Background: There is evidence that endothelial progenitor cells (EPCs) are mobilized into the circulation after coronary artery bypass grafting (CABG) with cardiopulmonary bypass. However, there is little known about EPC mobilization after off-pump CABG or valve surgery. We aimed to establish the response of EPCs to various forms of cardiac surgery and examine the role of well-known mobilizing cytokines on EPC levels.
Methods: One hundred and ten patients were studied: 54 elective CABG (30 on-pump, 24 off-pump); 23 urgent CABG; and 33 non-CABG. The EPC functional status was assessed using the colony forming unit assay (EPC-CFU) and plasma levels of granulocyte colony-stimulating factor (G-CSF), stromal cell-derived factor 1-alpha, matrix metalloproteinase, and vascular endothelial growth factor were assessed by enzyme-linked immunosorbent assay. Samples were taken preoperatively and on days 1 and 5 after surgery.
Results: Patients requiring urgent CABG and non-CABG patients had significantly higher numbers of EPC-CFU prior to surgery than elective CABG patients. All elective patients showed a significant increase in postoperative EPC-CFU levels: on-pump CABG 10.4 +/- 3.8 to 53.9 +/- 11.9, p = 0.001; off-pump CABG 9.5 +/- 3.5 to 65.7 +/- 17.3, p = 0.006; non-CABG 23.5 +/- 6.8 to 84.6 +/- 27.2, p = 0.05. The postoperative EPC rise in elective patients correlated with plasma G-CSF levels (r = 0.387, p < 0.01). Urgent patients demonstrated a significant increase in G-CSF levels but this was not associated with an increase in EPC-CFU level.
Conclusions: Patients undergoing elective cardiac surgery demonstrated an increase in EPC-CFU postoperatively, which correlated with increased plasma G-CSF level. Urgent patients did not have an increase in EPC-CFU despite a plasma G-CSF rise. Endogenously mobilized EPCs present a potential therapeutic target.