Downregulation of matrix metalloproteinase-2 in corneal fibroblasts by interleukin-1 receptor antagonist released from corneal epithelial cells.

PURPOSE The authors previously showed that the expression of various junctional proteins in corneal epithelial cells or corneal fibroblasts (CFs) is regulated by the presence of the other cell type in a coculture system. In this study, the effect of corneal epithelial cells on the expression of matrix metalloproteinases (MMPs) in CFs was studied. METHODS Human CFs and simian virus 40-transformed human corneal epithelial (HCE) cells were cultured on opposite sides of a collagen vitrigel membrane. Expression of MMPs in CFs was examined by reverse transcription-polymerase chain reaction and immunoblot analyses. RESULTS The amounts of MMP-2 mRNA and protein in CFs were decreased by the presence of HCE cells. HCE cells had no effect on the expression of MMP-1 in CFs. HCE cells released interleukin (IL)-1 receptor antagonist (IL-1RA) into the culture medium, and depletion of IL-1RA in HCE cells by RNA interference largely abolished the effect of these cells on MMP-2 expression in CFs. The downregulation of MMP-2 expression in CFs by HCE cells was blocked by an inhibitor of signaling by the mitogen-activated protein kinase (MAPK) ERK (PD98059) but was not affected by those of signaling by the MAPKs p38 (SB203580) or JNK (SP600125). CONCLUSIONS Corneal epithelial cells downregulated expression of MMP-2 in CFs in a manner dependent at least in part on the release of IL-1RA from the former cells. This effect might contribute to the attenuation of corneal stromal remodeling by corneal epithelial cells.