Quantification of gene expression with qPCR. Gene expression level of (A) COL1A1, (B) COL2A1, (C) COL3A1 and (D) COL10A1 were determined in mono-, co- and tricultures at day 7 (blank bars) and day 28 (bars with pattern) using plasmid standard curves. ASC (light grey bars), BMSC (white bars), mixed cultures (BMSC and chondrocytes in a ratio of 1:1, dark grey bars) and chondrocytes (black bars) were kept as monocultures (dotted lines at 100%) or as co- and tricultures (FB) with NB or OAB explants in chondrogenic medium. Due to high interexperimental variability we have calculated the raw data as a percentage of highest cDNA copy number per individual experiment and to 100% of monocultured controls. Stars (*) indicate significant differences between mono- and cocultures, hash signs (#) indicate significant differences between NB and OAB cocultures. Results are mean with standard deviation (SD). N =5; *P <0.05, **P <0.01, ***P <0.001. ASC, adipose-derived stem cells; BMSC, bone marrow-derived mesenchymal stem cells; FB, fibrin gel-embedded co- and tricultures together with subchondral bone explants; NB, normal subchondral bone; OAB, osteoarthritic subchondral bone.