Can circular RNAs be used as prenatal biomarkers for 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.

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.

Embryology and anatomy of congenital diaphragmatic hernia

Prenatal and postnatal treatment modalities for congenital diaphragmatic hernia (CDH) continue to improve, however patients still face high rates of morbidity and mortality caused by severe underlying persistent pulmonary hypertension and pulmonary hypoplasia. Though the majority of CDH cases are idiopathic, it is believed that CDH is a polygenic developmental defect caused by interactions between candidate genes, as well as environmental and epigenetic factors. However, the origin and pathogenesis of these developmental insults are poorly understood. Further, connections between disrupted lung development and the failure of diaphragmatic closure during embryogenesis have not been fully elucidated. Though several animal models have been useful in identifying candidate genes and disrupted signalling pathways, more studies are required to understand the pathogenesis and to develop effective preventative care. In this article, we summarize the most recent litterature on disrupted embryological lung and diaphragmatic development associated with CDH.

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.

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.