Cx43基因剔除小鼠心脏锥干部的异常发育

目的探讨Cx43基因缺陷小鼠心脏锥干部发育异常。方法选用胚胎（embryonic day,E）11．5d至出生后1dC57／BL6小鼠作为研究对象,根据基因型分为Cx43基因剔除纯合子（Cx43-／-）、杂合子（Cx43＋／-）及野生型（Cx43＋／＋）,采用聚合酶链反应方法鉴定基因型。免疫组化法测定横纹肌肌动蛋白α-SCA、平滑肌肌动蛋白α-SMA、神经嵴细胞的标志物AP-2α的表达;原位杂交方法检测AP-2α mRNA的表达。结果Cx43-/-出生后24h内即死亡。大体解剖见明显的右室流出道圆锥部异常膨隆。HE染色示右心室流出道壁大量异常小梁状组织增生突起,右室流出道腔明显狭窄。Cx43＋／-无明显异常。Cx43-／-近端流出道隔中央区域α-SCA的表达明显滞后。Cx43＋／-与Cx43-／-小鼠右室流出道与Cx43＋／＋比较可见比较强的α-SMA的表达,主要位于右侧锥干部的异常增生部位。Cx43-/-小鼠在E13．5流出道隔AP-2α蛋白及其mRNA水平表达均增多,且表达位置异常。结论Cx43 KO小鼠以右室流出道异常增生引起的梗阻性畸形为主要特征。Cx43 KO小鼠胚胎期近端流出道隔心肌化迟滞。Cx43 KO小鼠锥干部α-SMA的表达不能正常消退,心肌细胞发育不成熟。神经嵴细胞的发育异常可能参与了Cx43基因缺陷小鼠锥干部畸形的发病机制。

Abnormal development of conotruncal region in Cx43 knockout mice

OBJECTIVE: To explore the etiology of the conotruncal malformations in Cx43 knockout mice. METHODS: The objects were C57/BL6 mice of E11.5 to 1 day after birth by the mating of 2 month old heterozygous mice which included Cx43 (knockout, KO) homozygotes (Cx43-/-), heterozygotes (Cx43+/-) and wild-types (Cx43+/+) genotyped by PCR method. Microdissection and HE staining were used to examine the structures of hearts. The expression of the alpha-SCA, alpha-SMA, AP-2alpha were detected by immunohistochemistry. AP-2alpha mRNA was detected by in situ hybridization. RESULTS: Cx43-/- mice died within 24 h after birth with a swelling and blockage of the conotruncal region, which led to the obstruction of OFT and enlargement of right ventricle. HE staining showed plenty of abnormal tissues in this region forming many pouches. No apparent malformations were observed in Cx43+/- and Cx43+/+ mice. The expression of alpha-SCA in the proximal OFT septum was delayed obviously in Cx43-/- predominantly at E13.5 and E14.5. The expression of alpha-SMA in the OFT in Cx43+/- and Cx43-/- was stronger than that of Cx43+/+ mice, and mostly located in the hyperplastic conotruncal region especially at E13.5-E15.5 in Cx43-/- mice. The expression could still be observed at the birth day in Cx43-/- mice, which was not observed in Cx43+/+ mice. The expression of AP-2alpha and AP-2alpha mRNA at E13.5 increased in Cx43-/- and abnormally located in the proximal OFT septum. CONCLUSION: Cx43 KO mice are characterized by hyperplasia in conotruncal region. Cx43 KO mice exhibited a delayed myocardialization and the developmental immaturity of cardiomyocytes. The abnormal distribution of cardiac neural crest cells is likely to contribute to the conotruncal malformations in Cx43-deficient mice.