Chondrogenic medium in combination with a c-Jun N-terminal kinase inhibitor mediates engineered cartilage regeneration by regulating matrix metabolism and cell proliferation

Cartilage tissue engineering is a promising strategy for repairing cartilage defects. However, achieving satisfactory cartilage regeneration in vitro and maintaining its stability in vivo remains a challenge. The key to achieving this goal is establishing an efficient cartilage regeneration culture system to retain sufficient active cells with physiological functions, generate abundant cartilage extracellular matrix (ECM) and maintain a low level of cartilage ECM degradation. The current chondrogenic medium (CM) can effectively promote cartilage ECM production; however, it has a negative effect on cell proliferation. Meanwhile, the specific c-Jun N-terminal kinase pathway inhibitor SP600125 promotes chondrocyte proliferation but inhibits ECM synthesis. Here, we aimed to construct a three-dimensional cartilage regeneration model using a polyglycolic acid/polylactic acid scaffold in combination with chondrocytes to investigate the effect of different culture modes with CM and SP600125 on in vitro cartilage regeneration and their long-term outcomes in vivo systematically. Our results demonstrate that the long-term combination of CM and SP600125 made up for each other and maximized their respective advantages to obtain optimal cartilage regeneration in vitro. Moreover, the long-term combination achieved stable cartilage regeneration after implantation in vivo with a relatively low initial cell-seeding concentration. Therefore, the long-term combination of CM and SP600125 enhanced in vitro and in vivo cartilage regeneration stability with fewer initial seeding cells and thus optimized the cartilage regeneration culture system.