There are a number of eye diseases, many leading to blindness, in which ocular neovascularization plays a critical role. These include diabetic retinopathy, neovascular glaucoma, inflammatory diseases, and ocular tumors (e.g. retinoblastoma). At present, the treatment of these diseases, especially once neovascularization occurs, is often inadequate and blindness sometimes results. Thus it is conceivable that an inhibitor of neovascularization could have an important therapeutic role in relieving the course of these diseases, particularly ocular tumors. Such an inhibitor might also provide a useful tool with which to better study the etiology of these diseases. We have isolated and partially purified a vascular inhibitory factor from bovine scapular cartilage and shark cartilage. This substance caused a 70% decrease in vascular growth to V2 carcinoma in the rabbit cornea when administered locally by a polymer implant which continuously released the factor. This inhibitor has been infused (at a much higher level than with the polymer implant) regionally into mice with B16 melanoma in the conjunctiva and into rabbits carrying V2 carcinoma in the cornea. In both systems, neovascularization and tumor growth was decreased by a factor of over 40 during the period of infusion. No toxic effects to any animals were observed. We have now purified and obtained an N-terminal sequence of a cartilage derived collagenase inhibitor. Initial tests suggest this substance may be responsible for inhibition of angiogenesis. A new in vitro assay has been developed for angiogenesis inhibitors. These initial studies in our laboratory have provided the first evidence that naturally occurring inhibitors of ocular neovascularization exist and can be used to inhibit at least some forms of neovascularization in the eye. Having demonstrated this important biological activity, the specific aims of our proposed study are to: 1. Conduct studies in the genetic engineering and mammalian cell culture to provide both basic information about the inhibitor and to produce increased quantities of it. 2. Examine the mechanism of action at a biochemical, cellular, and whole animal level.
