title: Steep increase in myonuclear domain size during infancy.
abstract: We investigated whether myonuclear number increases in proportion to the increase in fiber size during maturational growth of skeletal muscle. Thoraco-abdominal muscle tissue was obtained from twenty 6-day to 15-year-old boys and girls during cardiothoracic surgery. Cross-sections were stained by anti-laminin for the basal lamina and by DAPI to identify nuclei. Basal lamina was traced on digital images to measure the fiber cross-sectional area (FCSA). Nuclei located within the basal lamina were considered myonuclei if pax7-negative and satellite cell nuclei if pax7-positive. Samples of two children were excluded from analysis because of clear signs of hypoxia as shown by positive carbonic anhydrase IX staining. Linear regression showed that FCSA increased with age by 187 μm(2) ·per annum (R(2) = 0.90; P < 0.001). Satellite cell density showed a dramatic decrease in the first months of life, but this was not accompanied by an increase in myonuclei per muscle fiber cross-section. Till four years of age the number of myonuclei per muscle fiber cross-section remained relatively constant but increased thereafter. Myonuclear domain size showed a steep increase during infancy and reached adult values in the young adolescent phase.
authors.affiliation: Department of Biomedical Engineering, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, the Netherlands. tammo.delhaas@maastrichtuniversity.nl
authors.forename: Tammo
authors.initials: T
authors.lastname: Delhaas
authors.forename: Sander F T
authors.initials: SF
authors.lastname: Van der Meer
authors.forename: Gert
authors.initials: G
authors.lastname: Schaart
authors.forename: Hans
authors.initials: H
authors.lastname: Degens
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Drost
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015415:Biomarkers / Q000032:analysis; D001706:Biopsy; D049108:Cell Enlargement; D002467:Cell Nucleus / Q000737:chemistry / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007211:Indoles; D007223:Infant; D007231:Infant, Newborn; D007797:Laminin / Q000032:analysis; D016014:Linear Models; D008297:Male; D008856:Microscopy, Fluorescence; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000502:physiology*; D051763:PAX7 Transcription Factor / Q000032:analysis; D032496:Satellite Cells, Skeletal Muscle / Q000737:chemistry / Q000502:physiology*; D013194:Staining and Labeling / Q000379:methods
chemical_list: D015415:Biomarkers; D005456:Fluorescent Dyes; D007211:Indoles; D007797:Laminin; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; C007293:DAPI