地塞米松对大鼠胎肺形态结构及Wnt信号转导途径的影响

目的 比较产前给予不同剂量地塞米松对大鼠胎肺形态结构及Wnt信号转导途径的影响.方法 孕鼠12只,于孕16、17、18 d,连续3 d给孕鼠腹腔注射药物,随机分为3组,每组4只.地塞米松小剂量组：地塞米松0.4 mg/(kg·d),地塞米松大剂量组：地塞米松0.8 mg/(kg·d),均用生理盐水稀释至0.5ml;对照组：生理盐水0.5 ml/d;取孕19 d胎鼠肺组织,HE染色观察肺病理学改变;RT-PCR、Western-Blot方法检测Wnt信号转导途径中Wnt7b、GSK-3β、β-catenin基因mRNA和蛋白表达.结果 (1)肺脏病理学改变：HE染色可见：地塞米松小剂量组肺泡数目为(15.6±2.1)个;大剂量组(13.2±1.6)个,对照组(20.8±2.0)个;肺泡间隔厚度：地塞米松小剂量组(11±5)μm;大剂量组(11±4)μm;对照组(13±7)μm;肺泡腔结构：地塞米松小剂量组(2483 ±1336)μm2;大剂量组(2924 ±1705)μm2;对照组(1913±764)μm2;以上各指标地塞米松组与对照组差异均有统计学意义(P均＜0.01),地塞米松大剂量组较小剂量组肺泡数目明显减少(P＜0.01).(2)地塞米松组胎肺Wnt7b及β-catenin基因mRNA的表达量均高于对照组,GSK-3β表达量低于对照组(1.1±0.6)(P均＜0.05);地塞米松组胞浆GSK-3β蛋白表达量低于对照组,大剂量组低于小剂量组;地塞米松小剂量组胞浆β-catenin的表达高于对照组,大剂量组低于对照组;胞核β-catenin蛋白表达量高于对照组.结论 产前使用地塞米松,肺泡数目减少,肺泡腔结构变大,肺泡间隔厚度变薄,周围结缔组织减少,影响胎肺形态发育;Wnt7b、β-catenin和GSK-3β基因表达异常;胎肺形态发育异常可能是通过地塞米松所致的Wnt信号转导途径障碍而发生.

Effects of dexamethasone on lung morphogenesis in rats and the expression of Wnt signal transduction pathway in the lung of offspring

Objective Multiple signal transduction pathways,for example,Wnt signal transduction pathway,fibroblast growth factor(FGF),bone morphogenetic protein(BMP)etc,are involved in rat fetal lung development.Wnt signal has been shown to play important roles in regulating cell differentiation and prolileration.It is demonstrated that antenatal dexamethasone(DEX)use can induce lung dysplasia.A rat premature delivery model was developed in this study to compare the effects of DEX on antenatal rat fetal lung morphogenesis and the expressions of Wnt7b,β-catenin and glycogen synthase kinase 3β(GSK-3β)genes in the lung of offspring on 19th day of embryo.Methods Twelve pregnant rats were divided into three groups randomly:small dose DEX group,large dose DEX group and control group with 4 rats in each group.The rats in me control group were injected with saline 0.5 ml/d;those in small dose DEX group were injected with DEX 0.4 mg/(kg·d),the rats in large dose DEX group were injected with DEX 0.8 mg/(kg·d),DEX was diluted to 0.5 ml by saline.On the 19th day of gestation,the fetuses were surgically taken out and the histologic structures of fetal rat lungs were observed with light microscope.The RT-PCR and Western-blot methods were used to detect the expressions of Wnt7b,GSK-3β and β-catenin genes Mrna and protein.Results (1) Changes of histologic structure included alveolar numbers:small dose DEX group (15.6±2.1),large dose DEX group(13.2±1.6),control group(20.8±2.0);thickness of alveolar septum:small dose DEX group(11±5)μm,large dose DEX group(11±4)μm,control group(13±7)μm;alveolar space:small dose DEX group(2483±1336)μm2,large dose DEX group(2924±1705)μm2.and control group(1913±764)μm2.All the parameters showed significant difference between DEX grouDs and control group.(P<0.01 for all comparisons).(2)The expressions of Wnt7b(0.55±0.19,0.64 ±0.54)and β-catenin(2.03 ±0.58,2.40±0.89)genes Mrna of the study groups were significantly higher as compared with those of the control group[Wnt7b(0.18 ±0.10),β-catenin(1.77±0.54)](P<0.05 for all comparisons)while the expressions of GSK-3β(1.0±0.5)were lower than those of the control group (1.1±0.6)(P＜0.05).The expressions of GSK-3β protein in cytoplasm of the study groups[(26.6±19.7)μg,(10.7±7.4)μg]reduced gradually while β-catenin's[(79.5±1.2)μg,(148.3±30.4)μg]in the nucleus enhanced simuhaneously compared with the control group[(50.0±00.0)μg].Conclusions Small dose of antenatal DEX usage can improve the fetal lung development,larger dose of DEX may have negative effect on rat fetal lung morphogenesis.Antenatal DEX usage can change the expressions of Wnt7b,GSK-3β and β-catenin genes Mrna and protein,these changes may result in paramorphia during pregnancy.