Role of Urokinase Type Plasminogen Activator (u-PA) in Corneal Epithelial Migration

Abstract

SummaryThe role of plasminogen activator (PA) in the migration of comeal reepithelialization was studied. Rabbit corneal blocks were cultured, and both the extent of epithelial migration over the exposed corneal stroma and the activity of PA released into the culture media were measured. A significant, direct correlation between epithelial migration and PA activity in the medium was observed, even when the migration was stimulated by fibronectin or EGF, or was inhibited by cytochalasin B or cycloheximide. Zymography confirmed that the PA released into the culture medium was of the urokinase type (u-PA). Immunohistochemical studies showed that u-PA and plasmin(ogen) were present at the leading edge of the migrating epithelium. Studies of corneal cell cultures indicated that epithelial cells rather than endothelial cells or fibroblasts were the source of the u-PA. The addition of anti-human u-PA IgG or protease inhibitors retarded the migration of the comeal epithelium in a dose-dependent manner, indicating that u-PA activity is essential for the migration of the corneal epithelium. These findings suggest that the migration of corneal epithelial cells requires not only cell attachment to the extracellular matrix through the fibronectin but also degradation of the fibronectin by the release of cellular u-PA.

Mathematical Modeling of Capillary Formation and Development in Tumor Angiogenesis: Penetration into the Stroma

“…These factors are chosen in order to provide a measure of how responsive endothelial cells are to protease and to fibronectin. It is known that proteases promote the movement of endothelial cells, (Schleef and Birdwell, 1982;Roberts and Forrester, 1990;Morimoto et al, 1993;Gordon and DeMoss, 1999).…”

Galardin Inhibits Collagen Degradation by Rabbit Keratocytes by Inhibiting the Activation of Pro-Matrix Metalloproteinases

“…Plasmin activity was measured using the plasmin substrate S-2251 as follows (Friberger et al, 1978 ;Morimoto et al, 1993) : 100-µl aliquots of conditioned culture media were mixed in each well of a 96-well plate with 20 µl plasminogen solution [10 µg ml −" in Tris-buffer (50 m Tris, pH 7n4, with 0n01 % Triton X-100)], and incubated at 37mC with 100 µl of 0n06 m S-2251 solution. The release of p-nitroanilide was measured by reading optical density at 405 nm with a microplate reader.…”

Transforming Growth Factor Beta Induces Urokinase Receptor Expression in Cultured Retinal Pigment Epithelial Cells

“…ProuPA can be converted to active enzyme by traces of plasmin initiating the plasminogen activation cascade. We have recently demonstrated that uPA staining in cultured human RPE cells was localized to focal contact sites at the leading edges of cultured subconfluent RPE cells [12], a distribution typical of migrating cells [18]. TGF-ß is produced by most cultured cells in a latent form which can be converted to the biologically active molecule by plasmin [19].…”