Stem cell based tissue engineering for meniscus repair

Defects of the meniscus greatly alter knee function and predispose the joint to degenerative changes. The purpose of this study was to test a recently developed cell-scaffold combination for the repair of a critical-size defect of the rabbit medial meniscus. A bilateral, complete resection of the pars intermedia of the medial meniscus was performed in 18 New Zealand White rabbits. A hyaluronan/gelatin composite scaffold was implanted into the defect of one knee of 6 rabbits and the contralateral defect was left untreated. Scaffolds loaded with autologous marrow-derived mesenchymal stem cells and cultured in a chondrogenic medium for 14 days were implanted in a second series of 12 rabbits. Empty scaffolds were implanted in the contralateral knees. Meniscii were harvested at 12 weeks. Untreated defects had a muted fibrous healing response. Defects treated with cell-free implants showed also predominantly fibrous tissue whereas fibrocartilage was present in some scaffolds. The cross-sectional width of the repair tissue after treatment with cell-free scaffolds was significantly greater than controls (p < 0.05). Pre-cultured implants integrated with the host tissue and 8 of 11 contained meniscus-like fibrocartilage, compared with 2 of 11 controls (p < 0.03). The mean cross-sectional width of the pre-cultured implant repair tissue was greater than controls (p < 0.004). This study demonstrates the repair of a critical size meniscal defect with a stem cell and scaffold based tissue engineering approach.