Mechanical loading of tissue engineered skeletal muscle prevents dexamethasone induced myotube atrophy

Kathryn W Aguilar-Agon,Mark P Lewis,Jacob W Fleming,Andrew J Capel,Darren J Player,Neil R W Martin

doi:10.1007/s10974-020-09589-0

Abstract

Skeletal muscle atrophy as a consequence of acute and chronic illness, immobilisation, muscular dystrophies and aging, leads to severe muscle weakness, inactivity and increased mortality. Mechanical loading is thought to be the primary driver for skeletal muscle hypertrophy, however the extent to which mechanical loading can offset muscle catabolism has not been thoroughly explored. In vitro 3D-models of skeletal muscle provide a controllable, high throughput environment and mitigating many of the ethical and methodological constraints present during in vivo experimentation. This work aimed to determine if mechanical loading would offset dexamethasone (DEX) induced skeletal muscle atrophy, in muscle engineered using the C2C12 murine cell line. Mechanical loading successfully offset myotube atrophy and functional degeneration associated with DEX regardless of whether the loading occurred before or after 24 h of DEX treatment. Furthermore, mechanical load prevented increases in MuRF-1 and MAFbx mRNA expression, critical regulators of muscle atrophy. Overall, we demonstrate the application of tissue engineered muscle to study skeletal muscle health and disease, offering great potential for future use to better understand treatment modalities for skeletal muscle atrophy.

Highlights

Skeletal muscle atrophy is known to occur as a consequence of acute and chronic illnesses, immobilisation or bed rest, muscular dystrophies, and aging
To determine if mechanical loading had protected or reversed DEX-induced decreases in maximal tetanic skeletal muscle force, engineered muscles were immersed in 3 mL Krebs–Ringer-HEPES buffer (KRH; 10 mM HEPES, 138 mM NaCl, 4.7 mM KCl, 1.25 mM C aCl2, 1.25 mM MgSO4, 5 mM Glucose, 0.05% bovine serum albumin in dH20) and attached to a force transducer (403A, Auora Scientific Ltd, UK)
Maximal tetanic force output and average crosssectional area (CSA) of the myotubes in the engineered skeletal muscles was measured after 24 h (Fig. 1)

Summary

Introduction

Skeletal muscle atrophy is known to occur as a consequence of acute and chronic illnesses (such as sepsis, chronic kidney disease and cancer cachexia), immobilisation or bed rest, muscular dystrophies, and aging. This can lead to severe muscle weakness, inactivity and reduced quality of life for the patients. The examination of muscle atrophy in mice containing null deletions of MAFbx (Bodine et al 2001) or MuRF-1 (Bodine et al 2001; Gomes et al 2012; Labeit et al 2010), has further supported the importance of both these ubiquitin ligases in the regulation of muscle atrophy

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Results

Conclusion