抗衰老因子GDF11维持骨髓间充质干细胞功能及逆转老年性骨丢失的机制研究

GDF11 is the newly discovered circulating factor that can reverse the aging related diseases, but its effect on bone metabolism is unknown. Our pilot work found that GDF11 could maintain the function of bone marrow mesenchymal stem cells (BMSCs) by enhancement of self-renewal and cloning formation ability. This study aims to investigate the effect of GDF11 on bone metabolism through studying BMSCs function. First we will elevate the levels of GDF11 in aging mice circulation by using heterochronic parabiosis model and intervention with recombinant mouse GDF11 protein, and investigate the effect of GDF11 on aging mice BMSCs ,including amount of BMSCs ,self-renewal, colony formation ability, osteogenenic differentiation potential and the process of aging and apoptosis. And then we will construct the BMSCs specific GDF11 receptor (Activin receptor II) gene knockout mice to study the effect of blocking GDF11 on BMSCs and bone mass; The changes of GDF11 on regulating BMSCs was also studied by blocking Notch signal pathway. We hope that illustrating the new mechanism of reversing age-related bone loss by maintaining BMSCs function with anti-aging factor GDF11 will be useful to explore a new way of prevention and treatment for senile osteoporosis.

GDF11为新发现的可逆转衰老相关性疾病的循环因子，但其对骨代谢的影响未明。我们首次发现GDF11可以增强骨髓间充质干细胞（BMSCs）的自我更新及克隆形成能力而维持BMSCs的功能，本研究拟从BMSCs功能角度探讨GDF11对骨代谢的作用。首先用青年-老年联体小鼠模型、重组GDF11蛋白干预，升高老年小鼠循环中GDF11水平，观察GDF11对老年小鼠BMSCs的数目，自我更新、克隆形成能力、成骨分化潜能等功能和骨代谢情况的影响；进而构建BMSCs特异性GDF11受体（Activin receptor II）基因敲除小鼠模型，研究GDF11作用阻断对BMSCs及骨量的作用；同时研究阻断Notch信号途径对GDF11作用的影响，解析GDF11对BMSCs影响的信号通路。探讨是否存在抗衰老因子GDF11通过维持BMSCs功能，逆转老年性骨丢失的新机制，为老年性骨质疏松的防治拓展新途径。

GDF11为新发现的可逆转衰老相关性疾病的循环因子，但其对骨代谢的影响未明。我们前期研究发现GDF11可以增强骨髓间充质干细胞（BMSCs）的自我更新及克隆形成能力而维持BMSCs的功能，本研究通过临床数据分析以及体内和体外实验探讨了GDF11对骨代谢的作用。首先我们收集了169例47-78岁绝经后女性，统计病人的基本信息，测定其骨密度，并收集其血液样本，ELISA测定GDF11水平，血液生化指标和骨生化指标，结果发现血GDF11水平随年龄增长而升高，与BAP呈负相关，与NTX无关，并且血GDF11水平是BMD的独立负性预测因子。而探究中国老年女性的骨质疏松症患病率与血清GDF11浓度的关系，我们发现GDF11的浓度与老年妇女的骨质疏松风险密切相关。接着我们通过细胞和动物实验进一步探讨了GDF11的作用及机制，我们观察到细胞实验中，GDF11重组蛋白抑制骨髓间充质干细胞的成骨性分化，而对小鼠进行腹膜腔内注射GDF11重组蛋白，可以抑制骨形成从而加速小鼠年龄相关性骨丢失。这一作用是通过在成骨分化过程诱导SMAD2/3磷酸化从而抑制RUNX2表达产生的。在体内和体外实验中，GDF11对破骨细胞分化或骨吸收均无影响。我们的结果确定了GDF11是绝经后妇女BMD的独立负性预测因子，与年龄密切相关，并且通过抑制成骨分化，导致老年性骨丢失，因此其拮抗药物可为老年性骨质疏松的防治提供新思路。