Costal Versus Articular Chondrocytes in Alginate Three-Dimensional Cultures

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Given the difficulties in accessing articular cartilage as a source of chondrocytes to be used in fabricating cartilage constructs, alternative sources are required. The present study examined chondrocytes from costal cartilage for their suitability in cartilage tissue engineering. Chondrocytes isolated from rat knee and rib hyaline cartilage were separately mixed with alginate and placed in a calcium chloride solution as two mm beads. The beads were incubated over 2 months, during which time the structural features, proliferation rates, and gene expression levels were determined by microscopy, [3-(A, 5-dimethylthiazol-2-yl)-1, 5-diphenyl tetrazulium bromide] (MTT) assay, and real-time PCR analysis, respectively. The majority of both articular and costal chondrocytes were observed to be organelle-rich round to oval cells embedded in lacuna-like cavities within the alginate beads. The propagation patterns of both cell types were similar, undergoing proliferation during the first 40 days and almost ceasing propagation over the remaining 20 days of the culture period. The levels of aggrecan and type II collagen (cartilage specific) gene expression in costal and articular chondrocyte cultures were comparable; expression levels were very low during the initial days of culturing but were significantly upregulated by study termination (day 60). Interestingly, in contrast to cultured articular cells, the level of collagen I expression was negligible in costal cultures (p<0.05). Collectively, these data suggest that the costal chondrocytes could provide a beneficial and more accessible source of chondrocytes for three dimensional (3D) cartilage constructs.