ECM Remodeling in Excessive Fibroplasia

描述(由申请人提供)： 长期目标：阐明伤口修复过程中过度瘢痕形成的细胞和分子基础。这一应用将集中在纤溶酶原激活物抑制物-1(PAI-1)的变化在瘢痕疙瘩成纤维细胞过度产生胶原中的作用。临时纤维蛋白基质的蛋白降解和新形成的含有胶原的瘢痕组织的重塑是损伤修复的基本特征。瘢痕疙瘩是一种病因不明的皮肤纤维化的极端形式，由伤口愈合不当引起。利用三维纤维蛋白凝胶培养系统，我们发现瘢痕疙瘩成纤维细胞由于PAL-1的过度表达而导致纤维蛋白降解缺陷。在之前的授予期间，我们在体外和体内证实，PAI-1的过度表达是瘢痕疙瘩成纤维细胞的表型，是导致胶原堆积增加的原因。降低PAI-1活性也可以消除瘢痕疙瘩成纤维细胞中增加的胶原堆积(Tuan等人，Am J Pathol 2003)。此外，我们在体内证明，随着胎鼠皮肤伤口从无疤痕(EL5)向瘢痕形成(E18和之后)修复的转变，PAI-1增加，而抑肽酶，一种uPA/纤溶酶抑制剂，导致E15胎儿皮肤伤口形成疤痕(Huang等人，WRR 2002)。PAI-1是纤溶酶原激活物(PA)/纤溶酶系统的主要抑制物。该系统是纤维蛋白降解、细胞黏附和迁移以及金属蛋白酶(MMPs)激活的中心，而MMPs是胶原蛋白周转所必需的。因此，我们假设“PAL-1通过抑制基质金属蛋白酶的激活和/或通过调节uPA介导的细胞黏附而促进瘢痕疙瘩成纤维细胞中胶原的增加”。PAI-1是转化生长因子-β的下游靶点，瘢痕疙瘩成纤维细胞在基质收缩和胶原合成方面表现出转化生长因子-β介导的差异。因此，我们还假设“转化生长因子-β信号通路的改变和/或PAI-1启动子反应元件的利用是导致瘢痕疙瘩成纤维细胞PAI-1表达增加的原因”。已建立的证据和独特的实验模型将使我们能够通过以下特定目的来检验这些假设： 目的：探讨纤溶酶原激活物-1(PAI-1)在瘢痕疙瘩成纤维细胞基质金属蛋白酶(MMPs)和细胞黏附介导的胶原沉积中的作用。 目的：探讨瘢痕疙瘩成纤维细胞中转化生长因子-β信号转导途径改变和/或PAI-1启动子利用差异导致PAI-1表达升高的生物学机制。

DESCRIPTION (provided by applicant): Long-term goal: To elucidate the cellular and molecular basis of excess scar formation during wound repair. This application will focus on the role of altered expression of plasminogen activator inhibitor-1 (PAI-1) in collagen over-production by keloidfibroblasts. Proteolytic degradation of the provisional fibrin matrix and remodeling of the newly formed collagen-containing scar tissues are essential features in injury repair. Keloids, resulting from improper wound healing, are the extreme form of skin fibrosis with unknown etiology. Using a 3-dimensional fibrin gel culture system, we discovered that keloid fibroblasts are defective in fibrin degradation due to PAl-1 over-expression. In the previous granting period, we established, both in vitro and in vivo, that PAI-1 overexpression is phenotypic of keloid fibroblasts and is causal in the elevated collagen accumulation. Reducing PAI-1 activity also abolishes the elevated collagen accumulation in keloid fibroblasts (Tuan et al., Am J Pathol 2003). In addition, we demonstrated that, in vivo, PAI-1 increases as fetal mouse skin wounds transition from scarless (El5) to scar-forming (E18 and after) repair, and aprotinin, a uPA/plasmin inhibitor, causes scar formation in E15 fetal skin wounds (Huang et al., WRR 2002). PAI-1 is the major inhibitor of the plasminogen activator (PA)/plasmin system. This system is central to fibrin degradation, cell adhesion and migration, and metalloproteinase (MMP) activation, which is essential in collagen turnover. Thus, we hypothesize that "PAl-1 contributes to elevated collagen accumulation in keloid fibroblasts by inhibiting MMP activation and or by modulating uPA-mediated cell adhesion". PAI-1 is a down stream target of TGF-beta, and keloid fibroblasts exhibit TGF-beta-mediated differences in matrix contraction and collagen synthesis. Thus, we also hypothesize that "an altered TGF-beta signaling pathway and or utilization of PAI-1 promoter response elements are responsible for increased PAI-1 expression in keloidfibroblasts" The established evidence and the unique experimental models will allow us to test these hypotheses through the following specific aims: Aim I: To investigate the role of PAI-1 increase in MMP- and cell adhesion-mediated collagen accumulation in keloid fibroblasts. Aim II: To determine the biological mechanism of PAI-1 increase resulting from altered TGF-beta signaling events and/or difference in PAI-1 promoter utilization in keloid fibroblasts.