The mechanical strain as a cross-linking agent for skeletal muscle ECM-derived hydrogels

Our research focuses on utilising decellularised extracellular matrix (ECM)-derived hydrogels to develop implants for repairing skeletal muscle defects. We investigate whether applying mechanical stimuli during the hydrogel reticulation phase enhances its biomechanical properties, aiming to achieve surface stiffness values closer to those of physiological tissue compared to conventional chemical cross-linking methods. The ECM-derived hydrogel is prepared and characterised in terms of surface stiffness and gelation kinetics. Before polymerisation, the ECM-derived solution is embedded with myogenic cells, and the final constructs are then obtained through a temperature-induced self-assembling mechanism. Two different modifications are alternatively added: genipin, a natural cross-linker, and a nearly-uniaxial mechanical strain using an in-house developed bioreactor. Both modifications of the ECM-derived hydrogel result in a two-fold increase in surface stiffness compared to the self-assembled samples. However, only the mechanical stimulus promotes the alignment of ECM components, which may facilitate the subsequent orientation of skeletal muscle cells and leads to a significant increase in cell proliferation after 5 days of culture. These findings indicate that mechanical stimulation functions as a physical cross-linker, positively affecting both the biomechanical properties of ECM-derived hydrogels and the subsequent behaviour of incorporated cells.