Abstract
Purpose::
To identify the activity of ocular tissue MMP protein(s) involved in normal canine aqueous humor outflow pathway and to compare these results to the MMP activity in dogs with glaucoma.
Methods::
16 normal canine eyes and 5 glaucomatous canine eyes were analyzed for MMP activity using substrate gel zymography. Iridocorneal angle tissue was homogenized into solution and Bradford total protein assays were determined. Substrate gelatin zymography was performed using 10 µg of sample total protein. All samples were repeated 3 times. Specific MMP gel bands were identified and measured quantitatively by densitometry technique. Statistical analysis was performed using a student t-test, multiple logistic chi-squared regression and Pearson correlations.
Results::
MMP-2 active form was found to be significantly increased in the glaucoma samples when compared to the normal tissue samples (t=2.865914, df=21, p=0.023). MMP- 9 latent form was also found to be significantly increased in glaucomatous tissue when compared to the normal eyes (t=4.050591, df=21, p=0.000375). Strong positive correlations were found between the presence of glaucoma and increasing MMP-2 active form (r=0.7804, p=0.0246) and increasing MMP-9 latent form (r=0.5170, p=0.0164). MMP-9 latent form was found to be dependent on glaucoma status (X2=4.1497, df=1, p=0.042). For every point increase in measured latent MMP-9, the odds of glaucoma occurrence increases by 1.168 (1.006, 1.355). Total protein was found to be increased significantly in the glaucoma samples (t=2.474414, df=21, p=0.0114).
Conclusions::
Iridocorneal angle tissue from glaucomatous eyes expressed a statistically significant increase in active MMP-2 and latent MMP-9 when compared to normal eyes.
Keywords: outflow: trabecular meshwork • enzymes/enzyme inhibitors • intraocular pressure