Microarray analysis of circRNAs sequencing profile in exosomes derived from bone marrow mesenchymal stem cells in postmenopausal osteoporosis patients

MIR155HG suppresses the osteogenic differentiation of bone marrow mesenchymal stem cells through regulating miR-155-5p and DKK1 expression

BACKGROUND

Increasing evidence has demonstrated that non-coding RNAs, including the lncRNA MIR155HG, are involved in the pathogenesis of postmenopausal osteoporosis (PMOP). In the current study, we studied MIR155HG function in regulation of osteogenic differentiation and tried to reveal the underlying mechanisms.

METHODS

Forty blood samples taken from 20 PMOP patients (PMOP group) and 20 postmenopausal individuals without osteoporosis (control group) were used to compare the contents of MIR155HG and miR-155-5p via RT-PCR. Alizarin red S staining and ALP staining were used to evaluate the osteogenic differentiation potential of bone marrow mesenchymal stem cells (BMSCs).

RESULTS

Elevated levels of MIR155HG and miR-155-5p were observed in the blood samples of the PMOP group. Upregulation of MIR155HG resulted in decreased expression of OPN, OSX, ALP, RUNX2 and β-catenin but increased DKK1 expression, together with decreased Alizarin red S + and ALP + staining areas. However, downregulation of DKK1 did not obviously change the above indices induced by MIR155HG upregulation. Further experiments revealed that MIR155HG caused an increase in the expression of miR-155-5p, which also serves as an inhibitor of the osteogenic differentiation of BMSCs through binding to β-catenin. Consistent with DKK1 knockdown, downregulation of miR-155-5p only also did not obviously reverse the repressive effect of MIR155HG on osteoblastic differentiation, but downregulation of DKK1 and miR-155-5p synchronously restored the osteogenic differentiation ability of BMSCs suppressed by MIR155HG overexpression.

CONCLUSION

MIR155HG suppressed the osteoblastic differentiation of BMSCs by regulating miR-155-5p and DKK1 expression. Either inhibition of miR-155-5p and DKK1 or direct suppression of MIR155HG may be effective approaches for treating PMOP.

Circular RNA circSTX12 regulates osteo-adipogenic balance and proliferation of BMSCs in senile osteoporosis

Increased adipogenic differentiation and decreased osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) along with slow self-renewal are pivotal causes for decreased bone formation in senile osteoporosis. Circular RNAs (circRNAs) play important roles in cell proliferation and differentiation, and are closely related to osteoporosis. Whether circRNAs orchestrate the adipo-osteogenic balance and the proliferation of BMSCs in osteoporosis remains unclear. We found in this study that circSTX12 was abnormally upregulated in bone sections from osteoporosis patients and in BMSCs from aged mice, as well as in later-generation human BMSCs in culture. Knockdown of circSTX12 in BMSCs resulted in enhanced osteogenesis, decreased adipogenesis, and increased proliferation capacity; circSTX12 overexpression had the opposite effect. RNA pull-down and mass spectrometry revealed the interactions between circSTX12 with CBL and LMO7. At the molecular level, circSTX12 regulated cell fate in BMSCs by competitively binding to CBL, reducing the ubiquitination-mediated degradation of MST1 and thereby activating the Hippo pathway, a key regulator of adipo-osteogenic balance. Knockdown of circSTX12 promoted the nuclear localization of YAP. In addition, our findings suggest that LMO7 mediates circSTX12-induced BMSCs proliferation by regulating the transcription of CCNA2, CCNH, and CCND1. In vivo, injection of antisense oligonucleotides (ASOs) to knockdown circSTX12 promoted bone formation in aged mice. Our results provide evidence for circSTX12 as a regulator of adipo-osteogenic differentiation and proliferation of BMSCs through binding to CBL and LMO7, respectively. Targeting circSTX12 may be a novel approach for osteoporosis treatment.

Regulatory role of miR-128-2-5p in serum exosomes on COL6A2 expression and postmenopausal osteoporosis

This study investigates the influence of miR-128-2-5p within serum-derived exosomes (Exos) on COL6A2 expression and its implications in postmenopausal osteoporosis (POMP). Utilizing bioinformatics analysis, we identified 1317 differentially expressed genes (DEGs), primarily enriched in the focal adhesion pathway-a critical regulator of osteoblast adhesion. A significant gene, COL6A2, emerged as notably downregulated in POMP, possessing potential as a diagnostic marker. Predictive analysis linked the upstream miRNA miR-128-2-5p, highly enriched in Exos, with the regulation of COL6A2. Experimentally, Exos from POMP patients demonstrated elevated miR-128-2-5p levels, which inhibited COL6A2 expression in vitro, reducing osteoblast adhesion and exacerbating osteoporotic conditions. These findings highlight the pivotal role of exosomal miR-128-2-5p in bone metabolism, suggesting a novel molecular mechanism and a potential therapeutic target in POMP.

Perspectives of exosomal ncRNAs in the treatment of bone metabolic diseases: Focusing on osteoporosis, osteoarthritis, and rheumatoid arthritis

Bone metabolic disorders, constituting a group of prevalent and grave conditions, currently have a scarcity of therapeutic alternatives. Over the recent past, exosomes have been at the forefront of research interest, owing to their nanoparticulate nature and potential for therapeutic intervention. ncRNAs are a class of heterogeneous transcripts that they lack protein-encoding capacity, yet they can modulate the expression of other genes through multiple mechanisms. Mounting evidence underscores the intricate role of exosomes as ncRNAs couriers implicated in the pathogenesis of bone metabolic disorders. In this review, we endeavor to elucidate recent insights into the roles of three ncRNAs - miRNAs, lncRNAs, and circRNAs - in bone metabolic ailments such as osteoporosis, osteoarthritis, and rheumatoid arthritis. Additionally, we examine the viability of exosomal ncRNAs as innovative, cell-free modalities in the diagnosis and therapeutic management of bone metabolic disorders. We aim to uncover the critical function of exosomal ncRNAs within the context of bone metabolic diseases.

Estrogen deficiency-mediated osteoimmunity in postmenopausal osteoporosis

Postmenopausal osteoporosis (PMO) is a common disease associated with aging, and estrogen deficiency is considered to be the main cause of PMO. Recently, however, osteoimmunology has been revealed to be closely related to PMO. On the one hand, estrogen deficiency directly affects the activity of bone cells (osteoblasts, osteoclasts, osteocytes). On the other hand, estrogen deficiency-mediated osteoimmunity also plays a crucial role in bone loss in PMO. In this review, we systematically describe the progress of the mechanisms of bone loss in PMO, estrogen deficiency-mediated osteoimmunity, the differences between PMO patients and postmenopausal populations without osteoporosis, and estrogen deficiency-mediated immune cells (T cells, B cells, macrophages, neutrophils, dendritic cells, and mast cells) activity. The comprehensive summary of this paper provides a clear knowledge context for future research on the mechanism of PMO bone loss.

Exploring the Role of Circular RNA in Bone Biology: A Comprehensive Review

Circular RNAs (circRNAs) have emerged as pivotal regulators of gene expression with diverse roles in various biological processes. In recent years, research into circRNAs' involvement in bone biology has gained significant attention, unveiling their potential as novel regulators and biomarkers in bone-related disorders and diseases. CircRNAs, characterized by their closed-loop structure, exhibit stability and resistance to degradation, underscoring their functional significance. In bone tissue, circRNAs are involved in critical processes such as osteogenic differentiation, osteoclastogenesis, and bone remodeling through intricate molecular mechanisms including microRNA regulation. Dysregulated circRNAs are associated with various bone disorders, suggesting their potential as diagnostic and prognostic biomarkers. The therapeutic targeting of these circRNAs holds promise for addressing bone-related conditions, offering new perspectives for precision medicine. Thus, circRNAs constitute integral components of bone regulatory networks, impacting both physiological bone homeostasis and pathological conditions. This review provides a comprehensive overview of circRNAs in bone biology, emphasizing their regulatory mechanisms, functional implications, and therapeutic potential.

CircCOX6A1 suppresses osteogenic differentiation and aggravates osteoporosis via miR-512-3p/DYRK2 axis

BACKGROUND

Osteoporosis (OP), characterized by compromised bone integrity and increased fracture risk, poses a significant health challenge. Circular RNAs (circRNAs) have emerged as crucial regulators in various pathophysiological processes, prompting investigation into their role in osteoporosis. This study aimed to elucidate the involvement of circCOX6A1 in OP progression and understand its underlying molecular mechanisms. The primary objective was to explore the impact of circCOX6A1 on bone marrow-derived mesenchymal stem cells (BMSCs) and its potential interactions with miR-512-3p and DYRK2.

METHODS

GSE161361 microarray analysis was employed to assess circCOX6A1 expression in OP patients. We utilized in vitro and in vivo models, including BMSC cultures, osteogenic differentiation assays, and an OVX-induced mouse model of OP. Molecular techniques such as quantitative RT-PCR, western blotting, and functional assays like alizarin red staining (ARS) were employed to evaluate circCOX6A1 effects on BMSC proliferation, apoptosis, and osteogenic differentiation. The interaction between circCOX6A1, miR-512-3p, and DYRK2 was investigated through dual luciferase reporter assays, RNA immunoprecipitation, and RNA pull-down assays.

RESULTS

CircCOX6A1 was found to be upregulated in osteoporosis patients, and its expression inversely correlated with osteogenic differentiation of BMSCs. CircCOX6A1 knockdown enhanced osteogenic differentiation, as evidenced by increased mineralized nodule formation and upregulation of osteogenic markers. In vivo, circCOX6A1 knockdown ameliorated osteoporosis progression in OVX mice. Mechanistically, circCOX6A1 acted as a sponge for miR-512-3p, subsequently regulating DYRK2 expression.

CONCLUSION

This study provides compelling evidence for the role of circCOX6A1 in osteoporosis pathogenesis. CircCOX6A1 negatively regulates BMSC osteogenic differentiation through the miR-512-3p/DYRK2 axis, suggesting its potential as a therapeutic target for mitigating OP progression.

Circulating Hsa-miR499a-5p as markers in dysmobility syndrome patients: a new index for diagnosing dysmobility syndrome based on osteoporosis and predicting fracture risk

BACKGROUND

Dysmobility syndrome based on osteoporosis (ODS) is a disease characterized by low bone mass and low muscle mass. Its features are high fracture and high fall risk. Falls and fractures are the most important factors affecting the quality of life and lifespan of ODS. However, there is no serum marker for the evaluation of ODS patients.Our previous studies have shown that the expression of circulating miRNA is stable and is a good marker for disease diagnosis. Therefore, this study aims to explore potential serum markers of ODS.

METHODS

A total of 78 subjects were included in this study. The data including appendicular skeletal muscle mass index, bone mineral density, bone metabolism markers, and other relevant information were collected for analysis. Real-time quantitative polymerase chain reaction was used to detect 19 miRNAs associated with muscle mass reduction. The correlation of quantitative data was analyzed by Pearson. The receiver operating characteristic curve was used to evaluate the performance of miRNA as a biomarker.

RESULTS

In this study, we found that the muscle mass and strength of patients with ODS are significantly reduced and are negatively correlated with the risk of fracture. The hsa-miR-499a-5p is specifically downregulated in ODS, and is positively correlated with muscle mass and strength, and negatively correlated with the risk of fracture. Compared with muscle mass and strength, hsa-miR-499a-5p has better sensitivity and specificity as a diagnostic marker.

CONCLUSION

hsa-miR-499a-5p is a potential serum biomarker for assessing muscle function and predicting fall or fracture risk in the ODS population.

The Potential of Exosomes for Osteoporosis Treatment: A Review

As a continuous process comprising bone resorption and formation, bone remodeling, plays an essential role in maintaining the balance of bone metabolism. One type of metabolic osteopathy is osteoporosis, which is defined by low bone mass and deteriorating bone microstructure. Osteoporosis patients are more likely to experience frequent osteoporotic fractures, which makes osteoporosis prevention and treatment crucial. A growing body of research has revealed that exosomes, which are homogenous vesicles released by most cell types, play a major role in mediating a number of pathophysiological processes, including osteoporosis. Exosomes may act as a mediator in cell-to-cell communication and offer a fresh perspective on information sharing. This review discusses the characteristics of exosomes and outlines the exosomes' underlying mechanism that contributes to the onset of osteoporosis. Recent years have seen a rise in interest in the role of exosomes in osteoporosis, which has given rise to innovative therapeutic approaches for the disease prevention and management.

Exosomes derived from BMSCs enhance diabetic wound healing through circ-Snhg11 delivery

BACKGROUND

Exosomes (Exos) generated from bone mesenchymal stem cells (BMSCs) are elucidated to enhance cutaneous wound healing in mice models of diabetes mellitus (DM). While underlying mechanisms remain unknown.

METHODS

Next-generation sequencing (NGS) was used to examine changes in circRNA expression levels following Exo treatment. Luciferase assays were used to determine the interactions between RNAs. Immunofluorescence staining was used to examine reactive oxygen species (ROS) in endothelial progenitor cells (EPCs) cultured in high glucose (HG) conditions. Therapeutic effects regarding Exos were also examined by immunofluorescence.

RESULTS

We found that Exo treatment enhanced cutaneous wound healing significantly. NGS indicated that circ-Snhg11 was involved in Exo-mediated tissue repairing. Downregulation of circ-Snhg11 decreased Exo-mediated therapy responses during wound healing in diabetic mouse. Our luciferase reporter data confirmed that SLC7A11 and miR-144-3p were circ-Snhg11 downstream targets. miR-144-3p overexpression or SLC7A11 knockdown altered the protective effects of circ-Snhg11 upon EPCs exposed to HG conditions. Upregulation of circ-Snhg11 incremented therapy effects of Exo treatment during wound healing in DM mice through enhanced angiogenesis along with a reduction in GPX4-mediated ferroptosis.

CONCLUSIONS

circ-Snhg11 in BMSC-Exos enhanced SLC7A11/GPX4-mediated anti-ferroptosis signals via miR-144-3p sponging resulting in enhanced diabetic wound healing and improved angiopoiesis.

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.

Regulatory mechanisms of circular RNAs during human mesenchymal stem cell osteogenic differentiation

Human osteogenic differentiation is a complex and well-orchestrated process which involves a plethora of molecular players and cellular processes. A growing number of studies have underlined that circular RNAs (circRNAs) play an important regulatory role during human osteogenic differentiation. CircRNAs are single-stranded, covalently closed non-coding RNA molecules that are acquiring increased attention as epigenetic regulators of gene expression. Given their intrinsic high conformational stability, abundance, and specificity, circRNAs can undertake various biological activities in order to regulate multiple cellular processes, including osteogenic differentiation. The most recent evidence indicates that circRNAs control human osteogenesis by preventing the inhibitory activity of miRNAs on their downstream target genes, using a competitive endogenous RNA mechanism. The aim of this review is to draw attention to the currently known regulatory mechanisms of circRNAs during human osteogenic differentiation. Specifically, we provide an understanding of recent advances in research conducted on various human mesenchymal stem cell types that underlined the importance of circRNAs in regulating osteogenesis. A comprehensive understanding of the underlying regulatory mechanisms of circRNA in osteogenesis will improve knowledge on the molecular processes of bone growth, resulting in the potential development of novel preclinical and clinical studies and the discovery of novel diagnostic and therapeutic tools for bone disorders.

17β-Estradiol-Loaded Exosomes for Targeted Drug Delivery in Osteoporosis: A Comparative Study of Two Loading Methods

Purpose

Exosomes are natural nanoparticles that participate in intercellular communication through molecular transport. Recently, due to their membrane vesicular structure and surface proteins, exosomes have been used extensively in the research field of drug delivery. Osteoporosis is an inflammation in which the cellular balance of bone tissue is disturbed that reduces bone density and making bone prone to abnormal fractures with small amount of force. Utilizing estrogen is one of the main therapeutic strategies for osteoporosis. Despite the positive effects of estrogen on bone tissue, changes in the natural estrogen levels of the body can cause a number of diseases such as different types of cancer. Therefore, designing a therapeutic system which controls more accurate tissue targeting of estrogen seems to be a rational and promising practical approach.

Methods

In this study, bone marrow mesenchymal stem cells (BMMSCs)-derived exosomes were loaded by estradiol using two different methods of drug loading, namely incubation and sonication methods and then the survival effects of the drug loaded exosomes on BMMSCs was investigated.

Results

Examination of size, shape, and surface factors of exosomes in different states (pure exosomes and drug-loaded exosomes) showed that the round morphology of exosomes was preserved in all conditions. However, the particles size increased significantly when loaded by sonication method. The increased survival of BMMSCs was noted with estradiol-loaded exosomes when compared to the control group.

Conclusion

The results suggest that estradiol-loaded exosomes have potential to be used as nano-drug carriers in the treatment of osteoporosis.

Implications and theragnostic potentials of circular RNAs in rheumatic diseases

Circular RNAs (circRNAs), a class of non-coding RNAs (ncRNAs), are highly stable and ubiquitous molecules that exhibit tissue-specific expression. Accumulating evidence has shown that aberrant expression of circRNAs can play a role in the pathogenesis of several diseases. Rheumatic diseases are a varied group of autoimmune and inflammatory disorders affecting mainly the musculoskeletal system. Notably, circRNAs, which are essential immune system gene modulators, are strongly linked to the occurrence and progression of autoimmune disorders. Here, we present and discuss the current findings concerning the roles, implications and theragnostic potentials of circRNAs in common rheumatic diseases, including ankylosing spondylitis (AS), osteoarthritis (OA), osteoporosis (OP), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Crohn's disease (CD), and gout. This review aims to provide new insights to support the development of novel diagnostic and therapeutic strategies for these disabling diseases.

Exosomes: A new option for osteoporosis treatment

Osteoporosis is a systemic bone disease characterized by reduced bone mass and destruction of bone microarchitecture, leading to increased bone fragility and susceptibility to fracture. However, the pathogenesis and molecular mechanisms of this disease remain unclear. Extracellular vesicles, structures originating from the plasma membrane and ranging from 30 nm to 5 µm in diameter, play an important role in intercellular communication in the bone microenvironment. Exosomes are extracellular vesicles that deliver cargo molecules, including endogenous proteins, lipids and nucleic acids. These cargo molecules are encapsulated in a lipid bilayer and internalized by target cells through receptor-ligand interactions or lipid membrane fusion. With the advancement of exosome research, exosome therapy for osteoporosis is fast becoming a research hotspot for researchers. This review aims to discuss the role of exosomes in the pathogenesis of osteoporosis. In addition, emerging diagnostic and therapeutic properties of exosomes are described to highlight the potential role of exosomes in osteoporosis.

Circular RNA MELK Promotes Chondrocyte Apoptosis and Inhibits Autophagy in Osteoarthritis by Regulating MYD88/NF-κB Signaling Axis through MicroRNA-497-5p

Osteoarthritis (OA) is a rheumatic disease and its pathogenesis involves the dysregulation of noncoding RNAs. Therefore, the regulatory mechanism of circular RNA MELK (circMELK) was specified in this work. OA human cartilage tissue was collected, and circMELK, miR-497-5p, and myeloid differentiation factor 88 (MYD88) expression were examined. Human chondrocytes were stimulated with interleukin- (IL-) 1β and interfered with vectors altering circMELK, miR-497-5p, and MyD88 expression to observe their effects on cell viability, cell cycle and apoptosis, autophagy, and inflammation. The binding relationship between RNAs was verified. The data presented that OA cartilage tissues presented raised circMELK and MYD88 and inhibited miR-497-5p expression. IL-1β suppressed cell viability, prevented cell cycle, and induced apoptosis, autophagy, and inflammation of chondrocytes. Functionally, IL-1β-induced changes of chondrocytes could be attenuated by suppressing circMELK or overexpressing miR-497-5p. circMELK acted as a sponge of miR-497-5p while miR-497-5p was a regulator of MYD88. MYD88 restricted the effect of overexpressing miR-497-5p on IL-1β-stimulated chondrocytes. MYD88 triggered nuclear factor-kappaB (NF-κB) pathway activation. Shortly, CircMELK promotes chondrocyte apoptosis and inhibits autophagy in OA by regulating MYD88/NF-κB signaling axis through miR-497-5p. Our study proposes a new molecular mechanism for the development of OA.

Expression profile analysis of lncRNA in bone marrow mesenchymal stem cells exosomes of postmenopausal osteoporosis patients through microarray and bioinformatics analyses

BACKGROUND

Postmenopausal osteoporosis (PMOP) is the most common bone metabolic disease affecting women worldwide. In this study, we investigate the role of long non-coding RNA (lncRNA) expression in exosomes obtained from bone marrow mesenchymal stem cells (BMSCs) of patients with PMOP.

METHODS

BMSCs from patients diagnosed with PMOP and healthy post-menopausal females as controls were isolated and cultured before exosome extraction. RNA microarray technology was used to identify differentially expressed lncRNAs in exosomes from BMSCs. Bioinformatics technology was utilized to analyze the roles of differentially expressed lncRNAs. Further, RT-qPCR was used to validate differentially expressed lncRNAs in 20 pairs of clinical samples.

RESULTS

A total of 286 differentially expressed lncRNAs were detected in the exosomes from BMSCs unlike in the control group, among which 148 were up-regulated, whereas 138 were down-regulated. RT-qPCR identified five critical lncRNAs, including ENST00000593078, NR_120593, ENST00000422343, MEG3 and NR_029192. This was consistent with the microarray results and with a significant difference (P < 0.01). Based on the differentially expressed lncRNAs, we constructed lncRNA-miRNA-mRNA interaction networks. Functional analysis revealed that differentially expressed lncRNAs in patients with PMOP potentially target Wnt/β-catenin, MAPK, and PI3K-Akt pathways.

CONCLUSION

In summary, we detected several dysregulated lncRNAs regulating PMOP progression in exosomes extracted from BMSCs of affected patients acting as novel biomarkers. This in turn provides valuable data for targeted treatment of PMOP.

SUBJECTS

Genomics; Molecular biology; Orthopedics; Women's Health.

Roles of circular RNAs in osteogenic differentiation of bone marrow mesenchymal stem cells (Review)

Bone marrow mesenchymal stem cells (BMSCs) can differentiate into osteoblasts, chondrocytes, adipocytes and even myoblasts, and are therefore defined as pluripotent cells. BMSCs have become extremely important seed cells in gene therapy, tissue engineering, cell replacement therapy and regenerative medicine due to their potential in multilineage differentiation, self‑renewal, immune regulation and other fields. Circular RNAs (circRNAs) are a class of non‑coding RNAs that are widely present in eukaryotic cells. Unlike standard linear RNAs, circRNAs form covalently closed continuous loops with no 5' or 3' polarity. circRNAs are abundantly expressed in cells and tissues, and are highly conserved and relatively stable during evolution. Numerous studies have shown that circRNAs play an important role in the osteogenic differentiation of BMSCs. Further studies on the role of circRNAs in the osteogenic differentiation of BMSCs can provide a new theoretical and experimental basis for bone tissue engineering and clinical treatment.

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.

Application of extracellular vesicles derived from mesenchymal stem cells as potential therapeutic tools in autoimmune and rheumatic diseases

Mesenchymal stem cells (MSCs) have been proven to have superior potential to be used astherapeutic candidates in various disorders. Nevertheless, the clinical application of these cells have been restricted because of their tumorigenic properties. Increasing evidence has established that the valuable impacts of MSCs are mainly attributable to the paracrine factors including extracellular vesicles (EVs). EVs are nanosized double-layer phospholipid membrane vesicles contain various proteins, lipids and miRNAs which mediate cell-to-cell communications. Due to their inferior immunogenicity and tumorigenicity, as well as easier management, EVs have drawn attention as potential cell-free replacement therapy to MSCs. For that reason, herein, we reviewed the recent findings of researches on different MSC-EVs and their effectiveness in the treatment of several autoimmune and rheumatic diseases including multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, osteoarthritis, osteoporosis, and systemic lupus erythematosus as well as Sjogren's syndrome, systemic sclerosis and other autoimmune diseases.