Cytokeratins and retinal epithelial cell behaviour.

The expression of cytokeratins 18 and 19 by human retinal pigment epithelial cells (HRPE) has been suspected of being associated with HRPE proliferation. We have investigated the involvement of these cytokeratin subtypes in the proliferative and migratory behaviour of cultured HRPE. Cell proliferation markers (bromodeoxyuridine and proliferating cell nuclear antigen) and the cytokeratins were identified using immunohistochemical techniques. In vitro, cytokeratins 18 and 19, as detected by the monoclonal antibodies RGE 53 and K4.62, were expressed in a subset of HRPE and this subset was significantly less likely to be proliferating. Micro-chemotaxis chambers were used to study migrating cells and immunohistochemical staining for cytokeratins 18 and 19 revealed that actively migrating cells always expressed these two cytokeratins, whereas stationary cells did not label for these cytokeratin subtypes. It was apparent that cytokeratins 18 and 19 were not markers of proliferation, but were involved in the mobility of HRPE in vitro. Cytokeratins 18 and 19 may be useful indicators of simple epithelial cell migration in tissues.