EPO enhanced in vitro human EBI formation. (A) Surface expression of CD163, CD169 and EPOR expression on cord blood CD34⁺ cell-derived macrophages. (B) Western blot analysis showing phosphorylation of STAT5 and AKT in CD34⁺ cell-derived macrophages upon EPO stimulation. (C) Representative images of EBIs formed between erythroblasts and untreated macrophages or macrophages pretreated with EPO. (D) Quantitative analyses of the EBIs showing enhancement of EBI formation by EPO pretreatment of the macrophages. *P < .05, ***P < .001. N = 3.