绒毛膜羊膜炎与产前糖皮质激素双重暴露对早产大鼠胎肺成熟与发育的影响

Effects of chorioamnionitis and prenatal glucocorticoid on fetal lung maturation and development in preterm rats

摘要:

目的：探讨不同程度绒毛膜羊膜炎（chorioamnionitis，CA）与产前糖皮质激素双重暴露对早产大鼠胎肺成熟及远期肺发育的影响。方法：36只SD孕鼠随机分6组：生理盐水+地塞米松（A组）、脂多糖0.5 μg 地塞米松（B组）、脂多糖4.0 μg 地塞米松（C组）、生理盐水 生理盐水（D组）、脂多糖0.5 μg 生理盐水（E组）、脂多糖4.0 μg 生理盐水（F组）。孕19 d时每组每个羊膜腔内分别注射生理盐水、脂多糖 0.5、4.0 μg，24 h后分别肌注地塞米松 0.4 mg和生理盐水。再24 h后剖宫取胎，胎盘、胎膜行病检，每组随机处死6只新生鼠，胎肺行病检。实时荧光定量PCR测肺组织表面活性蛋白（surfactant protein，SP）A、B、C及炎性细胞因子白介素-1β（interleukin-1β，IL-1β）、肿瘤坏死因子-α（tumor necrosis factor-α，TNF-α）的mRNA相对水平。生后第15天（P15）肺组织切片做形态学观察。结果：（1）C、F组胎鼠死亡率高于其他组而子鼠生存率低于其他组（P均<0.05）。（2）肺炎和CA病理评分C、F组最高，B、E组次之，A、D组最低（P均<0.05）。（3）SP-A、SP-C mRNAs相对表达水平D、F组低于其余4组而B组最高（P均<0.05）；SP-B mRNA表达水平D、E、F组低于其余3组而B、C组最高（P均<0.05）。（4）IL-1β mRNA表达水平在F组最高（P<0.05）；TNF-α mRNA表达水平在C、F组最高，A、D组最低（P均<0.05）。（5）P15时C组肺泡发育明显受抑。结论：孕鼠羊膜腔内注射不同剂量脂多糖可诱导不同程度的CA和肺炎，组织学炎症程度随脂多糖剂量增高而加重；轻中度CA和产前地塞米松双重暴露不会对围产期母子生存率造成不利影响，不会抑制胎儿和新生儿生长，炎症不被抑制反而协同诱导更显著的肺成熟；重度CA和产前地塞米松双重暴露会带来不利影响，尤其是增加支气管肺发育不良风险。

Abstract:

Objective：To determine the effects of different degrees of chorioamnionitis（CA） and prenatal glucocorticoid on fetal lung maturation and development in preterm rats. Methods：Totally 36 pregnant SD rats were randomly assigned to 6 groups. A group：normal saline（NS）+dexamethasone（DEX）；B group：lipopolysaccharide（LPS） 0.5 μg DEX；C group：LPS 4.0 μg DEX；D group：NS NS；E group：LPS 0.5 μg NS；F group：LPS 4.0 μg NS. All groups underwent intraamniotic injection with NS，LPS（0.5 μg and 4.0 μg respectively） on gestational day 19；24 h later，rats were intramuscularly injected with DEX 0.4 mg and NS respectively. After another 24 h，pathological inflammation of placenta，chorioamnion and fetal lung were observed. Surfactant protein A，B，C（SP-A，SP-B，SP-C） and interleukin-1β（IL-1β），tumor necrosis factor-α（TNF-α） mRNAs in lung were determined by quantitative real-time PCR（qRT-PCR）. Lung morphologic observation was performed on postnatal day 15（P15）. Results：①fetal rat mortality in C，F groups were higher than that in other groups；rat survival rate in C，F groups were lower than that in other groups（P all <0.05）. ②Pathologi－cal grading of pulmonary inflammation and CA：C and F groups were the highest，followed by B and E groups and A and D groups were the lowest（P all <0.05）. ③Relative expression of SP-A，SP-C mRNAs：D and F groups were lower than other groups，B group was the highest（P all <0.05）；relative expression of SP-B mRNA：D，E，F groups were lower than other groups，B and C groups were the highest（P all <0.05）. ④Relative expression of IL-1β mRNA：F group was the highest（P<0.05）. Relative expression of TNF-α mRNA：C and F groups were the highest while A and D groups were the lowest（P<0.05）. ⑤On P15，C group alveolarization was significantly inhibited. Conclusions：Different doses of intraam－niotic LPS could induce CA and fetal lung inflammation with different degrees. Histological inflammation aggravates with LPS dose increasing. Mild to moderate CA and antenatal DEX will not adversely affect the survival rate nor inhibit fetus and newborn growth. Inflammation was not suppressed but synergistically induced more significant lung maturation. Severe CA and prenatal DEX might cause adverse effects，particularly，increasing the risk of bronchopulmonary dysplasia.