miR-21/sprouty1功能轴参与骨质疏松发病的机制研究

Attenuated bone formation is the key mechanism in the pathology of postmenopausal osteoporosis. Recent studies show that miRNAs play an important role in bone formation and bone remodeling. However, it is still unclear that the pathophysiclogical role for miRNA in human osteoporosis. In previous study we found decreased miR-21 levels correlated with a lower degree of bone formation in patients with postmenopausal osteoporosis and ovariotomized(OVX) mice. Moreover, we found miR-21 directly targeted sprouty1(spry1) to regulate osteogenic differentiation in vitro. Therefore, we hypothesized that the abnormal function of miR-21/spry1 axis may be invovled in osteoporosis. In this study , we intend to identify the real role of miR-21/spry1 functional axis in miR-21osb-/- conditional knockout mice which specially knockout miR-21 in osteoblasts. Moreover, we further study the therapeutic role of miR-21/spry1 functional axis in postmenopausal osteoporosis by using OVX mice model in vivo.After injecting miR-21 mimics and inhibitors into OVX mice, we assess new bone formation and bone mass through micro-CT, dynamic bone histomorphometric analysis and bone histological and histomorphometric analysis. This study will firstly reveal miRNAs regulation involved in osteoporosis, and would help us to understand the mechanism of osteogenic differentiation and develop promising stragegies to treat osteoporosis.

成骨功能低下是骨质疏松发病的重要原因。研究证明miRNA在骨形成和重建过程中起关键调控作用，但miRNA参与骨质疏松发病的机制目前尚不清楚。本课题组前期利用基因芯片技术发现在骨质疏松患者及模型动物骨组织及细胞中miR-21表达明显下调，并在体外研究中发现miR-21通过靶基因sprouty1调控成骨分化。因此，我们推测miR-21/sprouty1功能轴异常可能参与骨质疏松发病。本研究通过在成骨细胞中敲除miR-21，构建miR-21osb-/-条件敲除小鼠，并借助去势模型模拟绝经后骨质疏松，利用micro-CT、动态骨形成率及组织学等方法检测新骨形成，从细胞到活体动物水平进一步探讨miR-21/sprouty1功能轴对骨形成的调控作用及参与骨质疏松发病的分子机制。本课题将首次从体内角度揭示miRNA分子调控网络参与骨形成的分子机理，并为防治骨质疏松及骨缺损等疾病提供新的治疗靶点及策略。

本项目利用绝经后骨质疏松及慢性牙周炎两种经典的慢性炎症微环境，研究在炎症微环境下，干细胞分化能力的改变及miR-21-Spry1功能轴对干细胞分化能力的影响；以及对成骨破骨相偶联机制的影响，并且研究初步了研究雌激素在绝经后骨质疏松中对干细胞分化，成骨破骨功能的影响；结果显示在慢性炎症环境中，干细胞成骨、成脂分化能力下降；炎性因子TNF-α能够通过miR-21-Sprouty1功能轴抑制干细胞体外分化，并且在体内通过负向调控MiR-Sprouty1功能轴来影响骨形成；体内注射TNF-α中和抗体及miR-21长效前体能够部分重塑OVX受损的骨形成能力；通过进一步研究MiR-21在破骨中的作用，我们发现miR-21能够抑制破骨分化，并且通过调控RANKL，OPG表达参与成骨破骨偶联调控。同时发现骨质疏松来源干细胞FASL表达异常可能跟雌激素表达有关。综上所述，本研究紧密围绕不同慢性炎症环境对骨改建的影响，并且进一步研究了炎性因子对成骨系和破骨系细胞在其中的系统作用，并在体内研究了miR-21在骨质疏松过程中对骨改建的影响,初步研究了骨质疏松中雌激素通过调控FASL对成骨系和破骨系细胞的作用。本项目的完成将很有可能为研究慢性炎症所致的骨疾病提供新的实验依据和靶点；为治疗骨质疏松及牙周炎提供新的思路和方法。