Matrix Metalloproteinases in Retinal Capillary Cells

Abstract

Abstract: : Purpose: Matrix metalloproteinases (MMPs) are critical in regulating homeostasis of extracellular matrix. However, their in cytokine induced vascular permeability in retinal capillary cells is not clear. We proposed: 1.That cultured retinal cells produce specific MMPs in concentrations that differ according to cell type and environment. 2.That the interaction of specific MMPs and (TIMPS) with inflammatory cytokines contributes to the regulation of the blood retinal barrier. Method: Second passage retinal microvascular cells were grown to confluence on coated polycarbonate filters for permeability studies. The monolayer was grown until tight junctions formed and then cells were exposed to combinations of cytokines and and TIMPs. Paracellular and transcellular permeability was assayed by use of radiolabelled inulin and albumin respectively. The procedure was repeated using medium containing 30 mM glucose. Zymography was carried out on conditioned media from cells exposed to cytokines and or TIMPs with PMA as a positive control for MMP activation and EDTA (an MMP inhibitor) as a negative control. Results: Human and bovine retinal endothelial cells and pericytes produced MMP-2 and MMP-9. Human pericytes also produced MMP-3. However the amount as well as the type of MMP varied according to the passage. The addition of cytokines TNFa and IL1b resulted in moderate activation of MMP-2 and stimulated the production of MMP-9 whereas TIMP 2 reduced activation in both endothelial cells and pericytes. Similarly TIMP 2 and TIMP 1 attenuate the increased permeability of cell monolayers induced by TNFa and IL1. TIMP 2 had a stronger effect than TIMP 1. However when TIMP 1 and TIMP 2 are used together, the effect is not summative. Exposure to 30mM glucose potentiated the hyperpermeability seen in cytokine-activated cells and changed the MMP profile observed in zymography. Conclusion: These data suggest that the human and bovine retinal microvascular cells produce MMP-2 and MMP-9 and that early passage human retinal endothelial cells and pericytes also produce MMP-3. That the MMP/TIMP axis plays a regulatory role in the permeability of the capillary blood retinal barrier, which may be disrupted in a high glucose environment.

Keywords: 388 diabetic retinopathy • 560 retinal culture • 399 enzymes/enzyme inhibitors