Exercise-induced upregulation of endothelial adhesion molecules in human skeletal muscle and number of circulating cells with remodeling properties

Multipotent cells have received great interest because of their potential capacity to repair and remodel peripheral tissues. We examined the effect of an acute exercise bout on the number of circulating cells with known remodeling properties and the level of factors in plasma and skeletal muscle tissue with potential to recruit these cells. Twenty healthy male subjects performed a 60-min cycling exercise. Blood samples for flow cytometry were drawn from 10 subjects (group 1) before and up to 2 h after exercise, and absolute cell counts of the classical (CD14⁺⁺CD16^–), intermediate (CD14⁺⁺CD16⁺), and nonclassical (CD14⁺CD16⁺⁺) monocyte (MO) subpopulations and of CD45^dimCD34⁺VEGFR2⁺ endothelial progenitor cells (EPCs) were measured by bead-based determination. Plasma samples and vastus lateralis muscle biopsies were obtained from the other 10 subjects (group 2). In group 1, all MO subsets were increased directly after exercise, with CD14⁺CD16⁺⁺ MOs showing the greatest fold increase. After 2 h, only CD14⁺⁺CD16^– MOs were increased compared with resting levels. The number of EPCs showed a trend toward increasing with exercise (P = 0.08). In group 2, the mRNA levels of the endothelial adhesion molecules ICAM-1, VCAM-1, and E-selectin increased in the skeletal muscle tissue. VEGF-A increased in exercised skeletal muscle and stimulated the expression of VCAM-1 and E-selectin in human umbilical vein endothelial cells. In conclusion, exercise increases MO subsets with different temporal patterns and enhances the capacity of skeletal muscle tissue to recruit circulating cells as shown by increased expression of endothelial adhesion molecules.

NEW & NOTEWORTHY In the present study we showed for the first time that the adhesion molecules ICAM-1, VCAM-1, and E-selectin, known to be able to recruit circulating cells to the peripheral tissue, increased in exercised human skeletal muscle concurrently with increased circulating levels of cells shown to have importance for skeletal muscle remodeling. These findings support the concept of cell recruitment from the circulation playing a role in skeletal muscle adaptation to exercise.

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