MACF1/TCF4/miR-335信号轴在老年性骨质疏松症中的作用机制研究

The decreased osteogenetic capacity of mesenchymal stem cells (MSCs) results in the reduction of bone formation, which is one of the important factor causing the occurrence of senile osteoporosis. Inhibition of Wnt signaling in MSCs is closely related with senile osteoporosis. MACF1 is an important protein, which can translocate β-catenin to the nucleus in Wnt signal pathway. However, the mechanism of MACF1 in senile osteoporosis is unclear. Our recent advances showed that miR-335, which could promote osteogenesis of MSCs, was a potential downstream target of TCF4. Besides, the MACF1 and miR-335 expression in bone tissues and MSCs of senile osteoporosis were downregulated. Knockdown of MACF1 in preosteoblast cells decreased miR-335 expression level. Therefore, we proposed that MACF1 may play an important role in senile osteoporosis via regulating miR-335 expression through TCF4. .This project will investigate the following content: (1) The function of MACF1 in MSCs osteogenic differentiation in senile osteoporosis; (2) The regulatory effect of MACF1 on miR-335 expression through TCF4 during MSCs osteogenic differentiation; (3) The regulatory function of MACF1 on MSCs osteogenic differentiation through miR-335. This project is aimed to provide theoretical basis and potential target for the prevention and treatment of senile osteoporosis.

间充质干细胞（MSCs）成骨分化能力下降导致骨形成减少是老年性骨质疏松症发生的重要原因之一。MSCs的Wnt信号抑制与老年性骨质疏松密切相关。MACF1是Wnt信号通路的重要蛋白，可促进β-catenin入核。但MACF1在老年性骨质疏松中的作用机制尚不清楚。申请者发现促进MSCs成骨分化的miR-335是TCF4潜在转录物，老年性骨质疏松症的骨组织和MSCs中MACF1和miR-335下调；前成骨细胞分化中敲低MACF1抑制miR-335表达。因此提出：MACF1可能通过TCF4调控miR-335表达在老年性骨质疏松中起重要作用。.本项目拟研究：（1）MACF1对老年性骨质疏松中MSCs成骨分化的影响；（2）MSCs成骨分化过程中MACF1通过TCF4对miR-335表达的调控；（3）MACF1通过miR-335对MSCs成骨分化的作用。以期为防治老年性骨质疏松症提供理论基础和潜在靶点。

MSCs成骨分化能力下降是引发骨质疏松的主要原因之一。骨质疏松等骨骼系统疾病发生过程中，MSCs成骨分化和骨形成的分子机制研究已得到了越来越多的关注，但目前其分子机制尚未阐明。MACF1在Wnt/β-catenin信号转导和细胞成骨分化中起重要作用。但是MACF1对MSCs成骨分化的作用和调控机制尚不清楚。miRNA参与调节骨形成并在骨代谢疾病发生过程中起重要作用。其中miR-335通过Wnt信号在MSCs成骨分化调控中起重要作用。但MSCs成骨分化过程中miR-335表达如何被调控尚未阐明。.本项目采用间充质干细胞条件敲入MACF1小鼠模型、前成骨细胞条件敲除MACF1小鼠模型和老龄小鼠模型，基于动物、细胞和分子三个层次探究：间充质干细胞和前成骨细胞中MACF1成骨分化和骨形成的作用和机制。研究获得了如下主要结论：.（1）在骨质疏松症临床患者和老龄小鼠骨组织和MSCs细胞中MACF1和miR-335表达与年龄负相关。（2）在老年性骨质疏松小鼠中，间充质干细胞中MACF1高表达可以促进成骨分化和骨形成，并且调控miR-335表达。（3）前成骨细胞中MACF1低表达可以抑制骨形成，并且通过BMP2/Smad通路抑制前成骨细胞成骨分化。（4）在成骨分化过程中，MACF1可通过TCF4调控miR-335表达。.本研究围绕“MSCs成骨分化能力下降导致骨形成减少是老年性骨质疏松症发生的重要原因之一”这一个有特色的细胞生物学和健康医学研究领域的基础科学问题，阐明了在老年性骨质疏松中MACF1调控成骨分化并参与骨形成的作用和机制。发现在老年性骨质疏松发生过程中，通过在MSCs细胞和前成骨细胞中高表达MACF1，可以增强细胞成骨分化和骨形成的能力。因此MACF1可以作为抗骨质疏松药物的靶点，通过基因特异靶向药物实现特异、有效地防治骨质疏松症的理论依据。