TGF-β1加速内皮干细胞向平滑肌细胞分化进而影响低氧诱导的肺血管重构

Pulmonary vascular remolding is the major pathological alteration of hypoxia-induced pulmonary arterial hypertension. However, the mechanism involved remains elusive. Previous studies mostly focused on involvement of smooth muscle cells (SMCs), without paying much attention to differentiation of endothelial progenitor cells (EPCs). Circulating EPCs are originated from bone marrow and have the capacity to differentiate into SMCs through a process called EnMT, during which TGF-β1 plays a critical role. Our preliminary experiments identified a positive relationship between pulmonary vascular remolding and TGF-β1. Therefore, we hypothesize that hypoxia increases production of TGF-β1, which in turn induces homing of EPCs to injured pulmonary vessel wall and its differentiation into SMCs. In the proposed research project, we will investigate the expression of TGF-β1 in EPCs and its effect on EPCs' proliferation in a hypoxia-induced pulmonary hypertension animal model. Functionally, we will study homing of fluorescently labeled EPCs with or without TGF-β1 pretreatment. Furthermore, we will elucidate possible mechanisms involved in differentiation of EPCs under hypoxia condition using gene over-expression and receptor inhibition of TGF-β1. Thereby our aim is to uncover new molecular mechanisms promoting pulmonary vascular remolding and identify novel drug targets for pulmonary arterial hypertension.

低氧性肺动脉高压的关键病变是肺血管重构，其机制仍未明确。既往研究更多关注血管平滑肌细胞（SMC）的增殖，而对内皮干细胞等分化为SMC的研究甚少。循环血内皮干细胞可以分化为SMC，其分化与TGF-β1相关。我们前期在体实验研究发现低氧性肺血管重构与TGF-β1成正相关。因此我们假设：低氧刺激TGF-β1分泌增多，诱导内皮干细胞向受损肺血管归巢并向SMC分化，促进肺血管的重构。本课题拟建立低氧诱导的肺动脉高压动物模型，应用体内诱导EPC增殖或体外荧光标记EPC回输等方法，观察肺组织及血液中TGF-β1的表达及EPC归巢、分化情况。低氧条件下体外培养CD133+内皮干细胞株，应用基因转染、受体阻断等方法, 观察低氧条件下TGF-β1对 EPC分化功能的影响及可能的机制。从而阐明低氧时TGF-β1诱导EPC向SMC分化在肺血管重构中的作用及机制，为肺血管重构研究提供新的思路和方向。

低氧性肺动脉高压以慢性进展，高死亡率和低治疗反应性为特点的慢性气道疾病，关键病变是肺血管重构，其机制仍未明确。气道的慢性炎症和间质重塑是也是肺血管重构主要发病机制和病理特点之一。既往更多的是关注肺动脉平滑肌细胞的增殖，研究干细胞对肺血管重构的影响相对较少，我们成功构建内皮干细胞及低氧肺动脉高压的动物模型，完成EPC体外荧光标记等，研究结果显示低氧诱导肺动脉平滑肌细胞增殖参与肺血管重构，低氧诱导内皮干细胞自分泌TGF-β1，但我们研究发现低氧条件下TGF-β1不同时间点(0, 3，6，12，24hr)刺激内皮干细胞，无法通过平滑肌细胞表型转化的途径而参与肺血管重构。我们探索性的发现LPS通过PI3K/AKT信号通路介导内皮干细胞抗炎因子IL-1ra表达，调控细胞外基质的旁分泌而参与肺血管重构。同时，我们发现其他干细胞如间充质干细胞，TGF-β1通过ERK1/2信号通路介导CCN4调控间充质干细胞对细胞外基质collagen1表达及通过Snail转录因子调控间质变vimentin的影响而参与血管重构，TGF-β1诱导心血管前体细胞分化成平滑肌细胞表型而参与血管重构。探讨干细胞与炎症反应和间质重塑过程的关系及调控网络，为干细胞干预肺血管重构的治疗提供新的理论依据，启发了未来肺血管重构新的研究思路和方向。