Cell proliferation in response to vitreous hemoglobin

Rabbits were examined at intervals to 90 days after receiving two or three intravitreal injections, on consecutive days, of homologous hemoglobin or saline. Cell proliferation in the vitreous was assessed by scintillation counting and radioautography after intravitreal administration of 3H-thymidine 4 hr prior to sacrifice. Two populations of vitreous cells phagocytize the vitreous hemoglobin and are stimulated to DNA synthesis. Cells that migrate into the vitreous in response to hemoglobin also contribute to total 3H-thymidine uptake. Tritiated thymidine incorporation peaks between 5 to 10 days and again between 22 to 30 days after the first administration of hemoglobin. By 45 to 60 days after two injections and 90 days after three injections the vitreous cell proliferative activity has returned to normal. It is concluded that a bleeding event which leads to the release of hemoglobin in the vitreous stimulates a minor, transient vitreous cell proliferation and a more significant, but also transient, migration of cells into the vitreous. Aside from contributing by phagocytosis to vitreal clearing, no other functions have been ascribed to these cells.