Avascular, hypoxic retina has been postulated to be a source of angiogenic factors that cause aberrant angiogenesis and intravitreal neovascularization (IVNV) in
retinopathy of prematurity.
Vascular endothelial growth factor (
VEGF) is an important factor involved. However,
VEGF is also required for normal
retinal vascular development, which raises concerns about inhibiting its activity to treat IVNV in
retinopathy of prematurity. Therefore, understanding the effects that
VEGF has on other factors in the development of avascular retina is important to prevent aberrant angiogenesis and IVNV. Here, we show that STAT3 was activated by increased
retinal VEGF in the rat 50/10
oxygen-induced retinopathy model. Phospho-STAT3 colocalized with
glutamine synthetase-labeled Müller cells. Inhibition of STAT3 reduced avascular retina and increased
retinal erythropoietin (Epo) expression. Epo administered exogenously also reduced avascular retina in the model. In an in vitro study,
hypoxia-induced
VEGF inhibited Epo gene expression by STAT3 activation in rat Müller cells. The mechanism by which activated STAT3 regulated Epo was by inhibition of Epo promoter activity. Together, these findings show that increased
retinal VEGF contributes to avascular retina by regulating
retinal Epo expression through
Janus kinase/STAT signaling. Our results suggest that rescuing Epo expression in the retina before the development of IVNV may promote normal developmental angiogenesis and, therefore, reduce the stimulus for later pathologic IVNV.