ABSTRACT
PURPOSE: Because retinal pigment epithelial cells in epiretinal membranes remodel and contract their surrounding extracellular matrix, investigations were performed to determine if these cells can produce matrix metalloproteinases and contract collagen gels in vitro in the presence of serum or cytokines. METHODS: Cells were grown on collagen gels and their production of metalloproteinases was measured using zymography. RESULTS: Cells grown in a three-dimensional collagen gel culture system produce several latent metalloproteinases that are secreted into the gel and the surrounding medium. These include molecules of 49, 56, 66, and 100 kD. In addition, an enzyme that is probably the active form of the 66 kD enzyme is present. When interleukin 1 beta is added to the cultures, latent 49 kD and 100 kD gelatinase production is greatly stimulated and an active form of both enzymes is also observed in the medium. In contrast, transforming growth factor beta has no stimulatory effect. The cells contract the collagen gel but this is small without cytokines; however, contraction is greatly enhanced in the presence of serum or interleukin 1 beta plus transforming growth factor beta. Contraction is unlikely to be the result of metalloproteinase action on the underlying extracellular matrix because complete inhibition of these enzymes has little effect. CONCLUSIONS: These results show that cytokines can cause cultured retinal pigment epithelial cells to produce metalloproteinases that can, when activated, degrade most collagens and other structural molecules in extracellular matrix. In addition, they can stimulate the contraction of extracellular matrix constituents but there is not a simple causal relationship between matrix remodeling and contraction.