Evaluation of regional lung mass and growth in neonates with bronchopulmonary dysplasia using ultrashort echo time magnetic resonance imaging

RATIONALE

Bronchopulmonary dysplasia (BPD) is the most common long term pulmonary morbidity in premature infants and is characterized by impaired lung growth and development. We hypothesized that lung mass growth is a critical factor in determining outcomes in infants with BPD.

OBJECTIVES

To measure regional lung density and mass in infants with BPD and compare to clinical variables.

METHODS

We conducted a retrospective cohort study of neonates (n = 5 controls, n = 46 with BPD). Lung mass and lung density were calculated using ultrashort echo time (UTE) magnetic resonance imaging (MRI).

MEASUREMENTS AND MAIN RESULTS

Lung mass increased with increasing corrected gestational age at the time of MRI in all patients. Total, right, and left lung mass in infants with BPD trended higher than control infants (65.7 vs. 49.9 g, 36.2 vs. 26.8 g, 29.5 vs. 23.1 g, respectively). Babies with BPD who survived to discharge had higher relative lung mass than control infants and infants with BPD that did not survive to discharge (21.6 vs. 15.7 g/kg, p = .01). There was a significant association between the rate of lung mass growth and linear growth at the time of MRI (p = .034).

CONCLUSIONS

Infants with BPD are capable of building lung mass over time. While this lung mass growth in infants with BPD may not represent fully functional lung tissue, higher lung mass growth is associated with increased linear growth.

Early life surfactant protein-D levels in bronchoalveolar lavage fluids of extremely preterm neonates

Surfactant protein-D (SP-D) is a hydrophilic protein with multiple crucial anti-inflammatory and immunological functions. It might play a role in the development and course of pulmonary infections, acute respiratory distress syndrome, and other respiratory disorders. Only few small neonatal studies have investigated SP-D: we aimed to investigate the links between this protein, measured in the first hours of life in extremely preterm neonates, and clinical outcomes, as well its relationship with pulmonary secretory phospholipase A2 (sPLA2). Bronchoalveolar lavage fluids were obtained within the first 3 h of life. SP-D and sPLA2 were measured with ELISA and radioactive method, respectively; epithelial lining fluid concentrations were estimated with urea ratio. Clinical data were prospectively collected. One hundred extremely preterm neonates were nonconsecutively studied. SP-D was significantly raised with increasing gestational age (24-26 wk: 68 [0-1,694], 27 or 28 wk: 286 [0-1,328], 29 or 30 wk: 1,401 [405-2,429] ng/mL, overall P = 0.03). SP-D was significantly higher in cases with clinical chorioamnionitis with fetal involvement (1,138 [68-3,336]) than in those without clinical chorioamnionitis with fetal involvement (0 [0-900] ng/mL, P < 0.001). SP-D was lower in infants with bronchopulmonary dysplasia (BPD) (251 [0-1,550 ng/mL]) compared with those without bronchopulmonary dysplasia (BPD) or who died before its diagnosis (977 [124-5,534 ng/mL], P = 0.05) and this was also significant upon multivariate analysis [odds ration (OR): 0.997 (0.994-0.999), P = 0.024], particularly in neonates between 27- and 28-wk gestation. SP-D significantly correlated with the duration of hospital stay (ρ = -0.283, P = 0.002), invasive ventilation (ρ = -0.544, P = 0.001), and total sPLA2 activity (ρ = 0.528, P = 0.008). These findings help understanding the role of SP-D early in life and support further investigation about the role of SP-D in developing BPD.NEW & NOTEWORTHY Surfactant protein-D increases with gestational age and is inversely associated with BPD development. These results have been obtained in the first hours of life of extremely preterm neonates with optimal perinatal care.

Intravenous surfactant protein D inhibits lipopolysaccharide-induced systemic inflammation

BACKGROUND

Surfactant protein D (SP-D) is an innate host defense protein that clears infectious pathogens from the lung and regulates pulmonary host defense cells. SP-D is also detected in lower concentrations in plasma and many other non-pulmonary tissues. Plasma levels of SP-D increase during infection and other proinflammatory states; however, the source and functions of SP-D in the systemic circulation are largely unknown. We hypothesized that systemic SP-D may clear infectious pathogens and regulate host defense cells in extrapulmonary systems.

METHODS

To determine if SP-D inhibited inflammation induced by systemic lipopolysaccharide (LPS), E.coli LPS was administered to mice via tail vein injection with and without SP-D and the inflammatory response was measured.

RESULTS

Systemic SP-D has a circulating half-life of 6 h. Systemic IL-6 levels in mice lacking the SP-D gene were similar to wild type mice at baseline but were significantly higher than wild type mice following LPS treatment (38,000 vs 29,900 ng/ml for 20 mg/kg LPS and 100,700 vs 73,700 ng/ml for 40 mg/kg LPS). In addition, treating wild type mice with purified intravenous SP-D inhibited LPS induced secretion of IL-6 and TNFα in a concentration dependent manner. Inhibition of LPS induced inflammation by SP-D correlated with SP-D LPS binding suggesting SP-D mediated inhibition of systemic LPS requires direct SP-D LPS interactions.

CONCLUSIONS

Taken together, the above results suggest that circulating SP-D decreases systemic inflammation and raise the possibility that a physiological purpose of increasing systemic SP-D levels during infection is to scavenge systemic infectious pathogens and limit inflammation-induced tissue injury.

Magnetic Resonance Imaging-Based Evaluation of Anatomy and Outcome Prediction in Infants with Esophageal Atresia

INTRODUCTION

There is currently no validated diagnostic modality to characterize the anatomy and predict outcomes of tracheal esophageal defects, such as esophageal atresia (EA) and tracheal esophageal fistulas (TEFs). We hypothesized that ultra-short echo-time MRI would provide enhanced anatomic information allowing for evaluation of specific EA/TEF anatomy and identification of risk factors that predict outcome in infants with EA/TEF.

METHODS

In this observational study, 11 infants had pre-repair ultra-short echo-time MRI of the chest completed. Esophageal size was measured at the widest point distal to the epiglottis and proximal to the carina. Angle of tracheal deviation was measured by identifying the initial point of deviation and the farthest lateral point proximal to the carina.

RESULTS

Infants without a proximal TEF had a larger proximal esophageal diameter (13.5 ± 5.1 mm vs. 6.8 ± 2.1 mm, p = 0.07) when compared to infants with a proximal TEF. The angle of tracheal deviation in infants without a proximal TEF was larger than infants with a proximal TEF (16.1 ± 6.1° vs. 8.2 ± 5.4°, p = 0.09) and controls (16.1 ± 6.1° vs. 8.0 ± 3.1°, p = 0.005). An increase in the angle of tracheal deviation was positively correlated with duration of post-operative mechanical ventilation (Pearson r = 0.83, p < 0.002) and total duration of post-operative respiratory support (Pearson r = 0.80, p = 0.004).

DISCUSSION

These results demonstrate that infants without a proximal TEF have a larger proximal esophagus and a greater angle of tracheal deviation which is directly correlated with the need for longer post-operative respiratory support. Additionally, these results demonstrate that MRI is a useful tool to assess the anatomy of EA/TEF.

Tracheostomy prediction model in neonatal bronchopulmonary dysplasia via lung and airway MRI

RATIONALE

Clinical management of neonatal bronchopulmonary dysplasia (BPD) is often imprecise and can vary widely between different institutions and providers, due to limited objective measurements of disease pathology severity. There is critical need to improve guidance on the application and timing of interventional treatments, such as tracheostomy.

OBJECTIVES

To generate an imaging-based clinical tool for early identification of those patients with BPD who are likely to require later tracheostomy and long-term mechanical ventilation.

METHODS

We conducted a prospective cohort study of n = 61 infants (55 BPD, 6 preterm non-BPD). Magnetic resonance imaging (MRI) scores of lung parenchymal disease were used to create a binomial logistic regression model for predicting tracheostomy requirement. This model was further investigated using clinical variables and MRI-quantified tracheomalacia (TM).

MEASUREMENTS AND MAIN RESULTS

A model for predicting tracheostomy requirement was created using MRI parenchymal score. This model had 89% accuracy, 100% positive predictive value (PPV), and 85% negative predictive value (NPV), compared with 84%, 60%, and 83%, respectively, when using only relevant clinical variables. In a subset of patients with airway MRI (n = 36), a model including lung and TM measurements had 83% accuracy, 92% PPV, and 78% NPV.

CONCLUSIONS

MRI-based measurements of parenchymal disease and TM can be used to predict need for tracheostomy in infants with BPD, more accurately than clinical factors alone. This prediction model has strong potential as a clinical tool for physicians and families for early determination of tracheostomy requirement.

Magnetic Resonance Imaging Assessment of Pulmonary Vascularity in Infants with Congenital Diaphragmatic Hernia: A Novel Tool for Direct Assessment of Severity of Pulmonary Hypertension and Hypoplasia

OBJECTIVES

To assess the feasibility of magnetic resonance imaging (MRI) for postnatal assessment of pulmonary vascularity in infants with congenital diaphragmatic hernia (CDH).

STUDY DESIGN

Infants with prenatally diagnosed CDH (n = 24) received postnatal pulmonary MRI. Infants with nonpulmonary birth defects served as controls (n = 5). Semiautomatic segmentation was performed to obtain total vascular volume using time of flight images to assess vascularity.

RESULTS

Average vascular density (vascular volume/lung volume) in control infants was 0.23 ± 0.06 mm³/mm³ compared with 0.18 ± 0.06 mm³/mm³ in infants with CDH is (P = .09). When stratified further based on CDH severity, the difference between control infants and moderate CDH group was statistically significant. (0.23 mm³/mm³ vs 0.15 mm³/mm³, P = .01). Ipsilateral vascular density on MRI in infants with CDH significantly correlated with the prenatal pulmonary hypertensive index (P = .0004, Spearman R = +0.87) and with number of days on mechanical ventilation (P = .04, Spearman R = -0.44), total days on inhaled nitric oxide (P = .02, Spearman R = -0.47), use of epoprostenol for acute pulmonary hypertension (PH) (0.14 mm³/mm³ vs 0.20 mm³/mm³, P = .005), and use of sildenafil for chronic PH (0.15 mm³/mm³ vs 0.19 mm³/mm³, P = .03).

CONCLUSIONS

Our results suggest that postnatal pulmonary vascularity assessed by MRI strongly correlates with prenatal and postnatal markers of PH severity and that pulmonary vascularity may serve as a direct measure of pulmonary vascular hypoplasia in infants with CDH.

Full-Length Recombinant hSP-D Binds and Inhibits SARS-CoV-2

SARS-CoV-2 infection of host cells is driven by binding of the SARS-CoV-2 spike-(S)-protein to lung type II pneumocytes, followed by virus replication. Surfactant protein SP-D, member of the front-line immune defense of the lungs, binds glycosylated structures on invading pathogens such as viruses to induce their clearance from the lungs. The objective of this study is to measure the pulmonary SP-D levels in COVID-19 patients and demonstrate the activity of SP-D against SARS-CoV-2, opening the possibility of using SP-D as potential therapy for COVID-19 patients. Pulmonary SP-D concentrations were measured in bronchoalveolar lavage samples from patients with corona virus disease 2019 (COVID-19) by anti-SP-D ELISA. Binding assays were performed by ELISAs. Protein bridge and aggregation assays were performed by gel electrophoresis followed by silver staining and band densitometry. Viral replication was evaluated in vitro using epithelial Caco-2 cells. Results indicate that COVID-19 patients (n = 12) show decreased pulmonary levels of SP-D (median = 68.9 ng/mL) when compared to levels reported for healthy controls in literature. Binding assays demonstrate that SP-D binds the SARS-CoV-2 glycosylated spike-(S)-protein of different emerging clinical variants. Binding induces the formation of protein bridges, the critical step of viral aggregation to facilitate its clearance. SP-D inhibits SARS-CoV-2 replication in Caco-2 cells (EC90 = 3.7 μg/mL). Therefore, SP-D recognizes and binds to the spike-(S)-protein of SARS-CoV-2 in vitro, initiates the aggregation, and inhibits viral replication in cells. Combined with the low levels of SP-D observed in COVID-19 patients, these results suggest that SP-D is important in the immune response to SARS-CoV-2 and that rhSP-D supplementation has the potential to be a novel class of anti-viral that will target SARS-CoV-2 infection.

Developmental basis of trachea-esophageal birth defects

Trachea-esophageal defects (TEDs), including esophageal atresia (EA), tracheoesophageal fistula (TEF), and laryngeal-tracheoesophageal clefts (LTEC), are a spectrum of life-threatening congenital anomalies in which the trachea and esophagus do not form properly. Up until recently, the developmental basis of these conditions and how the trachea and esophagus arise from a common fetal foregut was poorly understood. However, with significant advances in human genetics, organoids, and animal models, and integrating single cell genomics with high resolution imaging, we are revealing the molecular and cellular mechanisms that orchestrate tracheoesophageal morphogenesis and how disruption in these processes leads to birth defects. Here we review the current understanding of the genetic and developmental basis of TEDs. We suggest future opportunities for integrating developmental mechanisms elucidated from animals and organoids with human genetics and clinical data to gain insight into the genotype-phenotype basis of these heterogeneous birth defects. Finally, we envision how this will enhance diagnosis, improve treatment, and perhaps one day, lead to new tissue replacement therapy.

Surfactant protein D and bronchopulmonary dysplasia: a new way to approach an old problem

Surfactant protein D (SP-D) is a collectin protein synthesized by alveolar type II cells in the lungs. SP-D participates in the innate immune defense of the lungs by helping to clear infectious pathogens and modulating the immune response. SP-D has shown an anti-inflammatory role by down-regulating the release of pro-inflammatory mediators in different signaling pathways such as the TLR4, decreasing the recruitment of inflammatory cells to the lung, and modulating the oxidative metabolism in the lungs. Recombinant human SP-D (rhSP-D) has been successfully produced mimicking the structure and functions of native SP-D. Several in vitro and in vivo experiments using different animal models have shown that treatment with rhSP-D reduces the lung inflammation originated by different insults, and that rhSP-D could be a potential treatment for bronchopulmonary dysplasia (BPD), a rare disease for which there is no effective therapy up to date. BPD is a complex disease in preterm infants whose incidence increases with decreasing gestational age at birth. Lung inflammation, which is caused by different prenatal and postnatal factors like infections, lung hyperoxia and mechanical ventilation, among others, is the key player in BPD. Exacerbated inflammation causes lung tissue injury that results in a deficient gas exchange in the lungs of preterm infants and frequently leads to long-term chronic lung dysfunction during childhood and adulthood. In addition, low SP-D levels and activity in the first days of life in preterm infants have been correlated with a worse pulmonary outcome in BPD. Thus, SP-D mediated functions in the innate immune response could be critical aspects of the pathogenesis in BPD and SP-D could inhibit lung tissue injury in this preterm population. Therefore, administration of rhSP-D has been proposed as promising therapy that could prevent BPD.

Case Report: Esophageal Bronchus in a Neonate, With Image, Histological, and Molecular Analysis

In this case report, we describe the clinical course of a neonate who presented initially with respiratory distress and later with choking during feeding. He was subsequently found to have an esophageal bronchus to the right upper lung lobe, a rare communicating bronchopulmonary foregut malformation. Histological and molecular analysis of the fistula and distal tissues revealed that the proximal epithelium from the esophageal bronchus has characteristics of both esophageal and respiratory epithelia. Using whole exome sequencing of the patient's and parent's DNA, we identified gene variants that are predicted to impact protein function and thus could potentially contribute to the phenotype. These will be the subject of future functional analysis.

Factors that Influence Longitudinal Growth from Birth to 18 Months of Age in Infants with Gastroschisis

OBJECTIVE

This study aimed to investigate factors that influence growth in infants with gastroschisis.

STUDY DESIGN

Growth parameters at birth, discharge, 6, 12, and 18 months of age were collected from 42 infants with gastroschisis.

RESULTS

The mean z-scores for weight, length, and head circumference were below normal at birth and decreased between birth and discharge. Lower gestational age correlated with a worsening change in weight z-score from birth to discharge (rho 0.38, p = 0.01), but not with the change in weight z-score from discharge to 18 months (rho 0.04, p = 0.81). There was no correlation between the day of life when the enteral feeds were started and the change in weight z-score from birth to discharge (rho 0.12, p = 0.44) or discharge to 18 months (rho -0.15, p = 0.41).

CONCLUSION

Our study demonstrates that infants with gastroschisis experience a significant decline in weight z-score between birth and discharge, and start to catch up on all growth parameters after discharge. Prematurity in gastroschisis infants is associated with a greater risk for weight loss during this time. This information emphasizes the importance of minimizing weight loss prior to discharge in premature infants with gastroschisis and highlights the need for optimal management strategies for these infants.

Magentic Resonance Imaging Evaluation of Regional Lung Vts in Severe Neonatal Bronchopulmonary Dysplasia

Rationale: Bronchopulmonary dysplasia is a heterogeneous lung disease characterized by regions of cysts and fibrosis, but methods for evaluating lung function are limited to whole lung rather than specific regions of interest.Objectives: Respiratory-gated, ultrashort echo time magnetic resonance imaging was used to test the hypothesis that cystic regions of the lung will exhibit a quantifiable Vt that will correlate with ventilator settings and clinical outcomes.Methods: Magnetic resonance images of 17 nonsedated, quiet-breathing infants with severe bronchopulmonary dysplasia were reconstructed into end-inspiration and end-expiration images. Cysts were identified and measured by using density threshold combined with manual identification and segmentation. Regional Vts were calculated by subtracting end-expiration from end-inspiration volumes in total lung, noncystic lung, total-cystic lung, and individual large cysts.Measurements and Main Results: Cystic lung areas averaged larger Vts than noncystic lung when normalized by volume (0.8 ml Vt/ml lung vs. 0.1 ml Vt/ml lung, P < 0.002). Cyst Vt correlates with cyst size (P = 0.012 for total lung cyst and P < 0.002 for large cysts), although there was variability between individual cyst Vt, with 22% of cysts demonstrating negative Vt. Peak inspiratory pressure positively correlated with total lung Vt (P = 0.027) and noncystic Vt (P = 0.015) but not total lung cyst Vt (P = 0.8). Inspiratory time and respiratory rate did not improve Vt of any analyzed lung region.Conclusions: Cystic lung has greater normalized Vt when compared with noncystic lung. Ventilator pressure increases noncystic lung Vt, but inspiratory time does not correlate with Vt of normal or cystic lung.

Cardiovascular magnetic resonance imaging derived septal curvature in neonates with bronchopulmonary dysplasia associated pulmonary hypertension

BACKGROUND

Bronchopulmonary dysplasia (BPD) associated with pulmonary hypertension (PH) is a significant source of morbidity and mortality in premature infants. Recent advances have allowed the use of cardiovascular magnetic resonance (CMR) in the assessment of respiratory and cardiac disease in infants with BPD. In adults and older pediatric patients, decreased CMR interventricular septal curvature correlates with increased mean pulmonary artery pressure and pulmonary vascular resistance. The current study sought to determine the relationship of CMR derived septal curvature in neonates with BPD and BPD-PH with a need for PH therapy.

METHODS

Forty moderate or severe BPD and 12 mild BPD or control infants were imaged without contrast between 38 and 47 weeks post-menstrual age on a neonatal-sized, neonatal intensive care unit-sited 1.5 T CMR scanner. CMR indices including eccentricity index (CMR-EI) and septal curvature were measured and compared to BPD severity and clinical outcomes including hospital length of stay (LOS), duration of respiratory support, respiratory support level at discharge and PH therapy.

RESULTS

CMR-EI was directly associated and septal curvature was inversely associated with BPD severity. In a univariate analysis, CMR-EI and septal curvature were associated with increased hospital LOS, duration of respiratory support, respiratory support at hospital discharge, and need for PH therapy. In multivariable analysis CMR-EI was associated with hospital LOS and duration of respiratory support and septal curvature was associated with respiratory support at hospital discharge. Septal curvature was the only clinical or CMR variable associated with need for PH therapy (R2 = 0.66, p = 0.0014) in multivariable analysis demonstrating improved discrimination beyond CMR-EI.

CONCLUSIONS

CMR derived septal curvature correlates significantly with clinical outcomes including hospital LOS, duration of respiratory support, respiratory support level at hospital discharge, and PH therapy in neonates with BPD and BPD-PH. Further, CMR derived septal curvature demonstrated improved discrimination of need for PH therapy and respiratory support at discharge compared to clinical variables and other CMR indices, supporting septal curvature as a non-invasive marker of PH in this population with potential to guide management strategies.

Structure and activity of human surfactant protein D from different natural sources

Surfactant protein D (SP-D) is a C-type lectin that participates in the innate immune defense of lungs. It binds pathogens through its carbohydrate recognition domain in a calcium-dependent manner. Human surfactant protein D (hSP-D) has been routinely obtained from bronchoalveolar lavage of patients suffering from pulmonary alveolar proteinosis (PAP) and from amniotic fluid (AF). As a consequence of the disease, hSP-D obtained from PAP is found in higher amounts and is mainly composed of higher order oligomeric forms. However, PAP-hSP-D has never been directly compared with nonpathological human protein in terms of structure and biological activity. Moreover, the quantitative distribution of the different hSP-D oligomeric forms in human protein obtained from a natural source has never been evaluated. In this work, we have determined the quantitative distribution of AF-hSP-D oligomers, characterized the sugars attached through the N-glycosylation site of the protein, and compared the activity of hSP-D from AF and PAP with respect to their ability to bind and agglutinate bacteria. We have found that fuzzy balls (40%) are the most abundant oligomeric form in AF-hSP-D, very closely followed by dodecamers (33%), with both together constituting 73% of the protein mass. The glycan attached to the N-glycosylation site was found to be composed of fucose, galactose, sialic acid, and N-acetylglucosamine. Finally, in the functional assays performed, hSP-D obtained from PAP showed higher potency, probably as a consequence of its higher proportion of large oligomers compared with hSP-D from AF.

Functional characterization of the different oligomeric forms of human surfactant protein SP-D

Surfactant Protein D (SP-D) is a collectin protein that participates in the innate immune defense of the lungs. SP-D mediates the clearance of invading microorganisms by opsonization, aggregation or direct killing, which are lately removed by macrophages. SP-D is found as a mixture of trimers, hexamers, dodecamers and higher order oligomers, "fuzzy balls". However, it is unknown whether there are differences between these oligomeric forms in functions, activity or potency. In the present work, we have obtained fractions enriched in trimers, hexamers and fuzzy balls of full-length recombinant human (rh) SP-D by size exclusion chromatography, in a sufficient amount to perform functional assays. We have evaluated the differences in protein lectin-dependent activity relative to aggregation and binding to E. coli, one of the ligands of SP-D in vivo. Fuzzy balls are the most active oligomeric form in terms of binding and aggregation of bacteria, achieving 2-fold binding higher than hexamers and 50% bacteria aggregation at very short times. Hexamers, recently described as a defined oligomeric form of the protein, have never been isolated or tested in terms of protein activity. rhSP-D hexamers efficiently bind and aggregate bacteria, achieving 50-60% aggregation at final time point and high protein concentrations. Nevertheless, trimers are not able to aggregate bacteria, although they bind to them. Therefore, SP-D potency, in functions that relay on the C-lectin activity of the protein, is proportional to the oligomeric state of the protein.

Feeding Tolerance, Intestinal Motility, and Superior Mesenteric Artery Blood Flow in Infants with Gastroschisis

OBJECTIVE

The aim of this study was to determine the relationship of superior mesenteric artery (SMA) blood flow and intestinal motility with feeding tolerance in infants with gastroschisis.

STUDY DESIGN

This was a prospective observational cohort study of 23 infants with gastroschisis. Magnetic resonance images were obtained at abdominal wall closure, initiation of feeds, and full feeds. Motility and SMA flow data were correlated with feeding tolerance.

RESULT

All infants had abnormal motility, and most continued with abnormal motility despite achieving full feeds. Increased SMA flow at the time of abdominal wall closure was found to be significantly related to the earlier achievement of full feeds (ρ = -0.45, p = 0.05) and trended towards earlier initiation of feeds (ρ = -0.36, p = 0.13), shorter parenteral nutrition days (ρ = -0.42, p = 0.07), and earlier discharge (ρ = -0.41, p = 0.08).

CONCLUSION

Increased SMA blood flow at the time of abdominal wall closure is positively correlated with feeding tolerance, suggesting the importance of initial intestinal perfusion in the pathophysiology for feeding intolerance and intestinal dysmotility in gastroschisis.

Cardiac Magnetic Resonance Imaging Evaluation of Neonatal Bronchopulmonary Dysplasia-associated Pulmonary Hypertension

Rationale: Patients with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) have increased morbidity and mortality. Noninvasive assessment relies on echocardiograms (echos), which are technically challenging in this population. Improved assessment could augment decisions regarding PH therapies.Objectives: We hypothesized that neonatal cardiac magnetic resonance imaging (MRI) will correlate with BPD severity and predict short-term clinical outcomes, including need for PH therapies for infants with BPD.Methods: A total of 52 infants (31 severe BPD, 9 moderate BPD, and 12 with either mild or no BPD) were imaged between 39 and 47 weeks postmenstrual age on a neonatal-sized, neonatal ICU-sited 1.5-T magnetic resonance (MR) scanner. MR left ventricular eccentricity index (EI), main pulmonary artery-to-aorta (PA/AO) diameter ratio, and pulmonary arterial blood flow were determined. Echos obtained for clinical indications were reviewed. MRI and echo indices were compared with BPD severity and clinical outcomes, including length of stay (LOS), duration of respiratory support, respiratory support at discharge, and PH therapy.Measurements and Main Results: PA/AO ratio increased with BPD severity. Increased PA/AO ratio, MR-EI, and echo-EIs were associated with increased LOS and duration of respiratory support. No correlation was seen between pulmonary arterial blood flow and BPD outcomes. Controlling for gestational age, birth weight, and BPD severity, MR-EI was associated with LOS and duration of respiratory support. Increased PA/AO ratio and MR-EI were associated with PH therapy during hospitalization and at discharge.Conclusions: MRI can provide important image-based measures of cardiac morphology that relate to disease severity and clinical outcomes in neonates with BPD.

Ultrashort Echo-Time MRI for the Assessment of Tracheomalacia in Neonates

BACKGROUND

Bronchoscopy is the gold standard for evaluating tracheomalacia; however, reliance on an invasive procedure limits understanding of normal airway dynamics. Self-gated ultrashort echo-time MRI (UTE MRI) can assess tracheal dynamics but has not been rigorously evaluated.

METHODS

This study was a validation of UTE MRI diagnosis of tracheomalacia in neonates using bronchoscopy as the gold standard. Bronchoscopies were reviewed for the severity and location of tracheomalacia based on standardized criteria. The percent change in cross-sectional area (CSA) of the trachea between end-inspiration and end-expiration was determined by UTE MRI, and receiver-operating curves were used to determine the optimal cutoff values to predict tracheomalacia and determine positive and negative predictive values.

RESULTS

Airway segments with tracheomalacia based on bronchoscopy had a more than threefold change in CSA measured from UTE MRI (54.4 ± 56.1% vs 14.8 ± 19.5%; P < .0001). UTE MRI correlated moderately with bronchoscopy for tracheomalacia severity (ρ = 0.39; P = .0001). Receiver-operating curves, however, showed very good ability of UTE MRI to identify tracheomalacia (area under the curve, 0.78). A "loose" definition (> 20% change in CSA) of tracheomalacia had good sensitivity (80%) but low specificity (64%) for identifying tracheomalacia based on UTE MRI, whereas a "strict" definition (> 40% change in CSA) was poorly sensitive (48%) but highly specific (93%).

CONCLUSIONS

Self-gated UTE MRI can noninvasively assess tracheomalacia in neonates without sedation, ionizing radiation, or increased risk. This technique overcomes major limitations of other diagnostic modalities and may be suitable for longitudinal population studies of tracheal dynamics.

Evaluation of Lung Injury in Infants with Congenital Diaphragmatic Hernia

BACKGROUND/PURPOSE

The presence of lung injury and the factors that contribute to it in infants with congenital diaphragmatic hernia (CDH) have not been objectively measured during their clinical course. In adults with acute respiratory distress syndrome, higher serum levels of surfactant protein D (SP-D) are linked to lung injury and worse outcomes. We hypothesized that serum SP-D levels would be elevated in CDH infants and that the levels would correlate to the amount of lung injury present.

METHODS

In this retrospective cohort study, serum SP-D levels were analyzed in 37 CDH infants and 5 control infants using a commercially available enzyme-linked immunosorbent assay kit.

RESULTS

Infants with more severe CDH had a statistically significant increase (p < 0.001) in serum SP-D over their first month of life. SP-D levels in CDH infants were similar to control infants while on extracorporeal membrane oxygenation (ECMO) but were 2.5-fold higher (p = 0.03) than controls following ECMO termination. SP-D levels increased 1.6-fold following surgical repair of the diaphragm and were significantly higher in the second week following surgery when compared to pre-operative levels (p < 0.03).

CONCLUSIONS

These results demonstrate that CDH infants experience lung injury during the first week of life, around the time of surgery, and at the time of ECMO termination. Level II prognosis study.

Neonatal lung growth in congenital diaphragmatic hernia: evaluation of lung density and mass by pulmonary MRI

BACKGROUND

Outcomes of infants with congenital diaphragmatic hernia (CDH) are primarily dependent on the severity of pulmonary hypoplasia. It is previously unknown whether postnatal lung growth in infants with CDH represents true parenchymal lung growth or merely an expansion in volume of the existing tissue. We hypothesized that lung volume growth in CDH infants will be accompanied by an increase in lung mass and that CDH infants will demonstrate accelerated catch-up growth of the more hypoplastic lung.

METHODS

We used fetal and post-CDH repair MRI of 12 infants to measure lung volume and density, which was used to calculate lung mass.

RESULTS

The average increase in right lung mass was 1.1 ± 1.1 g/week (p = 0.003) and the average increase in left lung mass was 1.8 ± 0.7 g/week (p < 0.001). When the ratio of left-to-right lung mass of the prenatal MRI was compared to post-repair MRI, the ratio significantly increased in all infants with average prenatal and post-repair ratios of 0.30 and 0.73, respectively (p = 0.002).

CONCLUSION

Lung growth in infants with CDH is indeed growth in lung mass (i.e. parenchyma), and the lungs demonstrate catch-up growth (i.e., increased rate of growth in the more hypoplastic ipsilateral lung).

Elevated lung volumes in neonates with bronchopulmonary dysplasia measured via MRI

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of prematurity defined by requirement for respiratory support at 36 weeks postmenstrual age (PMA), but structural sequelae like lung hyperinflation are often not quantified. Quiet-breathing, nonsedated magnetic resonance imaging (MRI) allows tomographic quantification of lung volumes and densities. We hypothesized that functional residual capacity (FRC) and intrapleural volume (IV) are increased in BPD and correlate with qualitative radiological scoring of hyperinflation.

METHODS

Ultrashort echo time (UTE) MRI of 17 neonates (acquired at ~39 weeks PMA) were reconstructed at end-expiration and end-inspiration via the time course of the k₀ point in k-space. Images were segmented to determine total lung, tidal, parenchymal tissue, and vascular tissue volumes. FRC was calculated by subtracting parenchymal and vascular tissue volumes from IV. Respiratory rate (RR) was calculated via the UTE respiratory waveform, yielding estimates of minute ventilation when combined with tidal volumes (TVs). Two radiologists scored hyperinflation on the MR images.

RESULTS

IV at FRC increased in BPD: for control, mild, and severe (patients the median volumes were 32.8, 33.5, and 50.9 mL/kg, respectively. TV (medians: 2.21, 3.64, and 4.84 mL/kg) and minute ventilation (medians: 493, 750, and 991 mL/min) increased with increasing severity of BPD (despite decreasing RR, medians: 75.6, 63.0, and 56.1 breaths/min). FRC increased with increasing severity of BPD (39.3, 38.3, and 56.0 mL, respectively). Findings were consistent with increased hyperinflation scored by radiologists.

CONCLUSIONS

This study demonstrates that UTE MRI can quantify hyperinflation in neonatal BPD and that lung volumes significantly increase with disease severity.

Quantitative Assessment of Regional Dynamic Airway Collapse in Neonates via Retrospectively Respiratory-Gated 1 H Ultrashort Echo Time MRI

BACKGROUND

Neonatal dynamic tracheal collapse (tracheomalacia, TM) is a common and serious comorbidity in infants, particularly those with chronic lung disease of prematurity (bronchopulmonary dysplasia, BPD) or congenital airway or lung-related conditions such as congenital diaphragmatic hernia (CDH), but the underlying pathology, impact on clinical outcomes, and response to therapy are not well understood. There is a pressing clinical need for an accurate, objective, and safe assessment of neonatal TM.

PURPOSE

To use retrospectively respiratory-gated ultrashort echo-time (UTE) MRI to noninvasively analyze moving tracheal anatomy for regional, quantitative evaluation of dynamic airway collapse in quiet-breathing, nonsedated neonates.

STUDY TYPE

Prospective.

POPULATION/SUBJECTS

Twenty-seven neonatal subjects with varying respiratory morbidities (control, BPD, CDH, abnormal polysomnogram).

FIELD STRENGTH/SEQUENCE

High-resolution 3D radial UTE MRI (0.7 mm isotropic) on 1.5T scanner sited in the neonatal intensive care unit.

ASSESSMENT

Images were retrospectively respiratory-gated using the motion-modulated time-course of the k-space center. Tracheal surfaces were generated from segmentations of end-expiration/inspiration images and analyzed geometrically along the tracheal length to calculate percent-change in luminal cross-sectional area (A % ) and ratio of minor-to-major diameters at end-expiration (r D,exp ). Geometric results were compared to clinically available bronchoscopic findings (n = 14).

STATISTICAL TESTS

Two-sample t-test.

RESULTS

Maximum A % significantly identified subjects with/without a bronchoscopic TM diagnosis (with: 46.9 ± 10.0%; without: 27.0 ± 5.8%; P < 0.001), as did minimum r D,exp (with: 0.346 ± 0.146; without: 0.671 ± 0.218; P = 0.008). Subjects with severe BPD exhibited a far larger range of minimum r D,exp than subjects with mild/moderate BPD or controls (0.631 ± 0.222, 0.782 ± 0.075, and 0.776 ± 0.030, respectively), while minimum r D,exp was reduced in CDH subjects (0.331 ± 0.171) compared with controls (P < 0.001).

DATA CONCLUSION

Respiratory-gated UTE MRI can quantitatively and safely evaluate neonatal dynamic tracheal collapse, as validated with the clinical standard of bronchoscopy, without requiring invasive procedures, anesthesia, or ionizing radiation.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;49:659-667.

Neonatal Pulmonary Magnetic Resonance Imaging of Bronchopulmonary Dysplasia Predicts Short-Term Clinical Outcomes

RATIONALE

Bronchopulmonary dysplasia (BPD) is a serious neonatal pulmonary condition associated with premature birth, but the underlying parenchymal disease and trajectory are poorly characterized. The current National Institute of Child Health and Human Development (NICHD)/NHLBI definition of BPD severity is based on degree of prematurity and extent of oxygen requirement. However, no clear link exists between initial diagnosis and clinical outcomes.

OBJECTIVES

We hypothesized that magnetic resonance imaging (MRI) of structural parenchymal abnormalities will correlate with NICHD-defined BPD disease severity and predict short-term respiratory outcomes.

METHODS

A total of 42 neonates (20 severe BPD, 6 moderate, 7 mild, 9 non-BPD control subjects; 40 ± 3-wk postmenstrual age) underwent quiet-breathing structural pulmonary MRI (ultrashort echo time and gradient echo) in a neonatal ICU-sited, neonatal-sized 1.5 T scanner, without sedation or respiratory support unless already clinically prescribed. Disease severity was scored independently by two radiologists. Mean scores were compared with clinical severity and short-term respiratory outcomes. Outcomes were predicted using univariate and multivariable models, including clinical data and scores.

MEASUREMENTS AND MAIN RESULTS

MRI scores significantly correlated with severities and predicted respiratory support at neonatal ICU discharge (P < 0.0001). In multivariable models, MRI scores were by far the strongest predictor of respiratory support duration over clinical data, including birth weight and gestational age. Notably, NICHD severity level was not predictive of discharge support.

CONCLUSIONS

Quiet-breathing neonatal pulmonary MRI can independently assess structural abnormalities of BPD, describe disease severity, and predict short-term outcomes more accurately than any individual standard clinical measure. Importantly, this nonionizing technique can be implemented to phenotype disease, and has potential to serially assess efficacy of individualized therapies.

Evaluation of Early Onset Sepsis, Complete Blood Count, and Antibiotic Use in Gastroschisis

OBJECTIVE

Gastroschisis is a congenital defect in which the abdominal viscera herniate through the abdominal wall. In this population, antibiotics are often initiated immediately following delivery; however, this may be unnecessary as infections typically develop as a consequence of chronic issues in gastroschisis. The objective of this study was to evaluate the incidence of culture positive early onset sepsis, the reliability of the immature to mature neutrophil count (I:T) ratio as an infectious biomarker, and antibiotic use in infants with gastroschisis.

STUDY DESIGN

This retrospective chart review analyzed clinical data from 103 infants with gastroschisis and 103 weight-matched controls that were evaluated for early onset infection.

RESULTS

Compared with the control group, there was a significantly increased percentage of infants with an I:T ratio > 0.2 in the gastroschisis group (43% vs. 12%, p < 0.001) and an increased percentage of infants exposed to greater than 5 days of antibiotics regardless of their I:T ratio (75% vs. 6%, p < 0.001). There were no episodes of culture positive early onset sepsis in either group.

CONCLUSION

Our results indicate that I:T ratio is not a reliable marker of infection in gastroschisis, and suggest that empiric septic evaluation and antibiotic use, immediately following delivery in gastroschisis infants, may be unnecessary.

Diagnosing Infection in a Neonate Using Whole-Body Screening Magnetic Resonance Imaging

The location of invasive infections is difficult to detect in infants, in part due to their inability to localize signs and symptoms. However, identifying the location often significantly alters clinical management by extending the duration of antibiotic therapy or revealing a source requiring surgical intervention. Compared with commonly used first-line imaging techniques such as radiographs and ultrasounds, MRI has higher sensitivity for identifying invasive infections and allows for simultaneous evaluation of multiple foci. We present 2 cases in which whole-body screening MRI was used in neonates to identify invasive sources of infection, including one in which traditional modalities failed to detect multiple clinically significant sources. We posit that whole-body screening MRI merits consideration as a potential first-line imaging method when investigating invasive infections in infants.

Pre- and post-operative visualization of neonatal esophageal atresia/tracheoesophageal fistula via magnetic resonance imaging

Esophageal atresia (EA) is a relatively uncommon congenital anomaly, often observed in conjunction with tracheoesophageal fistula (TEF). Surgical repair in neonates typically takes place with little information about the pre-existing EA/TEF structure because there are currently no acceptable tools for evaluating EA/TEF anatomy prior to repair; chest x-ray radiograph does not identify malformation sub-type or gap length, while x-ray computed tomography (CT) demonstrate an unacceptably high exposure to ionizing radiation. There is a need for safe imaging methods to evaluate pre-operative EA/TEF anatomy, which would add value in surgical planning; this need may be met with high-resolution structural MRI. We report three cases of Type-C EA/TEF in neonates. Patients were imaged prior to surgical repair using high-resolution ultrashort echo time (UTE) magnetic resonance imaging (MRI) to visualize tracheoesophageal anatomy and allow for informed surgical planning and risk management. One of the three patients was imaged post-repair to evaluate surgical efficacy and evolution of the tracheoesophageal anatomy.

Evaluation of Neonatal Lung Volume Growth by Pulmonary Magnetic Resonance Imaging in Patients with Congenital Diaphragmatic Hernia

OBJECTIVE

To evaluate postnatal lung volume in infants with congenital diaphragmatic hernia (CDH) and determine if a compensatory increase in lung volume occurs during the postnatal period.

STUDY DESIGN

Using a novel pulmonary magnetic resonance imaging method for imaging neonatal lungs, the postnatal lung volumes in infants with CDH were determined and compared with prenatal lung volumes obtained via late gestation magnetic resonance imaging.

RESULTS

Infants with left-sided CDH (2 mild, 9 moderate, and 1 severe) were evaluated. The total lung volume increased in all infants, with the contralateral lung increasing faster than the ipsilateral lung (mean ± SD: 4.9 ± 3.0 mL/week vs 3.4 ± 2.1 mL/week, P = .005). In contrast to prenatal studies, the volume of lungs of infants with more severe CDH grew faster than the lungs of infants with more mild CDH (Spearman's ρ=-0.086, P = .01). Although the contralateral lung volume grew faster in both mild and moderate groups, the majority of total lung volume growth in moderate CDH came from increased volume of the ipsilateral lung (42% of total lung volume increase in the moderate group vs 32% of total lung volume increase in the mild group, P = .09). Analysis of multiple clinical variables suggests that increased weight gain was associated with increased compensatory ipsilateral lung volume growth (ρ = 0.57, P = .05).

CONCLUSIONS

These results suggest a potential for postnatal catch-up growth in infants with pulmonary hypoplasia and suggest that weight gain may increase the volume growth of the more severely affected lung.

Quantification of neonatal lung parenchymal density via ultrashort echo time MRI with comparison to CT

PURPOSE

To demonstrate that ultrashort echo time (UTE) magnetic resonance imaging (MRI) can achieve computed tomography (CT)-like quantification of lung parenchyma in free-breathing, non-sedated neonates. Because infant CTs are used sparingly, parenchymal disease evaluation via UTE MRI has potential for translational impact.

MATERIALS AND METHODS

Two neonatal control cohorts without suspected pulmonary morbidities underwent either a research UTE MRI (n = 5; 1.5T) or a clinically-ordered CT (n = 9). Whole-lung means and anterior-posterior gradients of UTE-measured image intensity (arbitrary units, au, normalized to muscle) and CT-measured density (g/cm³ ) were compared (Mann-Whitney U-test). Separately, a diseased neonatal cohort (n = 5) with various pulmonary morbidities underwent both UTE MRI and CT. UTE intensity and CT density were compared with Spearman correlations within ∼33 anatomically matched regions of interest (ROIs) in each diseased subject, spanning low- to high-density tissues. Radiological classifications were evaluated in all ROIs, with mean UTE intensities and CT densities compared in each classification.

RESULTS

In control subjects, whole-lung UTE intensities (0.51 ± 0.04 au) were similar to CT densities (0.44 ± 0.09 g/cm³ ) (P = 0.062), as were UTE (0.021 ± 0.020 au/cm) and CT (0.034 ± 0.024 [g/cm³ ]/cm) anterior-posterior gradients (P = 0.351). In diseased subjects' ROIs, significant correlations were observed between UTE and CT (P ≤0.007 in each case). Relative differences between UTE and CT were small in all classifications (4-25%).

CONCLUSION

These results demonstrate a strong association between UTE image intensity and CT density, both between whole-lung tissue in control patients and regional radiological pathologies in diseased patients. This indicates the potential for UTE MRI to longitudinally evaluate neonatal pulmonary disease and to provide visualization of pathologies similar to CT, without sedation/anesthesia or ionizing radiation.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:992-1000.

Retrospective respiratory self-gating and removal of bulk motion in pulmonary UTE MRI of neonates and adults

PURPOSE

To implement pulmonary three-dimensional (3D) radial ultrashort echo-time (UTE) MRI in non-sedated, free-breathing neonates and adults with retrospective motion tracking of respiratory and intermittent bulk motion, to obtain diagnostic-quality, respiratory-gated images.

METHODS

Pulmonary 3D radial UTE MRI was performed at 1.5 tesla (T) during free breathing in neonates and adult volunteers for validation. Motion-tracking waveforms were obtained from the time course of each free induction decay's initial point (i.e., k-space center), allowing for respiratory-gated image reconstructions that excluded data acquired during bulk motion. Tidal volumes were calculated from end-expiration and end-inspiration images. Respiratory rates were calculated from the Fourier transform of the motion-tracking waveform during quiet breathing, with comparison to physiologic prediction in neonates and validation with spirometry in adults.

RESULTS

High-quality respiratory-gated anatomic images were obtained at inspiration and expiration, with less respiratory blurring at the expense of signal-to-noise for narrower gating windows. Inspiration-expiration volume differences agreed with physiologic predictions (neonates; Bland-Altman bias = 6.2 mL) and spirometric values (adults; bias = 0.11 L). MRI-measured respiratory rates compared well with the observed rates (biases = -0.5 and 0.2 breaths/min for neonates and adults, respectively).

CONCLUSIONS

Three-dimensional radial pulmonary UTE MRI allows for retrospective respiratory self-gating and removal of intermittent bulk motion in free-breathing, non-sedated neonates and adults. Magn Reson Med 77:1284-1295, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Neutrophil CD64 as a diagnostic marker of sepsis: impact on neonatal care

OBJECTIVE

The aim of this study is to determine the validity and reliability of neutrophil CD64 in identifying infected infants and to evaluate the impact of this marker on clinical care.

STUDY DESIGN

Neutrophil CD64 index was incorporated in 371 infection evaluations in 234 infants (ages 1-293 days) from 2005 to 2009 and the impact of this change on clinical care was evaluated.

RESULTS

The sensitivity of the neutrophil CD64 assay was 87% in identifying 31 episodes of culture positive sepsis and 83% in identifying 12 infants with ventilator-associated pneumonia. There was no difference in the mean number of antibiotic days in infants with a normal CD64 versus those with a normal complete blood count (CBC) (p = 0.89), but twofold more infants were identified as "not infected" by CD64 than by CBC.

CONCLUSION

CD64 had a high sensitivity for identifying infected infants while also decreasing the number of infants that were exposed to unnecessary antibiotic use.

Octreotide for chylous effusions in congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Chylothorax is a frequent complication in congenital diaphragmatic hernia (CDH) infants and is associated with significant morbidity. The optimal treatment strategy remains unclear. We hypothesize that octreotide decreases chylous effusions in infants with CDH.

METHODS

This is a retrospective study of all infants with CDH admitted to our institution from October 2006 to October 2011.

RESULTS

Eleven (12%) infants developed a chylothorax. Five infants were managed conservatively with thoracostomy and total parenteral nutrition. Six infants were started on octreotide therapy. None of the infants required surgical intervention to stop the effusion. There was no significant difference in survival to discharge, length of stay, or average daily chest tube output between groups. There appeared to be a temporally associated drop in chest tube output upon initiation of octreotide in two infants; however, the overall rate of decline in chest tube drainage was unchanged. In addition, there were infants in the conservative group who demonstrated a similar drop in daily chest tube output despite the absence of octreotide.

CONCLUSIONS

Our data suggest that the majority of chylous effusions in CDH infants resolve with conservative therapy alone.

Subgaleal hemorrhage in a neonate with factor X deficiency following a non-traumatic cesarean section

This case report describes a term infant born by a non-traumatic, non-instrumented cesarean section that presented with respiratory failure and severe metabolic acidosis secondary to subgaleal hemorrhage (SGH). Further evaluation revealed a functional factor X deficiency that was initially treated with fresh frozen plasma infusions. This report is significant for the occurrence of a SGH in a non-traumatic delivery and emphasizes the importance of obtaining a coagulopathy evaluation in patients with similar presentations. In addition, this case suggests that the mechanism of injury that causes SGH may occur more frequently than previously thought, but does not become clinically significant in patients without an underlying coagulopathy.

The congenital diaphragmatic hernia composite prognostic index correlates with survival in left-sided congenital diaphragmatic hernia

PURPOSE

We developed the congenital diaphragmatic hernia congenital prognostic index (CDH-CPI) to incorporate all known prognostic variables into a single composite index to improve prognostic accuracy. The purpose of this study is to examine the ability of the CDH-CPI to predict survival in patients with left-sided congenital diaphragmatic hernia and to determine if the index has a stronger correlation with survival than each of the individual components.

METHODS

A retrospective review of patients with left-sided congenital diaphragmatic hernia between 2004 and 2010 was conducted. Ten prenatal parameters of the CDH-CPI were collected, total score was tabulated, and patients stratified according to total score and survival.

RESULTS

Sixty-four patients with a prenatal diagnosis of left-sided congenital diaphragmatic hernia were identified. Patients with a CDH-CPI score of 8 or higher had a significantly higher survival than patients with a CDH-CPI score of lower than 8. The CDH-CPI has the strongest correlation with survival compared with the individual parameters measured. The CDH-CPI correlates with extracorporeal membrane oxygenation use, and 75% of patients with a score of 5 or lower were placed on extracorporeal membrane oxygenation.

CONCLUSIONS

The CDH-CPI accurately stratifies survival in left-sided congenital diaphragmatic hernia. The amalgamation of 10 prenatal parameters of the CDH-CPI may be a better prenatal predictor than any single prognostic variable currently used.

Pulmonary maturational arrest and death in a patient with pulmonary interstitial glycogenosis

We present the clinical presentation and pathological findings from a term infant with atypical neonatal lung disease. A full term Caucasian male presented at birth with signs of respiratory distress. The respiratory condition continued to deteriorate despite maximum intervention and the patient was placed on ECMO for further cardiorespiratory assistance. An open lung biopsy demonstrated findings consistent with severe lung growth abnormality with non-uniform pulmonary interstitial glycogenosis. The patient consequently developed a pulmonary hemorrhage that required discontinuation of ECMO. The patient died shortly after decannulation. Most literature suggests that PIG is one of the few pediatric interstitial lung diseases that has a favorable prognosis with rare mortality in the absence of co-morbidities. However, the current case suggests prognosis may depend more on the underlying diagnosis than on the histological finding of PIG. In addition, this case may provide insight into the pathogenesis and potential modifiers of this idiopathic disorder.

Late gestation fetal magnetic resonance imaging-derived total lung volume predicts postnatal survival and need for extracorporeal membrane oxygenation support in isolated congenital diaphragmatic hernia

PURPOSE

Magnetic resonance imaging (MRI) has been used as an imaging modality to assess pulmonary hypoplasia in congenital diaphragmatic hernias (CDHs). The objective of this study was to determine if there is a correlation between late gestational fetal MRI-derived total lung volumes (TLVs) and CDH outcomes.

METHODS

From 2006 to 2009, 44 patients met criteria of an isolated CDH with a late gestational MRI evaluation. The prenatal TLV (in milliliters) was obtained between 32 and 34 weeks gestation. The measured study outcomes included survival, need for extracorporeal membrane oxygenation (ECMO), and length of stay.

RESULTS

There were 39 left and 5 right CDH patients. The average TLV was significantly lower for nonsurvivors (P = .01), and there was a significant association between lower TLV and the need for ECMO (P = .0001). When stratified by TLV, patients with a TLV of greater than 40 mL had a 90% survival vs 35% survival for a TLV of less than 20 mL. Furthermore, patients with a TLV greater than 40 mL had a lower rate of ECMO use (10%) than patients with a TLV of less than 20 mL (86%). Shorter length of stay was found to correlate with increasing TLV (P = .022).

CONCLUSION

Late gestation fetal MRI-derived TLV significantly correlates with postnatal survival and need for ECMO. Fetal MRI may be useful for the evaluation of patients who present late in gestation with a CDH.

Surfactant protein D deficiency increases lung injury during endotoxemia

Acute lung injury (ALI) and its severe form, acute respiratory distress syndrome (ARDS), are major causes of acute respiratory failure with high rates of morbidity and mortality. Although surfactant protein (SP)-D plays a critical role in pulmonary innate immunity and several clinical studies suggest that this protein may be implicated in the pathophysiology of ARDS, little is known regarding the function of SP-D in ARDS. In the present study, we induced indirect lung injury by intraperitoneal injection of LPS and direct lung injury by intratracheal injection of LPS in wild-type and Sftpd(-/-) mice to elucidate the role of SP-D during ALI/ARDS. Results indicate that pulmonary levels of IL-6 and TNF-α were higher in Sftpd(-/-) mice when compared with wild-type mice. However, the magnitude of this difference was 10-fold greater after indirect lung injury compared with direct lung injury. After indirect lung injury, there was a 2-fold increase in the number of pulmonary monocyte/macrophages in the Sftpd(-/-) mice when compared with wild-type mice, whereas pulmonary neutrophils were not increased. After indirect injury, the concentration of granulocyte-macrophage colony stimulating factor (GM-CSF) was approximately 5-fold greater in Sftpd(-/-) mice than wild-type mice. In contrast, after direct injury, the concentration of GM-CSF was 20-fold less in Sftpd(-/-) mice than wild-type mice. Despite increased inflammatory cells and markers of inflammation, survival in Sftpd(-/-) mice after indirect lung injury was paradoxically increased. In conclusion, these results suggest that SP-D inhibits pulmonary inflammation and migration of peripheral monocyte/macrophages into the lung through GM-CSF-dependent pathways during indirect lung injury.

Correction of Pulmonary Abnormalities in Sftpd-/- Mice Requires the Collagenous Domain of Surfactant Protein D

Surfactant protein D (SP-D) is a member of the collectin family of innate defense proteins. Members of this family share four distinct structural domains: an N-terminal cross-linking domain, a collagenous domain, a neck region, and a carbohydrate recognition domain. In this study, the function of the collagenous domain was evaluated by expressing a SP-D collagen deletion mutant protein (rSftpdCDM) in wild type and SP-D null mice (Sftpd(-/-)). rSftpdCDM formed disulfide-linked trimers that further oligomerized into higher order structures. The mutant protein effectively bound carbohydrate and aggregated bacteria in vitro. Whereas rSftpdCDM did not disrupt pulmonary morphology or surfactant phospholipid levels in wild type mice, the mutant protein failed to rescue the emphysema or enlarged foamy macrophages that are characteristic of Sftpd(-/-) mice. Moreover, rSftpdCDM partitioned with small aggregate surfactant in a manner similar to SP-D, but rSftpdCDM did not correct the abnormal surfactant ultrastructure or phospholipid levels observed in Sftpd(-/-) mice. In contrast, rSftpdCDM completely corrected viral clearance and the abnormal inflammatory response that occurs following pulmonary influenza A challenge in Sftpd(-/-) mice. Our findings indicate that the collagen domain of SP-D is not required for assembly of disulfide-stabilized oligomers or the innate immune response to viral pathogens. The collagen domain of SP-D is required for the regulation of pulmonary macrophage activation, airspace remodeling, and surfactant lipid homeostasis.

In defense of the lung: surfactant protein A and surfactant protein D

The lung is repeatedly exposed to inhaled particles and pathogens that are cleared by the actions of a multi-component innate host defense system. The pulmonary collectins--surfactant proteins A (SP-A) and D (SP-D)--play important roles in innate host defense by binding and clearing invading microbes from the lung. SP-A and SP-D also influence surfactant homeostasis, contributing to the physical structures of lipids in the alveoli and to the regulation of surfactant function and metabolism. In addition to binding and opsonizing infectious pathogens, SP-A and SP-D bind to the surfaces of host defense cells, promoting or inhibiting immune cell activity through multiple cellular pathways. As a consequence of their physiologic functions, SP-A- and SP-D-dependent pathways are targets for clinical therapies designed to limit the proliferation of microoorgansims and to ameliorate inflammation following pulmonary infection.

Binding of etoposide to topoisomerase II in the absence of DNA: decreased affinity as a mechanism of drug resistance

Despite the prevalence of topoisomerase II-targeted drugs in cancer chemotherapy and the impact of drug resistance on the efficacy of treatment, interactions between these agents and topoisomerase II are not well understood. Therefore, to further define interactions between anticancer drugs and the type II enzyme, a nitrocellulose filter assay was used to characterize the binding of etoposide to yeast topoisomerase II. Results indicate that etoposide binds to the enzyme in the absence of DNA. The apparent Kd value for the interaction was approximately 5 microM drug. Etoposide also bound to ytop2H1012Y, a mutant yeast type II enzyme that is approximately 3-4-fold resistant to etoposide. However, the apparent Kd value for the drug (approximately 16 microM) was approximately 3 times higher than that determined for wild-type topoisomerase II. Although it has been widely speculated that resistance to topoisomerase II-targeted anticancer agents results from a decreased drug-enzyme binding affinity, these data provide the first direct evidence in support of this hypothesis. Finally, the ability of yeast topoisomerase II to bind etoposide was dependent on the presence of the hydroxyl moiety of Tyr783, suggesting specific interactions between etoposide and the active site residue that is involved in DNA scission.

The response of eukaryotic topoisomerases to DNA damage

Beyond the known mutagenic properties of DNA lesions, recent evidence indicates that several forms of genomic damage dramatically influence the catalytic activities of DNA topoisomerases. Apurinic sites, apyrimidinic sites, base mismatches, and ultraviolet photoproducts all enhance topoisomerase I-mediated DNA cleavage when they are located in close proximity to the point of scission. Furthermore, when located between the points of scission of a topoisomerase II cleavage site, these same lesions (with the exception of ultraviolet photoproducts) greatly stimulate the cleavage activity of the type II enzyme. Thus, as found for anticancer drugs, lesions have the capacity to convert topoisomerases from essential cellular enzymes to potent DNA toxins. These findings raise exciting new questions regarding the mechanism of anticancer drugs, the physiological functions of topoisomerases, and the processing of DNA damage in the cell.

Topoisomerase II-mediated DNA cleavage and religation in the absence of base pairing. Abasic lesions as a tool to dissect enzyme mechanism

The interaction of topoisomerase II with its DNA cleavage site is critical to the physiological functions of the enzyme. Despite this importance, the specific enzyme-DNA interactions that drive topoisomerase II-mediated DNA cleavage and religation are poorly understood. Therefore, to dissect interactions between the enzyme and its cleavage site, abasic DNA lesions were incorporated into a bilaterally symmetrical and identical cleavage site. Results indicate that topoisomerase II has unique interactions with each position of the 4-base overhang generated by enzyme-mediated DNA cleavage. Lesions located 2 bases 3' to the point of scission stimulated cleavage the most, whereas those 3 bases from the point of scission stimulated cleavage the least. Moreover, an additive and in some cases synergistic cleavage enhancement was observed in oligonucleotides that contained multiple DNA lesions, with levels reaching >60-fold higher than the wild-type substrate. Finally, topoisomerase II efficiently cleaved and religated a DNA substrate in which apyrimidinic sites were simultaneously incorporated at every position on one strand of the 4-base overhang. Therefore, unlike classical DNA ligases in which base pairing is the driving force behind closure of the DNA break, it appears that for topoisomerase II, the enzyme is responsible for the spatial orientation of the DNA termini for ligation.

Spontaneous DNA lesions poison human topoisomerase IIalpha and stimulate cleavage proximal to leukemic 11q23 chromosomal breakpoints

Topoisomerase II-targeted drugs, such as etoposide, "poison" this enzyme and kill cells by increasing levels of covalent topoisomerase II-cleaved DNA complexes. In spite of the success of this drug in the treatment of human cancers, a significant proportion of patients treated with etoposide eventually develop secondary leukemias that are characterized by translocations at chromosome band 11q23. Since similar translocations are associated with primary leukemias in previously untreated infants, we questioned whether they could also be triggered by the actions of "endogenous topoisomerase II poisons". Recent studies, which demonstrated that several forms of spontaneous DNA damage stimulate cleavage mediated by Drosophila topoisomerase II, suggest that DNA lesions may act as these endogenous poisons. Therefore, to determine whether the ability to recognize spontaneous DNA damage has been conserved from this lower eukaryote to mammalian species, the effects of apurinic sites, apyrimidinic sites, and deaminated cytosine residues on human topoisomerase IIalpha were assessed. All three lesions were potent poisons of the human enzyme and stimulated cleavage when located within the four-base overhang generated by enzyme-mediated DNA scission. Furthermore, these lesions increased levels of cleavage at five sites proximal to 11q23 translocation breakpoints and did so with an efficacy that was comparable to or greater than that of therapeutic concentrations of etoposide. Although the physiological relevance of these findings has yet to be established, they suggest a potential role for endogenous topoisomerase II poisons in the initiation of leukemic chromosomal breakpoints.