Assessing effects of mechanical stimulation of fluid shear stress on inducing matrix Metalloproteinase-9 in cultured corneal epithelial cells.

Blinking is regarded as mechanical stimulation of fluid shear stress on the corneal epithelial cells. Therefore, we evaluated whether fluid shear stress affects matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in cultured human corneal epithelial cells (HCECs). No other study has shown the influence of fluid shear stress on HCECs regarding mRNA expression and the protein levels of MMPs. Cultured HCECs were exposed to shear stress (0, 1.2, 12 dyne/cm) for 12 and 24 h with the parallel-plate type of flow chamber. Gene expression of MMPs and TIMPs was measured by real-time polymerase reaction. Concentrations of MMP-1 and MMP-9 in cell lysates were determined using bead-based amplified luminescent proximity homogenous assay-linked immunosorbent assay. The expression of MMP-9 and MMP-1 in HCECs exposed to low and high flow for 12 and 24 h, respectively, increased significantly compared with those under static conditions. The expression of MMP-9 in the cells exposed to high flow for 24 h increased significantly compared with those under static and low flow conditions. Levels of MMP-9 in cell lysates exposed to fluid flow for 24 h were elevated significantly with increasing shear stress. Fluid shear stress exerted on HCECs affected MMPs, which was associated with inflammation and pathogenesis. Mechanical stress induced by blinking might influence expression of MMPs on the ocular surface. Further studies are warranted to establish the molecular mechanism of shear stress-induced alternations of MMPs.