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. 2019 Nov 1;127(5):1419-1426.
doi: 10.1152/japplphysiol.01123.2018. Epub 2019 Sep 12.

Consistent expression pattern of myogenic regulatory factors in whole muscle and isolated human muscle satellite cells after eccentric contractions in humans

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Consistent expression pattern of myogenic regulatory factors in whole muscle and isolated human muscle satellite cells after eccentric contractions in humans

Joshua P Nederveen et al. J Appl Physiol (1985). .

Abstract

Skeletal muscle satellite cells (SC) play an important role in muscle repair following injury. The regulation of SC activity is governed by myogenic regulatory factors (MRF), including MyoD, Myf5, myogenin, and MRF4. The mRNA expression of these MRF in humans following muscle damage has been predominately measured in whole muscle homogenates. Whether the temporal expression of MRF in a whole muscle homogenate reflects SC-specific expression of MRF remains largely unknown. Sixteen young men (23.1 ± 1.0 yr) performed 300 unilateral eccentric contractions (180°/s) of the knee extensors. Percutaneous muscle biopsies from the vastus lateralis were taken before (Pre) and 48 h postexercise. Fluorescence-activated cell sorting analysis was utilized to purify NCAM+ muscle SC from the whole muscle homogenate. Forty-eight hours post-eccentric exercise, MyoD, Myf5, and myogenin mRNA expression were increased in the whole muscle homogenate (~1.4-, ~4.0-, ~1.7-fold, respectively, P < 0.05) and in isolated SC (~19.3-, ~17.5-, ~58.9-fold, respectively, P < 0.05). MRF4 mRNA expression was not increased 48 h postexercise in the whole muscle homogenate (P > 0.05) or in isolated SC (P > 0.05). In conclusion, our results suggest that the directional changes in mRNA expression of the MRF in a whole muscle homogenate in response to acute eccentric exercise reflects that observed in isolated muscle SC.NEW & NOTEWORTHY The myogenic program is controlled via transcription factors referred to as myogenic regulatory factors (MRF). Previous studies have derived MRF expression from whole muscle homogenates, but little work has examined whether the mRNA expression of these transcripts reflects the pattern of expression in the actual population of satellite cells (SC). We report that MRF expression from an enriched SC population reflects the directional pattern of expression from skeletal muscle biopsy samples following eccentric contractions.

Keywords: fluorescence-activated cell sorting; mRNA expression; myogenic regulator factors; satellite cell.

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Conflict of interest statement

No conflicts of interest, financial or otherwise, are declared by the authors.

Figures

Fig. 1.
Fig. 1.
Representative NCAM+ population in skeletal muscle biopsy sorted via flow cytometry. Forward scatter (FSC; x-axis) and side scatter (SSC; y-axis) were used to select a population of cells with 7-AAD viability dye to exclude nonviable cells. NCAM+-viable cells are represented in AF647 channel (x-axis) against a dump channel (y-axis). Cell populations representative of before exercise (A–C) and 48 h post-eccentric exercise (D–F) are shown.
Fig. 2.
Fig. 2.
Myogenic regulatory factor (MRF) changes 48 h following eccentric damage in both isolated purified NCAM+ cells and a whole muscle (W.M) homogenate. Shown are MyoD (A and E, respectively), Myf5 (B and F, respectively), MRF4 (C and G, respectively), and myogenin (D and H, respectively) mRNA expression. Data are normalized to GAPDH. Values are means ± SE and reported as arbitrary units (a.u). *Significantly different compared with Pre (P < 0.05).
Fig. 3.
Fig. 3.
NCAM+ events/mg of fresh muscle tissue assessed via flow cytometry before (Pre) and 48 h (Post) after a bout of eccentric contraction-induced muscle damage. *Post was significantly different compared with Pre (P < 0.05).

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