Corneal opacification affects millions of people and is the second leading cause of blindness in the world. A clear need exists for the development of non-surgical strategies to prevent and treat corneal fibrosis and the subsequent development of corneal opacification. Previous and preliminary studies show that extracellular enymes including the 6-O-sulfatase Sulf-1 and matrix metalloproteinases (MMPs) including MMP-9 and MMP-12 are expressed in the cornea only upon injury, implicating their possible roles in corneal repair. These enzymes are produced by epithelial, stromal and inflammatory cells, and their roles in corneal repair c have not been well-studied. In the epithelium, MMP-9 appears to decrease re-epithelialization through its effects on the TGF pathway, while in the stroma MMP-12 has been shown to be protective against fibrosis via TGF-p in various other disease processes. In addition, MMP-12's ability to produce angiostatin more efficiently than other MMPs suggests that it might play a role in preventing corneal angiogenesis. Sulf-1 has been found to modulate the binding of growth factors and chemokines in vitro. Stimulation of various growth factors, particularly TGF-p2 and FGF, are critical to the corneal fibrotic phenotype and corneal neovascularization. Taken together, these extracellular enzymes may regulate various aspects of the repair process, both positively and negatively. In this application, we propose to investigate the roles of the extracellular enzymes MMP-9, MMP-12, and Sulf-1 in the epithelial, stromal, and inflammatory corneal response to injury.
Specific Aim 1 will determine the effects of MMP-9 or Sulf-1 activity on the epithelial cell proliferation response to injury.
Specific Aim 2 will use MMP-12 knockout mice to examine the role of MMP- 12 in fibrosis and angiogenesis during the corneal stromal response to injury.
Specific Aim 3 will examine the ability of these extracellular enzymes to recruit inflammatory cells to the cornea and will use a novel imaging technique based on spinning disk confocal microscopy to study inflammatory cell dynamics in the cornea in vivo and in real-time. Understanding the roles of extracellular enzymes in wounded corneas should further our understanding of the mechanisms important to the maintenance of corneal clarity and provide basic insights that will, in the long term, allow for the development of better treatment of corneal opacification.
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