FGF-2-expanded costal chondrocytes regenerate hyaline cartilage in rabbit osteochondral defects

In this study, we evaluated the potential usefulness of FGF-2-expanded costal chondrocytes (CCs) for the repair of osteochondral defect in articular cartilage. Rabbit CCs were expanded approximately 10⁷ folds up to passage 8 in the FGF-2 supplemented medium and became fully dedifferentiated. Their capacity to redifferentiate to hyaline cartilage was tested by in vitro 3D culture in the collagen scaffold and in vivo transplantation in the osteochondral defect of the rabbit knee. Those fully dedifferentiated CCs, which were seeded to collagen scaffold were successfully redifferentiated to hyaline cartilage under the chondrocyte differentiation condition for two weeks, which was featured by lacunae formation and glycosaminoglycan expression. After transplantation to the full thickness defect of the rabbit knee, both dedifferentiated CCs and redifferentiated CCs in the collagen scaffold successfully repaired the cartilage defect. The repaired tissue was confirmed to be hyaline cartilage by re-expressions of type II collagen, GAG, and aggrecan as well as histological grading scale. In conclusion, FGF-2 expanded CCs were fully dedifferentiated but retain their inherent capacity to redifferentiate to hyaline cartilage.