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Quantification and characterization of grouped type I myofibers in human aging
Author(s) -
Kelly Neil A.,
Hammond Kelley G.,
Stec Michael J.,
Bickel C. Scott,
Windham Samuel T.,
Tuggle S. Craig,
Bamman Marcas M.
Publication year - 2018
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.25711
Subject(s) - reinnervation , denervation , myocyte , serca , biology , anatomy , atpase , medicine , endocrinology , pathology , biochemistry , enzyme
Myofiber type grouping is a histological hallmark of age‐related motor unit remodeling. Despite the accepted concept that denervation–reinnervation events lead to myofiber type grouping, the completeness of those conversions remains unknown. Methods Type I myofiber grouping was assessed in vastus lateralis biopsies from Young (26 ± 4 years; n = 27) and Older (66 ± 4 years; n = 91) adults. Grouped and ungrouped type I myofibers were evaluated for phenotypic differences. Results Higher type I grouping in Older versus Young was driven by more myofibers per group (i.e., larger group size) ( P < 0.05). In Older only, grouped type I myofibers displayed larger cross‐sectional area, more myonuclei, lower capillary supply, and more sarco(endo)plasmic reticulum calcium ATPase I (SERCA I) expression ( P < 0.05) than ungrouped type I myofibers. Discussion Grouped type I myofibers retain type II characteristics suggesting that conversion during denervation–reinnervation events is either progressive or incomplete. Muscle Nerve 57 : E52–E59, 2018