Objective: Osteopontin (OPN), a noncollagenous adhesive protein, is implicated in atherosclerosis, in which macrophages within atherosclerotic plaques express OPN. However, it is not known whether the elevated OPN expression is a cause or result of atherosclerosis.
Methods and results: We generated mice that lacked OPN and crossed them with apolipoprotein (apo) E-deficient mice and analyzed these mice with a mixed C57BL/6x129 background after 36 weeks on a normal chow diet. In female mice, OP+/-E-/- and OP-/-E-/- mice had significantly smaller atherosclerotic and inflammatory lesions compared with OP+/+E-/- mice, and that was reflected by smaller area of MOMA-2-positive staining. In male mice, however, there was no significant difference in the atherosclerosis lesion areas among 3 genotypes. In both OP-/-E-/- and OP+/+E-/- mice, typical atherosclerotic lesions were detected, which include necrotic core, foamy cell collections, and cholesterol clefts. However, we found that vascular mineral-deposited areas in 60-week-old male OP-/-E-/- mice were significantly increased compared with those in OP+/+E-/- male mice.
Conclusions: These results suggest that OPN plays a promoting effect in atherosclerosis and inhibitory effect in vascular calcification. The suppression of OPN expression in females should be considered a therapeutic possibility in atherosclerosis.