Exosome介导的microRNA转运在失重性骨丢失对造血微环境影响中的作用及机制研究

Weightlessness induced bone loss is one of the limit factors during long term space flight, which is accompanied by the changes of bone marrow environment and leads to diseases related to osteoimmunology. microRNA plays an important role in the regulation of osteoblast, osteoclast, hematopoiesis and other stromal cells in the bone marrow. microRNA functions through the repression of translation and degradation of mRNA, but also it can be enveloped in the exosomes and secreted into the medium and mediates intercellular signaling transduction. At present, the changes of microRNA in the bone and bone marrow under weightlessness induced bone loss have not been reported. In this study, we will characterize the changes of microRNA in osteoblasts and osteoclasts and bone marrow fluids and their transporation from these cells to their targets. The function of these target cells will be analyzed. By constructed osteoblast or osteoclast specific transgenic or gene knockout mice, we will explore the regulation of osteoblasts or osteoclasts derived microRNA on the hematopoiesis stem cell, progenitor cells or mesenchymal cells in the bone marrow. This project will disclose new mechanisms to keep the homeostasis under weightlessness induced bone loss from the view of exosomes mediated intercellular communications and improve the theory of ostoimmunology.

失重性骨丢失是限制长期载人航天飞行的关键因素之一，骨与骨髓微环境的变化相伴而生，由此所致的骨免疫相关疾病的发生严重影响着航天员的健康。microRNA在骨组织细胞及造血干细胞的发育调控中起着重要的作用，exosome介导的miRNA转运是细胞间信号传递的一种新方式。造血微环境中骨组织细胞microRNA的变化规律、分泌特征及其对靶细胞的影响还未见报道。本研究在系统分析模拟失重条件下骨组织细胞和造血微环境细胞中microRNA变化特征的基础上，探讨exosome介导的细胞间microRNA转运机制及生物学效应。通过构建成骨或破骨特异的基因敲除与转基因小鼠，解析microRNA介导的骨组织细胞对造血微环境的调控作用。该研究将首次从exosome介导的microRNA胞间通讯的角度，解析失重性骨丢失所致机体稳态变化的新机制，探讨骨髓微环境调控的新策略，并进一步丰富和完善骨免疫调控理论。

失重性骨丢失是限制长期载人航天飞行的关键因素，骨与骨髓微环境的变化相伴而生，由此所致的造血微环境的变化与航天员的健康密切相关。该研究深入解析了失重性骨丢失、造血微环境的变化特征、调控机制、以及从exosome介导的microRNA胞间通讯的角度揭示了失重性骨丢失对造血微环境的影响。研究发现：1）机械力敏感的离子通道蛋白Piezo1是骨组织感受力学信号的分子基础，核内长链非编码RNA NEAT1 形成的无膜细胞器Paraspeckle发挥着关键的调控作用。钙调氯离子通道蛋白ANO1和线粒体钙通道蛋白MCU在去负荷状态下增加破骨细胞的活性促进失重性骨丢失的发生。2）揭示了失重性骨丢失导致机体免疫及骨髓微环境的变化特点，通过竞争性或系列性骨髓移植实验发现造血干细胞的血系重建能力显著下降，其功能的变化主要与细胞凋亡抑制和内质网应激密切有关。3）通过外泌体的示踪标记以及对骨组织外泌体分泌受阻小鼠的表型分析，揭示了外泌体对造血微环境的调控作用。成骨细胞来源的外泌体可以进入骨髓细胞保护辐射对造血微环境的损伤。骨组织中Piezo1、Neat1、Ano1等基因的敲除导致机体骨髓微环境及免疫功能发生了显著的变化。4）通过对成骨/破骨细胞，造血干细胞和骨髓exosome中miRNA进行测序及交叉分析筛选到了具有关键调控作用的miRNAs，深入研究了骨组织来源的miR-21和miR-214对造血干细胞的调控作用。5）发现骨组织细胞来源的外泌体对靶细胞的识别机制，其中EphrinA2和EphA2的作用是靶向调控的基础，确定了外泌体中包含的关键miRNA在靶细胞中的作用机制。该研究首次从exosome介导的microRNA胞间通讯的角度，解析失重性骨丢失所致机体造血微环境稳态变化的新机制，丰富和完善了骨免疫调控理论，并且对航天失重条件下骨髓微环境的调控提供了新的策略。