Proliferation of tartrate-resistant acid phosphatase positive multinucleate cells in ovariectomized animals.

In order to explore why ovarian hormone deficiency causes excessive osteoclastic bone resorption that results in osteoporosis in a large number of postmenopausal women, bone marrow cells from ovariectomized and sham-operated female mice were cultured for 8 days. The cells gave rise in culture to tartrate-resistant acid phosphatase-positive multinucleate cells. The formation of these osteoclast-like cells was enhanced by parathyroid hormone and 1,25(OH)2vitamin D3, with the latter being more effective. Cultures of cells from ovariectomized animals formed significantly more tartrate-resistant acid phosphatase-positive multinucleate cells than those from sham-operated controls. These findings support the hypothesis that ovarian hormone deficiency promotes the expansion of a pool of marrow-derived progenitor cells that differentiate into bone-resorbing osteoclasts under the influence of osteotropic hormones.