Delta-like 4 is required for pulmonary vascular arborization and alveolarization in the developing lung.

The molecular mechanisms by which endothelial cells (ECs) regulate pulmonary vascularization and contribute to alveolar epithelial cell development during lung morphogenesis remain unknown. We tested the hypothesis that delta-like 4 (DLL4), an EC Notch ligand, is critical for alveolarization by combining lung mapping and functional studies in human tissue and DLL4-haploinsufficient mice (Dll4+/lacz). DLL4 expressed in a PECAM-restricted manner in capillaries, arteries, and the alveolar septum from the canalicular to alveolar stage in mice and humans. Dll4 haploinsufficiency resulted in exuberant, nondirectional vascular patterning at E17.5 and P6, followed by smaller capillaries and fewer intermediate blood vessels at P14. Vascular defects coincided with polarization of lung EC expression toward JAG1-NICD-HES1 signature and decreased tip cell-like (Car4) markers. Dll4+/lacZ mice had impaired terminal bronchiole development at the canalicular stage and impaired alveolarization upon lung maturity. We discovered that alveolar type I cell (Aqp5) markers progressively decreased in Dll4+/lacZ mice after birth. Moreover, in human lung EC, DLL4 deficiency programmed a hypersprouting angiogenic phenotype cell autonomously. In conclusion, DLL4 is expressed from the canalicular to alveolar stage in mice and humans, and Dll4 haploinsufficiency programs dysmorphic microvascularization, impairing alveolarization. Our study reveals an obligate role for DLL4-regulated angiogenesis in distal lung morphogenesis.

Clinical Outcomes among Diagnostic Subgroups of Infants with Severe Bronchopulmonary Dysplasia through 2 Years of Age.

OBJECTIVE: This article aimed to identify readmission risk factors through 2 years of life for infants with severe bronchopulmonary dysplasia (BPD) who do not require tracheostomy and ventilatory support after neonatal intensive care unit (NICU) discharge. It also aimed to identify if clinical differences exist between the subcategories of severe BPD. STUDY DESIGN: A retrospective chart review was performed on 182 infants with severe BPD born between 2010 and 2015. A total of 130 infants met the inclusion criteria and were stratified into three groups based on their respiratory status at 36 weeks of gestational age: group A-oxygen (O2), group B-assisted ventilation (AV), group C-both O2 and AV. NICU clinical risk factors for readmission were assessed at set time points (6/12/18/24 months). Reasons for readmission were assessed for the entire cohort and severe BPD subgroups. CONCLUSION: An NICU diagnosis of neurologic abnormality, necrotizing enterocolitis, invasive NICU infection, dysphagia, and O2 at NICU discharge differed between the three subgroups of severe BPD. The most common cause of readmission was viral respiratory tract infection. Inhaled steroid use remained stable over time, while oxygen use and diuretic use declined over time. Risk factors for readmission in the entire cohort included g-tube, O2 use, and diuretic use at 12 months. There was no significant difference in readmission rates between the three BPD subgroups.

Acute Post-Tracheostomy Clinical Decompensations in Infants-Are There Predictive Markers?

OBJECTIVE: To report on the population of infants receiving a tracheostomy, identify acute post-tracheostomy clinical decompensations, and seek predictive markers associated with acute complications following the placement of a tracheostomy. STUDY DESIGN: Retrospective deidentified clinical data was provided by the Infant Pulmonary Data Repository at Children's Mercy Hospital, Kansas City. Data from infants undergoing tracheostomy from January 1, 2008 through September 30, 2016 were divided into one of two study groups based on clinical correlations: (1) no acute decompensations within 72 hours post-tracheostomy or (2) acute clinical decompensation defined as sustained escalation of respiratory care within the 72 hours following tracheostomy. RESULTS: Thirty-four percent of infants undergoing tracheostomy during this period developed acute post-tracheostomy clinical decompensations. Elevated pre-tracheostomy positive end expiratory pressure, mean airway pressure, and echocardiogram findings suggestive of pulmonary hypertension (PH) or ventricular dysfunction were associated with acute post-tracheostomy clinical decompensations. Additionally acute post-tracheostomy clinical decompensation was associated with higher rate of death prior to discharge. CONCLUSION: Infants requiring higher respiratory support and infants with PH or ventricular dysfunction are at risk of acute post-tracheostomy clinical decompensation, thus identifying these patients may lead to better pre-tracheostomy counseling and potentially targeted treatments to decrease this risk.

Lung epithelial-specific TRIP-1 overexpression maintains epithelial integrity during hyperoxia exposure.

The onset and degree of injury occurring in animals that develop hyperoxic acute lung injury (HALI) is dependent on age at exposure, suggesting that developmentally regulated pathways/factors must underlie initiation of the epithelial injury and subsequent repair. Type II TGFß receptor interacting protein-1 (TRIP-1) is a negative regulator of TGFß signaling, which we have previously shown is a developmentally regulated protein with modulatory effects on epithelial-fibroblastic signaling. The aim of this study was to assess if type II alveolar epithelial cells overexpressing TRIP-1 are protected against hyperoxia-induced epithelial injury, and in turn HALI. Rat lung epithelial cells (RLE) overexpressing TRIP-1 or LacZ were exposed to 85% oxygen for 4 days. A surfactant protein C (SPC)-driven TRIP-1 overexpression mouse (TRIP-1AECTg+ ) was generated and exposed to hyperoxia (>95% for 4 days) at 4 weeks of age to assess the effects TRIP-1 overexpression has on HALI. RLE overexpressing TRIP-1 resisted hyperoxia-induced apoptosis. Mice overexpressing TRIP-1 in their lung type II alveolar epithelial cells (TRIP-1AECTg+ ) showed normal lung development, increased phospho-AKT level and E-cadherin, along with resistance to HALI, as evidence by less TGFß activation, apoptosis, alveolar macrophage influx, KC expression. Taken together, these findings point to existence of a TRIP-1 mediated molecular pathway affording protection against epithelial/acute lung injury.

Nicotinamide Adenine Dinucleotide Phosphate Oxidase 2 Regulates LPS-Induced Inflammation and Alveolar Remodeling in the Developing Lung.

In premature infants, sepsis is associated with alveolar simplification manifesting as bronchopulmonary dysplasia. The redox-dependent mechanisms underlying sepsis-induced inflammation and alveolar remodeling in the immature lung remain unclear. We developed a neonatal mouse model of sepsis-induced lung injury to investigate whether nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) regulates Toll-like receptor (TLR)-mediated inflammation and alveolar remodeling. Six-day-old NOX2+/+ and NOX2-/- mice were injected with intraperitoneal LPS to induce sepsis. Lung inflammation and canonical TLR signaling were assessed 24 hours after LPS. Alveolar development was examined in 15-day-old mice after LPS on Day 6. The in vivo efficacy of a NOX2 inhibitor (NOX2-I) on NOX2 complex assembly and sepsis-induced lung inflammation were examined. Lung cytokine expression and neutrophil influx induced with sepsis in NOX2+/+ mice was decreased by >50% in NOX2-/- mice. LPS-induced TLR4 signaling evident by inhibitor of NF-κB kinase-ß and mitogen-activated protein kinase phosphorylation, and nuclear factor-κB/AP-1 translocation were attenuated in NOX2-/- mice. LPS increased matrix metalloproteinase 9 while decreasing elastin and keratinocyte growth factor levels in NOX2+/+ mice. An LPS-induced increase in matrix metalloproteinase 9 and decrease in fibroblast growth factor 7 and elastin were not evident in NOX2-/- mice. An LPS-induced reduction in radial alveolar counts and increased mean linear intercepts were attenuated in NOX2-/- mice. LPS-induced NOX2 assembly evident by p67phox/gp91phox coimmunoprecipitation was disrupted with NOX2-I. NOX2-I also mitigated LPS-induced cytokine expression, TLR pathway signaling, and alveolar simplification. In a mouse model of neonatal sepsis, NOX2 regulates proinflammatory TLR signaling and alveolar remodeling induced by a single dose of LPS. Our results provide mechanistic insight into the regulation of sepsis-induced alveolar remodeling in the developing lung.

Rehospitalization in Infants Born < 29 Weeks' Gestation during the First 2 Years of Life: Risk Assessment.

OBJECTIVE: This study aims to determine risk factors for rehospitalization in extremely premature infants. STUDY DESIGN: A retrospective cohort study of 157 infants born < 29 weeks' gestational age assessing risk factors for rehospitalization through 2 years of life. RESULTS: Multivariable logistic regression showed that an increasing number of respiratory infections (odds ratio [OR]: 1.8 [1.1-3.1] per infection p = 0.03) and inhaled steroid use at 1 year (OR: 4.0 [1.3-12.1] p = 0.01) were predictive of hospital readmission. Diuretic (OR: 27 [1.01-1,000] p = 0.04) and oxygen (OR: 32 [3.1-333] p = 0.004) use at 1 year were predictive of pediatric intensive care unit admission. The number of respiratory infections (OR: 2.8 [1.7-4.5] p < 0.0001) with reflux/aspiration necessitating G-tube/Nissen fundoplication surgical intervention with or without G-tubes alone (OR: 21.3 [2.9-166.7] p = 0.02 and OR: 22.7 [CI, 2.4-200] p = 0.04) was predictive of increased number of rehospitalizations. CONCLUSIONS: Key modifiable risk factors identified were reflux/aspiration and ongoing respiratory infections. Critical time periods for diuretic, oxygen, and inhaled steroid use in this population occurred at the age of 1 year.

Impaired growth at birth and bronchopulmonary dysplasia classification: beyond small for gestational age.

OBJECTIVE: To correlate intrauterine and postnatal growth with bronchopulmonary dysplasia (BPD) classification at 36 weeks postmenstrual age (PMA). STUDY DESIGN: A retrospective cohort design reviewing medical records for infants < 29 weeks gestational age (GA) born between 2008 and 2010. BPD classification using physiological definition at 36 weeks PMA and growth parameters at birth and 36 weeks PMA were compared between GA subgroups. RESULTS: The cohort consisted of 140 infants. Median GA and birth weight (BW) were 27 weeks and 918 g, respectively. Twenty percent of infants had no BPD, 27% had mild BPD, 31% had moderate BPD, and 22% had severe BPD. While BW and GA remain major factors associated with severe BPD, we did not observe differences in weights at 36 weeks PMA. Length and head circumference were significantly impaired in infants born < 26 weeks GA at birth and 36 weeks PMA. Most importantly, all infants born < 26 weeks GA below the 25th percentile for weight developed moderate/severe BPD. CONCLUSION: Infants born < 26 weeks GA were smaller at birth and had significant postnatal growth impairment in linear and head circumference growth. Risk of developing BPD associated with lower BW for GA appeared to occur beyond the traditional small-for-gestational age (SGA) classification.

TRIP-1 via AKT modulation drives lung fibroblast/myofibroblast trans-differentiation.

BACKGROUND: Myofibroblasts are the critical effector cells in the pathogenesis of pulmonary fibrosis which carries a high degree of morbidity and mortality. We have previously identified Type II TGFß receptor interacting protein 1 (TRIP-1), through proteomic analysis, as a key regulator of collagen contraction in primary human lung fibroblasts--a functional characteristic of myofibroblasts, and the last, but critical step in the process of fibrosis. However, whether or not TRIP-1 modulates fibroblast trans-differentiation to myofibroblasts is not known. METHODS: TRIP-1 expression was altered in primary human lung fibroblasts by siRNA and plasmid transfection. Transfected fibroblasts were then analyzed for myofibroblast features and function such as α-SMA expression, collagen contraction ability, and resistance to apoptosis. RESULTS: The down-regulation of TRIP-1 expression in primary human lung fibroblasts induces α-SMA expression and enhances resistance to apoptosis and collagen contraction ability. In contrast, TRIP-1 over-expression inhibits α-SMA expression. Remarkably, the effects of the loss of TRIP-1 are not abrogated by blockage of TGFß ligand activation of the Smad3 pathway or by Smad3 knockdown. Rather, a TRIP-1 mediated enhancement of AKT phosphorylation is the implicated pathway. In TRIP-1 knockdown fibroblasts, AKT inhibition prevents α-SMA induction, and transfection with a constitutively active AKT construct drives collagen contraction and decreases apoptosis. CONCLUSIONS: TRIP-1 regulates fibroblast acquisition of phenotype and function associated with myofibroblasts. The importance of this finding is it suggests TRIP-1 expression could be a potential target in therapeutic strategy aimed against pathological fibrosis.

An unusual case of rapidly progressive hyperbilirubinemia.

We present an unusual case of hyperbilirubinemia with rapid early progression leading to bilirubin encephalopathy in a term neonate. Despite early recognition and intervention, the total serum bilirubin reached a maximum level of 39 mg/dL at 32 hours of life. Prior to an emergent exchange transfusion, the patient's diagnostic evaluation was significant for Coombs-negative microangiopathic hemolytic anemia and thrombocytopenia. Further testing revealed a deficiency of ADAMTS13 protein, or von Willebrand factor-cleaving protease, a finding diagnostic of congenital thrombotic thrombocytopenic purpura, or Upshaw-Schulman syndrome. This rare disease is often misdiagnosed, especially in the newborn period.