Localisation and expression of osteopontin following PM exposure. A, exemplar images from immunostaining studies showing the induction of osteopontin expression upon PM treatment. B, results of pixel intensity analysis of images such as those shown in A. Data are mean ± S.D. pixel intensities from 10 cells at each concentration. *p < 0.05 compared to controls. C, Western blot analysis showed the presence of osteopontin at 66 kDa, which was greater in cells treated with 48 μg/ml PM for 24 h. D, quantification of band densities showed a 25% increase in osteopontin levels following PM exposure.