microRNA-130b downregulation potentiates chondrogenic differentiation of bone marrow mesenchymal stem cells by targeting SOX9

Ocu-miR-10a-5p promotes the chondrogenic differentiation of rabbit BMSCs by targeting BTRC-mediated Wnt/β-catenin signaling pathway

MicroRNAs (miRNAs) play an important role in articular cartilage damage in osteoarthritis (OA). However, the biological role of miRNAs in the chondrogenic differentiation of bone marrow mesenchymal stem cell (BMSC) remains largely unclear. Rabbit bone marrow mesenchymal stem cells (rBMSCs) were isolated, cultured, and identified. Afterwards, rBMSCs were induced to chondrogenic differentiation, examined by Alcian Blue staining. Differentially expressed miRNAs were identified in rBMSCs between induced and non-induced groups by miRNA sequencing analysis, part of which was validated via PCR assay. Cell viability and apoptosis were assessed by CCK-8 assay and Hoechst staining. Saffron O staining was utilized to assess chondrocyte hyperplasia. The expression of specific chondrogenic markers, including COL2A1, SOX9, Runx2, MMP-13, Aggrecan, and BMP-2, were measured at mRNA and protein levels. The association between beta-transducin repeat containing E3 ubiquitin protein ligase (BTRC) and miR-10a-5p in the miRNA family from rabbit (ocu-miR-10a-5p) was determined by luciferase reporter assay. A total of 76 differentially expressed miRNAs, including 52 downregulated and 24 upregulated miRNAs, were identified in rBMSCs from the induced group. Inhibition of ocu-miR-10a-5p suppressed rBMSC viability and chondrogenic differentiation, as well as downregulated the expression of β-catenin, SOX9, COL2A1, MMP-13, and Runx2. BTRC was predicted and confirmed as a target of ocu-miR-10a-5p. Overexpression of BTRC rescued the promoting impacts of overexpressed ocu-miR-10a-5p on chondrogenic differentiation of rBMSCs and β-catenin expression. Taken together, our data suggested that ocu-miR-10a-5p facilitated rabbit BMSC survival and chondrogenic differentiation by activating Wnt/β-catenin signaling through BTRC.

Single‑cell sequencing, genetics, and epigenetics reveal mesenchymal stem cell senescence in osteoarthritis (Review)

Osteoarthritis (OA) is a chronic joint disease characterized by articular cartilage degeneration, secondary bone hyperplasia, inadequate extracellular matrix synthesis and degeneration of articular cartilage. Mesenchymal stem cells (MSCs) can self‑renew and undergo multidirectional differentiation; they can differentiate into chondrocytes. Aging MSCs have a weakened ability to differentiate, and release various pro‑inflammatory cytokines, which may contribute to OA progression; the other mechanism contributing to OA is epigenetic regulation (for instance, DNA methylation, histone modification and regulation of non‑coding RNA). Owing to the self‑renewal and differentiation ability of MSCs, various MSC‑based exogenous cell therapies have been developed to treat OA. The efficacy of MSC‑based therapy is mainly attributed to cytokines, growth factors and the paracrine effect of exosomes. Recently, extensive studies have been conducted on MSC‑derived exosomes. Exosomes from MSCs can deliver a variety of DNA, RNA, proteins and lipids, thereby facilitating MSC migration and cartilage repair. Therefore, MSC‑derived exosomes are considered a promising therapy for OA. The present review summarized the association between MSC aging and OA in terms of genetics and epigenetics, and characteristics of MSC‑derived exosomes, and the mechanism to alleviate OA cartilage damage.

Stimulating factors for regulation of osteogenic and chondrogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs), distributed in many tissues in the human body, are multipotent cells capable of differentiating in specific directions. It is usually considered that the differentiation process of MSCs depends on specialized external stimulating factors, including cell signaling pathways, cytokines, and other physical stimuli. Recent findings have revealed other underrated roles in the differentiation process of MSCs, such as material morphology and exosomes. Although relevant achievements have substantially advanced the applicability of MSCs, some of these regulatory mechanisms still need to be better understood. Moreover, limitations such as long-term survival in vivo hinder the clinical application of MSCs therapy. This review article summarizes current knowledge regarding the differentiation patterns of MSCs under specific stimulating factors.

Co-regulation of Sox9 and TGFβ1 transcription factors in mesenchymal stem cells regenerated the intervertebral disc degeneration

Background

Intervertebral disc (IVD) shows aging and degenerative changes earlier than any other body connective tissue. Its repair and regeneration provide a considerable challenge in regenerative medicine due to its high degree of infrastructure and mechanical complexity. Mesenchymal stem cells, due to their tissue resurfacing potential, represent many explanatory pathways to regenerate a tissue breakdown.

Methods

This study was undertaken to evaluate the co-regulation of Sox9 and TGFβ1 in differentiating human umbilical cord mesenchymal stem cells (hUC-MSC) into chondrocytes. The combinatorial impact of Sox9 and TGFβ1 on hUC-MSCs was examined in vitro by gene expression and immunocytochemical staining. In in vivo, an animal model of IVD degeneration was established under a fluoroscopic guided system through needle puncture of the caudal disc. Normal and transfected MSCs were transplanted. Oxidative stress, pain, and inflammatory markers were evaluated by qPCR. Disc height index (DHI), water content, and gag content were analyzed. Histological examinations were performed to evaluate the degree of regeneration.

Results

hUC-MSC transfected with Sox9+TGFβ1 showed a noticeable morphological appearance of a chondrocyte, and highly expressed chondrogenic markers (aggrecan, Sox9, TGFβ1, TGFβ2, and type II collagens) after transfection. Histological observation demonstrated that cartilage regeneration, extracellular matrix synthesis, and collagen remodeling were significant upon staining with H&E, Alcian blue, and Masson's trichrome stain on day 14. Additionally, oxidative stress, pain, and inflammatory markers were positively downregulated in the animals transplanted with Sox9 and TGFβ1 transfected MSCs.

Conclusion

These findings indicate that the combinatorial effect of Sox9 and TGFβ1 substantially accelerates the chondrogenesis in hUC-MSCs. Cartilage regeneration and matrix synthesis were significantly enhanced. Therefore, a synergistic effect of Sox9 and TGFβ1 could be an immense therapeutic combination in the tissue engineering of cartilaginous joint bio-prostheses and a novel candidate for cartilage stabilization.

rno-miR-90 promotes chondrogenic differentiation of bone marrow mesenchymal stem cells by targeting SPARC-related modular calcium binding 2

Bone marrow mesenchymal stem cells (BMSCs) have the ability to differentiate into chondrocytes. In the differentiation of BMSCs into chondrocytes, micro-RNAs (miRNAs) play an important role. rno-miR-90 is a new miRNA discovered by our research team, and its role in chondrogenic differentiation of BMSCs is unknown. This study aimed to investigate whether rno-miR-90 could promote chondrogenic differentiation of BMSCs by regulating secreted protein acidic and rich in cysteine-related modular calcium binding 2 (Smoc2). First, BMSCs chondroblast differentiation was successfully induced in vitro by classical induction method of transforming growth factor (TGF)-β3. On this basis, we transfected rno-miR-90 mimic and inhibitor, and confirmed that rno-miR-90 mimic could promote the differentiation of BMSCs into chondrocytes by real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. In addition, we demonstrated that Smoc2 was a target gene of rno-miR-90 by dual-luciferase reporter assay, and confirmed that rno-miR-90 mimic could inhibit the expression of Smoc2 by RT-qPCR and western blotting. In order to further prove the targeting relationship between rno-miR-90 and Smoc2, we constructed three interfering fragments of Smoc2, and proved that silencing Smoc2 could promote the differentiation of BMSCs into chondrocytes at the transcriptional and protein levels. Finally, we constructed a carrier scaffold for ectopic chondrogenic differentiation in vivo, and confirmed that rno-miR-90 mimic and siSmoc2 could promote chondrogenic differentiation of BMSCs by Alcian blue staining and immunohistochemistry. In summary, our results suggested that rno-miR-90 could promote chondrogenic differentiation of BMSCs by down-regulating the expression of Smoc2. rno-miR-90 mimic and Smoc2 may be therapeutic targets of osteoarthritis.

MiR-362-5p inhibits cartilage repair in osteoarthritis via targeting plexin B1

BACKGROUND AND OBJECTIVES

Chondrogenesis of bone marrow mesenchymal stem cells (BMSCs) exerts great function during the pathogenesis of osteoarthritis (OA). Studies have reported the association of plexin B1 (PLXNB1) with OA pathogenesis. In this study, the upstream mechanism and function of PLXNB1 in this disease were explored.

METHODS

Flow cytometry was applied to test BMSC characterization. Chondrogenic differentiation of BMSCs was evaluated by Alcian blue staining. The expression of PLXNB1, miR-362-5p, miR-501-5p, miR-1827, miR-500-5p was measured using RT-qPCR analysis. The protein levels of PLXNB1, Aggrecan, and Silent information regulator factor 2-related enzyme 1 (SIRT1) were determined by western blotting. Binding relationship between miR-362-5p and PLXNB1 was confirmed using bioinformatics analysis and luciferase reporter assay. The in vivo model of OA was established in Sprague-Dawley rats which received medial meniscus instability surgery. For histopathological examination, cartilage tissues in the knee joint of rats were stained with hematoxylin and eosin. Micro-CT analysis was employed to observe the changes of morphometric indices including average trabecular separation, average trabecular thickness, and bone volume fraction.

RESULTS

BMSCs were identified to possess the characteristics of mesenchymal stem cells. PLXNB1 was observed to be highly expressed during chondrogenic differentiation of BMSCs and PLXNB1 overexpression promoted BMSC chondrogenic differentiation. Mechanically, PLXNB1 was targeted by miR-362-5p. In rescue assays, miR-362-5p reversed the effects of PLXNB1 on chondrogenic differentiation of BMSCs. In the in vivo experiments, upregulated PLXNB1 expression alleviated joint injury of OA rats. Additionally, overexpressed miR-362-5p and downregulated PLXNB1 expression levels were detected in OA rats.

CONCLUSION

MiR-362-5p promotes OA progression by suppressing PLXNB1.

MiR-145-5p restrains chondrogenic differentiation of synovium-derived mesenchymal stem cells by suppressing TLR4

Osteoarthritis (OA) is a progressive degeneration of articular cartilage with involvement of synovial membrane, and subchondral bone. Recently, cell-based therapies, including the application of stem cells such as mesenchymal stem cells (MSCs), have been introduced for restoration of the articular cartilage. Toll-like receptors (TLRs) were reported to participate in OA progression and MSC chondrogenesis. Here, the role and molecular mechanism of toll like receptor 4 (TLR4) in chondrogenic differentiation of synovium-derived MSCs (SMSCs) were investigated. Molecular markers (CD44, CD90, CD45 and CD14) on SMSC surfaces were identified by flow cytometry. Multi-potential differentiation capacities of SMSCs for chondrogenesis, adipogenesis and osteogenesis were examined by Alcian blue, oil red O and Alizarin red staining, respectively. TLR4 and miR-145-5p levels in SMSCs were assessed using RT-qPCR. The protein expression of TGFB3, Col II, SOX9 and Aggrecan in SMSCs was tested by western blotting. Cytokine secretions were analyzed with ELISA for IL-1β and IL-6. Intracellular NAD⁺ content and NAD⁺/NADH ratio were assessed. The interaction between miR-145-5p and TLR4 was confirmed by RNA pulldown and luciferase reporter assays. In this study, SMSCs were identified to have immunophenotypic characteristics of MSCs. TLR4 knockdown inhibited chondrogenic and osteogenic differentiation of SMSCs. Mechanistically, TLR4 was targeted by miR-145-5p in SMSCs. Moreover, TLR4 elevation offset the inhibitory impact of miR-145-5p upregulation on chondrogenic differentiation of SMSCs. Overall, miR-145-5p restrains chondrogenesis of SMSCs by suppressing TLR4.

MiR-20a-5p facilitates cartilage repair in osteoarthritis via suppressing mitogen-activated protein kinase kinase kinase 2

Bone marrow mesenchymal stem cell (BMSC) chondrogenic differentiation contributes to the treatment of osteoarthritis (OA). Numerous studies have indicated that microRNAs (miRNAs) regulate the pathogenesis and development of multiple disorders, including OA. Nevertheless, the role of miR-20a-5p in OA remains obscure. Forty male C57BL/6 mice were divided into four groups and were surgically induced OA or underwent sham surgery in the presence or absence of miR-20a-5p. Flow cytometry was implemented to detect surface markers of BMSCs. Reverse transcription quantitative polymerase chain reaction revealed the upregulation of miR-20a-5p during BMSC chondrogenic differentiation. Western blotting displayed that miR-20a-5p inhibition decreased protein levels of cartilage matrix markers but enhanced those of catabolic and hypertrophic chondrocyte markers in BMSCs. Alcian blue staining, hematoxylin‑eosin staining and micro-CT revealed that miR-20a-5p inhibition restrained chondrogenic differentiation and miR-20a-5p overexpression promoted the repair of damaged cartilage and subchondral bone, respectively. Luciferase reporter assay identified that mitogen activated protein kinase kinase kinase 2 (Map3k2) was a target of miR-20a-5p in BMSCs. Moreover, the expression of miR-20a-5p and Map3k2 was negatively correlated in murine cartilage tissues. Knocking down Map3k2 could rescue the suppressive influence of miR-20a-5p inhibition on chondrogenic differentiation of BMSCs. In conclusion, miR-20a-5p facilitates BMSC chondrogenic differentiation and contributes to cartilage repair in OA by suppressing Map3k2.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

miR-520c-3p regulates IL-1β-stimulated human chondrocyte apoptosis and cartilage degradation by targeting GAS2

Background

MicroRNAs (miRNAs) have been shown to be associated with osteoarthritis (OA) progression. This study aimed to explore the role of miR-520c-3p in OA progression.

Methods

Expression levels of miR-520c-3p and Growth arrest-specific 2 (GAS2) were detected using quantitative real-time PCR. The proliferation and apoptosis of cells were measured using cell counting kit 8 (CCK8) assay and flow cytometry. Furthermore, the protein levels of apoptosis-related markers, extracellular degradation markers, inflammatory response markers, and GAS2 were tested using quantitative real-time polymerase chain reaction (RT-PCR) and western blot (WB) analysis. In addition, the interaction between miR-520c-3p and GAS2 was examined using dual luciferase reporter assay.

Results

GAS2 was highly expressed, and miR-520c-3p was lowly expressed in OA cartilage tissues. miR-520c-3p could promote the proliferation and inhibit the apoptosis and inflammation of OA chondrocytes. miR-520c-3p could be sponged by GAS2, and its inhibitor could reverse the regulation of GAS2 on the biological functions of OA chondrocytes. GAS2 was a target of miR-520c-3p, which was identified by bioinformatic analysis and dual-luciferase reporter assay. Overexpression of GAS2 could inhibit the proliferation and promoted the apoptosis and inflammation of OA chondrocytes.

Conclusion

Our data showed that miR-520c-3p might regulate the GAS2 to inhibit the progression of OA.

CircATRNL1 protects against osteoarthritis by targeting miR-153-3p and KLF5

BACKGROUND

Osteoarthritis (OA) is characterized by chondrocyte injury. Circular RNAs (circRNAs) are involved in the pathogenesis of various diseases, including OA. The purpose of this study was to determine the potential role of circATRNL1 in OA pathology in vitro.

METHODS

Human chondrocytes were isolated and treated with interleukin-1 beta (IL-1β) to mimic OA in vitro. High-throughput RNA sequencing was performed to identify differentially expressed circRNAs, miRNAs and mRNAs between IL and 1β-treated chondrocytes and normal chondrocytes. The expression of circATRNL1, miR-153-3p and KLF5 was measured using quantitative real-time polymerase chain reaction (qRT-PCR). For functional analyses, cell apoptosis was assessed using a flow cytometry assay. Extracellular matrix (ECM) degradation was monitored by measuring the levels of ECM-associated proteins by Western blot. The potential target miRNAs of circATRNL1 were screened by bioinformatics analysis and verified by dual-luciferase reporter assay.

RESULTS

The expression of circATRNL1 was decreased in IL-1β-treated chondrocytes. CircATRNL1 overexpression ameliorated cell apoptosis and ECM degradation, which were promoted by IL-1β treatment. Mechanistic analysis revealed that circATRNL1 directly targeted miR-153-3p and that miR-153-3p could reverse the inhibitory effects of circATRNL1 overexpression on inflammatory responses, cell apoptosis and ECM degradation. KLF5 is a target of miR-153-3p.

CONCLUSION

Taken together, the results in this study suggested that circATRNL1 might ameliorate the development and progression of OA through regulating miR-153-3p/KLF5 axis. Our study increased the understanding of circRNAs as therapeutic targets in the treatment of OA.