The role of alpha-v integrins on activated fibroblasts in pulmonary fibrosis

描述(申请人提供)：肺纤维化是指当器官功能受损时，以纤维化组织替代正常肺实质的进行性和不可逆性改变，是一种主要的临床负担。这种疾病的治疗选择严重有限，突显出迫切需要在器官衰竭之前采取治疗措施来减缓和/或阻止疾病的进展。肺纤维化的特征包括成纤维细胞局灶性扩张 细胞外基质的沉积和激活的成纤维细胞是这一过程的关键执行者。众所周知，转化生长因子是推动肺纤维化形成的一种强有力的促纤维化细胞因子，转化生长因子通过与整合素的相互作用发挥作用，整合素是一种跨膜受体家族，由一个亚单位和一个亚单位组成。5个整合素共有v亚基，包括v 1、v 3、v 5、v 6和v 8，均可激活转化生长因子。虽然v6的表达仅限于上皮细胞，但其他的表达在包括肺上皮细胞在内的多个器官的成纤维细胞中表达。先前的研究表明，限制性的6可以在空间上激活转化生长因子，这种由6介导的转化生长因子的激活被证明在肺纤维化形成过程中起着重要作用。与6相比，其他整合素对成纤维细胞在肺纤维化中的作用了解较少。值得注意的是，我们的实验室最近在几个经典模型中发现，在体内删除周细胞/成纤维细胞上的v整合素可以保护小鼠免受纤维化的影响，包括 博莱霉素诱导的肺纤维化，单侧输尿管梗阻引起的肾小管间质纤维化，以及四氯化碳诱导的肝纤维化，提示 周细胞/成纤维细胞上的整合素是跨实体器官纤维化形成的中心介质。这项拟议研究的一个目标是确定哪些成纤维细胞亚群对整合素介导的肺纤维化的发展至关重要。目前的文献表明，肌成纤维细胞是纤维形成过程中主要的活化成纤维细胞，肌成纤维细胞是表达SMA的成纤维细胞亚群；然而，这一观点仍然存在争议，而且肌成纤维细胞在体内的具体作用还没有得到严格的研究。因此，这项研究产生了一种可以对肌成纤维细胞进行特定靶向和基因操作的小鼠品系，并将检查肌成纤维细胞上整合素的丢失是否保护小鼠免受博莱霉素诱导的肺纤维化的影响。此外，通过结合细胞类型特异性报告鼠和细胞分选技术，将表征整合素对激活的成纤维细胞的调节作用。最后，利用遗传学和药理学工具，将确定在体内哪个或多个成纤维细胞整合素(S)在肺纤维化中起关键作用。总之，这项拟议的研究将明确体内肌成纤维细胞在肺纤维化形成中的作用，并可能为开发抗纤维化药物治疗肺纤维化揭开新的治疗靶点(S)。

DESCRIPTION (provided by applicant): Pulmonary fibrosis, the progressive and irreversible replacement of normal lung parenchyma with fibrotic tissues, is a major clinical burden when organ function is compromised. Treatment options for this disease are severely limited, underscoring the urgent need for therapies to attenuate and/or halt disease progression before organ failure. Characteristic features of pulmonary fibrosis include focal expansion of fibroblasts and deposition of extracellular matrix, and activated fibroblasts are key executors of this process. TGF¿ is well known as a potent pro-fibrogenic cytokine driving lung fibrogenesis, and TGF¿ exerts much of its effects via interactions with integrins, a family of transmembrane receptors which consist of a ¿ and a ¿ subunit. Five integrins share the ¿v subunit, including ¿v¿1, ¿v¿3, ¿v¿5, ¿v¿6, and ¿v¿8, and all can activate TGF¿. While expression of ¿v¿6 is restricted to the epithelium, others are expressed in fibroblasts in multiple organs including lung Epithelium-restricted ¿v¿6 has been previously shown to spatially activate TGF¿, and this ¿v¿6-mediated TGF¿ activation has been demonstrated as an important player during lung fibrogenesis. Compared to ¿v¿6, the role of other ¿v integrins on fibroblasts in pulmonary fibrosis is less understood. Notably, our lab has recently found that in vivo deletion of ¿v integrins on pericytes/fibroblasts protects mice from fibrosis in several classic models, including bleomycin-induced pulmonary fibrosis, unilateral ureteral obstruction-induced renal tubulointerstitial fibrosis, and carbon tetrachloride-induced hepatic fibrosis, which suggests that ¿v integrins on pericytes/fibroblasts are central mediators during fibrogenesis across solid organs. One goal of this proposed research aims to identify which sub-population of fibroblasts is critical for this ¿v integrin-mediated development of pulmonary fibrosis. Current literature implicates myofibroblasts, the subpopulation of fibroblasts expressing ¿-SMA, as the major activated fibroblasts during fibrogenesis; however, this idea remains controversial, and the specific role of myofibroblasts has not been rigorously investigated in vivo. As such, a mouse line in which myofibroblasts can be specifically targeted and genetically manipulated has been generated for this research, and whether loss of ¿v integrins on myofibroblasts protects mice from bleomycin-induced pulmonary fibrosis will be examined. In addition, by combining cell-type specific reporter mice and cell sorting techniques, the regulatory role of ¿v integrins on activate fibroblasts will be characterized. Finally, by using both genetic and pharmacologic tools, which one or more fibroblast ¿v integrin(s) is/are critical to contribute to pulmonary fibrosis in vivo wll be determined. Overall, this proposed research should define the role of myofibroblasts in vivo during lung fibrogenesis, and may unravel new therapeutic target(s) for the development of anti-fibrotic agents to treat pulmonary fibrosis.