Regulation of Myogenesis by MechanomiR-200c/FoxO3 Axis

Area of Science:

• Muscle biology and regenerative medicine
• Molecular mechanisms of mechanotransduction
• Epigenetic regulation of differentiation

Background:

• Cyclic mechanical stretch inhibits myoblast differentiation and promotes proliferation.
• The molecular mechanisms underlying stretch-induced inhibition of differentiation are not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanisms by which mechanical stretch inhibits myoblast differentiation.
• To identify key regulatory molecules, including microRNAs, involved in this process.

Main Methods:

• Primary mouse myoblast culture and mechanical stretch application.
• MicroRNA (miRNA) microarray analysis to profile miRNA expression.
• Overexpression and antagomir studies to assess miR-200c function.
• Western blotting and chromatin immunoprecipitation (ChIP) assays to investigate protein and DNA interactions.

Main Results:

• Mechanical stretch inhibits myoblast differentiation by promoting cell cycle progression and suppressing MyoD expression.
• miR-200c was identified as a downregulated mechanosensitive miRNA (mechanomiR) crucial for myoblast differentiation.
• Overexpression of miR-200c counteracted stretch-induced inhibition, while an antagomir restored it, indicating miR-200c mediates the effect of stretch.
• The MyoD/miR-200c/FoxO3a pathway was identified, with MyoD regulating miR-200c transcription, and FoxO3a as a downstream target.
• miR-200c levels were elevated during muscle repair in young mice but not in aged mice.

Conclusions:

• Mechanical stretch inhibits myoblast differentiation partly through the downregulation of miR-200c.
• The identified MyoD/miR-200c/FoxO3a pathway is a novel mechanism by which mechanical cues regulate muscle differentiation and potentially muscle repair.
• Dysregulation of this pathway may contribute to impaired muscle regeneration in aged individuals.