Regulation of FLAP mRNA expression by 1,25(OH)2D3 and TGF-β in normal and osteoarthritis osteoblasts. Confluent cells were incubated for their last 48 hours in Ham's F12/DMEM medium containing 0.5% BSA in the presence or absence of 50 nM 1,25-dihydroxyvitamin D3 (1,25(OH)2D3; D3), 10 ng/ml transforming growth factor-β (TGF-β), or both. Osteoarthritis (OA) osteoblasts were separated into low and high OA as described in the legend to Figure 1. 5-Lipoxygenase-activating protein (FLAP) expression was measured as described in the legend to Figure 2. Values are means ± SEM. Normal samples, n = 3; low and high OA, n = 4 for each group.