Tatsuya Onguchi

MT1-MMP-Mediated Cleavage of Decorin in Corneal Angiogenesis

Background/Aims: Decorin has been shown to have antiangiogenic properties. In this study, we evaluate the involvement of membrane type 1-matrix metalloproteinase (MT1-MMP), a proangiogenic enzyme, in decorin cleavage in the cornea. Methods: MT1-MMP expression was confirmed immunohistochemically in keratocytes and immortalized corneal fibroblast cell lines. Corneal micropockets of bFGF were used to assess the expression of decorin and MT1-MMP. Western blotting was used to evaluate decorin degradation by MT1-MMP. Aortic ring tube formation assays were used to assay the inhibitory effect of decorin and stimulatory effect of MT1-MMP on vascular endothelial cells in vitro. Results: We show that MT1-MMP expression is upregulated following bFGF pellet implantation in the cornea in vivo, and that MT1-MMP cleaves decorin in a time- and concentration-dependent manner in vitro. Furthermore, the addition of MT1-MMP reduces the inhibitory effects of decorin on aortic ring tube formation in vitro. Cleavage of decorin by MT1-MMP-deficient corneal cell lysates is diminished relative to that by wild-type corneal cell lysates, and an MT1-MMP knockin restores decorin processing in vitro. Conclusion: The proangiogenic role of MT1-MMP in the cornea may be mediated, in part, by facilitated cleavage of corneal decorin.

Membrane Type-1 Matrix Metalloproteinase Potentiates Basic Fibroblast Growth Factor-Induced Corneal Neovascularization

Corneal neovascularization is one of the leading causes of blindness. The aim of this study was to evaluate the pro-angiogenic role of corneal fibroblast-derived membrane type-1 matrix metalloproteinase (MT1-MMP) on basic fibroblast growth factor (bFGF)-induced corneal neovascularization in vivo and in vitro. Immunohistochemical studies demonstrated that MT1-MMP was expressed in keratocytes and immortalized corneal fibroblast cell lines. Vascular endothelial growth factor protein levels were increased after bFGF-stimulation of wild-type fibroblast cells compared with MT1-MMP knockout fibroblast cells. Corneal vascularization was significantly increased after a combination of bFGF pellet implantation and naked MT1-MMP DNA injection in wild-type mouse corneas compared with either bFGF pellet implantation or naked MT1-MMP DNA-injected corneas. Western blotting analysis of the phosphorylation levels of the key signaling molecules (p38, JNK, and ERK) demonstrated that phosphorylation levels of both p38 and JNK were diminished after bFGF stimulation of MT1-MMP knockout cells compared with wild-type and MT1-MMP knockin cells. These results suggest that MT1-MMP potentiates bFGF-induced corneal neovascularization, likely by modulating the bFGF signal transduction pathway.

MT1-MMP cleavage of the antiangiogenic proteoglycan decorin: role in corneal angiogenesis.

PURPOSE Decorin is a small chondroitin sulfate proteoglycan that inhibits vascular endothelial cell migration and tube formation. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been shown to be an important angiogenic enzyme in the cornea. We evaluated the specific role of MT1-MMP in decorin cleavage in the cornea. METHODS Western blotting was used to evaluate decorin degradation by MT1-MMP. Aortic ring tube formation assays were used to assay the inhibitory effect of decorin and the stimulatory effect of MT1-MMP on vascular endothelial cells in vitro. Corneal micropocket assays using basic fibroblast growth factor (bFGF) were used to assess changes in the levels of decorin and MT1-MMP. RESULTS MT1-MMP cleaves decorin in a time- and concentration-dependent manner in vitro. MT1-MMP levels were upregulated after in vivo bFGF pellet implantation in the cornea, and decorin cleavage products were detected in bFGF-implanted corneas but not in normal corneas. MT1-MMP reduced the inhibitory effects of decorin on aortic ring tube formation in vitro. CONCLUSION MT1-MMP may play an essential role in angiogenesis through proteolytic processing of decorin in the cornea.