Pulmonary transcriptome analysis in the surgically induced rabbit model of diaphragmatic hernia treated with fetal tracheal occlusion

A Tracheal Aspirate-derived Airway Basal Cell Model Reveals a Proinflammatory Epithelial Defect in Congenital Diaphragmatic Hernia

Rationale: Congenital diaphragmatic hernia (CDH) is characterized by incomplete closure of the diaphragm and lung hypoplasia. The pathophysiology of lung defects in CDH is poorly understood. Objectives: To establish a translational model of human airway epithelium in CDH for pathogenic investigation and therapeutic testing. Methods: We developed a robust methodology of epithelial progenitor derivation from tracheal aspirates of newborns. Basal stem cells (BSCs) from patients with CDH and preterm and term non-CDH control subjects were derived and analyzed by bulk RNA sequencing, assay for transposase accessible chromatin with sequencing, and air-liquid interface differentiation. Lung sections from fetal human CDH samples and the nitrofen rat model of CDH were subjected to histological assessment of epithelial defects. Therapeutics to restore epithelial differentiation were evaluated in human epithelial cell culture and the nitrofen rat model of CDH. Measurements and Main Results: Transcriptomic and epigenetic profiling of CDH and control BSCs reveals a proinflammatory signature that is manifested by hyperactive nuclear factor kappa B and independent of severity and hernia size. In addition, CDH BSCs exhibit defective epithelial differentiation in vitro that recapitulates epithelial phenotypes found in fetal human CDH lung samples and fetal tracheas of the nitrofen rat model of CDH. Furthermore, blockade of nuclear factor kappa B hyperactivity normalizes epithelial differentiation phenotypes of human CDH BSCs in vitro and in nitrofen rat tracheas in vivo. Conclusions: Our findings have identified an underlying proinflammatory signature and BSC differentiation defects as a potential therapeutic target for airway epithelial defects in CDH.

A novel surgical toxicological-free model of diaphragmatic hernia in fetal rats

BACKGROUND

Teratogen-induced congenital diaphragmatic hernia (CDH) rat models are commonly used to study the pathophysiology. We have created a new and reliable surgically induced diaphragmatic hernia (DH) model to obtain a purely mechanical DH rat model, and avoid the confounding teratogen-induced effects on the lung development.

METHODS

Fetal DH was surgically created on fetuses at E18.5 and harvested at E21.5 in rats. Four groups were evaluated (n = 16): control (CONT), control exposed to Nitrofen (CONT NIT), DH surgically created (DH SURG), and CDH Nitrofen (CDH NIT). Body weight, total lung weights, and their ratio (BW, TLW, and TLBR) were compared. Air space (AS), parenchyma (PA), total protein, and DNA contents were measured to verify lung hypoplasia. Medial wall thickness (MWT) of pulmonary arterioles was also analyzed.

RESULTS

DH SURG showed significant hypoplasia (decreased in total protein and DNA) vs CONT (p < 0.05); DH SURG vs CDH NIT were similar in TLW and TLBR. DH SURG has less AS than CONT (p < 0.05) and similar PA compared to CONT NIT and CDH NIT, MWT were similarly increased in CONT NIT, DH SURG, and CDH NIT.

CONCLUSIONS

This novel surgical model generates fetal lung hypoplasia contributing to the study of the mechanical compression effect on fetal lung development in DH.

IMPACT

There is a critical need to develop a surgical model in rat to complement the findings of the well-known Nitrofen-induced CDH model. This experimental study is pioneer and can help to understand better the CDH pathophysiological changes caused by herniated abdominal viscera compression against the lung during the final stage of gestation in CDH fetuses, and also to develop more efficient treatments in near future.

Perinatal Outcomes after Fetal Endoscopic Tracheal Occlusion for Isolated Congenital Diaphragmatic Hernia: Rapid Review

OBJECTIVE

 To compare the perinatal outcomes of fetuses with isolated congenital diaphragmatic hernia after fetal endoscopic tracheal occlusion (FETO) and antenatal expectant management.

DATA SOURCES

 In this rapid review, searches were conducted in the MEDLINE, PMC, EMBASE and CENTRAL databases between August 10th and September 4th, 2020. Randomized controlled trials (RCTs), quasi-RCTs or cluster-RCTs published in English in the past ten years were included.

STUDY SELECTION

 We retrieved 203 publications; 180 studies were screened by abstract. Full-text selection was performed for eight studies, and 1 single center RCT met the inclusion criteria (41 randomized women; 20 in the FETO group, and 21 in the control group).

DATA COLLECTION

 Data collection was performed independently, by both authors, in two steps (title and abstract and full-text reading).

DATA SYNTHESIS

 There were no cases of maternal mortality. The mean gestational age at delivery was of 35.6 ±  2.4 weeks in the intervention group, and of 37.4 ±  1.9 weeks among the controls (p < 0.01). Survival until 6 months of age was reported in 50% of the intervention group, and in 5.8% of the controls (p < 0.01; relative risk: 10.5; 95% confidence interval [95%CI]: 1.5-74.7). Severe postnatal pulmonary hypertension was found in 50% of the infants in the intervention group, and in 85.7% of controls (p = 0.02; relative risk: 0.6; 95%CI: 0.4-0.9). An analysis of the study indicated some concerns of risk of bias. The quality of evidence was considered moderate to low.

CONCLUSION

 Current evidence is limited but suggests that FETO may be an effective intervention to improve perinatal outcomes.

Mouse lung organoid responses to reduced, increased, and cyclic stretch

Most lung development occurs in the context of cyclic stretch. Alteration of the mechanical microenvironment is a common feature of many pulmonary diseases, with congenital diaphragmatic hernia (CDH) and fetal tracheal occlusion (FETO, a therapy for CDH) being extreme examples with changes in lung structure, cell differentiation, and function. To address limitations in cell culture and in vivo mechanotransductive models, we developed two mouse lung organoid (mLO) mechanotransductive models using postnatal day 5 (PND5) mouse lung CD326-positive cells and fibroblasts subjected to increased, decreased, and cyclic strain. In the first model, mLOs were exposed to forskolin (FSK) and/or disrupted (DIS) and evaluated at 20 h. mLO cross-sectional area changed by +59%, +24%, and -68% in FSK, control, and DIS mLOs, respectively. FSK-treated organoids had twice as many proliferating cells as other organoids. In the second model, 20 h of 10.25% biaxial cyclic strain increased the mRNAs of lung mesenchymal cell lineages compared with static stretch and no stretch. Cyclic stretch increased TGF-β and integrin-mediated signaling, with upstream analysis indicating roles for histone deacetylases, microRNAs, and long noncoding RNAs. Cyclic stretch mLOs increased αSMA-positive and αSMA-PDGFRα-double-positive cells compared with no stretch and static stretch mLOs. In this PND5 mLO mechanotransductive model, cell proliferation is increased by static stretch, and cyclic stretch induces mesenchymal gene expression changes important in postnatal lung development.

The Cellular and Molecular Effects of Fetoscopic Endoluminal Tracheal Occlusion in Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) is a complex disease associated with pulmonary hypoplasia and pulmonary hypertension. Great strides have been made in our ability to care for CDH patients, specifically in the prenatal improvement of lung volume and morphology with fetoscopic endoluminal tracheal occlusion (FETO). While the anatomic effects of FETO have been described in-depth, the changes it induces at the cellular and molecular level remain a budding area of CDH research. This review will delve into the cellular and molecular effects of FETO in the developing lung, emphasize areas in which further research may improve our understanding of CDH, and highlight opportunities to optimize the FETO procedure for improved postnatal outcomes.

Fetal Tracheal Occlusion Increases Lung Basal Cells via Increased Yap Signaling

Fetal endoscopic tracheal occlusion (FETO) is an emerging surgical therapy for congenital diaphragmatic hernia (CDH). Ovine and rabbit data suggested altered lung epithelial cell populations after tracheal occlusion (TO) with transcriptomic signatures implicating basal cells. To test this hypothesis, we deconvolved mRNA sequencing (mRNA-seq) data and used quantitative image analysis in fetal rabbit lung TO, which had increased basal cells and reduced ciliated cells after TO. In a fetal mouse TO model, flow cytometry showed increased basal cells, and immunohistochemistry demonstrated basal cell extension to subpleural airways. Nuclear Yap, a known regulator of basal cell fate, was increased in TO lung, and Yap ablation on the lung epithelium abrogated TO-mediated basal cell expansion. mRNA-seq of TO lung showed increased activity of downstream Yap genes. Human lung specimens with congenital and fetal tracheal occlusion had clusters of subpleural basal cells that were not present in the control. TO increases lung epithelial cell nuclear Yap, leading to basal cell expansion.

Reversible Fetal Tracheal Occlusion in Mice: A Novel Minimal Invasive Technique

BACKGROUND

There is a certain need for reversible, cheap, and reproducible animal models for understanding the impact of tracheal occlusion (TO) in the congenital diaphragmatic hernia and pathophysiology. We aimed to present an easy, reversible, and minimally invasive murine TO model with optimized time points for introduction and removal of TO.

METHODS

Time-mated C57BL/6 mice underwent laparotomy at embryonic day 16.5 (E16.5) with transuterine TO performed on two fetuses in each uterine horn. In the TO group, the fetuses were harvested at E18.5 without suture removal; the suture was released at E17.5 in the TO-R group, and all fetuses were harvested at E18.5. The lungs of the fetuses were compared by morphometric and histologic analysis.

RESULTS

Successful TO was confirmed in 34 of 37 fetuses. Twenty-nine of them survived to E18.5 (90.6%), six of the fetuses had a spontaneous vaginal delivery. Fetal weights were comparable, but there was significant difference in lung weights and lung-to-body weight ratios (0.020 ± 0.006 [control] versus 0.026 ± 0.002 [TO] versus 0.023 ± 0.005 [TO-R]; P = 0.013). DNA/protein and DNA/lung weight ratios were elevated, whereas protein/lung weight ratio was lower in TO compared with the control group.

CONCLUSIONS

Reversal of fetal transuterine TO at E17.5, which was put at E16.5 in mice, is feasible with comparable outcomes to other current animal models with certain advantages and potential to translate the studies to the human.

Basic and translational science advances in congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a birth defect that is characterized by lung hypoplasia, pulmonary hypertension and a diaphragmatic defect that allows herniation of abdominal organs into the thoracic cavity. Although widely unknown to the public, it occurs as frequently as cystic fibrosis (1:2500). There is no monogenetic cause, but different animal models revealed various biological processes and epigenetic factors involved in the pathogenesis. However, the pathobiology of CDH is not sufficiently understood and its mortality still ranges between 30 and 50%. Future collaborative initiatives are required to improve our basic knowledge and advance novel strategies to (prenatally) treat the abnormal lung development. This review focusses on the genetic, epigenetic and protein background and the latest advances in basic and translational aspects of CDH research.

Heterogeneous Response in Rabbit Fetal Diaphragmatic Hernia Lungs After Tracheal Occlusion

BACKGROUND

Fetal tracheal occlusion (TO) is an experimental therapeutic approach to stimulate lung growth in the most severe congenital diaphragmatic hernia (CDH) cases. We have previously demonstrated a heterogeneous response of normal fetal rabbit lungs after TO with the appearance of at least two distinct zones. The aim of this study was to examine the fetal lung response after TO in a left CDH fetal rabbit model.

METHODS

Fetal rabbits at 25 d gestation underwent surgical creation of CDH followed by TO at 27 d and harvest on day 30. Morphometric analysis, global metabolomics, and fluorescence lifetime imaging microscopy (FLIM) were performed to evaluate structural and metabolic changes in control, CDH, and CDH + TO lungs.

RESULTS

Right and left lungs were different at the baseline and had a heterogeneous pulmonary growth response in CDH and after TO. The relative percent growth of the right lungs in CDH + TO was higher than the left lungs. Morphometric analyses revealed heterogeneous tissue-to-airspace ratios, in addition to size and number of airspaces within and between the lungs in the different groups. Global metabolomics demonstrated a slower rate of metabolism in the CDH group with the left lungs being less metabolically active. TO stimulated metabolic activity in both lungs to different degrees. FLIM analysis demonstrated local heterogeneity in glycolysis, oxidative phosphorylation (OXPHOS), and FLIM "lipid-surfactant" signal within and between the right and left lungs in all groups.

CONCLUSIONS

We demonstrate that TO leads to a heterogeneous morphologic and metabolic response within and between the right and left lungs in a left CDH rabbit model.

Tandem mass tag (TMT) proteomic analysis of fetal lungs revealed differential expression of tight junction proteins in a rat model of congenital diaphragmatic hernia

OBJECTIVE

Congenital diaphragmatic hernia (CDH) is a common and often lethal birth defect characterized by congenital lung malformation, which severely affects neonate prognosis and mortality. This study aimed to investigate differences in protein expression in order to elucidate the mechanism of CDH-associated pulmonary hypoplasia during the early stage of lung development using tandem mass tag (TMT) quantitative proteomics.

METHODS

Nitrofen was administered orally to establish a rat CDH model, and pathological changes were evaluated through hematoxylin-eosin (H&E), PCNA, and Ki67 staining at the pseudoglandular stage. Fetal lungs were then collected, pooled before TMT labeling, and subjected to mass spectrometry. Immunohistochemistry (IHC), Western blotting, and Q-PCR were used to further validate the candidate proteins.

RESULTS

A total of 79 differentially expressed proteins (DEPs) were identified when CDH and control lungs were compared, and further bioinformatics analysis showed that these proteins play important roles in tight-junctions, phospholipase D signaling, and the HIF-1 signaling pathway. Three differentially expressed proteins, Cldn3, Magi1, and Myh9 are involved in the tight-junction pathway (P < 0.05), and their differential expressions were confirmed by IHC, Western blotting, and Q-PCR.

CONCLUSION

These findings indicate that alterations of tight-junction protein expression may play an important role in the pathogenesis of abnormal lung development in CDH. Further studies are warranted to verify the mechanism by which these tight-junction proteins influence the pathogenesis of CDH-associated pulmonary hypoplasia.

The effects of tracheal occlusion on Wnt signaling in a rabbit model of congenital diaphragmatic hernia

PURPOSE

Tracheal occlusion (TO) reverses pulmonary hypoplasia (PH) in congenital diaphragmatic hernia (CDH), but its mechanism of action remains poorly understood. Wnt signaling plays a critical role in lung development, but few studies exist. The purpose of our study was to a) confirm that our CDH rabbit model produced PH which was reversed by TO and b) determine the effects of CDH +/- TO on Wnt signaling.

METHODS

CDH was created in fetal rabbits at 23 days, TO at 28 days, and lung collection at 31 days. Lung body weight ratio (LBWR) and mean terminal bronchiole density (MTBD) were determined. mRNA and miRNA expression was determined in the left lower lobe using RT-qPCR.

RESULTS

Fifteen CDH, 15 CDH + TO, 6 sham CDH, and 15 controls survived and were included in the study. LBWR was low in CDH, while CDH + TO was similar to controls (p = 0.003). MTBD was higher in CDH fetuses and restored to control levels in CDH + TO (p < 0.001). Reference genes TOP1, SDHA, and ACTB were consistently expressed within and between treatment groups. miR-33 and MKI67 were increased, and Lgl1 was decreased in CDH + TO.

CONCLUSION

TO reversed pulmonary hypoplasia and stimulated early Wnt signaling in CDH fetal rabbits.

TYPE OF STUDY

Basic science, prospective.

LEVEL OF EVIDENCE

II.

Proteomic profiling of tracheal fluid in an ovine model of congenital diaphragmatic hernia and fetal tracheal occlusion

Congenital diaphragmatic hernia (CDH) occurs in ~1:2,000 pregnancies and is associated with substantial morbidity and mortality. Fetal tracheal occlusion (TO) is an emerging therapy that improves lung growth and reduces mortality, although substantial respiratory compromise persists in survivors. In this study, we used tracheal fluid in a fetal sheep model of CDH with TO for proteomic analysis with subsequent validation of findings in sheep lung tissue. We found that the proteomic profiles of CDH tracheal fluid was most similar to control lung and CDH/TO lung most similar to TO lung. Among 118 proteins altered in CDH, only 11 were reciprocally regulated in CDH/TO. The most significantly altered pathways and processes were cell proliferation, phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin signaling, inflammation, and microtubule dynamics. CDH suppressed and TO promoted cell proliferation and AKT-related signaling cascades. By Western blot analysis and immunohistochemistry, epithelial PCNA and phosphorylated AKT were decreased in CDH and increased in TO and CDH/TO lungs. The Wnt target Axin2 was decreased threefold in CDH lung compared with control without a significant increase in CDH/TO lung. Cilia-related pathways were among the most dysregulated with CDH lung having a nearly twofold increase in acetylated α-tubulin and a relative increase in the number of ciliated cells. While TO improves lung growth and patient survival in CDH, the procedure substantially alters many processes important in lung development and cell differentiation. Further elucidation of these changes will be critical to improving lung health in infants with CDH treated with TO.

MicroRNA 200b is upregulated in the lungs of fetal rabbits with surgically induced diaphragmatic hernia

OBJECTIVE

Profiling of miR-200b expression and its targets (transforming growth factor [TGF]-β2 and ZEB2) in the surgical rabbit congenital diaphragmatic hernia (DH) model before and after tracheal occlusion (TO).

METHODS

Thirty-eight timed-pregnant rabbits had left DH creation on gestational day (GD) 23. On GD28, 17 randomly selected fetuses had TO. We harvested fetuses at GD23, GD28, or GD30. We calculated lung-to-body weight ratios, processed lungs for miR-200b in situ hybridization and real-time quantitative polymerase chain reaction, and evaluated effects on downstream targets TGF-β2 or ZEB2.

RESULTS

We obtained 16 DH fetuses (n = 7 GD28 and n = 9 GD30), 13 TO fetuses (GD30), and 38 control fetuses (n = 15 GD23, n = 11 GD28, and n = 12 GD30). Diaphragmatic hernia lungs were hypoplastic, and TO resulted in control lung-to-body weight ratio levels. Term miR-200b-3p levels were significantly upregulated in the hypoplastic compared with control ipsilateral lung (1.906 ± 0.90 vs 0.7429 ± 0.44) (P < .01). Fetal TO ipsilateral lungs displayed a variable miR-200b response on in situ hybridization and polymerase chain reaction, with levels similar to control and congenital DH lungs. The TGF-β2 was unchanged in hypoplastic and TO lungs, and ZEB2 tended to be reduced in TO compared with DH lungs (1.79 [0.4-2.9] vs 0.73 [0.5-1.4]).

CONCLUSIONS

Hypoplastic fetal rabbit lungs display upregulation of miR-200b expression although downstream targets are not different from controls. Following TO, fetal rabbit lungs display a variable miR-200b response.

Fetal tracheal occlusion in mice: a novel transuterine method

BACKGROUND

Fetal tracheal occlusion (TO) is an emerging surgical therapy in congenital diaphragmatic hernia that improves the fetal lung growth. Different animal models of congenital diaphragmatic hernia and TO present advantages and disadvantages regarding ethical issues, cost, surgical difficulty, size, survival rates, and available genetic tools. We developed a minimally invasive murine transuterine TO model, which will be useful in defining how TO impacts lung molecular biology, cellular processes, and overall lung physiology.

MATERIALS AND METHODS

Time-mated C57BL/6 mice underwent laparotomy at embryonic day 16.5 (E16.5) with transuterine TO performed on two fetuses in each uterine horn. At E18.5, dams were sacrificed and fetuses harvested. The lungs of the TO fetuses were compared with the nonmanipulated counterparts by morphometric and histologic analysis.

RESULTS

Successful TO was confirmed in 16 of 20 TO fetuses. Twelve of them survived to E18.5 (75%). Fetal weights were comparable, but lung weights were significantly greater in TO (28.41 ± 5.87 versus 23.38 ± 3.09, P = 0.043). Lung to body weight ratio was also greater (0.26 ± 0.003 versus 0.22 ± 0.002, P = 0.006). E18.5 TO lungs demonstrated dilated central and distal airspaces with increased cellularity. DNA/protein and DNA/lung weight ratios were elevated while protein/lung weight ratio was lower in TO compared to control.

CONCLUSIONS

Mice fetal transuterine TO is feasible with comparable outcomes to other current animal models. The increase in the lung weight, lung to body weight ratio and the DNA/protein ratio indicate organized lung growth rather than edema or cell hypertrophy.

Excessive Reversal of Epidermal Growth Factor Receptor and Ephrin Signaling Following Tracheal Occlusion in Rabbit Model of Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) causes severe pulmonary hypoplasia from herniation of abdominal contents into the thorax. Tracheal occlusion (TO) for human CDH improves survival, but morbidity and mortality remain high, and we do not fully understand the cellular pathways and processes most severely impacted by CDH and TO. We created a left diaphragmatic hernia (DH) in rabbit fetuses with subsequent TO and collected left lung sections for NextGen mRNA sequencing. DH, TO, and DHTO fetuses had comparable body and organ growth to control except for lower lung weights in DH (p<0.05). Of 13,687 expressed genes, DHTO had 687 differentially expressed genes compared to DH, but no other group-group comparison had more than 10. Considering genes in combination, many of the genes reduced in DH were more highly expressed in DHTO than in control. Benchmarking fetal rabbit lung gene expression to published lung development data, both DH and DHTO lungs were more highly correlated with the gene expression of immature lung. DNA synthesis was upregulated in DHTO compared to DH and ribosome and protein synthesis pathways were downregulated. DH reduced total and epithelial cell proliferation by half and two-thirds respectively, and DHTO increased proliferation by 2.5 and 3.4-fold respectively. Signaling pathways downregulated by DH and upregulated in DHTO were epidermal growth factor receptor signaling, ephrin signaling, and cell migration; however, levels of ephrin and EGFR signaling in DHTO exceeded that of control. Identification and inhibition of the ligands responsible for this dysregulated signaling could improve lung development in CDH.