Hierarchically reinforced injectable chitosan-based hydrogels integrating mechanical-bioactive nanofibers and chondrogenic cues for articular cartilage reconstruction

Articular cartilage defects represent a persistent clinical challenge in orthopedics. Articular cartilage, the load-bearing tissue of diarthrodial joints, possesses a hierarchically organized extracellular matrix (ECM) dominated by type II collagen and aggrecan, yet its avascular, aneural nature and low cellularity severely limit intrinsic repair capacity. Left untreated, such defects often progress to post-traumatic osteoarthritis. Despite significant advancements in tissue engineering for osteochondral regeneration, the hierarchical complexity and biomechanical demands of articular cartilage remain critical challenges. To address these limitations, we developed an injectable nanocomposite hydrogel by incorporating 2 % silk fibroin nanofibers and glucosamine into a thiolated chitosan matrix, enabling in situ gelation. The system achieved a 100.3 % increase in compressive strength over pristine chitosan hydrogel, alongside enhanced bioactivity: 26.2 % greater cellular proliferation, 150 % improved migration, and elevated chondrogenic differentiation. In a rat osteochondral defect model, the hydrogel promoted seamless tissue integration, articular surface restoration, and significant upregulation of cartilage-specific markers (COL-II, SOX-9). Collectively, this study presents a potentially translatable strategy that aims to address the longstanding trade-off between mechanical stability and bioactivity in cartilage repair.