Angiostatin and integrin αvβ3 in the feline, bovine, canine, equine, porcine and murine retina and cornea

Angiogenesis is tightly controlled in the ocular tissues of domestic animals but its mechanisms are not fully understood. This is largely because of insufficient data on the expression of molecules that impact angiogenesis. Because angiostatin and one of its receptors integrin αvβ3 inhibit and promote angiogenesis, respectively, we hypothesized that the normal retina and cornea of domestic animals would express angiostatin but not integrin αvβ3. Normal eyes of the cat, cow, dog, horse, pig and rat were evaluated for angiostatin and integrin αvβ3 by light and electron immunocytochemistry and estern blots. Angiostatin was detected in the corneal epithelium of the cat, dog, horse, pig and rat, but was not found in cow corneal epithelium. Angiostatin was localized in the nerve fiber layer, ganglion cell layer, inner and outer plexiform layers, and the photoreceptor layer of the cat, cow, dog and rat. Horse and pig retinas showed additional staining in the matrix of the inner nuclear layer. Immunogold electron microscopy further confirmed angiostatin in cat retina. Western blots showed angiostatin in corneal and retinal homogenates. Integrin αvβ3 was absent in cornea and retina of all the species studied. These data show that angiostatin, an inhibitor of angiogenesis, is present while integrin αvβ3, which promotes angiogenesis, is absent in normal cornea and retina of the domestic animals in this study with the exception being angiostatin absence in cow corneal epithelium. Therefore, angiostatin may contribute to the anti-angiogenic environment in the normal domestic animal eye while its absence in the cow may contribute to greater propensity for corneal vascularization. Because integrin αvβ3 is one of the receptors for angiostatin, its absence may prevent angiostatin from killing normal retinal and corneal cells.