Abstract
Purpose: :
Penetrating ocular needle injury (POI) induces angiostatic activity in the vitreous humor and alters the retinal and vitreous humor levels of several proteins known to regulate angiogenesis. Previous studies suggest that matrix metalloproteinases (MMP) facilitate neovascularization by remodeling retinal tissue to allow extension of neovascular structures from the retinal plane into the vitreous cavity. The purpose of this study was to investigate biochemical assays of MMP activities in the presence of soluble POI and non-POI rat vitreous.
Methods: :
To generate POI, a dry 30-gauge needle was inserted twice posterior to the temporal ora of the left eyes of Sprague-Dawley rats. The right eyes served as non-POI controls. Vitreous from both eyes was harvested 24 hours after needle injury and pooled separately. MMP-1, -2, -9, -13, and -14 proteolytic activities were assayed in the presence of vehicle, 50µg/ml soluble POI or 50µg/ml non-POI vitreous protein in a biochemical assay that uses an exogenous MMP substrate tagged with a fluorescent reporter. A potent inhibitor of all these enzymes was used as a negative control. All measurements were made when the change in fluorescent units was linear with time.
Results: :
Soluble POI and non-POI vitreous protein had no effect on MMP-1 and -13 activities. The MMP-2 and -14 positive control activities were significantly different from the MMP activities in the presence of soluble POI and non-POI vitreous protein. The data suggest that soluble POI vitreous protein decreases MMP-2 and -9 activity when compared with non-POI vitreous protein.
Conclusions: :
Soluble vitreous protein from both POI and non-POI eyes showed inhibition in MMP-2 and -14 activities. Vitreous protein from needle-injured eyes showed a decrease in MMP-2 and -9 activity, relative to that from non-injured eyes. Complimentary studies will be designed to further assess effect of needle injury on MMP activity.
Keywords: wound healing • proteolysis • retinal neovascularization