Abstract # 1810 Exercise induces a differential mobilisation of haematopoietic stem cell subsets into peripheral blood which is partly influenced by donor age.

Abstract

Exercise-induced leukocyte mobilisation is well defined, but few studies have examined their precursors – haematopoietic stem cells (HSCs). Seventeen males (33 ± 13 years, BMI 24 ± 3 kg·m2 and VO2max 60 ± 5 ml·kg·min) ran for 60 min at 80% VO2max. Blood was collected at rest, during the final minute of exercise, then 15, 60 and 120 min later. HSC populations were identified using flow cytometry: HSCs (CD34+CD45dim); Common Lymphoid Progenitor cells (CLP, CD34+CD45dimCD38-CD7+); Common Myeloid Progenitor cells (CMP, CD34+CD45dimCD38+CD123+CD45RA-); Megakaryocyte/Erythroid Progenitor cells (MEP, CD34+CD45dimCD38+CD123-CD45RA-); and Granulocyte/Macrophage Progenitor cells (GMP, CD34+CD45dimCD38+CD123+CD45RA+). HSCs increased by 100% during exercise, returning to baseline within 15 min, and fell 10% below baseline 60–120 min post-exercise (p η 2 = 0.44). CLP, CMP and GMPs were un-changed during or following exercise, but CMPs and GMPs fell 30–40% below baseline 1–2 h later (p’s η 2 = 0.37). HSC mobilisation was higher (+80%) in younger men (n = 10, 23 ± 3 years) compared to older men (n = 7, 48 ± 5 years; interaction p η 2 = 0.15). Controlling statistically for absolute heart rate during exercise attenuated the age-effect (p > 0.05; η 2 = 0.14), suggesting the smaller HSC mobilisation in older men was partly due to lower cardiac output and concomitant haemodynamic/shear forces. Exercise-induced HSC mobilisation could increase apheresis yields for transplant, but compared to younger donors, the elderly may require a more prolonged stimulus.