血管紧张素II-1型受体在纤维化力学信号转导中的作用机制

Fibrosis, which contributes to as much as 45% of the world deaths, is tightly regulated by the differentiation of fibroblasts to myofibroblasts (i.e., the myofibroblast differentiation) and is closely related to matrix stiffening. Angiotensin II type 1 receptor (AT1R) plays a critical role in matrix stiffness-induced myofibroblast differentiation. However, currently the underlying mechanism of AT1R-mediated matrix stiffness-induced myofibroblast differentiation is not clear. In this proposal, hydrogels with dynamically and in situ tunable stiffness are fibricated and applied for culturing primary caridac fibroblasts. The cell membrane tension is varied and the corresponding activated state of AT1R is characterized to determine the role of the cell membrane tension in matrix stiffness-induced AT1R activation. Further studies are performed to uncover the key signaling molecular pathways involved in AT1R-mediated matrix stiffness-induced myofibroblast differentiation, with focus on transforming growth factor-β1/Smad2/3 and Yes-associated protein and transcriptional co-activator with PDZ binding motif (YAP/TAZ) signaling pathways. The potential crosstalk between these two pathways in fibrotic mechanotransduction is also investigated. Finally, a mechano-chemical coupling model is developed to capture the AT1R-mediated matrix stiffness-induced myofibroblast differentiation process, and the underlying biophysical and molecular mechanisms are explored by by referring to the experimental results. We expect that this research will provide useful references for future mechanism study and treatment of fibrotic diseases from the perspective of mechanobiology.

纤维化的产生和发展与肌成纤维细胞（MyoFBs）表型转化及基质硬度的变化密切相关，而血管紧张素II-1型受体（AT1R）在基质硬度调控的MyoFBs表型转化中发挥了关键作用，但是其作用机制不清楚。本项目拟制备力学性能原位可调的水凝胶基质培养原代心肌成纤维细胞，在调控细胞膜张力的同时检测AT1R激活状态，明确细胞膜张力在基质硬度激活AT1R中的作用；探索AT1R介导的MyoFBs关键纤维化力学信号转导通路，着重明确转化生长因子-β1/Smad2/3和转录共激活因子YAP/TAZ相关信号通路的作用，并探明其串话关系；最后，建立基质硬度经AT1R及其关键力学信号转导通路调控MyoFBs表型转化的力-化耦合模型，并结合相关实验探讨AT1R在纤维化力学信号转导中的作用机制。本项目研究结果将有望为纤维化发生发展机制的阐明及纤维化相关疾病的防治提供新的力学生物学依据。

纤维化（fibrosis）在人体多种组织器官中均可发生，是许多疾病致残、致死的主要原因。统计数据表明，人类一半以上的疾病死亡率都与纤维化的发生发展密切相关，而临床上缺乏针对纤维化的有效治疗手段和药物。纤维化的发生发展与细胞力学微环境的变化密切相关，而目前基质力学影响纤维化主要效应细胞表型转化的规律和力学生物学机制不清楚。本项目着重围绕基质力学调控成纤维细胞表型转化的关键机制开展了相关研究，制备了基质刚度原位可调的胶原-海藻酸盐复合水凝胶，实现了基质刚度和细胞铺展的独立调控，证明了硬基质和转化生长因子β1（TGF-β1）促进心肌成纤维细胞（CF）表型转化与细胞铺展密切相关；构建了大鼠心肌梗死模型和力学调控的体外心肌纤维化模型，发现了血管紧张素II-1型受体（AT1R）和Yes相关蛋白（YAP）在基质刚度调控的CF表型转化中具有上下游关系；建立了基质刚度依赖的网络模体动力学模型，结合实验分析表明AT1R并不参与CF形成不可逆转表型的过程，而整合素-Piezo1力学正反馈回路是使CF形成不可逆表型的主要原因，并证实了通过同时干扰新发现的力学正反馈回路和调节基质刚度，可以逆转CF纤维化表型；进一步，发现了纤维化过程中基质塑性发生显著变化，证明了基质塑性的降低促进了细胞纤维化表型转化，揭示了细胞骨架张力在基质塑性调控的成纤维细胞表型转化中的作用机制。上述研究结果为纤维化相关疾病的病理机理和防治研究提供了力学生物学参考。