The magnitude of exercise-induced progenitor cell mobilisation and extravasation is positively associated with cardiorespiratory fitness.

CD34⁺ progenitor cells with angiogenic capabilities traffic into blood during exercise and extravasate afterwards but the magnitude of this response varies between people. We examined whether exercise-induced progenitor cell trafficking is influenced by cardiorespiratory fitness (maximum oxygen uptake; ${\dot{V}}_{O_2\max }$ ). Ten males (age: 23 ± 3 years; ${\dot{V}}_{O_2\max }$ : 61.88 ± 4.68 mL kg min^-1) undertook 1 h of treadmill running at 80% of ${\dot{V}}_{O_2\max }$ . Blood samples were collected before exercise (Pre), in the final minute of exercise (0 h) and afterwards at 0.25, 1 and 24 h. Pan-progenitor cells (CD34⁺, CD34⁺CD45^dim) and putative endothelial progenitor cells (CD34⁺CD133⁺, CD34⁺VEGFR2⁺, CD34⁺CD45^dimVEGFR2⁺) were quantified using flow cytometry. Progenitor subpopulations (except for CD34⁺CD45^dimVEGFR2⁺) increased at 0 h (P < 0.05) and returned to pre-exercise levels by 1 h. ${\dot{V}}_{O_2\max }$ was positively associated with the exercise-induced progenitor cell response and there were statistically significant time × ${\dot{V}}_{O_2\max }$ interactions for CD34⁺, CD34⁺CD45^dim and CD34+CD133⁺ subpopulations but not VEGFR2-expressing progenitor cells. There were statistically significant correlations between ${\dot{V}}_{O_2\max }$ and ingress (r > 0.70, P < 0.025) and egress (r > -0.77, P < 0.009) of progenitor cell subsets (CD34⁺, CD34⁺CD45^dim, CD34⁺CD133⁺), showing that cardiorespiratory fitness influences the magnitude of progenitor cell mobilisation into the blood and subsequent extravasation. These data may provide a link between high levels of cardiorespiratory fitness and vascular health.