Integrated 3D printing of topologically hierarchical mechanical hydrogel for accelerating osteochondral regeneration.

Abstract

Osteochondral defects present a formidable clinical challenge due to the intricate structural and functional interdependence of cartilage and subchondral bone. Conventional scaffolds, characterized by single-scale, disconnected pores, inherently restrict cell-cell communication and nutrient diffusion, thereby impeding osteoblast-to-osteocyte transformation and matrix mineralization. Herein, a 3D-printed topologically hierarchical mechanical hydrogel (THMH) scaffold was developed featuring a biomimetic bilayer architecture that recapitulates the native osteochondral microenvironment. THMH integrates a nanoporous cartilage-mimetic layer and a macroporous osteogenic layer, interconnected via gradient pores to facilitate nutrient transport, vascularization, and cellular crosstalk. <i>In vitro</i> evaluations revealed that the THMH has excellent biocompatibility and the ability to promote multidirectional differentiation of BMSCs. RNA-seq results indicated that cartilage-like layer of THMH may promote the chondrogenic differentiation of BMSCs by its mechanical properties and KGN to activate integrin-PI3K-AKT signaling axis. Osteogenic layer of THMH may promote the osteogenic differentiation of BMSCs due to its hierarchically porous structure for improving the internal hypoxic environment. <i>In vivo</i> implantation in a rat osteochondral defect model achieving near-complete osteochondral regeneration. This study establishes THMH as a multifunctional platform that bridges biomechanical robustness with biofunction fidelity, offering a transformative paradigm for addressing complex osteochondral regeneration challenges.