Vitreous macrophage elicitation: generation of stimulants for pigment epithelium in vitro.

Vitreous and macrophage samples were tested for the ability to stimulate proliferation and cell migration in cultured rabbit retinal pigment epithelium (RPE). A macrophage invasion was elicited by the intravitreal injection of latex particles in rabbits and after 3 days the vitreal macrophages were collected. The macrophages themselves, macrophage-conditioned culture medium, and macrophage-incubated vitreous had modest effects on RPE proliferation, but significantly stimulated RPE migration. A portion of the migration activity may be due to macrophage-derived proteases acting on normal vitreous. Mitogenic and additional migration-stimulating activity may also arise from adjacent tissues or from a breakdown of the blood-vitreous barrier that accompanies a macrophage invasion. A macrophage ingress into the vitreous may provide part of the stimulation for the migration and proliferation of RPE in conditions such as proliferative vitreoretinopathy.