RESUMO
In order to understand the effect of mechanical stretch on corneal extracellular matrix remodeling, human keratoconus fibroblasts (HKCFBs) were subjected to cyclic stretch in vitro and the expression of matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases (TIMPs), and inflammatory cytokines were evaluated. HKCFBs were seeded into a flexible membrane base and subjected to a cyclic stretch regimen of 10% equibiaxial stretch at a stretching frequency of 1 Hz for 6 h using a Flexcell tension unit. An antibody directed against interleukin6 (IL6 Ab) was used to investigate the roles of IL6 on mechanical stretch mediated regulation of MMP in HKCFBs. Culture supernatants were assayed using an enzymelinked immunosorbent assay for MMP1 and 3, TIMP1 and 2, and IL6. Total RNA from the cells was extracted, and quantitative polymerase chain reaction was used to determine mRNA for MMP1 and 3, TIMP1 and 2, and IL6. In stretched cells, levels of MMP1 and 3 demonstrated an increase compared with unstretched cells, but levels of TIMP1, and 2 revealed a decrease. Mechanical stretch significantly increased the mRNA expression and protein synthesis of IL6 compared with unstretched cells. IL6 induced MMP1 and 3 expression, whereas no significant effects were observed in levels of TIMP1 and 2 compared with the untreated control groups. Additionally, the IL6 Ab markedly inhibited the stretchinduced increase in MMP1 and 3 in culture supernatants in a dosedependent manner. No significant differences in TIMP1 and 2 protein levels were detected between stretched cells treated with IL6 Ab and stretched cells without IL6 Ab treatment. These results indicate that cyclical mechanical stretch augments IL6 production and MMP expression, and reduces levels of TIMP in HKCFBs. Thus, it is suggested that IL6 mediates the stretchinduced MMP expression.