Semi-quantitative real-time gene expression analysis of ovine chondrocytes in three-dimensional scaffold-assisted cartilage grafts derived from 5thpassage chondrocytes. Chondrocyte dedifferentiation and re-differentiation was analyzed by gene expression analysis of the typical chondrocytic marker genes aggrecan and type IIα1 collagen. Matrix remodeling was assessed by gene expression analysis of the matrix metalloproteinases (MMP)-1, -2 and −13 as well as the tissue inhibitors of metalloproteinases (TIMP)-1, -2 and −3. The expression level was calculated as the percentage of the expression level of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The mean (n = 3 donors) is plotted and the error bars represent SD. (*) significant (p<0.05) difference compared to expression level in passage 5; (+) significant (p<0.05) difference compared to expression level in 3D grafts cultured for 1 week; (#) significant (p<0.05) difference compared to expression level in 3D grafts cultured for 2 weeks.