Myofibroblast differentiation and fibrosis are mediated by TRPV4 mechanosensing

描述(申请人提供)：特发性肺纤维化(IPF)是一种致命的纤维性肺疾病，没有有效的药物治疗。纤维化肺修复的生物学过程及其分子驱动因素尚未完全阐明。肌成纤维细胞是体内纤维组织修复过程中的关键细胞。尽管机械信号(内部产生的细胞张力、基质硬度)和转化生长因子-β启动的信号对于成熟的肌成纤维细胞的最佳分化都是必不可少的，但机械信号被转导/维持的实际分子途径或其对体内纤维化的下游影响尚不清楚。我们发现瞬时受体电位香草酸家族(TRPV4)中的一个离子通道作为机械传感器/转导分子促进肌成纤维细胞的分化。这种机械敏感的钙渗透通道在局部质膜拉伸时迅速激活。TRPV4通过增强基质僵硬的转化生长因子-β信号和PI3K依赖的方式来介导肌成纤维细胞分化和肺纤维化形成的假设，将在三个特定的目标下进行测试。目标1中的工作将确定TRPV4通道功能在反应转化生长因子β时增强的机制。AIM 2的工作将确定PI3K细胞内信号通路如何影响TRPV4介导肌成纤维细胞分化的功能。通过这项工作，将明确特发性肺纤维化患者肺成纤维细胞中TRPV4活性上调的潜在机制。目标3中的工作将在两种不同的肺纤维化小鼠模型中确定TRPV4在活体肺纤维化形成中的作用。这项工作的完成将为TRPV4通道影响肌成纤维细胞分化的机制、其细胞内信号通路以及TRPV4在实验性肺纤维化中的作用提供确凿的证据。

DESCRIPTION (provided by applicant): Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disorder with no effective medical treatment. The biological processes that underlie fibrotic lung repair and their molecular drivers have yet to be fully elucidated. Myofibroblasts are critica to the in vivo fibrogenic tissue repair process. Although both a mechanical signal (internally-generated cell tension, matrix stiffness), and a TGF-¿-initiated signal are essential for optimal mature myofibroblast differentiation, the actual molecular pathway by which the mechanical signal is transduced/maintained, or its downstream consequences on in vivo fibrosis, are not known. We have made the novel observation that an ion channel in the transient receptor potential vanilloid family (TRPV4) serves as a mechanosensor/transducer to promote myofibroblast differentiation. This mechanosensitive, calcium permeable channel is rapidly activated upon local plasma membrane stretching. The hypothesis that TRPV4 mediates myofibroblast differentiation and pulmonary fibrogenesis by potentiating the TGF-¿ signal in a matrix stiffness, and PI3K-dependent manner, will be tested in three specific aims. The work in Aim 1 will determine the mechanism whereby the TRPV4 channel function is increased in response to TGF-¿. The work in Aim 2 will determine how the PI3K intracellular signaling pathway affects TRPV4 function to mediate myofibroblast differentiation. Through this work, the underlying mechanism for the observed upregulation of TRPV4 activity in lung fibroblasts from idiopathic pulmonary fibrosis patients will be defined. The work in Aim 3 will determine the role of TRPV4 in pulmonary fibrogenesis in vivo, in two distinct murine models of pulmonary fibrosis. When completed, this work will provide conclusive evidence for the mechanism of TRPV4 channel's effect on myofibroblast differentiation, its intracellular signaling pathway, and the rol of TRPV4 in experimental pulmonary fibrosis.