Abstract

While it is well understood that muscle tissue generates contractile forces, it is less appreciated that muscle also dynamically responds to applied forces during development as well as in regular motion. We previously fabricated tissue engineered muscle comprising skeletal myocytes in co-culture with spinal motor neurons on aligned nanofiber poly-caprolactone scaffolding, demonstrating that innervation elicited more robust myofibers and formation of neuromuscular junctions. The current study utilized custom mechanobioreactors to apply tensile elongation to this engineered muscle platform to explore the effects of exogenous forces and scaffold topology on innervated versus non-innervated myocytes. We found that nanofiber scaffold alignment played a significant role in myocyte thickness, width, and fusion under both innervated and non-innervated conditions. We observed that a combination of tensile loading and nanofiber alignment increased myocyte fusion, suggesting these parameters work together to expedite and enhance myofiber formation and maturation. Overall, this multi-faceted paradigm featuring biomechanical loading, substrate topology, and innervation mimics key features of the developmental microenvironment experienced by myocytes in vivo. Future work may further apply this biofidelic paradigm to study muscle development, function, and responses to trauma, as well as explore the utility of fabricating large-scale engineered muscle for repair of major muscle defects.