title: Satellite cell depletion prevents fiber hypertrophy in skeletal muscle.
abstract: The largest mammalian cells are the muscle fibers, and they have multiple nuclei to support their large cytoplasmic volumes. During hypertrophic growth, new myonuclei are recruited from satellite stem cells into the fiber syncytia, but it was recently suggested that such recruitment is not obligatory: overload hypertrophy after synergist ablation of the plantaris muscle appeared normal in transgenic mice in which most of the satellite cells were abolished. When we essentially repeated these experiments analyzing the muscles by immunohistochemistry and in vivo and ex vivo imaging, we found that overload hypertrophy was prevented in the satellite cell-deficient mice, in both the plantaris and the extensor digitorum longus muscles. We attribute the previous findings to a reliance on muscle mass as a proxy for fiber hypertrophy, and to the inclusion of a significant number of regenerating fibers in the analysis. We discuss that there is currently no model in which functional, sustainable hypertrophy has been unequivocally demonstrated in the absence of satellite cells; an exception is re-growth, which can occur using previously recruited myonuclei without addition of new myonuclei.
authors.affiliation: Department of Biosciences, University of Oslo, Blindern, Oslo N-0316, Norway.
authors.forename: Ingrid M
authors.initials: IM
authors.lastname: Egner
authors.affiliation: Department of Biosciences, University of Oslo, Blindern, Oslo N-0316, Norway Department of Health Sciences, Kristiania University College, P.O. Box 1190, Sentrum, Oslo N-0107, Norway.
authors.forename: Jo C
authors.identifier: 0000-0001-8163-5849
authors.initials: JC
authors.lastname: Bruusgaard
authors.affiliation: Department of Biosciences, University of Oslo, Blindern, Oslo N-0316, Norway kgunder@ibv.uio.no.
authors.forename: Kristian
authors.identifier: 0000-0001-9040-3126
authors.initials: K
authors.lastname: Gundersen
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism / Q000502:physiology; D005260:Female; D006984:Hypertrophy / Q000503:physiopathology / Q000517:prevention & control; D007150:Immunohistochemistry; D051379:Mice; D008822:Mice, Transgenic; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology* / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism / Q000502:physiology*
keywords: Hypertrophy; Mouse; Plasticity; Satellite cells; Skeletal muscle; Stem cells