Presence and function of microRNA-92a in chondrogenic ATDC5 and adipose-derived mesenchymal stem cells

miR-92a-3p-inspired shRNA exhibits pro-chondrogenic and chondrocyte protective effects in osteoarthritis treatment through targeting SMAD6/7

INTRODUCTION

Osteoarthritis (OA) compromises patients' quality of life and requires further study. Although miR-92a-3p was reported to possess chondroprotective effects, the underlying mechanism requires further clarification. The objectives of this study were to elucidate the mechanism by which miR-92a-3p alleviates OA and to examine the efficacy of shRNA-92a-3p, which was designed based on mature miR-92a-3p.

MATERIALS AND METHODS

TargetScan and luciferase reporter assay were used to predict the target of miR-92a-3p. Adipose-derived stem cells (ADSCs) were transfected with miR-92a-3p/miR-NC mimic for the analysis of chondrogenic biomarkers and SMAD proteins. ADSCs and osteoarthritic chondrocytes were transduced with shRNA-92a-3p for the analysis of chondrogenic biomarkers and SMAD proteins. OA was surgically induced in C57BL/6JJcl mice, and ADSCs with/without shRNA-92a-3p transduction were intra-articularly injected for the assessment of cartilage damage.

RESULTS

SMAD6 and SMAD7 were predicted as direct targets of miR-92a-3p by TargetScan and luciferase reporter assay. Transfection of the miR-92a-3p mimic resulted in a decrease in SMAD6 and SMAD7 levels and an increase in phospho-SMAD2/3, phospho-SMAD1/5/9, SOX9, collagen type II, and aggrecan levels in ADSCs. Furthermore, shRNA-92a-3p decreased SMAD6 and SMAD7 levels, and increased phospho-SMAD2/3, phospho-SMAD1/5/9, SOX9, collagen type II, and aggrecan levels in ADSCs and osteoarthritic chondrocytes. Additionally, ADSC-shRNA-92a-3p-EVs reduced the rate of decrease of SOX9, collagen type II, and aggrecan in osteoarthritic chondrocytes. In mice with surgically induced OA, shRNA-92a-3p-treated ADSCs alleviated cartilage damage more effectively than nontreated ADSCs.

CONCLUSIONS

miR-92a-3p and shRNA-92a-3p exhibit therapeutic effects in treating OA by targeting SMAD6 and SMAD7, thereby enhancing TGF-β signaling.

Mesenchymal stem cells in osteoarthritis: The need for translation into clinical therapy

Widely used for cell-based therapy in various medical fields, mesenchymal stem cells (MSCs) show capacity for anti-inflammatory effects, anti-apoptotic activity, immunomodulation, and tissue repair and regeneration. As such, they can potentially be used to treat osteoarthritis (OA). However, MSCs from different sources have distinct advantages and disadvantages, and various animal models and clinical trials using different sources of MSCs are being conducted in OA regenerative medicine. It is now widely believed that the primary tissue regeneration impact of MSCs is via paracrine effects, rather than direct differentiation and replacement. Cytokines and molecules produced by MSCs, including extracellular vesicles with mRNAs, microRNAs, and bioactive substances, play a significant role in OA repair. This chapter outlines the properties of MSCs and recent animal models and clinical trials involving MSCs-based OA therapy, as well as how the paracrine effect of MSCs acts in OA cartilage repair. Additionally, it discusses challenges and controversies in MSCs-based OA therapy. Despite its limits and unanticipated hazards, MSCs have the potential to be translated into therapeutic therapy for future OA treatment.

Adipose mesenchymal stem cell-derived exosomal microRNAs ameliorate polycystic ovary syndrome by protecting against metabolic disturbances

Polycystic ovary syndrome (PCOS) is the most common endocrine and metabolic disorder in women of childbearing age. Adipose mesenchymal stem cells (AMSCs) secrete cytokines involved in the regulation of metabolism and immunity. However, it remains unclear whether exosomes secreted by AMSCs (AMSC-EXOs) can rescue the polycystic phenotype and metabolic dysfunction in PCOS ovaries. Here, we show that AMSC-EXOs can protect against metabolic disturbances, ameliorate ovarian polycystic, and improve fertility in a rat model of PCOS. AMSC-EXOs inhibited the expression of B-cell translocation gene 2 by transferring miR-21-5p to the livers of rats with PCOS, thus activating the IRS1/AKT pathway and increasing hepatic metabolism. The role of AMSC-EXOs in transferring miRNAs to the liver to improve metabolic dysfunction in PCOS and reproduction by rescuing a non-coding RNA pathway was also discovered. This study provides a theoretical basis for the use of rat adipose stem cells and their secreted exosomes to treat PCOS.

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

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

Dental Pulp Stem Cell-Derived Secretome and Its Regenerative Potential

The therapeutic potential of the dental pulp stem (DSC) cell-derived secretome, consisting of various biomolecules, is undergoing intense research. Despite promising in vitro and in vivo studies, most DSC secretome-based therapies have not been implemented in human medicine because the paracrine effect of the bioactive factors secreted by human dental pulp stem cells (hDPSCs) and human exfoliated deciduous teeth (SHEDs) is not completely understood. In this review, we outline the current data on the hDPSC- and SHED-derived secretome as a potential candidate in the regeneration of bone, cartilage, and nerve tissue. Published reports demonstrate that the dental MSC-derived secretome/conditional medium may be effective in treating neurodegenerative diseases, neural injuries, cartilage defects, and repairing bone by regulating neuroprotective, anti-inflammatory, antiapoptotic, and angiogenic processes through secretome paracrine mechanisms. Dental MSC-secretomes, similarly to the bone marrow MSC-secretome activate molecular and cellular mechanisms, which determine the effectiveness of cell-free therapy. Many reports emphasize that dental MSC-derived secretomes have potential application in tissue-regenerating therapy due to their multidirectional paracrine effect observed in the therapy of many different injured tissues.

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

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

Diagnostic and Therapeutic Role of Extracellular Vesicles in Articular Cartilage Lesions and Degenerative Joint Diseases

Two leading contributors to the global disability are cartilage lesions and degenerative joint diseases, which are characterized by the progressive cartilage destruction. Current clinical treatments often fail due to variable outcomes and an unsatisfactory long-term repair. Cell-based therapies were once considered as an effective solution because of their anti-inflammatory and immunosuppression characteristics as well as their differentiation capacity to regenerate the damaged tissue. However, stem cell-based therapies have inherent limitations, such as a high tumorigenicity risk, a low retention, and an engraftment rate, as well as strict regulatory requirements, which result in an underwhelming therapeutic effect. Therefore, the non-stem cell-based therapy has gained its popularity in recent years. Extracellular vesicles (EVs), in particular, like the paracrine factors secreted by stem cells, have been proven to play a role in mediating the biological functions of target cells, and can achieve the therapeutic effect similar to stem cells in cartilage tissue engineering. Therefore, a comprehensive review of the therapeutic role of EVs in cartilage lesions and degenerative joint diseases can be discussed both in terms of time and favorability. In this review, we summarized the physiological environment of a joint and its pathological alteration after trauma and consequent changes in EVs, which are lacking in the current literature studies. In addition, we covered the potential working mechanism of EVs in the repair of the cartilage and the joint and also discussed the potential therapeutic applications of EVs in future clinical use.

Research Progress on Stem Cell Therapies for Articular Cartilage Regeneration

Injury of articular cartilage can cause osteoarthritis and seriously affect the physical and mental health of patients. Unfortunately, current surgical treatment techniques that are commonly used in the clinic cannot regenerate articular cartilage. Regenerative medicine involving stem cells has entered a new stage and is considered the most promising way to regenerate articular cartilage. In terms of theories on the mechanism, it was thought that stem cell-mediated articular cartilage regeneration was achieved through the directional differentiation of stem cells into chondrocytes. However, recent evidence has shown that the stem cell secretome plays an important role in biological processes such as the immune response, inflammation regulation, and drug delivery. At the same time, the stem cell secretome can effectively mediate the process of tissue regeneration. This new theory has attributed the therapeutic effect of stem cells to their paracrine effects. The application of stem cells is not limited to exogenous stem cell transplantation. Endogenous stem cell homing and in situ regeneration strategies have received extensive attention. The application of stem cell derivatives, such as conditioned media, extracellular vesicles, and extracellular matrix, is an extension of stem cell paracrine theory. On the other hand, stem cell pretreatment strategies have also shown promising therapeutic effects. This article will systematically review the latest developments in these areas, summarize challenges in articular cartilage regeneration strategies involving stem cells, and describe prospects for future development.

Identifying the Potential Differentially Expressed miRNAs and mRNAs in Osteonecrosis of the Femoral Head Based on Integrated Analysis

Purpose

Osteonecrosis of the femoral head is a common disease of the hip that leads to severe pain or joint disability. We aimed to identify potential differentially expressed miRNAs and mRNAs in osteonecrosis of the femoral head.

Methods

The data of miRNA and mRNA were firstly downloaded from the database. Secondly, the regulatory network of miRNAs-mRNAs was constructed, followed by function annotation of mRNAs. Thirdly, an in vitro experiment was applied to validate the expression of miRNAs and targeted mRNAs. Finally, GSE123568 dataset was used for electronic validation and diagnostic analysis of targeted mRNAs.

Results

Several regulatory interaction pairs between miRNA and mRNAs were identified, such as hsa-miR-378c-WNT3A/DACT1/CSF1, hsa-let-7a-5p-RCAN2/IL9R, hsa-miR-28-5p-RELA, hsa-miR-3200-5p-RELN, and hsa-miR-532-5p-CLDN18/CLDN10. Interestingly, CLDN10, CLDN18, CSF1, DACT1, IL9R, RCAN2, RELN, and WNT3A had the diagnostic value for osteonecrosis of the femoral head. Wnt signaling pathway (involved WNT3A), chemokine signaling pathway (involved RELA), focal adhesion and ECM-receptor interaction (involved RELN), cell adhesion molecules (CAMs) (involved CLDN18 and CLDN10), cytokine-cytokine receptor interaction, and hematopoietic cell lineage (involved CSF1 and IL9R) were identified.

Conclusion

The identified differentially expressed miRNAs and mRNAs may be involved in the pathology of osteonecrosis of the femoral head.

Engineered-extracellular vesicles as an optimistic tool for microRNA delivery for osteoarthritis treatment

Worldwide, osteoarthritis (OA) is one of the most common chronic diseases. In OA, profiling gene expression changes occur and cartilage tissue homeostasis is lost. Suggestions for OA treatment include regulation of gene expressions via the use of microRNAs (miRNAs). However, problems exist with the use of miRNAs, the most important of which is the delivery of sufficient amounts of effective miRNAs to save cartilage tissue. The engineering of extracellular vesicles (EVs) with the use of advanced techniques would be an efficient OA treatment. Therefore, we discuss the importance of miRNAs in terms of cartilage tissue regeneration and review recent advances in production of enriched EVs and miRNA delivery by EVs for future clinical applications.

Interplay between C-type lectin receptors and microRNAs in cellular homeostasis and immune response

C-type lectin receptors (CLRs) belong to the family of pattern recognition receptors (PRRs). They have a critical role to play in the regulation of a range of physiological functions including development, respiration, angiogenesis, inflammation, and immunity. CLRs can recognize distinct and conserved exogenous pathogen-associated as well as endogenous damage-associated molecular patterns. These interactions set off downstream signaling cascades, leading to the production of inflammatory mediators, activation of effector immune cells as well as regulation of the developmental and physiological homeostasis. CLR signaling must be tightly controlled to circumvent the excessive inflammatory burden and to maintain the cellular homeostasis. Recently, MicroRNAs (miRNAs) have been shown to be important regulators of expression of CLRs and their downstream signaling. The delicate balance between miRNAs and CLRs seems crucial in almost all aspects of multicellular life. Any dysregulations in the miRNA-CLR axes may lead to tumorigenesis or inflammatory diseases. Here, we present an overview of the current understanding of the central role of miRNAs in the regulation of CLR expression, profoundly impacting upon homeostasis and immunity, and thus, development of therapeutics against immune disorders.

MiR-520d-5p modulates chondrogenesis and chondrocyte metabolism through targeting HDAC1

MicroRNAs (miRNAs) play an essential role in the chondrogenesis and the progression of osteoarthritis (OA). This study aimed to determine miRNAs associated with chondrogenesis of human mesenchymal stem cells (hMSCs) and chondrocyte metabolism. MiRNAs were screened in hMSCs during chondrogenesis by RNA-seq and qRT-PCR. MiRNA expression was determined in primary human chondrocytes (PHCs), and degraded cartilage samples. MiRNA mimics and inhibitors were transfected to cells to determine the effect of miRNA. Bioinformatic analysis and luciferase reporter assays were applied to determine the target gene of miRNA. The results demonstrated that miR-520d-5p was increased in hMSCs chondrogenesis. The overexpression and knockdown of miR-520d-5p promoted and inhibited chondrogenesis, and regulated chondrocyte metabolism. Histone deacetylase 1 (HDAC1) was decreased in hMSCs chondrogenesis, and HDAC1 was a targeting gene of miR-520d-5p. CI994, HDAC1 inhibitor, elevated cartilage-specific gene expressions and promoted hMSCs chondrogenesis. In IL-1β-treated PHCs, CI994 promoted AGGRECAN expression and suppressed MMP-13 expression, abolishing the effect of IL-1β on PHCs. Taken together, these results suggest that miR-520d-5p promotes hMSCs chondrogenesis and regulates chondrocyte metabolism through targeting HDAC1. This study provides novel understanding of the molecular mechanism of OA progression.

Potential Application of Human β-Defensin 4 in Dental Pulp Repair

When pulp tissue is damaged by caries or trauma, vital pulp therapy (VPT) can help preserve the pulp tissue for long-term retention of teeth. However, the choice of pulp capping agent used in VPT is important for the successful preservation of the pulp tissue. Here we investigated the expression and biological function of human β-defensin 4 (HBD4) in dental pulp stem cells (DPSC) and explored its potential as a pulp capping agent. We examined the expression of HBD4 in DPSC in vitro using qPCR and immunofluorescence staining. We also looked at the effect of HBD4 on inflammatory factors in lipopolysaccharide (LPS)-stimulated DPSC, and its effects on mineralizing cell phenotype differentiation, via qPCR and western blot. Finally, we examined the ability of HBD4 to promote the restoration of the pulp-dentin complex in vivo, using male Wistar rats with reversible pulpitis. We found HBD4 was highly expressed in DPSC stimulated by TNF-α and IL-1α. HBD4 down-regulated the expression of inflammatory mediators (i.e., IL-1α, IL-1β, IL-6, TNF-α) in LPS-stimulated DPSC, and suppressed MAPK activity and the NF-κB pathway. HBD4 also enhanced the differentiation of DPSC into osteoblasts or odontoblasts, potentially by modulating the Notch pathway. Furthermore, HBD4 controlled the degree of pulp inflammation in a rat model of reversible pulpitis and induced the formation of restorative dentin. Together our findings indicate HBD4 may be a useful pulp capping agent for use in VPT.

Extracellular vesicles: Potential role in osteoarthritis regenerative medicine

Osteoarthritis (OA) is a prevalent whole joint disease characterised by cartilage degradation, subchondral bone sclerosis and bone remodelling, and synovium inflammation, leading to pain, deformity, and cartilage dysfunction. Currently, there is no appropriate therapy for OA, and available treatments simply aim to reduce pain and swelling. Exosomes are membrane-bound extracellular vesicles secreted by almost all cells, receiving increasing interest because of their effect in cell-to-cell communication. Increasing evidence suggests that exosomes play an important role in cartilage physiological and pathological effects. This article reviews the potential role of exosomes in OA regenerative medicine. Special attention is given to mesenchymal stem cells-derived exosomes due to the extensive research on their cartilage repair property and their function as miRNA cargo. More investigations are needed for the effects of exosomes from synovial fluid and chondrocytes in joints. A better understanding of the mechanisms will contribute to a novel and promising therapy for OA patients.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

A better understanding of the role of extracellular vesicles in regenerative medicine will contribute to a novel and promising therapy for OA patients.

Identification of differentially expressed miRNAs associated with thermal injury in epidermal stem cells based on RNA-sequencing

Current research indicates that epidermal stem cells (EpSCs) play an important role in promoting wound healing, but the mechanism of action of these cells during wound repair following thermal damage remains unclear. In the present study, the trypsin digestion method was used to isolate human EpSCs and the cells were incubated in a 51.5°C water tank for 35 sec to construct a thermal injury model. The differentially expressed miRNAs were identified using high-throughput sequencing technology, and bioinformatic methods were used to predict their target genes and signaling pathways that may be involved in wound repair. A total of 33 miRNAs including, hsa-miR-1973, hsa-miR-4485-3p, hsa-miR-548-5p, hsa-miR-212-3p and hsa-miR-4461 were upregulated, whereas 21 miRNAs including, hsa-miR-4520-5p, hsa-miR-4661-5p, hsa-miR-191-3p, hsa-miR-129-5p, hsa-miR-147b and hsa-miR-6868-3p were downregulated following thermal injury of the human EpSCs. The bioinformatic analysis indicated that the differentially expressed miRNAs are involved in biological processes such as cell proliferation and differentiation, cell growth apoptosis, cell adhesion and migration. The results showed that there is a differential expression pattern of miRNAs after thermal injury of human EpSCs and these differences are involved in the regulation of the wound healing process. These findings provide new clues for further study of the wound healing mechanism and targeted therapy.

MicroRNA-320c inhibits development of osteoarthritis through downregulation of canonical Wnt signaling pathway

AIMS

Osteoarthritis (OA) is a leading cause of deformity in aging people. Emerging evidence suggests that microRNAs and Wnt signaling pathway are associated with its pathogenesis. We aimed to determine whether microRNA-320c inhibits the development of osteoarthritis by suppressing Wnt signaling pathway.

MATERIALS AND METHODS

MiR-320c and β-catenin expression was assessed in human adipose derived stem cells (hADSCs) model of chondrogenesis and in normal and OA primary human chondrocytes. OA chondrocytes were transfected with miR-320c or its antisense inhibitor and β-catenin siRNA respectively. Direct interaction between miR-320c and β-catenin mRNA as well as activity of β-catenin/TCF complex were confirmed by luciferase reporter assay. Mmu-miR-320-3p agomir was intra-articularly injected in collagenase-induced OA mouse model. OA progression was evaluated histologically and immunohistochemically.

KEY FINDINGS

MiR-320c was decreased and β-catenin was increased in OA chondrocytes and late stage of hADSCs chondrogenesis. Overexpression of miR-320c and knockdown of β-catenin had similar effects that the cartilage-specific genes were elevated and hypertrophy-related genes were down-regulated in OA chondrocytes. Luciferase reporter assay confirm that miR-320c regulated the expression of β-catenin by directly targeting 3'UTR of β-catenin mRNA and decreased the relative transcriptional activity of the β-catenin/TCF complex. Injection of mmu-miR-320-3p attenuated OA progression in the OA mouse model.

SIGNIFICANCE

Our results supports that miR-320c can inhibits the degeneration of osteoarthritis chondrocytes via suppressing the canonical Wnt signaling pathway and indicates the potential of miR-320c as a novel therapeutic agent for osteoarthritis treatment.

miR-1307-3p suppresses the chondrogenic differentiation of human adipose-derived stem cells by targeting BMPR2

MicroRNAs (miRs) are involved in several physiological processes, including chondrogenic differentiation, however, their expression and roles in the chondrogenic differentiation of human adipose-derived stem cells (hADSCs) remain to be fully elucidated to date. Our previous study showed that miR-1307-3p was significantly downregulated during chondrogenic differentiation by microarray and northern blot analysis. The present study aimed to investigate the effects of miR-1307-3p on chondrogenic differentiation and the underlying mechanisms. First, the decreased expression of miR-1307-3p was confirmed by reverse transcription-quantitative polymerase chain reaction analysis. Subsequently, gain- and loss-of-function of miR-1307-3p experiments showed that the overexpression of miR-1307-3p suppressed the deposition of cartilage matrix proteoglycans and decreased the expression of cartilage-related markers, including sex determining region Y-box 9, collagen type II α1 chain and aggrecan, whereas the knockdown of miR-1307-3p had the opposite effect. In addition, bone morphogenetic protein receptor type 2 (BMPR2) was identified as a target of miR-1307-3p. Further mechanistic investigations showed that miR-1307-3p attenuated the chondrogenic differentiation of hADSCs at least partly by inhibiting BMPR2-mothers against decapentaplegic signaling pathways. In conclusion, the findings revealed that miR-1307-3p inhibited the chondrogenic differentiation of hADSCs by targeting BMPR2 and its down-stream signaling pathway, which may provide novel therapeutic clues for the treatment of cartilage injury.

MicroRNA-193b-3p regulates matrix metalloproteinase 19 expression in interleukin-1β-induced human chondrocytes

Micro(mi)RNAs are small, non-coding RNA molecules known to play a significant role in osteoarthritis (OA) initiation and development, and similar to matrix metalloproteinases (MMPs), they participate in cartilage degeneration and cleave multiple extracellular matrices. The aim of this study was to determine whether the expression of MMP-19 in interleukin (IL)-1β-induced human chondrocytes is directly regulated by miR-193b-3p. Expression levels of miR-193b-3p and MMP-19 in normal and osteoarthritis (OA) human cartilage, and interleukin-1 β (IL-1β)-induced human chondrocytes were determined by real-time polymerase chain reaction. Additionally, expression level of MMP-19 in IL-1β-induced human chondrocytes was estimated by Western blotting and immunohistochemistry analyses. The effect of miR-193b-3p on MMP-19 expression was evaluated using transient transfection of normal human chondrocytes with miR-193b-3p mimic or its antisense inhibitor (miR-193b-3p inhibitor), and siMMP-19. The putative binding site of miR-193b-3p in the 3'-untranslated region (UTR) of MMP-19 mRNA was validated by luciferase reporter assay. miR-193b-3p expression was reduced in OA cartilage compared to that in normal chondrocytes, while the opposite was observed for MMP-19. Upregulation of MMP-19 expression was correlated with downregulation of miR-193b-3p in IL-1β-stimulated normal chondrocytes. Increase in miR-193b-3p levels was associated with silencing of MMP-19. Overexpression of miR-193b-3p suppressed the activity of the reporter construct containing the 3'-UTR of human MMP-19 mRNA and inhibited the IL-1β-induced expression of MMP-19 and iNOS in chondrocytes, while treatment with miR-193b-3p inhibitor enhanced MMP-19 expression. MiR-193b-3p is an important regulator of MMP-19 in human chondrocytes and may relieve the inflammatory response in OA.

Extracellular vesicles: A new therapeutic strategy for joint conditions

Extracellular vesicles (EVs) are attracting increasing interest since they might represent a more convenient therapeutic tool with respect to their cells of origin. In the last years much time and effort have been expended to determine the biological properties of EVs from mesenchymal stem cells (MSCs) and other sources. The immunoregulatory, anti-inflammatory and regenerative properties of MSC EVs have been demonstrated in in vitro studies and animal models of rheumatoid arthritis or osteoarthritis. This cell-free approach has been proposed as a possible better alternative to MSC therapy in autoimmune conditions and tissue regeneration. In addition, EVs show great potential as biomarkers of disease or delivery systems for active molecules. The standardization of isolation and characterization methods is a key step for the development of EV research. A better understanding of EV mechanisms of action and efficacy is required to establish the potential therapeutic applications of this new approach in joint conditions.

[Research progress of miRNA regulation in differentiation of adipose-derived stem cells]

Objective

To review the research progress of miRNA regulation in the differentiation of adipose-derived stem cells (ADSCs).

Methods

The recent literature associated with miRNAs and differentiation of ADSCs was reviewed. The regulatory mechanism was analyzed in detail and summarized.

Results

The results indicate that the expression of miRNAs changes during differentiation of ADSCs. In addition, miRNAs regulate the differentiation of ADSCs into adipocytes, osteoblasts, chondrocytes, neurons, and hepatocytes by regulating the signaling pathways involved in cell differentiation.

Conclusion

Through controlling the differentiation of ADSCs by miRNAs, the suitable seed cell for tissue engineering can be established. The review will provide a theoretical basis for molecular targeted therapy and stem cell therapy in clinic.

MicroRNA-92a-3p regulates the expression of cartilage-specific genes by directly targeting histone deacetylase 2 in chondrogenesis and degradation

OBJECTIVE

Increased activity of histone deacetylase 2 (HDAC2) has been found in patients with osteoarthritis (OA) and cartilage matrix degradation and has been shown to mediate the repression of cartilage-specific gene expression in human chondrocytes. We aimed to determine whether microRNA-92a-3p (miR-92a-3p) regulates cartilage-specific gene expression via targeted HDAC2 in chondrogenesis and degradation.

METHODS

miR-92a-3p expression was assessed in vitro in a human mesenchymal stem cells (hMSCs) model of chondrogenesis and in normal and OA primary human chondrocytes (PHCs), and in normal and OA human cartilage by in situ hybridization. hMSCs and PHCs were transfected with miR-92a-3p or its antisense inhibitor (anti-miR-92a-3p), respectively. PHCs were transfected with miR-92a-3p or anti-miR-92a-3p for 24 h before chromatin immunoprecipitation (ChIP) assay was performed with anti-ac-H3 antibody. Direct interaction between miR-92a-3p and its putative binding site in the 3'-untranslated region (3'-UTR) of HDAC2 mRNA was confirmed by luciferase reporter assay.

RESULTS

miR-92a-3p expression was elevated in chondrogenic and hypertrophic hMSC, while reduced in OA cartilage compared with normal cartilage. The overexpression of miR-92a-3p suppressed the activity of a reporter construct containing the 3'-UTR and inhibited HDAC2 expression in both hMSCs and PHCs, while treatment with anti-miR-92a-3p enhanced HDAC2 expression. ChIP assays showed that miR-92a-3p enhances H3 acetylation on aggrecan (ACAN), cartilage oligomeric protein (COMP) and Col2a1 promoter, and also promotes relative cartilage matrix expression.

CONCLUSION

Our results suggest that miR-92a-3p regulates cartilage development and homeostasis, which directly targets HDAC2, indicating histone hyperacetylation plays an important role in increased expression of cartilage matrix.

MSC exosome as a cell-free MSC therapy for cartilage regeneration: Implications for osteoarthritis treatment

Mesenchymal stem cell (MSC) therapies have demonstrated efficacy in cartilage repair in animal and clinical studies. The efficacy of MSC-based therapies which was previously predicated on the chondrogenic potential of MSC is increasingly attributed to the paracrine secretion, particularly exosomes. Exosomes are thought to function primarily as intercellular communication vehicles to transfer bioactive lipids, nucleic acids (mRNAs and microRNAs) and proteins between cells to elicit biological responses in recipient cells. For MSC exosomes, many of these biological responses translated to a therapeutic outcome in injured or diseased cells. Here, we review the current understanding of MSC exosomes, discuss the possible mechanisms of action in cartilage repair within the context of the widely reported immunomodulatory and regenerative potency of MSC exosomes, and provide new perspectives for development of an off-the-shelf and cell-free MSC therapy for treatment of cartilage injuries and osteoarthritis.

Adipose-derived stem cells in cartilage regeneration: current perspectives

Repair of cartilage injuries represents a musculoskeletal medicine criticism because of the poor ability to self-renewal of adult cartilage. Therefore, research focuses on developing new regenerative strategies combining chondrocytes or stem cells, scaffolds and growth factors. Because of the low proliferation capability of explanted chondrocytes, new chondrogenesis models, employing human adipose-derived stem cells (ASCs), have been investigated. ASCs are readily accessible with no morbidity and display the capability to differentiate into several cell lineages, including the spontaneous chondrogenic differentiation when entrapped in collagen gel scaffolds. Recent studies also defined some biomolecular mechanisms involved in ASC chondrogenesis in vitro, and their regenerative properties in bioengineered scaffolds and in the presence of growth factors. However, further investigations are required to validate these exciting preclinical results for the application of bioenginereed ASCs in the clinical practice.