脂肪细胞来源外泌体在股骨头坏死中的作用及机制研究

The imbalance between osteogenic and adipogenic differentiation of bone marrow stromal stem cells (BMSCs) is an important cause of steroid-induced osteonecrosis of the femoral head (ON), but the mechanism of this imbalance is not yet clear. It has been reported that including adipocytes, most cells secrete exosomes containing multiple components, which modulate the physiological functions of peripheral and distant cells. Our previous results showed that the osteogenic differentiation ability of BMSCs reduced after co-cultured with the exosomes of adipocytes, therefore we hypothesized that the microenvironment around BMSCs of ON patients may be manipulated by adipocytes exosomes, which leads to the decrease of bone formation and proliferation. This project firstly intends to identify themiRNAs in adipocyte-secreted exosomes, which inhibit the osteogenic adipogenic differentiation and promote adipogenic differentiation; Secondly, the biological functions of the adipocyte-secreted exosomes and miRNA will be testified in vitro and in vivo; Lastly, the mechanisms of the miRNAs will be clarified through gene chips, bioinformatics analysis and gain or loss of function experiments. Through this project we hope to enunciate the biological function and molecular mechanism of adipocyte-secreted exosomes in the pathogenesis of osteonecrosis of the femoral head, lay the theoretical foudation for finding new target for ON therapy.

骨髓基质干细胞（BMSCs）成骨与成脂分化失衡是非创伤性股骨头坏死（ONFH）发病的重要机制之一，但其发生失衡的机制仍不明确。现有研究证明包括脂肪细胞在内的绝大多数细胞会分泌包含多种成分的外泌体（exosomes）调节周围及远处细胞的生理功能。我们前期实验发现使用脂肪细胞来源的外泌体处理BMSCs后可以观察到其成骨分化能力下降，据此我们提出激素性股骨头坏死BMSCs分化微环境可能受到脂肪细胞外泌体的影响，导致其成骨及增殖能力下降，本课题组拟分析脂肪细胞来源外泌体中促成脂抑成骨的miRNAs成分， 分别在细胞及动物水平研究外泌体及其内含miRNAs的功能，最后通过基因芯片、生物信息学分析及gain or loss of function等实验明确这些miRNAs的作用机制，系统的阐明脂肪细胞来源外泌体在ONFH发病过程中的作用，为激素性股骨头坏死治疗寻找新的有效靶点奠定理论基础。

股骨头坏死是一种股骨头缺血、坏死导致的股骨头塌陷的疾病。外泌体是一种细胞分泌物，具有传递信号的能力。本项目旨在探讨脂肪细胞来源的外泌体中关键的miRNA对股骨头坏死的影响。结果显示，脂肪细胞来源的外泌体抑制成骨诱导的骨髓基质干细胞（BMSCs）的成骨分化，促进成脂分化。其次，通过敲降外泌体中关键的分子miR-148a发现，BMSCs中成骨标志物RUNX2等的表达上调，成骨过程中的矿化量也显著增加，同时促进碱性磷酸酶（ALP）的活性。然而，成脂标志物PPARγ等的表达降低，且油红O染色中的脂滴也显著降低。以上结果表明，脂肪细胞来源的外泌体miR-148a可能是股骨头坏死治疗中的新靶点，同时为股骨头坏死的治疗提供了理论依据。此外，使用脂肪细胞来源的外泌体处理MPS诱导的股骨头坏死大鼠模型，结果显示，外泌体处理组中股骨头坏比MPS组更严重。表明外泌体可能是股骨头坏死的治疗的一个新策略。