Masticatory muscles of mouse do not undergo atrophy in space

FASEB J. 2015 Jul;29(7):2769-79. doi: 10.1096/fj.14-267336. Epub 2015 Mar 20.


Muscle loading is important for maintaining muscle mass; when load is removed, atrophy is inevitable. However, in clinical situations such as critical care myopathy, masticatory muscles do not lose mass. Thus, their properties may be harnessed to preserve mass. We compared masticatory and appendicular muscles responses to microgravity, using mice aboard the space shuttle Space Transportation System-135. Age- and sex-matched controls remained on the ground. After 13 days of space flight, 1 masseter (MA) and tibialis anterior (TA) were frozen rapidly for biochemical and functional measurements, and the contralateral MA was processed for morphologic measurements. Flight TA muscles exhibited 20 ± 3% decreased muscle mass, 2-fold decreased phosphorylated (P)-Akt, and 4- to 12-fold increased atrogene expression. In contrast, MAs had no significant change in mass but a 3-fold increase in P-focal adhesion kinase, 1.5-fold increase in P-Akt, and 50-90% lower atrogene expression compared with limb muscles, which were unaltered in microgravity. Myofibril force measurements revealed that microgravity caused a 3-fold decrease in specific force and maximal shortening velocity in TA muscles. It is surprising that myofibril-specific force from both control and flight MAs were similar to flight TA muscles, yet power was compromised by 40% following flight. Continued loading in microgravity prevents atrophy, but masticatory muscles have a different set point that mimics disuse atrophy in the appendicular muscle.

Keywords: atrogenes; microgravity; muscle adaptations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biomechanical Phenomena
  • Female
  • Gene Expression
  • Mastication / physiology
  • Masticatory Muscles / pathology*
  • Masticatory Muscles / physiopathology
  • Mice
  • Mice, Inbred C57BL
  • Muscle Contraction / physiology
  • Muscle Proteins / genetics
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / physiopathology
  • Muscular Atrophy / etiology
  • Muscular Atrophy / pathology
  • Muscular Atrophy / physiopathology
  • Myofibrils / pathology
  • Myofibrils / physiology
  • SKP Cullin F-Box Protein Ligases / genetics
  • Space Flight*
  • Tripartite Motif Proteins
  • Ubiquitin-Protein Ligases / genetics
  • Weight-Bearing / physiology
  • Weightlessness / adverse effects*


  • Muscle Proteins
  • Tripartite Motif Proteins
  • Fbxo32 protein, mouse
  • SKP Cullin F-Box Protein Ligases
  • Trim63 protein, mouse
  • Ubiquitin-Protein Ligases