GDF11逆转老龄骨髓干细胞衰老并促进种植体骨结合和骨缺损修复的研究

The world is facing the problems of aging population. The pluripotency of stem cells and new bone formation in response to titanium implants are reduced with age. Most recently studies showed that growth differentiation factor 11 (GDF11) was able to rejuvenate an old mouse's muscles and brain. This discovery suggested GDF11 as a potential factor to fight the ravages of aging in people, and was also selected as one of the top 10 breakthroughs of 2014 by Science. However, its effect on skeletal and dental implant related diseases is largely unknown. Our preliminary data, for the first time, showed that GDF11 administration improved the stemness of bone marrow stem cells (BMSCs) in aged mice, and increased their trabecular bone volumes. In this project, we propose that GDF11 activates the Tgf-β signaling, and then up-regulates the expression of Nanog, which has been recognized as the gateway of stem cell’s pluripotency. To dissect this mechanism, we are going to culture the aged BMSCs in vitro, and perform western blot, ChIP assay and Luciferase assay, as well as knockout of Nanog using CRISPR/Cas9. Next, we are sought to evaluate the effect of GDF11 on the fixation of titanium implant, and on regeneration of critical calvarial defect and femoral cortical bone defect using the elderly rodents. Finally, we are going to analyze the relationship between the GDF11 levels and osseointegration of dental implants in elderly patients, which will contribute to reveal if GDF11 could be a biomarker to predict the prognosis of implant treatment in elderly patients, and to explore potential treatment methods for enhancing the outcome. The results of this project will significantly improve the oral health and life quality of elderly patients.

老龄化是全球面临的重大问题。老龄患者干细胞活性下降，种植术后愈合缓慢。最新发现生长分化因子11（GDF11）能逆转衰老，被Science杂志评为2014年十大突破。但其在老龄化种植体和骨相关疾病中的作用尚未见报道。课题组前期发现GDF11能逆转老龄骨髓干细胞（BMSCs）的干性，改善老龄小鼠的骨质疏松。在此基础上，本研究将通过老龄BMSCs培养和CRISPR/Cas9基因敲除等实验，明确GDF11通过激活TGF-β通路，促进调控干细胞干性的“总开关” Nanog的表达，从而揭示GDF11逆转老龄BMSCs衰老的分子机理；进一步通过动物实验，研究GDF11对老龄小鼠钛种植体骨结合的影响，以及对老龄大鼠颅骨临界性骨缺损和股骨皮质骨缺损修复的影响；最后分析临床老龄患者血液GDF11浓度与种植体骨结合的相关性。研究结果对明确逆转衰老的分子机理，增强老龄患者牙种植修复效果，提高生活质量具有重要意义。

老龄化是全球面临的重大问题。老龄患者干细胞活性下降，种植术后愈合缓慢。本课题以GDF11作为切入点，按照原定计划实施，课题进展顺利，研究发现：（1）体内给予rGDF11负面地影响了年轻和老龄小鼠的骨改建过程，破骨生成增强的同时成骨活动减弱；（2）体外给予rGDF11通过激活TGF-β信号通路中Smad2/3和c-Fos的磷酸化上调Nfatc1促进RANKL介导的BMMs的破骨分化和成熟；（3）体外给予rGDF11通过激活TGF-β信号通路中Smad2/3的磷酸化抑制Runx2的表达从而抑制BMSCs和颅骨成骨细胞的成骨分化；（4）体内给予rGDF11阻碍颅骨和股骨的骨缺损修复及钛种植体骨结合；（5）体内给予GDF11中和抗体治疗可以预防雌激素缺乏引起的骨丧失，并能有效缓解年龄相关的骨质疏松；（6）GDF11通过抑制软骨细胞分化影响骨折愈合；（7）GDF11通过激活TGF-β/Smad信号通路抑制成脂分化。综合以上一系列的体内和体外实验结果，本课题新发现了一种骨改建的调控因子GDF11，并且可能作为绝经后及老龄性骨质疏松症治疗的潜在靶点。. 课题共标注发表SCI论文11篇，其中10分以上4篇，包括Nat Commun和Embo J等。参与课题研究生获得美国骨与矿物质研究协会优秀青年学者等奖项，共培养4名博士生毕业（均进入博士后工作站），2名硕士毕业；在此基础上，课题负责人获得国家自然科学基金优秀青年基金和面上项目资助，入选青年长江学者，万人计划领军人才，并担任四川省科技创新团队负责人。

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