Chondrogenesis of adipose-derived stem cells following adenoviral-mediated gene transfer. Monolayer cultures of adipose-derived stem cells (ASCs) were transduced with 100 multiplicity of infections of Ad.IGF-1, Ad.TGF-β1, Ad.FGF-2 and Ad.SOX9 single or in combination; following aggregate formation, the aggregates were cultured for 28 days and harvested at 14 and 28 days. Non-transduced positive and negative control ASCs were cultured in parallel. Safranine-O and Toluidine blue stainings were used for the detection of matrix proteoglycan in representative aggregate sections, and immunostaining was used for the presence of collagens; predominant collagen (COL) II indicates a chondrocyte-like phenotype, predominant COL I indicates a fibrous matrix, and predominant COL × indicates hypertrophic chondrocytes undergoing terminal differentiation. Negative control for the stainings corresponds to ASCs cultured in incomplete chondrogenic medium. All 100 × magnification, bar = 200 µm. 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.