类泛素化蛋白RCAD通过调控自噬影响骨质疏松的作用与机制研究

Diagnose and improving treatment efficiency of osteosarcoma have had drawn remarkable attentions.. Studies report autophagy has effect on the viability and differentiation of MSC, meanwhile, plays an important role in differentiation into osteoblast. RCAD was identified as E3 ligase of Ufm1 ubiquitin-like system by Dr. Honglin Li. We found RCAD deficiency significantly leads to accumulation of mitochondria, ROS and autophagosome in HSCs form RCAD knockout and inducible conditional knockout mice, which further inhibit cell proliferation and cell cycle of mice hematopoieic stem cells(HSCs). Interestingly, our previous data shows osteoporosis happens on heterozygous of RCAD knockout mice much earlier than WT mice. Pilot study found RCAD difficiency results in accumulation of mitochondria and autophagosome in MSC. According to our previous study, we propose the hypothesis that RCAD deficiency impairs malignant biological functions of MSC via autophagy pathway. Secondly, we will study the mechanism how RCAD modifies autophagy and find out the direct target of RCAD. What’s more, this hypothesis will be confirmed in mouse model of senescence osteoporosis. This project will not only be a breakthrough in the field of Ufm1 ubiquitin-like system by demonstrating biological function of RCAD, will do great contribution to mechanistic study of autophagy regulation as well. This study will provide a new version in the mechanism of osteoporosis, which might leads better treatment of this disease.

原发性骨质疏松症的发病机制尚未明了，疗效欠满意。研究报道自噬与骨质疏松和MSC的活力与分化密切相关。申请人实验室独立识别了Ufm1类泛素化E3连接蛋白RCAD，其生理功能尚不明确。研究RCAD敲基因和条件敲基因小鼠，发现RCAD缺失在血液系统抑制自噬降解，造成细胞内线粒体、活性氧和自噬体堆积，抑制小鼠骨髓造血干细胞增殖和分化。预实验发现RCAD杂合子敲基因小鼠较早发生骨质疏松，RCAD缺失致MSC增殖减慢，线粒体和自噬体堆积。基于上述基础提出假说，RCAD通过自噬影响骨质疏松的发生。拟使用原代MSC增殖和分化的模型研究RCAD的功能及分子机制，并在老年骨质疏松的动物模型中验证这一假说。本课题将对ufmylation类泛素化领域极大促进作用，且对自噬调控机制是一项重要的补充。更重要的是，为阐述原发性骨质疏松的发病机制提供新的思路，为临床诊疗带来新的预防和治疗方案。

随着我国人口老龄化现象加剧，老年性骨质疏松症的发病率越来越高，然而骨质疏松的发病机制仍未研究清楚。本课题研究通过建立老年小鼠骨质疏松模型，发现老年骨质疏松小鼠中RCAD表达量显著降低，使用氯喹抑制自噬导致小鼠原代间充质干细胞成骨分化能力和骨矿化能力减弱，RCAD蛋白表达量降低抑制小鼠原代间充质干细胞的成骨分化能力，并且显著影响自噬水平，上述结果提示RCAD蛋白通过调控自噬水平影响间充质干细胞的成骨分化能力，进而导致骨质疏松。此结论对原发性骨质疏松的发病机制提供了重要理论依据，RCAD蛋白的表达水平有可能成为骨质疏松潜在的治疗靶点，为临床诊疗带来新的预防和治疗方案。