Matrix metalloproteinase 2, matrix metalloproteinase 9, and connective tissue growth factor in the equine tear fluid: Possible implications in corneal wound healing

The goals of this study were to investigate the presence of matrix metalloproteinase 2 (MMP-2), matrix metalloproteinase 9 (MMP-9), and connective tissue growth factor (CTGF) in the equine tear film, cornea, and lacrimal glands; to compare the levels of MMP-2, MMP-9, and CTGF in the tear fluid of horses with healthy eyes and horses with ulcerative keratitis; to document the changes in MMP-2 and MMP-9 levels in horse tear film during corneal healing; and to investigate the in vitro effects of various proteinase inhibitors on the activity of MMP-2 and MMP-9 isolated from the equine tear film.; This study demonstrates by immunohistochemistry the expression of MMP-2 protein in the equine lacrimal gland and the gland of the nictitating membrane. The expression of MMP-2 and MMP-9 proteins was also found in the healthy cornea of the horse and was increased in the ulcerated equine cornea.; In this study, the level of MMP-2 and MMP-9 activity was determined in a total 330 tear fluid samples by the use of gelatin zymography. MMP proteolytic activity was detected in all tear samples and was significantly increased in the tear fluid of horses with ulcerative keratitis (1.92 +/- 1.06 RSU) compared to normal (0.62 +/- 0.47 RSU). Based on the collection and analysis of a total of 124 serial tear fluid samples in 10 horses with ulcerative keratitis, we documented for the first time that total MMP activity decreases in equine tears as corneal epithelial and stromal healing occur.; We documented, by gelatin zymography, a high amount of inhibition of equine MMP activity in vitro by the use of potassium edatate diaminetetrataacetatic acid, doxycycline, N-acetylcysteine, equine serum, ilomostat, and alpha-1-proteinase inhibitor.; The level of CTGF was determined by enzyme immunoassay in a total 64 tear fluid samples in this study and the molecule was detected in 39 of the samples. These data demonstrate that CTGF was present in the equine tear film. This study also indicates by immunohistochemistry the expression of CTGF protein in the healthy cornea, the lacrimal gland and the gland of the nictitating membrane of the horse (n = 10).