Hematopoietic Stem and Progenitor Cell (HSPC) Mobilization Responses to Different Exercise Intensities in Young and Older Adults

IntroductionHematopoietic stem and progenitor cells (HSPC) are responsible for the reconstitution of blood cells and thought to contribute to peripheral tissue repair. Following acute exercise in young adults, HSPC are mobilized from their niche in bone marrow into circulation, however the kinetics of mobilization following exercise is not well understood in older adults. In the present study, we aimed to investigate how exercise intensity influences mobilization of specific subpopulations of HSPC, and how mobilization is affected by aging.MethodsHealthy older men (OM; 69.9 +/- 2.0 years) and young men (YM; 21.5 +/- 0.8 years) performed three separate bouts of exercise on a cycle ergometer: 70% of their peak work rate (WRpeak) until volitional fatigue, 30% of their WRpeak work matched to the 70% WRpeak trial, and a high intensity interval training (HIIT) trial. Blood samples were collected before, immediately post, and 10, 30, and 60 min post-exercise. Total blood cells, hematocrit, and mononuclear cells isolated by density gradient centrifugation were quantified using flow cytometry.ResultsMononuclear cells, CD34+, CD34+/CD38+, CD34+/CD110+, CD3+/CD(16 + 56)+, CD11c+/CD123-, and CD11c-/CD123+ cells per millilitre of blood increased immediately post-exercise, but predominately in the 70% WRpeak trial in both OM and YM.ConclusionTaken together, our evidence suggests that higher intensity exercise but also volume is necessary for the mobilization of HSPC. Furthermore, the pattern of mobilization was nearly identical in OM as compared to YM though to a lesser extent than their younger counterparts.