Gene expression in genetically modified adipose-derived stem cells aggregate cultures. Adipose-derived stem cells (ASCs) were transduced with 100 multiplicity of infections of respective adenoviral vectors as indicated, cultured into aggregates, and maintained in a defined serum-free medium for 3, 7, 14, 21 or 28 days. For each treatment group and time point indicated, RNA was extracted from three aggregates, and both expression of (A) tranduced genes (3, 7, 14, 21 and 28 days) and (B,C,D,E,F,G,H) the cartilage-specific marker genes aggrecan (AGC), biglycan (BGC), cartilage matrix (CM), and proteoglycan (PGC), collagen (COL) I, COL II, COL X, (3, 14, and 28 days) were determined by quantitative real time (qRT)-PCR. RNA isolated from ASCs differentiated by a commercial established medium and RNA extracted immediately from ASCs newly transduced (time 0) were used as comparative controls. The primer sequences, product sizes, and annealing temperatures for qRT-PCR are listed in Additional file 1. The expression level of each targeted gene was normalized to the housekeeping gene GAPDH. Values are expressed as the fold induction of means ± standard deviations of normalized expression levels. Statistical differences between groups and positive control were analyzed using a t test; *differences were considered significant when P <0.05. FGF-2, fibroblast growth factor-2; IGF-1, insulin-like growth factor-1; SOX9, sex-determining region Y-box 9; TGFβ, transforming growth factor beta.