title: Reduced satellite cell numbers with spinal cord injury and aging in humans.
abstract: BACKGROUND
  Both sarcopenia and spinal cord injury (SCI) are characterized by the loss of skeletal muscle mass and function. Despite obvious similarities in atrophy between both models, differences in muscle fiber size and satellite cell content may exist on a muscle fiber type-specific level.
  
  
  METHODS
  In the present study, we compared skeletal muscle fiber characteristics between wheelchair-dependent young males with SCI (n = 8, 32 ± 4 yr), healthy elderly males (n = 8, 75 ± 2 yr), and young controls (n = 8, 31 ± 3 yr). Muscle biopsies were collected to determine skeletal muscle fiber type composition, fiber size, and satellite cell content.
  
  
  RESULTS
  Severe atrophy and a shift toward approximately 90% Type II muscle fibers were observed in muscle obtained from males with SCI. Muscle fiber size was substantially smaller in both the SCI (Types I and II fibers) and elderly subjects (Type II fibers) when compared with the controls. Satellite cell content was substantially lower in the wheelchair-dependent SCI subjects in both the Types I and II muscle fibers (0.049 ± 0.019 and 0.050 ± 0.005 satellite cells per fiber, respectively) when compared with the young controls (0.104 ± 0.011 and 0.117 ± 0.009 satellite cells per fiber, respectively). In the elderly, the number of satellite cells was lower in the Type II muscle fibers only (0.042 ± 0.005 vs 0.117 ± 0.009 satellite cells per fiber in the elderly vs young controls, respectively).
  
  
  CONCLUSIONS
  This is the first study to show that muscle fiber atrophy as observed with SCI (Types I and II fibers) and aging (Type II fibers) is accompanied by a muscle fiber type-specific reduction in satellite cell content in humans.
authors: NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Human Movement Sciences, Maastricht University Medical Centre+, Maastricht, The Netherlands. lex.verdijk@maastrichtuniversity.nl
authors: Lex B
authors: LB
authors: Verdijk
authors: Marlou L
authors: ML
authors: Dirks
authors: Tim
authors: T
authors: Snijders
authors: Jeanine J
authors: JJ
authors: Prompers
authors: Milou
authors: M
authors: Beelen
authors: Richard A M
authors: RA
authors: Jonkers
authors: Dick H J
authors: DH
authors: Thijssen
authors: Maria T E
authors: MT
authors: Hopman
authors: Luc J C
authors: LJ
authors: Van Loon
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology; D016022:Case-Control Studies; D002452:Cell Count; D006801:Humans; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology* / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000473:pathology* / Q000502:physiology; D009133:Muscular Atrophy / Q000473:pathology*; D010264:Paraplegia / Q000473:pathology; D055948:Sarcopenia / Q000473:pathology; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism* / Q000473:pathology*; D013119:Spinal Cord Injuries / Q000473:pathology*