Notch信号通路调控老龄骨髓间充质干细胞迁移及成骨-成脂转分化机制研究

Aged patients have osteoporosis and poor healing ability after jaw bone fracture. In China, the population is getting into an aging population, so the basic scientific problem related to the healing of facial bone fracture in the senile is worthy to studied, not only to solve medical problems, but also to meet the social needs. Bone marrow mesenchymal stem cells (BMSCs) in fracture region played a key role in the repairation. In the aged BMSCs, the osteogenic potential decreases while the adipogenic potential increases, namely, osteogenesis transdifferentiates into adipogenesis which has negative impacts on the bone healing. Among the moleculars regulating BMSCs, Notch signaling pathway is concerned with age-related changes and osteogenesis differentiation of BMSCs. Therefore, Notch is an expected critical regulating factor that affects the osteo-adipo transdifferentiation of BMSCs. This project focuses on the effects of Notch signaling pathway on some age-related changes of rabbit BMSCs including the migration and osteo-adipo transdifferentiation. Then we change the Notch activity to discuss the variation of migration capacity and osteo-adipo transdifferentiation in BMSCs and its regulation mechanism. After that, we will construct a control-released system to regulate Notch activity in vivo, to verify the role that Notch plays in aged osteoporosis fracture healing. This project will study the molecular mechanism that Notch signaling pathway regulating the migration and osteo-adipo transdifferentiation in BMSCs. This study is valuable to improving the healing ability of senile osteoporosis fracture, and has important meanings for the studies of other academic areas such as osteoporosis prevention and control, stem cells and bone regeneration.

老龄患者颌骨骨质疏松，骨折术后愈合能力差，而我国人口日趋老龄化，因此研究老年骨折相关基础科学问题，不仅解决医学难题，也符合社会需求。骨髓间充质干细胞(BMSCs)在骨折修复中扮演了关键角色，老龄BMSCs成骨减弱而成脂增强，即成骨-成脂转分化，直接影响了骨愈合。调控BMSCs的分子途径中，Notch信号通路与BMSCs的增龄改变和成骨分化均有关，因此可能在成骨-成脂转分化调控中发挥了关键作用。本课题研究兔BMSCs增龄改变与Notch信号通路的关系；改变Notch活性来探讨其对老龄BMSCs的迁移和成骨-成脂转分化的调控机制；并构建一种缓释活化系统在动物体内验证Notch通路对老龄骨质疏松性骨折愈合的作用。本课题研究Notch信号通路调控老龄BMSCs转分化机制及迁移能力，对改善老年骨质疏松性骨折愈合具有重要意义，对于其他研究领域如骨质疏松防治、干细胞与骨再生研究也具有参考价值。

老年个体骨髓间充质干细胞的生物学特性发生增龄性改变，其骨再生能力减弱，影响骨创愈合效果。本研究探讨老龄个体骨髓间充质干细胞（BMSCs）成骨潜能增龄改变及Notch信号通路在其中的调控作用，主要研究内容包括：①BMSCs增殖、迁移能力及成骨、成脂分化潜能的增龄性改变，以及老龄BMSCs的成骨-成脂转分化现象与Notch信号通路之间的关系；② Notch信号通路调控老龄BMSCs迁移能力及成骨-成脂分化的机制；③动物体内实验，Notch信号通路在动物模型中与骨密度的老龄变化之间的关系，并通过调节老龄BMSCs中Notch通路活性，再用处理后的细胞复合生物支架材料，来修复颅骨缺损，以期探索改变Notch通路活性是否能够逆转的老龄BMSCs中受损的骨再生能力。研究结果发现，年轻、中年、老龄组BMSCs的增殖能力和迁移能力并未随着年龄增加而明显受损；但在成骨和成脂的化学诱导及其定量分析实验中发现，老龄组BMSCs的成骨分化能力下降明显，与此相反，BMSCs成脂分化潜能，随个体年龄增长出现增强的趋势；关于Notch通路中各个信号分子跟年龄的关系，研究结果显示Notch1、2、3受体以及其下游因子Hey1、Hes1的基因蛋白表达升高，结合前述成骨、成脂研究结果，提示该通路参与了调控骨修复潜能的增龄性改变；应用γ-分泌酶抑制剂DAPT下调老龄BMSCs中Notch通路的活性，其下游信号亦得到改变，老龄组细胞中受损的成骨潜能得到改善，而原本随年龄增加的成脂潜能被逆转，相关成骨和成脂分化的信号蛋白也支持这一结论；老龄组的胫骨和颅骨的骨小梁质量存在不同程度的退化，对老龄BMSCs进行Notch活性的干预，复合生物支架材料修复颅骨缺损，发现经抑制Notch活性的细胞，骨修复能力有所增强。综上，本研究为进一步阐明增龄相关成骨能力改变的调控机制及改善老龄个体干细胞骨再生能力提供了实验室依据；为老龄化疾病治疗过程中存在的难题，如老龄患者骨损伤愈合困难等提供了新的线索。