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^dimVEGFR2⁺) 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^dimVEGFR2⁺ 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^dimVEGFR2⁺: 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.