成骨细胞mTORC1调控血小板生成及其机制研究

Megakaryocytes fragment into individual thrombocytes by proliferation and differentiation in bone marrow microenvironment, and the other components in bone marrow regulate thrombocytopoiesis by bone marrow microenvironment. However, it is unclear that the mechanism of regulation of thrombocytopoiesis by osteoblasts. Our previous works demonstrated knockdown of TSC1, the upstream molecule on Mammalian target of rapamycin complex 1 (mTORC1), in the osteoblasts resulted in the proliferation barrier of megakaryocytes and thrombocytopoiesis dysfunction in mice followed by specific activation of mTORC1 pathway, nevertheless, the development of erythroid and granule lineages in bone marrow didn’t affect. It suggests that osteoblastic mTORC1 regulate thrombocytopoiesis by bone marrow environment. In this study, we aim to demonstrate the roles of mTORC1 in osteoblast cells in megakaryocyte proliferation and thrombocytopoiesis by using the mice and cells with osteoblast cell-specific deletion of TSC1 and Raptor, which specifically inactivated mTORC1, and further investigate the mechanism of regulation of thrombocytopoiesis by the osteoblasts through increasing or decreasing the level of local secretory factors, providing new methods in regulatory mechanism of thrombocytopoiesis in bone marrow microenvironment and the potential therapeutic target for prevention and treatment of thrombocytopoiesis dysfunction.

巨核细胞在骨髓微环境中增殖、分化形成血小板，骨髓中其他细胞成分可通过骨髓微环境调节血小板形成，但成骨细胞在血小板生成中的作用及其调节机制不清楚。我们的前期工作发现，在成骨细胞中敲除雷帕霉素靶蛋白复合物1（mTORC1）的上游抑制分子TSC1，使mTORC1通路在小鼠成骨细胞中特异地活化，小鼠出现巨核细胞增殖与血小板生成障碍，但红系与粒系发育不受影响，提示成骨细胞mTORC1可能通过骨髓微环境调节血小板生成。本课题拟以成骨细胞特异敲除TSC1和Raptor(使mTORC1失活)的小鼠与细胞为模型，从分子、细胞及整体水平研究成骨细胞mTORC1在巨核细胞增殖分化和血小板生成中的作用，探讨mTORC1通过促进或抑制成骨细胞分泌局部因子改变骨髓微环境，从而调控血小板生成的分子机制，为血小板生成的调控机制提供新观点，为血小板生成或（和）功能障碍相关疾病的防治提供依据和潜在的药物治疗靶点。

严重的血小板减少症是恶性肿瘤患者接受骨髓抑制化疗的一个重大的挑战。了解骨髓微环境中的血小板生成巨核细胞发育生物学可能有助于开发新的疗法刺激血小板生成和防止血小板减少症。此研究主要报道成骨细胞分泌白细胞介素9，刺激IL-9受体促进巨核细胞/ STAT3信号。成骨细胞雷帕霉素靶蛋白复合物1负调控白介素9的产生和NF-κB信号通路。激活雷帕霉素靶蛋白复合物1抑制巨核细胞白介素9的产生，而雷帕霉素靶蛋白复合物1失活增加白介素9的产生和增强小鼠巨核细胞和血小板数。而且在小鼠模型中发现白介素9能够刺激巨核生成，而中和内源性白介素9 或者耗竭白介素9受体可抑制此过程。重要的是，低剂量的白介素9有效地预防化疗引起的血小板减少症和加速血小板恢复。这些数据表明白介素9是调节巨核生成必不可少的因子，有望成为治疗血小板减少症的患者的有效的治疗剂。