力感应细胞源性外泌体及其microRNA货物介导的细胞间通讯在骨重建稳态中调控机制及干预策略的研究

Mechanical force is an important regulator of bone remodeling homeostasis. Till now there is still no effective strategy to prevent and treat mechanical loading deficiency caused-disuse osteoporosis. Recent evidence demonstrates that osteocytes, which has long been considered as main mechanosensors of bone, regulate bone remodeling by detecting and transmitting mechanical signals to osteoblasts and osteoclasts. However, the mechanism of intercellular communication is unclear. Our previous research found that osteocytes responsed to mechanical loading and released exosomes sorting specific microRNA cargos to the extracellular microenvironment, which were subsequently internalized by adjacent osteoblasts and osteoclasts. We then propose scientific hypothesis that exosomes may act as the messenger of mechanical signal and regulate bone remodeling homeostasis through mediating intercellular communication and transferring functional cargos to osteoblasts and osteoclasts. The aim of the study is to capture and trace osteocytes-originated exosomes; using microarray and bioinformatic analysis to investigate the microRNA cargos and target genes; further in vitro and in vivo experiments focusing on intervention on exosome-microRNA to repress and rescue the negative balance of bone remodeling. The current study may elucidate the new mechanism of intercellular communication between exosome and bone remodeling and provide an potential anabolic strategy for disuse osteoporosis caused by pathological mechanical loading.

力学因素在调控骨重建稳态中起重要作用，由应力缺失所致废用性骨质疏松临床尚无有效防治措施。骨细胞作为核心力感应细胞感知转导力学信号至成骨/破骨细胞调控骨重建稳态，但其间通讯机制尚未清晰。前期研究发现：骨细胞对力学负载产生响应，将特异miRNA货物分选组装入外泌体释放至细胞外微环境并被毗邻成骨/破骨细胞摄取。据此提出科学假说：外泌体可能作为响应力学信号的骨细胞信使，通过细胞间通讯将功能货物传递至成骨/破骨受体细胞影响其功能及行为，调控骨重建稳态。本研究拟捕获载荷响应前后骨细胞源性外泌体，示踪追溯其在骨重建单位细胞间通讯功能及命运；利用芯片拷问miRNA货物表达谱；通过生物信息学方法锚定骨重建中力响应相关靶标基因；进而在体内外求证，通过靶向干预外泌体-miRNA环节，阻遏反转骨重建负平衡发生。探索外泌体与骨重建稳态关系为阐明细胞间通讯机制挖掘全新研究方向，为临床防治废用性骨质疏松提供潜在药靶。

长期卧床或制动（如骨折或脊髓损伤）、太空失重等生物力学因素导致的废用性骨质疏松症（Disuse osteoporosis，DOP）是一个重大的社会公共卫生问题，严重影响人类健康及生活质量，目前其具体的发病机制尚未清晰，临床仍缺乏有效靶向干预手段。本课题按照研究计划进行，通过研究外泌体在介导骨髓间充质干细胞（BMSCs）和破骨前体细胞之间的通讯作用，发现力学刺激下的BMSCs源性外泌体可有效抑制破骨细胞分化。通过动物体内模拟废用性骨质疏松并运用BMSCs源性外泌体进行治疗，发现力学刺激下的BMSCs源性外泌体可有效挽救模型小鼠骨量丢失。通过TRAP染色表明，经力学刺激下的BMSCs源性外泌体在体内也可减少破骨细胞的数量。Small RNA测序发现力学刺激下BMSCs源性外泌体中存在差异表达的small RNA，夯实了进一步探讨力学刺激下外泌体在骨代谢中的通讯机制的实验基础。此外，本项目还资助培养博士生1名，正在培养博士生1名，部分资助其他miRNA等相关研究并发表SCI论文3篇。