Corneal neovascularization (NV) is a major cause of blindness worldwide. Our research objective is to identify the role of membrane type 1 matrix metalloproteinase (MT1-MMP) activity and its proteolytic functions in corneal NV. Our laboratory has found that per cellular MT1-MMP activates proMMP-2, degrades collagen, and results in vascular endothelial growth factor (VEGF) upregulation in corneal stromal fibroblasts. We also have demonstrated that fibroblast growth factor-2 (FGF-2) upregulates MT1-MMP and that MT1-MMP and FGF-2 have a synergistic effect on VEGF upregulation in stromal fibroblasts. We performed additional experiments showing that exosomes derived from cultured stromal fibroblasts are rich in active MT1-MMP. We hypothesize that FGF-2 upregulation of MT1-MMP in stromal fibroblasts results in membrane-associated activity localized at the leading edge of migrating stromal fibroblasts. We further hypothesize that stromal fibroblast-associated active MT1-MMP promotes corneal neovascularization through two potential mechanisms: (i) upregulation of VEGF by synergistic activity with FGF-2/FGFR1 and (ii) breakdown of the extracellular matrix by stromal fibroblast-tethered or exosome-tethered MT1-MMP. The proposed research will test various aspects of our hypotheses: Aim A) determine the spatio-temporal localization of MT1-MMP enzymatic activity in vivo and in response to FGF-2/FGFR1 activation; Aim B) determine the necessity of MT1- MMP enzymatic activity on MT1-MMP-induced upregulation of VEGF in stromal fibroblasts; and, Aim C) examine the enzymatic activity of stromal fibroblast membrane- and exosome-associated MT1-MMP on collagen degradation and angiogenesis. Characterization of the spatial and temporal relationships of MT1- MMP activity in corneal angiogenesis and evaluation of the two proposed mechanisms of corneal NV will be valuable for identifying potential targets for therapeutic intervention in the treatment of corneal NV. PUBLIC HEALTH RELEVANCE: MT1-MMP enzymatic activity plays an important role in corneal revascularization. Transcriptional up regulation of VEGF and pericellular/transcellular ECM degradation may be two distinct mechanisms by which enzymatically active MT1-MMP promotes angiogenesis.