lncRNA MALAT1通过miR-155/Smad5调控BMSCs成骨分化在镉所致骨质疏松中的作用机制研究

Cadmium pollution seriously endangers human health; however，the mechanisms of cadmium-induced osteoporosis remain unclear. Inhibition on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is the main pathogenesis of osteoporosis, while there are few publications about the effects of cadmium on osteogenic differentiation. We previously found that cadmium-induced inflammation decreases lncRNA MALAT1 levels, increases miR-155 levels, and inhibits osteogenic differentiation of BMSCs. Based on the data of ceRNA chip for cadmium treatment of BMSCs, we are going to investigate: (1) the effect of different levels of cadmium on osteogenic differentiation in BMSCs, and its dependence on anti-inflammatory factor, up-regulated lncRNA MALAT1 level and down-regulated miR-155 level, and the Emodin antagonism on cadmium-induced osteogenic differentiation, respectively; (2) the effect of cadmium on bone damage in wild and miR-155-/- animal models and intervention of Emodin ; (3) the changes of related indicators in populations exposed to cadmium during follow-up. The purpose of this study is to investigate the roles and mechanisms of lncRNA MALAT1-regulated osteogenic differentiation of BMSCs via miR-155/Smad5 in cadmium-induced osteogenic differentiation and osteoporosis in cellular, animal, and human levels. The results of this investigation will not only facilitate a better understanding of the molecular mechanisms of cadmium-induced osteoporosis, but also provide new clues for identifying early biomarkers and developing novel measures of precise prevention and treatment for cadmium-induced health hazards.

镉污染严重危害人类健康，其引起骨质疏松的机制尚不清楚。骨髓间充质干细胞(BMSCs) 成骨分化抑制是骨质疏松的主要发病机制，镉对成骨分化影响的研究甚少。我们前期发现镉引起炎症、lncRNA MALAT1水平降低和miR-155水平升高，并抑制BMSCs成骨分化。本项目结合镉处理BMSCs的ceRNA芯片结果，拟探讨不同水平镉对BMSCs成骨分化的影响，并观察抗炎因子、上调lncRNA MALAT1、下调miR-155及大黄素对镉抑制BMSCs成骨分化的拮抗作用；在野生型和miR-155-/-动物中观察镉骨损害作用及大黄素的干预效果；在镉暴露人群中随访观察相关指标变化。在细胞、动物及人群层次探讨lncRNA MALAT1通过miR-155/Smad5调控BMSCs成骨分化在镉所致骨质疏松中作用机制，以揭示镉所致骨损害的分子机制，为寻找镉所致健康危害的早期生物标志和发现新的防治措施提供新线索。

镉污染严重危害人类健康，其引起骨质疏松的机制尚不清楚，且目前对镉所致骨质疏松暂无有效的预防和治疗措施。本项目从细胞、动物和人群三个层面，系统揭示了骨髓间充质干细胞（BMSCs）成骨分化在镉引起骨质疏松中的作用及机制，并在此基础上首次探讨了夏枯草对镉所致骨质疏松的保护效应。结果显示，50及100 mg/L氯化镉经饮水法染毒16周可抑制雌性SD大鼠成骨分化，进而导致骨质疏松。同时，氯化镉还可抑制大鼠股骨原代BMSCs成骨分化, 下调胞内lncRNA MALAT1和BMP/Smad信号通路，并促进miR-155表达；进一步利用原代人源BMSCs（hBMSCs）开展机制研究，发现氯化镉可通过上调miR-155抑制Smad5/Runx2信号通路来影响hBMSCs成骨分化，但对lncRNA MALAT1无明显调控作用；此外，我们发现BMP4/Smad是氯化镉抑制hBMSCs成骨分化的另一信号通路；人群流行病学研究显示miR-155和lncRNA MALAT1虽不适宜作为镉相关骨质疏松的生物标志物，但经基因芯片筛选和人群验证后发现，外周血单个核细胞中GAS5、ENST00000630276和ENST00000661348等lncRNAs具有成为镉相关骨质疏松生物标志物的潜能；最后，采用125及250 mg/kg bw夏枯草水提物灌胃雌性SD大鼠16周，发现夏枯草可有效减轻氯化镉所致成骨分化障碍及骨质疏松，该作用可能与上调BMP4/Smad信号通路有关。综上，本项目研究发现镉可通过miR-155/Smad5/Runx2和BMP4/Smad信号通路抑制BMSCs成骨分化引起骨质疏松，夏枯草对镉所致骨质疏松具有良好的保护作用。项目研究结果为进一步阐明镉所致骨质疏松的具体机制提供了重要科学证据，为寻找镉相关骨损伤的防治措施提供了新线索，有良好理论价值和现实指导意义。