[Relationship between changes of bone mineral density and bone marrow pathology in ovariectomized rats]

This study was purposed to investigate the relationship between sequential changes of bone mineral density and bone marrow hematopoiesis in ovariectomized rats, and explore the correlation between the osteoporosis and the hematopoiesis. Fifty female Sprege-Dawley rats aged 3 months were randomly divided into ovariectomized (OVX) and sham operated (Sham) groups, euthanized after 4, 8, 12, 16 and 20 weeks respectively. The bone mineral density (BMD) of left femur was measured. The right femur distal metaphysical cancellous bone was fixed in 10% formalin to observe the changes of the bone marrow pathology. The function of hematopoietic stem cells (HSC) was evaluated by colony forming assay. The level of granulocyte macrophage-colony stimulating factor (GM-CSF) was measured by the enzyme linked immunosorbent assay (ELISA). The results showed that the BMD of femur in OVX 4 week group not decreased significantly as compared with the Sham 4 group, but the volume of adipose tissue significantly increased. The BMD of femur in OVX 8, 12, 16 and 20 weeks decreased significantly as compared with the corresponding Sham groups (P < 0.05). Meanwhile, the volume of hematopoietic tissue decreased and volume of adipose tissue increased, the megakaryocyte number decreased, the number of osteoclasts and mast cells increased in bone marrow section, as compared with sham operated group (P < 0.05). After rats were ovariectomized for 16 weeks, the GM-CSF level was significantly lower than that of Sham group. After rats were ovariectomized for 12 weeks, the GM-CSF level was obviously lower than that of Sham group (P < 0.05). It is concluded that the bone marrow hematopoiesis function also decreases when the BMD of ovariectomized rats reduces. The Sprege-Dawley OVX rats aged 3 months can be used as an model to study the hypohemopoiesis.