Retinal pigment epithelial cells release an inhibitor of neovascularization

The possibility that controlling neovascularization will aid in the treatment of a variety of ocular disorders has prompted an extensive search for inhibitors of new blood vessel formation. Most inhibitors of neovascularization so far identified have been extracted from avascular tissues. Unfortunately, the study of these inhibitors is severely limited by the fact that only small quantities of active material can be extracted from these sources. It has been suggested that diabetic intraocular neovascularization is less likely to occur in eyes with chorioretinal scars. This has led to the widespread use of photocoagulation to induce chorioretinal scar formation. The production of these scars often results in the rapid regression of intraocular neovascularization in eyes with proliferative diabetic retinopathy. Regression occurs even when photocoagulation and resultant chorioretinal scarring take place in areas remote from the new blood vessels. Retinal pigment epithelial (RPE) cells are one component of these scars. We report herein our findings that human RPE cells in culture release a substance (or substances) that causes the regression of new blood vessels on the chick embryonic yolk sac.