目的:出生前的冷暴露(CE)是可能影响哺乳动物怀孕的初始应激源之一,改变胎盘和胎儿的发育,影响后代的健康。糖皮质激素(GCs)参与机体对CE应激的反应,其具体作用机制尚不清楚。这项研究旨在确定CE应激对胎盘的影响,并测试应激是否,由妊娠冷暴露引起的胎儿发育,通过过度的GC表达改变胎盘血管生成。
方法:将30只SD大鼠暴露于冷孕前,建立CE大鼠模型,或者在第一次,第二,怀孕第三周。血清皮质醇和可溶性fms样酪氨酸激酶-1(sFlt-1)表达水平,生理指标变化(食物摄入量,体重变化和血压),和妊娠结局(胎鼠体重,活胎鼠的数量,和胎盘重量)在基线和受孕后的不同时间点收集。11β-羟基类固醇脱氢酶2(11β-HSD2)蛋白表达水平,糖皮质激素受体,血管内皮生长因子A(VEGF-A),胎盘生长因子(PIGF),通过蛋白质印迹法测量胎盘组织中的sFlt-1。滋养细胞中的细胞角蛋白(CK)和层粘连蛋白(LN),通过免疫荧光法评估全身冷处理后妊娠大鼠螺旋动脉血管平滑肌中的α-肌动蛋白,并通过荧光显微镜观察。为了测试11β-HSD2水平对胎盘重铸的影响,人类早孕绒毛外滋养层细胞(HTR8/SVneo)使用特异性11β-HSD2siRNA构建体进行敲除。通过定量实时PCR(qPCR)分析11β-HSD2在HTR8细胞中的表达水平,采用qPCR检测各组11β-HSD2基因的表达水平。通过Transwell迁移试验评估细胞迁移和侵袭,通过ELISA测量HTR8细胞中的sFlt-1水平。
结果:孕前CE导致整个妊娠期间血清皮质酮和sFlt-1水平持续升高,与对照动物相比,大鼠CE模型的舒张压(DBP)持续升高。妊娠第二周的CE(Gp.3)与胎盘重量显着降低有关(p=0.0003)。第三周(Gp.4)的冷暴露与胎儿体重降低显着相关(p=0.001)。孕前CE与胎盘11β-HSD2、糖皮质激素受体、VEGF-A,PIGF,和sFlt-1蛋白和α-肌动蛋白与对照组相比。通过siRNA沉默11β-HSD2导致细胞迁移和侵袭减少,HTR8/SVneo细胞中sFlt-1的表达水平显着增加(p<0.05)。
结论:孕前和妊娠早期暴露会导致GCs水平升高和胎盘11β-HSD2活性受损。我们建议,在妊娠早期,随后的11β-HSD2诱导的sFlt-1表达增加可能会影响胎盘血管重塑并改变胎盘形态结构和功能。
OBJECTIVE: Cold exposure (CE) before birth is one of the initial stressors that may impact mammalian pregnancy, changing placental and fetal development and affecting the health of the offspring. While glucocorticoids (GCs) participate in the body\'s response to the stress of CE, the specific mechanisms of their action are unclear. This study aims to determine the effect of CE stress on the placenta and to test whether stress, caused by cold exposure in pregnancy impairs fetal development by changing placental angiogenesis via excessive GC expression.
METHODS: CE rat model was created by exposing 30 SD rats to cold preconception, or during the first, second, and third weeks of pregnancy. Serum cortisol and soluble fms-like tyrosine kinase-1 (sFlt-1) expression levels, physiological index changes (food intake, body weight change and blood pressure), and pregnancy outcomes (fetal rat weight, number of live fetal rats, and placental weight) were collected at baseline and at different time points after the conception. Protein expression levels of 11 β-hydroxysteroid dehydrogenase 2 (11β-HSD2), glucocorticoid receptor, vascular endothelial growth factor A (VEGF-A), placental growth factor (PIGF), and sFlt-1 in placental tissues were measured by western blotting. Cytokeratin (CK) and laminin (LN) in trophoblasts, and α-actin in vascular smooth muscle of the spiral arteries of pregnant rats after the systemic cold treatment were assessed by immunofluorescence and visualized by fluorescent microscopy. To test the effect of 11β-HSD2 levels on the placental recasting, human first-trimester extravillous trophoblast cells (HTR8/SVneo) underwent knockdown using specific 11β-HSD2 siRNA constructs. Expression levels of 11β-HSD2 were analyzed by quantitative real-time PCR (qPCR) and into HTR8 cells, and the expression levels of the 11β-HSD2 gene in each group were measured using qPCR. Cell migration and invasion was assessed by Transwell migration assay, and sFlt-1 levels in HTR8 cells were measured by ELISA.
RESULTS: CE pre-conception led to consistently increasing serum corticosterone and sFlt-1 levels throughout pregnancy, and persistently increased diastolic blood pressure (DBP) in rat CE model compared to control animals. CE during the second week of gestation (Gp.3) was associated with significantly lower placental weight (p=0.0003). Cold exposure in the third week (Gp.4) was associated with significantly (p=0.001) lower fetal weight. CE pre-conception was associated with significantly decreased placental levels of 11β-HSD2, glucocorticoid receptor, VEGF-A, PIGF, and sFlt-1 proteins and α-actin compared to the control group. Silencing 11β-HSD2 by siRNA led to reduced cell migrations and invasion, and markedly increased expression levels of sFlt-1 in HTR8/SVneo cells (p<0.05).
CONCLUSIONS: Pre-conception cold exposure and during early pregnancy leads to increased GCs levels and impaired placental 11β-HSD2 activity. We suggest that the subsequent 11β-HSD2-induced increase in the sFlt-1expression during early pregnancy may affect placental vascular remodeling and change placental morphological structure and function.