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Aya Kodama, Koji Sugioka, Keiichi Aomatsu, Hiroshi Mishima, Yoshikazu Shimomura; Corneal Epithelial Migration In Urokinase-type Plasminogen Activator And Its Receptor Knockout Mice. Invest. Ophthalmol. Vis. Sci. 2011;52(14):285.
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Recent studies have reported that urokinase-type plasminogen activator (uPA) binds to its receptor (uPAR) and regulates proteolytic activity at various cell surfaces.In this study, we investigated the role of uPA and uPAR in corneal epithelial wound healing using both uPA knockout (KO) and uPAR KO mice.
uPA KO and uPAR KO mice and uPA and uPAR wild-type (WT) mice were used in this study. The corneal epithelial defect model was made by abrading the corneal epithelium with a blade (3mm). The areas of the epithelial defects were measured to examine the healing of epithelial defects. Using fibrin enzymography, we detected enzymatic activity of PAs from extracts in the corneas during the corneal healing process. Expressions of uPA and uPAR in the corneas were determined by immunohistological analysis. To detect the expression of uPAR in the cornea, RT-PCR and western blotting were performed using human corneal epithelial cells (HCECs) and corneal fibroblasts.
uPA KO mice had significantly delayed reepithelialization of the corneal defects, which took 72 to 96 hours, compared to uPA WT with about 24 hours for resurfacing. Whereas uPAR KO mice had the corneal wound resurfaced at the same rate as their counterpart WT mice. Histological examination revealed that uPA WT mice had their injured cornea completely resurfaced about 24 hours after wounding, whereas, KO mice needed 72 hours for reepithelialization with the weak attachment between the corneal stroma and epithelium. Immunohistochemical study showed that uPA was strongly expressed in the leading edge of the migrating epithelium, however, uPAR did not increase its expression during the healing process. Fibrin enzymography analysis revealed that uPA increased with time in the uPA WT mice during corneal wound healing. Western blotting analysis showed that uPAR was detected in corneal fibroblasts but not in HCECs. On the other hand, RT-PCR analysis detected uPAR mRNA in HCECs but no significant increase was observed during the healing process.
uPA promoted the corneal epithelial migration even in the absence of uPAR. We detected uPAR gene expression in the corneal epithelial cell, however, we could not detect uPAR expression by immunohistochemical staining or western blotting analysis. These data suggest that uPAR probably did not contribute to the corneal epithelial cell migration.
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