AUTHOR=Andries Anke , Deschrevel Jorieke , Maes Karen , De Beukelaer Nathalie , Corvelyn Marlies , Staut Lauraine , De Houwer Hannah , Costamagna Domiziana , Nijs Stefaan , Metsemakers Willem-Jan , Nijs Elga , Hens Greet , De Wachter Eva , Prinsen Sandra , Desloovere Kaat , Van Campenhout Anja , Gayan-Ramirez Ghislaine 

TITLE=Histological analysis of the medial gastrocnemius muscle in young healthy children

JOURNAL=Frontiers in Physiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2024.1336283

DOI=10.3389/fphys.2024.1336283

ISSN=1664-042X

ABSTRACT=<p><bold>Introduction:</bold> Histological data on muscle fiber size and proportion in (very) young typically developing (TD) children is not well documented and data on capillarization and satellite cell content are also lacking.</p><p><bold>Aims:</bold> This study investigated the microscopic properties of the medial gastrocnemius muscle in growing TD children, grouped according to age and gender to provide normal reference values in healthy children.</p><p><bold>Methods:</bold> Microbiopsies of the medial gastrocnemius (MG) muscle were collected in 46 TD boys and girls aged 2–10 years subdivided into 4 age groups (2–4, 4–6, 6–8 and 8–10 years). Sections were immunostained to assess fiber type cross-sectional area (fCSA) and proportion, the number of satellite cells (SC), capillary to fiber ratio (C/F), capillary density for type I and II fiber (CFD), capillary domain, capillary-to-fiber perimeter exchange index (CFPE) and heterogeneity index. fCSA was normalized to fibula length<sup>2</sup> and the coefficient of variation (CV) was calculated to reflect fCSA intrasubject variability.</p><p><bold>Results:</bold> Absolute fCSA of all fibers increased with age (r = 0.72, <italic>p</italic> &lt; 0.001) but more in boys (+112%, <italic>p</italic> &lt; 0.05) than in girls (+48%, <italic>p</italic> &gt; 0.05) Normalized fCSA, CV and fiber proportion did not differ between age groups and gender. C/F was strongly correlated with age in boys (r = 0.83, <italic>p</italic> &lt; 0.001), and to a lesser extent in girls (r = 0.37, <italic>p</italic> = 0.115), while other capillary parameters as well as the number of SC remained stable with increasing age in boys and girls.</p><p><bold>Discussion:</bold> This study provides reference values of histological measures in MG according to age in normally growing boys and girls. These data may be used as a reference to determine disease impact and efficacy of therapeutic approach on the muscle.</p>