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Normal Myogenic Programming of Skeletal Muscle Satellite Cells from Spinal Cord Injured Subjects
Author(s) -
Savikj Mladen,
Kostovski Emil,
Ruby Maxwell Alexander,
Iversen Per Ole,
Zierath Juleen,
Krook Anna,
Widegren Ulrika
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1082.5
Subject(s) - myf5 , myogenesis , skeletal muscle , myogenic regulatory factors , myogenin , myocyte , desmin , endocrinology , medicine , biology , myod , microbiology and biotechnology , chemistry , immunohistochemistry , immunology , vimentin
Spinal cord injury (SCI) leads to changes in the skeletal muscle below the level of injury, e.g. atrophy and fiber composition change, followed by metabolic changes at both local and systemic level. Satellite cells grown in vitro have been shown to reflect the changes in the skeletal muscle in response to type 2 diabetes, obesity, exercise and neurological diseases. In this study, we have assessed the myogenic programming in satellite cells from skeletal muscle after SCI. We hypothesized that the injury would affect the ability to produce a normal muscle phenotype. Satellite cells were isolated from vastus lateralis biopsies of six able bodied (AB) and eight individuals with a longstanding (>1year) SCI. Primary skeletal muscle cultures were grown and differentiated into myotubes. The expression of myogenic regulatory factors (MRFs) was determined by quantitative PCR. The amount of skeletal muscle specific structural proteins, as well as regulators of protein synthesis, protein degradation and fatty acid oxidation, were determined by Western blot. Immunohistochemistry was performed for structural and proliferation markers. The capacity for protein synthesis and fatty acid oxidation was determined by radioactive tracer‐based metabolic assays. Fluorescent microscopy has shown that both AB and SCI groups were able to form multinucleated myotubes with an abundance of Desmin. The nuclear localization of Ki67, a proliferation marker, was high in myoblasts, and decreased through differentiation in myotubes. The expression pattern of MRFs was mainly unaffected by SCI. Both groups expressed equal levels of Pax7, Myf5, Myf6 and Myogenin, while myoblasts from SCI subjects had increased Myod1. The protein amounts of skeletal muscle specific structural proteins (Desmin, Myh 1/2 and Myh7) increased through differentiation in both study groups. The myotubes from spinal cord injured contained more both fast and slow type myosin heavy chain. The rate of incorporation of radiolabelled phenylalanine into protein was equal between both study groups of myotubes. The protein content of the members of Akt‐mTOR signalling axis was unchanged. The same was true for FoxO transcription factors and their targets, involved in protein degradation. Oxidative capacity of the myotubes was equal among the two groups, determined by radiolabelled water production from palmitic acid, as well as the protein content of phosphorylated and total ACC. Our results indicate that the myogenic programming of satellite cells is unchanged in spinal cord injured individuals. This may have implications for targeted interventions for satellite cell activation in an attempt to combat skeletal muscle atrophy in the spinal cord injured.