Expression of osteopontin messenger RNA by macrophages in ovarian serous papillary cystadenocarcinoma: A possible association with calcification of psammoma bodies

Calcified psammoma bodies often appear in human ovarian serous papillary cy stadenocarcinoma. Osteocalcin (OC), osteonectin (ON) and osteopontin (OPN) are three members of non-collagenous bone-related proteins known to be rela ted with mineralization of bone. To clarify possible involvement of these b one matrix proteins in the calcification of the psammoma bodies, the expres sion of OC, ON and OPN was analyzed by immunohistochemical and in situ hybr idization studies using 15 surgical specimens. OPN protein was detected in the calcified area of the psammoma bodies which was positively stained by v on Kossa's staining, while OC and ON proteins were not. OPN protein was not detected in any cells in tissues, but OPN messenger ribonucleic acid (mRNA ) was detected in CD68-positive macrophages, indicating that OPN was produc ed and promptly secreted by macrophages. These results suggest that OPN pro duced and promptly secreted by macrophages and subsequently translocated to psammoma bodies may be causally related with the calcium phosphate deposit ion in the psammoma bodies of the ovarian serous papillary cystadenocarcino mas.