Biomechanical strain vehicles for fibroblast-directed skeletal myoblast differentiation and myotube functionality in a novel coculture

Michael R. Hicks, Thanh V. Cao, Paul R. Standley

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Skeletal muscle functionality is governed by multiple stimuli, including cytokines and biomechanical strain. Fibroblasts embedded within muscle connective tissue respond to biomechanical strain by secreting cytokines that induce myoblast differentiation and, we hypothesize, regulate myotube function. A coculture was established to allow cross talk between fibroblasts in Bioflex wells and myoblasts on nondeformable coverslips situated above Bioflex wells. Cyclic short-duration strain (CSDS) modeling repetitive stress/injury, acyclic long-duration strain (ALDS) modeling manipulative therapy, and combined strain paradigms (CSDS + ALDS) were applied to fibroblasts. Nonstrained myoblasts in uniculture and coculture served as controls. After fibroblasts had induced myoblast differentiation, myotube contraction was assessed by perfusion of ACh (10−11–10−3 M). CSDS-treated fibroblasts increased myotube contractile sensitivity vs. uniculture (P< 0.05). As contraction is dependent on ACh binding, expression and clustering of nicotinic ACh receptors (nAChRs) were measured. CSDS-treated fibroblasts increased nAChR expression (P < 0.05), which correlated with myotube contraction. ALDS-treated fibroblasts did not significantly affect contraction or nAChR expression. Agrin-treated myotubes were then used to design a computer algorithm to identify α-bungarotoxin-stained nAChR clusters. ALDS-treated fibroblasts increased nAChR clustering (P < 0.05), while CSDS-treated fibroblasts disrupted cluster formation. CSDS-treated fibroblasts produced nAChRs preferentially located in nonclustered regions (P < 0.05). Strain-activated fibroblasts mediate myotube differentiation with multiple functional phenotypes. Similar to muscle injury, CSDS-treated fibroblasts disrupted nAChR clusters and hypersensitized myotube contraction, while ALDS-treated fibroblasts aggregated nAChRs in large clusters, which may have important clinical implications. Cellular strategies aimed at improving muscle functionality, such as through biomechanical strain vehicles that activate fibroblasts to stabilize postsynaptic nAChRs on nearby skeletal muscle, may serve as novel targets in neuromuscular disorders.

Original languageEnglish (US)
Pages (from-to)C671-C683
JournalAmerican Journal of Physiology - Cell Physiology
Volume307
Issue number8
DOIs
StatePublished - Oct 15 2014

Keywords

  • Biomechanical strain
  • Contraction
  • Cytokines
  • Fibroblasts
  • Nicotinic acetylcholine receptors
  • Skeletal muscle

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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