Gene expression pattern induced by transforming growth factor beta 1 under Sp1 ectopic expression. Human articular chondrocytes (HAC) were nucleofected with pEVR2 or pEVR2-Sp1. Thereafter, the media were replaced with DMEM + 2% FCS for 24 hours before adding transforming growth factor beta 1 (TGFβ1) (5 ng/ml) for an additional 24 hours of incubation. Total RNA was then extracted and real-time RT-PCR analysis was performed. Histograms represent the relative COL1A1, COL2A1, COL10A1, aggrecan or Sox9 mRNA levels versus GAPDH.