Superficial cartilage defects represent the most prevalent type of cartilage injury encountered in clinical settings, posing significant treatment challenges. Here, we fabricated a cartilage extracellular matrix mimic hydrogel (GHC, consisting of Gelatin, Hyaluronic acid, and Chondroitin sulfate) to avoid the exacerbation of cartilage deterioration, which is often driven by the accumulation of reactive oxygen species (ROS) and a pro-inflammatory microenvironment. The GHC hydrogel exhibited multifunctional properties, including in situ formation, tissue adhesiveness, anti-ROS capabilities, and the promotion of chondrogenesis. The enhancement of tissue adhesion was achieved by chemically modifying hyaluronic acid and chondroitin sulfate with o-nitrobenzene, enabling a covalent connection to the cartilage surface upon light irradiation. In vitro characterization revealed that GHC hydrogel facilitated chondrocyte adhesion, migration, and differentiation into cartilage. Additionally, GHC hydrogels demonstrated the ability to scavenge ROS in vitro and inhibit the production of inflammatory factors by chondrocytes. In the animal model of superficial cartilage injury, the hydrogel effectively promoted cartilage ECM regeneration and facilitated the interface integration between the host tissue and the material. These findings suggest that the multifunctional GHC hydrogels hold considerable promise as a strategy for cartilage defect repair. STATEMENT OF SIGNIFICANCE: : Superficial cartilage defects represent the most prevalent type of cartilage injury encountered in the clinic. Previous cartilage tissue engineering materials are only suitable for full-thickness cartilage defects or osteochondral defects. Here, we developed a multifunctional GHC hydrogel composed of gelatin, hyaluronic acid, and chondroitin sulfate, which are natural cartilage extracellular matrix components. The drug-free and cell-free hydrogel not only avoids immune rejection and drug toxicity, but also shows good mechanical properties and biocompatibility. More importantly, the GHC hydrogel could adhere tightly to the superficial cartilage defects and promote cartilage regeneration while protecting against oxidation. This natural ingredients and multifunctional hydrogel is a potential material for repairing superficial cartilage defects.

Osteoarthritis (OA) affects nearly 500 million people worldwide and is characterized by an irreversible loss of glycosaminoglycans (GAGs) at articular cartilage surfaces, which are essential in maintaining cartilage mechanical properties and chondrocyte phenotypes. Despite advances, preserving cartilage GAGs and controlling their turnover in living cells remain challenging. On the basis of the hypothesis that GAGs can interact with cationic molecules, we demonstrated a cost-effective strategy to increase human cartilage GAGs using a cationic polymer hexadimethrine bromide (HDMBr). HDMBr promoted chondrogenesis of mesenchymal stem cells by attracting pericellular GAGs and up-regulating vesicle formation, leading to increased matrix secretion. HDMBr also acted like a molecular assembler to promote the assembly of chondroitin sulfate (CS) into highly concentrated condensates during intracellular trafficking, resulting in more efficient GAG secretion. HDMBr was then evaluated as a potential therapeutic in two animal models. In a rabbit model of large cartilage defects, HDMBr promoted the intrinsic regeneration of GAG-rich hyaline-like cartilage and improved tissue integration. In a rat model of OA, low-dose HDMBr treatment increased cartilage thickness, supported cartilage matrix homeostasis, and supported cell-based therapy, reducing OA damage as compared with other tested clinical treatments. Overall, this study introduces a cost-effective GAG manipulation approach to cartilage repair and joint preservation, offering insights into the mechanisms of cell-material interactions.