Tensile Forces and Nanofiber Alignment Influence Both Innervated and Non-Innervated Skeletal Myofiber Formation in Custom Mechanobioreactors.

While it is understood that muscle tissue generates contractile forces, it is less appreciated that muscle dynamically responds to applied forces during development. We previously fabricated tissue engineered muscle comprised of 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. Nanofiber scaffold alignment played a significant role in myocyte thickness, width, and fusion under both innervated and non-innervated conditions. 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. These findings may facilitate more sophisticated studies on muscle development, function, and responses to trauma while also elucidating principles to support the fabrication of engineered muscle to repair major muscle defects.