Immunohistochemical insights into sickle cell retinopathy

Dynamic vaso-occlusive and vaso-proliferative events occur in sickle cell retinopathy. Using streptavidin peroxidase immuno-histochemistry, we investigated changes in distribution and relative levels of components in the fibrinolytic system and growth factors in retina and choroid from 2 sickle cell patients: a 20 month old SS patient and a 54 year old SC patient. Antigen localization in the sickle cell patients was compared to localization from 2 non-sickle cell, non-diabetic control subjects. In chorioretinal pigmented lesions of the SC patient, bFGF and TGF-β1, β2, and β3 immunoreactivity was present within migrating retinal pigment epithelial (RPE) cells. Our interpretation of the data presented in this case study is that fibrin deposition within retinal and choroidal vessels of sickle cell subjects may occur due to elevated PAI-1 activity. Moreover, vaso-occlusions of choroidal vessels may influence the expression of growth factors in choriocapillaris endothelium, which could stimulate formation of choroidal neovascularization. Finally, fibrosis and gliosis in and near chorioretinal pigmented lesions may be stimulated by RPE production of bFGF and TGF-β's.