• angiogenesis;
  • apoptosis;
  • endothelial colony-forming cells;
  • endothelial progenitor cells;
  • erythropoietin;
  • ischemia

Summary.  Background:  Endothelial colony-forming cells (ECFCs) are promising candidates for cell therapy of ischemic diseases. Erythropoietin (EPO) is a cytokine that promotes angiogenesis after ischemic injury. EPO receptors (EPORs) classically include two EPOR subunits, but may also associate with the β-common chain (CD131) in a newly identified receptor involved in EPO cytoprotective effects.

Objective:  The aim was to take advantage of the proangiogenic properties of EPO to enhance ECFC graft efficiency. We postulated that priming ECFCs by adding epoietin α in culture medium prior to experiments might increase their angiogenic properties. We also explored the role of the CD131 subunit in EPO priming of ECFCs.

Methods and Results:  By western blotting on cord blood ECFC lysates, we showed that EPOR and CD131 expression increased significantly after EPO priming. These proteins coimmunoprecipitated and colocalized, suggesting that they are covalently bound in ECFCs. EPO at 5 IU mL−1 significantly stimulated proliferation, wound healing, migration and tube formation of ECFCs. EPO priming also increased ECFC resistance to H2O2-induced apoptosis and survival in vivo. Similarly, in vivo studies showed that, as compared with non-primed ECFC injection, 5 IU mL−1 EPO-primed ECFCs, injected intravenously 24 h after hindlimb ischemia in athymic nude mice, increased the ischemic/non-ischemic ratios of hindlimb blood flow and capillary density. These effects were all prevented by CD131 small interfering RNA transfection, and involved the phosphoinositide 3-kinase–Akt pathway.

Conclusion:  These results highlight the potential role of EPO-primed ECFCs for cell-based therapy in hindlimb ischemia, and underline the critical role of CD131 as an EPO coreceptor.