miR-17-92家族调控自噬恢复衰老干细胞生物学特性的机制研究

Osteoporosis is a common disease of bones that relates to the senescence. Among the pathogenesis of osteoporosis, the amount and biological characteristic of mesenchymal stem cells (MSCs) are decreased during the senescence is the most important reason. Autophagy is a catabolic process involving the degradation of a cell's own components through the lysosomal machinery. It plays an important role in maintain internal environment stably. Autophagic activity declined during the senescence, however, the relationship between autophagy and biological characteristic of MSCs as well as osteoporosis is not yet fully understood. Our team found that the miR-17-92 cluster regulated osteoblastic differentiation and senescence of MSCs. Furthermore, some researches reported that microRNAs interfered with translation of specific target mRNAs could regulate autophagy from post-transcriptional level. In this study, in vitro and in vivo experiments were used to research the relationship between autophagy and biological characteristic of MSCs; regulatory mechansim between miR-17-92 cluster and autophagy; and the treatment effect of using miR-17-92 cluster in animal model. According to the results, we want to elucidate the regulatory loop among miRNAs, autophagy and biology characteristic of stem cells clearly. Our research not only provides a new treatment for osteoporosis via microRNA application, but also offers a good method for curing other senescence related diseases, such as Alzheimer's disease. Moreover, the autophagy related content are broadened through our study either. Therefore, our research has important theoretical and clinical significance.

骨质疏松是一种衰老相关性疾病，间充质干细胞（MSCs）生物学特性的改变是导致骨质疏松的重要原因。自噬的主要功能是清除细胞内多余的蛋白质或者衰老损伤的细胞器。衰老过程中细胞自噬活动下降，然而自噬是否通过影响MSCs的生物学特性从而引发骨质疏松尚不明确。本课题组前期研究发现miR-17-92家族与MSCs骨向分化及衰老密切相关，且microRNAs能够从转录后水平调控细胞的自噬。因此，本课题拟通过体内、外两部分实验,从自噬与MSCs生物学特性的关系、miR-17-92家族调控自噬的机制、及miR-17-92家族对衰老所致骨质疏松动物模型的治疗三个方面探讨microRNAs、自噬及干细胞生物学特性之间的关系。本研究不但为microRNAs治疗衰老所致骨质疏松提供一定的理论依据，而且能为microRNAs治疗其他衰老相关性疾病提供一定的参考，同时丰富了自噬的相关研究，具有重要的理论与临床意义。

本课题组围绕主要研究内容及预期目标，开展了以下几方面的研究工作：① 多种骨质疏松模型中（卵巢摘除小鼠、睾丸摘除小鼠、SAMP衰老小鼠、糖皮质激素诱导小鼠模型、I型糖尿病小鼠模型），BMMSCs的增殖及成骨分化能力下降，而成脂分化能力明显增强，说明BMMSCs的功能异常，是导致骨质疏松的重要原因；② 衰老小鼠骨质疏松症状明显，衰老小鼠骨组织及BMMSCs中，自噬水平均明显下降；在BMMSCs成骨分化过程中，其自噬水平升高，而在成脂分化过程中，自噬明显受到抑制；③ 过表达自噬相关基因Beclin1后，能够恢复衰老BMMSCs的自噬水平，从而促进其成骨分化而抑制其成脂分化能力；说明自噬对于维持BMMSCs的成骨/成脂分化平衡至关重要；④ 体内系统注射雷帕霉素能够明显恢复衰老小鼠的骨量，抑制其骨髓中的脂滴形成； ⑤ 而注射3-MA能够使年轻小鼠表现出骨质疏松症状；⑥ 去势小鼠BMMSCs中自噬下降，雷帕霉素注射后能够明显恢复去势小鼠的骨量，抑制其骨髓腔中的脂滴；⑦ 证明p53/miR-17/Smurf1级联反应在衰老BMMSCs成骨分化过程中发挥重要的调控作用；并证明自噬主要通过降解p53蛋白发挥调控BMMSCs再生能力的作用；⑧ 证明Aspirin能够恢复衰老和去势小鼠BMMSCs的自噬水平，从而达到治疗和预防骨质疏松的目的；⑨ 发表中文4篇，以第一作者和通讯作者发表SCI 论文6篇，总计影响因子30.8，其中IF>5.0 SCI 4篇；培养硕士研究生2名，博士研究生1名；参加国际特邀学术报告2次，国内特邀学术报告4次。