METALLOPROTEINASE IN NORMAL AND KERATOCONUS CORNEAS

圆锥角膜(KC)是一种人类角膜的异常变薄，影响 主要是年轻的个体。它的发病率为1/2,000，现在是 这是美国角膜移植的主要原因。在 在过去的一段时间里，PI在KC角膜和KC中都建立了 角质形成细胞中，有基质金属蛋白酶-2(MMP2)的增加 活动量与正常相比。假设是基质金属蛋白酶-2及其受体 相关的金属蛋白酶组织抑制物(TIMPs)是重要的 在最终导致角膜变薄和 正常调节基质金属蛋白酶-2活性的机制(S)发生改变 在KC眼角膜中。由此导致的蛋白水解酶活性的增加影响了两个 角膜、上皮基底膜/鲍曼层和 细胞外基质(ECM)的结构成分。一个重要的 活性增加的靶点可能是VI型胶原，它起着一种 蛋白多糖与胶原纤维之间的稳定物质 基质。为阐明MMPs在KC发病机制中的作用 建议：1)确定基质金属蛋白酶-2的结构是否存在缺陷 和/或TIMPs，这可能是酶活性异常的原因； 确定KC角膜是否存在TIMP-3的改变(新描述 抑制物)和/或MT-MMP(细胞膜结合的基质金属蛋白酶-2激活剂)；3) 确定角膜ECM成分，例如XII型胶原和 蛋白多糖，对基质金属蛋白酶-2敏感；4)确定是否在切割后 在基质金属蛋白酶-2的作用下，VI型胶原和其他易感的ECM成分相互作用 通常与胶原蛋白和蛋白多糖有关；5)识别哪些基因是 以Kc为单位进行差异表达。拟议的研究将极大地 加深我们对KC及其基因表达变化的理解 导致了这种混乱。此外，这些研究还将提供基本的 正常角膜及角膜基质金属蛋白酶活性调节的研究进展 蛋白水解酶作用对角膜ECM结构和细胞外基质的影响 组织。

Keratoconus (KC) is an abnormal thinning of the human cornea affecting mainly younger individuals. It has an incidence of 1 in 2,000 and is now a leading cause for corneal transplantation in the United States. In the past period the PI established that, in both KC corneas and KC keratocytes, there is an increase in matrix metalloproteinase-2 (MMP-2) activity compared to normal. The hypothesis is that MMP-2 and its associated tissue inhibitors of metalloproteinases (TIMPs) are important in the cascade of events which ultimately results in corneal thinning and that the mechanism(s) which normally regulates MMP-2 activity is altered in the KC cornea. The resulting increase in protease activity affects two areas of the Cornea, the epithelial basement membrane/Bowman's layer and structural components of the extracellular matrix (ECM). An important target of the increased activity may be type VI collagen, which acts as a stabilizing substance between proteoglycans and the collagen fibrils in the stroma. To clarify the role of MMPs in the etiology of KC, the PI proposes to: 1)Determine if there are defects in the structure of MMP-2 and/or TIMPs which would account for the abnormal enzyme activity; 2) Determine if KC corneas have an alteration in TIMP-3 (newly described inhibitor) and/or MT-MMP (cell membrane bound activator of MMP-2); 3) Determine if corneal ECM components, e.g., type XII collagen and proteoglycans, are susceptible to MMP-2; 4) Determine if after cleavage with MMP-2, type VI collagen and other susceptible ECM components interact normally with collagens and proteoglycans; 5) Identify genes which are differentially expressed in KC. The proposed studies will significantly advance our understanding of KC and the changes in gene expression which lead to this disorder. In addition, these studies will also provide basic information on the regulation of MMP activity in the normal cornea and the consequences of protease action on corneal ECM structure and organization.