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.

Capillary ultrastructure and mitochondrial volume density in skeletal muscle in relation to reduced exercise capacity of patients with intermittent claudication

“…All biopsies were taken from the participants at rest within a 6-wk period. Specimens were chemically fixed in a 6.25% (vol/vol) glutaraldehyde solution buffered with 0.1 M sodium cacodylate HCl (pH 7.4) and stored at 4°C until analysis (9).…”

“…With the use of these light micrographs, the number of capillary profiles and that of muscle fibers were quantified using the forbidden line rule (52). The mean cross-sectional fiber area (MCSFA) was estimated by point counting, and capillary profile density and capillary-to-fiber (C/F) ratio were calculated, as described previously (9).…”

“…Ultrathin sections (50 -60 nm in thickness) of the Epon blocks were prepared with an Ultracut ultramicrotome (Reichert-Jung, Bensheim, Germany), floated on 200-mesh copper grids (Plano, Wetzlar, Germany) and contrasted with uranyl acetate and lead citrate, as previously described (9,27). Imaging was carried out using a transmission electron microscope (Philips EM 400).…”

Skeletal and cardiac muscle pericytes: Functions and therapeutic potential

“…Recent evidence suggests that pericytes in human skeletal muscle proliferate/mobilize in response to exercise-induced angiogenesis with a significant increase in pericyte density, thickness, and endothelial coverage and a concurrent decrease in basement membrane density and thickness in ultrastructural analyses of capillaries in human muscle biopsies (Baum et al, 2015). Furthermore skeletal muscle pericytes are also considered to be myogenic precursors distinct from satellite cells, themselves thought to be the primary source of postnatal myoblasts (Zammit et al, 2006).…”

Angelica sinensis polysaccharides promotes apoptosis in human breast cancer cells via CREB-regulated caspase-3 activation

“…ASP has various bioactivities, such as hematopoiesis, immunomodulation, radioprotection, and anti-tumor activity [9,10]. And previous study indicated that angelica sinensis suppressed nitric oxide (NO) and prostaglandin E secretions in vitro.…”