Filamented Light (FLight) Bioprinting of Mini-Muscles with Self-Renewal Potential.

The plasticity and regenerative capacity of skeletal muscle arise from quiescent stem cells activated upon overload, injury, or disease state. Developing in vitro muscle models to study these properties can advance muscle disease modeling and pre-clinical evaluation. Here, Filamented Light (FLight) bioprinting is leveraged as a high-throughput approach for producing mini-muscle tissues. Using paired box protein 7 (Pax7)-nGFP primary myoblasts, mini-muscles are bioprinted from pristine collagen-fibrinogen (ColFib). The FLight hydrogel consist of aligned microstructures which guide the formation of aligned myotubes. Mini-muscles demonstrates in vivo-like tissue organization, including multinucleated myotubes and a Pax7(+) cell pool embedded in newly deposited laminin. Both spontaneous and electrically stimulated contractions are observed. ColFib matrix is promising for maintenance of the Pax7(+) cell pool. Damage from cardiotoxin-induced injury of the mini-muscles led to a massive proliferation of Pax7(+) cells and restoration of the contractile properties of myotubes. Notably, small molecules such as Repsox can enhance regeneration. FLight printed mini-muscles have potential for applications in muscle biology, exercise/atrophy, disease models, and drug screening.