MicroRNA-451 blockade promotes osteoblastic differentiation and skeletal anabolic effects by promoting YWHAZ-mediated RUNX2 protein stabilization

miRNA-Based Early Healing Mechanism of Extraction Sockets: miR-190a-5p, a Potential Enhancer of Bone Healing

Objective

Tooth extraction causes a wound with hard and soft tissue defects in the alveolar ridge. Few studies have reported the function of microRNAs (miRNAs) in the healing of extraction sockets. This study used bioinformatics analysis to reveal the possible relevance and role of miRNAs during the early stages following tooth extraction.

Materials and Methods

Socket tissues from beagle dogs (Canis familiaris; two males and two females) were collected 1 and 12 hours after extraction of premolars on both sides of the mandible. miRNA expression was profiled through miRNA sequencing, and hub miRNAs showing characteristic expression patterns were selected and subjected to target enrichment analysis. Alkaline phosphatase (ALP) activity analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were performed to verify the effect of hub miRNA on osteoblast differentiation and bone regeneration in vivo.

Results

Five miRNAs were identified to have consistently high expression levels, with cfa-miR-451 showing the highest expression. Additionally, 20 hub miRNAs were selected as candidates expected to play an important role in the healing process. Pathways, such as the MAPK, axon guidance, TGF-β, and Wnt signaling, were significantly enriched. Among hub miRNAs, miR-190a-5p increased ALP activity and mRNA expression of osteogenic markers and increased new bone formation in vivo.

Conclusions

Our findings suggest that miRNAs may be involved in the earliest stages of socket healing after tooth extraction and can play an important role in moderating the entire socket healing mechanism in the extraction socket.

Contribution of miRNAs and lncRNAs in osteogenesis and related disorders

Non-coding RNAs have been found to regulate several developmental processes among them is osteogenesis. Although these transcripts have several distinct classes, two classes i.e. microRNAs and long non-coding RNAs have attained more attention. These transcripts regulate intramembranous as well as endochondral ossification processes. The effects of microRNAs on osteogenesis are mostly mediated through modulation of Wnt/β-catenin and TGFβ/BMP pathways. Long non-coding RNAs can directly affect expression of these pathways or osteogenic transcription factors. Moreover, they can serve as a molecular sponge for miRNAs. MALAT1/miR-30, MALAt1/miR-214, LEF1-AS1/miR-24-3p, MCF2L-AS1/miR-33a, MSC-AS1/miR-140-5p and KCNQ1OT1/miR-214 are examples of such kind of interaction between lncRNAs and miRNAs in the context of osteogenesis. In the current paper, we explain these two classes of non-coding RNAs in the osteogenesis and related disorders.

microRNA-148a-3p-targeting p300 protects against osteoblast differentiation and osteoporotic bone reconstruction

Aim: This study sets out to investigate the possible effects of miRNA-148a-3p (miR-148a-3p) on osteoblast differentiation and bone remodeling following osteoporosis. Materials & methods: Expression of miR-148a-3p, p300, Nrf2 and differentiation-related proteins (Runx2, Osteocalcin and Col1a1) was examined in the osteoblast MC3T3-E1 cell line, followed by identification of interaction between miR-148a-3p and p300 and between p300 and Nrf2. After ectopic expression and depletion experiments in MC3T3-E1 cells, cell proliferation, osteogenic mineralization and osteogenic differentiation were measured. Ovariectomy-induced osteoporosis mouse models were established to verify function of miR-148a-3p in vivo. Results: miR-148a-3p expression was restrained and p300 and Nrf2 expression was increased during osteoblast differentiation. miR-148a-3p inhibition or p300 upregulation enhanced proliferation and osteogenic differentiation in MC3T3-E1 cells. p300 was targeted by miR-148a-3p. Additionally, miR-148a-3p reduced BMD, bone volume relative to tissue volume ratio, trabecular bone, trabecular thickness and trabecular spacing in ovariectomy mice. Conclusion: Taken together, miR-148a-3p might prevent the osteoblast differentiation and bone remodeling by disrupting p300-dependent Nrf2 pathway activation.

Transcriptome-wide study revealed m6A regulation of embryonic muscle development in Dingan goose (Anser cygnoides orientalis)

BACKGROUND

The number of myofiber is determined during the embryonic stage and does not increase during the postnatal period for birds, including goose. Thus, muscle production of adult goose is pre-determined during embryogenesis. Previous studies show N6-methyladenosine (m6A) is an important regulator for skeletal muscle development of birds and miRNAs play as a co-regulator for the skeletal muscle development in birds. Herein, we sequenced m6A and miRNA transcriptomes to investigate the profiles of m6A and their potential mechanism of regulating breast muscle development in Dingan Goose.

RESULTS

We selected embryonic 21th day (E21) and embryonic 30th day (E30) to investigate the roles of transcriptome-wide m6A modification combining with mRNAs and miRNAs in goose breast muscle development. In this study, m6A peaks were mainly enriched in coding sequence (CDS) and start codon and397 genes were identified as differentially methylated genes (DMGs). GO and KEGG analysis showed that DMGs were highly related to cellular and metabolic process and that most DMGs were enriched in muscle-related pathways including Wnt signaling pathway, mTOR signaling and FoxO signaling pathway. Interestingly, a negative correlation between m6A methylation level and mRNA abundance was found through the analysis of m6A-RNA and RNA-seq data. Besides, we found 26 muscle-related genes in 397 DMGs. We also detected 228 differentially expressed miRNAs (DEMs), and further found 329 genes shared by the target genes of DEMs and DMGs (m6A-miRNA-genes), suggesting a tightly relationship between DEMs and DMGs. Among the m6A-miRNA-genes, we found 10 genes are related to breast muscle development. We further picked out an m6A-miRNA-gene, PDK3, from the 10 genes to visualize it and the result showed differentially methylated peaks on the mRNA transcript consistent with our m6A-seq results.

CONCLUSION

GO and KEGG of DMGs between E21 and E30 showed most DMGs were muscle-related. In total, 228 DEMs were found, and the majority of DMGs were overlapped with the targets of DEGs. The differentially methylated peaks along with an m6A-miRNA-gene, PDK3, showed the similar results with m6A-seq results. Taken together, the results presented here provide a reference for further investigation of embryonic skeletal muscle development mechanism in goose.

Involvement of miR-337 in high glucose-suppressed osteogenic differentiation in bone marrow mesenchymal stem cells via negative regulation of Rap1A

This study aims to investigate the inhibitory effect of microRNA-337 (miR-337) on osteogenic differentiation in bone marrow mesenchymal stem cells and its action of mechanisms. Overexpression and knockdown of miR-337 were performed in bone marrow mesenchymal stem cells (BMSCs). Cell proliferation was assessed by using a cell counting kit-8 (CCK-8), mineralization assay was performed by alizarin red staining, and alkaline phosphatase activity was then measured. Luciferase reporter assay was applied to verify miR-337 binding to Ras-related protein 1A (Rap1A) mRNA. Reverse transcription and quantitative polymerase chain reaction (RT-qPCR) was applied to measure the expressions of runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), osteocalcin (OCN), osteopontin (OPN), bone morphogenetic protein (BMP2), and miR-337. Then the protein level of Rap1A was determined by western blot analysis. High glucose inhibited osteogenic differentiation but increased the level of miR-337. Overexpression of miR-337 inhibited osteogenic differentiation in high glucose-treated BMSCs, while the knockdown of miR-337 reversed this process. Luciferase reporter assay confirmed that the presumed pairing binding site of miRNA-337 was in the 3'-UTR of the Rap1A WT. In addition, the knockdown of Rap1A distinctly repressed osteogenic differentiation, which blocked the effect of miR-337-knockdown on osteogenic differentiation in high glucose-treated BMSCs. MiR-337 could repress osteogenic differentiation in high glucose-treated BMSCs directly targeting Rap1A, thus provide a potential therapeutic strategy for patients with diabetic osteoporosis in clinic.

The miRNA-15b/USP7/KDM6B axis engages in the initiation of osteoporosis by modulating osteoblast differentiation and autophagy

Osteoporosis is a metabolic disease that results from oxidative stress or inflammation in renal disorders. microRNAs (miRNAs) are recently implicated to participate in osteoporosis, but the mechanism remains largely unexplored. Herein, we aimed to explore the potential role of miR-15b in osteoblast differentiation and autophagy in osteoporosis. We established osteoporosis models through ovariectomy and determined that miR-15b was highly expressed whereas USP7 and KDM6B were poorly expressed in tissue of osteoporosis mice. Treatment of silenced miR-15b resulted in the elevation of decreased bone mineral density (BMD), the maximum elastic stress and the maximum load of osteoporosis mice. In osteoblasts, miR-15 overexpression decreased proliferation but suppressed the cell differentiation and autophagy, accompanied with decreased expression of USP7. Mechanistically, miR-15 bound and inhibited USP7 expression, while overexpression of USP7 promoted autophagy of osteoblasts. USP7, importantly, strengthened the stability of KDM6B and promoted KDM6B expression. MG132 protease inhibitor increased KDM6B and USP7 expression in osteoblasts. Silencing of KDM6B reversed the promoting effect on autophagy and proliferation induced by overexpression of USP7. Taken altogether, miR-15b inhibits osteoblast differentiation and autophagy to aggravate osteoporosis by targeting USP7 to regulate KDM6B expression.

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.

Scaffold-Based Gene Therapeutics for Osteochondral Tissue Engineering

Significant progress in osteochondral tissue engineering has been made for biomaterials designed to deliver growth factors that promote tissue regeneration. However, due to diffusion characteristics of hydrogels, the accurate delivery of signaling molecules remains a challenge. In comparison to the direct delivery of growth factors, gene therapy can overcome these challenges by allowing the simultaneous delivery of growth factors and transcription factors, thereby enhancing the multifactorial processes of tissue formation. Scaffold-based gene therapy provides a promising approach for tissue engineering through transfecting cells to enhance the sustained expression of the protein of interest or through silencing target genes associated with bone and joint disease. Reports of the efficacy of gene therapy to regenerate bone/cartilage tissue regeneration are widespread, but reviews on osteochondral tissue engineering using scaffold-based gene therapy are sparse. Herein, we review the recent advances in gene therapy with a focus on tissue engineering scaffolds for osteochondral regeneration.

Suppression of miR-451a accelerates osteogenic differentiation and inhibits bone loss via Bmp6 signaling during osteoporosis

Bone homeostasis is known as a dynamic balance, including bone formation through osteoblasts and bone resorption by osteoclasts. MicroRNAs (miRs) play a critical role in regulating bone formation and homeostasis. In the study, the effects of miR-451a on bone homeostasis were investigated. The results indicated that the primary osteoblasts and mesenchymal stem cells (MSCs), as the main source of osteoblasts, isolated from miR-451a-knockout (KO) mice showed promoted osteogenesis. in vivo, an ovariectomized (OVX) animal model was used to further explore the effect of miR-451a on osteoporosis. Micro-computed tomography (μCT) indicated a promoted bone volume in miR-451a-KO mice compared to wild-type (WT) mice after OVX operation, demonstrating a redundant bone formation after the knockout of miR-451a. Importantly, we for the first time found that bone morphogenetic protein 6 (Bmp6) was a direct target of miR-451a, elevating bone formation through regulating SMAD1/5/8 expression. In conclusion, reducing miR-451a expression levels could enhance bone formation during the progression of osteoporosis, which might be at least partly via the meditation of Bmp6 expression.

Hypoxia-responsive miRNA-21-5p inhibits Runx2 suppression by targeting SMAD7 in MC3T3-E1 cells

Sustained hypoxia inhibits osteogenesis and osteoblast differentiation by downregulating the expression of runt‐related transcription factor 2 (Runx2). MicroRNAs (miRNAs) have been shown to regulate osteogenesis and osteoblast differentiation. In the present study, we profiled miRNAs, with microRNA array and quantitative real‐time polymerase chain reaction (RT‐PCR) methods, in mouse osteoblast (MC3T3‐E1) cells under hypoxia. Then, we investigated regulation by miRNA‐21‐5p on the expression of Runx2 and other osteoblast differentiation‐associated markers via gain‐of‐function and loss‐of‐function strategies. We found that expression of miRNA‐21‐5p, miRNA‐210‐5p, and other eight miRNAs was upregulated significantly in hypoxia‐treated MC3T3‐E1 cells. miRNA‐21‐5p overexpression downregulated the expression of the mRNA and protein of suppressor of mothers against decapentaplegic (SMAD7) markedly, the 3′‐untranslated region (3′‐UTR) of which was highly homologous with the miRNA‐21‐5p sequence. miRNA‐21‐5p overexpression upregulated the protein expression of Runx2 in hypoxia‐treated MC3T3‐E1 cells, although mRNA expression of Runx2 and other osteoblast differentiation‐associated molecules (eg, osteocalcin, procollagen type 1 amino‐terminal propeptide, P1NP) were not regulated by it; such upregulation was SMAD7‐dependent. In conclusion, hypoxia‐responsive miRNA‐21‐5p promoted Runx2 expression (at least in part) by targeting the 3′‐UTR and downregulating SMAD7 expression. Our study suggests a protective role of miRNA‐21‐5p in promoting osteoblast differentiation under hypoxia.

Mmu-miR-185 depletion promotes osteogenic differentiation and suppresses bone loss in osteoporosis through the Bgn-mediated BMP/Smad pathway

MicroRNAs (miRs) play an essential role in the regulation of bone formation and homeostasis. miR-185 has been reported to negatively regulate osteogenesis in vitro. However, whether it has an impact on in vivo bone homeostasis remains unknown. Here, we demonstrated that primary osteoblasts and mesenchymal stem cells derived from miR-185-knockout (KO) mice exhibited enhanced osteogenesis. Further, we constructed an ovariectomized mouse model to investigate the role of miR-185 during osteoporosis. Micro-computed tomography revealed an increased bone volume in KO compared to wild-type mice 6 weeks after surgery, indicating redundant bone formation after miR-185 depletion. Dual-luciferase reporter assays identified biglycan (Bgn), which promotes bone formation through the BMP/Smad pathway, as the direct target of miR-185. Taken together, these findings indicate that blocking miR-185 expression increases bone formation during osteoporosis, which may partly occur through the regulation of Bgn expression and BMP/Smad signaling.

Current Progress on MicroRNA-Based Gene Delivery in the Treatment of Osteoporosis and Osteoporotic Fracture

Emerging evidence demonstrates that microRNAs, as important endogenous posttranscriptional regulators, are essential for bone remodeling and regeneration. Undoubtedly, microRNA-based gene therapies show great potential to become novel approaches against bone-related diseases, including osteoporosis and associated fractures. The major obstacles for continued advancement of microRNA-based therapies in clinical application include their poor in vivo stability, nonspecific biodistribution, and unwanted side effects. Appropriate chemical modifications and delivery vectors, which improve the biological performance and potency of microRNA-based drugs, hold the key to translating miRNA technologies into clinical practice. Thus, this review summarizes the current attempts and existing deficiencies of chemical modifications and delivery systems applied in microRNA-based therapies for osteoporosis and osteoporotic fractures to inform further explorations.

Parathyroid hormone-stimulation of Runx2 during osteoblast differentiation via the regulation of lnc-SUPT3H-1:16 (RUNX2-AS1:32) and miR-6797-5p

Parathyroid hormone (PTH) acts as a regulator of calcium homeostasis and bone remodeling. Runx2, an essential transcription factor in bone, is required for osteoblast differentiation. Noncoding RNAs such as long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) play crucial roles in regulating gene expression in osteoblasts. In this study, we investigated the effects of PTH on osteoblast differentiation via Runx2, lncRNA, and miRNA expression in human bone marrow stromal cells (hBMSCs) and human osteoblastic cells (MG63). PTH-treatment of hBMSCs for 24 h, 7 days, and 14 days stimulated Runx2 mRNA expression. Using bioinformatics tools, we identified 17 lncRNAs originating from human Runx2 gene. Among these, lnc-SUPT3H-1:16 (RUNX2-AS1:32) expression was highly up-regulated by the 7 d PTH-treatment in hBMSCs. We also identified miR-6797-5p as the putative target of lnc-SUPT3H-1:16 and Runx2 using bioinformatics tools. PTH-treatment increased the expression of miR-6797-5p in hBMSCs, and overexpression of miR-6797-5p decreased osteoblast differentiation in MG63 cells, suggesting a role for lnc-SUPT3H-1:16 as sponge molecule. A luciferase gene reporter assay identified direct targeting of miR-6797-5p with lnc-SUPT3H-1:16 and 3'UTR Runx2 in MG63 cells. Thus, PTH stimulated the expression of lnc-SUPT3H-1:16, miR-6797-5p and Runx2, and due to the sponging mechanism of lnc- SUPT3H-1:16 towards miR-6797-5p, Runx2 was protected, resulting in the promotion of osteoblast differentiation.