Expression of stromal-cell-derived factor-1 on circulating platelets is increased in patients with acute coronary syndrome and correlates with the number of CD34+ progenitor cells. 
Previous experimental studies have suggested that platelet stromal-cell-derived factor-1 (SDF-1) regulates mobilization and recruitment of haematopoietic progenitor cells supporting revascularization in mice.  However, there are no clinical data available regarding platelet-bound SDF-1 in patients with acute coronary syndrome (ACS).  The objective of this study was to evaluate the platelet-surface expression of SDF-1 in patients with ACS.  Patients with ACS (n = 418) showed a significantly enhanced SDF-1 expression on admission compared with those with stable angina pectoris (SAP, n = 486) [SAP (mean fluorescence intensity (MFI) +/- SD): 13.48 +/- 5.27; ACS: 18.45 +/- 12.85; P < 0.001) independent of cardiovascular risk factors and medication.  Enhanced platelet-bound SDF-1 expression was found in patients with reduced left ventricular ejection fraction (LVEF <55%) in comparison to patients with normal LVEF (P = 0.005).  Platelet-bound SDF-1 expression positively correlated with the degree of platelet activation [CD62P: r = 0.325; glycoprotein VI (GPVI): r = 0.277; PAC-1: r = 0.501; P < 0.001 for all] and showed a significant, but slight association with plasma levels of SDF-1 (r = 0.084; P = 0.045).  In a subgroup of patients with coronary artery disease, platelet-bound SDF-1, but not other platelet activation markers, significantly correlated with the number of circulating CD34(+) progenitor cells (r = 0.252; P = 0.002) or CD34(+)/CD133(+) endothelial progenitor cells (r = 0.352; P = 0.008).  Platelet-bound SDF-1 may play an important role in peripheral homing of circulating progenitor cells thus in tissue regeneration.