title: Angiogenesis-related ultrastructural changes to capillaries in human skeletal muscle in response to endurance exercise.
abstract: The ultrastructure of capillaries in skeletal muscle was morphometrically assessed in vastus lateralis muscle (VL) biopsies taken before and after exercise from 22 participants of two training studies. In study 1 (8 wk of ergometer training), light microscopy revealed capillary-fiber (C/F) ratio (+27%) and capillary density (+16%) to be higher (P ≤ 0.05) in postexercise biopsies than in preexercise biopsies from all 10 participants. In study 2 (6 mo of moderate running), C/F ratio and capillary density were increased (+23% and +20%; respectively, P ≤ 0.05) in VL biopsies from 6 angiogenesis responders (AR) after training, whereas 6 nonangiogenesis responders (NR) showed nonsignificant changes in these structural indicators (-4%/-4%, respectively). Forty capillary profiles per participant were evaluated by point and intersection counting on cross sections after transmission electron microscopy. In study 1, volume density (Vv) and mean arithmetic thickness (T) of endothelial cells (ECs; +19%/+17%, respectively) and pericytes (PCs; +20%/+21%, respectively) were higher (P ≤ 0.05), whereas Vv and T of the pericapillary basement membrane (BM) were -23%/-22% lower (P ≤ 0.05), respectively, in posttraining biopsies. In study 2, exercise-related differences between AR and NR-groups were found for Vv and T of PCs (AR, +26%/+22%, respectively, both P ≤ 0.05; NR, +1%/-3%, respectively, both P > 0.05) and BM (AR, -14%/-13%, respectively, both P ≤ 0.05; NR, -9%/-11%, respectively, P = 0.07/0.10). Vv and T of ECs were higher (AR, +16%/+18%, respectively; NR, +6%/+6%, respectively; all P ≤ 0.05) in both groups. The PC coverage was higher (+13%, P ≤ 0.05) in VL biopsies of individuals in the AR group but nonsignificantly altered (+3%, P > 0.05) in those of the NR group after training. Our study suggests that intensified PC mobilization and BM thinning are related to exercise-induced angiogenesis in human skeletal muscle, whereas training per se induces EC-thickening.
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Oliver
authors.initials: O
authors.lastname: Baum
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Gübeli
authors.affiliation: Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Frese
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Torchetti
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Corinna
authors.initials: C
authors.lastname: Malik
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Odriozola
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Franziska
authors.initials: F
authors.lastname: Graber
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Hans
authors.initials: H
authors.lastname: Hoppeler
authors.affiliation: Institute of Anatomy, University of Bern, Bern, Switzerland; and.
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Tschanz
mesh_terms: D000328:Adult; D002196:Capillaries / Q000648:ultrastructure*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology* / Q000648:ultrastructure*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*
keywords: capillary; electron microscopy; morphometry; skeletal muscle biopsies