Protein synthesis of human articular chondrocytes cultured in vitro for autologous transplantation

Chondrocytes in hyaline cartilage produce typical matrix proteins, the most abundant of them being collagen type II and aggrecan. Chondrocytes in monolayer cell culture dedifferentiate and gain fibroblastic phenotype. The cells gradually start to produce collagen type I while the production of collagen type II and aggrecan decreases. Transplantation of autologous chondrocytes cultured in vitro is used for treatment of aseptic articular cartilage lesions. For this purpose, cartilage biopsy is taken and isolated cells are subsequently proliferated in a monolayer cell culture. When implanted, the cells start to produce specific cartilaginous matrix that fills the defect. Prior to surgical procedure the cells can also be cryopreserved for longer periods of time after reaching appropriate numbers. We tested the influence of cultivation time and number of continuous culture passages as well as the influence of cryopreservation on the matrix protein synthesis of human articular chondrocytes. The ability of dedifferentiated chondrocytes to redifferentiate has been monitored by measuring matrix protein synthesis of the cells, re-seeded in agarose suspension culture. The results obtained show progressive dedifferentiation during monolayer cell culture procedures, facilitated by cryopreservation. Successful redifferentiation of cells re-seeded in suspension cultures was observed regardless of the previous level of chondrocyte dediferentiation.