Comparison of tissue factor pathway in human umbilical vein and adult saphenous vein endothelial cells: implications for newborn hemostasis and for laboratory models of endothelial cell function

Functionally distinct anticoagulant mechanisms of endothelial cells

Antithrombin and tissue factor pathway inhibitor (TFPI) provide different anticoagulant mechanisms. Having established a potent anticoagulant role of cultured human umbilical vein endothelial cells in vessel-on-a-chip microfluidic models, we now investigated how these cells modulated thrombin generation under stasis through antithrombin and TFPI pathways. We observed that endothelial monolayers in 96 well-plates strongly delayed and suppressed the thrombin generation process induced by tissue factor, regardless of the presence of whole blood, platelet-rich plasma or platelet-free plasma. Intervention studies indicated that the blocking of heparin-like proteoglycans with polybrene or protamine sulphate, similarly as the absence of antithrombin in plasma, reverted the endothelial anticoagulant activity. Heparinase treatment of the cells also reduced the anticoagulant potential. Furthermore, the presence of andexanet-alpha (inactivated factor Xa) and an anti-TFPI antibody were able to revert the endothelial effects. Jointly, these data point to additive anticoagulant mechanisms of endothelial cells through surface-expressed heparin-like proteoglycans and TFPI, both contributing to thrombin inhibition.

Comparison of standard and global hemostasis assays in cord and peripheral blood of newborns

BACKGROUND

Umbilical cord blood is used for the testing of various parameters in newborns. However, data on its applicability for hemostasis assays is insufficient.

OBJECTIVE

To evaluate whether umbilical cord blood can be used for standard tests, thromboelastometry and thrombodynamics for preterm and term newborns.

METHODS

187 newborns were included in the study. Blood was taken from the umbilical cord and by venipuncture of the newborn. Clotting times, fibrinogen, D-dimer, thromboelastometry and thrombodynamics were measured.

RESULTS

Clotting times and fibrinogen indicated a hypocoagulable shift, while thromboelastometry and thrombodynamics showed a hypercoagulable shift in hemostasis in umbilical cord blood compared to newborn blood. D-dimer indicated an enhanced process of thrombus lysis in newborn blood compared to cord blood. Collecting blood into a tube with the addition of a contact pathway inhibitor did not significantly change the global assay parameters in either umbilical cord blood or newborn blood. In the thrombodynamics assay, spontaneous clotting was detected but suppressed by the addition of a tissue factor inhibitor.

CONCLUSIONS

Hemostasis in cord and newborn blood differs for both global and standard tests. Hypercoagulability in newborns registered with the global assay thrombodynamics is associated with the presence of tissue factor in the blood.

IMPACT STATEMENT

1. We found a hypercoagulation shift in newborns compared with the adult references, possibly due to the presence of tissue factor in blood. 2. Blood coagulation is enhanced in cord blood compared with blood sampled from the vein of a newborn according to thromboelastometry and thrombodynamics assays. 3. Clotting times and fibrinogen concentrations in cord blood differ from these parameters in newborn blood. 4. Studying of the (patho)physiological features of hemostasis in newborns should consider differences in cord blood and vein sampled blood.

Differential procoagulatory response of microvascular, arterial and venous endothelial cells upon inflammation in vitro

INTRODUCTION

Inflammation induces a procoagulant phenotype of endothelial cells (EC) with the exposure of tissue factor (TF), a potent initiator of the extrinsic coagulation cascade. Although systemic inflammation affects the whole vascular system, thrombotic lesions occur particularly in microcirculation. This raises the question of whether TF-procoagulant activity (TF-PCA) differs between EC from arterial, venous, and microvascular beds.

MATERIALS AND METHODS

Functional coagulation tests, including TF-PCA, and inflammatory responses were investigated on arterial, venous and microvascular endothelial cells. Interleukin-6 (IL-6) and TF-levels were determined in cohort of 59 septic patients.

RESULTS

We found that tumor necrosis factor alpha (TNFα), lipopolysaccharide, and interleukin-1β induce a solid, dose-dependent increase in TF-PCA, which is highest in microvascular EC. A positive correlation of interleukin-6 (IL-6) with TF levels was observed in a cohort of 59 septic patients. In contrast, TF-PCA was independent of IL-6 concentrations in vitro. Re-analysis of publicly available gene expression data revealed that among the top 50 genes annotated to coagulation, TF is one of three regulated genes common to the three investigated EC subtypes. The response to inflammatory stimuli in terms of exposure of leukocyte-endothelial- and platelet-endothelial adhesion molecules (E-selectin and PECAM-1), remodeling of adherens junctions, co-exposure of negatively charged surfaces nor breakdown of the glycocalyx was comparable between the EC subtypes and did not explain the higher TF-PCA on microvascular cells. We found that the ratio of TF and TFPI exposure on the endothelial membrane significantly differs between the EC subtypes.

CONCLUSIONS

These findings indicate that the ratio of TF to its inhibitor TFPI is a determinant of endothelial TF-PCA, which is most pronounced on microvascular endothelial cells and might explain why the microvascular system is particularly susceptible to inflammation-induced thrombosis.

Current understanding and perioperative management of pediatric pulmonary hypertension

Pediatric pulmonary hypertension is a complex disease with multiple, diverse etiologies affecting the premature neonate to the young adult. Pediatric pulmonary arterial hypertension, whether idiopathic or associated with congenital heart disease, is the most commonly discussed form of pediatric pulmonary hypertension, as it is progressive and lethal. However, neonatal forms of pulmonary hypertension are vastly more frequent, and while most cases are transient, the risk of morbidity and mortality in this group deserves recognition. Pulmonary hypertension due to left heart disease is another subset increasingly recognized as an important cause of pediatric pulmonary hypertension. One aspect of pediatric pulmonary hypertension is very clear: anesthetizing the child with pulmonary hypertension is associated with a significantly heightened risk of morbidity and mortality. It is therefore imperative that anesthesiologists who care for children with pulmonary hypertension have a firm understanding of the pathophysiology of the various forms of pediatric pulmonary hypertension, the impact of anesthesia and sedation in the setting of pulmonary hypertension, and anesthesiologists' role as perioperative experts from preoperative planning to postoperative disposition. This review summarizes the current understanding of pediatric pulmonary hypertension physiology, preoperative risk stratification, anesthetic risk, and intraoperative considerations relevant to the underlying pathophysiology of various forms of pediatric pulmonary hypertension.

Ten-year-old children with a history of bronchopulmonary dysplasia have regional abnormalities in ventilation perfusion matching

AIM

The ratio of ventilation to blood flow is an important determinant for regional gas exchange in the lung and hypoxemia is one of the clinical hallmarks in infants with bronchopulmonary dysplasia (BPD). We have previously demonstrated ventilation/perfusion ratio (V/Q) abnormalities in infants with BPD at 36 weekś postconceptional age. The status of V/Q matching in older children with a history of BPD in infancy is unknown. In this study, we examined if 10-year-old children with a history of BPD had V/Q impairments.

METHODS

Three-dimensional V/Q-scintigraphy (SPECT) was performed in 26 children.

RESULTS

In the BPD group, lung volume with mismatch, (V>Q) was larger compared to areas with reverse mismatch (Q>V), 26.2% and 11.8%, respectively, implying that perfusion defects contribute more than ventilation defects in the V/Q mismatch. Also, the mean fractional distribution of V and Q to V/Q in children with BPD was reduced compared to healthy children, 31% and 51% compared to 64% and 89%, respectively (P < 0.01).

CONCLUSION

At 10 years of age children with a history of BPD had ventilation/perfusion abnormalities, with prominent perfusion defects. These V/Q abnormalities suggest the presence of residual alveolar-capillary impairment.

An Echocardiographic Screening Program Helps to Identify Pulmonary Hypertension in Extremely Low Birthweight Infants with and without Bronchopulmonary Dysplasia: A Single-Center Experience

BACKGROUND

Pulmonary hypertension (PH) affects 1 in 6 infants with a birthweight <1,000 g (extremely low birthweight; ELBW) and is frequently associated with bronchopulmonary dysplasia (BPD). If untreated, the mortality rates of the disease are high.

OBJECTIVES

The aim of this study was to characterize risk factors for PH in ELBW infants and to describe the timing of onset of the disease by setting up a screening program.

METHODS

ELBW infants treated at the Department of Neonatology (level III neonatal intensive care unit at the University of Cologne Medical Centre, Germany) between January 2010 and March 2015 were included. Echocardiography screening for PH was performed either before discharge or if BPD was diagnosed. Additionally, infants had at least 1 echocardiographic scan after discharge. Survival with PH, age at diagnosis of PH, and risk factors associated with PH were assessed.

RESULTS

In total, 34/188 (18%) infants had PH. Of these, 14 (41%) were identified after discharge. Another 11 (32%) were diagnosed with PH without suffering from moderate or severe BPD. The risk factors for diagnosis of PH were moderate (odds ratio, OR 4 [2-8]) or severe BPD (OR 13 [2-71]), prolonged rupture of membranes >7 days (OR 5 [1-19]), and birthweight below the 3rd percentile (OR 3 [1-9]). All infants with PH before discharge and 50% diagnosed after discharge were treated with sildenafil (2.0 mg/kg/day). PH resolved and sildenafil was discontinued in all patients after a median duration of 13 months (IQR 8-20).

CONCLUSIONS

An echocardiographic screening program may help to identify infants with PH. Examinations should include all ELBW infants irrespective of the presence of BPD and be continued after discharge.

Structural Pulmonary Abnormalities Still Evident in Schoolchildren with New Bronchopulmonary Dysplasia

BACKGROUND

A new pattern of bronchopulmonary dysplasia (BPD) has emerged with the improved survival of preterm children.

OBJECTIVES

Our aim was to characterize structural abnormalities associated with new BPD and to evaluate whether the severity of high-resolution computed tomography (HRCT) changes is associated with lung function.

METHODS

HRCT scans were performed on 21 schoolchildren with a history of new BPD (mild, n = 9; moderate, n = 4; and severe, n = 8) with a mean age of 12.7 years (range: 8.7-16.7). Scans were interpreted by 2 radiologists using a structured scoring system. Spirometry (forced expiratory volume in 1 s [FEV1] and maximum mid-expiratory flow [MMEF]) and the diffusion capacity of the lung for carbon monoxide (DLCO) were measured.

RESULTS

At least 1 HRCT abnormality was evident in 17 children (81%), including linear-to-triangular subpleural opacities (71%), air trapping (29%), mosaic perfusion (24%), peribronchial thickening (14%), and emphysema (14%). The HRCT score was higher in the severe BPD group (11.50; 95% CI 2.86-20.14) than in the mild or moderate BPD group (1.39; 95% CI 0.24-2.54, and 2.75; 95% CI 0.28-5.22, respectively). HRCT scores were inversely related to FEV1 (β -4.23; 95% CI -6.97 to -1.49, p = 0.004) and MMEF (β -3.45; 95% CI -6.10 to -0.80, p = 0.013) but not to DLCO. The duration of the initial mechanical ventilation was associated with HRCT scores (p = 0.014).

CONCLUSIONS

Structural lung abnormalities are common among schoolchildren with a history of new BPD, resembling abnormalities described in the presurfactant era. HRCT abnormalities are associated with the duration of early mechanical ventilation and the severity of BPD and they are correlated with spirometry.

Inhibition of Rac1 Signaling Downregulates Inflammasome Activation and Attenuates Lung Injury in Neonatal Rats Exposed to Hyperoxia

BACKGROUND

Inflammatory injury, particularly the production of active interleukin (IL)-1β plays a major role in the pathogenesis of bronchopulmonary dysplasia (BPD) in preterm infants. The release of active IL-1β is controlled by posttranscriptional modifications of its proform (pro-IL-1β) through the inflammasome. Rac1 is a member of the Rho family of GTPases that regulate the inflammatory process.

OBJECTIVE

This study tested the hypothesis that Rac1 signaling increases inflammasome activation that results in damaging inflammation, and that the inhibition of Rac1 signaling prevents lung injury, by inhibiting inflammasome activation in a newborn rat model of BPD induced by hyperoxia.

METHODS

Newborn rat pups were exposed to room air or hyperoxia (85% O2) and received daily intraperitoneal injections of placebo (normal saline) or NSC23766, a specific Rac1 inhibitor, for 10 days. The effects on lung inflammation, alveolarization, vascular development, vascular remodeling, right ventricular systolic pressure, and right ventricular hypertrophy (RVH) were then assessed.

RESULTS

Hyperoxia exposure upregulated Rac1 and increased the production of active IL-1β, which was accompanied by increasing expression of the inflammasome. In addition, hyperoxia induced the pathological hallmarks of BPD. However, treatment with NSC23766 significantly decreased inflammasome activation and macrophage infiltration, improved alveolar and vascular development, and reduced pulmonary vascular remodeling and RVH.

CONCLUSION

These results indicate that Rac1 signaling regulates the expression of the inflammasome and plays a pivotal role in the pathogenesis of hyperoxia-induced neonatal lung injury. Therefore, targeting Rac1 signaling may provide a novel strategy to prevent and treat BPD in preterm infants.

Impaired pulmonary vascular development in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), the chronic lung disease associated with preterm birth, results from the disruption of normal pulmonary vascular and alveolar growth. Though BPD was once described as primarily due to postnatal injury from mechanical ventilation and oxygen therapy after preterm birth, it is increasingly appreciated that BPD results from antenatal and perinatal factors that interrupt lung development in infants born at the extremes of prematurity. The lung in BPD consists of a simplified parenchymal architecture that limits gas exchange and leads to increased cardiopulmonary morbidity and mortality. This review outlines recent advances in the understanding of pulmonary vascular development and describes how the disruption of these mechanisms results in BPD. We point to future therapies that may augment postnatal vascular growth to prevent and treat this severe chronic lung disease.

The lung alveolar lipofibroblast: an evolutionary strategy against neonatal hyperoxic lung injury

SIGNIFICANCE

Oxygen, the main mode of support for premature infants with immature lungs, can cause toxicity by producing reactive oxygen species (ROS) that disrupt homeostasis; yet, these same molecules were entrained to promote vertebrate lung phylogeny. By providing a deeper understanding of this paradox, we propose physiologically rational strategies to prevent chronic lung disease (CLD) of prematurity.

RECENT ADVANCES

To prevent neonatal hyperoxic lung damage biologically, we have exploited the alveolar defense mechanism(s) that evolutionarily evolved to combat increased atmospheric oxygen during the vertebrate water to land transition.

CRITICAL ISSUES

Over the course of vertebrate lung evolution, ROS promoted the formation of lipofibroblasts, specialized adepithelial cells, which protect the alveoli against oxidant injury; peroxisome proliferator-activated receptor gamma (PPARγ), the master switch for lipofibroblast differentiation, prevents such oxidant lung injury, both by directly promoting mesodermal differentiation and its antioxidant defenses, and indirectly by stimulating the developmental epithelial-mesenchymal paracrine interactions that have physiologically determined lung surfactant production in accord with the lung's phylogenetic adaptation to atmospheric oxygen, preventing Respiratory Distress Syndrome at birth.

FUTURE DIRECTIONS

The molecular strategy (PPARγ agonists) to prevent CLD of prematurity, proposed by us, although seems to be robust, effective, and safe under experimental conditions, it awaits detailed pharmacokinetic and pharmacodynamic studies for its safe and effective clinical translation to human infants. Antioxid. Redox Signal. 21, 1893-1904. "I have procured air [oxygen]…between five and six times as good as the best common air that I have ever met with." -Joseph Priestley, 1775.

Heme oxygenase in neonatal lung injury and repair

SIGNIFICANCE

Premature and sick neonates are often exposed to high concentrations of oxygen, which results in lung injury and long-term adverse consequences. Nevertheless, neonates are more tolerant to hyperoxia than are adults. This may be, in part, explained by the high lung content of heme oxygenase-1 (HO-1), the rate-limiting enzyme in the degradation of heme and an important stress protein. The abundance of HO-1 dictates its cytoprotective and deleterious effects. Interestingly, in response to hyperoxia, lung HO-1 mRNA is not further up-regulated in neonates, suggesting that lung HO-1 gene expression is tightly regulated so as to optimize cytoprotection when faced with an oxidative stress such as hyperoxia.

RECENT ADVANCES

In addition to the lack of induction of HO-1 mRNA, neonatal lung HO-1 protein is observed in the nucleus in neonatal mice exposed to hyperoxia but not in adults, which is further evidence for the developmental regulation of HO-1. Nuclear HO-1 had unique properties independent of its enzymatic activity. In addition, there has been increasing evidence that nuclear HO-1 contributes to cellular proliferation and malignant transformation in several human cancers.

CRITICAL ISSUES

Since HO-1 has dual effects in cytoprotection and cellular proliferation, the titration of HO-1 effects is critical to ensure beneficial actions against oxidative stress.

FUTURE DIRECTIONS

Much more has to be understood about the specific roles of HO-1 so as to manipulate its abundance and/or nuclear migration to maximize the therapeutic benefit of this pleiotropic protein in the neonatal lung.

Pulmonary Hypertension in Preterm Infants with Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is a significant contributor to perinatal morbidity and mortality. Premature birth disrupts pulmonary vascular growth and initiates a cascade of events that result in impaired gas exchange, abnormal vasoreactivity, and pulmonary vascular remodeling that may ultimately lead to pulmonary hypertension (PH). Even infants who appear to have mild BPD suffer from varying degrees of pulmonary vascular disease (PVD). Although recent studies have enhanced our understanding of the pathobiology of PVD and PH in BPD, much remains unknown with respect to how PH should be properly defined, as well as the most accurate methods for the diagnosis and treatment of PH in infants with BPD. This article will provide neonatologists and primary care providers, as well as pediatric cardiologists and pulmonologists, with a review of the pathophysiology of PH in preterm infants with BPD and a summary of current clinical recommendations for managing PH in this population.

Tissue factor inflammatory response regulated by promoter genotype and p38 MAPK in neonatal vs. adult microvascular endothelial cells

OBJECTIVE AND DESIGN

Variable tissue factor (TF) expression by human microvascular endothelial cells (HMVEC) may be regulated by two promoter haplotypes, distinguished by an 18-basepair deletion (D) or insertion (I) at -1,208. We sought to determine the relationship between these haplotypes and interleukin-1α (IL-1α)-induced TF expression in neonatal versus adult HMVEC.

RESULTS

IL-1-stimulated TF mRNA, protein, and activity were significantly higher in neonatal compared to adult D/D donors. IL-1-stimulated HMVEC from neonatal D/D donors expressed threefold higher levels of TF mRNA, twofold higher TF protein, and fourfold increased TF activity compared to HMVEC from adult D/D donors. These results indicate that homozygosity for the D haplotype is characterized by increased response to IL-1 in neonates, but not adults. IL-1 induced increased phosphorylation of p38 mitogen-activated protein kinase (MAPK), which was significantly greater in neonatal compared to adult HMVEC. Moreover, inhibition of the p38 MAPK pathway reduced IL-1-stimulated TF mRNA expression in D/D neonatal but not adult HMVEC.

CONCLUSIONS

Upregulation of D/D neonatal HMVEC TF expression by IL-1 is mediated through the p38 MAPK pathway. This heightened response of D/D neonatal HMVEC to inflammatory stimuli may contribute to increased microvascular coagulopathies in susceptible newborn infants.

Shiga toxin downregulates tissue factor pathway inhibitor, modulating an increase in the expression of functional tissue factor on endothelium

INTRODUCTION

Endothelial expression of tissue factor (TF) may play a major role in (Stx)-related hemolytic uremic syndrome. We examined human umbilical vein endothelial cell (HUVEC) monolayers to determine the interaction between TF and TF pathway inhibitor (TFPI), hypothesizing that changes in TFPI modulate TF expression.

MATERIALS AND METHODS

We studied 1) cell surface expression of globotriasylceramide (Gb3, the receptor for Stx) with Stx-1 (10 pM), TNFα (20 Ng/ml), or Stx-1 plus TNFα compared to control, 2) gene expression of TF and TFPI, 3) total cellular and cell surface antigenic TF and TFPI, 4) TFPI secretion into supernatant, and 5) factor Xa production.

RESULTS AND CONCLUSIONS

Gb3 expression, negligible with control and Stx-1 alone, increased significantly with TNFα and with Stx-1 plus TNFα. TF mRNA increased 1.25 ± 0.32- fold (N = 9; p = 0.041) with Stx-1 alone vs. 2.82 ± 0.92-fold (N = 13; p < 0.0005) with TNFα alone. However, Stx-1 plus TNFα yielded a 6.51 ± 3.48-fold increase (N = 17; p < 0.0005). TFPI mRNA decreased with TNFα (p < 0.001) and Stx-1 plus TNFα (p < 0.0005). Total cellular and cell surface TF antigen increased significantly with TNFα, but no further with Stx-1 plus TNFα. Total TFPI cellular and cell surface antigen levels, and TFPI secretion decreased significantly with Stx-1 plus TNFα. Median factor Xa production for Stx-1 plus TNFα vs TNFα alone increased (p < 0.001) 3.24-fold. Our results indicate that a subinhibitory concentration of Stx-1 plus TNFα impairs TFPI gene expression, synthesis, cell-surface association, and secretion, leading to augmented functional TF.

The journey towards lung protective respiratory support in preterm neonates

The aim of this conceptual review is to provide the reader with a broad perspective on progress made in respiratory support of preterm infants over the past five decades. Landmark discoveries are described in their historical context and underlying theories of lung protection are discussed. The review finishes by integrating different approaches and perspectives into a state-of-the-art concept for lung-protective ventilation in this fragile patient population. Improvements in neonatal respiratory support in the 1970s and 1980s have contributed to dramatic improvements of mortality and morbidity rates among neonates with respiratory failure. Continuous positive airway pressure, antenatal corticosteroids and surfactant replacement therapy revolutionized the care of preterm infants. With the recognition that atelectrauma, volutrauma and oxygen toxicity are the main factors contributing to ventilator-induced lung injury, lung-protective strategies, including noninvasive respiratory support, tidal volume targeting during conventional mechanical ventilation and high frequency ventilation were developed in the 1990s. Given the fact that progress made in the last decade has only resulted in minor improvements in mortality and morbidity rates of neonates with respiratory failure, it seems unlikely that further refinements of current technologies will produce giant leaps forward in high-resource countries. It appears that entirely new approaches would be required. In contrast, knowledge and technology transfer of basic respiratory support strategies (e.g. use of oxygen, simple systems to provide continuous positive airway pressure), could have an enormous impact on the prognosis of neonates with respiratory failure in low-resource countries.

Aberrant signaling pathways of the lung mesenchyme and their contributions to the pathogenesis of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease in infants born extremely preterm, typically before 28 weeks' gestation, characterized by a prolonged need for supplemental oxygen or positive pressure ventilation beyond 36 weeks postmenstrual age. The limited number of autopsy samples available from infants with BPD in the postsurfactant era has revealed a reduced capacity for gas exchange resulting from simplification of the distal lung structure with fewer, larger alveoli because of a failure of normal lung alveolar septation and pulmonary microvascular development. The mechanisms responsible for alveolar simplification in BPD have not been fully elucidated, but mounting evidence suggests that aberrations in the cross-talk between growth factors of the lung mesenchyme and distal airspace epithelium have a key role. Animal models that recapitulate the human condition have expanded our knowledge of the pathology of BPD and have identified candidate matrix components and growth factors in the developing lung that are disrupted by conditions that predispose infants to BPD and interfere with normal vascular and alveolar morphogenesis. This review focuses on the deviations from normal lung development that define the pathophysiology of BPD and summarizes the various candidate mesenchyme-associated proteins and growth factors that have been identified as being disrupted in animal models of BPD. Finally, future areas of research to identify novel targets affected in arrested lung development and recovery are discussed.

Endothelial progenitor cells, bronchopulmonary dysplasia and other short-term outcomes of extremely preterm birth

AIM

To evaluate the impact of endothelial progenitor cells (EPCs), a subset of committed circulatory stem cells, on the development of bronchopulmonary dysplasia (BPD) and other short term outcomes in a cohort of extremely premature newborns.

METHODS

Progenitor cells were quantified by flow cytometry at birth in 36 neonates born <=28 weeks of gestation and at 36 postmenstrual weeks in 18 of them. Cells expressing the stemness markers CD34, CD133, or both were defined as circulating progenitor cells (CPCs). EPCs were defined as CPCs co-expressing the endothelial marker KDR.

RESULTS

Mean (SD) gestational age and birth weight of the infants studied were 26.2(1.5) weeks and 761.6(171.8) grams, respectively. EPC levels at birth did not differ between infants who subsequently developed BPD (n=9) and those who did not (n=24) [CD34(+)KDR(+) EPCs: 81(34-41) vs 80(56-110), p=0.7] and were not correlated with the duration of mechanical ventilation or O2-dependence, nor with the need of surfactant replacement. Infants with a hemodynamically significant patent ductus arteriosus (PDA) (n=22) had significantly lower EPC levels at birth than those with no PDA (n=11) [CD34(+)KDR(+) cells: 47(34-92) vs 142(84.5-221), p=0.008]. Data from the 18 infants studied both at birth and at 36 postmenstrual weeks showed that, while CPCs sharply decline over time, levels of all EPCs phenotypes are preserved after delivery.

CONCLUSIONS

Levels of EPCs at birth did not affect the risk of developing BPD in our group of extremely premature neonates. However, the association between low EPC counts at birth and PDA may be clinically relevant, and deserves further studies.

Preterm infants with chronic lung disease: are protein and energy intakes after discharge sufficient for optimal growth?

AIM

To document post-discharge feeding practices of preterm infants with chronic lung disease (CLD) and determine if sufficient protein and energy is consumed for optimal growth.

METHOD

Protein and energy intakes of preterm infants with CLD were quantified through detailed analysis of measured food and fluid intakes at four corrected age (CA) assessments, post-discharge. Most of the infants were in hospital for the term assessment. Milk intake from breastfeeding was determined by test weighing. Protein and energy intakes were compared with the Australian and New Zealand Nutrient Reference Values (NRV) for healthy term-born infants, and CA z-scores for weight, length and head circumference were calculated using Australian national gestational growth data and Centre for Disease Control 2000 growth data.

RESULTS

Ten of the 28 CLD infants who were exclusively receiving expressed breast milk in hospital were transitioned to infant formula within 1 month of discharge. Complementary foods were introduced at a median CA of 3.6 months. Protein intakes almost always exceeded the NRV for healthy term-born infants, and at each assessment, at least 63% of infants met the energy NRV. Longitudinal growth data are available for 20 infants, four of whom had been small for gestational age. At the 12-month assessment, 10 of these infants weighed less than the 10th percentile.

CONCLUSION

Preterm infants who develop CLD do not always achieve reference growth in their first year following discharge, despite protein and energy intakes being mostly comparable to those recommended for healthy term-born infants.

Use of azithromycin for the prevention of bronchopulmonary dysplasia in preterm infants: a randomized, double-blind, placebo controlled trial

OBJECTIVE

Since preventive therapies for bronchopulmonary dysplasia (BPD) are limited we treated preterm infants with azithromycin to decrease the incidence of BPD.

METHODS

Infants less than 1,250 g birth weight were randomized to azithromycin or placebo within 12 hr of beginning mechanical ventilation and within 72 hr of birth. The treatment group received azithromycin 10 mg/kg/day for 7 days followed by 5 mg/kg/day for a maximum of 6 weeks. Aspirates were collected during the study to assay for Ureaplasma. The primary endpoints were incidence of BPD or mortality. (Clinical Trials Identifier: NCT00319956.)

RESULTS

A total of 220 infants were enrolled (n=111 azithromycin, and 109 placebo). Mortality was 18% for the azithromycin group versus 22% for the placebo group (P = 0.45). Incidence of BPD was 76% for the azithromycin group versus 84% for the placebo group (P=0.2). The multiple logistic regression analysis demonstrated an odds ratio of 0.46 decrease in the chance of developing BPD or death for the azithromycin group, but was not statistically significant. The incidence of BPD in the Ureaplasma subgroup was 73% in the azithromycin group versus 94% in the placebo group (P=0.03). Analysis of patients in the Ureaplasma subgroup only, using the exact logistic model demonstrated a decrease in BPD or death in the azithromycin group with an estimated odds ratio of 0.026 (0.001-0.618, 95% confidence interval).

CONCLUSIONS

Routine use of azithromycin therapy for the prevention of BPD cannot be recommended. The early treatment of Ureaplasma colonized/infected patients might be beneficial, but a larger multi-centered trial is required to assess this more definitively.

Long term consequences of oxygen therapy in the neonatal period

Preterm and term infants are frequently exposed to high concentrations of oxygen for prolonged periods. In experimental models, high and prolonged oxygen exposures cause delayed alveolar septation and a bronchopulmonary dysplasia phenotype. Often, however, the oxygen exposure is tolerated in that the infants recover without severe lung or systemic injury. Multiple exposures change oxygen sensitivity in adult and newborn animals. Examples are antenatal corticosteroids, inflammatory mediators or preconditioning with oxygen, which will increase tolerance to oxygen injury. Intrauterine growth restriction or postnatal nutritional deficits will increase oxygen injury. Different infants probably have quite variable sensitivities to oxygen injury, but there are no biomarkers available to predict the risk of oxygen injury.

The 'new' bronchopulmonary dysplasia: challenges and commentary

Lung development is orchestrated by highly integrated morphogenic programs of interrelated patterns of gene and protein expression. Injury to the developing lung in the canalicular and saccular phases of lung development alters subsequent alveolar and vascular development resulting in simplified alveolar structures, dysmorphic capillary configuration, variable interstitial cellularity and fibroproliferation that are characteristic of the 'new' bronchopulmonary dysplasia (BPD). Fetal and neonatal infection, abnormal stretch of the developing airways and alveoli, altered expression of surfactant proteins (or genetically altered proteins), polymorphisms of genes encoding for vascular endothelial growth factors, and reactive oxygen species result in imparied gas exchange in the developing lung. However, the 'new' BPD represents only one form of neonatal chronic lung disease and the consistent use of both the physiologic definition and severity scale would provide greater accuracy in determining the impact of the disease currently defined by its treatment. Our present labelling of the clinical state of oxygen supplementation and/or ventilatory support at 36 weeks' postmenstrual age and the histopathologic severity of alveolar arrest and vascular 'simplification' may not always be predictive of the degree of altered lung development and thus longer-term pulmonary function evaluations are needed to determine the impact of this disorder in specific infants. The proposed role of novel molecular therapies, and the combined effects of currently established therapies, as well as exogenous surfactant and inhaled nitric oxide or repetitive surfactant dosing, on the severity and incidence of new BPD hold considerable promise for reducing the long-term pulmonary morbidity among infants delivered prematurely.

Prenatal factors in the development of chronic lung disease

Chronic lung disease (CLD), defined as chronic oxygen dependency, is a common outcome of neonatal intensive care. It occurs most frequently in infants born very prematurely, but also in infants born at term who had severe lung disease and those with abnormal antenatal lung growth due particularly to reduction in fetal breathing movements, amniotic fluid volume or intrathoracic space. There are, however, other causes and the importance of antenatal infection/inflammation regarding impairment of antenatal lung growth is increasingly recognised. Affected infants can suffer chronic respiratory morbidity including an excess of respiratory symptoms and lung function abnormalities even in adulthood. Antenatal interventions directed at improving lung growth are available, but require testing inappropriately designed trials with pulmonary function at follow-up as an outcome.

Chronic lung disease of prematurity: a short history

Chronic lung disease of prematurity (CLD) is commonly considered to be a consequence of assisted ventilation. However, prior to the description in 1967 of bronchopulmonary dysplasia (BPD), following ventilator therapy for respiratory distress syndrome, Wilson-Mikity syndrome (WMS) had been described in very preterm infants on minimal oxygen supplementation. In the 1970s and 1980s, many infants treated with assisted ventilation required prolonged mechanical ventilation after developing radiographic features of coarse infiltrates, severe hyperinflation, and microcystic changes, associated with hypercarbemia and the need for increased inspired oxygen concentrations. Some infants died and showed evidence of pulmonary fibrosis, obstructive bronchiolitis, and dysplastic change. The role of supplemental oxygen, positive pressure ventilation, and the immaturity of the lung have long been considered important in the etiology of CLD/BPD. More recently, the role of inflammation (particularly antenatal exposure to cytokines) and individual susceptibility (genetic predisposition) have assumed greater etiologic importance. The historical setting into which corticosteroid treatment for BPD was introduced is also discussed. After the licensing of exogenous surfactant to treat RDS in the early 1990s and more widespread use of prenatal corticosteroids in the mid-1990s, severe BPD became an unusual event. Gradually, the diagnosis of CLD, still often referred to as BPD, was based on an oxygen requirement at 36 weeks postmenstrual age. However, it is not clear that this 'new BPD' is substantially different from WMS. It is difficult to make prognostications about long-term lung function of these infants based on oxygen 'requirement' at 36 weeks, since supplemental oxygen is frequently used unnecessarily.

Congenital and opportunistic infections: Ureaplasma species and Mycoplasma hominis

There is strong evidence from clinical and experimental animal studies that ureaplasmas can invade the amnionic sac and induce an inflammatory response resulting in chorioamnionitis, preterm labor and neonatal lung injury. The ability of Ureaplasma spp. and Mycoplasma hominis to cause pneumonia, bacteremia, and meningitis in newborns can no longer be questioned. The association of Ureaplasma spp. with bronchopulmonary dysplasia has been supported by the majority of observational studies, but proof of causality is still lacking. The availability of molecular diagnostic technologies has enabled the designation of the two Ureaplasma biovars as individual species, but additional work must be done to establish whether there is differential pathogenicity between the Ureaplasma spp. or among their respective serovars. Future investigations to prevent prematurity should be directed toward identification and localization of specific micro-organisms combined with targeted antibiotic trials to determine whether such interventions can improve long-term infant outcomes.

Signal Transduction and Procoagulant State of Human Cord Blood—Progenitor-Derived Endothelial Cells after Interleukin-1α Stimulation

Isolation of endothelial progenitors from human umbilical cord blood generated great hope in vascular tissue engineering. However, before clinical use, progenitor derived endothelial cells (PDECs) have to be compared with mature endothelial cells (ECs). The aim of this study was to explore the behavior of PDECs exposed to a proinflammatory cytokine (interleukin-1alpha; IL-1alpha) according to the mitogen-activated protein (MAP) kinase and nuclear factor (NF)-kappaB signal transduction pathways as well as procoagulant activity (PCA). CD34(+) mononuclear cells were isolated using magnetic beads, cultured, and compared with human saphenous vein ECs (HSVECs). PDECs express endothelial markers: CD31, VE-cadherin, von Willebrand factor, KDR, and incorporate acetylated low-density lipoprotein (Dil-Ac-LDL). IL-1alpha similarly activates c-Jun N-terminal protein kinase (JNK) and p38 pathways in HSVECs and PDECs, whereas extracellular signal-related kinase (ERK)1/2 phosphorylation is lower in PDECs than in HSVECs. Low ERK1/2 phosphorylation in PDECs was specific to IL-1alpha as vascular endothelial growth factor (VEGF) similarly stimulated ERK1/2 pathway. With respect to inhibitor of NF-kappa B (Ikappa B) degradation, NF-kappa B translocation and phosphorylation, the NF-kappa B pathway is comparable in HSVECs and PDECs after stimulation. PCA and tissue factor level induced by IL-1alpha are lower in PDECs than in HSVECs. Thus, our data show that PDECs display the characteristics of functional mature ECs under IL-1alpha stimulation. However, we observed significant differences between PDECs and HSVECs related to both ERK1/2 pathway activation and tissue factor production.

Gender-related effects of prenatal administration of estrogen and progesterone receptor antagonists on VEGF and surfactant-proteins and on alveolarisation in the developing piglet lung

BACKGROUND

Vascular endothelial growth factor (VEGF) is essential for embryonic lung development and has been shown to be regulated by estradiol (E2) and progesterone (P).

AIM

To investigate the effects of prenatal E2 and P withdrawal by specific receptor antagonists on the mRNA expression of VEGF, surfactant proteins (SP-B and SP-C) and on alveolarisation in lung tissue of male and female pig fetuses.

METHODS

Fetuses from 10 sows were randomized to receive either both an intramuscular injection of the E2 receptor blocker ICI 182.780 and the P receptor blocker RTI 3021-022 (ICI+RTI, n=5) or a placebo injection (n=5) at 90 days of gestation (DOG, 115=term). After delivery by cesarean section on 114 DOG, tissue of the left lingula of the piglet's lung (28 placebo, 26 ICI+RTI) was obtained to determine the mRNA expression of VEGF, SP-B and SP-C. Lungs from 15 placebo and 14 ICI+RTI group piglets were removed and alveolar counts performed.

RESULTS

The ICI+RTI group showed significantly lower SP-C mRNA expression and alveolar counts compared to the placebo group (p=0.04 and 0.03, respectively). Diminished alveolarisation in the ICI+RTI group was mainly due to the reduction of alveolar counts in male piglets (p=0.02). Within the placebo group VEGF and SP-B mRNA expression in male piglets were significantly lower compared to female piglets (p=0.01 and 0.004, respectively). ICI+RTI treatment abolished this gender-related difference.

CONCLUSION

Estradiol and P antagonism affected gender-related differences of key proteins for pulmonary function and development and especially in males was associated with diminished alveolarisation.

Inhaled nitric oxide for preterm neonates

The evidence for the benefits of inhaled nitric oxide (iNO) on gas exchange, cytokine-induced lung inflammation, and vascular dysfunction has been demonstrated by several animal and human studies. The use of iNO in extremely low birth weight neonates for the prevention of adverse outcomes like chronic lung disease and neurologic injury has been investigated, but the findings remain inconclusive. This review briefly outlines the biologic rationale for the use of iNO in preterm neonates and the results on the outcome measures of bronchopulmonary dysplasia and brain injury from the recent clinical trials. This article focuses on the potential toxicities, persistent controversies, and unanswered questions regarding the use of this treatment modality in this patient population at high risk for adverse outcomes.

Combined application of 17beta-estradiol and progesterone enhance vascular endothelial growth factor and surfactant protein expression in cultured embryonic lung cells of mice

Preterm delivery is associated with disruption of the placental supply with 17beta-estradiol (E2) and progesterone (P). The aim is to evaluate the role of E2 and P on the regulation of key proteins in lung development in embryonic lung cells. Alveolar cell type II (AT-II) and central lung fibroblast cultures were established from mouse embryos. Cells were exposed for 24 hours to E2 and/or P, the estrogen receptor antagonist ICI 182.780 (ICI) and the progesterone receptor antagonist mifepristone (RU 486). The mRNA expression of vascular endothelial growth factor (VEGF) and surfactant protein B and C (SB-B, SB-C) was determined, and protein levels of VEGF were measured. Only the combined treatment with E2 and P increased mRNA expression and VEGF protein in AT-II cells and lung fibroblasts. Combined treatment also promoted SP-B and SP-C expression in AT-II cells. Pretreatment with ICI and RU 486 completely abolished the E2 and P induced effects. E2 and P enhanced expression of VEGF and surfactant proteins in primary embryonic lung cells and may be involved in regulating expression of key molecules for the prenatal lung development and postnatal lung function.

Below median birth weight in appropriate-for-gestational-age preterm infants as a risk factor for bronchopulmonary dysplasia

AIMS

To assess the presence of chorioamnionitis and intrauterine growth as prenatal risk factors for broncho pulmonary dysplasia (BPD) in appropriate-for-gestational-age (AGA) infants of <28 weeks' gestation.

METHODS

Gender, race, birth weight, gestational age, histology of the placenta, diagnosis of BPD at 36 weeks' gestation, postnatal dexamethasone treatment, and death were recorded in 150 preterm infants born at <28 weeks' gestation, and admitted between 1996 and 2001.

RESULTS

In 122 AGA infants (mean gestational age: 26.18 weeks, mean birth weight: 837 g), BPD was associated with gestational age-related birth weights below the 50(th) centile. Intrauterine growth deceleration started between 25 and 26 weeks' gestation. Chorioamnionitis was not related to BPD.

CONCLUSIONS

AGA infants of 26-28 weeks' gestation with birth weights below the median showed an increased risk of developing BPD.

Influence of lung oxidant and antioxidant status on alveolarization: role of light-exposed total parenteral nutrition

Parenteral multivitamins (MVP) are linked to the generation of peroxides, which cause oxidant injury in lungs associated with alveolar remodelling linked to lung disease of prematurity. This study was to investigate the relationship between alveolar development and lung oxidant-antioxidant status as modulated by the mode of administration of multivitamins with total parenteral nutrition (TPN). Four groups of guinea pig pups received parenteral nutrition differing by 1) mode of MVP admixture: with amino acid solution (AA-MVP) or lipid emulsion (LIP-MVP); 2) light exposure: TPN exposed (LE) or shielded from light (LP). After 2 or 4 days of TPN, vitamins C and E, 8-isoprostaneF2alpha and alveolarization index were determined in lungs and GSSG/GSH in lungs and blood. Exposure to light and the mode of MVP admixture did not influence vitamin E and isoprostane levels. Blood glutathione redox potential was more oxidized in LE and LIP-MVP groups after 4-day infusions, whereas lung redox potential was more reduced in LE groups. LP and LIP-MVP had a beneficial effect, with higher number of alveoli. Globally, results indicate that in this model, alveolarization and modifications in lung redox potential are two independent events induced by light exposed TPN.

Endothelial function in children with a history of premature prolonged rupture of membranes and bronchopulmonary dysplasia--a pilot study

AIM

To investigate vascular function in children with a neonatal history of generalised inflammation indicated by premature prolonged rupture of membranes (PPROM) and bronchopulmonary dysplasia (BPD).

METHODS

Children born at <or=30 weeks 1994-2000 were investigated at a present age of 6-12 years. Twenty-eight children participated and were divided into two groups with regard to BPD/no BPD (n=15/13) and PPROM/no PPROM (n=10/18). Vascular endothelial function was assessed by acetylcholine (ACh)-induced skin vasodilatation.

RESULTS

Maximum ACh-induced skin perfusion was statistically significantly lower in the PPROM group compared with the non-PPROM group (p=0.045) after adjustment for confounders. We found no association between BPD and maximum ACh-induced skin perfusion (p=0.404), after adjustment for confounders.

CONCLUSION

A neonatal history of prolonged premature rupture of membranes was associated with later impairment of vascular endothelial function in childhood. This association was not observed with BPD. Some forms of perinatal inflammation may be associated with later cardiovascular function.

Lung parenchyma at maturity is influenced by postnatal growth but not by moderate preterm birth in sheep

BACKGROUND

We have recently shown that moderate preterm birth, in the absence of respiratory support, altered the structure of lung parenchyma in young lambs, but the long-term effects are unknown.

OBJECTIVES

To determine whether structural changes persist to maturity, and whether postnatal growth affects lung structure at maturity in sheep.

METHODS

At approximately 1.2 years after birth, lung parenchyma of sheep born 14 days before term (n = 7) was stereologically compared with that of controls born at term (n = 8, term approx. 146 days).

RESULTS

Preterm birth per se had no significant effect on lung volume, alveolar number and size, and thicknesses of the alveolar walls and blood-gas barrier. After combining the preterm and term groups, we examined the effects of postnatal growth rates on lung parenchyma. Slower-growing sheep (SG; n = 7: 4 preterm, 3 term) were compared with faster-growing sheep (FG; n = 8: 3 preterm, 5 term). At approximately 1.2 years, the right lung volume, relative to body weight, was significantly lower in SG than FG sheep (p < 0.05) and alveolar number was significantly lower by approximately 44%. The total alveolar internal surface area of the right lung of SG sheep was 38% smaller than in FG sheep; it was also significantly lower when related to both lung and body weight.

CONCLUSIONS

Our data suggest that moderate preterm birth does not cause persistent alterations in lung parenchyma. However, slow postnatal growth in low-birth-weight sheep results in smaller lungs with fewer alveoli and a lower alveolar surface area relative to body weight.

Inhaled nitric oxide for the treatment of preterm infants with respiratory distress syndrome

Many authors have hypothesized that inhaled nitric oxide (iNO) might acutely improve oxygenation in preterm neonates with infant respiratory distress syndrome (iRDS) and decrease the risk of bronchopulmonary dysplasia. The studies on the effects of iNO in preterm infants with iRDS have given contradictory results. We report their main methodological characteristics and the observed effects of iNO in preterm infants. Moreover, we discuss the infants' age at the beginning of the study, the dose and duration of iNO therapy, its potential effect on neurodevelopment, its relationship with surfactant properties, and the need to identify patients who are likely to respond to this therapy. We advise caution against the widespread use of iNO in preterm infants with iRDS. At present, it appears to be premature to have specific recommendations regarding the indications for iNO therapy in this group of patients. The conclusion of current trials and the follow-up studies of recently completed trials will give further data to guide neonatologists' decisions, and until then it is likely that clinicians will continue to make case-by-case decisions for the treatment of iNO in preterm infants with hypoxia that is unresponsive to other therapies. However, this decision should always be discussed with the parents.

Cord blood KL-6, a specific lung injury marker, correlates with the subsequent development and severity of atypical bronchopulmonary dysplasia

BACKGROUND

A considerable number of preterm infants may have been exposed to inflammation in utero and may be born with an inflamed lung.

OBJECTIVES

To determine the impact of antenatal lung injury and inflammatory response on the pathogenesis of bronchopulmonary dysplasia (BPD) according to its clinical pattern, using KL-6 (as a lung injury marker) and C-reactive protein (CRP) (as a marker of inflammatory response).

METHODS

In this case-control study, a total of 74 infants (<32 weeks of gestation) including BPD with minimal early lung disease ('atypical'; 21 infants), BPD with significant early lung disease ('classic'; 29 infants) and the non-BPD (24 infants) groups underwent KL-6 and CRP in cord blood determinations.

RESULTS

The cord plasma KL-6 levels were significantly higher in the atypical and the total BPD groups than in the non-BPD group (median = 60.9 vs. 34.5 U/ml, p = 0.031; 43.5 vs. 34.5 U/ml, p = 0.02). However, the cord plasma CRP levels were not significantly different among the study groups. The cord plasma KL-6 levels in patients with atypical BPD were significantly higher in infants with moderate or severe BPD than in infants with mild BPD (median = 88.3 vs. 41.5 U/ml, p = 0.041) and were found to be significantly correlated with the duration of oxygen therapy (r = 0.502, p = 0.024).

CONCLUSIONS

The present study shows that cord plasma KL-6, a specific lung injury marker, is increased and objectively reflects disease severity in atypical BPD.

In preterm neonates, is the risk of developing bronchopulmonary dysplasia influenced by the failure to protect total parenteral nutrition from exposure to ambient light?

Light-exposed total parenteral nutrition (TPN) generates peroxides that contribute to an oxidant load. Shielding TPN from light protects against lung remodelling. In preterm infants, photoprotection of TPN is associated with a 30% reduction in bronchopulmonary dysplasia in a post-hoc analysis. This analysis provides justification for a randomized controlled trial.

Effects of beta2-glycoprotein-I on platelet aggregation in cord versus adult whole blood

We present a peculiarity of the neonatal hemostatic system that might contribute to establish a procoagulant readiness in neonatal blood by sensitizing neonatal platelets for ADP stimulation. beta2-glycoprotein-I (beta2-GP-I) is a plasma constituent capable of suppressing ADP-induced platelet aggregation. We found significant lower levels of beta2-GP-I in cord vs. adult plasma (120 +/- 27 vs. 180 +/- 37 microg/mL, P<0.001). We demonstrate dose-dependent inhibition of ADP-induced platelet aggregation in cord whole blood (WB) in the presence of increasing amounts of beta2-GP-I, evaluated by means of WB aggregometry employing the impedance method. Particularly, raising the beta2-GP-I concentration in cord WB from neonatal level up to the respective adult value caused significant reduction of amplitude (from 9.5 +/- 2.7 to 2.8 +/- 0.9 Omega, P<0.001) and of slope (from 5.9 +/- 2.4 to 1.89 +/- 0.9 Omega/min, P<0.001), and a significant prolongation of the aggregation time (from 51.8 +/- 22.9 to 110.8 +/- 60.3 s, P<0.001). In conclusion, physiological low levels of beta2-GP-I in cord WB cause enhanced responsiveness of neonatal platelets to ADP stimulation. This mechanism might help to explain the clinically observed well-functioning hemostasis in neonates.

Ureaplasma infection and neonatal lung disease

Infection with the ureaplasmas may occur in utero or perinatally in prematurely born infants. For some infants, infection with these organisms triggers a vigorous pro-inflammatory response in the lungs and increases the risk of developing bronchopulmonary dysplasia (BPD). At present, there is insufficient evidence from clinical trials to determine whether antibiotic treatment of Ureaplasma has any influence on the development of BPD and its comorbidities. Future investigation in the context of well-designed, adequately powered controlled clinical trials should focus on determining whether treatment of ureaplasmal infection lessens lung inflammation, decreases rates of BPD, and improves long-term, neurodevelopmental outcome.

A rational approach to home oxygen use in infants and children

The provision of supplemental oxygen for infants and children with hypoxaemia is expensive but advantageous because it facilitates earlier discharge from hospital and enhances quality of life in the home setting. It is seen as potentially cost effective and family friendly. However, the prescription of supplemental oxygen varies greatly between neonatologists, paediatric respiratory physicians and paediatric cardiologists. There is a lack of consensus on appropriate indications for prescribing oxygen, desirable oxygen targets and clinically significant immediate and longer-term outcome measures. Of the limited studies available, most are small studies reporting the treatment of infants with chronic neonatal lung disease with inconsistent outcome measures. Such data are not readily extrapolated to older children, who are also poorly served by existing data in adult studies. Further delineation of the indications for home oxygen therapy is required together with appropriately designed and funded multicentre trials to provide evidence for optimal oxygen therapy.

Inhaled nitric oxide in very preterm infants with severe respiratory distress syndrome

AIM

To test the hypothesis that inhaled nitric oxide therapy can decrease the incidence of bronchopulmonary dysplasia and death in preterm infants with severe respiratory distress syndrome; to evaluate the possible predictive factors for the response to inhaled nitric oxide therapy.

METHODS

Preterm infants (less than 30 weeks' gestation) were randomized to receive during the first week of life inhaled nitric oxide, or nothing, if they presented severe respiratory distress syndrome. Then, the treated infants were classified as non responders and responders.

RESULTS

Twenty infants were enrolled in the inhaled nitric oxide therapy group and 20 in the control group. Bronchopulmonary dysplasia and death were less frequent in the inhaled nitric oxide group than in the control group (50 vs. 90%, p=0.016). Moreover, nitric oxide treatment was found to decrease as independent factor the combined incidence of death and BPD (OR=0.111; 95% C.I. 0.02-0.610). A birth weight lower than 750 grams had a significant predictive value for the failure of responding to inhaled nitric oxide therapy (OR 12; 95% C.I. 1.3-13.3).

CONCLUSION

Inhaled nitric oxide decreases the incidence of bronchopulmonary dysplasia and death in preterm infants with severe respiratory distress syndrome. Birth weight may influence the effectiveness of inhaled nitric oxide therapy in promoting oxygenation improvement in preterm infants.

Definitions and diagnostic criteria for bronchopulmonary dysplasia

The changes in clinical presentation of bronchopulmonary dysplasia (BPD) in recent years have made many of the original definitions of BPD obsolete. The use of supplemental oxygen as a criterion for BPD diagnosis has many limitations. Supplemental oxygen is necessary to treat these infants, but at the same time it plays an important role in the pathogenesis of BPD. Because there are no accepted standards for supplemental oxygen administration, there are wide variations for its indications among different centers and this has a marked effect on the reported incidence of BPD. For this reason, it is essential to standardize the indications for supplemental oxygen when duration of oxygen therapy is used as the main criteria to diagnose BPD. Using supplemental oxygen need at specific time points does not necessarily reflect chronic lung damage and should be avoided as a single diagnostic criterion for BPD. A prolonged duration of supplemental oxygen is necessary to demonstrate the presence of chronic lung damage. The criteria based on supplemental oxygen at 36 weeks postmenstrual age has gained wide acceptance, but it is a less stringent criterion for the more mature infants. The longer the gestation, the shorter the time on oxygen that is required to meet this BPD criterion. None of the proposed criteria based on duration of oxygen therapy have shown a strong predictive value for long-term outcome. In view of all these shortcomings, it is essential to develop more objective physiologic tools to define the degree of lung damage and improve the prediction for long-term outcome in these infants.

Pathogenesis of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), initially described 40 years ago, is a dynamic clinical entity that continues to affect tens of thousands of premature infants each year. BPD was first characterized as a fibrotic pulmonary endpoint following severe Respiratory Distress Syndrome (RDS). It was the result of pulmonary healing after RDS, high oxygen exposure, positive pressure ventilation, and poor bronchial drainage secondary to endotracheal intubation in premature infants. With improved treatment for RDS, including surfactant replacement, oxygen saturation monitoring, improved modes of mechanical ventilation, antibiotic therapies, nutritional support, and infants surviving at younger gestations, the clinical picture of BPD has changed. In the following pages, we will summarize the multifaceted pathophysiologic factors leading to the pulmonary changes in "new" BPD, which is primarily characterized by disordered or delayed development. The contribution of hyperoxia and hypoxia, mechanical forces, vascular maldevelopment, inflammation, fluid management, patent ductus arteriosus (PDA), nutrition, and genetics will be discussed.

Pathology of bronchopulmonary dysplasia

Over the past three decades, advances in prenatal and neonatal intensive care have contributed to marked improvements in survival rates for extremely immature infants born during the canalicular phase of lung development at 24 to 26 weeks, a time when alveolar and distal vascular development is rapidly occurring. The histopathological lesions of severe airway injury and alternating sites of overinflation and fibrosis in "old" BPD have been replaced in "new" BPD with the pathologic changes of large, simplified alveolar structures, a dysmorphic capillary configuration, and variable interstitial cellularity and/or fibroproliferation. Airway and vascular lesions, when present, tend to be present in infants, who over time develop more severe disease. The concept that "new" BPD results in an arrest in alveolization should be modified to that of an impairment in alveolization as evidence shows that short ventilatory times and/or the use of nCPAP allow continued alveolar formation.

Expression of inflammation-related genes in endothelial cells is not directly affected by microparticles from preeclamptic patients

BACKGROUND

Inflammation and endothelial dysfunction are prominent in preeclampsia. Microparticles (MPs) may link these processes, as MPs induce the production of pro-inflammatory cytokines by endothelial cells and cause endothelial dysfunction.

AIM

To study changes in expression of inflammation-related genes in human endothelial cells in response to MPs from preeclamptic patients.

METHODS

Human umbilical vein endothelial cells (HUVECs) were incubated for various time intervals in the absence or presence of isolated MP fractions from preeclamptic patients (n = 3), normotensive pregnant women (n = 3), non-pregnant controls (n = 3), and interleukin (IL)-1alpha as a positive control. Total RNA was isolated and used for multiplex ligation-dependent probe amplification (MLPA) and real-time polymerase chain reaction (PCR).

RESULTS

IL-1alpha enhanced the expression of IL-1alpha, IL-2, IL-6, and IL-8; nuclear factor of kappa light chain enhancer in B-cells (NFkappaB)-1, NFkappaB-2, and NFkappaB-inhibitor; cyclin-dependent kinase inhibitor and monocyte chemotactic protein-1; and transiently increased tissue factor expression. RNA expression of inflammation-related genes and genes encoding adhesion receptors, however, were unaffected by any of the MP fractions tested.

CONCLUSION

MLPA is a suitable assay to test the inflammatory status of endothelial cells, because incubation with IL-1alpha triggered substantial changes in RNA expression in endothelial cells. Taken together, it seems unlikely that MPs from preeclamptic patients induce endothelial dysfunction by directly affecting the expression of inflammation-related genes in these cells.