| Postmenopausal osteoporosis is a heterogeneous disorder characterized by accelerated bone loss after natural or surgical menopause and an increased risk of fractures. The epithelial Ca2+ channel TRPV5/TRPV6 performance to have sensitive selectivity to the calcium ion, thus it has the very important effect on the calcium ion metabolizes and the bone metabolism. The previous study showed TRPV5 was mainly exist in kidney, the TRPV6 was mainly exist in small intestines. TRPV5/TRPV6 has been tested in the osteoblast of bone tissue. The foreign research has already proven to make exchange the calcium ion to keep the extracellular level of calcium. Our experimental term have observed the expression of TRPV5 and TRPV6 in osteoblasts which come from the differentiation of BMSCs. The study on the expression of TRPV5 and TRPV6 in the cultured neonatal rat calvarial osteoblasts and the role of the expression of TRPV5 and TRPV6 in mechanism of post-menopausal osteoporosis has not yet been reported. The present study mainly observed the the expression of TRPV5 and TRPV6 in neonatal rat calvarial osteoblasts and the role of the expression of TRPV5 and TRPV6 in mechanism of post-menopausal osteoporosis. The bone loss in estrogen deficiency results from the increased bone resorption and impaired ability of osteoblastic bone formation. In the other hand, the interventive measures were used to probe into the possible treatment of estrogen and 1,25(OH)2VD3 to post-menopausal osteoporosis.The first section is to study the possible mechanism of estrogen and 1,25 (OH)2VD3 treatment to post-menopausal osteoporosis in vivo experiment. The osteoporosis model was copied by resecting the rat ovarian. Rats of ovariectomy were treated with estrogen or 1,25(OH)2VD3 for anti-osteoporosis for 8 weeks. Rats were sacrificed to detect bone density, bone histomorphometry, and some serum bone metabolic index so on. The RT-PCR technique was used to detected the mRNA expression of OPG, RANKL, M-CSF and TRPV6 in bone of rats of ovariectomy with/without treatment of estrogen / 1,25(OH)2VD3. The results showed, , the treatment of estrogen can protect against osteoporosis to some extent, however, the effect of 1,25(OH)2VD3 against osteoporosis wasn't significant. Meanwhile, it was showed that estrogen probably promoted the bone formation by stimulating the expression OPG, RANKL pathway and openning of Ca2+ chanel TRPV6.The second section is to study the possible mechanism of estrogen and 1,25(OH)2VD3 treatment to post-menopausal in vitro experiment. As we all known, osteoblast played the important role in the pathogenesis of osteoporosis. In the present study , the neonatal rat calvarial osteoblasts were cultured and subcultured to observed the proliferation and expression of OPG, RANKL, TRPV5 and TRPV6 after exposed to estrogen and 1,25(OH)2VD3. The cells showed the characteristic osteoblast by ALP postive staining and formation of osteoblasts nodule. It was observed that the proliferation of osteoblast activity increased companied with the increase of estrogen concentration. The mRNA and protein expression of OPG,TRPV5 and TRPV6 in osteoblast showed a dose-dependent manner. These results suggested that bone formation induced by estrogen may be mediated by the OPG/OPGL path and calcium ion content regulated by the special Ca2+ chanel TRPV5 and TRPV6. In the other hand, the action of 1,25(OH)2VD3 on osteoblasts was observed and showed that only very low concentrations of 1,25(OH)2VD3 stimulated the proliferation of osteoblasts. Whereas, 1,25(OH)2VD3 promoted the mRNA expression of OPG, TRPV5 and TRPV6 which was similar with the action of estrogen on osteoblast. These results suggested that bone formation induced by 1,25(OH)2VD3 also was mediated by the OPG/OPGL path and the special Ca2+ chanel TRPV5 and TRPV6. |
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