Bioactive Bilirubin Hydrogel Promotes Structural-Functional Skeletal Muscle Regeneration Following Volumetric Muscle Loss Through Regulating Glycolysis-Inflammation and Enhancing Muscle Innervation

The structural-functional regeneration of skeletal muscle following volumetric muscle loss (VML) remains a significant challenge owing to the dysregulated microenvironments, damaged regenerative ability, and decreased muscle innervation. Macrophages play a critical role as regulators in the process of inflammation, muscle innervation, and skeletal muscle repair. Herein, a bioactive bilirubin hydrogel (DPBD) is fabricated to promote VML regeneration by regulating macrophage intracellular glycolysis-inflammation, creating an enhanced muscle regenerative microenvironment, and improving muscle innervation. DPBD possesses excellent self-healing capability, stability, pH/reactive oxygen species (ROS) dual-responsiveness, tissue adhesion, and superior hemostatic ability. Simultaneously, DPBD displays antibacterial and antioxidant properties, which can effectively combat bacterial infections and eliminate oxidative stress. Additionally, DPBD suppresses glycolysis in macrophages by reducing phosphofructokinase activity, thereby inhibiting M1 macrophage polarization and alleviating inflammatory responses. Moreover, DPBD improves cell proliferation, endothelial cell migration, tubule formation, and myogenic differentiation, exhibiting superior biocompatibility. Importantly, DPBD accelerates skeletal muscle regeneration and motor function restoration in VML by reducing local inflammation, promoting M2 macrophages polarization, neovascularization, muscle fiber formation, mitigating fibrosis, and facilitating muscle innervation in vivo. This work indicates that bioactive bilirubin hydrogel may be a potential candidate for complete skeletal muscle regeneration after traumatic injuries.