Purpose: It is widely accepted that intravitreous levels of erythropoietin (Epo) are elevated in patients with ischemic retinal diseases such as proliferative diabetic retinopathy (PDR). The aim of this study was to examine the expression of Epo and the Epo receptor (EpoR) in diabetic and non-diabetic epiretinal membranes.
Methods: Eighteen epiretinal membranes (PDR (n=10), non-diabetic idiopathic epiretinal membranes (IERMs) (n=4), and inner limiting membranes (ILMs) (n=4)) were obtained during pars plana vitrectomy. Formalin-fixed and paraffin-embedded tissues were examined by immunohistochemistry with anti-Epo and EpoR antibodies.
Results: The histopathological findings demonstrated that PDR membranes consisted of a variety of endothelial cells forming a microvascular cavity with red blood cells and non-vascular stromal mononuclear cells. Membranous and cytoplasmic immunoreactivity for EpoR was strongly detected in endothelial cells and stromal cells in all PDR subjects. Although microvessels were not observed in IERMs and ILMs, immunoreactivity for EpoR was noted in the cellular component of IERMs, and was weakly detected in ILMs. Epo was not expressed in any membranes.
Conclusion: EpoR was strongly expressed in microvessels of all PDR membranes. The in vivo evidence in this study suggests that Epo in the vitreous binds to EpoR in PDR membranes, which subsequently leads to the proliferation of new retinal vessels. EpoR immunoreactivity in non-vascular stromal cells in PDR membranes, and IERMs and ILMs might be indirectly correlated with ischemia.
- epiretinal membrane
- erythropoietin receptor
- proliferative diabetic retinopathy