转录因子Satb2/Hoxa2/Runx2的交互作用在失重性骨质疏松的调控及机制研究

Because the significant osteoporosis induced by weightlessness has no self-limitation and lack of effective countermeasures, it has become one of the most medical problems during long-term spaceflight. It has been reported that the decrease in osteoblast (OB) function and bone formation resulted in weightlessness-induced osteoporosis. Resent studies showed that changes of bone marrow mesenchyme stem cells (BMSCs) were also involved in this process and the transcriptional factor stab2 plays important role in bone formation. However, the cellular and molecular mechanism underlying it remain to be fully elucidated. Based on our previous results, in this study, we introduce the hindlimb unloading rats and clinorotation-induced cell as simulated weightlessness models to explorer the changes of BMSCs and OB function after weightlessness. The alterations of Satb2/Hoxa2/Runx2 expression in BMSCs and OB were to be explored to investigate the mechanisms of osteoporosis induced by weightlessness. In order to further clarify the key molecule in regulating this process, we examine the changes of BMSCs and OB function by interfering the activities of Stab2 and Hoxa2. Our study will provide experiment data for the mechanism of osteoporosis induced by weightlessness. Our finding might help to know the possible mechanism of the BMSCs and OB function alteration and provide some theoretical basis to the protection of osteoporosis induced by weightlessness.

失重性骨质疏松由于没有自限性且防护效果不佳，已成为航天医学中迫切需要解决的重大问题之一，目前认为其发病机制主要是成骨细胞增殖分化障碍及骨形成减少。近期研究认为，失重后骨髓间充质干细胞分化障碍不容忽视，而转录因子stab2成骨分化中发挥重要作用。本研究利用独特的细胞回转器模拟失重效应，并建立尾吊大鼠的模拟失重模型，采用多种分子生物学技术，在前期研究工作的基础上，揭示骨髓间充质干细胞和成骨细胞在失重导致骨丢失中的作用，通过对模拟失重致骨髓间充质干细胞和成骨细胞功能异常的分子机制研究，明确转录因子Satb2/Hoxa2/Runx2参与失重后骨质疏松信号传导的方式，继而对Satb2和Hoxa2的功能活性和表达进行人工干预，发现控制该途径的关键信号转导分子，从而对失重性骨质疏松的机制探讨作出新的补充，为确定能否成为延缓或阻止失重性骨质疏松的药物设计靶点提供新的思路和理论依据。

在太空失重环境中，航天员由于骨骼系统的脱负荷会出现持续性的骨丢失，影响航天任务的完成和威胁航天员健康。然而，其发生机理尚不明确，而且缺乏针对性的防护措施。本研究利用细胞回转器和尾悬吊大鼠模型在细胞和动物整体两个水平模拟失重效应，运用多种细胞生物学技术，开展了模拟失重环境下骨髓间充质干细胞和成骨细胞增殖、周期、凋亡等功能异常变化的研究，探讨了模拟失重致骨髓间充质干细胞成骨分化功能障碍的可能机制，明确了Satb2、Hoxa2相关信号转导通路在骨髓间充质干细胞功能异常的作用及其调控机制，并在模拟失重大鼠上进行了验证。结果发现，模拟失重24h和48h可以使骨髓间充质干细胞和成骨细胞形态发生改变，抑制骨髓间充质干细胞和成骨细胞增殖活性，使其细胞周期受抑，而模拟失重48h可引起骨髓间充质干细胞凋亡增加、成骨分化功能下降；进一步发现模拟失重24h和48h可引起骨髓间充质干细胞和成骨细胞转录因子Satb2、Runx2 mRNA及蛋白表达水平表达显著降低，Hoxa2 mRNA及蛋白显著增高；通过改变Satb2和Hoxa2的活性发现两者在模拟失重致骨髓间充质干细胞成骨分化障碍中发挥重要作用；模拟失重7d、14d、21d、28d大鼠股骨和椎体力学性能显著降低和骨小梁结构的破坏、最大压缩力下降，且随着失重时间的延长骨质疏松逐渐加重；模拟失重7d、14d、21d、28d可致大鼠股骨和椎体Satb2和Runx2表达量显著降低，而Hoxa2 表达量则显著升高，与模拟失重对体外培养的骨髓间充质干细胞结果一致，过表达Satb2可部分对抗模拟失重28d导致的大鼠骨力学性能降低。本项目有关模拟失重下骨髓间充质干细胞和成骨细胞功能异常的研究结果，补充了模拟失重下骨丢失的理论体系，其有关机制的研究将有助于为失重性骨质疏松的防治提供新的思路。