functionality of engineered tissue constructs. Next-generation hydrogel technology and bioprinting can be used not only for healing cartilage injury areas but also for extensive osteoarthritic degenerative changes within the joint. Although more challenges need to be solved before they can be translated into full-fledged commercial products, nano-organic composites remain very promising candidates for the future development of cartilage tissue engineering.

Engineering of MSC-Derived Exosomes: A Promising Cell-Free Therapy for Osteoarthritis

Osteoarthritis (OA) is characterized by progressive cartilage degeneration with increasing prevalence and unsatisfactory treatment efficacy. Exosomes derived from mesenchymal stem cells play an important role in alleviating OA by promoting cartilage regeneration, inhibiting synovial inflammation and mediating subchondral bone remodeling without the risk of immune rejection and tumorigenesis. However, low yield, weak activity, inefficient targeting ability and unpredictable side effects of natural exosomes have limited their clinical application. At present, various approaches have been applied in exosome engineering to regulate their production and function, such as pretreatment of parental cells, drug loading, genetic engineering and surface modification. Biomaterials have also been proved to facilitate efficient delivery of exosomes and enhance treatment effectiveness. Here, we summarize the current understanding of the biogenesis, isolation and characterization of natural exosomes, and focus on the large-scale production and preparation of engineered exosomes, as well as their therapeutic potential in OA, thus providing novel insights into exploring advanced MSC-derived exosome-based cell-free therapy for the treatment of OA.

Mesenchymal Stem Cell Exosomes Promote Growth Plate Repair and Reduce Limb-Length Discrepancy in Young Rats

BACKGROUND

The objective of this study was to examine the therapeutic effects of human mesenchymal stromal/stem cell (MSC) exosomes in a rat model of growth plate injury.

METHODS

A growth plate defect was surgically created on the distal part of the right femur of 40 female Sprague-Dawley rats. A single intra-articular injection of 100 µg of MSC exosomes in 100 µL of phosphate-buffered saline solution (PBS), or an equivalent volume of PBS alone, was administered to the right knee immediately after surgery. At 4 and 8 weeks post-treatment, limb length was measured with micro-CT, and tissue repair was assessed with histological, immunohistochemical, and histomorphometric analyses.

RESULTS

A single injection of MSC exosomes significantly increased limb length from 3.29 ± 0.07 cm at 4 weeks to 3.37 ± 0.11 cm at 8 weeks (p = 0.047). However, no improvement in limb length was observed in the PBS control group. The limb-length discrepancy between the involved limb and the contralateral limb in the exosome-treated group was significantly less than the discrepancy in the PBS-treated group at both 4 weeks (2.52% ± 1.30% versus 4.11% ± 0.93%; p = 0.006) and 8 weeks (5.27% ± 2.11% versus 8.06% ± 2.56%; p = 0.016). Consistent with the reduced limb-length discrepancy, the exosome-treated defects displayed significantly more chondrocytes (p < 0.05) and a higher area percentage with deposition of sulphated glycosaminoglycan (p < 0.05) and collagen II (p < 0.05) than PBS-treated defects at 8 weeks. However, bone bridge formation was not inhibited in either group.

CONCLUSIONS

A single intra-articular injection of MSC exosomes significantly enhanced physeal repair and reduced limb-length discrepancy but did not inhibit bone-bridge formation.

CLINICAL RELEVANCE

This proof-of-concept study demonstrates for the first time the potential use of MSC exosomes as a minimally invasive cell-free therapeutic to promote physeal repair and reduce limb-length discrepancy following growth plate injuries.

The Research Progress of Exosomes in Osteoarthritis, With Particular Emphasis on the Therapeutic Effect

Exosomes participate in many physiological and pathological processes by regulating cell-to-cell communication. This affects the etiology and development of diseases, such as osteoarthritis (OA). Although exosomes in the OA tissue microenvironment are involved in the progression of OA, exosomes derived from therapeutic cells represent a new therapeutic strategy for OA treatment. Recent studies have shown that exosomes participate in OA treatment by regulating the proliferation, apoptosis, inflammation, and extracellular matrix synthesis of chondrocytes. However, studies in this field are scant. This review summarizes the therapeutic properties of exosomes on chondrocytes in OA and their underlying molecular mechanisms. We also discuss the challenges and prospects of exosome-based OA treatment.

Regenerative medicine 2.0: extracellular vesicle-based therapeutics for musculoskeletal tissue regeneration

In recent years, extracellular vesicles (EVs) have emerged as prominent mediators of the homeostasis, repair, and regeneration of musculoskeletal tissues including bone, skeletal muscle, and cartilage. Accordingly, the therapeutic potential of EVs for regenerative medicine applications has not gone unnoticed. The use of EVs for the treatment of musculoskeletal injury and disease in veterinary species is a nascent but rapidly expanding area of research. Recent studies in this area have demonstrated the safety and feasibility of EV products in dogs and horses. While early clinical responses to EV-based therapeutics in companion animals have been favorable, more rigorously designed, sufficiently powered, and placebo-controlled clinical trials are required to fully elucidate the clinical benefits and best-use scenarios for EV therapeutics in veterinary medicine. Additionally, clinical translation of EV-based therapeutics will require Good Manufacturing Practice-compliant methods to scale up and purify EV products. Despite these challenges, EVs hold great promise in the regenerative medicine landscape, particularly in the treatment of musculoskeletal injury and disease in companion animals.

Therapeutic potential of mesenchymal stem cell-derived exosomes as a cell-free therapy approach for the treatment of skin, bone, and cartilage defects

OBJECTIVE

The aim of this study was to collect the articles concerning mesenchymal stem cell (MSC)-derived exosomes for regeneration of bone, cartilage and skin defects.

METHOD

Scopus, PubMed, EMBASE, and Web of Science were searched for keywords "Exosome, MSC, Skin, Bone and Cartilage defects, Regenerative medicine, and extracellular vesicles.

RESULTS

MSC-derived exosomes can emulate the biological activity of MSCs by horizontal transfer of multiple functional molecules including mRNAs, miRNAs, proteins, and lipids to the local microenvironment and recipient cells, and subsequently mediate restoring homeostasis and tissue regeneration through various mechanisms. Compared to MSCs, MSC-derived exosomes reveal many advantages such as non-immunogenicity, easy access, easy preservation, and extreme stability under various conditions.

CONCLUSION

Hence, exosomes could be considered as an alternative strategy for cell-based therapies in regenerative medicine. In this paper, after describing the characteristics of exosomes, we will review the recent literature on the therapeutic potentials of MSC-derived exosomes in skin, bone, and cartilage repair.

Mesenchymal Stem Cell Exosomes Promote Functional Osteochondral Repair in a Clinically Relevant Porcine Model

BACKGROUND

Previous studies have reported the efficacy of human mesenchymal stem cell (MSC) exosomes for the repair of osteochondral defects in rats and rabbits. However, the safety and efficacy of MSC exosomes remain to be validated in a clinically relevant large animal model.

PURPOSE

To validate the safety and efficacy of human MSC exosomes for osteochondral repair in a clinically relevant micropig model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Bilateral osteochondral defects (6-mm diameter and 1-mm depth) were surgically created in the medial femoral condyles in knees of 12 micropigs. The pigs then received 2-mL intra-articular injections of MSC exosomes and hyaluronic acid (HA) (Exosome+HA) or HA alone after surgery and thereafter at 8 and 15 days. Osteochondral repair was assessed by magnetic resonance imaging (MRI) at 15 days and at 2 and 4 months after surgery as well as by macroscopic, histological, biomechanical, and micro-computed tomography (micro-CT) analyses at 4 months after surgery.

RESULTS

Exosome+HA-treated defects demonstrated significantly better MRI scores than HA-treated defects at 15 days and at 2 and 4 months. Additionally, Exosome+HA-treated defects demonstrated functional cartilage and subchondral bone repair, with significantly better macroscopic and histological scores and biomechanical properties (Young modulus and stiffness) than HA-treated defects at 4 months. Micro-CT further showed significantly higher bone volume and trabecular thickness in the subchondral bone of Exosome+HA-treated defects than that of HA-treated defects. Importantly, no adverse response or major systemic alteration was observed in any of the animals.

CONCLUSION

This study shows that the combination of MSC exosomes and HA administered at a clinically acceptable frequency of 3 weekly intra-articular injections can promote functional cartilage and subchondral bone repair, with significantly improved morphological, histological, and biomechanical outcomes in a clinically relevant porcine model.

CLINICAL RELEVANCE

Our findings provide a robust scientific rationale to support a phase 1/2 clinical trial to test MSC exosomes in patients with osteochondral lesions.

Extracellular vesicles: a promising cell-free therapy for cartilage repair

Few effective therapies for cartilage repair have been found as cartilage has a low regenerative capacity. Extracellular vesicles (EVs), including exosomes, are produced by cells and contain bioactive components such as nucleic acids, proteins, lipids and other metabolites that have potential for treating cartilage injuries. Challenges like the difficulty in standardizing targeted therapy have prevented EVs from being used frequently as a treatment option. In this review we present current studies, mechanisms and delivery strategies of EVs. Additionally, we describe the challenges and future directions of EVs as therapeutic agents for cartilage repair.

Repairing cartilage damage is challenging due to the tissue’s low regenerative capacity. Extracellular vesicles (EVs) contain bioactive components that may be able to treat cartilage injuries. However, EV-based therapy is not widely used. This review summarizes the current state of knowledge regarding the use of EVs for cartilage repair, including the mechanisms, delivery strategies, challenges and future directions.

Autologous Platelet-Rich Fibrin Membrane to Augment Healing of Microfracture Has Better Macroscopic and Histologic Grades Compared With Microfracture Alone on Chondral Defects in a Rabbit Model

PURPOSE

To determine the in vivo effectiveness of a single-stage surgical procedure that combines microfracture and an autologous platelet-rich fibrin (PRF) membrane for cartilage repair in a rabbit model.

METHODS

Cartilage defects were created in the trochlear groove of the knees of adult white rabbits. Defects were divided into 2 treatment groups: microfracture only (control group) and microfracture covered by a PRF membrane (PRF group). To evaluate the repair cartilage, assessments were performed at 4, 12, and 24 weeks postoperatively using the International Cartilage Repair Society (ICRS) macroscopic scoring system and modified Wakitani histologic grading system.

RESULTS

The mean ICRS macroscopic scores in the control and PRF groups were 4.1 and 5.8, respectively, at 4 weeks (P = .0623); 6.3 and 9.8, respectively, at 12 weeks (P = .006); and 6.5 and 10.3, respectively, at 24 weeks (P = .010). The mean modified Wakitani scores in the control and PRF groups were 4.0 and 3.9, respectively, at 4 weeks (P > .999); 5.3 and 10.4, respectively, at 12 weeks (P = .006); and 2.6 and 7.4, respectively, at 24 weeks (P = .012).

CONCLUSIONS

The ICRS macroscopic scores and modified Wakitani scores showed that a single-stage surgical procedure combining microfracture and a PRF membrane was more effective than surgery with only microfracture for promoting cartilage repair.

CLINICAL RELEVANCE

A single-stage surgical procedure combining microfracture and an autologous PRF membrane is a potentially beneficial treatment method for cartilage defects that does not require using any xenocollagen membrane.

Exosomes: A Tool for Bone Tissue Engineering

Mesenchymal stem cells (MSCs) have been repeatedly shown to be a valuable source for cell-based therapy in regenerative medicine, including bony tissue repair. However, engraftment at the injury site is poor. Recently, it has been suggested that MSCs and other cells act through a paracrine signaling mechanism. Exosomes are nanostructures that have been implicated in this process. They carry DNA, RNA, proteins, and lipids and play an important role in cell-to-cell communication directly modulating their target cell at a transcriptional level. In a bone microenvironment, they have been shown to increase osteogenesis and osteogenic differentiation in vivo and in vitro. In the following review, we will discuss the most advanced and significant knowledge of biological functions of exosomes in bone regeneration and their clinical applications in osseous diseases. Impact statement Mesenchymal stem cells have been shown to be a promising tool in bone tissue engineering. Recently, it has been suggested that they secrete exosomes containing messenger RNA, proteins, and lipids, thus acting through paracrine signaling mechanisms. Considering that exosomes are nonteratogenic and have low immunogenic potential, they could potentially replace stem-cell based therapy and thus eradicate the risk of neoplastic transformation associated with cell transplantations in bone regeneration.

State of the Art: The Immunomodulatory Role of MSCs for Osteoarthritis

Osteoarthritis (OA) has generally been introduced as a degenerative disease; however, it has recently been understood as a low-grade chronic inflammatory process that could promote symptoms and accelerate the progression of OA. Current treatment strategies, including corticosteroid injections, have no impact on the OA disease progression. Mesenchymal stem cells (MSCs) based therapy seem to be in the spotlight as a disease-modifying treatment because this strategy provides enlarged anti-inflammatory and chondroprotective effects. Currently, bone marrow, adipose derived, synovium-derived, and Wharton's jelly-derived MSCs are the most widely used types of MSCs in the cartilage engineering. MSCs exert immunomodulatory, immunosuppressive, antiapoptotic, and chondrogenic effects mainly by paracrine effect. Because MSCs disappear from the tissue quickly after administration, recently, MSCs-derived exosomes received the focus for the next-generation treatment strategy for OA. MSCs-derived exosomes contain a variety of miRNAs. Exosomal miRNAs have a critical role in cartilage regeneration by immunomodulatory function such as promoting chondrocyte proliferation, matrix secretion, and subsiding inflammation. In the future, a personalized exosome can be packaged with ideal miRNA and proteins for chondrogenesis by enriching techniques. In addition, the target specific exosomes could be a gamechanger for OA. However, we should consider the off-target side effects due to multiple gene targets of miRNA.

Biomaterials-assisted exosomes therapy in osteoarthritis

Due to the avascular characteristic of articular cartilage, its self-repair capacity is limited. When cartilage is damaged or forms osteoarthritis, clinical treatment is necessary. However, conventional treatments, including joint replacement, microfracture, cell and drug therapies, have certain limits. Lately, the exosomes derived from mesenchymal stem cells (MSCs-EXO), which consist of complex transcription factors, proteins and targeting ligand components, have shown great therapeutic potentials. With recent advancements in various biomaterials to extend MSCs-EXO's retention time and control the release properties in vivo, biomaterials-assisted exosomes therapy has been soon becoming a practically powerful tool in treating OA. This review analyzes the effects of MSCs-EXO on osteoarthritis inflammation, metabolism, ageing and apoptosis, and introduces the combinational systems of MSCs-EXO with biomaterials to enhance the repair, anti-inflammatory, and homeostasis regulation functions. Moreover, different types of natural or synthetic biomaterials and their applications with MSCs-EXO were also described and discussed. And finally, we presage the future perspective in the development of biomaterial-assisted exosome therapies, as well as the potential to incorporate with other treatments to enhance their therapeutic effects in osteoarthritis.

Harnessing Tissue-derived Extracellular Vesicles for Osteoarthritis Theranostics

Osteoarthritis (OA) is a prevalent chronic whole-joint disease characterized by low-grade systemic inflammation, degeneration of joint-related tissues such as articular cartilage, and alteration of bone structures that can eventually lead to disability. Emerging evidence has indicated that synovium or articular cartilage-secreted extracellular vesicles (EVs) contribute to OA pathogenesis and physiology, including transporting and enhancing the production of inflammatory mediators and cartilage degrading proteinases. Bioactive components of EVs are known to play a role in OA include microRNA, long non-coding RNA, and proteins. Thus, OA tissues-derived EVs can be used in combination with advanced nanomaterial-based biosensors for the diagnostic assessment of OA progression. Alternatively, mesenchymal stem cell- or platelet-rich plasma-derived EVs (MSC-EVs or PRP-EVs) have high therapeutic value for treating OA, such as suppressing the inflammatory immune microenvironment, which is often enriched by pro-inflammatory immune cells and cytokines that reduce chondrocytes apoptosis. Moreover, those EVs can be modified or incorporated into biomaterials for enhanced targeting and prolonged retention to treat OA effectively. In this review, we explore recently reported OA-related pathological biomarkers from OA joint tissue-derived EVs and discuss the possibility of current biosensors for detecting EVs and EV-related OA biomarkers. We summarize the applications of MSC-EVs and PRP-EVs and discuss their limitations for cartilage regeneration and alleviating OA symptoms. Additionally, we identify advanced therapeutic strategies, including engineered EVs and applying biomaterials to increase the efficacy of EV-based OA therapies. Finally, we provide our perspective on the future of EV-related diagnosis and therapeutic potential for OA treatment.

OUP accepted manuscript

Mesenchymal progenitor cells (MPCs) have shown promise initiating articular cartilage repair, with benefits largely attributed to the trophic factors they secrete. These factors can be found in the conditioned medium (CM) collected from cell cultures, and it is believed that extracellular vesicles (EVs) within this CM are at least partially responsible for MPC therapeutic efficacy. This study aimed to examine the functionality of the EV fraction of CM compared to whole CM obtained from human adipose-derived MPCs in an in vivo murine cartilage defect model. Mice treated with whole CM or the EV fraction demonstrated an enhanced cartilage repair score and type II collagen deposition at the injury site compared to saline controls. We then developed a scalable bioprocess using stirred suspension bioreactors (SSBs) to generate clinically relevant quantities of MPC-EVs. Whereas static monolayer culture systems are simple to use and readily accessible, SSBs offer increased scalability and a more homogenous environment due to constant mixing. This study evaluated the biochemical and functional properties of MPCs and their EV fractions generated in static culture versus SSBs. Functionality was assessed using in vitro MPC chondrogenesis as an outcome measure. SSBs supported increased MPC expression of cartilage-specific genes, and EV fractions derived from both static and SSB culture systems upregulated type II collagen production by MPCs. These results suggest that SSBs are an effective platform for the generation of MPC-derived EVs with the potential to induce cartilage repair.

The Potential Use of Mesenchymal Stem Cells and Their Derived Exosomes for Orthopedic Diseases Treatment

Musculoskeletal disorders (MSDs) are conditions that can affect muscles, bones, and joints. These disorders are very painful and severely limit patients' mobility and are more common in the elderly. MSCs are multipotent stem cells isolated from embryonic (such as the umbilical cord) and mature sources (such as adipose tissue and bone marrow). These cells can differentiate into various cells such as osteoblasts, adipocytes, chondrocytes, NP-like cells, Etc. Due to MSC characteristics such as immunomodulatory properties, ability to migrate to the site of injury, recruitment of cells involved in repair, production of growth factors, and large amount production of extracellular vesicles, these cells have been used in many regenerative-related medicine studies. Also, MSCs produce different types of EVs, such as exosomes, to the extracellular environment. Exosomes reflect MSCs' characteristics and do not have cell therapy-associated problems because they are cell-free. These vesicles carry proteins, nucleic acids, and lipids to the host cell and change their function. This review focuses on MSCs and MSCs exosomes' role in repairing dense connective tissues such as tendons, cartilage, invertebrate disc, bone fracture, and osteoporosis treatment.

Mesenchymal Stem Cell Extracellular Vesicles as Adjuvant to Bone Marrow Stimulation in Chondral Defect Repair in a Minipig Model

OBJECTIVE

This study evaluated the effects of mesenchymal stem cell-extracellular vesicles (MSC-EVs) on chondrocyte proliferation in vitro and on cartilage repair in vivo following bone marrow stimulation (BMS) of focal chondral defects of the knee.

METHODS

Six adult Göttingen minipigs received 2 chondral defects in each knee. The pigs were randomized to treatment with either BMS combined with MSC-EVs or BMS combined with phosphate-buffered saline (PBS). Intraarticular injections MSC-EVs or PBS were performed immediately after closure of the surgical incisions, and at 2 and 4 weeks postoperatively. Repair was evaluated after 6 months with gross examination, histology, histomorphometry, immunohistochemistry, and micro-computed tomography (µCT) analysis of the trabecular bone beneath the defect.

RESULTS

Defects treated with MSC-EVs had more bone in the cartilage defect area than the PBS-treated defects (7.9% vs. 1.5%, P = 0.02). Less than 1% of the repair tissue in both groups was hyaline cartilage. International Cartilage and Joint Preservation Society II histological scoring showed that defects treated with MSC-EVs scored lower on "matrix staining" (20.8 vs. 50.0, P = 0.03), "cell morphology" (35.4 vs. 53.8, P = 0.04), and "overall assessment" (30.8 vs. 52.9, P = 0.03). Consistently, defects treated with MSC-EVs had lower collagen II and higher collagen I areal deposition. Defects treated with MSC-EVs had subchondral bone with significantly higher tissue mineral densities than PBS-treated defects (860 mg HA/cm3 vs. 838 mg HA/cm3, P = 0.02).

CONCLUSION

Intraarticular injections of MSC-EVs in conjunction with BMS led to osseous ingrowth that impaired optimal cartilage repair, while enhancing subchondral bone healing.

Mesenchymal Stem Cell-Derived Exosomes and MicroRNAs in Cartilage Regeneration: Biogenesis, Efficacy, miRNA Enrichment and Delivery

Exosomes are the small extracellular vesicles secreted by cells for intercellular communication. Exosomes are rich in therapeutic cargos such as microRNA (miRNA), long non-coding RNA (lncRNA), small interfering RNA (siRNA), DNA, protein, and lipids. Recently, many studies have focused on miRNAs as a promising therapeutic factor to support cartilage regeneration. Exosomes are known to contain a substantial amount of a variety of miRNAs. miRNAs regulate the post-transcriptional gene expression by base-pairing with the target messenger RNA (mRNA), leading to gene silencing. Several exosomal miRNAs have been found to play a role in cartilage regeneration by promoting chondrocyte proliferation and matrix secretion, reducing scar tissue formation, and subsiding inflammation. The exosomal miRNA cargo can be modulated using techniques such as cell transfection and priming as well as post-secretion modifications to upregulate specific miRNAs to enhance the therapeutic effect. Exosomes are delivered to the joints through direct injection or via encapsulation within a scaffold for sustained release. To date, exosome therapy for cartilage injuries has yet to be optimized as the ideal cell source for exosomes, and the dose and method of delivery have yet to be identified. More importantly, a deeper understanding of the role of exosomal miRNAs in cartilage repair is paramount for the development of more effective exosome therapy.

Mesenchymal Stem Cell-Derived Extracellular Vesicles for Osteoarthritis Treatment: Extracellular Matrix Protection, Chondrocyte and Osteocyte Physiology, Pain and Inflammation Management

Osteoarthritis (OA) is a common degenerative disease that can lead to persistent pain and motion restriction. In the last decade, stem cells, particularly mesenchymal stem cells (MSCs), have been explored as a potential alternative OA therapy due to their regenerative capacity. Furthermore, it has been shown that trophic factors enveloped in extracellular vesicles (EVs), including exosomes, are a crucial aspect of MSC-based treatment for OA. Evidently, EVs derived from different MSC sources might rescue the OA phenotype by targeting many biological processes associated with cartilage extracellular matrix (ECM) degradation and exerting protective effects on different joint cell types. Despite this advancement, different studies employing EV treatment for OA have revealed reverse outcomes depending on the EV cargo, cell source, and pathological condition. Hence, in this review, we aim to summarize and discuss the possible effects of MSC-derived EVs based on recent findings at different stages of OA development, including effects on cartilage ECM, chondrocyte biology, osteocytes and bone homeostasis, inflammation, and pain management. Additionally, we discuss further strategies and technical advances for manipulating EVs to specifically target OA to bring the therapy closer to clinical use.

Potential of Exosomes as Cell-Free Therapy in Articular Cartilage Regeneration: A Review

Treatment of cartilage defects such as osteoarthritis (OA) and osteochondral defect (OCD) remains a huge clinical challenge in orthopedics. OA is one of the most common chronic health conditions and is mainly characterized by the degeneration of articular cartilage, shown in the limited capacity for intrinsic repair. OCD refers to the focal defects affecting cartilage and the underlying bone. The current OA and OCD management modalities focus on symptom control and on improving joint functionality and the patient’s quality of life. Cell-based therapy has been evaluated for managing OA and OCD, and its chondroprotective efficacy is recognized mainly through paracrine action. Hence, there is growing interest in exploiting extracellular vesicles to induce cartilage regeneration. In this review, we explore the in vivo evidence of exosomes on cartilage regeneration. A total of 29 in vivo studies from the PubMed and Scopus databases were identified and analyzed. The studies reported promising results in terms of in vivo exosome delivery and uptake; improved cartilage morphological, histological, and biochemical outcomes; enhanced subchondral bone regeneration; and improved pain behavior following exosome treatment. In addition, exosome therapy is safe, as the included studies documented no significant complications. Modifying exosomal cargos further increased the cartilage and subchondral bone regeneration capacity of exosomes. We conclude that exosome administration is a potent cell-free therapy for alleviating OA and OCD. However, additional studies are needed to confirm the therapeutic potential of exosomes and to identify the standard protocol for exosome-based therapy in OA and OCD management.

The role and therapeutic potential of MSC-derived exosomes in osteoarthritis

Osteoarthritis (OA) is the most common painful disease with chronic articular cartilage degeneration. The pathological process of OA is complex and characterized by the imbalance between the synthesis and catabolism of chondrocytes and extracellular matrix, leading to the progressive destruction of articular cartilage damage. Because of the self-renewal and differentiation of mesenchymal stem cells (MSCs), various exogenous MSC-based cell therapies have been developed to treat OA. Moreover, the efficacy of MSC- based therapy is mainly attributed to the paracrine of cytokines, growth factors, and exosomes. Exosomes derived from MSCs can deliver various DNAs, RNAs, proteins and lipids, thus promoting MSCs migration and cartilage repair. Therefore, MSC-derived exosomes are considered as a promising alternative therapy for OA. In this review, we summarized properties of MSC-derived exosomes and the new role of MSC-derived exosomes in the treatment of OA. We also proposed possible perspectives of MSC-derived exosomes as cell-free regenerative reagents in the treatment of OA.

Mesenchymal Stem Cell-Derived Exosomes: Applications in Regenerative Medicine

Exosomes are a type of extracellular vesicles, produced within multivesicular bodies, that are then released into the extracellular space through a merging of the multivesicular body with the plasma membrane. These vesicles are secreted by almost all cell types to aid in a vast array of cellular functions, including intercellular communication, cell differentiation and proliferation, angiogenesis, stress response, and immune signaling. This ability to contribute to several distinct processes is due to the complexity of exosomes, as they carry a multitude of signaling moieties, including proteins, lipids, cell surface receptors, enzymes, cytokines, transcription factors, and nucleic acids. The favorable biological properties of exosomes including biocompatibility, stability, low toxicity, and proficient exchange of molecular cargos make exosomes prime candidates for tissue engineering and regenerative medicine. Exploring the functions and molecular payloads of exosomes can facilitate tissue regeneration therapies and provide mechanistic insight into paracrine modulation of cellular activities. In this review, we summarize the current knowledge of exosome biogenesis, composition, and isolation methods. We also discuss emerging healing properties of exosomes and exosomal cargos, such as microRNAs, in brain injuries, cardiovascular disease, and COVID-19 amongst others. Overall, this review highlights the burgeoning roles and potential applications of exosomes in regenerative medicine.

Bone-a-Petite: Engineering Exosomes towards Bone, Osteochondral, and Cartilage Repair

Recovery from bone, osteochondral, and cartilage injuries/diseases has been burdensome owing to the damaged vasculature of large defects and/or avascular nature of cartilage leading to a lack of nutrients and supplying cells. However, traditional means of treatment such as microfractures and cell-based therapy only display limited efficacy due to the inability to ensure cell survival and potential aggravation of surrounding tissues. Exosomes have recently emerged as a powerful tool for this tissue repair with its complex content of transcription factors, proteins, and targeting ligands, as well as its unique ability to home in on target cells thanks to its phospholipidic nature. They are engineered to serve specialized applications including enhancing repair, anti-inflammation, regulating homeostasis, etc. via means of physical, chemical, and biological modulations in its deriving cell culture environments. This review focuses on the engineering means to functionalize exosomes for bone, osteochondral, and cartilage regeneration, with an emphasis on conditions such as osteoarthritis, osteoporosis, and osteonecrosis. Finally, future implications for exosome development will be given alongside its potential combination with other strategies to improve its therapeutic efficacy in the osteochondral niche.

A paradigm shift in cell-free approach: the emerging role of MSCs-derived exosomes in regenerative medicine

Recently, mesenchymal stem/stromal cells (MSCs) due to their pro-angiogenic, anti-apoptotic, and immunoregulatory competencies along with fewer ethical issues are presented as a rational strategy for regenerative medicine. Current reports have signified that the pleiotropic effects of MSCs are not related to their differentiation potentials, but rather are exerted through the release of soluble paracrine molecules. Being nano-sized, non-toxic, biocompatible, barely immunogenic, and owning targeting capability and organotropism, exosomes are considered nanocarriers for their possible use in diagnosis and therapy. Exosomes convey functional molecules such as long non-coding RNAs (lncRNAs) and micro-RNAs (miRNAs), proteins (e.g., chemokine and cytokine), and lipids from MSCs to the target cells. They participate in intercellular interaction procedures and enable the repair of damaged or diseased tissues and organs. Findings have evidenced that exosomes alone are liable for the beneficial influences of MSCs in a myriad of experimental models, suggesting that MSC- exosomes can be utilized to establish a novel cell-free therapeutic strategy for the treatment of varied human disorders, encompassing myocardial infarction (MI), CNS-related disorders, musculoskeletal disorders (e.g. arthritis), kidney diseases, liver diseases, lung diseases, as well as cutaneous wounds. Importantly, compared with MSCs, MSC- exosomes serve more steady entities and reduced safety risks concerning the injection of live cells, such as microvasculature occlusion risk. In the current review, we will discuss the therapeutic potential of MSC- exosomes as an innovative approach in the context of regenerative medicine and highlight the recent knowledge on MSC- exosomes in translational medicine, focusing on in vivo researches.