Effects of PM treatment on osteopontin gene and protein expression. A, HUVECs from four different donors were exposed in triplicate experiments to 88 μg/ml PM for 24 h. Gene expression was examined using a PCR array. Data are mean fold changes in gene expression normalised to DMSO controls. B, 24-hour exposure to PM induced the secretion of osteopontin in a concentration dependent manner. Data are mean ± S.D. osteopontin concentrations (n = 6 in each case), as detected by electrochemiluminescence. *p < 0.05 compared to controls.