PAX7+ satellite cells in young and older adults following resistance exercise

Abstract

Introduction: Resistance exercise (RE) stimulates a muscle protein anabolic response partially through enhanced satellite cell (SC) activity, however, age- and gender-related changes in SC content over a 24-h time course are not known.

Methods: Ten young (27 ± 2 years) men and women and 11 older (70 ± 2 years) men and women performed an acute bout of RE. Myofiber and SC characteristics were determined from muscle biopsies of the vastus lateralis using immunohistochemistry. Immunoblotting was used to determine phosphorylation of cyclin-dependent kinase-2 and protein expression of p27(Kip1) and cyclin D1.

Results: Pax7+ SC were significantly increased in young men 24 h following RE. Percent SC were significantly increased in older women at 6 and 24 h following RE. Aging decreased myonuclear domain and increased protein expression of p27(Kip1) .

Conclusions: An acute bout of RE increases SC content in young men at 24 h and older women at 6 and 24 h.

Copyright © 2012 Wiley Periodicals, Inc.

Figures

Figure 1

Immunohistochemical detection on a muscle cross section of a healthy younger male demonstrates sarcolemma by anti-laminin in green, myosin heavy chain type I positive muscle fibers in red, and myosin heavy chain type II muscle fibers are black (negative for myosin heavy chain type I)

Figure 2

Immunohistochemical detection of skeletal muscle SC on a single cross section of a healthy older male at baseline. Nuclei were stained blue, laminin were stained green, and Pax7+ cells (denoting skeletal muscle SC) were identified as any nuclei localized to the sarcolemma and stained red.

Figure 3

The number of Pax7+ cells at baseline and at 6 and 24 h post resistance exercise in young (black lines) and older (grey lines) men (solid lines) and women (dashed lines). *Different from baseline, P ≤ 0.006. †Different from all groups at 24 h, P ≤ 0.006.