模拟失重下间充质干细胞分泌外泌体的变化及其对造血干细胞的调控作用研究

During spaceflight, the bone marrow hematopoietic system of astronaut was inhibited, leading to abnormal hematopoietic and immune functions. Mesenchymal stem cells play an important role in tissue repair and immune regulation, and exosome-mediated signal transduction between cells plays an important regulatory role in the hematopoietic microenvironment. Our previous data showed that the differentiation ability of mesenchymal stem cells was significantly affected under the simulated weightless environment, and the characters of bone marrow exosomes also changed, but the effects of changes in the exosomes of mesenchymal stem cells under weightless conditions on the hematopoietic stem cells has not been reported. In this study, the exosomes-mediated regulation of hematopoietic stem cells by mesenchymal stem cells was investigated based on a systematic analysis of changes in exosomes of mesenchymal stem cells under simulated microgravity. The aim was to analyze new mechanisms for the exosome-mediated regulation of hematopoietic microenvironment by mesenchymal stem cells under conditions of microgravity with hindlimb unloading models and rotary cell culture system and cell-specific gene knockout mice. This study will provide a new theoretical basis for space protection.

长期航天飞行会导致航天员骨髓造血功能的明显变化，由此引起造血和免疫功能异常。间充质干细胞和造血干细胞共同处在骨髓微环境中，间充质干细胞在组织修复以及免疫调节方面发挥重要功能，外泌体介导的细胞间信号传导在造血微环境中起着重要调控作用。我们前期数据显示，在模拟失重环境下间充质干细胞的分化能力受到显著影响，并且骨髓外泌体的性状也发生改变，但失重条件下间充质干细胞外泌体的变化对造血干细胞的影响未见报道。本研究在系统分析模拟失重条件下间充质干细胞外泌体变化特征的基础上，探讨外泌体介导的间充质干细胞对造血干细胞的调控作用。该研究通过小鼠尾吊以及细胞回转等模拟失重模型，结合细胞特异性基因敲除鼠等工具，从外泌体介导的miRNA胞间通讯的角度，解析间充质干细胞调控造血微环境的新机制，为失重条件下的航天防护提供新的理论基础。

长期航天飞行会导致航天员骨髓造血功能的明显变化，由此引起造血和免疫功能异常。外泌体介导的miRNA转运对模拟失重环境下造血干细胞的影响尚不清楚。本项目围绕模拟失重条件下骨髓微环境中间充质干细胞和外泌体的变化及外泌体介导的miRNA转运对造血干细胞的调控机制开展研究，主要研究结果如下：1) 我们使用尾吊模拟失重小鼠模型，对尾吊 28天的小鼠骨髓外泌体进行了 miRNA 芯片检测，发现骨髓外泌体内大量miRNA表达出现显著改变；2) 尾吊条件下，小鼠骨髓造血干细胞数量增加，凋亡下降，体内外实验显示外泌体可以抑制造血干细胞的凋亡；3) 通过对尾吊小鼠间充质干细胞进行测序，发现表达谱变化基因功能集中在细胞因子分泌等过程，可能涉及到 NF-κ B 及 MAPK 等信号通路；4) 通过测序及体内外实验验证，确定 miR-21 为外泌体抑制造血干细胞凋亡的关键 miRNA；5) 进一步深入研究显示，miR-21降低造血干细胞凋亡是通过靶向Pdcd4发挥作用的。本研究鉴定出外泌体中的miR-21是造血干细胞凋亡保护的有效调节因子，并为减少骨髓造血损伤提供了一种新策略。