Bovine Retinal Pigment Epithelium Promotes Proliferation of Choroidal Endothelium In Vitro

The invasion of Bruch's membrane and subsequently the subpigment epithelium and subretinal spaces by proliferating choroidal capillaries is a prominent feature of age-related macular degeneration. The ability to isolate and propagate pure cultures of bovine choroidal microvascular endothelium, choroidal pericytes, turbinate fibroblasts, and bovine retinal pigment epithelium allowed us to identify a growth-promoting activity produced by the retinal pigment epithelium that stimulated the proliferation of these cells in vitro. This mitogenic activity is present in both retinal pigment epithelium-conditioned medium and retinal pigment epithelium extract and enhances the mitogenic activity of retinal-derived extract. The activity is resistant to extremes of temperature and pH but partially sensitive to trypsin inactivation.