Self-Assembly of Fibrochondrocytes and Chondrocytes for Tissue Engineering of the Knee Meniscus

Chondrocyte self-assembly in high-density scaffoldless culture has shown success in producing articular cartilage constructs, and a similar process could be applied to fibrocartilage tissue engineering. Three cell combinations were compared in self-assembly culture—100% chondrocytes, 100% meniscal fibrochondrocytes, and 50:50 co-cultures of fibrochondrocytes and chondrocytes with the goal of creating a proteoglycan, collagen I, and collagen II matrix similar to native meniscus. Two culture surfaces were also compared for self-assembly: agarose-coated wells and tissue culture plastic. After 4 weeks, the resulting self-assembled chondrocyte constructs were 10.24 ± 0.63 mm in diameter and 0.96 ± 0.14 mm thick, weighing 84.5 ± 7.2 mg. Co-culture constructs were smaller and weighed 22.5 ± 1.0 mg. In contrast, the fibrochondrocyte constructs contracted into spheres weighing 1.3 ± 0.3 mg. Immunostaining showed collagen II in the chondrocyte constructs, both collagen I and collagen II in the co-cultures, and only collagen I in the fibrochondrocyte constructs. Collagen densities for chondrocyte, co-culture, and fibrochondrocyte constructs were 41 ± 3, 38 ± 3, and 20 ± 2 μg/mg dry weight, and glycosaminoglycan densities were 230 ± 2, 80 ± 6, and 10 ± 1 μg/mg dry weight, respectively. Self-assembled co-cultures, with their mixed collagen I and II matrix and robust gross characteristics, appear promising for tissue engineering of the knee meniscus.