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Purpose. To evaluate the effects of adenosine and related substances on events that occur during vasculogenesis and angiogenesis, using in vitro assays.Methods. Adenosine (ADO), inosine (INO, an adenosine catabolite), and 5′-(N-ethylcarboxamido) adenosine (NECA, an adenosine agonist) were evaluated for their effect on the proliferation of canine retinal microvascular endothelial cells (DRME), using a cell count assay. Also, these substances and ADO receptor selective agonists and antagonists were evaluated in an assay for DRME chemokinesis by measuring random migration into a wound made in a confluent cellular monolayer. Finally, the effects of these substances on DRME cord formation were evaluated in a 3-dimensional collagen gel. Bovine retinal extract (RE) was used as a positive control for all assays.Results. There was no effect on proliferation of DRME by any of the substances related to adenosine, but VEGF yielded a 30% stimulation of proliferation. Retinal extract, 10 μM ADO and 1.2 nM VEGF stimulat...

To determine if vascular occlusion and nonperfusion is associated with the outer retinal atrophy, retinopathy, and choroidopathy (chorioretinopathy) that occurs in the alpha H beta S[beta MDD] and alpha H beta S [alpha MD beta MDD] transgenic mouse models of sickle cell disease.Mice from the alpha H beta S[beta MDD] and alpha H beta S[alpha MD beta MDD] transgenic mouse lines that express high levels of human beta S globin were anesthetized and administered horseradish peroxidase (HRP) intracardially. After 1 min, the animals were sacrificed, and the retina from one eye was excised, fixed, and developed in diaminobenzidine (DAB). The contralateral eye was fixed, embedded whole in glycol methacrylate, and HRP developed in 2.5 microns sections.HRP reaction product (HRP-RP) and stained erythrocytes (RBCs) (due to endogenous peroxidase) were diffusely distributed within all vascular lumens in flatmount retinas from control animals (littermates homozygous for the mouse Beta Major deletion not expressing the beta S transgene). In 42.5% of the transgenic mice expressing beta S without any proliferative retinopathy, many blood vessels contained RBC plugs and lacked lumenal HRP-RP. In addition to packed RBCs, fibrin was sometimes present at sites of occlusion. In sections from whole eyes of the same animals, foci of photoreceptor degeneration were associated with areas of choriocapillaris nonperfusion (lumen that lacked HRP-PR). In areas with normal photoreceptors, the choriocapillaris appeared perfused (HRP-RP was present). In animals with proliferative chorioretinopathy, some neovascular formations lacked luminal HRP-RP, suggesting autoinfarction.Nonperfused retinal and choroidal vessels were observed in mice from the alpha H beta S[beta MDD] and alpha H beta S[alpha MD beta MDD] lines without retinal and choroidal neovascularization, whereas, all mice with neovascularization had nonperfused areas. Furthermore, small foci of PR loss were associated with areas of nonperfused choriocapillaris. These results suggest that sickle cell-mediated vaso-occlusions are an initial event in the chorioretinopathy and outer retinal atrophy that occurs in these models.