Prenatal microRNA miR-200b Therapy Improves Nitrofen-induced Pulmonary Hypoplasia Associated With Congenital Diaphragmatic Hernia

Cellular origins and translational approaches to congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a complex developmental abnormality characterized by abnormal lung development, a diaphragmatic defect and cardiac dysfunction. Despite significant advances in management of CDH, mortality and morbidity continue to be driven by pulmonary hypoplasia, pulmonary hypertension, and cardiac dysfunction. The etiology of CDH remains unknown, but CDH is presumed to be caused by a combination of genetic susceptibility and external/environmental factors. Current research employs multi-omics technologies to investigate the molecular profile and pathways inherent to CDH. The aim is to discover the underlying pathogenesis, new biomarkers and ultimately novel therapeutic targets. Stem cells and their cargo, non-coding RNAs and agents targeting inflammation and vascular remodeling have produced promising results in preclinical studies using animal models of CDH. Shortcomings in current therapies combined with an improved understanding of the pathogenesis in CDH have given rise to novel promising experimental treatments that are currently being evaluated in clinical trials. This review provides insight into current developments in translational research, ranging from the cellular origins of abnormal cardiopulmonary development in CDH and the identification of novel treatment targets in preclinical CDH models at the bench and their translation to clinical trials at the bedside.

Fetal hypoplastic lungs have multilineage inflammation that is reversed by amniotic fluid stem cell extracellular vesicle treatment

Antenatal administration of extracellular vesicles from amniotic fluid stem cells (AFSC-EVs) reverses features of pulmonary hypoplasia in models of congenital diaphragmatic hernia (CDH). However, it remains unknown which lung cellular compartments and biological pathways are affected by AFSC-EV therapy. Herein, we conducted single-nucleus RNA sequencing (snRNA-seq) on rat fetal CDH lungs treated with vehicle or AFSC-EVs. We identified that intra-amniotically injected AFSC-EVs reach the fetal lung in rats with CDH, where they promote lung branching morphogenesis and epithelial cell differentiation. Moreover, snRNA-seq revealed that rat fetal CDH lungs have a multilineage inflammatory signature with macrophage enrichment, which is reversed by AFSC-EV treatment. Macrophage enrichment in CDH fetal rat lungs was confirmed by immunofluorescence, flow cytometry, and inhibition studies with GW2580. Moreover, we validated macrophage enrichment in human fetal CDH lung autopsy samples. Together, this study advances knowledge on the pathogenesis of pulmonary hypoplasia and further evidence on the value of an EV-based therapy for CDH fetuses.

Microinjection With Nanoparticles to Deliver Drugs in Prenatal Lung Explants - A Pilot Study for Prenatal Therapy in Congenital Diaphragmatic Hernia

BACKGROUND

Fetoscopic endoluminal tracheal occlusion (FETO) improves the survival rate in fetuses with severe congenital diaphragmatic hernia (CDH). We hypothesize that prenatal therapies into the trachea during FETO can further improve outcomes. Here, we present an ex vivo microinjection technique with rat lung explants to study prenatal therapy with nanoparticles.

METHODS

We used microsurgery to isolate lungs from rats on embryonic day 18. We injected chitosan nanoparticles loaded with fluorescein (FITC) into the trachea of the lung explants. We compared the difference in biodistribution of two types of nanoparticles, functionalized IgG-conjugated nanoparticles (IgG-nanoparticles) and bare nanoparticles after 24 h culture with immunofluorescence (IF). We used IF to mark lung epithelial cells with E-cadherin and to investigate an apoptosis (Active-caspase 3) and inflammatory marker (Interleukin, IL-6) and compared its abundance between the two experimental groups and control lung explants.

RESULTS

We detected the presence of nanoparticles in the lung explants, and the relative number of nanoparticles to cells was 2.49 fold higher in IgG-nanoparticles than bare nanoparticles (p < 0.001). Active caspase-3 protein abundance was similar in the control, bare nanoparticles (1.20 fold higher), and IgG-nanoparticles (1.34 fold higher) groups (p = 0.34). Similarly, IL-6 protein abundance was not different in the control, bare nanoparticles (1.13 fold higher), and IgG-nanoparticles (1.12 fold higher) groups (p = 0.33).

CONCLUSIONS

Functionalized nanoparticles had a higher presence in lung cells and this did not result in more apoptosis or inflammation. Our proof-of-principle study will guide future research with therapies to improve lung development prenatally.

LEVELS OF EVIDENCE

N/A TYPE OF STUDY: Animal and laboratory study.

Exploring new perspectives on congenital diaphragmatic hernia: A comprehensive review

Congenital diaphragmatic hernia (CDH) represents a developmental anomaly that profoundly impacts the embryonic development of both the respiratory and cardiovascular systems. Understanding the influences of developmental defects, their origins, and clinical consequences is of paramount importance for further research and the advancement of therapeutic strategies for this condition. In recent years, groundbreaking studies in the fields of metabolomics and genomics have significantly expanded our knowledge regarding the pathogenic mechanisms of CDH. These investigations introduce novel diagnostic and therapeutic avenues. CDH implies a scarcity of available information within this domain. Consequently, a comprehensive literature review has been undertaken to synthesize existing data, providing invaluable insights into this rare disease. Improved comprehension of the molecular underpinnings of CDH has the potential to refine diagnostic precision and therapeutic interventions, thus potentially enhancing clinical outcomes for CDH patients. The identification of potential biomarkers assumes paramount significance for early disease detection and risk assessment in CDH, facilitating prompt recognition and the implementation of appropriate interventions. The process of translating research findings into clinical practice is significantly facilitated by an exhaustive literature review. It serves as a pivotal step, enabling the integration of novel, more effective diagnostic and therapeutic modalities into the management of CDH patients.

The RNA-binding protein quaking is upregulated in nitrofen-induced congenital diaphragmatic hernia lungs at the end of gestation

BACKGROUND

The RNA-binding protein Quaking (QKI) increases during epithelial-to-mesenchymal transition and its expression is controlled by microRNA-200 family members. Here, we aimed to describe the expression of QKI in the developing lungs of control and nitrofen-induced congenital diaphragmatic hernia lungs (CDH).

METHODS

To investigate the expression of QKI, we dissected lungs from control and nitrofen-induced CDH rats on embryonic day 15, 18, 21 (E15, E18, E21). We performed immunofluorescence (IF) and quantitative reverse transcription PCR (RT-qPCR) for QKI expression. Additionally, we assessed Interleukin-6 (IL-6) abundance using IF.

RESULTS

On E21, IF showed that the abundance of all three QKI isoforms and IL-6 protein was higher in CDH lungs compared to control lungs (QKI5: p = 0.023, QKI6: p = 0.006, QKI7: p = 0.014, IL-6: p = 0.045, respectively). Furthermore, RT-qPCR data showed increased expression of QKI5, QKI6, and QKI7 mRNA in E21 nitrofen lungs by 1.63 fold (p = 0.001), 1.63 fold (p = 0.010), and 1.48 fold (p = 0.018), respectively.

CONCLUSIONS

Our data show an increase in the abundance and expression of QKI at the end of gestation in nitrofen-induced CDH lungs. Therefore, a disruption in the regulation of QKI during the late stage of pregnancy could be associated with the pathogenesis of abnormal lung development in CDH.

Inflammation in Hernia and the epigenetic control

Inflammation is much more intrinsic to hernia then is what is generally appreciated. The occurrence of hernias is associated with swelling, stress and inflammation. Surgery remains an important intervention to treat hernias and for many years, post-surgical levels of inflammatory cytokines have been evaluated to compare the different strategies for their comparative advantages. All surgical procedures elicit some sort of inflammatory response and moreover the meshes used for hernia repair are also associated with elevated inflammatory response, although some favor predominantly a pro-inflammatory response while the other meshes favor anti-inflammatory response. An estimated more than 90% of hernia repairs involve some meshes with polypropylene considered as the gold standard. Efforts are underway to modulate polypropylene meshes associated inflammation through use of alternative materials as well as modifications to polypropylene meshes themselves. In the last one decade, miRNAs have entered hernia research and the data on a role of miRNAs in different hernias is slowly emerging, providing the first evidence of epigenetics in hernia. Some reports are connecting miRNAs with inflammation in hernia. All these aspects, such as, surgery-related to mesh-related inflammation as well as miRNA-related inflammation, are discussed in this article to present an up-to-date information on the topic.

Overactivated Epithelial NF-κB Disrupts Lung Development in Congenital Diaphragmatic Hernia

Abnormal lung development is the main cause of morbidity and mortality in neonates with congenital diaphragmatic hernia (CDH), a common birth defect (1:2,500) of largely unknown pathobiology. Recent studies discovered that inflammatory processes, and specifically NF-κB-associated pathways, are enriched in human and experimental CDH. However, the molecular signaling of NF-κB in abnormal CDH lung development and its potential as a therapeutic target require further investigation. Using sections and hypoplastic lung explant cultures from the nitrofen rat model of CDH and human fetal CDH lungs, we demonstrate that NF-κB and its downstream transcriptional targets are hyperactive during abnormal lung formation in CDH. NF-κB activity was especially elevated in the airway epithelium of nitrofen and human CDH lungs at different developmental stages. Fetal rat lung explants had impaired pseudoglandular airway branching after exposure to nitrofen, together with increased phosphorylation and transcriptional activity of NF-κB. Dexamethasone, the broad and clinically applicable antiinflammatory NF-κB antagonist, rescued lung branching and normalized NF-κB signaling in hypoplastic lung explants. Moreover, specific NF-κB inhibition with curcumenol similarly rescued ex vivo lung hypoplasia and restored NF-κB signaling. Last, we showed that prenatal intraperitoneal dexamethasone administration to pregnant rat dams carrying fetuses with hypoplastic lungs significantly improves lung branching and normalizes NF-κB in vivo. Our results indicate that NF-κB is aberrantly activated in human and nitrofen CDH lungs. Antiinflammatory treatment with dexamethasone and/or specific NF-κB inhibition should be investigated further as a therapeutic avenue to target lung hypoplasia in CDH.

Mesenchymal stem cell-derived extracellular vesicles prevent the formation of pulmonary arterial hypertension through a microRNA-200b-dependent mechanism

BACKGROUND

Bone marrow mesenchymal stem cell-derived extracellular vesicles (BMSC-EVs) have been highly studied with their critical roles as carriers of therapeutic targets such as microRNAs (miRNAs) in the treatment of human diseases, including pulmonary arterial hypertension (PAH). Herein, we tried to study the potential of BMSC-EVs to deliver miR-200b for the regulation of macrophage polarization in PAH.

METHODS

Rat models of PAH were induced with monocrotaline treatment, followed by miR-200b expression detection in lung tissues, pulmonary artery smooth muscle cells (PASMCs) and macrophages. miR-200b-containing BMSCs or miR-200b-deficient BMSCs were selected to extract EVs. Then, we assessed the changes in rats with PAH-associated disorders as well as in vitro macrophage polarization and the functions of PASMCs after treatment with BMSC-EVs. Moreover, the interaction between miR-200b, phosphodiesterase 1 A (PDE1A) was identified with a luciferase assay, followed by an exploration of the downstream pathway, cAMP-dependent protein kinase (PKA).

RESULTS

miR-200b was reduced in lung tissues, PASMCs and macrophages of rats with PAH-like pathology. BMSC-EVs transferred miR-200b into macrophages, and subsequently accelerated their switch to the M2 phenotype and reversed the PAH-associated disorders. Furthermore, miR-200b carried by BMSC-EVs induced PKA phosphorylation by targeting PDE1A, thereby expediting macrophage polarization.

CONCLUSION

Our current study highlighted the inhibitory role of BMSC-EV-miR-200b in PAH formation.

In utero delivery of miRNA induces epigenetic alterations and corrects pulmonary pathology in congenital diaphragmatic hernia

Structural fetal diseases, such as congenital diaphragmatic hernia (CDH) can be diagnosed prenatally. Neonates with CDH are healthy in utero as gas exchange is managed by the placenta, but impaired lung function results in critical illness from the time a baby takes its first breath. MicroRNA (miR) 200b and its downstream targets in the TGF-β pathway are critically involved in lung branching morphogenesis. Here, we characterize the expression of miR200b and the TGF-β pathway at different gestational times using a rat model of CDH. Fetal rats with CDH are deficient in miR200b at gestational day 18. We demonstrate that novel polymeric nanoparticles loaded with miR200b, delivered in utero via vitelline vein injection to fetal rats with CDH results in changes in the TGF-β pathway as measured by qRT-PCR; these epigenetic changes improve lung size and lung morphology, and lead to favorable pulmonary vascular remodeling on histology. This is the first demonstration of in utero epigenetic therapy to improve lung growth and development in a pre-clinical model. With refinement, this technique could be applied to fetal cases of CDH or other forms of impaired lung development in a minimally invasive fashion.

Role of microRNAs in Congenital Diaphragmatic Hernia-Associated Pulmonary Hypertension

Epigenetic regulators such as microRNAs (miRNAs) have a key role in modulating several gene expression pathways and have a role both in lung development and function. One of the main pathogenetic determinants in patients with congenital diaphragmatic hernia (CDH) is pulmonary hypertension (PH), which is directly related to smaller lung size and pulmonary microarchitecture alterations. The aim of this review is to highlight the importance of miRNAs in CDH-related PH and to summarize the results covering this topic in animal and human CDH studies. The focus on epigenetic modulators of CDH-PH offers the opportunity to develop innovative diagnostic tools and novel treatment modalities, and provides a great potential to increase researchers’ understanding of the pathophysiology of CDH.

Foetal genome editing

PURPOSE OF REVIEW

The development of modern gene editing tools alongside promising innovations in gene sequencing and prenatal diagnostics as well as a shifting regulatory climate around targeted therapeutics offer an opportunity to address monogenic diseases prior to the onset of pathology. In this review, we seek to highlight recent progress in preclinical studies evaluating the potential in-utero gene editing as a treatment for monogenic diseases that cause morbidity or mortality before or shortly after birth.

RECENT FINDINGS

There has been significant recent progress in clinical trials for postnatal gene editing. Corresponding advances have been made with respect to in-utero cell and enzyme replacement therapies. These precedents establish the foundation for 'one-shot' treatments by way in-utero gene editing. Compelling preclinical data in liver, pulmonary and multisystemic diseases demonstrate the potential benefits of in-utero editing approaches.

SUMMARY

Recent proof-of-concept studies have demonstrated the safety and feasibility of in-utero gene editing across multiple organ systems and in numerous diseases. Clinical translation will require continued evolution of vectors and editing approaches to maximize efficiency and minimize unwanted treatment effects.

Ductus arteriosus flow predicts outcome in neonates with congenital diaphragmatic hernia

OBJECTIVE

To investigate whether the pattern of flow through the ductus arteriosus (DA) is associated with the need for extracorporeal membrane oxygenation support (ECMO) or death in neonates with congenital diaphragmatic hernia (CDH).

DESIGN

Retrospective observational study.

SETTING

German level III Neonatal Intensive Care Unit.

PARTICIPANTS

One hundred and nine CDH neonates were born between March 2009 and May 2021.

METHODS

DA flow pattern was assessed in echocardiograms obtained within 24 h of life by measuring flow time and velocity time integral (VTI) for both left-to-right (LR) and right-to-left (RL) components of the ductal shunt. A VTI ratio (VTILR/VTIRL) < 1.0 and an RL relative flow time (flow timeRL/(Flow timeLR+Flow timeRL)) >33% were defined as markers of abnormal flow patterns. The primary outcome was the need for ECMO. The secondary outcome was death.

RESULTS

Seventy-two patients (51.8%) had a VTI ratio <1.0, 73 (52.5%) an RL relative flow time >33%. Fifty-nine patients (42.4%) had an alteration of both values. Need for ECMO was present in 37.4% (n = 52), while 19.4% (n = 27) died. A VTI ratio <1.0 had the highest diagnostic accuracy for the need for ECMO, (sensitivity 82.7%, specificity 66.7%, negative predictive value [NPV] 86.6%, and positive predictive value [PPV] 59.7%) as well as for death (sensitivity 77.8%, specificity 54.5%, NPV 91.0%, and PPV 29.2%). Patients with VTI ratio <1.0 were 4.7 times more likely to need ECMO and 3.3 times more likely to die. VTI ratio values correlated significantly with pulmonary hypertension (PH) severity (r = -0.516, p < 0.001).

CONCLUSIONS

A VTI ratio <1.0 is a valuable threshold to identify high-risk CDH neonates. For improved risk stratification, other parameters-for example, left ventricular cardiac dysfunction-should be combined with DA flow assessment.

Gestational Diabetes Mellitus Impedes Fetal Lung Development Through Exosome-Dependent Crosstalk Between Trophoblasts and Lung Epithelial Cells

Background

Fetal lung underdevelopment (FLUD) is associated with neonatal and childhood severe respiratory diseases, among which gestational diabetes mellitus (GDM) play crucial roles as revealed by recent prevalence studies, yet mechanism underlying GDM-induced FLUD, especially the role of trophoblasts, is not all known.

Methods

From the perspective of trophoblast-derived exosomes, we established in vitro, ex vivo, in vivo and GDM trophoblast models. Utilizing placenta-derived exosomes (NUB-exos and GDMUB-exos) isolated from normal and GDM umbilical cord blood plasma and trophoblast-derived exosomes (NC-exos and HG-exos) isolated from HTR8/SVneo trophoblasts medium with/without high glucose treatment, we examined their effects on fetal lung development and biological functions.

Results

We found that, compared with the NUB-exos group, the exosome concentration increased in GDMUB-exos group, and the content of exosomes also changed evidenced by 61 dysregulated miRNAs. After applying these exosomes to A549 alveolar type II epithelial cells, the proliferation and biological functions were suppressed while the proportion of apoptotic cells was increased as compared to the control. In ex vivo studies, we found that GDMUB-exos showed significant suppression on the growth of the fetal lung explants, where the number of terminal buds and the area of explant surface decreased and shrank. Besides, the expression of Fgf10, Vegfa, Flt-1, Kdr and surfactant proteins A, B, C, and D was downregulated in GDMUB-exos group, whilst Sox9 was upregulated. For in vivo studies, we found significant suppression of fetal lung development in GDMUB-exos group. Importantly, we found consistent alterations when we used NC-exos and HG-exos, suggesting a dominant role of trophoblasts in placenta-derived exosome-induced FLUD.

Conclusion

In conclusion, GDM can adversely affect trophoblasts and alter exosome contents, causing crosstalk disorder between trophoblasts and fetal lung epithelial cells and finally leading to FLUD. Findings of this study will shine insight into the theoretical explanation for the pathogenesis of FLUD.

Intraluminal chloride regulates lung branching morphogenesis: involvement of PIEZO1/PIEZO2

BACKGROUND

Clinical and experimental evidence shows lung fluid volume as a modulator of fetal lung growth with important value in treating fetal lung hypoplasia. Thus, understanding the mechanisms underlying these morphological dynamics has been the topic of multiple investigations with, however, limited results, partially due to the difficulty of capturing or recapitulating these movements in the lab. In this sense, this study aims to establish an ex vivo model allowing the study of lung fluid function in branching morphogenesis and identify the subsequent molecular/ cellular mechanisms.

METHODS

Ex vivo lung explant culture was selected as a model to study branching morphogenesis, and intraluminal injections were performed to change the composition of lung fluid. Distinct chloride (Cl^-) concentrations (5.8, 29, 143, and 715 mM) or Cl^- channels inhibitors [antracene-9-carboxylic acid (A9C), cystic fibrosis transmembrane conductance regulator inhibitor172 (CFTRinh), and calcium-dependent Cl^- channel inhibitorA01 (CaCCinh)] were injected into lung lumen at two timepoints, day0 (D0) and D2. At D4, morphological and molecular analyses were performed in terms of branching morphogenesis, spatial distribution (immunofluorescence), and protein quantification (western blot) of mechanoreceptors (PIEZO1 and PIEZO2), neuroendocrine (bombesin, ghrelin, and PGP9.5) and smooth muscle [alpha-smooth muscle actin (α-SMA) and myosin light chain 2 (MLC2)] markers.

RESULTS

For the first time, we described effective intraluminal injections at D0 and D2 and demonstrated intraluminal movements at D4 in ex vivo lung explant cultures. Through immunofluorescence assay in in vivo and ex vivo branching morphogenesis, we show that PGP9.5 colocalizes with PIEZO1 and PIEZO2 receptors. Fetal lung growth is increased at higher [Cl^-], 715 mM Cl^-, through the overexpression of PIEZO1, PIEZO2, ghrelin, bombesin, MLC2, and α-SMA. In contrast, intraluminal injection of CFTRinh or CaCCinh decreases fetal lung growth and the expression of PIEZO1, PIEZO2, ghrelin, bombesin, MLC2, and α-SMA. Finally, the inhibition of PIEZO1/PIEZO2 by GsMTx4 decreases branching morphogenesis and ghrelin, bombesin, MLC2, and α-SMA expression in an intraluminal injection-independent manner.

CONCLUSIONS

Our results identify PIEZO1/PIEZO2 expressed in neuroendocrine cells as a regulator of fetal lung growth induced by lung fluid.

Congenital lung malformations: Dysregulated lung developmental processes and altered signaling pathways

Congenital lung malformations comprise a diverse group of anomalies including congenital pulmonary airway malformation (CPAM, previously known as congenital cystic adenomatoid malformation or CCAM), bronchopulmonary sequestration (BPS), congenital lobar emphysema (CLE), bronchogenic cysts, and hybrid lesions. Little is known about the signaling pathways that underlie the pathophysiology of these lesions and the processes that may promote their malignant transformation. In the last decade, the use of transgenic/knockout animal models and the implementation of next generation sequencing on surgical lung specimens have increased our knowledge on the pathophysiology of these lesions. Herein, we provide an overview of normal lung development in humans and rodents, and we discuss the current state of knowledge on the pathophysiology and molecular pathways that are altered in each congenital lung malformation.

Autophagy is Impaired in Fetal Hypoplastic Lungs and Rescued by Administration of Amniotic Fluid Stem Cell Extracellular Vesicles

RATIONALE

Pulmonary hypoplasia secondary to congenital diaphragmatic hernia (CDH) is characterized by reduced branching morphogenesis, which is responsible for poor clinical outcomes. Administration of amniotic fluid stem cell extracellular vesicles (AFSC-EVs) rescues branching morphogenesis in rodent fetal models of pulmonary hypoplasia. Herein, we hypothesized that AFSC-EVs exert their regenerative potential by affecting autophagy, a process required for normal lung development.

OBJECTIVES

To evaluate autophagy in hypoplastic lungs throughout gestation and establish whether AFSC-EV administration improves branching morphogenesis through autophagy-mediated mechanisms.

METHODS

EVs were isolated from c-kit+ AFSC conditioned medium by ultracentrifugation and characterized by size, morphology, and EV marker expression. Branching morphogenesis was inhibited in rat fetuses by nitrofen administration to dams and in human fetal lung explants by blocking RAC1 activity with NSC23766. Expression of autophagy activators (BECN1 and ATG5) and adaptor (SQSTM1) was analyzed in vitro (rat and human fetal lung explants) and in vivo (rat fetal lungs). Mechanistic studies on rat fetal primary lung epithelial cells were conducted using inhibitors for microRNA-17 and -20a contained in the AFSC-EV cargo and known to regulate autophagy.

MEASUREMENTS AND MAIN RESULTS

Rat and human models of fetal pulmonary hypoplasia showed reduced autophagy at different developmental stages. AFSC-EV administration restored autophagy levels in both pulmonary hypoplasia models by transferring miR-17~92 cluster members contained in the EV cargo.

CONCLUSIONS

AFSC-EV treatment rescues branching morphogenesis partly by restoring autophagy through miRNA cargo transfer. This study enhances our understanding of pulmonary hypoplasia pathogenesis and creates new opportunities for fetal therapeutic intervention in CDH babies. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a rare birth defect characterized by incomplete closure of the diaphragm and herniation of fetal abdominal organs into the chest that results in pulmonary hypoplasia, postnatal pulmonary hypertension owing to vascular remodelling and cardiac dysfunction. The high mortality and morbidity rates associated with CDH are directly related to the severity of cardiopulmonary pathophysiology. Although the aetiology remains unknown, CDH has a polygenic origin in approximately one-third of cases. CDH is typically diagnosed with antenatal ultrasonography, which also aids in risk stratification, alongside fetal MRI and echocardiography. At specialized centres, prenatal management includes fetal endoscopic tracheal occlusion, which is a surgical intervention aimed at promoting lung growth in utero. Postnatal management focuses on cardiopulmonary stabilization and, in severe cases, can involve extracorporeal life support. Clinical practice guidelines continue to evolve owing to the rapidly changing landscape of therapeutic options, which include pulmonary hypertension management, ventilation strategies and surgical approaches. Survivors often have long-term, multisystem morbidities, including pulmonary dysfunction, gastroesophageal reflux, musculoskeletal deformities and neurodevelopmental impairment. Emerging research focuses on small RNA species as biomarkers of severity and regenerative medicine approaches to improve fetal lung development.

Tenascin C is dysregulated in hypoplastic lungs of miR-200b-/- mice

PURPOSE

We previously demonstrated that absence of miR-200b results in abnormal lung development in congenital diaphragmatic hernia due to imbalance between epithelial and mesenchymal cells. Tenascin C is a highly conserved extracellular matrix protein involved in epithelial to mesenchymal transition, tissue regeneration and lung development. Considering the involvement of Tenascin C and miR-200b and their potential interaction, we aimed to study Tenascin C during lung development in the absence of miR-200b.

METHODS

We collected lungs of miR-200b^-/- mice (male, 8 weeks). We performed Western blot (WB) analysis (N = 6) and immunofluorescence (N = 5) for Tenascin C and alpha smooth muscle actin and RT-qPCR for Tenascin C gene expression (N = 4).

RESULTS

Using WB analysis, we observed a decreased total protein abundance of Tenascin C in miR-200b^-/- lungs (miR-200b^+/+: 3.8 × 10⁷ ± 1 × 10⁷; miR-200b^-/-: 1.9 × 10⁷ ± 5 × 10⁶; p = 0.002). Immunofluorescence confirmed decreased total Tenascin C in miR-200b^-/- lungs. Tenascin C was significantly decreased in the mesenchyme but relatively increased in the airways of mutant lungs. Total lung RNA expression of Tenascin C was higher in miR-200b^-/- lungs.

CONCLUSION

We report dysregulation of Tenascin C in lungs of miR-200b^-/- mice. This suggests that absence of miR-200b results in abnormal Tenascin C abundance contributing to the lung hypoplasia observed in miR-200b^-/- mice.

Antenatal Management of Congenital Diaphragmatic Hernia: what's next ?

Congenital diaphragmatic hernia (CDH) can be diagnosed in the prenatal period and its severity can be measured by fetal imaging. There is now level I evidence that, in selected cases, Fetoscopic Endoluminal Tracheal Occlusion (FETO) increases survival to discharge from the neonatal unit as well as the risk for prematurity. Both effects are dependent on the time point of tracheal occlusion. FETO may also lead to iatrogenic death when done in unexperienced centres. The implementation of the findings from our clinical studies, may also vary based on local conditions. These may be different in terms of available skill set, access to fetal therapy, as well as outcome based on local neonatal management. We encourage prior benchmarking of local outcomes with optimal postnatal management, based on large enough numbers and using identical criteria as in the recent trials. We propose to work further on prenatal prediction methods, and the improvement of fetal intervention. In this manuscript, we describe a research agenda from a fetal medicine perspective. This research should be in parallel with innovation in neonatal and pediatric (surgical) management of this condition. This article is protected by copyright. All rights reserved.

Fetal lung regeneration using stem cell-derived extracellular vesicles: A new frontier for pulmonary hypoplasia secondary to congenital diaphragmatic hernia

The poor outcomes of babies with congenital diaphragmatic hernia (CDH) are directly related to pulmonary hypoplasia, a cosndition characterized by impaired lung development. Although the pathogenesis of pulmonary hypoplasia is not fully elucidated, there is now evidence that CDH patients have missing or dysregulated microRNAs (miRNAs) that regulate lung development. A prenatal therapy that supplements these missing/dysregulated miRNAs could be a strategy to rescue normal lung development. Extracellular vesicles (EVs), also known as exosomes when of small dimensions, are lipid-bound nanoparticles that can transfer their heterogeneous cargo (proteins, lipids, small RNAs) to target cells to induce biological responses. Herein, we review all studies that show evidence for stem cell-derived EVs as a regenerative therapy to rescue normal development in CDH fetal lungs. Particularly, we report studies showing that administration of EVs derived from amniotic fluid stem cells (AFSC-EVs) to models of pulmonary hypoplasia promotes fetal lung growth and maturation via transfer of miRNAs that are known to regulate lung developmental processes. We also describe that stem cell-derived EVs exert effects on vascular remodeling, thus possibly preventing postnatal pulmonary hypertension. Finally, we discuss future perspectives and challenges to translate this promising stem cell EV-based therapy to clinical practice. This article is protected by copyright. All rights reserved.

The heart in congenital diaphragmatic hernia: Knowns, unknowns, and future priorities

There is growing recognition that the heart is a key contributor to the pathophysiology of congenital diaphragmatic hernia (CDH), in conjunction with developmental abnormalities of the lung and pulmonary vasculature. Investigations to date have demonstrated altered fetal cardiac morphology, notably relative hypoplasia of the fetal left heart, as well as early postnatal right and left ventricular dysfunction which appears to be independently associated with adverse outcomes. However, many more unknowns remain, not least an understanding of the genetic and cellular basis for cardiac dysplasia and dysfunction in CDH, the relationship between fetal, postnatal and long-term cardiac function, and the impact on other parts of the body especially the developing brain. Consensus on how to measure and classify cardiac function and pulmonary hypertension in CDH is also required, potentially using both non-invasive imaging and biomarkers. This may allow routine assessment of the relative contribution of cardiac dysfunction to individual patient pathophysiological phenotype and enable better, individualized therapeutic strategies incorporating targeted use of fetal therapies, cardiac pharmacotherapies, and extra-corporeal membrane oxygenation (ECMO). Collaborative, multi-model approaches are now required to explore these unknowns and fully appreciate the role of the heart in CDH.

Developmental Pathways Underlying Lung Development and Congenital Lung Disorders

Lung organogenesis is a highly coordinated process governed by a network of conserved signaling pathways that ultimately control patterning, growth, and differentiation. This rigorously regulated developmental process culminates with the formation of a fully functional organ. Conversely, failure to correctly regulate this intricate series of events results in severe abnormalities that may compromise postnatal survival or affect/disrupt lung function through early life and adulthood. Conditions like congenital pulmonary airway malformation, bronchopulmonary sequestration, bronchogenic cysts, and congenital diaphragmatic hernia display unique forms of lung abnormalities. The etiology of these disorders is not yet completely understood; however, specific developmental pathways have already been reported as deregulated. In this sense, this review focuses on the molecular mechanisms that contribute to normal/abnormal lung growth and development and their impact on postnatal survival.

Fetal lung underdevelopment is rescued by administration of amniotic fluid stem cell extracellular vesicles in rodents

Fetal lung underdevelopment, also known as pulmonary hypoplasia, is characterized by decreased lung growth and maturation. The most common birth defect found in babies with pulmonary hypoplasia is congenital diaphragmatic hernia (CDH). Despite research and clinical advances, babies with CDH still have high morbidity and mortality rates, which are directly related to the severity of lung underdevelopment. To date, there is no effective treatment that promotes fetal lung growth and maturation. Here, we describe a stem cell-based approach in rodents that enhances fetal lung development via the administration of extracellular vesicles (EVs) derived from amniotic fluid stem cells (AFSCs). Using fetal rodent models of pulmonary hypoplasia (primary epithelial cells, organoids, explants, and in vivo), we demonstrated that AFSC-EV administration promoted branching morphogenesis and alveolarization, rescued tissue homeostasis, and stimulated epithelial cell and fibroblast differentiation. We confirmed this regenerative ability in in vitro models of lung injury using human material, where human AFSC-EVs obtained following good manufacturing practices restored pulmonary epithelial homeostasis. Investigating EV mechanism of action, we found that AFSC-EV beneficial effects were exerted via the release of RNA cargo. MicroRNAs regulating the expression of genes involved in lung development, such as the miR17-92 cluster and its paralogs, were highly enriched in AFSC-EVs and were increased in AFSC-EV-treated primary lung epithelial cells compared to untreated cells. Our findings suggest that AFSC-EVs hold regenerative ability for underdeveloped fetal lungs, demonstrating potential for therapeutic application in patients with pulmonary hypoplasia.

Nanoparticles for delivery of agents to fetal lungs

Fetal treatment of congenital lung disease, such as cystic fibrosis, surfactant protein syndromes, and congenital diaphragmatic hernia, has been made possible by improvements in prenatal diagnostic and interventional technology. Delivery of therapeutic agents to fetal lungs in nanoparticles improves cellular uptake. The efficacy and safety of nanoparticle-based fetal lung therapy depends on targeting of necessary cell populations. This study aimed to determine the relative distribution of nanoparticles of a variety of compositions and sizes in the lungs of fetal mice delivered through intravenous and intra-amniotic routes. Intravenous delivery of particles was more effective than intra-amniotic delivery for epithelial, endothelial and hematopoietic cells in the fetal lung. The most effective targeting of lung tissue was with 250nm Poly-Amine-co-Ester (PACE) particles accumulating in 50% and 44% of epithelial and endothelial cells. This study demonstrated that route of delivery and particle composition impacts relative cellular uptake in fetal lung, which will inform future studies in particle-based fetal therapy.

Pulmonary hypertension is an important co-morbidity in developmental lung diseases of infancy: Bronchopulmonary dysplasia and congenital diaphragmatic hernia

Bronchopulmonary dysplasia (BPD) following preterm birth and congenital diaphragmatic hernia (CDH) are both forms of developmental lung disease that may result in persistent pulmonary and pulmonary vascular morbidity in childhood. The pulmonary vascular disease (PVD) which accompanies BPD and CDH is due to developmental abnormalities and ongoing perinatal insults. This may be accompanied by evidence of elevated right heart pressures and pulmonary vascular resistance, leading to diagnosis of pulmonary hypertension (PH). The development of PH in these conditions is associated with increased morbidity and mortality in the vulnerable BPD and CDH populations. We present a review of PVD pathogenesis and evaluation in BPD and CDH and discuss management of related sequelae of PH co-morbidity for affected infants.

Epithelial cell-adhesion protein cadherin 26 is dysregulated in congenital diaphragmatic hernia and congenital pulmonary airway malformation

BACKGROUND

Congenital diaphragmatic hernia (CDH) and congenital pulmonary airway malformation (CPAM) are two inborn pathologies of the lung of unknown origin. Alterations of gene expression in airway epithelial cells are involved in the pathobiology of both diseases. We previously found decreased expression of the epithelial cell adhesion protein cadherin 26 (CDH26) in hypoplastic mice lungs. Here, our objective was to describe the expression and localization of CDH26 in hypoplastic CDH lungs and hyperproliferative CPAM tissues.

METHODS

After ethical approval, we used human lung tissues from CDH and CPAM cases and age-matched control samples from a previously established biobank. Furthermore, lungs from the nitrofen rat model of CDH were included in the study. We performed immunohistochemistry and western blot analysis with antibodies against CDH26 to examine protein localization and abundance. Statistical analysis was performed using Mann-Whitney U test with significance set at p < 0.05.

RESULTS

We observed an overexpression of CDH26 within the epithelium of cystic CPAM lesions compared to normal airways within the same lung and compared to control lungs. Western blot demonstrated a downregulation of CDH26 in the nitrofen rat model of CDH compared to healthy controls. Immunohistochemistry could not show consistent differences between CDH and control in human and rat lungs. In the studied human lung samples, CDH26 was localized to the apical part of the airway epithelial cells.

CONCLUSION

CDH26 is differentially expressed in human CPAM lung tissues and may be downregulated in nitrofen-induced hypoplastic rat lungs compared to control lungs. Disruption of CDH26 associated pathways in lung development may be involved in the pathogenesis of lung hypoplasia or cystic lung disease.

Unraveling the Genetics of Congenital Diaphragmatic Hernia: An Ongoing Challenge

Congenital diaphragmatic hernia (CDH) is a congenital structural anomaly in which the diaphragm has not developed properly. It may occur either as an isolated anomaly or with additional anomalies. It is thought to be a multifactorial disease in which genetic factors could either substantially contribute to or directly result in the developmental defect. Patients with aneuploidies, pathogenic variants or de novo Copy Number Variations (CNVs) impacting specific genes and loci develop CDH typically in the form of a monogenetic syndrome. These patients often have other associated anatomical malformations. In patients without a known monogenetic syndrome, an increased genetic burden of de novo coding variants contributes to disease development. In early years, genetic evaluation was based on karyotyping and SNP-array. Today, genomes are commonly analyzed with next generation sequencing (NGS) based approaches. While more potential pathogenic variants are being detected, analysis of the data presents a bottleneck-largely due to the lack of full appreciation of the functional consequence and/or relevance of the detected variant. The exact heritability of CDH is still unknown. Damaging de novo alterations are associated with the more severe and complex phenotypes and worse clinical outcome. Phenotypic, genetic-and likely mechanistic-variability hampers individual patient diagnosis, short and long-term morbidity prediction and subsequent care strategies. Detailed phenotyping, clinical follow-up at regular intervals and detailed registries are needed to find associations between long-term morbidity, genetic alterations, and clinical parameters. Since CDH is a relatively rare disorder with only a few recurrent changes large cohorts of patients are needed to identify genetic associations. Retrospective whole genome sequencing of historical patient cohorts using will yield valuable data from which today's patients and parents will profit Trio whole genome sequencing has an excellent potential for future re-analysis and data-sharing increasing the chance to provide a genetic diagnosis and predict clinical prognosis. In this review, we explore the pitfalls and challenges in the analysis and interpretation of genetic information, present what is currently known and what still needs further study, and propose strategies to reap the benefits of genetic screening.

miR-200 family expression during normal and abnormal lung development due to congenital diaphragmatic hernia at the later embryonic stage in the nitrofen rat model

INTRODUCTION

Congenital diaphragmatic hernia (CDH) is a life-threatening disease associated with pulmonary hypoplasia. CDH occurs approximately 1 in every 2000-3000 live births, and the pathophysiology is unknown. MicroRNAs are short, non-coding RNAs that control gene expression through post-transcriptional regulation. Based on our previous work, we hypothesized that the miR-200 family is differentially expressed in normal and abnormal lung development. We aimed to examine the expression of the miR-200 family during normal and hypoplastic lung development due to CDH.

METHODS

We performed reverse transcriptase polymerase chain reaction (RT-qPCR) and fluorescent in situ hybridization (FISH) to study the expression levels and distribution of the miR-200 family members on embryonic day 21 (E21) rat control and nitrofen-induced hypoplastic CDH lungs.

RESULTS

RT-qPCR showed up-regulation of miR-200a in hypoplastic CDH lungs. FISH showed contrasting expression patterns for miR- 200a, miR-200c, and miR-429 between control and hypoplastic CDH lungs, while we could not detect miR-141 in control and hypoplastic CDH lungs.

CONCLUSION

We demonstrate a specific expression pattern of miR-200 family members in hypoplastic CDH lungs different from control lungs. This study suggests that disruption of miR-200 family expression plays a role in the pathogenesis of pulmonary hypoplasia associated with CDH.

The Role of miR-200b-3p in Modulating TGF-β1-induced Injury in Human Bronchial Epithelial Cells

BACKGROUND

Dysregulation of microRNAs (miRNAs) has been implicated in airway diseases where transforming growth factor-β (TGF-β)-induced epithelial-mesenchymal transition (EMT) may contribute to pathophysiology. Our study investigated the role of miRNA-200b in TGF-β1-induced EMT in human bronchial epithelial cells.

METHODS

NanoString nCounter miRNA assay was used to profile miRNA in control versus TGF-β1 (1, 4, and 24 h) stimulated BEAS-2B cells. Immortalized primary bronchial epithelial cell line (BEAS-2B cells), human primary bronchial epithelial cells (PBECs), and PBECs derived post-lung transplant were transfected with miR-200b-3p mimics and EMT marker expression was examined at RNA and protein level. miRNA target studies were performed and validated using computational tools and luciferase assay. In situ hybridization was done on normal lung tissue to localize miR-200b-3p in airway epithelium.

RESULTS

miR-200b-3p was downregulated post-TGF-β1 treatment compared with control in BEAS-2B. miR-200b-3p mimic transfection before TGF-β1 stimulation maintained epithelial marker expression and downregulated mesenchymal cell markers at RNA and protein level in BEAS-2B cells and PBECs. Furthermore, miR-200b-3p mimics reversed established TGF-β1-induced EMT in BEAS-2B cells. miR-200b-3p targets, ZNF532, and ZEB2 were validated as direct targets using luciferase assay. miR-200b-3p mimics suppress TGF-β1-induced EMT via inhibition of ZNF532 and ZEB2. In situ hybridization showed that miR-200b-3p is expressed in the normal lung epithelium. Additionally, miR-200b-3p mimics inhibit EMT in the presence of TGF-β1 in PBECs derived from lung allograft.

CONCLUSIONS

We provide proof of concept that miR-200b-3p protects airway epithelial cells from EMT. Manipulating miR-200b-3p expression may represent a novel therapeutic modulator in airway pathophysiology.

Congenital diaphragmatic hernia: current management strategies from antenatal diagnosis to long-term follow-up

Congenital diaphragmatic hernia (CDH) is a developmental birth defect consisting of a diaphragmatic defect and abnormal lung development. CDH complicates 2.3-2.8 per 10,000 live births. Despite efforts to standardize clinical practice, management of CDH remains challenging. Frequent re-evaluation of clinical practices in CDH reveals that management of CDH is evolving from one of postnatal stabilization to prenatal optimization. Translational research reveals promising avenues for in utero therapeutic intervention, including fetoscopic endoluminal tracheal occlusion. These remain highly experimental and demand improved antenatal diagnostics. Timely diagnosis of CDH and identification of severely affected fetuses allow time for delivery planning or in utero therapeutics. Optimal perinatal care and surgical treatment strategies are highly debated. Improved CDH mortality rates have placed increased emphasis on identifying and monitoring the long-term sequelae of disease throughout childhood and into adulthood. We review the current management strategies for CDH, highlighting where progress has been made, and where future developments have the potential to revolutionize care in this vulnerable patient population.

Congenital diaphragmatic hernia-associated pulmonary hypertension

Congenital diaphragmatic hernia (CDH) is a neonatal pathology in which intrathoracic herniation of abdominal viscera via diaphragmatic defect results in aberrant pulmonary and cardiovascular development. Despite decades of study and many advances in the diagnosis and treatment of CDH, morbidity and mortality remain high, largely due to pulmonary hypertension (PH), along with pulmonary hypoplasia and cardiac dysfunction. In patients with CDH, hypoplastic pulmonary vasculature and alterations in multiple molecular pathways lead to pathophysiologic pulmonary vasculopathy and, for severe CDH, sustained, elevated pulmonary arterial pressures. This review addresses the multiple anatomic and physiologic changes that underlie CDH-associated PH (CDH-PH), along with the multimodal treatment strategies that exist currently and future therapies currently under investigation.

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.

MiR-130a-5p/Foxa2 axis modulates fetal lung development in congenital diaphragmatic hernia by activating the Shh/Gli1 signaling pathway

AIMS

Congenital diaphragmatic hernia (CDH) is a lethal birth defect characterized by congenital lung malformation, and the severity of pulmonary hypoplasia directly affects the prognosis of infants with CDH. Using a nitrofen-induced CDH rat model, we previously reported that Foxa2 expression was downregulated in CDH lungs by proteomics analysis. Here, we investigate the role of miR-130a-5p/Foxa2 axis in lung development of the nitrofen-induced CDH and evaluate its potential role in vivo prenatal therapy.

MAIN METHODS

Nitrofen was orally administrated on embryonic day (E) 8.5 to establish a rat CDH model, and fetal lungs were collected on E13.5, E15.5, E17.5, E19.5 and E21.5. The binding sites of miR-130a-5p on Foxa2 mRNA were identified using bioinformatics prediction software and were validated via luciferase assay. The expression levels of miR-130a-5p and Foxa2 were detected using qRT-PCR, ISH, IHC and western blotting. The role of miR-130a-5p/Foxa2 axis in CDH-associated lung development was investigated in ex vivo lung explants.

KEY FINDINGS

We found that Foxa2 was downregulated in CDH lung tissues, and Foxa2 upregulating improved CDH branching morphogenesis in ex vivo lung explants. Meanwhile, we also showed that miR-130a-5p was significantly upregulated in CDH lungs and thus inversely correlated with Foxa2. Increasing miR-130a-5p abundance with mimics decreases Foxa2-driven Shh/Gli1 signaling and inhibits branching morphogenesis in ex vivo lung explants.

SIGNIFICANCE

This study was the first to show that the miR-130a-5p/Foxa2 axis played a crucial role in CDH-associated pulmonary hypoplasia. These findings may provide relevant insights into the prenatal diagnosis and prenatal therapy of CDH.

First steps in the development of a liquid biopsy in situ hybridization protocol to determine circular RNA biomarkers in rat biofluids

PURPOSE

Epigenetic factors are involved in the pathogenesis of congenital diaphragmatic hernia (CDH). Circular RNAs (circRNAs) are epigenetic regulators amenable to biomarker profiling. Here, we aimed to develop a liquid biopsy protocol to detect pathognomonic circRNA changes in biofluids.

METHODS

Our protocol is adapted from the existing BaseScope™ in situ hybridization technique. Rat biofluids were fixed in a gelatin-coated 96-well plate with formalin. Probes were designed to target circRNAs with significant fold change in nitrofen-induced CDH. FastRED fluorescence was assessed using a plate reader and confirmed with confocal microscopy. We tested maternal serum and amniotic fluid samples from control and nitrofen-treated rats.

RESULTS

We detected circRNAs in rat serum and amniotic fluid from control and CDH (nitrofen-treated) rats using fluorescent readout. CircRNA signal was observed in fixed biofluids as fluorescent punctate foci under confocal laser scanning microscopy. This was confirmed by comparison to BaseScope™ lung tissue sections. Signal was concentration dependent and DNase resistant.

CONCLUSION

We successfully adapted BaseScope™ to detect circRNAs in rat biofluids: serum and amniotic fluid. We detected signal from probes targeted to circRNAs that are dysregulated in rat CDH. This work establishes the preliminary feasibility of circRNA detection in prenatal diagnostics.

Prenatal maternal biomarkers for the early diagnosis of congenital malformations: A review

Congenital anomalies cause ~7% of all neonatal deaths, many of which have no identified pathophysiological cause. Because accurate and robust laboratory tests are unavailable for most birth defects, physicians rely on imaging such as ultrasound and MRI. Biomarkers from human body fluids are considered a powerful diagnostic tool to assess human disease and health as it mirrors an individual's condition. Minimally invasive 'liquid biopsies' from blood samples are highly valuable for diagnosis, prognosis, risk assessment, and treatment of many conditions. Recent large-scale analysis ('omics') have enabled researchers to identify novel biomarkers in different areas. To accurately facilitate the early detection of congenital anomalies, the identification of biomarkers from maternal plasma should be promoted. This approach will uncover new opportunities in prenatal diagnosing and likely lead to a better understanding of the pathogenesis of congenital anomalies.

Recent advances in our understanding of the mechanisms of lung alveolarization and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common cause of morbidity and mortality in preterm infants. A key histopathological feature of BPD is stunted late lung development, where the process of alveolarization-the generation of alveolar gas exchange units-is impeded, through mechanisms that remain largely unclear. As such, there is interest in the clarification both of the pathomechanisms at play in affected lungs, and the mechanisms of de novo alveoli generation in healthy, developing lungs. A better understanding of normal and pathological alveolarization might reveal opportunities for improved medical management of affected infants. Furthermore, disturbances to the alveolar architecture are a key histopathological feature of several adult chronic lung diseases, including emphysema and fibrosis, and it is envisaged that knowledge about the mechanisms of alveologenesis might facilitate regeneration of healthy lung parenchyma in affected patients. To this end, recent efforts have interrogated clinical data, developed new-and refined existing-in vivo and in vitro models of BPD, have applied new microscopic and radiographic approaches, and have developed advanced cell-culture approaches, including organoid generation. Advances have also been made in the development of other methodologies, including single-cell analysis, metabolomics, lipidomics, and proteomics, as well as the generation and use of complex mouse genetics tools. The objective of this review is to present advances made in our understanding of the mechanisms of lung alveolarization and BPD over the period 1 January 2017-30 June 2019, a period that spans the 50th anniversary of the original clinical description of BPD in preterm infants.

Surgical technique for developing a rabbit model of congenital diaphragmatic hernia and tracheal occlusion

The surgical model of congenital diaphragmatic hernia (CDH) has been utilized in exploring treatments and innovative therapies, such as tracheal occlusion (TO). The rabbit is an excellent surgical model compared to others due to lower cost, ease of care, short gestational period, and large litter size. This model is also ideal in studying lung hypoplasia of CDH because rabbit lung development is most similar to humans as alveolarization begins prior to birth and continues post-natally. However, the surgical technique in creating a rabbit model of CDH is quite difficult and information is lacking on how to establish this model. Therefore, the aim of this paper is to describe:

•

Surgical technique in establishing a rabbit model of CDH and TO

•

Perioperative care for pregnant rabbit does

Assessment of the nitrofen model of congenital diaphragmatic hernia and of the dysregulated factors involved in pulmonary hypoplasia

PURPOSE

To study pulmonary hypoplasia (PH) associated with congenital diaphragmatic hernia (CDH), investigators have been employing a fetal rat model based on nitrofen administration to dams. Herein, we aimed to: (1) investigate the validity of the model, and (2) synthesize the main biological pathways implicated in the development of PH associated with CDH.

METHODS

Using a defined strategy, we conducted a systematic review of the literature searching for studies reporting the incidence of CDH or factors involved in PH development. We also searched for PH factor interactions, relevance to lung development and to human PH.

RESULTS

Of 335 full-text articles, 116 reported the incidence of CDH after nitrofen exposure or dysregulated factors in the lungs of nitrofen-exposed rat fetuses. CDH incidence: 54% (27-85%) fetuses developed a diaphragmatic defect, whereas the whole litter had PH in varying degrees. Downregulated signaling pathways included FGF/FGFR, BMP/BMPR, Sonic Hedgehog and retinoid acid signaling pathway, resulting in a delay in early epithelial differentiation, immature distal epithelium and dysfunctional mesenchyme.

CONCLUSIONS

The nitrofen model effectively reproduces PH as it disrupts pathways that are critical for lung branching morphogenesis and alveolar differentiation. The low CDH rate confirms that PH is an associated phenomenon rather than the result of mechanical compression alone.

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.

Circulating microRNAs are associated with Pulmonary Hypertension and Development of Chronic Lung Disease in Congenital Diaphragmatic Hernia

Pulmonary hypertension (PH) contributes to high mortality in congenital diaphragmatic hernia (CDH). A better understanding of the regulatory mechanisms underlying the pathology in CDH might allow the identification of prognostic biomarkers and potential therapeutic targets. We report the results from an expression profiling of circulating microRNAs (miRNAs) in direct post-pulmonary blood flow of 18 CDH newborns. Seven miRNAs differentially expressed in children that either died or developed chronic lung disease (CLD) up to 28 days after birth, compared to those who survived without developing CLD during this period, were identified. Target gene and pathway analyses indicate that these miRNAs functions include regulation of the cell cycle, inflammation and morphogenesis, by targeting molecules responsive to growth factors, cytokines and cellular stressors. Furthermore, we identified hub molecules by constructing a protein-protein interaction network of shared targets, and ranked the relative importance of the identified miRNAs. Our results suggest that dysregulations in miRNAs let-7b-5p, -7c-5p, miR-1307-3p, -185-3p, -8084, -331-3p and -210-3p may be detrimental for the development and function of the lungs and pulmonary vasculature, compromise cardiac function and contribute to the development of CLD in CDH. Further investigation of the biomarker and therapeutic potential of these circulating miRNAs is encouraged.