The Effects Of 17 beta-Estradiol On Osseous Tissue In Ovariectomized Rats

Jang, Won Seok; Kim, Jong Ryoul; Park, Bong Soo; Sung, Iel Young

Abstract

This study was focused on the changes of mineral density and histopathologic features of osseous tissue when ovariectomized rats were administered with 17beta -Estradiol. Forty-eight rats,11 weeks of age,were divided into four groups,which are a normal control group,an ovariectomized control group, an experimental group 1 which was given 17beta -estradiol immediately after the ovariectomy and an experimental group 2 which was given 17 beta -Estradiol 3 weeks after the ovariectomy. They were sacrificed at different time intervals (1,3,4 and 8 weeks)for histopathologic observation, histo -morphometric analysis and immunohistochemistry with fibronectin and CD34 antibody. Most rats showed the increase in bone density, which was the least in the ovariectomized control group. In histopathologic features of both the mandible and the tibia, the osteoclasts in bone marrow increased in the ovariectomized control group of more than 3 weeks. In histomorphometric analysis, the osteoclasts increased in both the mandible and the tibia in length of time. In comparison of the increase of osteoclast between four groups, it decreased as following order: the ovariectomized control group,the experimental group 2 the experimental group 1, the normal control group. Especially the experimental group 1 and experimental group 2 at 4 weeks showed remarkable changes both in the mandible and in the tibia in comparision with the ovariectomized control group. In immunohistochemical analysis with fibronectin, the more week-ovariectomized control groups of both the mandible and the tibia showed weaker fibronectin expression in osteoblast and bone marrow. Among the experimental group 1 and 2,4-week group showed the strongest expression. In immunohistochemical analysis with CD34,the mandible showed generally weak expression but 8-week experimental group 1 and 2 showed relatively moderate expression in osteoblast and bone marrow. In case of the same groups of tibia,4-week group show the strongest expression. With all these results, it is assumed that 17beta -Estradiol has more effect on the development and differentiation of osteoclasts than those of osteoblasts and contributes to the initial bone formation most efficiently by inhibiting osteoclastic action and stimulating osteoblasts.