Expression of iron-regulators in the bone tissue of rats with and without iron overload.

Recently, more and more studies indicate that iron overload would cause osteopenia or osteoporosis. However, the molecular mechanism of it remains unclear. Moreover, very little is known about the iron metabolism in bone tissue at present. Therefore, the mRNA expression of iron-regulators, transferrin receptor1 (Tfr1), divalent metal transporter1 (Dmt1 + IRE and Dmt1 - IRE), ferritin (FtH and FtL), and ferroportin1 (Ireg1), and the localization of ferroportin1 protein were examined in the bone tissue of rats. In addition, the mRNA expression of each gene was compared between groups of rats with and without iron overload. The results showed that ferroportin1 protein was localized in the cytoplasm of osteoblast, osteocyte, chondrocyte and osteoclast of rats' femur. The six iron-regulatory genes, Tfr1, ferritin (FtH and FtL), (Dmt1 + IRE and Dmt1 - IRE) and ferroportin1 (Ireg1), were found in femurs of rats. In addition, significantly up-regulated expression of FtH and FtL mRNA, and markedly down-regulated expression of Tfr1, Dmt1 + IRE and Ireg1 mRNA, were observed in the iron overload group compared with the control group. The result indicates that ferroportin1 protein is localized in the cytoplasm of bone cells of rats. Tfr1, Dmt1, ferritin and ferroportin1 exist in bone tissue of rats, and they may be involved in the pathological process of iron overload-induced bone lesion.