Effect of Exercise on Circulating Endothelial Progenitor Cells in Microvascular Angina

Background: Circulating endothelial progenitor cells (EPCs) might limit endothelial dysfunction in patients with microvascular angina (MVA). Endothelial colony-forming cells (ECFCs; displaying the CD34+/KDR+/CD45- phenotype) are currently regarded as true EPCs. The aim of this study was to evaluate exercise-induced ECFC mobilization and platelet reactivity in patients with MVA or with obstructive coronary artery disease (CAD). Methods and Results: Exercise stress test (EST) was performed in 20 MVA patients, 20 CAD patients and 20 controls. Platelet reactivity was assessed before and after EST as formation of monocyte-platelet aggregates (MPAs) and CD41 platelet expression, without and with adenosine diphosphate (ADP) stimulation. ECFC number was measured before and 24 h after EST. At rest, MPAs and CD41 platelet expression increased more with ADP in MVA patients (+71 +/- 11.0% and +37 +/- 7.5%, respectively), than in CAD patients (+37 +/- 8.6% and +19 +/- 4.5%, respectively) and controls (+29 +/- 3.5% and +21 +/- 3.1%, respectively; P<0.001 for both). At rest, ECFCs tended to be lower in CAD patients, compared to MVA patients and controls (4.1 +/- 5.0%, 7.2 +/- 6.0% and 7.3 +/- 7.0% cells/10(5), respectively; P=0.056). After EST, ECFCs increased less in MVA patients (+2.8 +/- 11) compared to CAD patients (+3.3 +/- 15; P<0.05) and controls (+7.4 +/- 24; P<0.01). Conclusions: In MVA patients, EST is able to blunt the peculiar increase of platelet reactivity to ADP present at rest; in contrast, no potential protective response of ECFCs to exercise was seen in these patients.