The α7 integrin is prerequisite for Sca-1⁺ stem cell accumulation in skeletal muscle following exercise.

(A) Localization of stem cell antigen-1 (Sca-1) (arrows, TRITC-red) positive mononuclear cells and α7 integrin (FITC-green) in the interstitium of wild type (WT), α7 transgenic (α7Tg), and α7^−/− skeletal muscle in the sedentary state (Sed) or 24 hr post-exercise (Ex) at 20×. (B) Localization of Sca-1 (TRITC-red) positive mononuclear cells and α7 integrin (FITC-green) in the myotendinous junction and in close proximity to vessels and nerves of WT and α7Tg skeletal muscle in the sedentary state (Sed) or post-exercise (Ex). (C) FACS analysis of Sca-1 and CD45 expression on mononuclear cells extracted from skeletal muscle in the sedentary state and post-exercise. (D) Quantitation of Sca-1⁺CD45⁻ mononuclear cells in the sedentary state (Sed) and 24 hr post-exercise (Ex). (E) Representative images showing co-localization of Sca-1⁺ cells with leukemia inhibitory factor (LIF) in the vascular niche of WT and α7Tg muscle. Scale bar = 10 µm. Data are means ± SEM, n = 4–6/group for C and D. * P<0.05 vs. WT Sed and § P<0.05 vs. all groups.