雌激素对骨折愈合过程中骨形态发生蛋白4 mRNA表达的影响

目的：探讨骨折愈合过程中雌激素对骨形态发生蛋白4(bone morphogenetic protein-4，BMP—4)基因表达的影响，了解BMP—4在骨折愈合过程中的作用。方法：180只雌性SD大鼠随机分成4组。OVXE1组为卵巢切除后1d开始雌激素替代治疗；OVXE2组为骨折后雌激素替代组；OVX组为雌激素缺乏组；SO组为正常对照组。所有动物在一侧胫骨中段造成骨折模型；各组动物分别在骨折后1、2、3、4、5、6、7、14、28d处死取材；标本制成石蜡切片，用地高辛标记的BMP-4 cDNA探针进行原位核酸分子杂交；实验结果经计算机图像处理系统分析并作统计学处理。结果：各组动物骨折后1—3d，骨折周围血肿及组织内BMP—4 cRMA检测为阳性，从第4d开始为阴性。OVX组的BMP—4 mRNA表达较任何一组都明显增多(P＜0．05)；SO组及OVXE1组最少。结论：BMP—4主要在骨折愈合早期起作用。雌激素对BMP-4基因的表达有抑制作用，将BMP—4基因的表达控制在一定程度内可能是雌激素调节骨折愈合的一种方式。

Effect of Estrogen on Bone Morphogenetic Protein- 4 mRNA Expression during Fracture Healing

Objective:To investigate the effect of estrogen on the expression of bone morphogenetic protein-4(BMP-4) mRNA and understand the function of BMP-4 during fracture healing.Methods:One-hundred and eighty female Sprague-Dawley rats were randomly divided into four groups:ovariectomized(OVX),Sham-operated(SO),ovariectomized rats with estrogen replacement after castration(OVXE1) and ovariectomized rats noestrogen treating in a month(OVXE2).A month later,all animals undergone a surgery to establish unilateral tibia closed diaphysis fracture model.OVXE2 rats were treated with estrogen following fracture.The rats in four groups were euthanized at each of the following points:1,2,3,4,5,6,7,14 and 28d after fracture and the callus with nearby soft tissue were taken off.The specimens were cut into 8 micron paraffin sections after decalcification.The slides were in situ hybridized with Dig-11-DUTP labeled BMP-4 cDNA probe and the results were analyzed by computer system.Results:From 1 to 3d,BMP-4 mRNA was detected by in situ hybridization in hematoma and tissues around blood vessel near the fracture ends.The positive signs was not seen after 3d.The mRNA of BMP-4 in OVX rats was increased dramatically compared with any other animals( P <0.05),whereas a slight appearance of BMP-4 signal was seen in OVXE1 and SO rats.Conclusion:This study indicates that BMP-4 plays a major role in early stage of fracture repair and suggests that estrogen inhibited gene expression of BMP-4.Thus,estrogen limiting the gene expression of BMP-4 in a certain degree may be one of its roles in fracture healing.