MMP9 and diabetic retinopathy: In a rat model of diabetic retinopathy, retinal levels of mRNA for MMP-2, MMP-9, and MMP-14 were increased; furthermore, exposure to MMP-2 and MMP-9 reduced tight junction function in cultures of bovine retinal endothelial cells, suggesting that these MMPs might have a role in the breakdown of the blood–retinal barrier in diabetic retinopathy120