The healing process after corneal injury is initiated through the release of a number of proteins that disassemble the epithelial junctions and contribute to the movement of the epithelial sheet to cover the wounded area. Matrix metalloproteinases (MMPs), a family of proteolytic enzymes that degrade components of the cell surface and extracellular matrix, are central to this process. Barely detected in unwounded cornea, their induction is thought to play a key role during wound healing and in the establishment of chronic wounds. The production and activation of MMPs are tightly regulated by complex mechanisms that include homo-oligomerization of CD147, a heavily N-glycosylated transmembrane protein highly expressed in tumor cells. We recently discovered that CD147 is a novel cell surface counter-receptor for galectin-3, a ?alactoside-binding lectin known to cluster cell surface receptors. More importantly, we found that clustering of CD147 by galectin-3 dramatically upregulates MMP9, the primary metalloproteinase synthesized and secreted by corneal epithelial cells migrating to resurface a wound. The long-term objective of this proposal is to determine whether induction of CD147 clustering by galectin-3 is a powerful regulatory mechanism of the physiological and pathological remodeling processes associated with wound repair in the cornea. The following specific aims will address this objective: (1) to investigate te role of CD147 clustering by galectin-3 as modulator of collective cell detachment and cell migration in corneal epithelial cells, and to determine whether degradation of the galectin-3 by MMP9 inhibits CD147 clustering, thereby constituting a negative feedback mechanism to prevent sustained corneal remodeling, (2) to investigate the role of CD147 N-glycosylation in modulating galectin-3 binding affinity, CD147 clustering, and MMP9 induction, and (3) to characterize the biological role of the CD147/galectin-3 complex in mouse models of wound healing and recurrent erosion, and determine whether inhibiting galectin-3 receptor clustering and CD147 function have a therapeutic potential during recurrent epithelial wound healing. This research will explore, for the first time, the molecular mechanism linking glycan dynamics to the biological process by which wounded tissue initiates epithelial cell detachment and migration, and will provide better insight into the pathogenesis of chronic wounds.
Clinical management of impaired or delayed re-epithelialization and associated persistent epithelial defects during corneal wound healing is a vexing problem for the ophthalmologist, particularly because current wound healing therapies are limited in efficacy. Failure of the epithelia adjacent to the denuded area to migrate properly makes the underlying cornea more susceptible to inflammation and infection. We have discovered a likely mechanism responsible for modulating re-epithelization in cornea and are evaluating its role in the development of chronic wounds.
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