我们前期研究发现：miR-196b-5p可抑制骨髓基质干细胞成骨分化而促进其成脂分化，miR-196b-5p靶向抑制Wnt信号激活因子SEMA3A，成骨细胞特异性miR-196b-5p转基因小鼠骨量下降。因此提出假说：miR-196b-5p通过抑制SEMA3A而影响Wnt信号，进而调节骨髓基质干细胞成骨-成脂平衡而影响机体骨稳态。为验证该假说，本项目拟完善miR-196b-5p转基因鼠的表型研究，分析转基因鼠骨形成/骨吸收和骨量的变化及其与SEMA3A-β-catenin信号的关系；通过体内外实验明确SEMA3A-β-catenin信号参与miR-196b-5p调节骨髓基质干细胞定向分化和骨稳态的机制；观察抑制miR-196b-5p是否可以缓解去卵巢小鼠骨丢失表型；探讨miR-196b-5p与人骨质疏松的相关性。本研究将为揭示miRNA在骨质疏松等疾病发展中的作用机制提供理论依据和新靶点。

Our preliminary data have demonstrated that miR-196b-5p inhibited osteogenic differentiation and promoted adipogenic differentiation from bone marrow stromal stem cells. Mechanism investigation demonstrated Semaphorin3A (SEMA3A), a recently identified novel activator of canonical Wnt, to be the direct target of miR-196b-5p. In addition, we developed osteobast-specific miR-196b-5p transgenic mice in which miR-196b-5p was overexpressed under the control of the Col1α1 promoter. The bone mass was dramatically decreased in the transgenic mice as compared to wild-type control. Based on these findings, we hypothesize that miR-196b-5p may inactivate the canonical Wnt/β-catenin signaling through directly inhibiting SEMA3A translation, thereby regulating the osteogenic and adipogenic differentiation of bone marrow stromal stem cells and controlling bone homeostasis and bone mass. In this project we will further analyze the phenotypes of the miR-196b-5p transgenic mice. Then by using in vitro and in vivo experiments, we will further investigate if and how SEMA3A-β-catenin signaling is involved in the regulation of marrow stromal stem cell differentiation and bone homeostasis by miR-196b-5p. Moreover, we will further study whether inhibition of miR-196b-5p helps to improve the phenotypes of bone loss in ovariectomized mice and investigate the correlation between mir-196b-5p and osteoporosis in human. This proposed study will help to enrich our understanding of the role of miRNAs in the osteoblast development and bone homeostasis, and may suggest a new therapeutic target for metabolic disorders such as osteoporosis.