Modulation of Angiogenesis in vitro and in vivo in Ischaemic Retinopathy by Dynepo

Abstract

Purpose: : Erythropoietin (EPO) regulates angiogenesis and manufactured EPO analogues (epoetins) may have beneficial properties for microvascular re-modelling following ischaemic injury. In the context of the retina, ischaemia leads to inappropriate neovascularisation and sight-threatening retinopathy. In the current study, we have evaluated the angiogenic activity of human cell-derived epoetin delta (Dynepo) in vitro and also how this analogue regulates various pathogenic end-points in a murine model of ischaemic retinopathy.

Methods: : The angiogenic potential of epoetin delta (concentration range 0.1-100IU/ml) was investigated in vitro using human microvascular endothelial cells. The murine model of oxygen induced retinopathy (OIR) displays central retina ischaemia which drives pre-retinal neovascularisation. Mice received 30-2500IU/Kg of epoetin delta or vehicle control buffer i.p. for 5 concurrent days. On day 5 VEGF and EPO mRNA expression and microglial activation were quantified and the retinal microvascular profile assessed. CD133 and SCA-1 was also assessed in the bone marrow by flow cytometry.

Results: : Epoetin delta caused a significant reduction in in-vitro angiogenic activity when compared to controls (p<0.001) (0.1-1IU/ml) while at higher non pharmacological concentrations (>20IU/ml) there was a significant increase in angiogenesis (p<0.001). Epoetin delta-treatment of mice subjected to OIR induced a significant increase in retinal VEGF (p<0.001) and EPO-R mRNA expression (p<0.05) and attenuated microglial numbers and activation state in comparison to controls (p<0.05). Epoetin delta induced no increase in pre-retinal neovascularisation but induced a significant intra-retinal vessel forming response in the ischaemic regions (p<0.05). Epoetin Delta increased the hematopoetic stem cell markers CD133 and Sca-1.

Conclusions: : Epoetin delta induces a complex angiogenic response in vitro and in vivo. This human cell derived epoetin delta induces significant re-modelling of the ischaemic retina and this suggests a protective role in ischaemic retinopathies.

Keywords: retinal neovascularization • diabetic retinopathy • hypoxia