Abstract
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; V ̇ O 2 max ${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$ <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><msub><mi>O</mi> <mn>2</mn></msub> <mi>max</mi></mrow> </msub> <annotation>${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$</annotation></semantics> </math> ). Ten males (age: 23 ± 3 years; V ̇ O 2 max ${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$ <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><msub><mi>O</mi> <mn>2</mn></msub> <mi>max</mi></mrow> </msub> <annotation>${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$</annotation></semantics> </math> : 61.88 ± 4.68 mL kg min-1) undertook 1 h of treadmill running at 80% of V ̇ O 2 max ${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$ <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><msub><mi>O</mi> <mn>2</mn></msub> <mi>max</mi></mrow> </msub> <annotation>${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$</annotation></semantics> </math> . 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+CD45dim) and putative endothelial progenitor cells (CD34+CD133+, CD34+VEGFR2+, CD34+CD45dimVEGFR2+) were quantified using flow cytometry. Progenitor subpopulations (except for CD34+CD45dimVEGFR2+) increased at 0 h (P < 0.05) and returned to pre-exercise levels by 1 h. V ̇ O 2 max ${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$ <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><msub><mi>O</mi> <mn>2</mn></msub> <mi>max</mi></mrow> </msub> <annotation>${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$</annotation></semantics> </math> was positively associated with the exercise-induced progenitor cell response and there were statistically significant time × V ̇ O 2 max ${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$ <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><msub><mi>O</mi> <mn>2</mn></msub> <mi>max</mi></mrow> </msub> <annotation>${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$</annotation></semantics> </math> interactions for CD34+, CD34+CD45dim and CD34+CD133+ subpopulations but not VEGFR2-expressing progenitor cells. There were statistically significant correlations between V ̇ O 2 max ${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$ <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><msub><mi>O</mi> <mn>2</mn></msub> <mi>max</mi></mrow> </msub> <annotation>${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{max}}}}$</annotation></semantics> </math> and ingress (r > 0.70, P < 0.025) and egress (r > -0.77, P < 0.009) of progenitor cell subsets (CD34+, CD34+CD45dim, 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.