Corneal Repair: uPA and extracellular matrix

描述：角膜伤口愈合无瘢痕再生角膜透明度。愈合后有疤痕的角膜有混浊和视力障碍。因此，了解影响再生而不是纤维化愈合的途径是治疗促进健康修复的重要一步。角膜受伤后，基质中通常静止的细胞分化为成纤维细胞，成纤维细胞在迁移时分泌蛋白酶。该建议的重点是细胞外丝氨酸蛋白酶，尿激酶型纤溶酶原激活剂（uPA），这是由角膜成纤维细胞表达创伤后的贡献。当uPA与其细胞表面受体uPAR结合时，uPA在细胞-基质界面产生纤溶酶。纤溶酶降解细胞外基质（ECM）并激活潜在的生长因子，如TGF β。转化生长因子刺激成纤维细胞增殖和迁移，并诱导能动的成纤维细胞分化为非能动的肌成纤维细胞，这对于基质收缩和伤口闭合是必需的。TGF β可能引起其双重作用的一种方式是通过诱导纤溶酶原激活抑制剂（派-1）的表达。有大量数据表明派-1的相反作用是浓度依赖性的：低浓度的派-1诱导细胞增殖和迁移，而高浓度则抑制这些过程。在该提议中测试的假设是，角膜受伤后，局部派-1浓度通过与Vn结合来介导。此外，低浓度的派-1导致角膜成纤维细胞增殖和迁移，而高浓度的派-1诱导uPA/uPAR下调并导致肌成纤维细胞分化。具体目的是确定1）TGF β浓度是否调节派-1水平、uPA活性和肌成纤维细胞分化。 2)Vn介导TGF β和派-1对uPA活性、细胞迁移和肌成纤维细胞分化的影响。 3)Vn、派-1和整合素表达在整个伤口愈合过程中随着基质表型的变化而变化。 4)uPAR裂解成非uPA结合形式抑制细胞迁移并诱导成肌纤维细胞分化。这些研究的结果将导致更好地理解引导再生伤口修复的机制。

DESCRIPTION: Corneal wound healing without scarring regenerates corneal transparency. Corneas that heal with scarring have opacities and obstructed vision. Thus, understanding the pathways that influence regenerative rather than fibrotic healing is an essential step towards therapeutically promoting healthy repair. Upon corneal wounding, the normally quiescent cells in the stroma differentiate into fibroblasts, which secrete proteases as they migrate. This proposal is focused on the contributions of the extracellular serine protease, urokinase-type plasminogen activator (uPA), which is expressed by corneal fibroblasts after wounding. When uPA binds to its cell-surface receptor, uPAR, uPA generates plasmin at the cell-matrix interface. Plasmin degrades extracellular matrix (ECM) and activates latent growth factors such as TGF¿. TGF¿ stimulates fibroblast proliferation and migration, and induces the differentiation of motile fibroblasts into non-motile myofibroblasts, which are essential for matrix contraction and wound closure. One way in which TGF¿ may be eliciting its dual effects is through the induction of plasminogen activation inhibitor (PAI-1) expression. There is a significant body of data that the opposing effects of PAI-1 are concentration dependent: low concentrations of PAI-1 induce cell proliferation and migration, whereas, high concentrations inhibit these processes. The hypothesis being tested in this proposal is that after corneal wounding, local PAI-1 concentrations are mediated by binding to Vn. Further, that low concentrations of PAI-1 result in corneal fibroblast proliferation and migration whereas high concentrations of PAI-1 induce uPA/uPAR downregulation and result in myofibroblast differentiation. The specific aims are to determine if 1) TGF¿ concentration regulates PAI-1 levels, uPA activity, and myofibroblast differentiation. 2) Vn mediates the effects of TGF¿ and PAI-1 on uPA activity, cell migration, and myofibroblast differentiation. 3) Vn, PAI-1 and integrin expression change throughout wound healing with changing stromal phenotypes. 4) uPAR cleavage into a non-uPA binding form inhibits cell migration and induces myofibroblast differentiation. The results of these studies will lead to a better understanding of the mechanisms that guide regenerative wound repair.