Effect of Cyclical Mechanical Stretch and Exogenous Transforming Growth Factor-??1 on Matrix Metalloproteinase-2 Activity in Lamina Cribrosa Cells from the Human Optic Nerve Head

Abstract

Purpose: Extensive remodeling of the lamina cribrosa extracellular matrix occurs in primary open angle glaucoma. The transforming growth factor-β (TGF-β) and matrix metalloproteinase (MMP) protein families are implicated in this process. The authors investigated (a) the effect of cyclical mechanical stretch on TGF-β1 mRNA synthesis, TGF-β1 protein secretion, MMP-2 protein activity and (b) the effect of exogenous TGF-β1 on MMP-2 protein activity in human lamina cribrosa cells in vitro. Methods: Primary human lamina cribrosa cells grown on flexible and rigid plates were exposed to cyclical stretch (1Hz, 15%) or static conditions for 12 and 24 hours. Cells grown on 100-mm plates were exposed to human TGF-β1 (10 ng/ml) or vehicle (4 mM HCl/1% BSA) for 24 hours. TGF-β1 mRNA synthesis in stretched and static cells was measured using real-time polymerase chain reaction. TGF-β1 protein secretion in stretched and static cell media was measured using enzyme linked immunosorbent assay. Gelatin zymography measured MMP-2 activity in stretched, static, TGF-β1- treated and vehicle-treated cell media. Results: Cyclical stretch induced significant increases in TGF-β1 mRNA synthesis after 12 hours (**P < 0.01) and TGF-β1 protein secretion after 24 hours (*P < 0.05). Cyclical stretch significantly (*P < 0.05) increased MMP-2 activity in cell media after 24 hours. Exogenous TGF-β1 induced a significant (**P < 0.01) increase in cell media MMP-2 activity after 24 hours. Conclusions: These results suggest that cyclical stretch and TGF-β1 modulate MMP-2 activity in human lamina cribrosa cells. TGF-β1 and MMP-2 release from lamina cribrosa cells may facilitate matrix remodeling of the optic nerve head in primary open angle glaucoma.