Elevated endothelial progenitor cells during painful sickle cell crisis

ObjectiveCirculating endothelial progenitor cells (EPCs) counts were determined in patients with sickle cell disease (SCD) to elucidate their role in SCD-related ischemia-induced angiogenesis and reendothelialization.Materials and MethodsCirculating EPC counts (KDR+/CD34+/Cd45dim cells) and their relation to serum levels of EPC mobilizing growth factors erythropoietin, vascular endothelial growth factor, and interleukin-8 were investigated in SCD patients during asymptomatic state (n = 66) and painful crisis (n = 36) and compared to healthy controls (n = 13).ResultsEPC counts were comparable between controls (0; range, 0–1.1 cells/mL) and patients (0; range, 0–0 cells/mL) in asymptomatic state, but were significantly higher during painful crisis (41.7; range, 0–186 cells/mL; p < 0.05). Also in a paired analysis of 12 patients who were included both during asymptomatic state and painful crisis, EPC counts increased significantly during painful crisis (from 0 [range, 0–0] to 26 [range, 0–149 cell/mL; p < 0.05). EPC counts were not related to any of the measured growth factors.ConclusionThe higher EPC counts during painful crisis might indicate a role for EPC mobilization in reendothelialization. As a relationship of EPCs with the established mobilizing growth factors, measured in this study was not observed, the mechanism of EPC mobilization in SCD remains to be elucidated.