The nuclear receptor TR4 orchestrates cytoskeletal organization in a Gα12/ROCK-dependent manner to promote myofibroblast differentiation and tissue fibrosis in systemic sclerosis

本研究的目的是研究TR4在纤维化组织重塑发病机制中的作用，并特别关注SSc作为一种典型的系统性纤维化疾病。我们在互补小鼠模型中评估了tgf - β信号对TR4表达的调控，TR4调控tgf - β诱导的成纤维细胞活化的分子机制，以及靶向灭活TR4对皮肤和肺纤维化的作用。我们的初步结果表明，TR4在SSc中以TGF依赖的方式过表达，TR4与纤维化组织重塑有关，因为TR4的失活降低了多种纤维化相关基因的表达，阻止了肌成纤维细胞分化，减少了胶原的释放，改善了博莱霉素诱导的皮肤和肺纤维化以及tbriact诱导的皮肤纤维化。为了更详细地表征由TR4调控的纤维化信号通路，并验证TR4作为抗纤维化治疗的潜在靶点，具体而言，我们计划使用RNA-seq和核糖核酸-seq多组学方法进一步表征TR4在成纤维细胞向肌成纤维细胞分化中的作用。先前的RNA-Seq结果表明，与细胞骨架组织和Rho/ROCK活性相关的多个基因和功能过程的mRNA水平发生了深刻的变化。因此，我们将研究TR4对G12/ROCK信号的影响，作为TR4对肌成纤维细胞分化调节作用的分子机制。此外，我们将在慢性移植物抗宿主病（cGvHD）小鼠模型中评估成纤维细胞特异性Tr4敲低的抗纤维化作用。最后，我们将评估TR4失活对高级人类体外模型系统纤维化组织重塑的影响。

The aim of the proposed study is to investigate the role of TR4 in the pathogenesis of fibrotic tissue remodeling with a particular focus on SSc as a prototypical systemic fibrotic disease. We evaluate the regulation of TR4 expression by TGFβ signaling, the molecular mechanisms, by which TR4 regulates TGFβ-induced fibroblast activation and the efficacy of targeted inactivation of TR4 on dermal and pulmonary fibrosis in complementary mouse models. We demonstrate in our preliminary results that TR4 is overexpressed in SSc in a TGF-dependent manner, that TR4 is implicated in fibrotic tissue remodeling as inactivation of TR4 decreases the expression of multiple, fibrosis-relevant genes, prevents myofibroblast differentiation, reduces the release of collagen and ameliorates bleomycin-induced dermal and pulmonary fibrosis as well as TBRIact-induced dermal fibrosis. To characterize the profibrotic signaling pathways regulated by TR4 in more detail and validate TR4 as a potential target for antifibrotic therapies, specifically, we plan to further characterize the role of TR4 on fibroblast-to-myofibroblast differentiation using a multi-omics approach with RNA-seq and Ribo-seq. Previous RNA-Seq results showed that identified profound changes in the mRNA levels of multiple genes and functional processes implicated in cytoskeletal organization and Rho/ROCK activity. Thus, we will investigate the effects of TR4 on G12/ROCK signaling as a molecular mechanism underlying the regulatory effects of TR4 on myofibroblast differentiation. Moreover, we will evaluate of the anti-fibrotic effects of fibroblast-specific Tr4 knockdown in a murine model of chronic graft-versus-host-disease (cGvHD). In the end, the efficacy of TR4 inactivation on fibrotic tissue remodeling in advanced human in vitro model systems will be assessed.