Figure 1.

LM-111 treatment increases α7B integrin subunit protein expression in aged plantaris muscle of wild-type mice following chronic mechanical loading. Laminin-111 (LM-111) or saline was administered by intraperitoneal (i.p.) injection to 3- or 22-mo-old wild-type mice 1 wk prior to initiation of chronic mechanical loading induced by myotenectomy (MTE) and muscle was evaluated 2 wk post-MTE (A). LM-111 is present in skeletal muscle 3 d following i.p. injection (top panel). α7B integrin protein demonstrated a punctate pattern of expression in close proximity to DAPI⁺ nuclei (bottom panel, arrows indicate colocalization of integrin expression with DAPI-stained nuclei around in inside the fiber) (B). Total α7B integrin subunit protein expression in aged plantaris was increased with LM-111 treatment compared to age-matched sham and saline-treated controls (C). The percentage of fibers with >50% integrin localization at the sarcolemma was increased in young muscle post-MTE, but not aged muscle. (D) Graphical depiction of integrin enrichment near DAPI⁺ nuclei outside and inside muscle fibers with LM-111 treatment and speculative changes in mechanosensing. n = 4–7/group. ^‡ vs age-matched sham and saline-treated groups. All values are mean ± SEM. * vs age-matched sham group. Data are expressed relative to young sham for each muscle.