Collagen Type II-Based Injectable Materials for In situ Repair and Regeneration of Articular Cartilage Defect.

Repairing and regenerating articular cartilage defects (ACDs) have long been challenging for physicians and scientists. The rise of injectable materials provides a novel strategy for minimally invasive surgery to repair ACDs. In this study, we successfully developed injectable materials based on collagen type II, achieving hyaline cartilage repair and regeneration of ACDs. Analysis was conducted on the regenerated cartilage after materials injection. The histology staining demonstrated complete healing of the ACDs with the attainment of a hyaline cartilage phenotype. The biochemical and biomechanical properties are similar to the adjacent native cartilage without noticeable adverse effects on the subchondral bone. Further transcriptome analysis found that compared with the Native cartilage adjacent to the defect area, the Regenerated cartilage in the defect area repaired with type II collagen-based injection materials showed changes in cartilage-related pathways, as well as down-regulation of T cell receptor signaling pathways and interleukin-17 signaling pathways, which changed the immune microenvironment of the ACD area. Overall, these findings offer a promising injectable approach to treating ACDs, providing a potential solution to the challenges associated with achieving hyaline cartilage in situ repair and regeneration while minimizing damage to the surrounding cartilage.