Blood Flow Restriction Exercise Attenuates the Exercise-Induced Endothelial Progenitor Cell Response in Healthy, Young Men

Endothelial progenitor cells (EPCs) are a vasculogenic subset of progenitors, which play a key role in maintenance of endothelial integrity. These cells are exercise-responsive, and thus exercise may play a key role in vascular repair and maintenance via mobilization of such cells. Blood flow restriction exercise, due to the augmentation of local tissue hypoxia, may promote exercise-induced EPC mobilization. Nine, healthy, young (18-30 years) males participated in the study. Participants undertook 2 trials of single leg knee extensor (KE) exercise, at 60% of thigh occlusion pressure (4 sets at 30% maximal torque) (blood flow restriction; BFR) or non- blood flow restriction (non-BFR), in a fasted state. Blood was taken prior, immediately after, and 30 min after exercise. Blood was used for the quantification of hematopoietic progenitor cells (HPCs: CD34(+)CD45(dim)), EPCs (CD34(+)VEGFR2(+)/CD34(+)CD45(dim)VEGFR2(+)) by flow cytometry. Our results show that unilateral KE exercise did not affect circulating HPC levels (p = 0.856), but did result in increases in both CD34(+)VEGFR2(+) and CD34(+)CD45(dim)VEGFR2(+) EPCs, but only in the non-BFR trial (CD34(+)VEGFR2(+): 269 +/- 42 cells mL(-1) to 573 +/- 90 cells mL(-1), pre- to immediately post-exercise, p = 0.008; CD34(+)CD45(dim)VEGFR2(+): 129 +/- 21 cells mL(-1) to 313 +/- 103 cells mL(-1), pre- to 30 min post-exercise, p = 0.010). In conclusion, low load BFR exercise did not result in significant circulating changes in EPCs in the post-exercise recovery period and may impair exercise-induced EPC mobilization compared to non-BFR exercise.