Effect of tracheal occlusion on peripheric pulmonary vessel muscularization in a fetal rabbit model for congenital diaphragmatic hernia

Lung proliferation is dependent on the duration not the timepoint of tracheal occlusion in nitrofen rats with diaphragmatic hernia

OBJECTIVE

Prenatal tracheal occlusion (TO) promotes lung growth and is applied clinically in fetuses with congenital diaphragmatic hernia (CDH). Limited data are available regarding the effect of duration versus timepoint of TO. Our objective was to document the impact of TO on lung development in the near-term period in rats with nitrofen-induced CDH.

METHOD

Nitrofen was administered on embryonic day (ED)9 and fetal TO was performed on ED18.5, 19, or 20 (term = ED22). Sham-operated and untouched littermates served as controls. Lungs were harvested in 0.5-day steps and only fetuses with a left-sided CDH were included in further analyses. Healthy fetuses provided a reference for normal near-term lung development.

RESULTS

Duration of TO in the nitrofen rat model for CDH predicts lung growth in terms of lung-body-weight ratio as well as an increased mRNA level of the proliferation marker Ki67. Longer TO also induced a more complex airway architecture. The timepoint of TO was not predictive of lung growth.

CONCLUSION

In the nitrofen rat model of CDH, a longer period of TO leads to enhanced lung growth and more refined airway architecture.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

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.

Unique Heterogeneous Topological Pattern of the Metabolic Landscape in Rabbit Fetal Lungs following Tracheal Occlusion

INTRODUCTION

Fetal tracheal occlusion (TO) is currently an experimental approach to drive accelerated lung growth. It is stimulated by mechanotransduction that results in increased cellular proliferation and growth. However, it is currently unknown how TO affects the metabolic landscape of fetal lungs.

MATERIALS AND METHODS

TO or sham was performed on fetal rabbits at 26 days followed by lung harvest on day 30. Mass spectrometry was performed to evaluate global metabolic changes. Fluorescence lifetime intensity microscopy (FLIM) was performed to estimate local free/bound NADH relative ratio as an indicator of aerobic glycolysis versus oxidative phosphorylation (glycolysis/OXPHOS).

RESULTS

TO results in a metabolic shift from tricarboxylic acid cycle towards glycolysis. FLIM reveals uniform structures in control lungs characterized by similar ratios of free/bound NADH indicating a homogenous topological pattern. Similar uniform structures are observed in shams with some variability in the glycolysis/OXPHOS ratio. In contrast, lungs following TO demonstrate different types of unique distinct topological zones: one with enlarged alveoli and a shift towards glycolysis; the other maintains balance between glycolysis/OXPHOS similar to control lungs.

CONCLUSION

We demonstrate for the first time a unique variable topological pattern of metabolism in fetal lungs following TO with a wide variation of metabolism between zones.

Suggested Mechanisms of Tracheal Occlusion Mediated Accelerated Fetal Lung Growth: A Case for Heterogeneous Topological Zones

In this article, we report an up-to-date summary on tracheal occlusion (TO) as an approach to drive accelerated lung growth and strive to review the different maternal- and fetal-derived local and systemic signals and mechanisms that may play a significant biological role in lung growth and formation of heterogeneous topological zones following TO. Pulmonary hypoplasia is a condition whereby branching morphogenesis and embryonic pulmonary vascular development are globally affected and is classically seen in congenital diaphragmatic hernia. TO is an innovative approach aimed at driving accelerated lung growth in the most severe forms of diaphragmatic hernia and has been shown to result in improved neonatal outcomes. Currently, most research on mechanisms of TO-induced lung growth is focused on mechanical forces and is viewed from the perspective of homogeneous changes within the lung. We suggest that the key principle in understanding changes in fetal lungs after TO is taking into account formation of unique variable topological zones. Following TO, fetal lungs might temporarily look like a dynamically changing topologic mosaic with varying proliferation rates, dissimilar scale of vasculogenesis, diverse patterns of lung tissue damage, variable metabolic landscape, and different structures. The reasons for this dynamic topological mosaic pattern may include distinct degree of increased hydrostatic pressure in different parts of the lung, dissimilar degree of tissue stress/damage and responses to this damage, and incomparable patterns of altered lung zones with variable response to systemic maternal and fetal factors, among others. The local interaction between these factors and their accompanying processes in addition to the potential role of other systemic factors might lead to formation of a common vector of biological response unique to each zone. The study of the interaction between various networks formed after TO (action of mechanical forces, activation of mucosal mast cells, production and secretion of damage-associated molecular pattern substances, low-grade local pulmonary inflammation, and cardiac contraction-induced periodic agitation of lung tissue, among others) will bring us closer to an appreciation of the biological phenomenon of topological heterogeneity within the fetal lungs.

[Fetoscopic tracheal occlusion for severe congenital diaphragmatic hernia: retrospective study]

BACKGROUND AND OBJECTIVES

The temporary fetal tracheal occlusion performed by fetoscopy accelerates lung development and reduces neonatal mortality. The aim of this paper is to present an anesthetic experience in pregnant women, whose fetuses have diaphragmatic hernia, undergoing fetoscopic tracheal occlusion (FETO).

METHOD

Retrospective, descriptive study, approved by the Institutional Ethics Committee. Data were obtained from medical and anesthetic records.

RESULTS

FETO was performed in 28 pregnant women. Demographic characteristics: age 29.8±6.5; weight 68.64±12.26; ASA I and II. Obstetric: IG 26.1±1.10 weeks (in FETO); 32.86±1.58 (reversal of occlusion); 34.96±2.78 (delivery). Delivery: cesarean section, vaginal delivery. Fetal data: Weight (g) in the occlusion and delivery times, respectively (1045.82±222.2 and 2294±553); RPC in FETO and reversal of occlusion: 0.7±0.15 and 1.32±0.34, respectively. Preoperative maternal anesthesia included ranitidine and metoclopramide, nifedipine (VO) and indomethacin (rectal). Preanesthetic medication with midazolam IV. Anesthetic techniques: combination of 0.5% hyperbaric bupivacaine (5-10mg) and sufentanil; continuous epidural predominantly with 0.5% bupivacaine associated with sufentanil, fentanyl, or morphine; general. In 8 cases, there was need to complement via catheter, with 5 submitted to PC and 3 to BC. Thirteen patients required intraoperative sedation; ephedrine was used in 15 patients. Fetal Anesthesia: fentanyl 10 to 20mg·kg^-1 and pancuronium 0,1-0,2mg·kg^-1 (IM). Neonatal survival rate was 60.7%.

CONCLUSION

FETO is a minimally invasive technique for severe congenital diaphragmatic hernia repair. Combined blockade associated with sedation and fetal anesthesia proved safe and effective for tracheal occlusion.

Combined antenatal therapy with retinoic acid and tracheal occlusion in a rat model of congenital diaphragmatic hernia

AIM

To investigate the effect of combined prenatal treatment with retinoic acid (RA) and tracheal occlusion (TO) on the pulmonary vascular morphology and expression of vascular endothelial growth factors (VEGF) and its receptors in a rat model of congenital diaphragmatic hernia (CDH).

MATERIAL AND METHODS

Rats were given nitrofen at 9 days of gestation followed by no treatment (CDH), RA (CDH + RA), TO (CDH + TO), or both (CDH + RA + TO) (n = 16). We measured the median wall thickness of the pulmonary arterioles (MWT) and analyzed the expression of VEGF and its receptors (VEGFR1 and VEGFR2).

RESULTS

Compared to control animals, CDH had increased MWT (44 ± 15 vs. 58 ± 7; p < 0.05) and decreased expression of VEGF, VEGFR1, and VEGFR2 (p < 0.05). Treatment with RA or TO alone, and RA + TO reduced the MWT (46 ± 9, 42 ± 11, 46 ± 8, respectively) and improved the expression of VEGF, VEGFR1, and VEGFR2 compared to CDH (p < 0.05). However, the combination of RA + TO did not confer additional benefit in the reduction of the MWT or in increasing the VEGF and its receptors compared to either treatment alone.

CONCLUSION

Antenatal treatment with either RA or TO improved the MWT and expression of VEGF and its receptors in a CDH rat model. However, combined treatment with RA + TO was not superior to either treatment alone.

Transplacental sildenafil rescues lung abnormalities in the rabbit model of diaphragmatic hernia

INTRODUCTION

The management of congenital diaphragmatic hernia (DH) would benefit from an antenatal medical therapy, which addresses both lung hypoplasia and persistent pulmonary hypertension. We aimed at evaluating the pulmonary effects of sildenafil in the fetal rabbit model for DH.

METHODS

We performed a dose-finding study to achieve therapeutic fetal plasmatic concentrations without toxicity following maternal sildenafil administration. Subsequently, DH fetuses were randomly exposed to transplacental placebo or sildenafil 10 mg/kg/day from gestational day 24 until examination at term (day 30). Efficacy measures were ipsilateral pulmonary vascular and airway morphometry, micro-CT-based branching analysis, Doppler flow in the main pulmonary artery and postnatal lung mechanics.

RESULTS

Fetal sildenafil plasmatic concentration was above the minimal therapeutic level for at least 22 h/day without maternal and fetal side effects. The placebo-exposed DH fetuses had increased wall thickness in peripheral pulmonary vessels and significantly less fifth-order vessels compared with controls (CTR). Sildenafil-exposed DH fetuses, instead, had a medial and adventitial thickness in peripheral pulmonary vessels in the normal range and normal vascular branching. Fetal pulmonary artery Doppler showed a reduction of pulmonary vascular resistances both in DH and in CTR fetuses treated by sildenafil compared with the placebo-treated ones. Sildenafil also reversed the mean terminal bronchiolar density to normal and improved lung mechanics, yet without measurable impact on lung-to-bodyweight ratio.

CONCLUSIONS

In the rabbit model for DH, antenatal sildenafil rescues vascular branching and architecture, reduces pulmonary vascular resistances and also improves airway morphometry and respiratory mechanics.

Antenatal BAY 41-2272 reduces pulmonary hypertension in the rabbit model of congenital diaphragmatic hernia

Infants with congenital diaphragmatic hernia (CDH) fail to adapt at birth because of persistent pulmonary hypertension (PH), a condition characterized by excessive muscularization and abnormal vasoreactivity of pulmonary vessels. Activation of soluble guanylate cyclase by BAY 41-2272 prevents pulmonary vascular remodeling in neonatal rats with hypoxia-induced PH. By analogy, we hypothesized that prenatal administration of BAY 41-2272 would improve features of PH in the rabbit CDH model. Rabbit fetuses with surgically induced CDH at day 23 of gestation were randomized at day 28 for an intratracheal injection of BAY 41-2272 or vehicle. After term delivery (day 31), lung mechanics, right ventricular pressure, and serum NH2-terminal-pro-brain natriuretic peptide (NT-proBNP) levels were measured. After euthanasia, lungs were processed for biological or histological analyses. Compared with untouched fetuses, the surgical creation of CDH reduced the lung-to-body weight ratio, increased mean terminal bronchial density, and impaired lung mechanics. Typical characteristics of PH were found in the hypoplastic lungs, including increased right ventricular pressure, higher serum NT-proBNP levels, thickened adventitial and medial layers of pulmonary arteries, reduced capillary density, and lower levels of endothelial nitric oxide synthase. A single antenatal instillation of BAY 41-2272 reduced mean right ventricular pressure and medial thickness of small resistive arteries in CDH fetuses. Capillary density, endothelial cell proliferation, and transcripts of endothelial nitric oxide synthase increased, whereas airway morphometry, lung growth, and mechanics remained unchanged. These results suggest that pharmacological activation of soluble guanylate cyclase may provide a new approach to the prenatal treatment of PH associated with CDH.

Increased TGF-β: a drawback of tracheal occlusion in human and experimental congenital diaphragmatic hernia?

Survivors of severe congenital diaphragmatic hernia (CDH) present significant respiratory morbidity despite lung growth induced by fetal tracheal occlusion (TO). We hypothesized that the underlying mechanisms would involve changes in lung extracellular matrix and dysregulated transforming growth factor (TGF)-β pathway, a key player in lung development and repair. Pulmonary expression of TGF-β signaling components, downstream effectors, and extracellular matrix targets were evaluated in CDH neonates who died between birth and the first few weeks of life after prenatal conservative management or TO, and in rabbit pups that were prenatally randomized for surgical CDH and TO vs. sham operation. Before tissue harvesting, lung tissue mechanics in rabbits was measured using the constant-phase model during the first 30 min of life. Human CDH and control fetal lungs were also collected from midterm onwards. Human and experimental CDH did not affect TGF-β/Smad2/3 expression and activity. In human and rabbit CDH lungs, TO upregulated TGF-β transcripts. Analysis of downstream pathways indicated increased Rho-associated kinases to the detriment of Smad2/3 activation. After TO, subtle accumulation of collagen and α-smooth muscle actin within alveolar walls was detected in rabbit pups and human CDH lungs with short-term mechanical ventilation. Despite TO-induced lung growth, mediocre lung tissue mechanics in the rabbit model was associated with increased transcription of extracellular matrix components. These results suggest that prenatal TO increases TGF-β/Rho kinase pathway, myofibroblast differentiation, and matrix deposition in neonatal rabbit and human CDH lungs. Whether this might influence postnatal development of sustainably ventilated lungs remains to be determined.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Airway and vascular maturation stimulated by tracheal occlusion do not correlate in the rabbit model of diaphragmatic hernia

BACKGROUND

In animal models of congenital diaphragmatic hernia (CDH), tracheal occlusion (TO) has induced maturation of both airway spaces and vascular structures. Airway and vascular response to TO are assumed to occur in parallel. This study aims to describe and measure the relationship between airway and vascular maturation induced by TO.

METHODS

A rabbit model of CDH on gestational day (GD) 23 and TO on GD 28 (term = GD 31) has been used. Two study groups have been defined: DH (diaphragmatic hernia) and TO (DH treated with TO). Animals were collected on GD 30 and blood flow data of the pulmonary artery (pulsatility index (PI) and fractional moving blood volume) were ultrasonographically measured. Lung morphometry consisted of measurements of radial alveolar count (RAC) and arterial muscular thickness.

RESULTS

Animals in the DH group (n = 9) had the worst hemodynamic parameters; their lungs were hypoplastic and had the thickest arterial muscular layer. Animals in the TO group (n = 10) had all these effects reversed. There were no correlations among hemodynamic, airway, and vascular parameters, except for RAC and PI (r = -0.528, P = 0.043).

CONCLUSION

Airway and vascular maturation after TO appear to be uncorrelated effects. TO could trigger several pathways that separately regulate airway and vascular responses.

Alveolarization genes modulated by fetal tracheal occlusion in the rabbit model for congenital diaphragmatic hernia: a randomized study

Background

The mechanisms by which tracheal occlusion (TO) improves alveolarization in congenital diaphragmatic hernia (CDH) are incompletely understood. Therefore transcriptional and histological effects of TO on alveolarization were studied in the rabbit model for CDH. The question of the best normalization strategy for gene expression analysis was also addressed.

Methods

Fetal rabbits were randomized for CDH or sham operation on gestational day 23/31 and for TO or sham operation on day 28/31 resulting in four study groups. Untouched littermates were added. At term and before lung harvest, fetuses were subjected to mechanical ventilation or not. Quantitative real-time PCR was performed on lungs from 4–5 fetuses of each group with and without previous ventilation. Stability of ten housekeeping genes (HKGs) and optimal number of HKGs for normalization were determined, followed by assessment of HKG expression levels. Expression levels of eleven target genes were studied in ventilated lungs, including genes regulating elastogenesis, cell-environment interactions, and thinning of alveolar walls. Elastic staining, immunohistochemistry and Western blotting completed gene analysis.

Results

Regarding HKG expression, TO increased β-actin and β-subunit of ATP synthase. Mechanical ventilation increased β-actin and β2-microglobulin. Flavoprotein subunit of succinate dehydrogenase and DNA topoisomerase were the most stable HKGs. CDH lungs showed disorganized elastin deposition with lower levels for tropoelastin, fibulin-5, tenascin-C, and α6-integrin. After TO, CDH lungs displayed a normal pattern of elastin distribution with increased levels for tropoelastin, fibulin-5, tenascin-C, α6-integrin, ß1-integrin, lysyl oxidase, and drebrin. TO increased transcription and immunoreactivity of tissue inhibitor of metalloproteinase-1.

Conclusions

Experimental TO might improve alveolarization through the mechanoregulation of crucial genes for late lung development. However part of the transcriptional changes involved genes that were not affected in CDH, raising the question of TO-induced disturbances of alveolar remodeling. Attention should also be paid to selection of HKGs for studies on mechanotransduction-mediated gene expressions.

Pulmonary alveolar and vascular morphometry after gel plug occlusion of the trachea in a fetal rabbit model of CDH

PURPOSE

Tracheal occlusion (TO) induces lung growth in congenital diaphragmatic hernia (CDH) but is also associated with drawbacks. We devised a temporary gel plug that induced lung growth when placed in the fetal trachea. This study evaluates the effects of temporary versus permanent TO on histologic radial alveolar count (RAC) and vascular morphometrics.

METHODS

Experimental CDH was created surgically in 64 New Zealand White rabbit fetuses on gestational day (GD) 24. On GD 27, these fetuses were randomized to intratracheal instillation of a fibrin gel plug (GP), tracheal suture ligation (SL), intratracheal instillation of normal saline (NS), or sham amniotomy (SH). Non-manipulated fetuses served as controls (NM). Histologic lung sections were assessed blindly for RAC and relative arterial adventitial thickness (%AT) as a variable for vascular remodelling. Results were statistically compared.

RESULTS

RAC was significantly lower in the ipsilateral lung of SH fetuses than in the contralateral lung (p = 0.011). Mean RAC was higher after SL (p < 0.001) and GP (p = 0.03) compared to SH. Furthermore, %AT was higher in GP (50 ± 28, p < 0.001) and SL (45 ±2 6, p = 0.003) fetuses than in controls (36 ± 19).

CONCLUSION

Temporary and permanent TO leads to increased RAC; this effect was more pronounced with permanent TO. Both interventions were associated with an increased %AT. These findings may explain the adverse clinical effects of TO, despite causing accelerated lung growth.

Tracheal occlusion alters pulmonary circulation in the fetal lamb with normally developing lungs

BACKGROUND

Tracheal occlusion (TO) promotes fetal lung growth through an increase in intraluminal pressure. Although evidence suggests that fetal TO (FETO) decreases the occurrence of pulmonary hypertension in severe congenital diaphragmatic hernia, controversies on its effect on the pulmonary circulation remain. Therefore, we investigated the effects of FETO on the lung hemodynamics in a chronically catheterized fetal lamb model.

METHODS

Fifteen pregnant ewes were operated on between 125 and 128 days of gestation (term: 145 days). Catheters and ultrasonic flow transducer were placed through a left thoracotomy in the lamb fetus to determine aortic, pulmonary and left atrial pressures, and left pulmonary artery blood flow. A balloon was positioned between the carina and vocal cords under fetoscopic control. The animals were assigned to either control (n=6) or FETO (n=9) groups. TO was performed by inflating the balloon. We studied the acute effects of temporary (2-h) and prolonged (4-day) TO on basal pulmonary vascular tone and on the pulmonary vascular reactivity to acetylcholine and to increased fetal oxygen tension.

RESULTS

We found that left pulmonary blood flow (LPA) increased and pulmonary vascular resistance (PVR) decreased by 20% during brief TO (p<0.05). After balloon deflation, LPA blood flow further increased by 40%, and PVR decreased by 50% compared to baseline values (p<0.05). In contrast, no change in LPA blood flow or PVR was observed during prolonged TO. Moreover, the vasodilator responses to acetylcholine and to increased fetal PaO2 were blunted during TO.

CONCLUSIONS

These data indicate that antenatal tracheal occlusion promotes active pulmonary vasodilation, which is partly blunted by the mechanical effects of elevation of the intraluminal pressure.

Signaling molecules in the fetal rabbit model for congenital diaphragmatic hernia

RATIONALE AND OBJECTIVES

Little is known about molecular changes in lungs of fetal rabbits with surgically induced diaphragmatic hernia (DH). Therefore, we examined in this model gene expressions of pivotal molecules for the developing lung.

METHODS

At day 23 of gestation, DH was created in 12 fetuses from 4 does. Both lungs from six live DH fetuses and from six unoperated controls were harvested and weighed at term. Transcription of 15 genes involved in alveolarization, angiogenesis, regulation of vascular tone, or epithelial maturation was investigated by real-time quantitative polymerase chain reaction.

MAIN RESULTS

DH decreased lung-to-body weight ratio (P < 0.001). A bilateral downregulation was seen for genes encoding for tropoelastin (P < 0.01), lysyl oxidase (P < 0.05), fibulin 5 (P < 0.05), and cGMP specific phosphodiesterase 5 (P < 0.05). Lower mRNA levels for endothelial nitric oxide synthase occurred in the ipsilateral lung (P < 0.05).

CONCLUSIONS

Experimental DH in fetal rabbits disrupted transcription of genes implicated in lung growth and function. Similarities with the human disease make this model appropriate for investigation of new prenatal therapies.

Advances in prenatal diagnosis and treatment of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common birth anomaly. Absence or presence of liver herniation and determination of lung-to-head ratio are the most accurate predictors of prognosis for fetuses with CDH. Though open fetal CDH repair has been abandoned, fetal endoscopic balloon tracheal occlusion promotes lung growth in fetuses with severe CDH. Although significant improvements in lung function have not yet been shown in humans, reversible or dynamic tracheal occlusion is promising for select fetuses with severe CDH. This article reviews advances in prenatal diagnosis of CDH, the experimental basis for tracheal occlusion, and its translation into human clinical trials.

Contribution of intrapulmonary artery Doppler to improve prediction of survival in fetuses with congenital diaphragmatic hernia treated with fetal endoscopic tracheal occlusion

OBJECTIVE

To evaluate the contribution of intrapulmonary artery Doppler in predicting the survival of fetuses with congenital diaphragmatic hernia (CDH) treated with fetoscopic tracheal occlusion (FETO).

METHODS

A cohort of 41 fetuses (between 24 and 28 weeks of gestation) with CDH was treated with FETO. The observed/expected lung-to-head ratio (O/E-LHR), pulmonary artery pulsatility index (PI), peak early diastolic reversed flow (PEDRF) and peak systolic velocity (PSV) were evaluated before FETO, and their isolated and combined value to predict survival using multiple logistic regression and decision-tree analysis was assessed.

RESULTS

O/E-LHR and intrapulmonary artery PI and PEDRF were significantly associated with the probability of survival (O/E-LHR > or = 26%, OR 14.2; PI < 1 Z-score, OR 8.4; and PEDRF < 3.5 Z-scores, OR 5.7). Decision-tree analysis showed that O/E-LHR was the best initial predictor of prognosis (O/E-LHR > or = 26%, 90% survival; O/E-LHR < 26%, 45% survival). For fetuses with an O/E-LHR of < 26%, Doppler parameters allowed discrimination of cases with moderate (66-71% survival) and very poor (0% survival) prognosis.

CONCLUSION

Intrapulmonary artery Doppler evaluation helps to refine the prediction of survival after FETO in fetuses with severe CDH.

Antenatal fetal VEGF therapy to promote pulmonary maturation in a preterm rabbit model

AIM

To assess the effects of fetal tracheal administration of VEGF on pulmonary maturation in a preterm rabbit model.

METHODS

On day 26 (term=31days), fetal rabbits received recombinant rat VEGF (30microg in 70microL normal saline) or placebo (normal saline 70microL) intratracheally, with or without subsequent tracheal occlusion. Non-operated littermates served as internal controls. Fetuses were harvested on day 28 for morphometric study of the lungs or for mechanical ventilation and measurement of lung mechanics. In total, 96 fetuses from 42 does were used, 47 for ventilation and 49 for morphometry.

RESULTS

In fetuses receiving intratracheal VEGF, an increase in immunoreactivity for Flk-1 was observed throughout the lung parenchyma. Tracheal occlusion (TO) adversely affected pulmonary mechanics as compared to un-occluded controls. That effect is partly reversed by intratracheal VEGF. Intratracheal injection of VEGF without tracheal occlusion improves lung mechanics but no more than what was observed in placebo injected controls.

CONCLUSION

Antenatal intratracheal VEGF administration was associated with an increase in Flk-1 immunoreactivity. It also improves lung mechanics, however more so when the trachea is occluded. Without TO, the effects were comparable to placebo controls.

The impact of iatrogenic gastroschisis on pulmonary maturation in the fetal rabbit models of congenital diaphragmatic hernia

PURPOSE

The aim of this study was to analyze the effect of iatrogenic gastroschisis on pulmonary hypoplasia in fetal rabbits with congenital diaphragmatic hernia (CDH).

MATERIALS AND METHODS

A total of 30 pregnant rabbits received fetal surgery on gestational day 23. A left diaphragmatic hernia was created in one end fetus (DH group) of each rabbit, and the other end fetus of the same rabbit received sham thoracotomy as control (CR group). Another 19 pregnant rabbits underwent partial resection of the diaphragm in both end fetuses on gestational day 23, and then artificial gastroschisis was performed on one end fetus (GS group) on gestational day 26, while the other end remained as control (CGS group). The fetuses were harvested on gestational day 30. The histological and morphometric evaluation of lungs and livers of the end fetuses in each group was conducted.

RESULTS

In the DH group, the lungs were hypoplastic with a decrease in the total lung weight to body weight ratio, and remarkable thickening in alveolar septa. The lung vessels showed significantly thicker arterial walls when compared with those from control fetuses. The pathological finding in the CGS group was similar to that of the DH group. The thickness of the alveolar septa and of the pulmonary arterial walls showed no significant difference among the GS group, DH group and the CGS group. The ratio of liver weight to body weight increased notably in the GS group, DH group and CGS group compared with that in the CR group.

CONCLUSIONS

In the fetal rabbit models of CDH, pulmonary hypoplasia is the most significant pathological feature. Iatrogenic gastroschisis does not improve pulmonary maturation due to the active growth of the liver that herniates into the thoracic cavity.

Tracheal occlusion for fetal congenital diaphragmatic hernia: the US experience

Congenital diaphragmatic hernia (CDH) is characterized by a defect in the diaphragm that permits abdominal viscera to herniate into the chest. These herniated viscera are thought to compress the growing lung and cause lung parenchymal and vascular hypoplasia. The genetic defects that cause the diaphragmatic defect may also contribute primarily to lung hypoplasia. Postnatal reduction of the herniated abdominal viscera and correction of the diaphragmatic defect are easily achievable, but the lung hypoplasia persists, often leading to persistent fetal circulation and respiratory failure. This article reviews the experimental basis of fetal therapy for CDH and the US clinical experience with tracheal occlusion.

The effect of fetal tracheal occlusion on lung tissue mechanics and tissue composition

Fetal tracheal occlusion (TO) is currently used to treat severe cases of congenital diaphragmatic hernia (DH). Clinical and experimental studies suggest an improved postnatal outcome, but lung tissue mechanics after TO have not been studied. We determined the effect of TO on mechanical impedance and lung tissue components in a rabbit model for DH. At 23 days of gestation (term = 31 days) either a sham thoracotomy or a diaphragmatic defect was induced. DH fetuses were randomly assigned to undergo 5 days later TO. Fetuses were delivered by term cesarean section to determine lung to body weight ratio (LBWR), dynamic lung mechanics and lung impedance. Airway resistance (R(aw)), elastance (H(L)), tissue damping (G(L)) and hysteresivity (G(L)/H(L)) were calculated from impedance data. Collagen I and III and elastin were quantified histologically. LBWR was significantly increased by TO compared to DH (P < 0.001) and resistance and compliance of the respiratory system (R(rs), C(rs)) were improved as well. TO resulted in a significant decrease of R(aw) comparable to observations in sham-fetuses, without effect on lung tissue mechanics H(L), G(L) and hysteresivity. This coincides with a significant decrease of collagen I, III and elastin in comparison to DH fetuses. In this first report on lung tissue mechanics in a rabbit model of DH, TO had a substantial effect on tissue morphology yet this was not mirrored in lung mechanics. We conclude that the effect of TO on lung mechanics without in utero reversal of occlusion, is dominated by airway remodeling.

Fetal tracheal occlusion for severe congenital diaphragmatic hernia in humans: a morphometric study of lung parenchyma and muscularization of pulmonary arterioles

OBJECTIVE

The aim of this study is to examine structure of lung parenchyma (Pp) and muscularization of pulmonary arterioles (PAs) in human fetuses that underwent tracheal occlusion (TO) therapy for severe congenital diaphragmatic hernia (CDH).

MATERIAL

Fifteen fetuses underwent TO, with 5 survivors (Am J Obstet Gynecol. 2000:183;1059-1066). Paraffin-embedded lung specimens from 7 of 10 nonsurvivors (CDH-TO) and 6 age-matched fetuses (CDH) were available for morphometric analysis, which included measurements of point fraction of lung Pp and surface density. The PAs were categorized according to external diameter (<70 microm and 70 <or= 140 microm). Percent medial wall thickness (%MWT) was calculated by dividing raw measurements of MWT by external diameter.

RESULTS

Gestational age at TO was 27.6 +/- 0.9 weeks with a mean duration of TO of 32.6 +/- 6.8 days. Gestational age at delivery (CDH-TO 31.9 +/- 0.9 vs CDH 35.4 +/- 1.8 weeks; P = .18) and postnatal survival time (CDH-TO 20.5 +/- 6.0 vs CDH 18.6 +/- 7.8 days; P = .85) were not significantly different between groups. Tracheal occlusion significantly increased the lung-to-body weight ratio (CDH-TO 13.0 +/- 2.2 vs CDH 6.6 +/- 0.9; P = .02). Tracheal occlusion tended to decrease right-lung Pp (CDH-TO 54.6% +/- 2.6% vs CDH 65.7% +/- 5.9%; P = .05), whereas left-lung Pp was not different between groups (CDH-TO 63.0% +/- 3.5% vs CDH 66.7% +/- 4.1%; P = .51). Surface density of airspaces was not different between groups in either left (CDH-TO 171.3 +/- 16.1 cm(-1) vs CDH 151.1 +/- 8.1 cm(-1); P = .34) or right (CDH-TO 172.0 +/- 10.6 cm(-1) vs CDH 160.8 +/- 3.6 cm(-1); P = .33) lungs. The %MWT in small and large PA was similar between groups.

CONCLUSIONS

Open prenatal TO in human fetuses increased lung growth, as evidenced by an increase in lung weight, but did not improve parenchymal structure or muscularization of PAs.

Effects of betamethasone on peripheral arterial development in term fetal rabbit

Glucocorticoids are given antenatally to promote pulmonary epithelial maturation and prevent respiratory distress syndrome in premature newborns. In contrast to airway changes, effects on vessels are less documented. We hypothesized that antenatal betamethasone (BM) administration promotes vascular development. Does received either a course of BM = 0.05 mg/kg/day (18 does, 70 fetuses), BM = 0.1 mg/kg/day (20 does, 75 fetuses), or saline (11 does, 92 fetuses) starting on d25, 26 (canalicular stage), d27, d28 (saccular stage), and d29 (alveolar stage) of gestation. In total 236 fetuses from 49 does were examined at term (d31) in terms of vascular development. Lung specimens were weighed and formalin fixed for morphometry. We determined differences in fetal body, liver and lung weight, proportionate medial thickness, muscularization of intra-acinar vessels, number of vessels under 100 microm, as well as immunoreactivity to Flk-1 in vascular smooth muscle and endothelial cells. A dose-dependent reduction in neonatal body and organ weight was observed in fetuses exposed to BM at d25. In contrast, term liver weight increased after late administration of BM (d28, 29). There was a dose- and time-dependent thinning of the pulmonary arterial media, which coincided with a decreased proportion of intra- and pre-acinar muscularized arteries (ED <or= 60 microm) and increased microvascularization (ED <or= 30), as well as increased endothelial immunoreactivity for Flk-1. Analyzing our data using a purpose designed geometrical model, the results suggest that maternal administration of BM promotes changes in vascular morphology, which may be compatible with remodeling and vessel formation.

Effect of maternal administration of betamethasone on peripheral arterial development in fetal rabbit lungs

OBJECTIVES

Glucocorticoids promote lung maturation and reduce the incidence of respiratory distress syndrome in premature newborns. We hypothesized that betamethasone (BM), which is known to induce thinning of the alveolar walls, would also thin the arterial media and adventitia of intra-parenchymatic vessels in developing rabbit lungs.

STUDY DESIGN

112 fetuses from 21 time-mated, pregnant, giant white rabbits received maternal injections of BM at either 0.05 or 0.1 mg/kg/day on days 25-26 of gestational age. Controls received either saline (10 does, 56 fetuses) or no injection (10 does, 59 fetuses). Fetuses were harvested from day 27 onwards until term (day 31). 44 additional fetuses (8 does) were harvested between days 23 and 26. Endpoints were wet lung-to-body weight ratio, vascular morphometric indices and immunohistochemistry staining for alpha-smooth muscle actin, Flk-1, vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS). ANOVA (Tukey's test) and independent t test (p < 0.05) were used for comparison between BM and saline groups.

RESULTS

Maternal BM injected on days 25-26 to pregnant rabbits induced a significant decrease in fetal body and lung weight and the lung-to-body weight ratio in the preterm pups shortly after injection. BM led to a dose-dependent thinning of the arterial media and adventitia (pulmonary arteries with an external diameter (ED) of <100 microm), to an increase in the percentage of non-muscularized peripheral vessels (ED <60 microm), in eNOS and VEGF immunoreactivity of the endothelial and smooth muscle cells in the pulmonary vessels and to an increase in Flk-1-positive pulmonary epithelial cell density.

CONCLUSIONS

Maternal administration of BM caused thinning of the arterial wall of pulmonary vessels (ED <100 microm) and a decrease in muscularization in peripheral vessels (ED <60 microm). This coincided with increased expression of Flk-1 in the endothelium and smooth muscle cells of the pulmonary arteries. All the effects studied were dose-dependent.

The effect analysis and comparison between gastroschisis and tracheal ligation on experimental diaphragmatic hernia in fetal rabbits

PURPOSE

The authors analyzed and compared the effects of experimentally induced gastroschisis and tracheal ligation on pulmonary hypoplasia in fetal rabbits with congenital diaphragmatic hernia.

METHODS

Twenty-three pregnant rabbits underwent fetal surgery on gestational day 24 through 27. Left diaphragmatic hernia was created in 1 fetus (DH group) from each rabbit, and a left diaphragmatic hernia with gastroschisis (GS group) or tracheal ligation (TL group) was created in another fetuses. The fetuses were delivered on gestational day 27 through 33. Histologic and morphometric examination of the lungs were performed in each group.

RESULTS

In the DH group, the lungs were hypoplastic with a decrease in lung weight to body weight ratio and an increase in pulmonary arterial wall thickness. The alveolar septae were markedly thickened and diminished alveolar air spaces. In GS and TL groups, the alveolar septae were thickened but narrower than those of the DH group, air spaces were increased, and the pulmonary arterial wall was only slightly thickened.

CONCLUSIONS

Pulmonary hypoplasia seen in newborn rabbits after experimentally induced diaphragmatic hernia is less severe in those rabbits with concurrently made gastroschisis or tracheal ligation. From the histologic viewpoint, the effects of gastroschisis and tracheal ligation on pulmonary hypoplasia in diaphragmatic hernia have no differences.

Pulmonary arteriole muscularization in lambs with diaphragmatic hernia after combined tracheal occlusion/glucocorticoid therapy

OBJECTIVE

A morphometric study was performed to examine the effects of prenatal glucocorticoids, which were administered 48 hours before birth, on muscularization of small pulmonary arterioles (<60 microm diameter) in lambs with diaphragmatic hernia (DH) after fetal tracheal occlusion (TO).

STUDY DESIGN

DH was created in 23 fetal sheep at 65 days gestation. TO was performed in 16 of 24 fetuses between 110 and 140 days of gestation; 9 of the fetuses were exposed prenatally to betamethasone (0.5 mg/kg body weight) 48 hours before delivery. Six sham-operated animals served as controls. Sections of paraffin that were embedded in lung tissues were stained with Elastin-Van Gieson, and the percentage of medial wall thickness (MWT) was determined.

RESULTS

The percentage of MWT in DH lambs (29.6% +/- 1.9%) was increased compared with sham animals (18.1% +/- 1.3%) and was not different from that of DH/TO animals (30.3% +/- 1.7%). In DH/TO + glucocorticoid lambs, the percentage of MWT (24.6% +/- 1.2%) was significantly lower than in the DH/TO group but was higher than the sham group.

CONCLUSION

In fetuses who underwent prolonged TO therapy for severe DH, prenatal glucocorticoid treatment decreased medial hypertrophy of pulmonary arterioles by approximately 19%. We speculate that such structural changes may have contributed to improve gas exchange that was observed in this model.

Lung tissue mechanics predict lung hypoplasia in a rabbit model for congenital diaphragmatic hernia

Several animal models have been proposed to study the pathophysiology of congenital diaphragmatic hernia (CDH). Surgical induction of CDH in fetal rabbits during the pseudoglandular phase has been shown to induce severe pulmonary hypoplasia, but functional studies in this model are scarce. We aimed to measure neonatal pulmonary impedance and related it to the severity of lung hypoplasia. CDH was surgically created in rabbits at 23 days of gestation. Following cesarean delivery at term (31 days) pups were subjected to measurement of total lung capacity (TLC), lung to body weight ratio (LBWR) and lung impedance by forced oscillation technique (FOT). Airway resistance (R(aw)), tissue elastance (H(L)), tissue damping (G(L)), and hysteresivity (eta) (G(L)/H(L)) were calculated from impedance data. Twelve CDH fetuses and 15 controls were available for final analysis. LBWR and TLC were significantly lower in the CDH group compared to gestational and age matched controls (P<0.001). R(aw), H(L), and G(L) were significantly increased in CCDH fetuses. eta and H(L) best reflected lung hypoplasia (LBWR) (r(2) = 0.42 and 0.43; P=0.001), indicating a dominant contribution of lung tissue mechanics to CDH-induced lung hypoplasia. We successfully introduced lung impedance measurement by FOT in neonatal rabbits. Following surgical induction of CDH in the pseudoglandular phase, they have, next to morphological evidence of pulmonary hypoplasia, changes in lung mechanics. Our results for lung tissue mechanics support the concept of delayed pulmonary tissue modeling. We propose to employ functional studies in future experiments when evaluating prenatal interventions aimed at reversing pulmonary hypoplasia.

Prenatal intervention for congenital diaphragmatic hernia

Advances in prenatal ultrasound have revealed the poor natural history of fetal congenital diaphragmatic hernia (CDH) and its hidden mortality during gestation and immediately after birth. Attempts to improve this poor outcome led to the development of prenatal surgical intervention for severe CDH by Harrison and his colleagues at the University of California San Francisco. Prenatal surgical intervention for CDH has seen four phases: open fetal surgical repair, open surgical tracheal occlusion, endoscopic external tracheal occlusion, and endoscopic endoluminal tracheal occlusion. After extensive work in the laboratory, prenatal intervention has been applied in humans since 1984. With the most recent techniques, maternal risk is significantly reduced as is the incidence of preterm labor. In the meantime, the survival rate of fetuses with CDH without fetal intervention has improved mainly due to the minimization of iatrogenic lung injury by gentle ventilation, first described in 1985. However, the morbidity of the survivors with severe CDH remains high. Prenatal intervention for CDH will be justified if improvement in survival or morbidity can be demonstrated when compared to planned delivery and postnatal management with gentle ventilation strategy.

Pulmonary vascular remodeling

The maladaptive response of the pulmonary vasculature that occurs in patients with congenital diaphragmatic hernia significantly impacts outcome. Muscularized distal pulmonary arterioles inhibit the ability of the neonate to adjust to extrauterine circulation, resulting in severe pulmonary hypertension. This review summarizes the current state of knowledge regarding normal and abnormal development of the lung vascular system and identifies current and potential therapies directed toward preserving or restoring proper pulmonary vascular function.

Tracheal occlusion: A review of obstructing fetal lungs to make them grow and mature

Fetal lung growth and functional differentiation are affected strongly by the extent that pulmonary tissue is distended (expanded) by liquid that naturally fills developing future airspaces. Methods that prevent normal egress of this lung fluid through the trachea magnify mechanical stretching of lung parenchymal cells, thereby promoting lung development. Indeed, experimental observations demonstrate that in utero tracheal occlusion (TO) performed on fetuses during the late canalicular-early saccular stage potently stimulates pulmonary growth and maturation. In this review, we present the four principle non-human animal models of TO/obstruction and discuss them in relation to their utility in elucidating lung development, in remedying congenital diaphragmatic hernia (CDH) as well as in investigating the stretching effects on growth and remodeling of the fine vasculature.

Quantitative analysis of fetal pulmonary vasculature by 3-dimensional power Doppler ultrasonography in isolated congenital diaphragmatic hernia

OBJECTIVE

The purpose of this study was to evaluate the potential of 3-dimensional (3D) power Doppler imaging to predict neonatal outcome and pulmonary arterial hypertension (PAH) in congenital diaphragmatic hernia (CDH).

STUDY DESIGN

In this prospective observational study, 3D-power Doppler ultrasonography was performed in 21 cases with isolated CDH between 23 and 33 weeks of gestation and in 58 controls between 20 and 40 weeks. Using the same preestablished settings for all cases, power Doppler was applied to each lung, and fetal lung volumes (FLV) were estimated using the rotational technique. The 3D power Doppler histogram was used to determine the vascular indices, which were plotted against gestational age and compared with neonatal outcome, PAH, gestational age, and FLV.

RESULTS

Fetal pulmonary vascular indices showed a constant distribution throughout gestation, being significantly lower in cases with CDH than in controls (P < .001). Among CDH cases, the vascular indices were significantly lower in fetuses who died (P < .05), and in fetuses with neonatal PAH (P < .05). The severity of neonatal PAH was also associated with a progressive reduction in prenatal vascular indices (P < .05). All vascular indices correlated with o/e-FLV, but not with gestational age.

CONCLUSION

All vascular indices seem to be constant throughout gestation. In isolated CDH, perinatal outcome and postnatal PAH can be predicted using the vascular indices assessed by 3D power Doppler histogram.

Fetal lung-to-head ratio in the prediction of survival in severe left-sided diaphragmatic hernia treated by fetal endoscopic tracheal occlusion (FETO)

OBJECTIVE

The objective of the study was to investigate the value of fetal lung area to head circumference ratio in the prediction of the postnatal outcome in left-sided congenital diaphragmatic hernia treated by fetoscopic endoluminal tracheal occlusion.

STUDY DESIGN

The lung area to head circumference ratio was measured before fetoscopic endoluminal tracheal occlusion in 28 fetuses with congenital diaphragmatic hernia at 25 to 29 weeks. Regression analysis was used to investigate the effect on survival of lung area to head circumference ratio, gestation at fetoscopic endoluminal tracheal occlusion, gestation at delivery, preterm amniorrhexis following fetoscopic endoluminal tracheal occlusion, and prenatal removal of the balloon.

RESULTS

The median lung area to head circumference ratio prior to fetoscopic endoluminal tracheal occlusion was 0.7 (range 0.5 to 0.9). The median gestation at delivery was 34 (range 27 to 39) weeks, and there were 16 survivors (57%). Only lung area to head circumference ratio provided significant prediction of survival, which increased from 17% for lung area to head circumference ratio of 0.4 to 0.5 to 62% for lung area to head circumference ratio of 0.6 to 0.7 and 78% for lung area to head circumference ratio of 0.8 to 0.9.

CONCLUSION

In congenital diaphragmatic hernia treated by fetoscopic endoluminal tracheal occlusion, postnatal survival can be predicted by the lung area to head circumference ratio measured prior to the procedure.

Prenatal intervention for isolated congenital diaphragmatic hernia

PURPOSE OF REVIEW

We aim to review the recent literature regarding early prenatal prediction of outcome in babies diagnosed with isolated congenital diaphragmatic hernia, as well as results of fetal therapy for this condition.

RECENT FINDINGS

Current survival rates in population-based studies are around 55-70%. Highly specialized centers report 80% and more, but discount the hidden mortality, mainly in the antenatal period. Fetuses presenting with liver herniation and a lung-to-head ratio of less than 1.0 measured in midgestation have a poor prognosis. Other volumetric techniques are being evaluated for use in midtrimester. Recently, a randomized trial failed to show benefit from prenatal therapy, but lacked power to document the potential advantage of prenatal therapy in severe cases. We proposed percutaneous fetal endoluminal tracheal occlusion with a balloon at 26-28 weeks through a 3.3 mm incision. In severe cases, fetal endoluminal tracheal occlusion increased lung size as well as survival, with an early (7 day) survival, late neonatal (28 day) survival and survival at discharge of 75, 58 and 50%, respectively, comparing favorably with 9% in contemporary controls. Airways can be restored prior to birth improving neonatal survival (83.3% compared with 33.3%). The procedure carries a risk for preterm prelabour rupture of the fetal membranes, although that may decrease with experience.

SUMMARY

Fetuses with severe congenital diaphragmatic hernia can be identified in the second trimester. Fetal endoluminal tracheal occlusion can be considered as a minimally invasive fetal therapy, improving outcome in such highly selected cases.

Encouraging Early Clinical Experience with Deliberately Delayed Temporary Fetoscopic Tracheal Occlusion for the Prenatal Treatment of Life-Threatening Right and Left Congenital Diaphragmatic Hernias

OBJECTIVE

In order to assess the effect of deliberately delayed percutaneous fetoscopic tracheal occlusion on survival of fetuses with life-threatening congenital diaphragmatic hernia.

METHODS

Eight fetuses with life-threatening congenital diaphragmatic hernia underwent fetoscopic tracheal balloon occlusion between 29 + 0 and 32 + 4 weeks of gestation. Delayed occlusion was chosen in order to minimize potentially negative pulmonary effects from premature delivery as a result of fetal surgery. In addition, we wanted to become able to provide all available postnatal intensive care treatment means in these patients.

RESULTS

Six of the 8 fetuses survived to discharge from hospital.

CONCLUSION

Delayed fetoscopic tracheal balloon occlusion may be rewarded with lung growth sufficient to allow survival of fetuses with life-threatening congenital diaphragmatic hernia.

Tracheal occlusion in fetal rats alters expression of mesenchymal nuclear transcription factors without affecting surfactant protein expression

BACKGROUND/PURPOSE

Mesenchymal nuclear transcription factors (MNTF) are involved in lung development and maturation and regulate surfactant protein (SP) expression. Prolonged (>2 weeks) fetal tracheal occlusion (TO) has been shown to accelerate lung growth and inhibit pulmonary surfactant synthesis. The effects of TO on SP expression and MNTF, however, have not been formally assessed. The objectives of this study were to evaluate the effects of short-term (3 days) TO on normal lung growth and protein expression of pulmonary MNTF involved in SP synthesis.

METHODS

At E19 (term, 22 days), 2 fetuses per time-dated Sprague-Dawley rats underwent either TO (n = 23) or a sham (n = 22) operation. Lungs were harvested 72 hours post surgery. Pulmonary SP-A; SP-B; SP-C messenger RNA (mRNA) expression; and SP-A and SP-B, Hoxb5, thyroid transcription factor 1, and retinoic X receptor-alpha protein expression were analyzed.

RESULTS

Lung weight was significantly increased by TO (TO 0.32 +/- 0.02g vs SHAM 0.14 +/- 0.01 g; P < .001), resulting in 123% increase of the lung-to-body-weight ratio. No difference of SP-A-mRNA (177 +/- 4.3 TO vs 169 +/- 4.4 SHAM; P = .25), SP-B-mRNA (87.7 +/- 0.2 TO vs 87.4 +/- 0.02 SHAM; P = .33), and SP-C-mRNA (186.5 +/- 3.2 TO vs 183.2 +/- 2.7 SHAM; P = .45) expression was found. Surfactant protein A (175.6 +/- 25.3 TO vs 192.5 +/- 19.8 SHAM; P = .59) and SP-B (163.4 +/- 5.2 TO vs 166.8 +/- 9.3 SHAM; P = .75) protein expression were similar in both groups; however, Hoxb5 (70.3 +/- 18.9 TO vs 130.6 +/- 5.1 SHAM; P = .02) and thyroid transcription factor 1 (102.6 +/- 19 TO vs 181.1 +/- 6.3 SHAM; P = .007) expression were significantly decreased. Retinoic X receptor-alpha expression tended to be increased by TO (171.9 +/- 6.0 TO vs 155.4 +/- 6.7 SHAM; P = .06).

CONCLUSIONS

Short-term TO late in gestation induces rapid lung growth. Surfactant protein-mRNA and protein expression are not significantly altered. Thyroid transcription factor 1 and Hoxb5 are down-regulated by TO, suggesting that duration and timing of occlusion are important in balancing the effects of TO on lung growth vs lung maturation.

Current consequences of prenatal diagnosis of congenital diaphragmatic hernia

BACKGROUND

Today, the diagnosis of congenital diaphragmatic hernia (CDH) can readily be made in the prenatal period during screening ultrasound examination. Patients ought to be referred to rule out associated anomalies, and in isolated cases, prognosis is poor when the liver is intrathoracic and the lung-to-head ratio (LHR) is less than 1. In these patients, prenatal intervention aiming to reverse pulmonary hypoplasia can be considered.

METHODS

We present our current algorithm for counselling patients presenting with CDH. Patients with a poor prognosis are offered percutaneous fetal endoluminal tracheal occlusion (FETO) with a balloon, inserted at 26 to 28 weeks. We report on the evolution of technique and results in a consecutive homogeneous case series and compare outcome in cases with similar severity managed in the postnatal period.

RESULTS

Within a period of 28 months, FETO was performed between 26 and 28 weeks in 24 fetuses with severe left-sided CDH. Under general (n = 5), epidural (n = 17) or local (n = 2) anesthesia, the balloon was successfully positioned at first surgery (23/24) with a mean operation time of 20 minutes (range, 3-60 minutes). There were no serious maternal complications or direct fetal adverse effects. In the first 2 weeks after FETO, LHR increased from 0.7 to 1.7. Premature prelabour rupture of the membrane (PPROM) occurred in 16.7% and 33.3% at 28 and 32 weeks or earlier, respectively. Gestational age at delivery was 33.5 weeks. Patency of airways was restored either in the prenatal (n = 12) or perinatal period (n = 12). Early (7 days) and late (28 days) survival, and survival at discharge were 75% (18/24), 58.3% (14/24) and 50% (12/24), respectively. Half of nonsurvivors (n = 6) died of pulmonary hypoplasia and hypertension, in combination with PPROM and preterm delivery (n = 4) and balloon dislodgement (n = 2), which coincided with a short tracheal occlusion (TO) period (12 days). In the other 6, TO period was comparable to that in the 12 survivors (47 vs 42 days, respectively). In that group of 6 babies, only 2 died of pulmonary problems. Late neonatal survival (28 days) was higher with prenatal vs perinatal balloon retrieval 83.3% vs 33.3% (P = .013). In a multicentre study validating the criteria, survival till discharge in 37 comparable cases was 9% (3/32) and 13% (5/37) of parents opted for termination.

CONCLUSION

Fetuses with isolated left-sided CDH, liver herniation, and LHR of less than 1 have a poor prognosis. Percutaneous FETO is minimally invasive and may improve the outcome in these highly selected cases. Airways can be restored before birth, allowing vaginal delivery and return to the referring tertiary unit and may improve survival rate. The procedure carries a risk for PPROM, although that may decrease with experience.

Fetal intervention for congenital diaphragmatic hernia: the European experience

Fetuses with CDH presenting with liver herniation and a lung area-to-head circumference ratio of less than 1.0 have a high chance for neonatal death due to pulmonary hypoplasia. Fetal tracheal occlusion (TO) prevents egress of lung liquid, which triggers lung growth. In animal experiments, we were able to develop a minimally invasive technique for Fetoscopic Endoluminal Tracheal Occlusion (FETO) with a detachable balloon. In 2001, we demonstrated feasibility of FETO by percutaneous access in fetuses with severe CDH. In a retrospective multicenter review, we obtained LHR measurements and position of the liver in 134 cases of isolated left-sided CDH between 24 and 28 weeks. Eleven patients (8%) with LHR < 1.4 opted for termination. Overall survival of liveborn babies was 47% (58/123). LHR and position of the liver correlated both to survival. Combination of both variables predicted neonatal outcome better: liver up and LHR < 1.0 predicted a survival of 9%. When LHR < 0.6, there were no survivors irrespective of liver position. We could successfully perform endotracheal placement of the balloon in 20 cases at a median gestational age of 26 weeks. The mean duration of the operation was 22 (range 5-54) minutes. In 11 (55%) of these patients, there was postoperative prelabor (ie, <37 weeks) amniorrhexis. Membranes ruptured before 32 weeks in 35%, with a decreasing trend as experience increased. Ultrasound scans after FETO demonstrated an increase in the echogenicity of the lungs within 48 hours and improvement in the LHR from a median 0.7 (range 0.4-0.9) before FETO to 1.8 (range 1.1-2.9) within 2 weeks after surgery. The median gestation at delivery was 33.2 (range 27-38) weeks, and in 14 (70%) this occurred after 32 weeks. Surgical repair of the diaphragmatic hernia could be done in 13 babies, and in all but 1 the defect was extensive and required the insertion of a patch. Survival to discharge was 50%. These 10 long-term surviving babies are now aged 7 to 26 (median 19) months without known neurologic morbidity. Eight babies died in the neonatal period due to complications of the underlying disease. Two nonsurvivors died from other causes but with appropriately developed lungs. Improved survival coincided with increasing experience, in turn related to reduced incidence of postoperative amniorrhexis, later delivery, and a change in the policy on the timing of removal of the balloon from intrapartum to the prenatal period. Survival in eligible contemporary controls was 1/12 (8%). The presence of liver herniation and a low lung-to-head ratio (LHR <1.0) is a good predictor of poor prognosis at different tertiary centers around the world. Severe CDH may be successfully treated with FETO, which is minimally invasive and may improve postnatal survival.