METALLOPROTEINASE IN NORMAL AND KERATOCONUS CORNEAS

圆锥角膜 (KC) 是一种影响人类角膜的异常变薄的疾病 主要是年轻人。 它的发病率为 2,000 分之一，现在 这是美国角膜移植的主要原因。 在 过去一段时间，PI 确定，在 KC 角膜和 KC 角膜细胞中，基质金属蛋白酶-2 (MMP-2) 增加 活动与正常相比。假设 MMP-2 及其 金属蛋白酶相关组织抑制剂 (TIMP) 很重要 在一系列事件中最终导致角膜变薄 通常调节 MMP-2 活性的机制发生了改变 在 KC 角膜中。 由此产生的蛋白酶活性增加影响两个 角膜区域、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 活性增加的目标可能是 VI 型胶原蛋白，它充当 蛋白聚糖和胶原纤维之间的稳定物质 基质。为了阐明 MMP 在 KC 病因学中的作用，PI 提出：1）确定MMP-2的结构是否存在缺陷 和/或 TIMP 可以解释异常的酶活性； 2） 确定 KC 角膜是否有 TIMP-3 的改变（新描述 抑制剂）和/或MT-MMP（MMP-2的细胞膜结合激活剂）； 3） 确定角膜 ECM 成分，例如 XII 型胶原蛋白和 蛋白多糖，对 MMP-2 敏感； 4) 判断是否裂解后 与 MMP-2、VI 型胶原蛋白和其他易受影响的 ECM 成分相互作用 通常含有胶原蛋白和蛋白聚糖； 5) 识别基因 KC 中差异表达。拟议的研究将显着 增进我们对 KC 和基因表达变化的理解 导致这种病症。此外，这些研究还将提供基础 有关正常角膜中 MMP 活性调节的信息和 蛋白酶作用对角膜 ECM 结构的影响 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.