miR-26b modulates OA induced BMSC osteogenesis through regulating GSK3β/β-catenin pathway

Mechanism of KDM5A-mediated H3K4me3 modification in the osteogenic differentiation of mesenchymal stem cells in steroid-induced osteonecrosis of the femoral head

OBJECTIVES

Steroid-induced osteonecrosis of the femoral head (SONFH) is characterized by impaired osteogenesis in bone marrow mesenchymal stem cells (BMSCs). This study investigates the role of lysine-specific demethylase 5A (KDM5A) in SONFH to identify potential therapeutic targets.

METHODS

Human BMSCs were isolated and characterized for cell surface markers and differentiation capacity. A SONFH cell model was established using dexamethasone treatment. BMSCs were transfected with KDM5A overexpression vectors or si-KDM5A, and the expression of KDM5A, miR-107, runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and osteopontin (OPN) was assessed. Alizarin red staining was used to observe mineralization nodules, while alkaline phosphatase activity and cell viability were measured. The enrichment of KDM5A and histone 3 lysine 4 trimethylation (H3K4me3) on the promoters of RUNX2, OCN, and OPN was analyzed. The binding between miR-107 and KDM5A 3'UTR was validated, and the combined effect of miR-107 overexpression and KDM5A overexpression on BMSC osteogenic differentiation was evaluated.

RESULTS

KDM5A was upregulated in BMSCs from SONFH. Inhibition of KDM5A promoted osteogenic differentiation of BMSCs, associated with increased RUNX2, OCN, and OPN promoters. KDM5A bound to the promoters of RUNX2, OCN, and OPN, leading to reduced H3K4me3 levels and downregulation of their expression. Overexpression of miR-107 inhibited KDM5A and enhanced BMSC osteogenic differentiation.

CONCLUSION

KDM5A negatively regulates BMSC osteogenic differentiation by modulating H3K4me3 levels on the promoters of key osteogenic genes. miR-107 overexpression counteracts the inhibitory effect of KDM5A on osteogenic differentiation. These findings highlight the potential of targeting the KDM5A/miR-107 axis for SONFH therapy.

Targeting WNT signalling pathways as new therapeutic strategies for osteoarthritis

Osteoarthritis (OA) is a highly prevalent chronic joint disease and the leading cause of disability. Currently, no drugs are available to control joint damage or ease the associated pain. The wingless-type (WNT) signalling pathway is vital in OA progression. Excessive activation of the WNT signalling pathway is pertinent to OA progression and severity. Therefore, agonists and antagonists of the WNT pathway are considered potential drug candidates for OA treatment. For example, SM04690, a novel small molecule inhibitor of WNT signalling, has demonstrated its potential in a recent phase III clinical trial as a disease-modifying osteoarthritis drug (DMOAD). Therefore, targeting the WNT signalling pathway may be a distinctive approach to developing particular agents helpful in treating OA. This review aims to update the most recent progress in OA drug development by targeting the WNT pathway. In this, we introduce WNT pathways and their crosstalk with other signalling pathways in OA development and highlight the role of the WNT signalling pathway as a key regulator in OA development. Several articles have reviewed the Wnt pathway from different aspects. This candid review provides an introduction to WNT pathways and their crosstalk with other signalling pathways in OA development, highlighting the role of the WNT signalling pathway as a key regulator in OA development with the latest research. Particularly, we emphasise the state-of-the-art in targeting the WNT pathway as a promising therapeutic approach for OA and challenges in their development and the nanocarrier-based delivery of WNT modulators for treating OA.

Differentiation of osteoblasts: the links between essential transcription factors

Osteoblasts, cells derived from mesenchymal stem cells (MSCs) in the bone marrow, are cells responsible for bone formation and remodeling. The differentiation of osteoblasts from MSCs is triggered by the expression of specific genes, which are subsequently controlled by pro-osteogenic pathways. Mature osteoblasts then differentiate into osteocytes and are embedded in the bone matrix. Dysregulation of osteoblast function can cause inadequate bone formation, which leads to the development of bone disease. Various key molecules are involved in the regulation of osteoblastogenesis, which are transcription factors. Previous studies have heavily examined the role of factors that control gene expression during osteoblastogenesis, both in vitro and in vivo. However, the systematic relationship of these transcription factors remains unknown. The involvement of ncRNAs in this mechanism, particularly miRNAs, lncRNAs, and circRNAs, has been shown to influence transcriptional factor activity in the regulation of osteoblast differentiation. Here, we discuss nine essential transcription factors involved in osteoblast differentiation, including Runx2, Osx, Dlx5, β-catenin, ATF4, Ihh, Satb2, and Shn3. In addition, we summarize the role of ncRNAs and their relationship to these essential transcription factors in order to improve our understanding of the transcriptional regulation of osteoblast differentiation. Adequate exploration and understanding of the molecular mechanisms of osteoblastogenesis can be a critical strategy in the development of therapies for bone-related diseases.Communicated by Ramaswamy H. Sarma.

Unveiling Mesenchymal Stem Cells' Regenerative Potential in Clinical Applications: Insights in miRNA and lncRNA Implications

It is now widely recognized that mesenchymal stem cells (MSCs) possess the capacity to differentiate into a wide array of cell types. Numerous studies have identified the role of lncRNA in the regulation of MSC differentiation. It is important to elucidate the role and interplay of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) in the regulation of signalling pathways that govern MSC function. Furthermore, miRNAs and lncRNAs are important clinical for innovative strategies aimed at addressing a wide spectrum of existing and emerging disease. Hence it is important to consider their impact on MSC function and differentiation. Examining the data available in public databases, we have collected the literature containing the latest discoveries pertaining to human stem cells and their potential in both fundamental research and clinical applications. Furthermore, we have compiled completed clinical studies that revolve around the application of MSCs, shedding light on the opportunities presented by harnessing the regulatory potential of miRNAs and lncRNAs. This exploration of the therapeutic possibilities offered by miRNAs and lncRNAs within MSCs unveils exciting prospects for the development of precision therapies and personalized treatment approaches. Ultimately, these advancements promise to augment the efficacy of regenerative strategies and produce positive outcomes for patients. As research in this field continues to evolve, it is imperative to explore and exploit the vast potential of miRNAs and lncRNAs as therapeutic agents. The findings provide a solid basis for ongoing investigations, fuelling the quest to fully unlock the regenerative potential of MSCs.

Circular RNA-FK501 binding protein 51 boosts bone marrow mesenchymal stem cell proliferation and osteogenic differentiation via modulating microRNA-205-5p/Runt-associated transcription factor 2 axis

OBJECTIVE

Osteogenesis is the key process of bone homeostasis differentiation. Numerous studies have manifested that circular RNA (circRNA) is a critical regulator of osteogenesis. The research was to explore circRNA-mediated mechanisms in osteogenesis.

METHODS

Bone marrow mesenchymal stem cells (BMSCs) were cultured and induced to osteogenic differentiation (OD). Then, oe-circ-FKBP5, oe-NC, si-circ-FKBP5, si-NC, miR-205-5p mimic, mimic NC, miR-205-5p inhibitor, inhibitor NC, sh-RUNX2, or sh-NC were transfected into BMSCs. Alkaline phosphatase (ALP) activity was detected by ALP staining, cell mineralization was detected by alizarin red staining, cell proliferation was detected by CCK-8, and cell apoptosis was detected by flow cytometry. Then, the expression of circ-FKBP5, miR-205-5p, RUNX2 and osteogenic marker genes was detected by RT-qPCR, and the expression of RUNX2 protein was detected by Western blot. Finally, the targeting relationship between miR-205-5p and circ-FKBP5 or RUNX2 was verified by bioinformation website analysis and dual luciferase reporter gene detection.

RESULTS

Circ-FK501 binding protein 51 (FKBP5) was distinctly elevated during OD of BMSCs. Elevated circ-FKBP5 boosted the proliferation and OD, as well as expression of osteogenic marker genes while reduced apoptosis of BMSCs. Down-regulation of circ-FKBP5 inhibited BMSCs proliferation, OD and osteogenic marker gene expression, and promoted apoptosis of BMSCs. Subsequently, circ-FKBP5 combined with miR-205-5p and constrained miR-205-5p expression. Silenced miR-205-5p boosted proliferation, OD, and expression of osteogenic marker genes and suppressed apoptosis of BMSCs. However, up-regulation of miR-205-5p inhibited BMSC proliferation, OD and osteogenic marker gene expression, and promoted apoptosis. Additionally, miR-205-5p targeted Runt-associated transcription factor 2 (RUNX2). Repression of RUNX2 turned around the effect of circ-FKBP5 overexpression on BMSCs.

CONCLUSION

In brief, circ-FKBP5 boosted BMSC proliferation and OD by mediating the miR-205-5p/RUNX2 axis.

Baicalin inhibits hepatocellular carcinoma cell growth and metastasis by suppressing ROCK1 signaling

Hepatocellular carcinoma (HCC) is a common malignancy affecting many people worldwide. Baicalin is a flavonoid extracted from the dried root of Scutellaria baicalensis Georgi. It can effectively inhibit the occurrence and development of HCC. Nonetheless, the mechanism through which Baicalin inhibits HCC growth and metastasis remain unknown. This work discovered that Baicalin inhibited HCC cell proliferation, invasion, metastasis while inducing cell cycle arrest at the G0/G1 phase and apoptosis. In vivo HCC xenograft results indicated that Baicalin inhibited HCC growth. Western blotting analysis indicated that Baicalin suppressed the expressions of ROCK1, p-GSK-3β, and β-catenin, whereas it up-regulated the expressions of GSK-3β and p-β-catenin. Baicalin also reduced the expressions of Bcl-2, C-myc, Cyclin D1, MMP-9, and VEGFA, while increasing the expression of Bax. Molecular docking revealed that Baicalin docked in the binding site of the ROCK1 agonist, with a binding energy of -9 kcal/mol between the two. In addition, lentivirus-mediated suppression of ROCK1 expression improved the inhibitory effect of Baicalin on the proliferation, invasion, and metastasis of HCC and the expression of proteins associated with ROCK1/GSK-3β/β-catenin signaling pathway. Moreover, restoring ROCK1 expression decreased the anti-HCC efficacy of Baicalin. These findings suggest that Baicalin may decrease HCC proliferation and metastasis by suppressing ROCK1/GSK-3β/β-catenin signaling.

Circulating and extracellular vesicle-derived microRNAs as biomarkers in bone-related diseases

MicroRNAs (miRNA) are small non-coding RNA molecules that regulate posttranscriptional gene expression by repressing messengerRNA-targets. MiRNAs are abundant in many cell types and are secreted into extracellular fluids, protected from degradation by packaging in extracellular vesicles. These circulating miRNAs are easily accessible, disease-specific and sensitive to small changes, which makes them ideal biomarkers for diagnostic, prognostic, predictive or monitoring purposes. Specific miRNA signatures can be reflective of disease status and development or indicators of poor treatment response. This is especially important in malignant diseases, as the ease of accessibility of circulating miRNAs circumvents the need for invasive tissue biopsy. In osteogenesis, miRNAs can act either osteo-enhancing or osteo-repressing by targeting key transcription factors and signaling pathways. This review highlights the role of circulating and extracellular vesicle-derived miRNAs as biomarkers in bone-related diseases, with a specific focus on osteoporosis and osteosarcoma. To this end, a comprehensive literature search has been performed. The first part of the review discusses the history and biology of miRNAs, followed by a description of different types of biomarkers and an update of the current knowledge of miRNAs as biomarkers in bone related diseases. Finally, limitations of miRNAs biomarker research and future perspectives will be presented.

LncRNA LINC00205 stimulates osteoporosis and contributes to spinal fracture through the regulation of the miR-26b-5p/KMT2C axis

BACKGROUND

Osteoporosis (OP) is a common bone disease marked by decreased bone strength. Increasing evidence suggests that long non-coding RNA (lncRNAs) play important roles in the occurrence and progression of OP. This study aimed to investigate the role and mechanism of LINC00205 in the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and OP.

METHODS

Bone tissue samples were obtained from healthy controls and patients with osteoporosis with a spinal fracture (OP-Frx) or without a spinal fracture (OP-no-Frx). HMSCs were cultured and induced to undergo osteogenic differentiation. The expression of LINC00205, lysine (K)-specific methyltransferase 2C (KMT2C), and miR-26b-5p in bone tissues and cells was evaluated using western blotting and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). The effects of LINC00205, miR-26b-5p, and KMT2C on calcium deposition, alkaline phosphatase (ALP) activity, and mRNA levels of the osteogenic differentiation marker genes [ALP, osteocalcin (OCN), and runt-related transcription factor 2 (RUNX2)] were investigated using alizarin red S staining, an ALP activity assay, and qRT-PCR, respectively. Dual-luciferase reporter assay was performed to ascertain the binding relationship between miR-26b-5p and LINC00205/KMT2C.

RESULTS

LINC00205 and KMT2C were upregulated in patients with OP-Frx and OP-no-Frx, whereas miR-26b-5p was downregulated. Furthermore, LINC00205 and KMT2C expression decreased, whereas that of miR-26b-5p increased over time from day 7 to 21 of the osteogenic differentiation of hMSCs. The knockdown of LINC00205 and KMT2C significantly increased ALP activity, calcium deposition, and the expression of RUNX2, ALP, and OCN. In contrast, the inhibition of miR-26b-5p yielded the opposite result. These data suggest that LINC00205 inhibits the osteogenic differentiation of hMSCs by modulating the miR-26b-5p/KMT2C signaling axis.

CONCLUSION

LINC00205 promotes OP and is involved in spinal fractures. LINC00205 is also a potential negative regulator of the osteogenic differentiation of hMSCs.

Network regulatory mechanism of ncRNA on the Wnt signaling pathway in osteoporosis

Non-coding RNA (ncRNA) is a type of non-protein-coding RNA molecule transcribed from the genome which performs broad regulation of a variety of biological functions in human cells. The Wnt signaling pathway is highly conserved in multicellular organisms, playing an important role in their growth and development. Increasing evidence suggests that ncRNA can regulate cell biological function, enhance bone metabolism, and maintain normal bone homeostasis by interacting with the Wnt pathway. Studies have also demonstrated that the association of ncRNA with the Wnt pathway may be a potential biomarker for the diagnosis, evaluation of prognosis, and treatment of osteoporosis. The interaction of ncRNA with Wnt also performs an important regulatory role in the occurrence and development of osteoporosis. Targeted therapy of the ncRNA/Wnt axis may ultimately be the preferred choice for the treatment of osteoporosis in the future. The current article reviews the mechanism of the ncRNA/Wnt axis in osteoporosis and reveals the relationship between ncRNA and Wnt, thereby exploring novel molecular targets for the treatment of osteoporosis and providing theoretical scientific guidance for its clinical treatment.

MiR-218-5p-dependent SOCS3 downregulation increases osteoblast differentiation inpostmenopausal osteoporosis

BACKGROUND

Postmenopausal osteoporosis (POP) is a prevalent skeletal disease among elderly women. Previous study indicated that suppressor of cytokine signaling 3 (SOCS3) participates in the regulation of bone marrow stromal cell (BMSC) osteogenesis. Here, we further investigated the exact function and mechanism of SOCS3 in POP progression.

METHODS

BMSCs were isolated from Sprague-Dawley rats and treated with Dexamethasone (Dex). Alizarin Red staining and ALP activity assays were applied to assess the osteogenic differentiation of rat BMSCs under the indicated conditions. Osteogenic genes (ALP, OPN, OCN, COL1) mRNA levels were determined using quantitative RT-PCR. Luciferase reporter assay verified the interaction between SOCS3 and miR-218-5p. Rat models of POP were established in ovariectomized (OVX) rats to detect the in vivo effects of SOCS3 and miR-218-5p.

RESULTS

We found that silencing SOCS3 antagonized the suppressive effects of Dex on the osteogenic differentiation of BMSCs. SOCS3 was found to be targeted by miR-218-5p in BMSCs. The SOCS3 levels were negatively modulated by miR-218-5p in femurs of POP rats. MiR-218-5p upregulation promoted the BMSC osteogenic differentiation, while SOCS3 overexpression reversed the effects of miR-218-5p. Moreover, SOCS3 was highly expressed and miR-218-5p was downregulated in the OVX rat models, and silencing SOCS3 or overexpressing miR-218-5p alleviated POP in OVX rats by promoting osteogenesis.

CONCLUSION

SOCS3 downregulation mediated by miR-218-5p increases osteoblast differentiation to alleviate POP.

LncRNA VPS9D1-AS1 Sponging miR-520a-5p Contributes to the Development of Uterine Corpus Endometrial Carcinoma by Enhancing BIRC5 Expression

The pattern of VPS9D1-AS1 expression and its effects on uterine corpus endometrial carcinoma (UCEC) remained unclear. VPS9D1-AS1, miR-520a-5p, and BIRC5 mRNA levels were quantified by qRT-PCR. Bax, Bcl-2, N-cadherin, E-cadherin, and BIRC5 protein levels were analyzed through western blotting. Cell migration, invasion, proliferation, as well as apoptosis of cells were checked after performing assay for wound-healing, Transwell, cell-counting kit-8 (CCK-8) assay, and western blotting. VPS9D1-AS1 effects on UCEC were observed in nude mice. Through bioinformatics tools, we analyzed the association present among miR-520a-5p, BIRC5, and VPS9D1-AS1 along with RNA immunoprecipitation, and Dual-Luciferase verification reporter analysis. Our findings suggested VPS9D1-AS1 gene expression was up-regulated in both tissues as well as cells of UCEC. VPS9D1-AS1 knockdown suppressed migration, invasion, epithelial-mesenchymal transition (EMT) along with proliferation of UCEC cells, caused in vitro cell apoptosis initiation, and in vivo reduction of tumor growth. Mechanistically, it was verified that VPS9D1-AS1 targeted BIRC5 and caused miR-520a-5p sponging. Inhibitor of miR-520-5p markedly reversed the anti-tumor effects of VPS9D1-AS1 knockdown or BIRC5 knockdown on UCEC progression. Our studies revealed that VPS9D1-AS1 contributed to the UCEC development and progression by binding to miR-520a-5p competitively and inducing BIRC5 expression, indicating that VPS9D1-AS1 might act as a therapeutic target to develop new therapies for UCEC patients.

Jin-Tian-Ge ameliorates ovariectomy-induced bone loss in rats and modulates osteoblastogenesis and osteoclastogenesis in vitro

BACKGROUND

Tiger bone, which had been one of the most famous traditional Chinese medicine for 2000 years, was originate from the skeleton of Panthera tigris L., and had the actions of anti-inflammatory, analgesic, immune-regulatory and promoting healing of bone fracture, and was used for the treatment of osteoporosis and rheumatoid arthritis. Jin-Tian-Ge (JTG), the artificial tiger bone powder, were prepared from skeletons of several farmed animals to substitute the natural tiger bone, and has been used for the treatment of osteoporosis in clinical practice. However, the characteristic and mechanism of action of JTG for the therapy of osteoporosis need to be further evidenced by using modern pharmacological methods. The aim of this work is to investigate the bone-protective effects of JTG, and explore the possible underlying mechanism.

METHODS

Ovariectomy (OVX) rats were orally administrated JTG or estradiol valerate (EV) for 12 weeks. We investigated the pharmacodynamic effects of JTG on anti-bone loss in OVX rats, and also investigated the role of JTG in promoting osteogenesis and inhibiting osteoclast differentiation.

RESULTS

JTG increased the bone mineral density (BMD), improved the bone microarchitecture and biomechanical properties in ovariectomized rast, whereas reversed the bone high turnover in OVX rats as evidenced by serum biochemical markers in OVX rats. JTG increased osteogenic differentiation of BMSCs in vitro, and up-regulated the expression of the key proteins of BMP and Wnt/β-catenin pathways. JTG also inhibited the osteoclastogenesis of BMM as evidenced by the alteration of the TRAP activity, F-actin construction and the expression of nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), c-Fos, Cathepsin K (Ctsk) and matrix metallopeptidase 9 (MMP9) of OCs induced with RANKL and LPS, reduced the expression and phosphorylation of NF-κB in OCs.

CONCLUSIONS

JTG prevented bone loss in OVX rats and increased osteogenic differentiation of BMSCs through regulation of the BMP and Wnt/β-catenin pathway, inhibited osteoclastogenesis by suppressing the NF-κB pathway, suggesting that JTG had the potentials for prevention and treatment of osteoporosis by modulating formation and differentiation of osteoblast and osteoclast.

MicroRNA-26b regulates BMSC osteogenic differentiation of TMJ subchondral bone through β-catenin in osteoarthritis

Temporomandibular joint osteoarthritis (TMJ-OA) is a degenerative disease of the joint. The early manifestations of TMJ-OA are abnormal remodeling of condylar subchondral bone. In bone tissue, bone marrow mesenchymal stem cells (BMSCs) and osteoblasts play important roles in the differentiation and maturation of most hematopoietic cells. MicroRNA-26b (miR-26b) is upregulated during the osteogenesis of BMSCs, and miR-26b overexpression leads to the activation of β-catenin and the enhancement of osteogenesis and cartilage formation. However, the pathologic mechanism remains unclear. In the present study, we used a rat model with OA-like changes in the TMJ induced by experimental unilateral anterior crossbite (UAC) and found that the level of miR-26b was markedly lower in BMSCs from the subchondral bones of UAC rats than in those from sham control rats. MiR-26b overexpression by agomiR-26b increased condylar subchondral bone osteogenesis in UAC rats. Notably, although agomiR-26b primarily affected miR-26b levels in the subchondral bone (but not in cartilage or the synovium), the overexpression of miR-26b in BMSCs in UAC rats largely rescued OA-like cartilage degradation, while the inhibition of miR-26b in BMSCs exacerbated cartilage degradation in UAC rats. We measured the expression levels of β-catenin and related osteogenic and osteoclastic factors after using miR-26b mimics and inhibitors in vivo. Moreover, BMSCs were treated with the β-catenin blocker Wnt-C59 and then transfected with miR-26b mimics or inhibitors. Then, we examined the expression of β-catenin as the direct target of miR-26b. The results of the present study indicate that miR-26b may modulate subchondral bone loss induced by abnormal occlusion and influence the osteogenic differentiation of subchondral BMSCs through β-catenin in the context of TMJ-OA progression.

The roles of N6-methyladenosine methylation in the regulation of bone development, bone remodeling and osteoporosis

N⁶-methyladenosine (m⁶A), a novel epitranscriptomic RNA modification, plays crucial roles in a variety of biological processes and diseases. Recently, there are growing evidence supporting that m⁶A methylation is essential for bone development and homeostasis through the regulation of key genes by regulating RNA stability, localization, turnover and translation efficiency. In this review, we summarized our current understanding of the functional roles of m⁶A methylation and its related regulators in bone development and bone remodeling. These findings will offer new directions and insights on the further investigations of m⁶A methylation in bone biology. Moreover, we also discussed important advances of m⁶A methylation related regulators as potential therapeutic targets, which allows for novel therapeutic strategies on the medications of bone-related diseases including osteoporosis.

Co-Culture of Bone Marrow Mesenchymal Stem Cell (BMSC) and Osteoclasts Regulates Cell Differentiation and Alleviates Osteoporosis by Up-Regulating miR-211

Bone marrow mesenchymal stem cells (BMSCs) can release a large amount of exosomes (EXO) during bone remodeling by osteoclasts. EXO contains miRNA-211, which has a variety of biological effects. However, little is known about whether miR-211 from BMSC-EXO affects the surrounding cells. Therefore, we aim to study the role of miRNA-211 derived from BMSC-EXO in regulating osteoclasts differentiation. Macrophage colony stimulating factor (M-CSF) and nuclear factor kappa B receptor activator (RANKL) were used to stimulate bone marrow macrophages (BMM) to obtain osteoclasts, which were treated with BMSC-EXO or LPS followed by analysis of osteoclast-related genes expression by PCR, ROS release by flow cytometry, actin ring formation by immunofluorescence, and osteoclast differentiation by anti-tartrate acid phosphatase (TRAP) staining. Finally, an in vivo experiment was conducted to verify BMSC-EXO’s effect on osteoporosis. BMSC-EXO significantly inhibited RNAKL-induced osteoclast differentiation of BMMs. During osteoclasts formation, BMSC-EXO inhibited ROS production induced by RANKL and the subsequent activation of NF-κB signaling pathway induced by ROS. In addition, BMSC-EXO significantly down-regulated the osteoclast genes including nuclear factor, cytoplasmic 1 (NFATc1), C-fos, tartrate-resistant acid phosphatase (TRAP) and osteoclast-associated immunoglobulin-like receptor (OSCAR) in activated T cells. BMSC-EXO inhibited ROS release by promoting miR-211 expression, thereby inhibiting the NF-κB signaling and ultimately participating in osteoclasts differentiation. In LPS-induced mouse osteoporosis models, BMSC-EXO inhibited LPS-induced bone loss and exerted a protective effect. In conclusion, microRNA-211 derived from BMSC-EXO can regulate osteoclasts differentiation, suggesting that it might be used as a potential approach for treating osteoporosis.

The Regulation of Collagen Processing by miRNAs in Disease and Possible Implications for Bone Turnover

This article describes several recent examples of miRNA governing the regulation of the gene expression involved in bone matrix construction. We present the impact of miRNA on the subsequent steps in the formation of collagen type I. Collagen type I is a main factor of mechanical bone stiffness because it constitutes 90-95% of the organic components of the bone. Therefore, the precise epigenetic regulation of collagen formation may have a significant influence on bone structure. We also describe miRNA involvement in the expression of genes, the protein products of which participate in collagen maturation in various tissues and cancer cells. We show how non-collagenous proteins in the extracellular matrix are epigenetically regulated by miRNA in bone and other tissues. We also delineate collagen mineralisation in bones by factors that depend on miRNA molecules. This review reveals the tissue variability of miRNA regulation at different levels of collagen maturation and mineralisation. The functionality of collagen mRNA regulation by miRNA, as proven in other tissues, has not yet been shown in osteoblasts. Several collagen-regulating miRNAs are co-expressed with collagen in bone. We suggest that collagen mRNA regulation by miRNA could also be potentially important in bone metabolism.

miRNAs Related to Different Processes of Fracture Healing: An Integrative Overview

Fracture healing is a complex, dynamic process that is directed by cellular communication and requires multiple cell types, such as osteoblasts, osteoclasts, and immune cells. Physiological fracture healing can be divided into several phases that consist of different processes, such as angiogenesis, osteogenesis, and bone resorption/remodelling. This is needed to guarantee proper bone regeneration after fracture. Communication and molecular regulation between different cell types and within cells is therefore key in successfully orchestrating these processes to ensure adequate bone healing. Among others, microRNAs (miRNAs) play an important role in cellular communication. microRNAs are small, non-coding RNA molecules of ~22 nucleotides long that can greatly influence gene expression by post-transcriptional regulation. Over the course of the past decade, more insights have been gained in the field of miRNAs and their role in cellular signalling in both inter- and intracellular pathways. The interplay between miRNAs and their mRNA targets, and the effect thereof on different processes and aspects within fracture healing, have shown to be interesting research topics with possible future diagnostic and therapeutic potential. Considering bone regeneration, research moreover focusses on specific microRNAs and their involvement in individual pathways. However, it is required to combine these data to gain more understanding on the effects of miRNAs in the dynamic process of fracture healing, and to enhance their translational application in research, as well as in the clinic. Therefore, this review aims to provide an integrative overview on miRNAs in fracture healing, related to several key aspects in the fracture healing cascade. A special focus will be put on hypoxia, angiogenesis, bone resorption, osteoclastogenesis, mineralization, osteogenesis, osteoblastogenesis, osteocytogenesis, and chondrogenesis.

Knockdown of long non-coding RNA HOTAIR promotes bone marrow mesenchymal stem cell differentiation by sponging microRNA miR-378g that inhibits nicotinamide N-methyltransferase

Osteoporosis (OP) is associated with a serious social and economic burden. Recent studies have shown that the differential expression of long non-coding RNAs (lncRNAs) is closely related to OP. However, the specific molecular mechanism of HOX transcript antisense intergenic RNA (HOTAIR) remains to be elucidated.The expression of HOTAIR and miR-378g in OP patients was detected using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Bone marrow mesenchymal stem cells (BMSCs) were isolated and cultured, and osteogenic differentiation was induced. Alkaline phosphatase (ALP) and Runt-related transcription factor 2 (RUNX2) were detected by qRT-PCR, ELISA, and Western blotting. Calcium deposition was measured using Alizarin red s (ARS) staining. Molecular interactions between HOTAIR, miR-378g, and nicotinamide N-methyltransferase (NNMT) were detected using a dual-luciferase reporter assay.HOTAIR expression was upregulated and miR-378g level was downregulated in OP patients. HOTAIR expression decreased during the osteogenic differentiation of BMSCs. Silencing HOTAIR or NNMT reduced ALP and RUNX2 levels and promoted calcium deposition. The overexpression of HOTAIR or interference with miR-378g inhibited the osteogenic differentiation of BMSCs. HOTAIR negatively regulates miR-378g by targeting NNMT.HOTAIR is an miR-378g sponge that targets NNMT, inhibits the osteogenic differentiation of BMSCs, and provides a valuable target for the treatment of OP.

The Interaction between microRNAs and the Wnt/β-Catenin Signaling Pathway in Osteoarthritis

Osteoarthritis (OA) is a chronic disease affecting the whole joint, which still lacks a disease-modifying treatment. This suggests an incomplete understanding of underlying molecular mechanisms. The Wnt/β-catenin pathway is involved in different pathophysiological processes of OA. Interestingly, both excessive stimulation and suppression of this pathway can contribute to the pathogenesis of OA. microRNAs have been shown to regulate different cellular processes in different diseases, including the metabolic activity of chondrocytes and osteocytes. To bridge these findings, here we attempt to give a conclusive overview of microRNA regulation of the Wnt/β-catenin pathway in bone and cartilage, which may provide insights to advance the development of miRNA-based therapeutics for OA treatment.

miR-129-5p in exosomes inhibits diabetes-associated osteogenesis in the jaw via targeting FZD4

Diabetes mellitus (DM) influence induces poor osseointegration. The osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is a critical factor in successful dental implants. Certain microRNAs play important roles during bone development, and others are deregulated in diabetes. This study investigated the roles of miR-129-5p in the osteoblast differentiation regulation. Exosomes containing miR-129-5p inhibited the osteoblast differentiation and was found in the blood of DM rats. The BMSCs isolated from the jaw of rats were used to detect the miR-129-5p expression. Frizzled (FZD) proteins function as receptors for WNT ligands. The FZD4 was the target of miR-129-5p in dual luciferase assay and Western blot. The miR-129-5p inhibited osteoblast differentiation and decreased the osteoblast markers. The exosomes isolated from the blood of DM rats showed more miR-129-5p level. Results suggested that the exosomes containing miR-129-5p maybe regulators of BMSCs in jaw. The collected exosomes containing miR-129-5p showed the inhibition effect in osteoblast differentiation and decreased the expression osteoblastic markers by targeting FZD4/β-catenin signaling pathway. Therefore, the exosomes containing miR-129-5p in DM rats inhibits osteoblast differentiation by targeting FZD4/β-catenin pathway.

Circular RNA circ_0000020 promotes osteogenic differentiation to reduce osteoporosis via sponging microRNA miR-142-5p to up-regulate Bone Morphogenetic Protein BMP2

This study was designed to study functions of Circ_0000020 during osteogenic differentiation. First, we used RT-qPCR to detect the expression of Circ_0000020, miR-142-5p and osteogenesis-related genes, whereas western blot analysis detected the expression of osteogenesis markers after the osteogenic differentiation of primary BMSCs isolated from rats. Alkaline phosphatase (ALP) activity and alizarin red Sstaining validated osteoblast phenotypes. Flow cytometry was used to detect cell apoptosis. Sh-Circ_0000020 was used to study the function of Circ_0000020 in osteogenic differentiation of BMSCs. Luciferase assay and RNA immunoprecipitation were used to validate the interaction between Circ_0000020 and miR-142-5p, and BMP2 and miR-142-5p. Co-transfection of miR-142-5p and sh-Circ_0000020 was used to verify the downstream signaling pathway. Circ_0000020 expression was up-regulated during osteogenic differentiation, whereas miR-142-5p expression was significantly decreased. Silencing Circ_0000020 inhibited osteogenic differentiation and promoted apoptosis, and inhibited ALP activity and mineralization ability. Moreover, Circ_0000020 interacts directly with miR-142-5p which binds to the BMP2 3ʹUTR and inhibits its expression. Additionally, co-transfection of miR-142-5p inhibitors and sh-Circ_0000020 rescued down-regulated BMP2, increased the expression osteogenesis-related gene expressions, and thereby rescued the inhibition of osteogenic differentiation induced by Circ_0000020 silencing. Furthermore, co-transfection of miR-142-5p inhibitors and sh-Circ_0000020 reversed Circ_0000020 silencing-induced downregulation of p-Smad1/5/8, Runx2, and Osterix protein levels. Circ_0000020 regulates BMP2 expression through sponging miR-142-5p as ceRNA, thereby positively regulating BMSCs osteogenic differentiation through Circ_0000020/miR-142-5p/BMP2/SMAD-dependent signaling pathway.

BRD4 induces osteogenic differentiation of BMSCs via the Wnt/β-catenin signaling pathway

Bromodomain 4 (BRD4), an important epigenetic regulator, is involved in many bone-related pathologies via promoting osteoclast formation. However, whether and how it participates in the process of osteoblast formation remain unclear. This study aimed to investigate the potential role of BRD4 in osteogenic differentiation of bone marrow stromal cells (BMSCs). Our experiments revealed that an inhibitor of BRD4, JQ1, attenuated osteogenic differentiation of BMSCs. The recombinant adenoviruses for AdBRD4 and AdsiBRD4 could infect BMSCs with high efficiency. Exogenous BRD4 expression potentiated differentiation, and silencing endogenous BRD4 expression decreased it. In addition, the Wnt/β-catenin signaling pathway is known to be important for osteogenic differentiation. Our results showed that AdBRD4 increased the expressions of Wnt3a and β-catenin while AdsiBRD4 decreased the expressions. What's more, the recombinant adenovirus for Adsiβ-catenin, which obviously decreased in β-catenin expression, inhibited BRD4-induced osteogenic differentiation. Conclusion: Our data indicates that the epigenetic reader BRD4 participates in the process of BMSC osteogenic differentiation via the Wnt/β-catenin signaling pathway. This finding may pave the way into further understanding the mechanism of BMSC osteogenic differentiation.

GPR35 regulates osteogenesis via the Wnt/GSK3β/β-catenin signaling pathway

It is well known that osteoporosis is a significant chronic disease with the increase of the aging population. Here, we report that expression of G protein-coupled receptor 35 (GPR35) in bone marrow mesenchymal stem cells (BMSCs) is suppressed in diagnosed osteoporosis patients and osteoporotic mice. The expression of GPR35 on BMSCs is enhanced during osteogenic differentiation. GPR35 knockout suppresses the proliferation and osteogenesis of BMSCs and deteriorates bone mass in both sham-treated and ovariectomized mice. Moreover, GPR35 deficiency reduces β-catenin activity in BMSCs. In contrast, the overexpression of GPR35 contributes to these processes in BMSCs. Finally, using zaprinast, a synthetic GPR35 agonist, we show that zaprinast rescues OVX-induced bone loss and promotes bone generation in mice. Thus, GPR35 may as a new target and its agonist zaprinast may serve as a novel treatment for osteoporosis.

MicroRNAs Modulate Signaling Pathways in Osteogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have been identified in many adult tissues and they have been closely studied in recent years, especially in view of their potential use for treating diseases and damaged tissues and organs. MSCs are capable of self-replication and differentiation into osteoblasts and are considered an important source of cells in tissue engineering for bone regeneration. Several epigenetic factors are believed to play a role in the osteogenic differentiation of MSCs, including microRNAs (miRNAs). MiRNAs are small, single-stranded, non-coding RNAs of approximately 22 nucleotides that are able to regulate cell proliferation, differentiation and apoptosis by binding the 3' untranslated region (3'-UTR) of target mRNAs, which can be subsequently degraded or translationally silenced. MiRNAs control gene expression in osteogenic differentiation by regulating two crucial signaling cascades in osteogenesis: the transforming growth factor-beta (TGF-β)/bone morphogenic protein (BMP) and the Wingless/Int-1(Wnt)/β-catenin signaling pathways. This review provides an overview of the miRNAs involved in osteogenic differentiation and how these miRNAs could regulate the expression of target genes.

The role of microRNAs in bone development

Epigenetic regulation is critical for proper bone development. Evidence from a large body of published literature informs us that microRNAs (miRNAs) are important epigenetic factors that control many aspects of bone development, homeostasis, and repair processes. These small non-coding RNAs function at the post-transcriptional level to suppress expression of specific target genes. Many target genes may be affected by one miRNA resulting in alteration in cellular pathways and networks. Therefore, changes in levels or activity of a specific miRNA (e.g. via genetic mutations, disease scenarios, or by over-expression or inhibition strategies in vitro or in vivo) can lead to substantial changes in cell processes including proliferation, metabolism, apoptosis and differentiation. In this review, Section 1 briefly covers general background information on processes that control bone development as well as the biogenesis and function of miRNAs. In Section 2, we discuss the importance of miRNAs in skeletal development based on findings from in vivo mouse models and human clinical reports. Section 3 focuses on describing more recent data from the last three years related to miRNA regulation of osteoblast differentiation in vitro. Some of these studies also involve utilization of an in vivo rodent model to study the effects of miRNA modulation in scenarios of osteoporosis, bone repair or ectopic bone formation. In Section 4, we provide some recent information from studies analyzing the potential of miRNA-mediated crosstalk in bone and how exosomes containing miRNAs from one bone cell may affect the differentiation or function of another bone cell type. We then conclude by summarizing where the field currently stands with respect to miRNA-mediated regulation of osteogenesis and how information gained from developmental processes can be instructive in identifying potential therapeutic miRNA targets for the treatment of certain bone conditions.

The miR-4739/DLX3 Axis Modulates Bone Marrow-Derived Mesenchymal Stem Cell (BMSC) Osteogenesis Affecting Osteoporosis Progression

Osteoporosis is a complex multifactorial disorder linked to various risk factors and medical conditions. Bone marrow-derived mesenchymal stem cell (BMSC) dysfunction potentially plays a critical role in osteoporosis pathogenesis. Herein, the study identified that miR-4739 was upregulated in BMSC cultures harvested from osteoporotic subjects. BMSCs were isolated from normal and osteoporotic bone marrow tissues and identified for their osteogenic differentiation potential. In osteoporotic BMSCs, miR-4739 overexpression significantly inhibited cell viability, osteoblast differentiation, mineralized nodule formation, and heterotopic bone formation, whereas miR-4739 inhibition exerted opposite effects. Through direct binding, miR-4739 inhibited distal-less homeobox 3 (DLX3) expression. In osteoporotic BMSCs, DLX3 knockdown also inhibited BMSC viability and osteogenic differentiation. Moreover, DLX3 knockdown partially attenuated the effects of miR-4739 inhibition upon BMSCs. Altogether, the miR-4739/DLX3 axis modulates the capacity of BMSCs to differentiate into osteoblasts, which potentially plays a role in osteoporosis pathogenesis. The in vivo and clinical functions of the miR-4739/DLX3 axis require further investigation.

miRNA-187-5p Regulates Osteoblastic Differentiation of Bone Marrow Mesenchymal Stem Cells in Mice by Targeting ICAM1

Osteoporosis (OP) is a common bone metabolic disease, the process of which is fundamentally irreversible. Therefore, the investigation into osteoblastic differentiation of bone marrow mesenchymal stem cells (BMSCs) will provide more clues for OP treatment. In the present study, we found that microRNA-187-5p (miR-187-5p) played a key role on osteoblastic differentiation, which was significantly upregulated during osteogenic differentiation of BMSCs in mice. Moreover, overexpression of miR-187-5p suppressed osteoblastic differentiation of BMSCs through increasing alkaline phosphatase (ALP), matrix mineralization, and levels of Osterix (OSX), and osteopontin (OPN) as well as runt-related transcription factor 2 (Runx2) in vitro. The results in vivo indicated that the upregulation of miR-187-5p enhanced the efficacy of new bone formation in the heterotopic bone formation assay. Luciferase reporter assay and western blot analysis revealed that miR-187-5p was involved in osteogenesis by targeting intracellular adhesion molecule 1 (ICAM-1). Furthermore, ICAM-1 silence inhibited osteoblastic differentiation of BMSCs. Taken together, our results suggested for the first time that miR-187-5p may promote osteogenesis by targeting ICAM-1, and provided a possible therapeutic target for bone metabolic diseases.

The Osteoporosis/Microbiota Linkage: The Role of miRNA

Hundreds of trillions of bacteria are present in the human body in a mutually beneficial symbiotic relationship with the host. A stable dynamic equilibrium exists in healthy individuals between the microbiota, host organism, and environment. Imbalances of the intestinal microbiota contribute to the determinism of various diseases. Recent research suggests that the microbiota is also involved in the regulation of the bone metabolism, and its alteration may induce osteoporosis. Due to modern molecular biotechnology, various mechanisms regulating the relationship between bone and microbiota are emerging. Understanding the role of microbiota imbalances in the development of osteoporosis is essential for the development of potential osteoporosis prevention and treatment strategies through microbiota targeting. A relevant complementary mechanism could be also constituted by the permanent relationships occurring between microbiota and microRNAs (miRNAs). miRNAs are a set of small non-coding RNAs able to regulate gene expression. In this review, we recapitulate the physiological and pathological meanings of the microbiota on osteoporosis onset by governing miRNA production. An improved comprehension of the relations between microbiota and miRNAs could furnish novel markers for the identification and monitoring of osteoporosis, and this appears to be an encouraging method for antagomir-guided tactics as therapeutic agents.

Astragaloside‑IV modulates NGF‑induced osteoblast differentiation via the GSK3β/β‑catenin signalling pathway

Astragaloside (AST) is derived from the Chinese herb Astragalus membranaceus, and studies have demonstrated that it promotes differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). To the best of our knowledge, however, the functions of the component AST-IV in osteogenesis have not previously been elucidated. The present study aimed to verify the effects of AST-IV in osteogenesis. First, the proliferation and differentiation status of human BMSCs incubated with AST-IV were analysed and compared with a control (no AST-IV treatment). In order to determine the involvement of the glycogen synthase kinase (GSK)3β signalling pathway in AST-IV, overexpression and inhibition of GSK3β was induced during incubation of BMSCs with AST-IV. In order to investigate how neuronal growth factor (NGF) contributes to BMSCs differentiation, BMSCs were co-incubated with an anti-NGF antibody and AST IV, and then levels of osteogenesis markers were assessed. The results demonstrated for the first time that AST-IV contributed to BMSCs differentiation. Furthermore, the GSK3β/β-catenin signalling pathway was revealed to be involved in AST-IV-induced osteogenesis; moreover, AST-IV accelerated differentiation by enhancing the expression levels of NGF. In summary, the present study demonstrated that AST-IV promotes BMSCs differentiation, thus providing a potential target for the treatment of osteoporosis.

[The regulatory role of microRNA in osteogenic differentiation of mesenchymal stem cells and its application as a therapeutic target and diagnostic tool in orthopedic diseases]

OBJECTIVE

To summarize the research progress of the regulatory role of microRNA (miRNA) in osteogenic differentiation of mesenchymal stem cells (MSCs) and its application as a therapeutic target and diagnostic tool in orthopedic diseases.

METHODS

The recent literature on the regulation of MSCs osteogenic differentiation by miRNAs was extensively reviewed, and its regulatory mechanism and its application as a therapeutic target and diagnostic tool in orthopedic diseases were reviewed.

RESULTS

miRNAs are small endogenous non-coding RNAs with a length of 20-22 nucleotides, which play an important role in the osteogenic differentiation of MSCs. Osteogenesis begins with the differentiation of MSCs into mature osteoblasts, and each stage of dynamic homeostasis of bone metabolism is associated with the regulation of different miRNAs. miRNAs are regulated from the post-transcriptional level by mRNAs cleavage, degradation, translational repression, or methylation. In addition, current studies suggest that miRNAs can be used as a new diagnostic tool and therapeutic target for orthopedic diseases.

CONCLUSION

Further study on the regulation mechanism of miRNAs will provide more ideas for finding new therapeutic targets and diagnostic tools for orthopedic disease.