title: Reduced masticatory function is related to lower satellite cell numbers in masseter muscle.
abstract: The physiology of masseter muscles is known to change in response to functional demands, but the effect on the satellite cell (SC) population is not known. In this study, the hypothesis is tested that a decreased functional demand of the masseter muscle causes a reduction of SCs. To this end, twelve 5-week-old male Sprague-Dawley rats were put on a soft diet (SD, n = 6) or a hard diet (HD, n = 6) and sacrificed after 14 days. Paraffin sections of the superficial masseter and the m. digastricus (control muscle) were stained with haematoxylin and eosin for tissue survey and with anti-myosin heavy chain (MHC) for slow and fast fibres. Frozen sections of both muscles were double-stained for collagen type IV and Pax7. Slow MHC fibres were equally distributed in the m. digastricus but only localized in a small area of the m. masseter. No differences between HD or SD for the m. digastricus were found. The m. masseter had more SCs per fibre in HD than in SD (0.093 ± 0.007 and 0.081 ± 0.008, respectively; P = 0.027). The m. masseter had more fibres per surface area than the m. digastricus in rats with an SD group (758.1 ± 101.6 and 568.4 ± 85.6, P = 0.047) and a HD group (737.7 ± 32.6 and 592.2 ± 82.2; P = 0.007). The m. digastricus had more SCs per fibre than the m. masseter in the SD group (0.094 ± 0.01 and 0.081 ± 0.008; P = 0.039). These results suggest that reduced masseter muscle function is related to a lower number of SCs. Reduced muscle function might decrease microdamage and hence the requirement of SCs in the muscle fibres.
authors: Department of Orthodontics and Craniofacial Biology, Radboud University Nijmegen Medical Centre, The Netherlands, Department of Orthodontics, University of Geneva, Switzerland and orthodontics@dent.umcn.nl.
authors: M A R
authors: MA
authors: Kuijpers
authors: Department of Orthodontics and Craniofacial Biology, Radboud University Nijmegen Medical Centre, The Netherlands.
authors: S
authors: S
authors: Grefte
authors: Department of Preventive and Curative Dentistry, Radboud University Nijmegen Medical Center, The Netherlands.
authors: E M
authors: EM
authors: Bronkhorst
authors: Department of Orthodontics and Craniofacial Biology, Radboud University Nijmegen Medical Centre, The Netherlands.
authors: C E L
authors: CE
authors: Carels
authors: Department of Orthodontics, University of Geneva, Switzerland and.
authors: S
authors: S
authors: Kiliaridis
authors: Department of Orthodontics and Craniofacial Biology, Radboud University Nijmegen Medical Centre, The Netherlands.
authors: J W
authors: JW
authors: Von den Hoff
mesh_terms: D000818:Animals; D002452:Cell Count; D024141:Collagen Type IV / Q000378:metabolism; D004032:Diet; D008297:Male; D008406:Masseter Muscle / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D009334:Neck Muscles / Q000166:cytology / Q000378:metabolism; D051763:PAX7 Transcription Factor / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D032496:Satellite Cells, Skeletal Muscle / Q000502:physiology*
chemical_list: D024141:Collagen Type IV; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; D018995:Myosin Heavy Chains