Analysis of the secretion pattern of monocyte chemotactic protein-1 (MCP-1) and transforming growth factor-beta 2 (TGF-beta 2) by human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells, situated between the neurosensory r etina and the vascularized choroid, form part of the blood-eye barrier and are important for homeostasis of the outer retina. These cells are able to produce a variety of cytokines which may play a role in the maintenance of the immunosuppressive milieu inside the eye and in intraocular inflammatory responses. In the present study, we investigated whether RPE cells secrete d the anti-inflammatory cytokine TGF-beta 2 acid the proinflammatory cytoki ne MCP-1 in a polarized manner. Monolayers of human donor RPE cells were cu ltured on transwell filters. Secretion of TGF-beta 2 and MCP-1 at either th e apical or basal side of the RPE cell monolayers, that were not treated or stimulated with IL-1 beta (200 U/ml), was analysed by ELISA. All three cel l lines examined had a different TGF-beta 2 secretion pattern. In two of th e three donor RPE cell lines tested, TGF-beta 2 secretion was polarized, bu t not in the same direction. TGF-beta 2 secretion was not up-regulated by s timulation with IL-1 beta. In contrast, IL-1 beta strongly induced MCP-I se cretion preferentially into the basal compartment of all RPE monolayers tes ted. These data indicate that human RPE cells are able to secrete TGF-beta 2 and MCP-1 in a polarized fashion. Our results suggest that MCP-I can be s ecreted by RPE cells in the direction of choroidal vessels during inflammat ory responses in the posterior part of the eye, which may limit damage to t he neurosensory retina.