In vitro models of skeletal muscle are critically needed to elucidate disease mechanisms, identify therapeutic targets, and test drugs pre-clinically. However, culturing skeletal muscle has been challenging due to myotube delamination from synthetic culture substrates approximately one week after initiating differentiation from myoblasts. In this study, we successfully maintained aligned skeletal myotubes differentiated from C2C12 mouse skeletal myoblasts for three weeks by utilizing micromolded (μmolded) gelatin hydrogels as culture substrates, which we thoroughly characterized using atomic force microscopy (AFM). Compared to polydimethylsiloxane (PDMS) microcontact printed (μprinted) with fibronectin (FN), cell adhesion on gelatin hydrogel constructs was significantly higher one week and three weeks after initiating differentiation. Delamination from FN-μprinted PDMS precluded robust detection of myotubes. Compared to a softer blend of PDMS μprinted with FN, myogenic index, myotube width, and myotube length on μmolded gelatin hydrogels was similar one week after initiating differentiation. However, three weeks after initiating differentiation, these parameters were significantly higher on μmolded gelatin hydrogels compared to FN-μprinted soft PDMS constructs. Similar results were observed on isotropic versions of each substrate, suggesting that these findings are independent of substrate patterning. Our platform enables novel studies into skeletal muscle development and disease and chronic drug testing in vitro.

Cultured skeletal myotubes are a powerful in vitro system for identifying mechanisms of skeletal muscle development and disease. However, skeletal myotubes routinely delaminate from conventional culture substrates after approximately 1 week, which significantly hampers their utility for in vitro disease modeling and drug screening. To address this problem, we fabricated micromolded gelatin hydrogels as culture substrates that are more biomimetic than conventional substrates. On micromolded gelatin hydrogels, C2C12 skeletal myoblasts align and differentiate into skeletal myotubes that are stable in culture for multiple weeks. With this protocol, we detail three key steps: (1) Fabrication of micromolded gelatin hydrogels; (2) Culture of mouse C2C12 myoblasts and differentiation into myotubes; and (3) Quantification of myotube morphology. These substrates have many applications for skeletal muscle disease modeling and drug screening over longer time scales.