Elucidation of the molecular mechanisms governing the osteogenic differentiation of human mesenchymal stem cells (hMSCs) is of great importance for improving the treatment of bone-related diseases. MicroRNAs (miRNAs or miRs), a class of small non-coding RNAs, are critical in a number of biological processes, including the proliferation, differentiation and survival of cells and organisms. Emerging evidence indicates that miRNAs are essential in regulating osteoblastogenesis and bone formation. However, the role of miRNAs in osteoblast mechanotransduction remains to be defined. The present study aimed to examine the role of miR-153 in the osteogenesis of hMSCs and to investigate the impact of miR-153 on bone morphogenetic protein receptor type II (BMPR2) expression. The overexpression of miR-153 inhibited the osteogenic differentiation of hMSCs, whereas downregulation of miR-153 enhanced the process. Furthermore, bioinformatic analysis predicted that miR-153 is a potential regulator of BMPR2. The direct binding of miR-153 to the BMPR2 3'-untranslated region (3'-UTR) was demonstrated by a luciferase reporter assay using a construct containing the BMPR2 3'-UTR. In addition, knockdown of BMPR2 by RNA interference inhibited the osteogenic differentiation of hMSCs, with a similar effect to the upregulation of miR-153. In conclusion, the results suggest that miR-153 is a mechano-sensitive miRNA that regulates osteoblast differentiation by directly targeting BMPR2, and that therapeutic inhibition of miR-153 may be an efficient anabolic strategy for skeletal disorders caused by pathological mechanical loading.

Astragaloside IV (AST-IV) facilitates the proliferation and migration of osteoblastlike cells. We sought to explore the effect and potential mechanism of AST-IV on regeneration of tibial defects. To reveal the effect of AST-IV on regeneration of tibial defects in rat, HE staining and microcomputed tomography (μCT) were performed on tibial bone. The binding relationship between miR-124-3p.1 and STAT3 was analyzed by TargetScan V7.2 and a dual-luciferase reporter assay. Human bone marrow mesenchymal stromal/stem cells (hBMSCs) were identified by morphological observation and flow-cytometric analysis. To reveal the effect and mechanism of AST-IV on phenotypes of hBMSCs, hBMSCs were treated with AST-IV, miR-124-3p.1 mimic, and pcDNA-STAT3, and cell viability, cell cycle, ALP activity, and calcium deposition of hBMSCs in vitro were determined by MTT, flow-cytometric analysis, ELISA, and Alizarin red staining, respectively. The expressions of osteoblast marker molecules (RUNX2, OCN, Smad4), miR-124-3p.1, and STAT3 were indicated by RT-qPCR and Western blot. AST-IV decreased miR-124-3p.1 expression, increased STAT3 expression in tibial bone defects, and promoted regeneration of tibial bone defects in a concentration-dependent manner. The hBMSCs appeared spindle-shaped and were positive for CD105, but negative for CD34. MiR-124-3p.1 negatively regulated STAT3 expression in hBMSCs under osteogenic conditions. AST-IV promoted viability, cell cycle, ALP activity, and osteogenic differentiation of hBMSCs along with increased expressions of osteoblast marker molecules, which was partially reversed by miR-124-3p.1 overexpression. However, the effect of miR-124-3p.1 overexpression on hBMSCs was also partially reversed by STAT3 overexpression. AST-IV improves tibial defects in rats and promotes proliferation and osteogenic differentiation of hBMSCs through the miR-124-3p.1/STAT3 axis.

Aim: Given that astragaloside-IV (As-IV) has the ability to promote osteogenic differentiation, its mechanism is worthy of exploration. Methods: The effect of As-IV on rat tibial defects was examined by histopathological staining and MiR-CT scan. The alkaline phosphatase (ALP) content, osteogenic differentiation-related gene expressions, and mineralized nodule formation in bone marrow mesenchymal stem cells (BMSCs) were detected. Results: As-IV repaired tibial defects of rats. As-IV or neuromedin receptor 2 ( NMUR2) overexpression elevated ALP content, mineralized nodules, osteogenic differentiation-related genes, β-catenin and NMUR2 levels, the effects of which were reversed by NMUR2 silencing or Wnt/β-catenin pathway inhibitors. Conclusion: As-IV regulates the Wnt/β-catenin pathway through NMUR2 to promote the repair of tibial defects in rats and the differentiation of BMSCs into osteoblasts.