Ischemia-induced
hypoxia elicits
retinal neovascularization and is a major component of several blinding retinopathies such as
retinopathy of prematurity (ROP),
diabetic retinopathy (DR) and
retinal vein occlusion (RVO). Currently, noninvasive imaging techniques capable of detecting and monitoring
retinal hypoxia in living systems do not exist. Such techniques would greatly clarify the role of
hypoxia in experimental and human
retinal neovascular pathogenesis. In this study, we developed and characterized HYPOX-4, a fluorescence-imaging probe capable of detecting
retinal-
hypoxia in living animals. HYPOX-4 dependent in vivo and ex vivo imaging of
hypoxia was tested in a mouse model of
oxygen-induced retinopathy (OIR). Predicted patterns of
retinal hypoxia were imaged by HYPOX-4 dependent fluorescence activity in this animal model. In
retinal cells and mouse
retinal tissue,
pimonidazole-adduct immunostaining confirmed the
hypoxia selectivity of HYPOX-4. HYPOX-4 had no effect on
retinal cell proliferation as indicated by
BrdU assay and exhibited no acute toxicity in
retinal tissue as indicated by TUNEL assay and electroretinography (ERG) analysis. Therefore, HYPOX-4 could potentially serve as the basis for in vivo fluorescence-based
hypoxia-imaging techniques, providing a tool for investigators to understand the pathogenesis of ischemic retinopathies and for physicians to address unmet clinical needs.