Hypoxia enhances the tissue protective effect of erythropoietin and its analogues in an endothelial cell injury model

PO has tissue protective activities in ischemic disease but also has prothrombotic, erythropoietic effects. Carbamylated EPO (CEPO) retains the protective actions without the erythropoietic effects. To assess the potential of these molecules in atherosclerosis (an ischemic heart disease), we investigated EPO and CEPO in an in vitro model of injury using bovine aortic endothelial cells (BAEC) in hypoxia and normoxia.. BAECs were grown to confluence in 10% FBS in 12 well culture plates. They were then cultured under normoxia (21% oxygen) or hypoxia (5% oxygen) 24 h prior to their use in an injury model using the ‘scratch assay.’ The effects of EPO and CEPO on endothelial closure were assessed using a range of concentrations (0-10 ng/mL). In separate experiments, the effects of EPO and CEPO on BAEC proliferation and chemotaxis were also assessed under similar hypoxic conditions. Gene expression of the receptors that may be involved in their protective pathway [EPOR and the ß common chain receptor (ßCR)] were assessed using quantitative PCR. The effects of both EPO and CEPO were enhanced under hypoxic conditions (13 ± 2.6 %, and 10 ± 1.69 %, p< 0.01 improvement in the degree of endothelial cell closure after treatment with EPO and CEPO respectively) compared to normoxic conditions (3.2 ± 0.9%, p>0.05). Whilst, the expression of EPOR gene increased by 2.1 ± 0.8 folds (p<0.05) In hypoxia, ßCR expression was not affected by the change in oxygen tension. The effects of EPO and CEPO in the scratch assay appeared to be mediated by enhancing cell proliferation and migration of BAECs (p<0.05). In conclusion, the enhanced effects of EPO and CEPO on endothelial cells under hypoxia requires further investigation in processes in which hypoxia may play a role, e.gfor example. in atherogenesis and re-stensosis following angioplasty.