Background: Endothelial progenitor cells (EPC) derive from bone marrow and participate in both endothelial regeneration and development of new blood vessels. EPC also play a role in the atherosclerotic process, and their number correlates negatively with the presence of classical risk factors.

Aim: To evaluate circulating EPC count and their exercise-induced mobilisation in patients with premature coronary artery disease (CAD).

Methods: The study group included 60 patients with stable CAD diagnosed before 45 years of age. The control group consisted of 33 healthy age- and gender-matched volunteers. Venous blood was sampled 3 times in order to assess circulating EPC count immediately before an exercise test (EPC 0) and at 15 min (EPC 15) and 60 min (EPC 60) after the exercise test.

Results: Circulating EPC count in the study group at rest and at 15 min after exercise was comparable (2.1 vs. 2.1 cell/μL, p = 0.35) and increased significantly at 60 min after exercise in comparison to resting values (2.1 vs. 3.2 cell/μL, p < 0.00001). In the control group, circulating EPC count increased significantly at 15 min after exercise (2.0 vs. 3.5 cell/μL, p < 0.0001) but later decreased at 60 min after exercise, although it remained greater than at rest (2.7 vs. 2.0 cell/μL, p < 0.0002). Circulating EPC count at rest and at 60 min after exercise was comparable in the two groups (2.1 vs. 2.0 cell/μL, p = 0.96; and 3.2 vs. 2.7 cell/μL, p = 0.13, respectively) but it was significantly lower in the study group compared to the control group at 15 min after exercise (2.1 vs. 3.5 cell/μL, p < 0.00001). Circulating EPC count at rest and at 15 min after exercise did not correlate with the number of stenosed coronary arteries but at 60 min after exercise it was greater in patients with one-vessel disease compared to those with two- or three-vessel disease (4.2 vs. 3.4 cell/μL, p = 0.01; and 4.2 vs. 2.3 cell/μL, p = 0.00003). However, no difference in circulating EPC count was seen at 60 min after exercise between patients with two- or three-vessel disease (3.4 vs. 2.3 cell/μL, p = 0.3).

Conclusions: 1. Circulating EPC count at rest is comparable between subjects with premature atherosclerosis and healthy volunteers. 2. A single bout of physical exercise causes a significant increase in circulating EPC count in both groups, but the dynamics of exercise-induced EPC mobilisation is different, with delayed exercise-induced EPC mobilisation in subjects with premature CAD. 3. The extent of atherosclerotic coronary lesions does not influence circulating EPC count at rest.