TGF-beta, matrix, and myofibroblasts in hepatic fibrosis

描述(申请人提供)：肝纤维化是多种原因引起的慢性肝损伤的病理性伤口愈合反应，是肝硬变的前兆，在美国和全世界都会导致显著的发病率和死亡率。 纤维化的中心病理生理事件是前体细胞分化为肌成纤维细胞，肌成纤维细胞是损伤肝脏中异常细胞外基质沉积的主要原因。尽管肌成纤维细胞在纤维化中的作用被广泛认识，但导致肌成纤维细胞进行性激活的事件还不是很清楚。我们以前已经证明了机械因素的重要性，特别是基质硬度，在TW前体细胞、肝星状细胞和门静脉成纤维细胞的肌成纤维细胞分化过程中。此外，我们和其他人已经证明了可溶性因子的重要性，特别是转化生长因子？(转化生长因子？)，在这一过程中。在这项研究中，我们提供的初步数据表明，基质蛋白的细微变化显著改变了肝脏的环境，包括机械环境，不同的肌成纤维细胞前体群体(星状细胞和门静脉成纤维细胞)可能受到胆道和非胆管纤维化这些变化的不同影响。支持这一建议的假设是，基质蛋白、转化生长因子β和力学的变化是相互关联的，共同推动肌成纤维细胞的分化和纤维化的发展。该提案的目标是确定三组核心基质蛋白--交联型胶原蛋白和弹性蛋白、细胞纤维连接蛋白和富含亮氨酸的小分子蛋白多糖--在这些过程中的作用。这将通过三个具体目标来实现：具体目标1：确定LOX介导的胶原和弹性蛋白在早期纤维化中的作用，特别是LOX及其表达的相关异构体的功能力学后果。具体目标#2：确定细胞纤维连接蛋白剪接变异体EIIIA和EIIIB在肌成纤维细胞功能和肝纤维化中的作用，特别是它们在转化生长因子？体内和体外的活化和胶原纤维形成。具体目标#3：确定富含亮氨酸的小分子蛋白多糖LUMICAN和纤维调素在肝脏肌成纤维细胞分化和纤维化中的作用，特别是它们在介导肝脏胶原沉积和机械变化中的作用。这项工作将对基质和力学作为纤维化介质的作用提供独特的见解，并有望阐明肝星状细胞和门静脉成纤维细胞之间的功能差异，以及胆源性和非胆源性纤维化之间的机制差异。此外，这项工作将为可行的抗纤维化治疗确定新的靶点。 公共卫生相关性：这项建议的目标是确定慢性肝病纤维化(疤痕形成)的机制，特别是特定的细胞外基质蛋白和机械因素在纤维化进展中的作用。建议的实验将增加我们对肝纤维化早期事件的了解，并可能导致新的治疗靶点的确定。

DESCRIPTION (provided by applicant): Liver fibrosis is the pathological wound healing response to chronic liver injury from multiple causes and is the precursor to liver cirrhosis, a condition that results in significant morbidity and mortality in the United States and worldwide. The central pathophysiologic event in fibrosis is the differentiation of precursor cells to myofibroblasts, ?-smooth muscle actin-expressing fibrogenic cells responsible for the majority of the abnormal extracellular matrix deposition in the injured liver. Although the role of myofibroblasts in fibrosis is widely appreciated, the events leading to progressive myofibroblast activation are not well understood. We have previously demonstrated the importance of mechanical factors, specifically matrix stiffness, in the myofibroblastic differentiation of tw precursor populations, hepatic stellate cells and portal fibroblasts. Additionally, we an others have demonstrated the importance of soluble factors, particularly transforming growth factor-? (TGF-?), in this process. In this proposal, we present preliminary data suggesting that subtle changes in matrix proteins dramatically alter the environment of te liver, including the mechanical environment, and that different myofibroblast precursor populations (stellate cells versus portal fibroblasts) may be differentially affected by these changes in biliary and non-biliary fibrosis. The hypothesis underlying this proposal is that changes in matrix proteins, TGF-?, and mechanics are interrelated and collectively drive myofibroblast differentiation and the development of fibrosis. The goal of the proposal is to determine the role of three central groups of matrix proteins - cross-linked collagens and elastins, cellular fibronectins, and small leucine-rich proteoglycans - in these processe. This will be achieved through three specific aims: Specific Aim #1: Determine the role of LOX-mediated collagen and elastin cross-linking in early fibrosis, in particular the functional mechanical consequences of the LOXs and the relevant isoforms expressed. Specific Aim #2: Determine the role of the cellular fibronectin splice variants EIIIA and EIIIB in myofibroblast function and liver fibrosis, specifically their role in TGF-? activation and collagen fibrillogeness in vivo and in vitro. Specific Aim #3: Determine the role of the small leucine-rich proteoglycans lumican and fibromodulin in liver myofibroblast differentiation and fibrosis, specifically their roe in mediating collagen deposition and mechanical changes in the liver. This work will provide unique insight into the role of matrix and mechanics as mediators of fibrosis, and is expected to shed light on functional differences between hepatic stellate cells and portal fibroblasts as well as mechanistic differences between biliary and non-biliary forms of fibrosis. Additionally, the work will identify new targets for feasible antifibrotic therapies. PUBLIC HEALTH RELEVANCE: The goal of this proposal is to determine the mechanism of fibrosis (scar formation) in chronic liver disease, in particular the role of specific extracellula matrix proteins and mechanical factors in the progression of fibrosis. The experiments proposed will increase our understanding of the early events in liver fibrosis and may lead to the identification of new therapeutic targets.