Exosomes derived from maxillary BMSCs enhanced the osteogenesis in iliac BMSCs

Diagnostic and therapeutic potential of oral cavity-derived exosomes in oral and maxillofacial tissue engineering: current advances and future perspectives

Oral and maxillofacial (OMF) tissue engineering has always been the subject of longstanding professional and academic debates. Despite rapidly evolving therapeutic approaches including reconstructive surgeries, tissue grafts, platelet-rich therapies, and mesenchymal stem cell-based treatments, there are remaining concerns regarding the therapeutic efficacy, safety profile, immunological compatibility, target-specificity, and ethical issues of such therapies. In addition to the multifactorial nature of OMF diseases, complex maxillofacial anatomy and neurovasculature further pinpoint the urgent need for breakthroughs in the era of OMF treatments. In recent years, exosomes have garnered immense popularity as the frontiers of regenerative medicine. Exosomes, natural nanovesicles secreted by a wide range of cells, act as nano messengers that harbor the rich molecular cargo received by their original cells and demonstrate important roles for diverse physiological and pathological intercellular communications. Among the different sources of exosomes, the oral cavity hosts a wide variety of mesenchymal stem cell-derived and salivary exosomes. Owing to the neural crest origin and multipotent differentiation, oral stem cell-derived exosomes hold great promise for OMF tissue engineering. Moreover, exosomes derived from pathological oral cavity cells and saliva samples provide diagnostic and prognostic signatures for different OMF diseases. This review highlights the cutting-edge diagnostic and therapeutic applications of oral cavity-derived exosomes in the field of OMF regeneration. Furthermore, we emphasize the existing challenges and constraints in exosome-based diagnostics and therapy, thus offering important perspectives for the future clinical application of exosomes derived from the oral cavity.

Therapeutic potential of stem cell-derived exosomes for bone tissue regeneration around prostheses

Artificial joint replacement is a widely recognized treatment for arthritis and other severe joint conditions. However, one of the primary causes of failure in joint replacements is the loosening of the prosthesis. After implantation, wear particles between the implant and the adjacent bone tissue are the principal contributors to this loosening. Recently, exosomes have garnered significant interest due to their low immunogenicity and effective membrane binding. They have shown potential in promoting bone regeneration via the paracrine pathway. This review examines the role and mechanisms of exosomes derived from mesenchymal stem cells (MSCs) in bone regeneration, their impact on the integration of various implants into surrounding bone tissue and current challenges and future directions for the clinical application of exosomes. The Translational Potential of this Article: Emerging evidence suggests that mesenchymal stem cell-derived exosomes may offer a promising therapeutic strategy for aseptic prosthesis loosening, potentially mediated through mechanisms such as modulation of inflammatory responses, suppression of osteoclastogenesis, enhancement of osteogenic differentiation and facilitation of bone regeneration. Preclinical studies further indicate that the therapeutic potential of these extracellular vesicles could be optimized through bioengineering strategies, including surface modification and cargo-loading techniques, warranting further investigation to advance their clinical translation.

Cell origin and microenvironment: The players of differentiation capacity in human mesenchymal stem cells

Mesenchymal stem cells (MSCs) have several important properties that make them desirable for regenerative medicine. These properties include immunomodulatory ability, growth factor production, and differentiation into various cell types. Despite extensive research and promising results in clinical trials, our understanding of MSC biology, their mechanism of action, and their targeted and routine use in clinics is limited. Differentiation of human MSCs (hMSCs) is a complex process influenced by various elements such as growth factors, pharmaceutical compounds, microRNAs, 3D scaffolds, and mechanical and electrical stimulation. Research has shown that different culture conditions can affect the differentiation potential of hMSCs obtained from multiple fetal and adult sources. Additionally, it seems that what affects the differentiation capacities of these cells is their secretory characteristics, which are influenced by the origin of the cells and the local microenvironment where the cells are located. The review can provide insights into the microenvironment-based mechanisms involved in MSC differentiation, which can be valuable for future therapeutic applications.

Recent advances in the application of engineered exosomes from mesenchymal stem cells for regenerative medicine

Exosomes, cell-derived vesicles produced by cells, are fascinating and drawing growing interest in biomedical exploration due to their exceptional properties. There is intriguing evidence that exosomes are involved in major biological processes, including diseases and regeneration. Exosomes from mesenchymal stem cells (MSCs) have shown promising outcomes in regenerative medicine. Numerous studies suggest that exosomes have several advantages over conventional synthetic nanocarriers, opening novel frontiers for innovative drug delivery. Regenerative medicine has demonstrated the profound therapeutic outcomes of engineered or loaded exosomes from MSCs. Different methods are being used to modify or/load exosomes. These exosomes can improve cell signaling pathways for bone and cartilage diseases, liver diseases, nerve tissues, kidney diseases, skin tissue, and cardiovascular diseases. Despite extensive research, clinical translation of these exosomes remains a challenge. The optimization of cargo loading methods, efficiency, physiological stability, and the isolation and characterization of exosomes present some challenges. The upcoming examination should include the development of large-scale, quality-controllable production approaches, the modification of drug loading approaches, and numerous in vivo investigations and clinical trials. Here, we provided an informative overview of the extracellular vesicles and modification/loading methods of exosomes. We discuss the last exosome research on regeneration disorders, highlighting the therapeutic applications of MSCs-derived exosomes. We also highlight future directions and challenges, underscoring the significance of addressing the main questions in the field.

Isolation, identification, and challenges of extracellular vesicles: emerging players in clinical applications

Extracellular vesicles (EVs) serve as critical mediators of intercellular communication, encompassing exosomes, microvesicles, and apoptotic vesicles that play significant roles in diverse physiological and pathological contexts. Numerous studies have demonstrated that EVs derived from mesenchymal stem cells (MSC-EVs) play a pivotal role in facilitating tissue and organ repair, alleviating inflammation and apoptosis, enhancing the proliferation of endogenous stem cells within tissues and organs, and modulating immune function-these functions have been extensively utilized in clinical applications. The precise classification, isolation, and identification of MSC-EVs are essential for their clinical applications. This article provides a comprehensive overview of the biological properties of EVs, emphasizing both their advantages and limitations in isolation and identification methodologies. Additionally, we summarize the protein markers associated with MSC-EVs, emphasizing their significance in the treatment of various diseases. Finally, this article addresses the current challenges and dilemmas in developing clinical applications for MSC-EVs, aiming to offer valuable insights for future research.

Exosomes from Human Periodontal Ligament Stem Cells Promote Differentiation of Osteoblast-like Cells and Bone Healing in Rat Calvarial Bone

Deep caries and severe periodontitis cause bone resorption in periodontal tissue, and severe bone resorption leads to tooth loss. Periodontal ligament stem cells (PDLSCs) are important for the healing of defective periodontal tissue. It is increasingly understood that healing of periodontal tissue is mediated through the secretion of trophic factors, particularly exosomes. This study investigated the effects of exosomes from human PDLSCs (HPDLSCs-Exo) on human osteoblast-like cells in vitro and on the healing of rat calvarial bone defects in vivo. HPDLSCs-Exo were isolated and characterized by their particle shape, size (133 ± 6.4 nm), and expression of surface markers (CD9, CD63, and CD81). In vitro results showed that HPDLSCs-Exo promoted the migration, mineralization, and expression of bone-related genes such as alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP2), osteocalcin (OCN), and osteopontin (OPN) in human osteoblast-like cells. Furthermore, in vivo results showed that more newly formed bone was observed in the HPDLSCs-Exo-treated group than in the non-treated group at the defect sites in rats. These results indicated that HPDLSCs-Exo could promote osteogenesis in vitro and in vivo, and this suggests that HPDLSCs-Exo may be an attractive treatment tool for bone healing in defective periodontal tissue.

Release of exosomes from injectable silk fibroin and alginate composite hydrogel for treatment of myocardial infarction

Myocardial infarction (MI) is considered as a significant cause of death globally. Exosomes (EXOs) are essential for intercellular communication and pathophysiology of several cardiovascular diseases. Nevertheless, the short half-life and rapid clearance of EXOs leads to a lack of therapeutic doses delivered to the lesioned area. Therefore, an injectable silk fibroin and alginate (SF/Alg) composite hydrogel was developed to bind folate receptor-targeted EXOs (FA-EXOs) derived from H9C2 cells for the therapy of myocardial injury following myocardial infarction-ischemia/reperfusion (MI-I/R). The resulting composite exhibits a variety of properties, including adjustable gelation kinetics, shear-thinning injectability, soft and dynamic stability that adapts to the heartbeat, and outstanding cytocompatibility. After injected into the damaged rat heart, administration of SF/Alg + FA-EXOs significantly enhanced cardiac function as demonstrated by improved ejection fraction, fractional shortening and decreased fibrosis area. The results of real-time PCR and immunofluorescence staining show a remarkable up-regulation in the expression of proteins (CD31) and genes (VWF and Serca2a) related to the heart. Conversely, expression of fibrosis-related genes (TGF-β1) decreased significantly. Therefore, the obtained SF/Alg + FA-EXOs system remarkably enhanced the intercellular interactions, promoted cell proliferation and angiogenesis, and achieved an outstanding therapeutic effect on MI.

Hypoxic bone marrow mesenchymal stem cell exosomes promote angiogenesis and enhance endometrial injury repair through the miR-424-5p-mediated DLL4/Notch signaling pathway

Background

Currently, bone marrow mesenchymal stem cells (BMSCs) have been reported to promote endometrial regeneration in rat models of mechanically injury-induced uterine adhesions (IUAs), but the therapeutic effects and mechanisms of hypoxic BMSC-derived exosomes on IUAs have not been elucidated.

Objective

To investigate the potential mechanism by which the BMSCS-derived exosomal miR-424-5p regulates IUA angiogenesis through the DLL4/Notch signaling pathway under hypoxic conditions and promotes endometrial injury repair.

Methods

The morphology of the exosomes was observed via transmission electron microscopy, and the expression of exosome markers (CD9, CD63, CD81, and HSP70) was detected via flow cytometry and Western blotting. The expression of angiogenesis-related genes (Ang1, Flk1, Vash1, and TSP1) was detected via RT‒qPCR, and the expression of DLL4/Notch signaling pathway-related proteins (DLL4, Notch1, and Notch2) was detected via Western blotting. Cell proliferation was detected by a CCK-8 assay, and angiogenesis was assessed via an angiogenesis assay. The expression of CD3 was detected by immunofluorescence. The endometrial lesions of IUA rats were observed via HE staining, and the expression of CD3 and VEGFA was detected via immunohistochemistry.

Results

Compared with those in exosomes from normoxic conditions, miR-424-5p was more highly expressed in the exosomes from hypoxic BMSCs. Compared with those in normoxic BMSC-derived exosomes, the proliferation and angiogenesis of HUVECs were significantly enhanced after treatment with hypoxic BMSC-derived exosomes, and these effects were weakened after inhibition of miR-424-5p. miR-424-5p can target and negatively regulate the expression of DLL4, promote the expression of the proangiogenic genes Ang1 and Flk1, and inhibit the expression of the antiangiogenic genes Vash1 and TSP1. The effect of miR-424-5p can be reversed by overexpression of DLL4. In IUA rats, treatment with hypoxic BMSC exosomes and the miR-424-5p mimic promoted angiogenesis and improved endometrial damage.

Conclusion

The hypoxic BMSC-derived exosomal miR-424-5p promoted angiogenesis and improved endometrial injury repair by regulating the DLL4/Notch signaling pathway, which provides a new idea for the treatment of IUAs.

Effects of HMGB1/TLR4 on secretion IL-10 and VEGF in human jaw bone-marrow mesenchymal stem cells

OBJECTIVE

We aimed to investigate the regulatory effects of HMGB1/TLR4 signaling pathway on the expression of IL-10 and VEGF in human bone marrow mesenchymal stem cells.

METHODOLOGY

Human JBMSCs were isolated and cultured. Then, HMGB1 was added into the JBMSCs culture medium, and the protein and mRNA expression levels of IL-10 and VEGF were assessed. Moreover, cells were pretreated with a specific TLR4 inhibitor (TAK-242), and the expression changes of IL-10 and VEGF were compared.

RESULTS

Compared with the control group, exposure to HMGB1 in human JBMSCs up-regulated TLR4, IL-10, and VEGF secretion at both protein and mRNA levels (P<0. 05). In addition, the increased expression of IL-10 and VEGF could be restrained in TAK-242 group compared with the HMGB1 group (P<0.05).

CONCLUSIONS

The results indicated that HMGB1 activate TLR4 signaling pathway in Human JBMSCs, which plays a regulatory role in cytokines expression.

Osteoporosis under psychological stress: mechanisms and therapeutics

Psychological stress has been associated with the onset of several diseases, including osteoporosis. However, the underlying pathogenic mechanism remains unknown, and effective therapeutic strategies are still unavailable. Growing evidence suggests that the sympathetic nervous system regulates bone homeostasis and vascular function under psychological stress, as well as the coupling of osteogenesis and angiogenesis in bone development, remodeling, and regeneration. Furthermore, extracellular vesicles (EVs), particularly mesenchymal stem cell extracellular vesicles (MSC-EVs), have emerged as prospecting therapies for stimulating angiogenesis and bone regeneration. We summarize the role of sympathetic regulation in bone homeostasis and vascular function in response to psychological stress and emphasize the relationship between vessels and bone. Finally, we suggest using MSC-EVs as a promising therapeutic method for treating osteoporosis in psychological stress.

Exosomes Derived from Quercetin-Treated Bone Marrow Derived Mesenchymal Stem Cells Inhibit the Progression of Osteoarthritis Through Delivering miR-124-3p to Chondrocytes

Osteoarthritis (OA) is a chronic disease characterized by the progressive loss of cartilage and failure of the diarrheal joint. Quercetin has been reported to attenuate the development of OA. Bone marrow derived mesenchymal stem cell (BMSC)-derived exosomes are involved in OA progression. However, the role of BMSC-derived exosomes in quercetin-mediated progression of OA remains unclear. Western blotting and RT-qPCR were used to assess protein and mRNA levels, respectively. CCK8 assay was performed to assess cell viability, and cell apoptosis was assessed using flow cytometry. A dual-luciferase assay was performed to assess the relationship between miR-124-3p and TRAF6 expression. Furthermore, in vivo experiments were performed to test the function of exosomes derived from Quercetin-treated BMSCs in OA patients. IL-1β significantly inhibited the viability of chondrocytes, whereas the conditioned medium of Quercetin-treated BMSCs (BMSCsQUE-CM) reversed this phenomenon through exosomes. IL-1β notably upregulated MMP13 and ADAMT5 and reduced the expression of COL2A1 in chondrocytes, which were rescued by BMSCsQUE-CM. The effects of BMSCsQUE-CM on these three proteins were reversed in the absence of exosomes. Exosomes can be transferred from BMSCs to chondrocytes, and exosomes derived from Quercetin-treated BMSCs (BMSCsQue-Exo) can reverse the apoptotic effects of IL-1β on chondrocytes. The level of miR-124-3p in BMSCs was significantly upregulated by quercetin, and miR-124-3p was enriched in BMSCsQue-Exo. TRAF6 was identified as a direct target of miR-124-3p, and BMSCsQue-Exo abolished the IL-1β-induced activation of MAPK/p38 and NF-κB signaling. Furthermore, BMSCsQue-Exo significantly attenuated OA progression in vivo. Exosomes derived from Quercetin-treated BMSCs inhibited OA progression through the upregulation of miR-124-3p.

Understanding exosomes: Part 3-therapeutic + diagnostic potential in dentistry

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 various diseases. Over 5000 publications are currently being published on this topic yearly, many of which in the dental space. This extensive review article is the first scoping review aimed at summarizing all therapeutic uses of exosomes in regenerative dentistry. A total of 944 articles were identified as using exosomes in the dental field for either their regenerative/therapeutic potential or for diagnostic purposes derived from the oral cavity. In total, 113 research articles were selected for their regenerative potential (102 in vitro, 60 in vivo, 50 studies included both). Therapeutic exosomes were most commonly derived from dental pulps, periodontal ligament cells, gingival fibroblasts, stem cells from exfoliated deciduous teeth, and the apical papilla which have all been shown to facilitate the regenerative potential of a number of tissues including bone, cementum, the periodontal ligament, nerves, aid in orthodontic tooth movement, and relieve temporomandibular joint disorders, among others. Results demonstrate that the use of exosomes led to positive outcomes in 100% of studies. In the bone field, exosomes were found to perform equally as well or better than rhBMP2 while significantly reducing inflammation. Periodontitis animal models were treated with simple gingival injections of exosomes and benefits were even observed when the exosomes were administered intravenously. Exosomes are much more stable than growth factors and were shown to be far more resistant against degradation by periodontal pathogens found routinely in a periodontitis environment. Comparative studies in the field of periodontal regeneration found better outcomes for exosomes even when compared to their native parent stem cells. In total 47 diagnostic studies revealed a role for salivary/crevicular fluid exosomes for the diagnosis of birth defects, cardiovascular disease, diabetes, gingival recession detection, gingivitis, irritable bowel syndrome, neurodegenerative disease, oral lichen planus, oral squamous cell carcinoma, oropharyngeal cancer detection, orthodontic root resorption, pancreatic cancer, periodontitis, peri-implantitis, Sjögren syndrome, and various systemic diseases. Hence, we characterize the exosomes as possessing "remarkable" potential, serving as a valuable tool for clinicians with significant advantages.

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

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

Exosomes derived from mesenchymal stromal cells promote bone regeneration by delivering miR-182-5p-inhibitor

Exosomes, small extracellular vesicles that function as a key regulator of cell-to-cell communication, are emerging as a promising candidate for bone regeneration. Here, we aimed to investigate the effect of exosomes from pre-differentiated human alveolar bone-derived bone marrow mesenchymal stromal cells (AB-BMSCs) carrying specific microRNAs on bone regeneration. Exosomes secreted from AB-BMSCs pre-differentiated for 0 and 7 days were cocultured with BMSCs in vitro to investigate their effect on the differentiation of the BMSCs. MiRNAs from AB-BMSCs at different stages of osteogenic differentiation were analyzed. BMSCs seeded on poly-L-lactic acid(PLLA) scaffolds were treated with miRNA antagonist-decorated exosomes to verify their effect on new bone regeneration. Exosomes pre-differentiated for 7 days effectively promoted the differentiation of BMSCs. Bioinformatic analysis revealed that miRNAs within the exosomes were differentially expressed, including the upregulation of osteogenic miRNAs (miR-3182, miR-1468) and downregulation of anti-osteogenic miRNAs (miR-182-5p, miR-335-3p, miR-382-5p), causing activation of the PI3K/Akt signaling pathway. The treatment of BMSC-seeded scaffolds with anti-miR-182-5p decorated exosomes demonstrated enhanced osteogenic differentiation and efficient formation of new bone. In conclusion, Osteogenic exosomes secreted from pre-differentiated AB-BMSCs were identified and the gene modification of exosomes provides great potential as a bone regeneration strategy. DATA AVAILABILITY STATEMENT: Data generated or analyzed in this paper partly are available in the GEO public data repository(http://www.ncbi.nlm.nih.gov/geo).

Extracellular vesicles: From bone development to regenerative orthopedics

Regenerative medicine aims to promote the replacement of tissues lost to damage or disease. While positive outcomes have been observed experimentally, challenges remain in their clinical translation. This has led to growing interest in applying extracellular vesicles (EVs) to augment or even replace existing approaches. Through the engineering of culture environments or direct/indirect manipulation of EVs themselves, multiple avenues have emerged to modulate EV production, targeting, and therapeutic potency. Drives to modulate release using material systems or functionalize implants for improved osseointegration have also led to outcomes that could have real-world impact. The purpose of this review is to highlight advantages in applying EVs for the treatment of skeletal defects, outlining the current state of the art in the field and emphasizing avenues for further investigation. Notably, the review identifies inconsistencies in EV nomenclature and outstanding challenges in defining a reproducible therapeutic dose. Challenges also remain in the scalable manufacture of a therapeutically potent and pure EV product, with a need to address scalable cell sources and optimal culture environments. Addressing these issues will be critical if we are to develop regenerative EV therapies that meet the demands of regulators and can be translated from bench to bedside.

SDF-1α promotes subchondral bone sclerosis and aggravates osteoarthritis by regulating the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells

BACKGROUND

Subchondral bone sclerosis is a major feature of osteoarthritis (OA), and bone marrow mesenchymal stem cells (BMSCs) are presumed to play an important role in subchondral bone sclerosis. Accumulating evidence has shown that stromal cell-derived factor-1α (SDF-1α) plays a key role in bone metabolism-related diseases, but its role in OA pathogenesis remains largely unknown. The purpose of this study was to explore the role of SDF-1α expressed on BMSCs in subchondral bone sclerosis in an OA model.

METHODS

In the present study, C57BL/6J mice were divided into the following three groups: the sham control, destabilization of the medial meniscus (DMM), and AMD3100-treated DMM (DMM + AMD3100) groups. The mice were sacrificed after 2 or 8 weeks, and samples were collected for histological and immunohistochemical analyses. OA severity was assessed by performing hematoxylin and eosin (HE) and safranin O-fast green staining. SDF-1α expression in the OA model was measured using an enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (q-PCR), and immunohistochemistry. Micro-CT was used to observe changes in subchondral bone in the OA model. CD44, CD90, RUNX2, and OCN expression in subchondral bone were measured using q-PCR and immunohistochemistry. In vitro, BMSCs were transfected with a recombinant lentivirus expressing SDF-1α, an empty vector (EV), or siRNA-SDF-1α. Western blot analysis, q-PCR, and immunofluorescence staining were used to confirm the successful transfection of BMSCs. The effect of SDF-1α on BMSC proliferation was evaluated by performing a CCK-8 assay and cell cycle analysis. The effect of SDF-1α on the osteogenic differentiation of BMSCs was assessed by performing alkaline phosphatase (ALP) and alizarin red S (ARS) staining. Cyclin D1, RUNX2 and OCN expression were measured using Western blot analysis, q-PCR, and immunofluorescence staining.

RESULTS

SDF-1α expression in the DMM-induced OA model increased. In the DMM + AMD3100 group, subchondral bone sclerosis was alleviated, OA was effectively relieved, and CD44, CD90, RUNX2, and OCN expression in subchondral bone was decreased. In vitro, high levels of SDF-1α promoted BMSC proliferation and increased osteogenic differentiation. Cyclin D1, RUNX2, and OCN expression increased.

CONCLUSION

The results of this study reveal a new molecular mechanism underlying the pathogenesis of OA. The targeted regulation of SDF-1α may be clinically effective in suppressing OA progression.

Engineering exosomes and biomaterial-assisted exosomes as therapeutic carriers for bone regeneration

Mesenchymal stem cell-based therapy has become an effective therapeutic approach for bone regeneration. However, there are still limitations in successful clinical translation. Recently, the secretome of mesenchymal stem cells, especially exosome, plays a critical role in promoting bone repair and regeneration. Exosomes are nanosized, lipid bilayer-enclosed structures carrying proteins, lipids, RNAs, metabolites, growth factors, and cytokines and have attracted great attention for their potential application in bone regenerative medicine. In addition, preconditioning of parental cells and exosome engineering can enhance the regenerative potential of exosomes for treating bone defects. Moreover, with recent advancements in various biomaterials to enhance the therapeutic functions of exosomes, biomaterial-assisted exosomes have become a promising strategy for bone regeneration. This review discusses different insights regarding the roles of exosomes in bone regeneration and summarizes the applications of engineering exosomes and biomaterial-assisted exosomes as safe and versatile bone regeneration agent delivery platforms. The current hurdles of transitioning exosomes from bench to bedside are also discussed.

MSC-Exos: Important active factor of bone regeneration

Bone defect and repair is a common but difficult problem in restorative and reconstructive surgery. Bone tissue defects of different sizes caused by different reasons bring functional limitations and cosmetic deformities to patients. Mesenchymal stem cells (MSC), a major hotspot in the field of regeneration in recent years, have been widely used in various studies on bone tissue regeneration. Numerous studies have shown that the bone regenerative effects of MSC can be achieved through exosome-delivered messages. Although its osteogenic mechanism is still unclear, it is clear that MSC-Exos can directly or indirectly support the action of bone regeneration. It can act directly on various cells associated with osteogenesis, or by carrying substances that affect cellular activators or the local internal environment in target cells, or it can achieve activation of the osteogenic framework by binding to materials. Therefore, this review aims to summarize the types and content of effective contents of MSC-Exos in bone regeneration, as well as recent advances in the currently commonly used methods to enable the binding of MSC-Exos to the framework and to conclude that MSC-Exos is effective in promoting osteogenesis.

Nanotechnology-Inspired Extracellular Vesicles Theranostics for Diagnosis and Therapy of Central Nervous System Diseases

Shuttling various bioactive substances across the blood-brain barrier (BBB) bidirectionally, extracellular vesicles (EVs) have been opening new frontiers for the diagnosis and therapy of central nervous system (CNS) diseases. However, clinical translation of EV-based theranostics remains challenging due to difficulties in effective EV engineering for superior imaging/therapeutic potential, ultrasensitive EV detection for small sample volume, as well as scale-up and standardized EV production. In the past decade, continuous advancement in nanotechnology provided extensive concepts and strategies for EV engineering and analysis, which inspired the application of EVs for CNS diseases. Here we will review the existing types of EV-nanomaterial hybrid systems with improved diagnostic and therapeutic efficacy for CNS diseases. A summary of recent progress in the incorporation of nanomaterials and nanostructures in EV production, separation, and analysis will also be provided. Moreover, the convergence between nanotechnology and microfluidics for integrated EV engineering and liquid biopsy of CNS diseases will be discussed.

Exosomal let-7f-5p derived from mineralized osteoblasts promotes the angiogenesis of endothelial cells via the DUSP1/Erk1/2 signaling pathway

Blood vessel formation is the prerequisite for the survival and growth of tissue-engineered bone. Mineralized osteoblasts (MOBs) have been shown to regulate angiogenesis through the secretion of exosomes containing various pro-angiogenic factors. However, whether the mineralized osteoblast-derived exosomes (MOB-Exos) containing let-7f-5p can regulate the angiogenesis of endothelial cells (ECs) is still unknown. In this study, the angiogenic capabilities of ECs respectively treated with MOB-Exos, let-7f-5p mimicked MOB-Exos (miR mimic group), and let-7f-5p inhibited MOB-Exos (miR inhibitor group) were compared through in vitro and in vivo studies. Moreover, the potential mechanism of MOB-Exo let-7f-5p regulating angiogenesis was explored by verifying the role of the Erk1/2 signaling pathway and target gene DUSP1. The results showed that MOB-Exos could significantly promote the angiogenesis of ECs, which could be enhanced by mimicked exosomal let-7f-5p and attenuated by inhibited exosomal let-7f-5p. Let-7f-5p could suppress the luciferase activity of wide-type DUSP1, and the mutation of DUSP1 could abrogate the repressive ability of let-7f-5p. Furthermore, the expression of DUSP1 exhibited a reversed trend to that of pErk1/2. The expression of pErk1/2 was significantly higher in the miR mimic group and lower in the miR inhibitor group than that in the MOB-Exos group, while inhibition of pErk1/2 could partly impair the angiogenic capabilities of ECs. In conclusion, we concluded that exosomal let-7f-5p derived from MOBs could promote the angiogenesis of ECs via activating the DUSP1/Erk1/2 signaling pathway, which might be a promising target for promoting the angiogenesis of tissue-engineered bone.

Exosomes Derived from Runx2-Overexpressing BMSCs Enhance Cartilage Tissue Regeneration and Prevent Osteoarthritis of the Knee in a Rabbit Model

Objectives

Osteoarthritis is the leading disease of joints worldwide. Osteoarthritis may be treated by exosomes derived from Runx2-overexpressed bone marrow mesenchymal stem cells (R-BMSCs-Exos). R-BMSCs-Exos would promote the proliferation, migration, and phenotypic maintenance of articular chondrocytes.

Methods

BMSCs were transfected with and without Runx2. Exosomes derived from BMSCs and R-BMSCs (BMSCs-Exos and R-BMSCs-Exos) were isolated and identified. Proliferation, migration, and phenotypic maintenance were determined in vitro and compared between groups. The mechanism for activation of Yes-associated protein (YAP) was investigated using small interfering RNA (siRNA). The exosomes' preventive role was determined in vivo using Masson trichrome and immunohistochemical staining.

Results

R-BMSCs-Exos enhance the proliferation, migration, and phenotypic maintenance of articular chondrocytes based on the YAP being activated. R-BMSCs-Exos prevent knee osteoarthritis as studied in vivo through a rabbit model.

Conclusions

Findings emphasize the efficacy of R-BMSCs-Exos in preventing osteoarthritis. Potential source of exosomes is sorted out for the advantages and shortcomings. The exosomes are then modified based on the molecular mechanisms to address their limitations. Such exosomes derived from modified cells have the role in future therapeutics.

Potential of extracellular space for tissue regeneration in dentistry

With the proven relationship between oral and general health and the growing aging population, it is pivotal to provide accessible therapeutic approaches to regenerate oral tissues and restore clinical function. However, despite sharing many core concepts with medicine, dentistry has fallen behind the progress in precision medicine and regenerative treatments. Stem cell therapies are a promising avenue for tissue regeneration, however, ethical, safety and cost issues may limit their clinical use. With the significance of paracrine signalling in stem cell and tissue regeneration, extracellular space comprising of the cell secretome, and the extracellular matrix can serve as a potent source for tissue regeneration. Extravesicles are secreted and naturally occurring vesicles with biologically active cargo that can be harvested from the extracellular space. These vesicles have shown great potential as disease biomarkers and can be used in regenerative medicine. As a cell free therapy, secretome and extracellular vesicles can be stored and transferred easily and pose less ethical and safety risks in clinical application. Since there are currently many reviews on the secretome and the biogenesis, characterization and function of extracellular vesicles, here we look at the therapeutic potential of extracellular space to drive oral tissue regeneration and the current state of the field in comparison to regenerative medicine.

Effects of BMSC-Derived EVs on Bone Metabolism

Extracellular vesicles (EVs) are small membrane vesicles that can be secreted by most cells. EVs can be released into the extracellular environment through exocytosis, transporting endogenous cargo (proteins, lipids, RNAs, etc.) to target cells and thereby triggering the release of these biomolecules and participating in various physiological and pathological processes. Among them, EVs derived from bone marrow mesenchymal stem cells (BMSC-EVs) have similar therapeutic effects to BMSCs, including repairing damaged tissues, inhibiting macrophage polarization and promoting angiogenesis. In addition, BMSC-EVs, as efficient and feasible natural nanocarriers for drug delivery, have the advantages of low immunogenicity, no ethical controversy, good stability and easy storage, thus providing a promising therapeutic strategy for many diseases. In particular, BMSC-EVs show great potential in the treatment of bone metabolic diseases. This article reviews the mechanism of BMSC-EVs in bone formation and bone resorption, which provides new insights for future research on therapeutic strategies for bone metabolic diseases.

Bone marrow mesenchymal stem cells-derived exosomes suppress miRNA-5189-3p to increase fibroblast-like synoviocyte apoptosis via the BATF2/JAK2/STAT3 signaling pathway

Ankylosing spondylitis (AS) is characterized by inflammation of the sacroiliac joint and the attachment point of the spine. Herein, we aimed to investigate the effect of bone marrow mesenchymal stem cells (BMSCs)-derived exosomes on apoptosis of fibroblast-like synoviocytes (FLSs) and explored its molecular mechanism. Exosomes were isolated from BMSCs and verified by transmission electron microscope and nanoparticle tracking analysis. FLSs were isolated and co-incubated with BMSC exosomes. Cell apoptosis was assessed using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling analysis and flow cytometry. The results showed that BMSC exosomes increased apoptosis of FLSs. MiR-5189-3p was downregulated, while basic leucine zipper transcription factor ATF-like 2 (BATF2) was upregulated in FLSs by treatment of BMSC exosomes. As a direct target of miR-5189-3p, BATF2 inactivates the JAK2/STAT3 pathway. MiR-5189-3p suppressed apoptosis of FLSs and BATF2 exerted an opposite effect. In conclusion, BMSCs-derived exosomes suppress miR-5189-3p to facilitate the apoptosis of FLSs via the BATF2/JAK2/STAT3 signaling pathway, which facilitates the understanding of the therapeutic effect of BMSCs on AS and the underlying molecular mechanism.

Educating EVs to Improve Bone Regeneration: Getting Closer to the Clinic

The incidence of bone-related disorders is continuously growing as the aging of the population in developing countries continues to increase. Although therapeutic interventions for bone regeneration exist, their effectiveness is questioned, especially under certain circumstances, such as critical size defects. This gap of curative options has led to the search for new and more effective therapeutic approaches for bone regeneration; among them, the possibility of using extracellular vesicles (EVs) is gaining ground. EVs are secreted, biocompatible, nano-sized vesicles that play a pivotal role as messengers between donor and target cells, mediated by their specific cargo. Evidence shows that bone-relevant cells secrete osteoanabolic EVs, whose functionality can be further improved by several strategies. This, together with the low immunogenicity of EVs and their storage advantages, make them attractive candidates for clinical prospects in bone regeneration. However, before EVs reach clinical translation, a number of concerns should be addressed. Unraveling the EVs’ mode of action in bone regeneration is one of them; the molecular mediators driving their osteoanabolic effects in acceptor cells are now beginning to be uncovered. Increasing the functional and bone targeting abilities of EVs are also matters of intense research. Here, we summarize the cell sources offering osteoanabolic EVs, and the current knowledge about the molecular cargos that mediate bone regeneration. Moreover, we discuss strategies under development to improve the osteoanabolic and bone-targeting potential of EVs.

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.

Bone mesenchymal stem cells-derived miR-223-3p-containing exosomes ameliorate lipopolysaccharide-induced acute uterine injury via interacting with endothelial progenitor cells

Bone mesenchymal stem cells (BMSCs) have been used for the treatment of acute uterine injury (AUI)-induced intrauterine adhesion (IUA) via interacting with the endothelial progenitor cells (EPCs), and BMSCs-derived exosomes (BMSCs-exo) may be the key regulators for this process. However, the underlying mechanisms have not been studied. Based on the existed literatures, lipopolysaccharide (LPS) was used to induce AUI in mice models and EPCs to mimic the realistic pathogenesis of IUA in vivo and in vitro. Our data suggested that LPS induced apoptotic and pyroptotic cell death in mice uterine horn tissues and EPCs, and the clinical data supported that increased levels of pro-inflammatory cytokines IL-18 and IL-1β were also observed in IUA patients' serum samples, and silencing of NLRP3 rescued cell viability in LPS-treated EPCs. Next, the LPS-treated EPCs were respectively co-cultured with BMSCs in the Transwell system and BMSCs-exo, and the results hinted that both BMSCs and BMSCs-exo reversed the promoting effects of LPS treatment-induced cell death in EPCs. Then, we screened out miR-223-3p, as the upstream regulator for NLRP3, was enriched in BMSCs-exo, and BMSCs-exo inactivated NLRP3-mediated cell pyroptosis in EPCs via delivering miR-223-3p. Interestingly, upregulation of miR-223-3p attenuated LPS-induced cell death in EPCs. Collectively, we concluded that BMSCs-exo upregulated miR-223-3p to degrade NLRP3 in EPCs, which further reversed the cytotoxic effects of LPS treatment on EPCs to ameliorate LPS-induced AUI.

Capturing Magnesium Ions via Microfluidic Hydrogel Microspheres for Promoting Cancellous Bone Regeneration

Metal ions are important trace elements in the human body, which directly affect the human metabolism and the regeneration of damaged tissues. For instance, the advanced combination of magnesium ions (Mg²⁺) and bone repair materials make the composite materials have the function of promoting vascular repair and enhancing the adhesion of osteoblasts. Herein, inspired by magnets to attract metals, we utilized the coordination reaction of metal ion ligand to construct a bisphosphonate-functionalized injectable hydrogel microsphere (GelMA-BP-Mg) which could promote cancellous bone reconstruction of osteoporotic bone defect via capturing Mg²⁺. By grafting bisphosphonate (BP) on GelMA microspheres, GelMA-BP microspheres could produce powerful Mg²⁺ capture ability and sustained release performance through coordination reaction, while sustained release BP has bone-targeting properties. In the injectable GelMA-BP-Mg microsphere system, the atomic percentage of captured Mg²⁺ was 0.6%, and the captured Mg²⁺ could be effectively released for 18 days. These proved that the composite microspheres could effectively capture Mg²⁺ and provided the basis for the composite microspheres to activate osteoblasts and endothelial cells and inhibit osteoclasts. Both in vivo and in vitro experimental results revealed that the magnet-inspired Mg²⁺-capturing composite microspheres are beneficial to osteogenesis and angiogenesis by stimulating osteoblasts and endothelial cells while restraining osteoclasts, and ultimately effectively promote cancellous bone regeneration. This study could provide some meaningful conceptions for the treatment of osteoporotic bone defects on the basis of metal ions.

Effect and mechanism of propranolol on promoting osteogenic differentiation and early implant osseointegration

The present study aimed to investigate the effect of β‑receptor blocker propranolol on early osseointegration of pure titanium implants and the underlying molecular regulatory mechanisms. An implant osseointegration model using the tibial metaphysis of New Zealand rabbits was established. The rabbits were divided into control and low‑, medium‑ and high‑dose propranolol groups. The formation of implant osseointegration was detected by X‑ray scanning. Mesenchymal stem cells (MSCs) and osteoblasts (OBs) were isolated and cultured in vitro, isoproterenol was supplemented to simulate sympathetic action and propranolol was subsequently administrated. The effect of propranolol on cell proliferation and osteogenic differentiation were assessed by EdU, flow cytometry, alizarin red staining and alkaline phosphatase (ALP) detection. The expression levels of bone morphogenetic protein (BMP)2, RUNX family transcription factor (RunX)2, collagen (COL)‑1, osteocalcin (OCN) and β2‑adrenergic receptor (AR) were detected by immunofluorescence, reverse transcription‑quantitative PCR and western blot assay. Propranolol effectively promoted implant osseointegration in vivo, facilitated proliferation of OBs, inhibited proliferation of MSCs and enhanced osteogenic differentiation of OBs and MSCs. The calcium content and ALP activity of cells treated with propranolol were markedly higher than in the control group. Propranolol also elevated mRNA and protein expression levels of BMP2, RunX2, COL‑1 and OCN in tissue and cells, and decreased the expression of β2‑AR. The present study demonstrated that the β‑receptor blocker propranolol promoted osteogenic differentiation of OBs and MSCs and enhanced implant osseointegration. The present study provided a novel insight into the application and regulatory mechanisms of propranolol.

Extracellular vesicles for tissue repair and regeneration: Evidence, challenges and opportunities

Extracellular vesicles (EVs) are biological nanoparticles naturally secreted by cells, acting as delivery vehicles for molecular messages. During the last decade, EVs have been assigned multiple functions that have established their potential as therapeutic mediators for a variety of diseases and conditions. In this review paper, we report on the potential of EVs in tissue repair and regeneration. The regenerative properties that have been associated with EVs are explored, detailing the molecular cargo they carry that is capable of mediating such effects, the signaling cascades triggered in target cells and the functional outcome achieved. EV interactions and biodistribution in vivo that influence their regenerative effects are also described, particularly upon administration in combination with biomaterials. Finally, we review the progress that has been made for the successful implementation of EV regenerative therapies in a clinical setting.

Osteogenic and Angiogenic Potency of VEGF165-Transfected Canine Bone Marrow Mesenchymal Cells Combined with Coral Hydroxyapatite in Vitro

BACKGROUND

To explore the osteogenic and angiogenic potential of human vascular endothelial growth factor 165 (hVEGF165) gene-transfected canine bone marrow mesenchymal stem cells (BMSCs) combined with coral hydroxyapatite (CHA) scaffold.

METHODS

We constructed a lentiviral vector and transfected canine BMSCs with the best multiplicity of infection. Osteogenesis was induced in the transfected groups (GFP-BMSCs group and hVEGF-BMSCs group) and non-transfected group (BMSCs group), followed by the evaluation of alkaline phosphatase (ALP) activity and alizarin red S staining. Cells from the three groups were co-cultured with CHA granules, respectively to obtain the tissue-engineered bone. MTT assay and fluorescence microscopy were employed to assess cell proliferation and adhesion. The expression of osteogenic and angiogenic related genes and proteins were evaluated at 7, 14, 21, and 28 days post osteoinduction in cell culture alone and cell co-culture with CHA, respectively using RT-PCR and ELISA.

RESULTS

The hVEGF165 gene was transfected into BMSCs successfully. Higher ALP activity and more calcified nodules were found in the hVEGF-BMSCs group than in the control groups (p < 0.001). Cells attached and proliferated in CHA particles. Both cells cultured alone and cells co-culture with CHA expressed more osteogenic and angiogenic related genes and proteins in the hVEGF-BMSCs group compared to the GFP-BMSCs and BMSCs groups (p < 0.05).

CONCLUSION

High expression of hVEGF165 in BMSCs potentially promote the osteogenic potential of BMSCs, and synergically drive the expression of other osteogenic and angiogenic factors. hVEGF-BMSCs co-cultured with CHA expressed more osteogenic and angiogenic related factors, creating a favorable microenvironment for osteogenesis and angiogenesis. Also, the findings have allowed for the construction of a CHA-hVEGF-BMSCs tissue-engineered bone.

Mesenchymal stromal cell-derived extracellular vesicles for bone regeneration therapy

Purpose

To analyze preclinical bone regeneration studies employing mesenchymal stromal cell (MSC)- derived extracellular vesicles (EVs) and highlight any commonalities in EV biomarker expression, miRNA cargo(s) or pathway activation that will aid in understanding the underlying therapeutic mechanisms.

Methods

Articles employing EVs derived from either MSCs or MSC-like osteogenic stromal cells in preclinical bone regeneration studies are included in this review.

Results

EVs derived from a variety of MSC types were able to successfully induce bone formation in preclinical models. Many studies failed to perform in-depth EV characterization. The studies with detailed EV characterization data report very different miRNA cargos, even in EVs isolated from the same species and cell types. Few preclinical studies have analyzed the underlying mechanisms of MSC-EV therapeutic action.

Conclusion

There is a critical need for mechanistic preclinical studies with thorough EV characterization to determine the best therapeutic MSC-EV source for bone regeneration therapies. Issues including controlled EV delivery, large scale production, and proper storage also need to be addressed before EV-based bone regeneration therapies can be translated for clinical bone repair.

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EVs from different MSC sources successfully regenerate bone in preclinical models.

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Studies were reviewed to find commonalities in EV cargo(s)/pathways activated in MSC-EV-based bone regeneration therapies.

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Issues that need to be overcome to enable clinical translation of EV-based therapies were addressed.

Bone Marrow Mesenchymal Stem Cells-Derived Exosomal MicroRNA-150-3p Promotes Osteoblast Proliferation and Differentiation in Osteoporosis

At present, much more studies have focused on the role of microRNAs in osteoporosis, but the more specific role of microRNA-150-3p (miR-150-3p) in osteoporosis still needs full exploration. We aim at investigating the role of miR-150-3p in osteoporosis and at exploring the related mechanisms. Bone marrow mesenchymal stem cells (BMSCs) were cultured, from which exosomes were isolated. Osteoporosis models were established by ovariectomy and injected with transfected BMSCs exosomes. Bone formation markers in serum, histopathological changes and miR-150-3p, runt-related transcription factor 2 (Runx2) and Osterix expression, and osteoblast apoptosis in femoral tissues were detected. Osteoblasts were isolated and co-cultured with the transfected BMSCs-derived exosomes. Osteoblast proliferation, cell differentiation, and apoptosis, along with miR-150-3p, Runx2, and Osterix expression in osteoblasts were detected. In vivo experiment demonstrated that miR-150-3p, Runx2, and Osterix expression was decreased whereas bone formation markers were decreased in osteoporosis. BMSCs exosomes attenuated osteoporosis, which was further improved by upregulated miR-150-3p in exosomes whereas it was impaired by downregulated miR-150-3p in exosomes. In vitro experiments declared decreased miR-150-3p, Runx2, and Osterix expression; suppressed proliferation; and encouraged apoptosis in osteoblasts in osteoporosis. BMSCs exosomes promoted osteoblast proliferation and differentiation and inhibited apoptosis, which was strengthened by raised exosomal miR-150-3p whereas it was disrupted by inhibited exosomal miR-150-3p. Our study elucidates that exosomal miR-150-3p promotes osteoblast proliferation and differentiation in osteoporosis and provides a new clue for the treatment of patients with osteoporosis.

Exosome-Derived Noncoding RNAs as a Promising Treatment of Bone Regeneration

The reconstruction of large bone defects remains a crucial challenge in orthopedic surgery. The current treatments including autologous and allogenic bone grafting and bioactive materials have their respective drawbacks. While mesenchymal stem cell (MSC) therapy may address these limitations, growing researches have demonstrated that the effectiveness of MSC therapy depends on paracrine factors, particularly exosomes. This aroused great focus on the exosome-based cell-free therapy in the treatment of bone defects. Exosomes can transfer various cargoes, and noncoding RNAs are the most widely studied cargo through which exosomes exert their ability of osteoinduction. Here, we review the research status of the exosome-derived noncoding RNAs in bone regeneration, the potential application of exosomes, and the existing challenges.

Extracellular vesicles in bone and periodontal regeneration: current and potential therapeutic applications

Oral mesenchymal stem cells (MSCs) and their secretomes are considered important factors in the field of medical tissue engineering and cell free biotherapy due to their ease of access, differentiation potential, and successful therapeutic outcomes. Extracellular vesicles (EVs) and the conditioned medium (CM) from MSCs are gaining more attraction as an alternative to cell-based therapies due to the less ethical issues involved, and their easier acquisition, preservation, long term storage, sterilization, and packaging. Bone and periodontal regenerative ability of EVs and CM have been the focus of some recent studies. In this review, we looked through currently available literature regarding MSCs' EVs or conditioned medium and their general characteristics, function, and regenerative potentials. We will also review the novel applications in regenerating bone and periodontal defects.

TGF-β1-containing exosomes derived from bone marrow mesenchymal stem cells promote proliferation, migration and fibrotic activity in rotator cuff tenocytes

Objective

This study aimed to investigate effects of TGF-β1-containing exosomes derived from bone marrow mesenchymal stem cells (BMSC) on cell function of rotator cuff tenocytes and its implication to rotator cuff tear.

Methods

The primary BMSC and rotator cuff tenocytes were extracted and cultured. Identification of BMSC were performed by observing cell morphology and measurement of surface biomarkers by flow cytometry. BMSC-derived exosomes were extracted and identified by using electron microscopy, nanoparticle-tracking analysis (NTA) and western blotting. Cell proliferation and cell cycle were measured by CCK-8 assay and flow cytometry assay, respectively. Transwell assay was used for detection of tenocytes migration. The fibrotic activity of tenocytes was determined via qPCR and western blotting assays.

Results

BMSC and BMSC-derived exosomes were successfully extracted. Treatment of BMSC-derived exosomes or TGF-β1 promoted cell proliferation, migration and increased cell ratio of (S + G2/M) phases in tenocytes, as well as enhanced the expression levels of fibrotic activity associated proteins. However, inhibition of TGF-β1 by transfection of sh-TGF-β1 or treatment of TGFβR I/II inhibitor partially reversed the impact of BMSC-derived exosomes on tenocytes function.

Conclusion

Taken together, TGF-β1-containing exosomes derived from BMSC promoted proliferation, migration and fibrotic activity in rotator cuff tenocytes, providing a new direction for treatment of rotator cuff tendon healing.

Mesenchymal stem cell exosomes in bone regenerative strategies-a systematic review of preclinical studies

The ability of bone for regeneration has long been recognized. However, once beyond a critical size, spontaneous regeneration of bone is limited. Several studies have focused on enhancing bone regeneration by applying mesenchymal stromal/stem cells (MSCs) in the treatment strategies. Despite the therapeutic efficacy of MSCs in bone regeneration, cell-based therapies are impeded by several challenges in maintaining the optimal cell potency and viability during expansion, storage, and final delivery to patients. Recently, there has been a paradigm shift in therapeutic mechanism of MSCs in tissue repair from one based on cellular differentiation and replacement to one based on secretion and paracrine signaling. Among the broad spectrum of trophic factors, extracellular vesicles ​particularly the exosomes have been reported to be therapeutically efficacious in several injury/disease indications, including bone defects and diseases. The current systematic review aims to summarize the results of the existing animal studies which were conducted to evaluate the therapeutic efficacy of MSC exosomes for bone regeneration. Following the Preferred Reporting Items for Systematic Reviews and Meta-analysis ​guidelines, the PubMed and The Cochrane Library database were searched for relevant controlled preclinical animal studies. A total of 23 studies were identified, with the total sample size being 690 rats or mice and 38 rabbits. Generally, MSC exosomes were found to be efficacious for bone regeneration in animal models of bone defects and diseases such as osteonecrosis and osteoporosis. In these studies, MSC exosomes promoted new bone formation with supporting vasculature ​and displayed improved morphological, biomechanical, and histological outcomes, coupled with positive effects on cell survival, proliferation, and migration, osteogenesis, and angiogenesis. Unclear-to-low risk in bias and incomplete reporting in the primary studies highlighted the need for standardization in outcome measurements and reporting. Further studies in large animal models to establish the safety and efficacy would provide useful information on guiding the design of clinical trials.

MiR-596 inhibits osteoblastic differentiation and cell proliferation by targeting Smad3 in steroid-induced osteonecrosis of femoral head

Background

It is reported that miR-596 has a potential diagnostic value for non-traumatic osteonecrosis of the femoral head (NOFH), but its underlying mechanisms in NOFH is unclear.

Methods

The expression of miR-596 and Smad3 was detected by western blot and quantitative real-time PCR. The relationship between the two molecules was explored using Dual-Luciferase Reporter Assay. Glucocorticoid (GC)—dexamethasone, was used to induce bone marrow mesenchymal stem cell (BMSC) osteogenic differentiation, and the effects of miR-596 on BMSC osteogenic differentiation and proliferation were determined.

Results

MiR-596 expression was upregulated, while Smad3 expression was inhibited in the bone marrow samples of patients with steroid-induced osteonecrosis of femoral head (SANFH). Overexpression of miR-596 inhibited the proliferation and osteogenic differentiation of BMSCs induced by GC. Meanwhile, the opposite results were observed in the miR-596 inhibitor group. In addition, Smad3 was a target gene of miR-596, and negatively regulated by miR-596. The promotion effect of the miR-596 inhibitor on BMSC proliferation and osteogenic differentiation was reversed by si-Smad3.

Conclusion

MiR-596 can suppress GC-BMSC osteoblastic differentiation and proliferation by regulating Smad3 expression.

Exosomes derived from umbilical cord mesenchymal stem cells in mechanical environment show improved osteochondral activity via upregulation of LncRNA H19

Background

Exosomes derived from stem cells have been demonstrated to be good candidates for the treatment of osteochondral injury. Our previous studies have demonstrated that mechanical stimulation could be crucial for the secretion of exosomes derived from umbilical cord mesenchymal stem cells (U-MSCs). Therefore, we explore whether mechanical stimulation caused by a rotary cell culture system (RCCS) has a beneficial effect on exosome yield and biological function.

Methods

U-MSCs were subjected to an RCCS at different rotational speeds and exosomes were characterised by transmission electron microscopy, nanoparticle tracking analysis and western blotting. small-interfering RNAs of Rab27a (siRNA-Rab27a) was used to reduce exosome production. Quantitative real-time PCR (qRT-PCR) was used to detect the expression of mechanically sensitive long non-coding RNA H19 (LncRNA H19). The effects of exosomes on chondrocyte proliferation were examined using cell counting kit-8 (CCK-8), toluidine blue staining and a series of related genes. Annexin V-FITC and PI (V-FITC/PI) flow cytometry was used to detect the effect of exosomes on the inhibition of chondrocyte apoptosis. Macroscopic evaluation, MRI quantification and immunohistochemical staining were conducted to investigate the in vivo effects of exosomal LncRNA H19 through SD rat cartilage defect models.

Results

RCCS significantly promoted exosome production at 36 rpm/min within 196 h. Mechanical stimulation was able to increase the expression level of exosomes. The exosomal LncRNA H19 was found to promote chondrocyte proliferation and matrix synthesis and inhibit apoptosis in vitro. Chondral regeneration activity was lost in LncRNA H19-defective exosomes. The injection of exosomal LncRNA H19 in vivo resulted in improved macroscopic assessment, MRI quantification and histological analysis. Moreover, exosomal LncRNA H19 was able to relieve pain levels during the early stages of cartilage repair in an animal experiment.

Conclusion

Our findings confirmed that mechanical stimulation can enhance exosome yield as well as biological function for the repair of cartilage defects. The underlying mechanism may be related to the high expression of LncRNA H19 in exosomes. The translational potential of this article: This study provides a theoretical support of optimizing exosome production. It advances the yield of mesenchymal stem cell exosome and facilitate the clinical application to repair of osteochondral damage.