Decellularized extracellular matrix enhances hydrogel printability for bioprinting functional muscle constructs in a volumetric muscle loss model

Volumetric muscle loss (VML) remains a major clinical challenge due to the limited regenerative capacity of skeletal muscle. Effective repair requires the use of biomaterials that support cell viability, promote myogenic differentiation and enable vascularisation to allow the formation of structurally aligned, functional muscle. Here, we have integrated a biomimetic bioink based on gelatin methacryloyl (GelMA) and methacryloyl-modified decellularized extracellular matrix (dECM-MA) with a micropost tension-assisted bioprinting strategy to engineer skeletal muscle constructs for VML repair. We synthesized and characterized GelMA and dECM-MA bioinks, demonstrating well-preserved ECM components, reproducible gelation, mechanical properties and rheological properties suitable for extrusion bioprinting. In vitro, printed GelMA + dECM-MA scaffolds supported high cell viability, alignment and robust myogenic differentiation of C2C12 myoblasts, human satellite cells (hSkMSCs) and human umbilical vein endothelial cells (HUVECs). Co-culture of satellite cells with HUVECs enhanced endothelial network formation and improved myotube maturation. Printing around PDMS microposts provided passive mechanical tension, producing aligned fibres and greater contraction velocity and micropost displacement in co-culture constructs under electrical stimulation. To assess regenerative potential, 3-day-matured constructs were implanted in a mouse VML model. Constructs containing both hSkMSCs and HUVECs showed the greatest tissue regeneration, higher myofiber density, improved organization, and enhanced functional recovery compared with acellular or monoculture constructs. No immune response towards the presence of the human cells or porcine ECM was observed, suggesting a protective role for dECM-MA. Together, this integrated bioink-biomechanical platform resulted in the generation of vascularised, aligned, and functional muscle tissue with strong translational potential for VML therapy.