Recombinant angiostatin prevents retinal neovascularization in a murine proliferative retinopathy model

Retinal neovascularization is central to the pathogenesis of proliferative diabetic retinopathy, the leading cause of blindness among the middle-aged population. Angiostatin, a proteolytic fragment of plasminogen is one of th e most promising inhibitors of angiogenesis currently in clinical trials. H ere we show that recombinant angiostatin can inhibit retinal neovasculariza tion in a mouse model of proliferative retinopathy. Because proliferative d iabetic retinopathy is a recurrent disease, effective therapy will need to be sustained. Recombinant adeno-associated Viruses permit long-term express ion of transfected genes; however they can only accommodate a small insert sequence. Thus, we engineered and tested a shortened recombinant angiostati n derivative containing a signal sequence to permit secretion. Recombinant protein was purified from the medium of transfected HEK293 cells and inject ed subcutaneously into treated animals. The retinal vasculature was analyze d in retinal flat mounts and using immunohistochemically stained sections. Both methods demonstrate that this short, secreted form of angiostatin B ef fective in reducing the development of blood vessels in a nontumor environm ent and has therapeutic potential for neovascular retinopathies such as dia betic retinopathy, retinopathy of prematurity, retinal vein occlusion and, possibly, age-related macular degeneration.