T. Ikeda et al., OSTEOPONTIN MESSENGER-RNA IS EXPRESSED BY SMOOTH MUSCLE-DERIVED FOAM CELLS IN HUMAN ATHEROSCLEROTIC LESIONS OF THE AORTA, The Journal of clinical investigation, 92(6), 1993, pp. 2814-2820
Osteopontin is a phosphorylated, sialic acid-rich, noncollagenous bone
matrix protein containing the Arg-Gly-Asp-Ser amino acid sequence res
ponsible for cell adhesion. The protein strongly binds to hydroxyapati
te and play an important role in calcification. Expression of osteopon
tin mRNA was analyzed in human aortic atherosclerotic lesion by Northe
rn blot hybridization, as well as by in situ hybridization. The expres
sion of osteopontin mRNA was detected in 24 out of 25 samples of aorta
obtained from 17 autopsy cases, but not in one normal aortic sample.
The magnitude of expression was proportional to the stage of atheroscl
erosis. In situ hybridization revealed that the cells expressing osteo
pontin mRNA were detected in the wall surrounding atheroma and closely
associated with calcification. They were morphologically identified a
s foam cells and immunohistologically positive with HHF35, appearing t
o be derived from smooth muscle cells. These findings have suggested t
hat smooth muscle cell-derived foam cells express osteopontin mRNA and
play an important role in calcification of the atherosclerotic lesion
s.