Morphological alterations in the growth plate cartilage of ovariectomized mice.

The effects of ovariectomy on growth and estrogen receptor (ER) expression level in the epiphyseal growth plate in mice have been estimated by histomorphometry and immunohistochemistry. Twelve female ddY mice, 8-9 weeks of age, were subjected to bilateral ovariectomy and 12 others were sham operated. They were then killed 8 weeks later. Ovariectomy significantly increased the total thickness of the distal femoral and proximal tibial growth plate cartilage. Ovariectomy caused a 1.4-fold increase in the thickness of the proliferative layer in the distal growth plate of the femur and a 1.3-fold increase in the thickness of the proliferative layer in the proximal growth plate of the tibia. ERalpha and ERbeta immunoreactivity was detected in chondrocytes of the growth plate and the expression level of ERs in epiphyseal plates was increased in ovariectomized mice compared with controls. These data suggest that ERalpha and ERbeta are coexpressed in the growth plates of the mice and that the cartilage growth and the level of expression of ERs in these tissues are hormonally regulated.