Surfactant replacement therapy for preterm and term neonates with respiratory distress

Aerosol delivery of dry powder synthetic lung surfactant to surfactant-deficient rabbits and preterm lambs on non-invasive respiratory support

Background: The development of synthetic lung surfactant for preterm infants has focused on peptide analogues of native surfactant proteins B and C (SP-B and SP-C). Non-invasive respiratory support with nasal continuous positive airway pressure (nCPAP) may benefit from synthetic surfactant for aerosol delivery. Methods: A total of three dry powder (DP) surfactants, consisting of phospholipids and the SP-B analogue Super Mini-B (SMB), and one negative control DP surfactant without SMB, were produced with the Acorda Therapeutics ARCUS® Pulmonary Dry Powder Technology. Structure of the DP surfactants was compared with FTIR spectroscopy, in vitro surface activity with captive bubble surfactometry, and in vivo activity in surfactant-deficient adult rabbits and preterm lambs. In the animal experiments, intratracheal (IT) aerosol delivery was compared with surfactant aerosolization during nCPAP support. Surfactant dosage was 100 mg/kg of lipids and aerosolization was performed using a low flow inhaler. Results: FTIR spectra of the three DP surfactants each showed secondary structures compatible with peptide folding as an α-helix hairpin, similar to that previously noted for surface-active SMB in other lipids. The DP surfactants with SMB demonstrated in vitro surface activity <1 mN/m. Oxygenation and lung function increased quickly after IT aerosolization of DP surfactant in both surfactant-deficient rabbits and preterm lambs, similar to improvements seen with clinical surfactant. The response to nCPAP aerosol delivery of DP surfactant was about 50% of IT aerosol delivery, but could be boosted with a second dose in the preterm lambs. Conclusions: Aerosol delivery of active DP synthetic surfactant during non-invasive respiratory support with nCPAP significantly improved oxygenation and lung function in surfactant-deficient animals and this response could be enhanced by giving a second dose. Aerosol delivery of DP synthetic lung surfactant has potential for clinical applications.

Surfactant Administration via Thin Catheter: A Practical Guide

Exogenous surfactant replacement is the most effective evidence-based therapy for respiratory distress syndrome in preterm infants. The mode of administration has evolved in the last decade towards less invasive techniques that aim to effectively provide an adequate dose of surfactant, while allowing spontaneous respiration to continue, and with the support of continuous positive airway pressure. Surfactant delivery via aerosolisation, pharyngeal instillation, and laryngeal mask are being actively pursued in research, but have not yet been adopted to any significant degree in clinical practice. Surfactant administration via thin catheter, on the other hand, is becoming more widely used in neonatal intensive care units worldwide and is now an acknowledged alternative to the standard mode of surfactant delivery. Different devices, including nasogastric tubes, vascular catheters, and purpose-built surfactant instillation catheters are used. We present here a contemporary review of surfactant administration via thin catheter, in a practical guide format that reflects the individual and collective scientific opinions of the clinicians who participated in formulating the guide.

Paving the Road for Mesenchymal Stem Cell-Derived Exosome Therapy in Bronchopulmonary Dysplasia and Pulmonary Hypertension

Bronchopulmonary dysplasia (BPD) is a chronic neonatal lung disease characterized by inflammation and arrest of alveolarization. Its common sequela, pulmonary hypertension (PH), presents with elevated pulmonary vascular resistance associated with remodeling of the pulmonary arterioles. Despite notable advancements in neonatal medicine, there is a severe lack of curative treatments to help manage the progressive nature of these diseases. Numerous studies in preclinical models of BPD and PH have demonstrated that therapies based on mesenchymal stem/stromal cells (MSCs) can resolve pulmonary inflammation and ameliorate the severity of disease. Recent evidence suggests that novel, cell-free approaches based on MSC-derived exosomes (MEx) might represent a compelling therapeutic alternative offering major advantages over treatments based on MSC transplantation. Here, we will discuss the development of MSC-based therapies, stressing the centrality of paracrine action as the actual vector of MSC therapeutic functionality, focusing on MEx. We will briefly present our current understanding of the biogenesis and secretion of MEx, and discuss potential mechanisms by which they afford such beneficial effects, including immunomodulation and restoration of homeostasis in diseased states. We will also review ongoing clinical trials using MSCs as treatment for BPD that pave the way for bringing cell-free, MEx-based therapeutics from the bench to the NICU setting.

Bronchopulmonary Dysplasia: 50 Years after the Original Description

Bronchopulmonary dysplasia (BPD) is one of the few diseases in neonatal medicine that has continued to evolve since its first description about 50 years ago. Over these years, advancements in neonatal medicine such as antenatal steroids and exogenous surfactant therapy have significantly reduced neonatal mortality and lowered the limits of viability for preterm infants. Although the incidence of BPD continues to be high, especially in extremely low birth weight infants, the clinical picture has evolved into a milder disease with low mortality or significant morbidities. This new BPD is the result of complex interactions between altered alveolar and vascular development, injury by ante- and postnatal pathogenic factors, and reparative processes in the lung. There has been significant progress in our understanding of risk factors for BPD, but challenges persist in its definition, and in finding effective preventive strategies. There are promising developments with newer preventive interventions such as mesenchymal stem cells, exosomes, immunomodulators, and growth factors, but they are still in preclinical stage. The future challenges include finding ways to define BPD based on the severity of lung pathology, which can better predict long-term outcomes, development of early predictors of lung disease, and finding innovative and evidence-based preventive and management strategies.

Prevention and Treatment of Respiratory Distress Syndrome in Preterm Neonates

Respiratory distress syndrome (RDS) impacts a high proportion of preterm neonates, resulting in significant morbidity and mortality. Advances in pharmacotherapy, specifically antenatal corticosteroids and postnatal surfactant therapy, have significantly reduced the incidence and impact of neonatal RDS. Antenatal corticosteroids accelerate fetal lung maturation by increasing the activity of enzymes responsible for surfactant biosynthesis, resulting in improved lung compliance. Maternal antenatal corticosteroid treatment has improved survival of preterm neonates and lowered the incidence of brain injury. After birth, exogenous surfactant administration improves lung compliance and oxygenation, resulting in reductions in the incidence of pneumothorax and of death. Future research will identify the optimal surfactant product, timing of the initial dose, and mode of delivery.

The scope and extent of exogenous surfactant utilization in Nigerian health care facilities: benefits of its regular use to outcome of premature babies

Background: Surfactant replacement therapy (SRT) is the standard of care in developed countries. Poor access to surfactant limits its use in low resource settings. The extent of its use and the effect of its regular use on the preterm in such settings is unknown.Objective: This study assessed the extent of exogenous surfactant utilization in Nigerian tertiary care facilities and the benefits of its regular use to the preterm population.Methods: A two-phase cross-sectional study design evaluated the response from a respondent administered structured questionnaire addressed to health care providers from 54 centers and a targeted assessment of the outcome of the regular use of exogenous surfactant in a tertiary care facility from January 2014 to December 2016.Results: SRT was available in 16.7% of 54 units evaluated nationally; three (33.3%) were located in south-south and south-west respectively, 2 (22.2%) in southeast and one (11.1%) in north-central regions of the country. Twenty-two percent of the units were private centers, 77.8% were public tertiary care facilities. Four (44.4%) units provide SRT as the standard of care while five (66.6%) provide the service on request. One thousand one hundred twenty babies were admitted to the audited tertiary facility with 550 (49%) as preterms. Only 2.72% received surfactant replacement therapy. Sixty-six percent of recipients survived whilst 33.3% died. Respiratory support positively enhanced outcome in recipients of surfactant therapy.Conclusion: There is a limited use of surfactant nationally. Its use seemed to have improved survival.

Quantitative lipidomic analysis of mouse lung during postnatal development by electrospray ionization tandem mass spectrometry

Lipids play very important roles in lung biology, mainly reducing the alveolar surface tension at the air-liquid interface thereby preventing end-expiratory collapse of the alveoli. In the present study we performed an extensive quantitative lipidomic analysis of mouse lung to provide the i) total lipid quantity, ii) distribution pattern of the major lipid classes, iii) composition of individual lipid species and iv) glycerophospholipid distribution pattern according to carbon chain length (total number of carbon atoms) and degree of unsaturation (total number of double bonds). We analysed and quantified 160 glycerophospholipid species, 24 sphingolipid species, 18 cholesteryl esters and cholesterol from lungs of a) newborn (P1), b) 15-day-old (P15) and c) 12-week-old adult mice (P84) to understand the changes occurring during postnatal pulmonary development. Our results revealed an increase in total lipid quantity, correlation of lipid class distribution in lung tissue and significant changes in the individual lipid species composition during postnatal lung development. Interestingly, we observed significant stage-specific alterations during this process. Especially, P1 lungs showed high content of monounsaturated lipid species; P15 lungs exhibited myristic and palmitic acid containing lipid species, whereas adult lungs were enriched with polyunsaturated lipid species. Taken together, our study provides an extensive quantitative lipidome of the postnatal mouse lung development, which may serve as a reference for a better understanding of lipid alterations and their functions in lung development and respiratory diseases associated with lipids.

Poractant Alfa Versus Beractant for Neonatal Respiratory Distress Syndrome: A Retrospective Cost Analysis

OBJECTIVES The objectives of this study were to determine the average medication cost per patient of poractant alfa and beractant, and to compare the outcomes of treatment with these agents.

METHODS We conducted a retrospective, observational, cohort study of patients who received surfactant, before and after an institutional formulary change from beractant to poractant alfa. The primary outcome was the average medication cost per case. Secondary measures were clinical outcomes, including duration of respiratory support, length of hospital stay, and the occurrence of complications.

RESULTS A total of 114 patients were enrolled; 38 were treated with poractant alfa and 76 patients were treated with beractant. Baseline characteristics were similar between groups. The average medication cost per patient was $1756.44 ± $1030.06 and $1329.78 ± $705.64 for poractant alfa and beractant, respectively (p = 0.011). Patients treated with poractant alfa had a shorter length of stay (45.0 ± 30.5 days) than patients treated with beractant (65.1 ± 37.1 days) (p = 0.010). Rates of pneumothoraces, pulmonary hemorrhage, necrotizing enterocolitis, intraventricular hemorrhage, and mortality did not differ significantly between groups.

CONCLUSIONS We found an unanticipated increase in drug cost with poractant alfa compared to beractant.

Lung ultrasonography score versus chest X-ray score to predict surfactant administration in newborns with respiratory distress syndrome

OBJECTIVES

We aim to verify the diagnostic accuracy of a lung ultrasonography (LUS) score to early predict the need for surfactant therapy in newborns with respiratory distress syndrome (RDS), and to compare it with a chest X-ray score.

METHODS

In this prospective diagnostic accuracy study we included all newborns admitted for respiratory distress and initially treated with nasal CPAP. LUS was performed within 2 h from nasal CPAP positioning and in any case before surfactant administration. A chest X-ray was also performed. A LUS score and an X-ray score were used and compared. Ability of the scores to predict surfactant administration was evaluated through ROC analysis.

RESULTS

In our population of 56 newborns with mean gestational age of 31 weeks (SD 3) and mean birth weight of 1442 g (SD 520), LUS score showed higher AUC than X-ray score in early recognition of infants with respiratory distress syndrome requiring surfactant treatment (0.94; 95%CI, 0.89-0.98; P < 0.001 vs 0.80; 95%CI, 0.74-0.86; P < 0.001). It showed also higher sensitivity (86% vs 82%), higher specificity (88% vs 76%), better positive (83% vs 69%), and negative (91% vs 87%) predictive values.

CONCLUSIONS

LUS is a non-invasive, bedside and reproducible method that could improve the management of neonatal respiratory distress. It is accurate and reliable to early identify patients who will need treatment with surfactant allowing both an early treatment and a reduction of radiation exposure.

A sulfur-free peptide mimic of surfactant protein B (B-YL) exhibits high in vitro and in vivo surface activities

Background: Animal-derived surfactants containing surfactant proteins B (SP-B) and C (SP-C) are used to treat respiratory distress syndrome (RDS) in preterm infants. SP-B (79 residues) plays a pivotal role in lung function and the design of synthetic lung surfactant. Super Mini-B (SMB), a 41-residue peptide based on the N- and C-domains of SP-B covalently joined with a turn and two disulfides, folds as an α-helix hairpin mimicking the properties of these domains in SP-B. Here, we studied ‘B-YL’, a 41-residue SMB variant that has its four cysteine and two methionine residues replaced by tyrosine and leucine, respectively, to test whether these hydrophobic substitutions produce a surface-active, α-helix hairpin.

Methods: Structure and function of B-YL and SMB in surfactant lipids were compared with CD and FTIR spectroscopy, and surface activity with captive bubble surfactometry and in lavaged, surfactant-deficient adult rabbits.

Results: CD and FTIR spectroscopy of B-YL in surfactant lipids showed secondary structures compatible with peptide folding as an α-helix hairpin, similar to SMB in lipids. B-YL in surfactant lipids demonstrated excellent in vitro surface activity and good oxygenation and dynamic compliance in lavaged, surfactant-deficient adult rabbits, suggesting that the four tyrosine substitutions are an effective replacement for the disulfide-reinforced helix-turn of SMB. Here, the B-YL fold may be stabilized by a core of clustered tyrosines linking the N- and C-helices through non-covalent interactions involving aromatic rings.

Conclusions: ‘Sulfur-free’ B-YL forms an amphipathic helix-hairpin in surfactant liposomes with high surface activity and is functionally similar to SMB and native SP-B. The removal of the cysteines makes B-YL more feasible to scale up production for clinical application. B-YL’s possible resistance against free oxygen radical damage to methionines by substitutions with leucine provides an extra edge over SMB in the treatment of respiratory failure in preterm infants with RDS.

Review shows that using surfactant a number of times or as a vehicle for budesonide may reduce the risk of bronchopulmonary dysplasia

AIM

Bronchopulmonary dysplasia (BPD) remains the most common respiratory morbidity in immature infants. This review describes the diagnosis of BPD has evolved and summarises the therapeutic approaches that have made it possible to limit the incidence of BPD.

METHOD

We reviewed the literature from the first definition of BPD by Northway in 1967 to the surfactant treatment policies that are currently in use, drawing on more than 50 papers up to 2017.

RESULTS

Our review showed that improvements in neonatal survival have been associated with an increased risk of severe BPD, significant levels of long-term morbidity and the increased use of healthcare resources. These issues have encouraged researchers to explore potential new treatments that limit the incidence of BPD. Repeated surfactant instillation and the use of surfactant as a vehicle for budesonide are promising strategies for alleviating the burden of chronic lung disease. Ongoing research on surfactant or stem cell therapy may further improve the respiratory prognosis for prematurely born children.

CONCLUSION

Considerable research has been carried out into the increase in BPD, which has resulted from improvements in neonatal survival. Key areas of research include repeated surfactant administration, using surfactant as a vehicle for budesonide and stem cell therapy.

Review demonstrates that less invasive surfactant administration in preterm neonates leads to fewer complications

Surfactant treatment of neonatal respiratory distress syndrome (RDS) was introduced in Europe during the 1990s. Meta-analyses have indicated that using less invasive surfactant administration techniques on preterm neonates receiving continuous positive airway pressure (CPAP) results in improved survival rates without bronchopulmonary dysplasia. Surfactant should be administered early and ventilator settings adapted to changing oxygen requirements and lung mechanics. Side effects including initial bradycardia, oxygen desaturation, tube obstruction and isolated cases of pulmonary haemorrhage have been reported.

CONCLUSION

Less invasive surfactant therapy improves pulmonary outcomes in preterm neonates with RDS and should ideally be administered in combination with CPAP.

Effects of bovine lipid extract surfactant administration in preterm infants treated for respiratory distress syndrome

AIM

To review the initial effectiveness of bovine lipid extract surfactant (BLES) for the treatment of respiratory distress syndrome in preterm infants.

METHODS AND RESULTS

A retrospective review of data collected from infants born <37-week gestation with respiratory distress syndrome treated with BLES between February 1, 2015 and March 1, 2016. Data were analyzed to determine the timing of initial dose, the length of time to wean the fraction of inspired oxygen (FiO2) concentration to 0.21 following initial dose, and the number of repeated doses given during hospital admission. Infants were subgrouped by gestational age stratum, 230 to 276 weeks (group 1), 280 to 316 weeks (group 2), and 320 to 366 weeks (group 3). Ninety-eight infants received the surfactant during the study period. After applying exclusion criteria, 77 infants were analyzed. Mean (SD) gestational age was 28 (4) weeks, and mean (SD) birth weight was 1250 (602) g. Initial dose of BLES was given at a median (interquartile range) time of 29 (19-43) minutes in group 1, 150 (20-615) minutes in group 2, and 990 (53-2025) minutes in group 3. Median (interquartile range) length of time to wean the FiO2 concentration to 0.21 was 14 (5-56) minutes, 10 (5-53) minutes, and 10 (5-38) minutes in groups 1, 2, and 3, respectively. Ten infants required repeated doses.

CONCLUSION

Given the rapid response of BLES in all the groups, careful monitoring of ventilator parameters is paramount to allow for rapid weaning and early extubation to avoid lung injury associated with mechanical ventilation.

Gender-related efficacy of pulmonary surfactant in infants with respiratory distress syndrome: A STROBE compliant study

Whether gender influences the efficacy of exogenous pulmonary surfactant (PS) for replacement therapy in newborns with respiratory distress syndrome (RDS) has not been well studied yet.Retrospective cohort study design. Data on PS therapy including blood gas, oxygenation function parameters, and therapy results were collected and analyzed from 370 infants diagnosed with RDS in 20 hospitals of the Northwest China Neonatal Collaboration from January 2011 to December 2011.Female infants were more sensitive to PS treatment than males. In multivariate analysis, when adjusted for other variables, an increased initial dose of surfactant significantly reduced mortality risk (OR = 0.98, 95%CI [0.96, 0.99], P = .002). An interaction between gender and initial dose of PS was observed. In male infants, an increased initial dose of surfactant was correlated with reduced mortality risk (OR = 0.97, 95%CI [0.96, 0.99], P = 0.005), while in female infants, we failed to found a relationship between the initial dose of surfactant and the risk of mortality (OR = 0.99, 95%CI [0.96, 1.02], P = .543). Moreover, the effect of surfactant replacement therapy was better for female infants than male infants at initial PS doses <130 mg/kg.Gender influences the efficacy of PS treatment. An increased initial dose of PS should be used in RDS therapy for male infants.

Opportunities in posthemorrhagic hydrocephalus research: outcomes of the Hydrocephalus Association Posthemorrhagic Hydrocephalus Workshop

The Hydrocephalus Association Posthemorrhagic Hydrocephalus Workshop was held on July 25 and 26, 2016 at the National Institutes of Health. The workshop brought together a diverse group of researchers including pediatric neurosurgeons, neurologists, and neuropsychologists with scientists in the fields of brain injury and development, cerebrospinal and interstitial fluid dynamics, and the blood-brain and blood-CSF barriers. The goals of the workshop were to identify areas of opportunity in posthemorrhagic hydrocephalus research and encourage scientific collaboration across a diverse set of fields. This report details the major themes discussed during the workshop and research opportunities identified for posthemorrhagic hydrocephalus. The primary areas include (1) preventing intraventricular hemorrhage, (2) stopping primary and secondary brain damage, (3) preventing hydrocephalus, (4) repairing brain damage, and (5) improving neurodevelopment outcomes in posthemorrhagic hydrocephalus.

An oxidation-resistant peptide mimic of surfactant protein B (B-YL) forms an amphipathic helix-hairpin in liposomes with high surface activity

Background: Animal-derived surfactants containing surfactant proteins B (SP-B) and C (SP-C) are used to treat respiratory distress syndrome (RDS) in preterm infants. SP-B (79 residues) plays a pivotal role in lung function and the design of synthetic lung surfactant. Super Mini-B (SMB), a 41-residue peptide based on the N- and C-domains of SP-B joined with a turn and two disulfides, folds as an α-helix hairpin mimicking the properties of these domains in SP-B. Here, we studied ‘B-YL’, a 41-residue oxidation-resistant SMB variant that has its four Cys and two Met residues replaced by Tyr and Leu, respectively, to test whether these hydrophobic substitutions produce a surface-active, α-helix hairpin.Methods:Structure and function of B-YL and SMB in surfactant lipids were compared with CD and FTIR spectroscopy and molecular dynamic (MD) simulations, and surface activity with captive bubble surfactometry and in lavaged, surfactant-deficient adult rabbits.Results:CD and FTIR spectroscopy of B-YL in surfactant lipids showed secondary structures compatible with peptide folding as an α-helix hairpin, similar to SMB in lipids. MD simulations confirmed that B-YL maintained its α-helix hairpin in a lipid bilayer, matching the hairpin obtained from MD of SMB. Unlike the disulfide-reinforced helix-turn of SMB, the B-YL fold was stabilized by a core of clustered Tyr linking the N- and C-helices through noncovalent interactions involving aromatic rings. B-YL in surfactant lipids demonstrated excellentin vitrosurface activity and good oxygenation and dynamic compliance in lavaged, surfactant-deficient adult rabbits.Conclusions:‘Sulfur-free’ and ‘oxidation-resistant’ B-YL forms an amphipathic helix-hairpin in surfactant liposomes with high surface activity and is functionally similar to SMB and native SP-B. B-YL’s resistance against free oxygen radical damage provides an extra edge over oxidized SMB in the treatment of respiratory failure in preterm infants with RDS and children and adults with acute lung injury.

Respiratory Management of Extremely Preterm Infants: An International Survey

BACKGROUND

There are significant international variations in chronic lung disease rates among very preterm infants yet there is little data on international variations in respiratory strategies.

OBJECTIVE

To evaluate practice variations in the respiratory management of extremely preterm infants born at < 29 weeks' gestational age (GA) among 10 neonatal networks participating in the International Network for Evaluating Outcomes (iNeo) of Neonates collaboration.

METHODS

A web-based survey was sent to the representatives of 390 neonatal intensive care units from Australia/New Zealand, Canada, Finland, Illinois (USA), Israel, Japan, Spain, Sweden, Switzerland, and Tuscany (Italy). Responses were based on practices in 2015.

RESULTS

Overall, 321 of the 390 units responded (82%). The majority of units within networks (40-92%) mechanically ventilate infants born at 23-24 weeks' GA on continuous positive airway pressure (CPAP) with 30-39% oxygen in respiratory distress within 48 h after birth, but the proportion of units that offer mechanical ventilation for infants born at 25-26 weeks' GA at similar settings varied significantly (20-85% of units within networks). The most common respiratory strategy for infants born at 27-28 weeks' GA on CPAP with 30-39% oxygen with respiratory distress within 48 h after birth used by units also varied significantly among networks: mechanical ventilation (0-60%), CPAP (3-82%), intubation and surfactant administration with immediate extubation (0-75%), and less invasive surfactant administration (0-68%).

CONCLUSIONS

There are marked variations but also similarities in respiratory management of extremely preterm infants between networks. Further collaboration and exploration is needed to better understand the association of these variations in practice with pulmonary outcomes.

Delivery of Therapeutics to the Lung

Pulmonary delivery in animal models can be performed using either direct administration methods or by passive inhalation. Direct pulmonary delivery requires the animal to be endotracheally intubated, whereas passive delivery uses a nose-only or a whole-body chamber. Endotracheal delivery of therapeutics and vaccines allows investigators to deliver the payload directly into the lung without the limitations associated with passive pulmonary administration methods. Additionally, endotracheal delivery can achieve deep lung delivery without the involvement of other exposure routes and is more reproducible and quantitative than passive pulmonary delivery in terms of accurate dosing. Here we describe the endotracheal delivery of both liquids and dry powders for preclinical models of treatment and exposure.

Preventing cerebral palsy in preterm labour: a multiorganisational quality improvement approach to the adoption and spread of magnesium sulphate for neuroprotection

Magnesium sulphate has been demonstrated to be an effective neuroprotectant for babies delivered prematurely (under 37 weeks' gestational age). Antenatal administration reduces infant mortality and cerebral palsy (CP); however, uptake in the UK has been significantly lower than other countries. A quality improvement (QI) project (PReventing Cerebral palsy in Pre Term labour (PReCePT)) was carried out in the West of England, UK, to raise awareness of evidence and to improve the uptake of magnesium sulphate as neuroprotectant in preterm deliveries. Five National Health Service (NHS) Trusts and the West of England Academic Health Science Network participated in the QI project. The project was underpinned by a multifaceted QI approach that included: patient and clinical coproduction of resources; recruitment of clinical champions to support the local microsystems and create a stimulating/supporting environment for change; Plan, Do, Study, Act cycles; training for over 600 NHS staff and awareness raising and strategic influencing of key leaders. A baseline audit and regular measurement of the number of eligible women receiving magnesium sulphate was undertaken at each hospital site, and the overall programme was evaluated using data from an international benchmarking organisation for neonatal care outcomes-the Vermont Oxford Network. During the project 664 staff received magnesium sulphate training. The use of magnesium sulphate increased across the West of England from an average baseline of 21% over the 2 years preceding the project to 88% by the conclusion of the project. The project was also able to influence the development of a national data collection process for benchmarking the use of magnesium sulphate for neuroprotection in preterm deliveries in the U.K. PReCePT appears to have had a favourable effect on the uptake of magnesium sulphate across the West of England. The project has also provided learning about how to stimulate adoption and spread of evidence using a QI approach across a network.

Golden hour of neonatal life: Need of the hour

"Golden Hour" of neonatal life is defined as the first hour of post-natal life in both preterm and term neonates. This concept in neonatology has been adopted from adult trauma where the initial first hour of trauma management is considered as golden hour. The "Golden hour" concept includes practicing all the evidence based intervention for term and preterm neonates, in the initial sixty minutes of postnatal life for better long-term outcome. Although the current evidence supports the concept of golden hour in preterm and still there is no evidence seeking the benefit of golden hour approach in term neonates, but neonatologist around the globe feel the importance of golden hour concept equally in both preterm and term neonates. Initial first hour of neonatal life includes neonatal resuscitation, post-resuscitation care, transportation of sick newborn to neonatal intensive care unit, respiratory and cardiovascular support and initial course in nursery. The studies that evaluated the concept of golden hour in preterm neonates showed marked reduction in hypothermia, hypoglycemia, intraventricular hemorrhage (IVH), bronchopulmonary dysplasia (BPD), and retinopathy of prematurity (ROP). In this review article, we will discuss various components of neonatal care that are included in "Golden hour" of preterm and term neonatal care.

"New" bronchopulmonary dysplasia and chronic lung disease

Bronchopulmonary dysplasia (BPD) is the major cause of chronic lung disease and morbidity in preterm infants. Since it was first described fifty years ago, the epidemiology, pathogenesis, and treatment for BPD has changed dramatically. This review summarizes these changes and the clinical outcomes for infants diagnosed with BPD.

Surfactant effects on the viability and function of human mesenchymal stem cells: in vitro and in vivo assessment

BACKGROUND

Surfactant therapy has become the standard of care for preterm infants with respiratory distress syndrome. Preclinical studies have reported the therapeutic benefits of mesenchymal stem cells (MSCs) in experimental bronchopulmonary dysplasia. This study investigated the effects of a surfactant on the in vitro viability and in vivo function of human MSCs.

METHODS

The viability, phenotype, and mitochondrial membrane potential (MMP) of MSCs were assessed through flow cytometry. The in vivo function was assessed after intratracheal injection of human MSCs (1 × 10⁵ cells) diluted in 30 μl of normal saline (NS), 10 μl of a surfactant diluted in 20 μl of NS, and 10 μl of a surfactant and MSCs (1 × 10⁵ cells) diluted in 20 μl of NS in newborn rats on postnatal day 5. The pups were reared in room air (RA) or an oxygen-enriched atmosphere (85% O₂) from postnatal days 1 to 14; eight study groups were examined: RA + NS, RA + MSCs, RA + surfactant, RA + surfactant + MSCs, O₂ + NS, O₂ + MSCs, O₂ + surfactant, and O₂ + surfactant + MSCs. The lungs were excised for histological and cytokine analysis on postnatal day 14.

RESULTS

Compared with the controls, surfactant-treated MSCs showed significantly reduced viability and MMP after exposure to 1:1 and 1:2 of surfactant:MSCs for 15 and 60 minutes. All human MSC samples exhibited similar percentages of CD markers, regardless of surfactant exposure. The rats reared in hyperoxia and treated with NS exhibited a significantly higher mean linear intercept (MLI) than did those reared in RA and treated with NS, MSCs, surfactant, or surfactant + MSCs. Treatment with MSCs, surfactant, or surfactant + MSCs significantly reduced the hyperoxia-induced increase in MLI. The O₂ + surfactant + MSCs group exhibited a significantly higher MLI than did the O₂ + MSCs group. Furthermore, treatment with MSCs and MSCs + surfactant significantly reduced the hyperoxia-induced increase in apoptotic cells.

CONCLUSIONS

Combination therapy involving a surfactant and MSCs does not exert additive effects on lung development in hyperoxia-induced lung injury.

Prophylactic versus Early Rescue Surfactant Treatment in Preterm Infants Born at Less than 30 Weeks Gestation or with Birth Weight Less than or Equal 1,250 Grams

Prophylactic surfactant is known to be effective to reduce chronic lung disease in preterm infants compared with rescue surfactant treatment. In Korea, early prophylactic surfactant therapy was introduced in 2011. However, recently, the increased utilization of antenatal steroids and early stabilization through continuous positive airway pressure (CPAP) in the delivery room may have changed the risks and benefits of prophylactic surfactant therapy of infants at high risk of respiratory distress syndrome (RDS). We compared the effects and safety of prophylactic surfactant therapy (within 30 minutes after birth) and early selective surfactant therapy (within 3 hours after birth) in preterm infants born at < 30 weeks gestation or with birth weight ≤ 1,250 g. The clinical data of 193 infants in period 1 (from 2008 to 2010, early selective surfactant therapy group) were collected retrospectively; those of 191 infants in period 2 (from 2012 to 2014, prophylactic surfactant therapy group) were collected prospectively. Compared to period 1, the rate of intubation and surfactant use were significantly increased in period 2. The use of multiple doses of surfactant in period 2 was significantly increased compared with period 1. Despite more invasive and aggressive management in period 2, there was no difference in the duration of mechanical ventilation, the incidence of bronchopulmonary dysplasia (BPD) or death, and the risk of other adverse neonatal outcomes between the 2 groups. In conclusion, the benefit of prophylactic surfactant therapy in infants treated under current practices is no longer clear compared to early selective surfactant therapy.

Surfactant Therapy for Early Onset Pneumonia in Late Preterm and Term Neonates Needing Mechanical Ventilation

INTRODUCTION

Pathophysiology of pneumonia involves leakage of plasma proteins into the airways and accumulation of cytokines within the lung. Several in vitro and in vivo studies have demonstrated that this proteinaceous material and lung inflammation inhibit surfactant function.

AIM

To evaluate whether exogenous surfactant therapy improves oxygenation and gas exchange in late preterm and term neonates with early onset pneumonia and respiratory failure.

MATERIALS AND METHODS

This prospective interventional cohort study was conducted at a tertiary care neonatal unit. Twenty four late preterm and term neonates with early onset pneumonia requiring mechanical ventilation for respiratory failure were included and received surfactant therapy. Oxygenation index, arterial/alveolar PO₂ (a/A ratio), mean airway pressure and fraction of inspired oxygen were calculated from arterial blood gases obtained before and after surfactant therapy. Wilcoxon signed rank sum test was used for assessment of change in oxygenation variables 12 hours after surfactant therapy. Data regarding clinical outcomes and complications were collected and analysed.

RESULTS

Just over half (54.2%) of the study neonates were of term gestation. After surfactant therapy, the median Oxygenation Index (OI) decreased from 11.15 to 3.7 at one hour and the change was sustained and significant at 12 hours (p<0.05). The median a/A PO₂ ratio improved from 0.09 to 0.3 within one hour of surfactant replacement and the improvement was significant at 12 hours (p<0.01). Twenty two neonates (92%) survived to discharge. Median duration of hospital stay was 15 days.

CONCLUSION

Significant and rapid improvement in oxygenation in late preterm and term neonates with early onset pneumonia was seen after surfactant therapy, which is sustained for a longer period. There could be a substantial role for the use of surfactant in early onset pneumonia, although larger controlled trials are needed before definite recommendations can be made.

Surfactant administration via a thin endotracheal catheter during spontaneous breathing in preterm infants

To systematically review the clinical outcomes of surfactant administration via a thin endotracheal catheter during spontaneous breathing compared with conventional administration involving tracheal intubation, mechanical ventilation (MV), and tracheal extubation, in preterm infants. PubMed, EMBASE, and the Cochrane Library were searched to identify relevant clinical trials. Data were analyzed using the Cochrane Collaboration methods. Primary outcome measures included the incidence of MV and bronchopulmonary dysplasia (BPD). Finally, four RCTs, two prospective cohort trials, and six historical controlled trials involving 5,261 preterm infants were analyzed. In RCTs, surfactant administration though a thin catheter reduced the incidence of MV (risk ratio [RR]: 0.74; 95% confidence interval [CI]: 0.66, 0.81) in 72 hr and BPD (RR: 0.69, 95%CI: 0.50, 0.97) compared with conventional administration and in non-RCTs, there was also significant reduction in the incidence of MV (RR: 0.55, 95%CI: 0.45, 0.68) and BPD (RR: 0.70, 95%CI: 0.60, 0.82) in favor of the thin catheter group. There were no significant differences between the two procedures in terms of short-term pulmonary complications, intracranial pathology, necrotizing enterocolitis, retinopathy of prematurity, and mortality. Thus, surfactant administration via a thin endotracheal catheter to preterm infants has promising benefits, including reducing the incidences of MV and BPD, while providing comparable breathing support to conventional administration in MV. Pediatr Pulmonol. 2017; 52:844-854. © 2017 Wiley Periodicals, Inc.

Surfactant reduced the mortality of neonates with birth weight ⩾1500 g and hypoxemic respiratory failure: a survey from an emerging NICU network

OBJECTIVE

We evaluated the efficacy of surfactant therapy and assisted ventilation on morbidity and mortality of neonates with birth weight (BW) ⩾1500 g and hypoxemic respiratory failure (HRF).

STUDY DESIGN

We retrospectively analyzed 5650 patients with BW ⩾1500 g for incidence, management and outcome of HRF, defined as acute hypoxemia requiring mechanical ventilation and/or nasal continuous positive airway pressure ⩾24 h. The patients were allocated into groups of moderate preterm (1735, 30.7%), late preterm (1431, 25.4%), early term (ETM, 986, 17.5%), full term (1390, 24.6%) and post term (79, 1.4%), with gestational age ⩽33, 34 to 36, 37 to 38, 39 to 41 and ⩾42 weeks, respectively.

RESULTS

In the five groups, 66.9, 42, 21.6, 12.8 and 5.1% had respiratory distress syndrome (RDS). For pneumonia/sepsis and meconium aspiration syndrome (MAS), the proportion was 13.8%, 25.4%, 38.0%, 52.5% and 76.0%, respectively. Surfactant was given to 21.9% (n=1238) of HRF and 51.2% (n=1108) of RDS. Survival rates of RDS were 82.2%, 87.8%, 84.5%, 77.1% and 75.0%, respectively (numbers needed to treat was 8 to 11 for surfactant benefit). Overall mortality rate of HRF was 21%, or 17.9%, 14.7%, 25.6%, 28.9% and 39.2%, respectively. Mortalities of MAS and pneumonia/sepsis were 29.4 and 27.6%. Relative risk of death was associated with initial disease severity, female gender, mechanical ventilation and congenital anomalies by multivariate logistic regression analysis.

CONCLUSION

Surfactant was effective for infants with RDS and BW ⩾1500 g, and different incidences and outcome of HRF among GA groups reflected standard of perinatal and respiratory care in emerging neonatal intensive care unit network.

Lung-protective ventilatory strategies in intubated preterm neonates with RDS

This article provides a narrative review of lung-protective ventilatory strategies (LPVS) in intubated preterm infants with RDS. A description of strategies is followed by results on short-and long-term respiratory and neurodevelopmental outcomes. Strategies will include patient-triggered or synchronized ventilation, volume targeted ventilation, the technique of intubation, surfactant administration and rapid extubation to NCPAP (INSURE), the open lung concept, strategies of high-frequency ventilation, and permissive hypercapnia. Based on this review single recommendations on optimal LPVS cannot be made. Combinations of several strategies, individually applied, most probably minimize or avoid potential serious respiratory and cerebral complications like bronchopulmonary dysplasia and cerebral palsy.

The roles of drug therapy given via the endotracheal tube to neonates

Many drugs are given to intubated neonates by the inhalation route. The optimum aerosol delivery system, however, has not been identified and there are many challenges in delivering drugs effectively to the lower airways of intubated neonates. The effectiveness of surfactant in prematurely born infants and nitric oxide has been robustly investigated. Other drugs are being used on very limited evidence.

Increased fetal lung T2 signal is not due to increasing surfactant concentration: an in vitro T2 mapping analysis

OBJECT

The aim of this study was to perform in vitro T2 mapping of serial dilutions of pharmaceutical surfactant.

MATERIALS AND METHODS

Magnetic resonance imaging. Magnetic resonance scanning was performed on serial dilutions of surfactant on large bore clinical magnets at a field strength of 1.5 T Philips and 3.0 T (Achieva TX, Philips Healthcare, the Netherlands).

RESULTS

The curves demonstrate a small increasing trend between surfactant concentration and R2 (shortened T2's), with a 7.3% increase in R2 for each doubling of surfactant concentration (95% confidence interval: 6.1-8.6%, p < 0.001).

CONCLUSIONS

The increasing lung/liver T2 signal ratio seen in fetal lungs with increasing gestational age is not due to increasing surfactant concentration. © 2016 John Wiley & Sons, Ltd.

Evolution of surfactant therapy for respiratory distress syndrome: past, present, and future

Respiratory distress syndrome (RDS) due to surfactant deficiency is the most common cause of respiratory failure in preterm infants. Tremendous progress has been made since the original description that surfactant deficiency is the major cause of RDS. Surfactant therapy has been extensively studied in preterm infants and has been shown to significantly decrease air leaks and neonatal and infant mortality. Synthetic and animal-derived surfactants from bovine as well as porcine origin have been evaluated in randomized controlled trials. Animal-derived surfactants generally result in faster weaning of respiratory support, shorter duration of invasive ventilation, and decreased mortality when compared to first- or second-generation of synthetic surfactants, but some of the second-generation synthetic surfactants are at least not inferior to the animal-derived surfactants. Using a higher initial dose of porcine derived surfactant may provide better outcomes when compared with using lower doses of bovine surfactants, likely, due to compositional difference and/or the dose. Third-generation synthetic surfactant containing peptide analogs of surfactant protein B and C are currently being studied. Less invasive intra-tracheal surfactant administration techniques in spontaneously breathing neonate receiving noninvasive ventilator support are also being evaluated. In the present era, prophylactic surfactant is not recommended as it may increase the risk of lung injury or death. In the future, surfactants may be used as vector to deliver steroids, or used in combination with molecules, such as, recombinant Club Cell Protein-10 (rhCC-10) to improve pulmonary outcomes. Also, noninvasive surfactant administration techniques, such as aerosolization or atomization of surfactant may play a greater role in the future.

Surfactant for Respiratory Distress Syndrome: New Ideas on a Familiar Drug with Innovative Applications

In the last 4 decades, advances in neonatology have led to a significant increase in the survival of preterm infants. One of the biggest advances was the introduction of surfactant replacement therapy for the treatment of respiratory distress syndrome. This is the main cause of respiratory insufficiency in preterm infants and is one of the major causes of perinatal morbidity and mortality. Surfactant replacement therapy is already a well-investigated and established therapy in neonatology. However, surfactant replacement therapy has progressed and been refined over recent decades, especially with the increasing care for preterm infants born before 26 weeks' gestational age and the recent clinical focus on avoiding mechanical ventilation. Clinical evidence is evolving on new types of surfactant, surfactant dosages, co-medication given before, with, or after surfactant replacement, and new technical advances regarding the mode of administration.

Noninvasive Respiratory Support During Transportation

To minimize ventilator-associated lung injury in neonates, use of noninvasive (NIV) respiratory support has markedly increased over the past decade, especially in neonates younger than 28-weeks gestational age and 1250 g. Previously, neonates with respiratory failure who required anything greater than an oxyhood or low-flow nasal cannula were intubated for transport. This increased use has required transport teams to develop or incorporate a new set of support tools to minimize lung injury. This article reviews the various modes of NIV used during neonatal transport, important patient selection criteria, appropriate assessment, and the associated risks and benefits.

Design of Surfactant Protein B Peptide Mimics Based on the Saposin Fold for Synthetic Lung Surfactants

Surfactant protein (SP)-B is a 79-residue polypeptide crucial for the biophysical and physiological function of endogenous lung surfactant. SP-B is a member of the saposin or saposin-like proteins (SAPLIP) family of proteins that share an overall three-dimensional folding pattern based on secondary structures and disulfide connectivity and exhibit a wide diversity of biological functions. Here, we review the synthesis, molecular biophysics and activity of synthetic analogs of saposin proteins designed to mimic those interactions of the parent proteins with lipids that enhance interfacial activity. Saposin proteins generally interact with target lipids as either monomers or multimers via well-defined amphipathic helices, flexible hinge domains, and insertion sequences. Based on the known 3D-structural motif for the saposin family, we show how bioengineering techniques may be used to develop minimal peptide constructs that maintain desirable structural properties and activities in biomedical applications. One important application is the molecular design, synthesis and activity of Saposin mimics based on the SP-B structure. Synthetic lung surfactants containing active SP-B analogs may be potentially useful in treating diseases of surfactant deficiency or dysfunction including the neonatal respiratory distress syndrome and acute lung injury/acute respiratory distress syndrome.

Synthetic lung surfactants containing SP-B and SP-C peptides plus novel phospholipase-resistant lipids or glycerophospholipids

Background

This study examines the biophysical and preclinical pulmonary activity of synthetic lung surfactants containing novel phospholipase-resistant phosphonolipids or synthetic glycerophospholipids combined with Super Mini-B (S-MB) DATK and/or SP-Css ion-lock 1 peptides that replicate the functional biophysics of surfactant proteins (SP)-B and SP-C. Phospholipase-resistant phosphonolipids used in synthetic surfactants are DEPN-8 and PG-1, molecular analogs of dipalmitoyl phosphatidylcholine (DPPC) and palmitoyl-oleoyl phosphatidylglycerol (POPG), while glycerophospholipids used are active lipid components of native surfactant (DPPC:POPC:POPG 5:3:2 by weight). The objective of the work is to test whether these novel lipid/peptide synthetic surfactants have favorable preclinical activity (biophysical, pulmonary) for therapeutic use in reversing surfactant deficiency or dysfunction in lung disease or injury.

Methods

Surface activity of synthetic lipid/peptide surfactants was assessed in vitro at 37 °C by measuring adsorption in a stirred subphase apparatus and dynamic surface tension lowering in pulsating and captive bubble surfactometers. Shear viscosity was measured as a function of shear rate on a Wells-Brookfield micro-viscometer. In vivo pulmonary activity was determined by measuring lung function (arterial oxygenation, dynamic lung compliance) in ventilated rats and rabbits with surfactant deficiency/dysfunction induced by saline lavage to lower arterial PO₂ to <100 mmHg, consistent with clinical acute respiratory distress syndrome (ARDS).

Results

Synthetic surfactants containing 5:3:2 DPPC:POPC:POPG or 9:1 DEPN-8:PG-1 combined with 3% (by wt) of S-MB DATK, 3% SP-Css ion-lock 1, or 1.5% each of both peptides all adsorbed rapidly to low equilibrium surface tensions and also reduced surface tension to ≤1 mN/m under dynamic compression at 37 °C. However, dual-peptide surfactants containing 1.5% S-MB DATK + 1.5% SP-Css ion-lock 1 combined with 9:1 DEPN-8:PG-1 or 5:3:2 DPPC:POPC:POPG had the greatest in vivo activity in improving arterial oxygenation and dynamic lung compliance in ventilated animals with ARDS. Saline dispersions of these dual-peptide synthetic surfactants were also found to have shear viscosities comparable to or below those of current animal-derived surfactant drugs, supporting their potential ease of deliverability by instillation in future clinical applications.

Discussion

Our findings support the potential of dual-peptide synthetic lipid/peptide surfactants containing S-MB DATK + SP-Css ion-lock 1 for treating diseases of surfactant deficiency or dysfunction. Moreover, phospholipase-resistant dual-peptide surfactants containing DEPN-8/PG-1 may have particular applications in treating direct forms of ARDS where endogenous phospholipases are present in the lungs.

High Flow Nasal Cannulae versus Nasal Continuous Positive Airway Pressure in Neonates with Respiratory Distress Syndrome Managed with INSURE Method: A Randomized Clinical Trial

BACKGROUND

In recent years, various noninvasive respiratory support (NRS) of ventilation has been provided more in neonates. The aim of this study was to compare the effect of HFNC with NCPAP in post-extubation of preterm infants with RDS after INSURE method (intubation, surfactant, extubation).

METHODS

A total of 54 preterm infants with RDS (respiratory distress syndrome) were enrolled in this study. Using a randomized sequence, they were assigned into two groups after INSURE method. The first group received HFNC while the second group received NCPAP for respiratory support after extubation. A comparison was made between these two groups by the rate of reintubation, air leak syndrome, duration of oxygen therapy, hospitalization, the rate of bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP), and mortality. Data were analyzed by using the SPSS version 18 software. The statistical analyses included Student's t-test for continuous data and compared proportions using Chi-squared test and Fisher's exact test for categorical data.

RESULT

The rate of reintubation was higher in the HFNC compared with the NCPAP group. The rate of either IVH or ROP had no significant differences between the two groups. In addition, duration of oxygen requirement and hospitalization were not statistically different. There was no case of BPD or mortality among these patients.

CONCLUSION

This study showed that preterm infants with RDS could manage post-extubation after INSURE method with either NCPAP or HFNC. However, in this single-center study, the rate of reintubation was higher in the HFNC group while further multicenter study might be assigned. Trial Registration Number: IRCT201201228800N1.

A Case of Pulmonary Interstitial Emphysema Treated by Percutaneous Catheter Insertion in Extremely Low Birth Weight Infant

The pulmonary interstitial emphysema (PIE) is a life-threatening illness in premature infants with mechanical ventilation. While most are managed conservatively, decompression would be necessary. Here, we report the first case of PIE treated by percutaneous catheter insertion in an extremely low birth weight (ELBW) infant in Korea. The patient, born with 660 g in 23+2 weeks of gestation, showed PIE in left lower lung on postnatal day 12. Percutaneous catheter insertion was performed on postnatal day 25. The size of PIE decreased, but didn't disappear completely. On postnatal day 42, we exchanged catheter and inserted additional catheter in pleural space. However, sudden desaturation and pneumothorax occurred on postnatal day 44. We changed catheter in pleural space, and pneumothorax and PIE improved. Finally, we successfully removed catheters, and weaned patient out. As in our case, percutaneous catheter insertion would be a useful option for ELBW infants with PIE.

Metabolic Functions of the Lung, Disorders and Associated Pathologies

The primary function of the lungs is gas exchange. Approximately 400 million years ago, the Earth's atmosphere gained enough oxygen in the gas phase for the animals that emerged from the sea to breathe air. The first lungs were merely primitive air sacs with a few vessels in the walls that served as accessory organs of gas exchange to supplement the gills. Eons later, as animals grew accustomed to a solely terrestrial life, the lungs became highly compartmentalized to provide the vast air-blood surface necessary for O2 uptake and CO2 elimination, and a respiratory control system was developed to regulate breathing in accordance with metabolic demands and other needs. With the evolution and phylogenetic development, lungs were taking a variety of other specialized functions to maintain homeostasis, which we will call the non-respiratory functions of the lung and that often, and by mistake, are believed to have little or no connection with the replacement gas. In this review, we focus on the metabolic functions of the lung, perhaps the least known, and mainly, in the lipid metabolism and blood-adult lung vascular endothelium interaction. When these functions are altered, respiratory disorders or diseases appear, which are discussed concisely, emphasizing how they impact the most important function of the lungs: external respiration.

Prevention and management of bronchopulmonary dysplasia: Lessons learned from the neonatal research network

Despite remarkable improvements in survival of extremely premature infants, the burden of BPD among survivors remains a frustrating problem for parents and caregivers. Advances, such as antenatal steroids and surfactant replacement, which have dramatically improved survival, have not reduced BPD among survivors. Other advances that have significantly improved the combined outcome of death or BPD, such as vitamin A and avoidance of mechanical ventilation, have had smaller magnitude effects on the outcome of BPD alone. Postnatal steroids have a clear beneficial effect on BPD, but the optimal preparation, dose, and timing for maximizing benefit and minimizing harm have yet to be determined. This persistent burden of BPD among the most immature survivors remains a challenge for the NRN and other researchers in neonatal medicine.

Stability of an amphipathic helix-hairpin surfactant peptide in liposomes

Surfactant protein B (SP-B; 79 residues) is a member of the saposin superfamily and plays a pivotal role in lung function. The N- and C-terminal regions of SP-B, cross-linked by two disulfides, were theoretically predicted to fold as charged amphipathic helices, suggesting participation in surfactant activities. Previous studies with oxidized Super Mini-B (SMB), a construct based on the N- and C-regions of SP-B (i.e., residues 1-25 and 63-78) joined with a designer turn (-PKGG-) and two disulfides, indicated that freshly prepared SMB in lipids folded as a surface active, α-helix-hairpin. Because other peptides modeled on α-helical SP domains lost helicity and surfactant activity on storage, experiments were here performed on oxidized SMB in surfactant liposomes stored at ~2-8°C for ≤5.5years. Captive bubble surfactometry confirmed low minimum surface tensions for fresh and stored SMB preparations. FTIR spectroscopy of fresh and stored SMB formulations showed secondary structures compatible with the peptide folding as α-helix-hairpin. A homology (I-TASSER) model of oxidized SMB demonstrated a globular protein, exhibiting a core of hydrophobic residues and a surface of polar residues. Since mass spectroscopy indicated that the disulfides were maintained on storage, the stability of SMB may be partly due to the disulfides bringing the N- and C-α-helices closer. Mass spectroscopy of stored SMB preparations showed some methionine oxidation, and also partial deacylation of surfactant phospholipids to form lyso-derivatives. However, the stable conformation and activity of stored SMB surfactant suggest that the active helix-hairpin resists these chemical changes which otherwise may lead to surfactant inhibition.

Structural and transcriptomic response to antenatal corticosteroids in an Erk3-null mouse model of respiratory distress

BACKGROUND

Neonatal respiratory distress syndrome in preterm infants is a leading cause of neonatal death. Pulmonary insufficiency-related infant mortality rates have improved with antenatal glucocorticoid treatment and neonatal surfactant replacement. However, the mechanism of glucocorticoid-promoted fetal lung maturation is not understood fully, despite decades of clinical use. We previously have shown that genetic deletion of Erk3 in mice results in growth restriction, cyanosis, and early neonatal lethality because of pulmonary immaturity and respiratory distress. Recently, we demonstrated that the addition of postnatal surfactant administration to antenatal dexamethasone treatment resulted in enhanced survival of neonatal Erk3-null mice.

OBJECTIVE

To better understand the molecular underpinnings of corticosteroid-mediated lung maturation, we used high-throughput transcriptomic and high-resolution morphologic analysis of the murine fetal lung. We sought to examine the alterations in fetal lung structure and function that are associated with neonatal respiratory distress and antenatal glucocorticoid treatment.

STUDY DESIGN

Dexamethasone (0.4 mg/kg) or saline solution was administered to pregnant dams on embryonic days 16.5 and 17.5. Fetal lungs were collected and analyzed by microCT and RNA-seq for differential gene expression and pathway interactions with genotype and treatment. Results from transcriptomic analysis guided further investigation of candidate genes with the use of immunostaining in murine and human fetal lung tissue.

RESULTS

Erk3(-/-) mice exhibited atelectasis with decreased overall porosity and saccular space relative to wild type, which was ameliorated by glucocorticoid treatment. Of 596 differentially expressed genes (q < 0.05) that were detected by RNA-seq, pathway analysis revealed 36 genes (q < 0.05) interacting with dexamethasone, several with roles in lung development, which included corticotropin-releasing hormone and surfactant protein B. Corticotropin-releasing hormone protein was detected in wild-type and Erk3(-/-) lungs at E14.5, with significantly temporally altered expression through embryonic day 18.5. Antenatal dexamethasone attenuated corticotropin-releasing hormone at embryonic day 18.5 in both wild-type and Erk3(-/-) lungs (0.56-fold and 0.67-fold; P < .001). Wild type mice responded to glucocorticoid administration with increased pulmonary surfactant protein B (P = .003). In contrast, dexamethasone treatment in Erk3(-/-) mice resulted in decreased surfactant protein B (P = .012). In human validation studies, we confirmed that corticotropin-releasing hormone protein is present in the fetal lung at 18 weeks of gestation and increases in expression with progression towards viability (22 weeks of gestation; P < .01).

CONCLUSION

Characterization of whole transcriptome gene expression revealed glucocorticoid-mediated regulation of corticotropin-releasing hormone and surfactant protein B via Erk3-independent and -dependent mechanisms, respectively. We demonstrated for the first time the expression and temporal regulation of corticotropin-releasing hormone protein in midtrimester human fetal lung. This unique model allows the effects of corticosteroids on fetal pulmonary morphologic condition to be distinguished from functional gene pathway regulation. These findings implicate Erk3 as a potentially important molecular mediator of antenatal glucocorticoid action in promoting surfactant protein production in the preterm neonatal lung and expanding our understanding of key mechanisms of clinical therapy to improve neonatal survival.