Cartilage matrix-inspired engineered organoid precursors using digital light processing 3D bioprinting for articular cartilage regeneration

Articular cartilage injury poses a significant global public health challenge, with limited self-repair capacity often leading to fibrotic repair and insufficient integration following current clinical interventions. To overcome the limitations of existing hydrogels and precisely reconstruct a native-like microenvironment, this study aimed to develop a highly translational, matrix-inspired bioink. We formulated a novel bioink combining recombinant humanized type II collagen (RhCol II)—which resolves the scarcity and extraction difficulties of natural collagen—decellularized glycosaminoglycans (GAGs), and hyaluronic acid methacrylate (HAMA) for digital light processing (DLP) bioprinting of cartilage organoid precursors (COPs). Distinct from fully matured in vitro organoids, these COPs serve as highly inductive developmental blueprints designed to programmatically drive autonomous maturation post-printing. Quantitative in vitro analysis demonstrated that the bioink at the optimal RhCol II/GAGs ratio (7:3) exhibited excellent biocompatibility and significantly upregulated chondrogenic-specific genes (SOX9, ACAN, Col II) in human umbilical cord mesenchymal stem cells (hUCMSCs). Subcutaneous implantation in nude mice resulted in the maturation of COPs into cartilage-like tissue with typical lacunar structures and robust extracellular matrix (ECM) deposition. Crucially, in situ implantation in a rabbit articular cartilage defect model achieved superior hyaline cartilage regeneration, demonstrating enhanced biomechanical properties, favorable tissue integration, and subchondral bone preservation at 12 weeks. Transcriptomic and molecular analyses revealed that the biomimetic matrix components dynamically drove this chondrogenic differentiation by specifically activating the FOXO1/3 signaling pathway. This study provides an efficient, mechanistically defined platform for functional cartilage organoid construction via this novel COP strategy, offering promising potential applications in osteoarthritis modeling and cartilage tissue engineering research. Graphical Abstract