Influence of estrogen and progesterone on matrix-induced endochondral bone formation

Summary The influence of estradiol and progesterone, alone or in combination, on the discrete phases of matrix-induced endochondral bone formation was investigated. Administration of estradiol and progesterone in combination increased mesenchymal cell proliferation, as indicated by [³H] thymidine incorporaton into acid precipitable material. However, ornithine decarboxylase (ODC) activity was significantly suppressed by the combination of estradiol and progesterone. Also, this treatment did not influence the³⁵SO₄ incorporation into proteoglycans on day 7. Mineralization of newly induced bone was quantitated by alkaline phosphatase,⁴⁵Ca incorporation into bone mineral and calcium content, and was found to be significantly increased by progesterone alone and in combination with estradiol in both matrix-induced plaques and tibial metaphysis. These results demonstrated the stimulatory role of progesterone in combination with estradiol in bone formation and mineralization.