Cartilage Regeneration Units Based on Hydrogel Microcarriers for Injectable Cartilage Regeneration in an Autologous Goat Model

Despite numerous studies on tissue-engineered injectable cartilage, it is still difficult to realize stable cartilage formation in preclinical large animal models because of suboptimal biocompatibility, which hinders further application in clinical settings. In this study, we proposed a novel concept of cartilage regeneration units (CRUs) based on hydrogel microcarriers for injectable cartilage regeneration in goats. To achieve this goal, hyaluronic acid (HA) was chosen as the microparticle to integrate gelatin (GT) chemical modification and a freeze-drying technology to create biocompatible and biodegradable HA-GT microcarriers with suitable mechanical strength, uniform particle size, a high swelling ratio, and cell adhesive ability. CRUs were then prepared by seeding goat autologous chondrocytes on the HA-GT microcarriers and culturing in vitro. Compared with traditional injectable cartilage methods, the proposed method forms relatively mature cartilage microtissue in vitro and improves the utilization rate of the culture space to facilitate nutrient exchange, which is necessary for mature and stable cartilage regeneration. Finally, these precultured CRUs were used to successfully regenerate mature cartilage in nude mice and in the nasal dorsum of autologous goats for cartilage filling. This study provides support for the future clinical application of injectable cartilage.