L-leucine-incorporated 3D-printed SilMA hydrogel scaffolds promote calvarial defect repair with PLOD2-associated...

Effective repair of bone defects requires scaffolds that not only match defect geometry and provide mechanical support, but also support both osteogenic and angiogenic processes during regeneration. Here, a photocurable hydrogel ink integrating methacrylated silk fibroin (SilMA) with L-leucine (L-Leu) is developed for 3D printing of architected scaffolds with programmable pore structures. L-Leu incorporation enhances the compressive performance and surface wettability of the hydrogel without compromising print fidelity, thereby improving the interfacial microenvironment for cell attachment and tissue remodeling. In vitro, SilMA@L-Leu exhibits good cytocompatibility, promotes bone marrow-derived mesenchymal stem cell proliferation and osteogenic differentiation, and enhances the angiogenic activity of human umbilical vein endothelial cells. Among the tested formulations, SilMA@L-Leu containing 300 ng mL^-1 L-Leu showed the most balanced osteogenic and angiogenic performance and was therefore selected for mechanistic and in vivo evaluation. In a rat critical-size calvarial defect model, this scaffold markedly promotes new bone formation, collagen deposition, and mineralized tissue development. Mechanistically, siRNA-mediated silencing of procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2) attenuated the scaffold-induced osteogenic effects, suggesting the involvement of PLOD2-associated collagen matrix remodeling in the pro-osteogenic activity of SilMA@L-Leu. These findings identify SilMA@L-Leu as a 3D-printable, small-molecule-incorporated scaffold with promise for bone defect repair.