Laminin-111 improves skeletal muscle stem cell quantity and function following eccentric exercise

Laminin-111 (α1, β1, γ1; LM-111) is an important component of the extracellular matrix that is required for formation of skeletal muscle during embryonic development. Recent studies suggest that LM-111 supplementation can enhance satellite cell proliferation and muscle function in mouse models of muscular dystrophy. The purpose of this study was to determine the extent to which LM-111 can alter satellite and nonsatellite stem cell quantity following eccentric exercise-induced damage in young adult, healthy mice. One week following injection of LM-111 or saline, mice either remained sedentary or were subjected to a single bout of downhill running (EX). While one muscle was preserved for evaluation of satellite cell number, the other muscle was processed for isolation of mesenchymal stem cells (MSCs; Sca-1⁺CD45^-) via FACS at 24 hours postexercise. Satellite cell number was approximately twofold higher in LM-111/EX compared with all other groups (p <.05), and the number of satellite cells expressing the proliferation marker Ki67 was 50% to threefold higher in LM-111/EX compared with all other groups (p <.05). LM-111 also increased the quantity of embryonic myosin heavy chain-positive (eMHC⁺) fibers in young mice after eccentric exercise (p <.05). Although MSC percentage and number were not altered, MSC proinflammatory gene expression was decreased, and hepatocyte growth factor gene expression was increased in the presence of LM-111 (p <.05). Together, these data suggest that LM-111 supplementation provides a viable solution for increasing skeletal muscle stem cell number and/or function, ultimately allowing for improvements in the regenerative response to eccentric exercise.