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Figure 5. Gene-expression analysis, 5 weeks after in vitro culture. Data are shown as mean CT-values ± SD of housekeeping genes (A) and average relative gene-expression of chondrogenic genes (B) . nd = not detected (ct-value > 35.00) ; hsGAPDH = human-specific GAPDH ; bsGAPDH = bovine-specific GAPDH ; hsACAN = human-specific ACAN ; bsACAN = bovine-specific ACAN ; hsCOL2A1 = human- specific COL2A1 ; h AMSC = human Adipose-tissue-derived Mesenchymal Stem Cell ( n=3 experiments with 3 independent donors) ; h BMSC = human Bone-marrow-derived Mesenchymal Stem Cell ( n=3 experiments with 3 independent donors) ; b AC = bovine Articular Chondrocyte ( n=3 experiments with 3 pools of donors). Per experiment, 3 samples were used for analyses. Based on previous results, we further wanted to evaluate signs of hypertrophy in these constructs, since hypertrophic differentiation is an unwanted phenomenon in cartilage regeneration. b ACs cultured in ‘basic medium’ expressed hardly any COL10 after 3 weeks of culture. In addition, when b ACs were exposed to paracrine factors of h MSC either via Transwell® system or h MSC-conditioned medium, COL10 -gene-expression was upregulated and significantly increased in constructs exposed to paracrine factors of h AMSCs (Transwell® system p =0.004 ; h AMSC-conditioned medium p =0.028). Although COL10 -gene-expression was slightly upregulated in constructs exposed to paracrine factors of h BMSC, no significant 99 AMSCs OR BMSCs FULFILL A TROPHIC ROLE IN CO-CULTURE 5