The role of fetal breathing motions compared with gasping motions in pulmonary airway uptake of intra-amniotic iron dextran

Choriodecidual Group B Streptococcal Infection Induces miR-155-5p in the Fetal Lung in Macaca nemestrina

The mechanisms underlying fetal lung injury remain poorly defined. MicroRNAs (miRNAs) are small noncoding, endogenous RNAs that regulate gene expression and have been implicated in the pathogenesis of lung disease. Using a nonhuman primate model of choriodecidual infection, we sought to determine if differentially expressed miRNAs were associated with acute fetal lung injury. After inoculating 10 chronically catheterized pregnant monkeys (Macaca nemestrina) with either group B streptococcus (GBS) at 1 × 10(6) CFU (n = 5) or saline (n = 5) in the choriodecidual space, we extracted fetal lung mRNA and miRNA and profiled the changes in expression by microarray analysis. We identified 9 differentially expressed miRNAs in GBS-exposed fetal lungs, but of these, only miR-155-5p was validated by quantitative reverse transcription-PCR (P = 0.02). Significantly elevated miR-155-5p expression was also observed when immortalized human fetal airway epithelial (FeAE) cells were exposed to proinflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha [TNF-α]). Overexpression of miR-155-5p in FeAE cells in turn increased the production of IL-6 and CXCL10/gamma interferon-induced protein 10, which are implicated in leukocyte recruitment but also in protection from lung injury. Interestingly, while miR-155-5p decreased fibroblast growth factor 9 (FGF9) expression in a luciferase reporter assay, FGF9 levels were actually increased in GBS-exposed fetal lungs in vivo. FGF9 overexpression is associated with abnormal lung development. Thus, upregulation of miR-155-5p may serve as a compensatory mechanism to lessen the increase in FGF9 and prevent aberrant lung development. Understanding the complicated networks regulating lung development in the setting of infection is a key step in identifying how to prevent fetal lung injury leading to bronchopulmonary dysplasia.

The use of human amniotic fluid stem cells as an adjunct to promote pulmonary development in a rabbit model for congenital diaphragmatic hernia

OBJECTIVE

This study aimed to evaluate the potential benefit of intra-tracheal injection of human amniotic fluid stem cells (hAFSC) on pulmonary development combined with TO in a rabbit model for CDH.

METHODS

In time-mated pregnant does a left diaphragmatic defect was created at d23 (term = 31). At d28, previously operated fetuses were assigned to either TO and injection with 70 μL of phosphate buffered saline (PBS) or 1.0 × 10(6) c-Kit positive hAFSC expressing LacZ or were left untouched (CDH). Harvesting was done at d31 to obtain their lung-to-body weight ratio (LBWR), airway and vascular lung morphometry, X-gal staining and immunohistochemistry for Ki67 and surfactant protein-B (SP-B).

RESULTS

CDH-induced pulmonary hypoplasia is countered by TO + PBS, this reverses LBWR, mean terminal bronchiole density (MTBD) and medial thickness to normal. The additional injection of hAFSC decreases MTBD and results in a non-significant decrease in muscularization of intra-acinary vessels. There were no inflammatory changes and LacZ positive hAFSC were dispersed throughout the lung parenchyma 4 days after injection.

CONCLUSION

HAFSC exert an additional effect on TO leading to a decrease in MTBD, a measure of alveolar number surrounding the terminal bronchioles, without signs of toxicity. © 2015 John Wiley & Sons, Ltd.

Novel non-surgical prenatal approaches to treating congenital diaphragmatic hernia

This review focuses on the emerging field of non-surgical in-utero therapies in the management of fetal pulmonary hypoplasia and pulmonary hypertension associated with congenital diaphragmatic hernia (CDH). These experimental approaches include pharmacologic as well as stem-cell-based strategies. Current barriers of non-surgical therapies toward clinical translation are emphasized. As the severity of CDH will likely influence the efficacy of any in-utero therapy, the current status of prenatal imaging and the role of novel biomarkers, especially those related to fetal inflammation, are also reviewed.

Choriodecidual infection downregulates angiogenesis and morphogenesis pathways in fetal lungs from Macaca nemestrina

BACKGROUND

Intrauterine exposure to amniotic fluid (AF) cytokines is thought to predispose to bronchopulmonary dysplasia (BPD). We evaluated the effects of GBS exposure on RNA expression in fetal lung tissue to determine early molecular pathways associated with fetal lung injury that may progress to BPD.

METHODS

Ten chronically catheterized pregnant monkeys (Macaca nemestrina) at 118-125 days gestation (term = 172 days) received choriodecidual inoculation of either: 1) Group B Streptococcus (n = 5) or 2) saline (n = 5). Cesarean section and fetal necropsy was performed in the first week after GBS or saline inoculation regardless of labor. RNA was extracted from fetal lungs and profiled by microarray. Results were analyzed using single gene, Gene Set, and Ingenuity Pathway Analysis. Validation was by RT-PCR and immunohistochemistry.

RESULTS

Despite uterine quiescence in most cases, fetal lung injury occurred in four GBS cases (intra-alveolar neutrophils, interstitial thickening) and one control (peri-mortem hemorrhage). Significant elevations of AF cytokines (TNF-α, IL-8, IL-1β, IL-6) were detected in GBS versus controls (p<0.05). Lung injury was not directly caused by GBS, because GBS was undetectable by culture and PCR in the AF and fetal lungs. A total of 335 genes were differentially expressed greater than 1.5 fold (p<0.05) with GBS exposure associated with a striking upregulation of genes in innate and adaptive immunity and downregulation of pathways for angiogenesis, morphogenesis, and cellular growth and development.

CONCLUSIONS

A transient choriodecidual infection may induce fetal lung injury with profound alterations in the genetic program of the fetal lung before signs of preterm labor. Our results provide a window for the first time into early molecular pathways disrupting fetal lung angiogenesis and morphogenesis before preterm labor occurs, which may set the stage for BPD. A strategy to prevent BPD should target the fetus in utero to attenuate alterations in the fetal lung genetic program.

Lipopolysaccharide-induced injury is more pronounced in fetal transgenic ErbB4-deleted lungs

Pulmonary ErbB4 deletion leads to a delay in fetal lung development, alveolar simplification, and lung function disturbances in adult mice. We generated a model of intrauterine infection in ErbB4 transgenic mice to study the additive effects of antenatal LPS administration and ErbB4 deletion during fetal lung development. Pregnant mice were treated intra-amniotically with an LPS dose of 4 μg at E17 of gestation. Lungs were analyzed 24 h later. A significant influx of inflammatory cells was seen in all LPS-treated lungs. In heterozygote control lungs, LPS treatment resulted in a delay of lung morphogenesis characterized by a significant increase in the fraction of mesenchyme, a decrease in gas exchange area, and disorganization of elastic fibers. Surfactant protein (Sftp)b and Sftpc were upregulated, but mRNA of Sftpb and Sftpc was downregulated compared with non-LPS-treated controls. The mRNA of Sftpa1 and Sftpd was upregulated. In ErbB4-deleted lungs, the LPS effects were more pronounced, resulting in a further delay in morphological development, a more pronounced inflammation in the parenchyma, and a significant higher increase in all Sftp. The effect on Sftpb and Sftpc mRNA was somewhat different, resulting in a significant increase. These results imply a major role of ErbB4 in LPS-induced signaling in structural and functional lung development.

Intra-amniotic surfactant for women at risk of preterm birth for preventing respiratory distress in newborns

BACKGROUND

Early surfactant reduces mortality and pulmonary complications in preterm infants with respiratory distress syndrome. However, current surfactant administration strategies require endotracheal intubation with or without continued mechanical ventilation. Bronchopulmonary dysplasia and chronic lung disease (CLD) are associated with mechanical ventilation and potentially life-long effects. Non-invasive methods of surfactant administration including intra-amniotic surfactant may avoid endotracheal intubation and mechanical ventilation, potentially preventing development of CLD.

OBJECTIVES

To determine if intra-amniotic instillation of surfactant for women at risk of preterm birth, compared to placebo or no treatment or post-delivery tracheal surfactant instillation, reduces morbidity or mortality, or both, in preterm infants. If intra-amniotic instillation is effective, in subgroup analysis to determine the effect of 1) gestational age; 2) type of surfactant; 3) dose; 4) timing; 5) indication; and 6) multiple pregnancy.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (August 2009), MEDLINE (1950-August 2009), handsearched the Proceedings of Pediatric Academic Societies (American Pediatric Society, Society for Pediatric Research and European Society for Pediatric Research) from 1990-2009 in Pediatric Research Journal and Abstracts online and the Proceedings of Perinatal Society of Australia and New Zealand (PSANZ) (1996-2009). We also searched the Science Citation Index (Web of Science) (August 2009) and checked reference lists of identified studies. We contacted Abbott Laboratories, Inc for unpublished studies.

SELECTION CRITERIA

Published, unpublished and ongoing randomised controlled, cluster-randomised or quasi-randomised trials of intra-amniotic instillation of surfactant for women at risk of preterm birth, compared to placebo or no treatment or post-delivery tracheal surfactant instillation.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed study eligibility and quality.

MAIN RESULTS

We found no trials were found met the inclusion criteria for this review.

AUTHORS' CONCLUSIONS

We identified no randomised trials that evaluated the effect of intra-amniotic instillation of surfactant for women at risk of preterm birth. Evidence from animal and observational human studies suggest that intra-amniotic surfactant administration is potentially safe, feasible and effective. Well designed trials of intra-amniotic instillation of surfactant for women at risk of preterm birth are needed.

Study of fetal tracheal fluid velocities using Doppler ultrasound

OBJECTIVE

To characterize tracheal fluid flow during fetal breathing movements by Doppler ultrasound.

STUDY DESIGN

To use pulsed Doppler to measure flow velocity during inspiration and expiration in a cross-sectional study of 15 normal fetuses and determine the correlation, if any, between flow velocity and gestational age.

RESULTS

Cyclic respiratory profiles - both regular and irregular - were observed. Intratracheal flow velocity was very elevated during inspiration, ranging from 10 to 80 cm/s and from 5 to 20 cm/s during expiration.

CONCLUSION

This technique enables the noninvasive semiquantitative evaluation of fetal breathing movements. This Doppler application opens the field for future studies to characterize the extent of pulmonary hypoplasia.

Lipopolysaccharide increases alveolar type II cell number in fetal mouse lungs through Toll-like receptor 4 and NF-κB

Chorioamnionitis is a major cause of preterm delivery. Infants exposed to inflammation in utero and then born preterm may have improved lung function in the immediate postnatal period. We developed a mouse model of chorioamnionitis to study the inflammatory signaling mechanisms that might influence fetal lung maturation. With this in vivo model, we found that Escherichia coli lipopolysaccharide (LPS) increased the number of alveolar type II cells in the fetal mouse lung. LPS also increased type II cell number in cultured fetal lung explants, suggesting that LPS could directly signal the fetal lung in the absence of maternal influences. Using immunostaining, we localized cells within the fetal mouse lung expressing the LPS receptor molecule Toll-like receptor 4 (TLR4). Similar to the signaling pathways in inflammatory cells, LPS activated NF-κB in fetal lung explants. Activation of the TLR4/NF-κB pathway appeared to be required, as LPS did not increase the number of type II cells in C.C3H- Tlr4 Lps-d mice, a congenic strain containing a loss of function mutation in tlr4. In addition, the sesquiterpene lactone parthenolide inhibited NF-κB activation following LPS exposure and blocked the LPS-induced increase in type II cells. On the basis of these data from our mouse model of chorioamnionitis, it appears that LPS specifically activated the TLR4/NF-κB pathway, leading to increased type II cell maturation. These data implicate an important signaling mechanism in chorioamnionitis and suggest the TLR4/NF-κB pathway can influence lung development.