Perinatal factors in neonatal and pediatric lung diseases

Acute respiratory compromise in the NICU

Acute respiratory compromise (ARC) is a significant and frequent emergency in the Neonatal Intensive Care Unit (NICU), characterized by absent, agonal, or inadequate respiration that necessitates an immediate response. The primary etiologies of ARC in neonates can be categorized into upper and lower airway issues, disordered control of breathing, and lung tissue disease. ARC events are particularly dangerous as they compromise oxygen delivery and carbon dioxide removal, potentially leading to cardiopulmonary arrest. Approximately 1 % of NICU admissions experience cardiopulmonary arrest, and ARC is the primary cause of most events. This article provides a comprehensive review of the etiologies of ARC, including anatomical abnormalities, syndromic disorders, airway obstruction, and pulmonary diseases such as bronchopulmonary dysplasia and pneumonia. Management strategies include the use of continuous positive airway pressure, positive pressure ventilation, and advanced interventions like extracorporeal membrane oxygenation (ECMO) in cases of severe respiratory distress. Additionally, quality improvement initiatives aimed at reducing incidents such as unplanned extubations (UE) are discussed, along with emergency responses to ARC, which often require multidisciplinary collaboration and advanced airway management. The article emphasizes the importance of preparedness, training, and structured emergency protocols to ARC in the NICU to optimize patient care.

Long-term lung function follow-up of preterm infants less than 32 weeks of gestational age

BACKGROUND

Preterm infants, particularly those with bronchopulmonary dysplasia (BPD), are at risk of lung development problems. Over the last decades, lung protective strategies have been used, decreasing the risk of chronic lung disease.

OBJECTIVE

To evaluate the pulmonary function test (PFT) of preterm infants born after the introduction of lung protective strategies and to assess perinatal determinants of impaired lung function in this population.

METHODS

A prospective, observational, single-center study was conducted in the neonatal unit of a high-complexity hospital. The study included newborns with less than 32 weeks gestational age born between 2012 and 2014, who were followed up until they reach school age. For the main outcome, two groups were stablished: no BPD or grade 1 BPD (no BPD/1) and grade 2 or 3 BPD (BPD 2/3).

RESULTS

Out of 327 patients, 116 were included. BPD was diagnosed in 49.1% (47), with 50.9% (29) classified as grade 1, 35.1% (20) as grade 2, and 14.0% (8) as grade 3. Mean age at PFT was 8.59 years (SD 0.90). Mean FEV1% was 95.36% (SD 13.21) and FEV1 z-score -0.36 (SD 1.12); FVC% 97.53% (SD 12.59) and FVC z-score -0.20 (SD 1.06); FEV1/FVC ratio 85.84% (SD 8.34) and z-score -0.24 (SD 1.34). When comparing patients with no BPD/1 and BPD 2/3, we observed differences in all pulmonary function parameters, which persisted after adjusting for gestational age. No differences in PFT were observed between patients without BPD and those with grade 1 BPD. Most patients (76.7%, 89) had normal spirometry pattern, with obstructive pattern observed in 12.9% (15), restrictive pattern in 9.5% (11), and mixed pattern in 0.9% (1) of patients.

CONCLUSION

Preterm infants with BPD 2/3 showed a decrease in all pulmonary function parameters compared to preterm infants with no BPD/1; an effect that was independent of gestational age. Among patients with BPD who had an altered PFT pattern, the most common pattern was obstructive, followed by restrictive and then, mixed.

Exogenous hydrogen sulfide attenuates hyperoxia effects on neonatal mouse airways

Supplemental O2 remains a necessary intervention for many premature infants (<34 wk gestation). Even moderate hyperoxia (<60% O2) poses a risk for subsequent airway disease, thereby predisposing premature infants to pediatric asthma involving chronic inflammation, airway hyperresponsiveness (AHR), airway remodeling, and airflow obstruction. Moderate hyperoxia promotes AHR via effects on airway smooth muscle (ASM), a cell type that also contributes to impaired bronchodilation and remodeling (proliferation, altered extracellular matrix). Understanding mechanisms by which O2 initiates long-term airway changes in prematurity is critical for therapeutic advancements for wheezing disorders and asthma in babies and children. Immature or dysfunctional antioxidant systems in the underdeveloped lungs of premature infants thereby heightens susceptibility to oxidative stress from O2. The novel gasotransmitter hydrogen sulfide (H2S) is involved in antioxidant defense and has vasodilatory effects with oxidative stress. We previously showed that exogenous H2S exhibits bronchodilatory effects in human developing airway in the context of hyperoxia exposure. Here, we proposed that exogenous H2S would attenuate effects of O2 on airway contractility, thickness, and remodeling in mice exposed to hyperoxia during the neonatal period. Using functional [flexiVent; precision-cut lung slices (PCLS)] and structural (histology; immunofluorescence) analyses, we show that H2S donors mitigate the effects of O2 on developing airway structure and function, with moderate O2 and H2S effects on developing mouse airways showing a sex difference. Our study demonstrates the potential applicability of low-dose H2S toward alleviating the detrimental effects of hyperoxia on the premature lung.NEW & NOTEWORTHY Chronic airway disease is a short- and long-term consequence of premature birth. Understanding effects of O2 exposure during the perinatal period is key to identify targetable mechanisms that initiate and sustain adverse airway changes. Our findings show a beneficial effect of exogenous H2S on developing mouse airway structure and function with notable sex differences. H2S donors alleviate effects of O2 on airway hyperreactivity, contractility, airway smooth muscle thickness, and extracellular matrix deposition.

Implications of maternal vitamin D administration for the neonatal respiratory distress syndrome: A randomized clinical trial

BACKGROUND

Vitamin D deficiency has been suggested to be a risk factor for neonatal respiratory distress syndrome (RDS). This study aimed to evaluate the effect of 25 (OH) D administrations in pregnant women with findings of preterm labor on the incidence of RDS in their preterm neonates.

MATERIALS AND METHODS

A randomized controlled clinical trial was conducted on pregnant mothers with gestational age (GA) of less than 34 weeks at risk of preterm delivery. 175 subjects were randomly assigned into two groups, including intervention (intramuscular injection of 50,000 units of 25(OH) D during 72 hours before delivery) and control (no injections). Serum concentrations of 25(OH) D were measured shortly after birth in both mothers and neonates. Then, clinical and laboratory results of mothers and their offspring were recorded (in a checklist). Short-term outcomes and the need for respiratory support were also assessed. Data were analyzed by independent t-test, Mann-Whitney U test, Fisher's exact test, and chi-square test.

RESULTS

Even though gestational age, birth weight, delivery method, and serum vitamin D levels are consistent among both groups, 45% of neonates in the control group and 20% in the intervention group developed respiratory distress syndrome (P = 0.05). The mean 25(OH) D level in neonates was 17.7±10.5 and 19.29±9.94 ng/mL in the intervention and control groups, respectively (P > 0.05).

CONCLUSION

A single dose of 50,000 units of intramuscular 25(OH)D in pregnant women at risk of preterm labor can lower the risk of RDS in the infant.

Dose-dependent impact of human milk feeding on tidal breathing flow-volume loop parameters across the first 2 years of life in extremely low-birth-weight infants: a cohort study

The purpose of this study is to test the hypothesis that higher consumption of human milk (HM) in preterm infants with birth weight (BW) <1000 g is associated with improved lung function in a dose-dependent manner over the first 2 years of corrected age (CA). This retrospective study at an academic medical center included infants with BW <1000g. They had lung function assessment by the tidal breathing flow-volume loop (TBFVL) follow-up visits at 0-3-, 3-6-, 6-12-, 12-18-, and 18-24-month CA. One hundred eighty infants were included in the study with a mean (SD) gestational age 26.5 (1.90) weeks and BW 772.4 (147.0) g, 50% were female, and 60% developed BPD. 62.8% of infants received HM during the NICU stay. According to a general linear model (including GA, being small for GA (SGA), sex, human milk percentage, sepsis, and BPD), on average, each week of GA resulted in a higher tPTEF/tE of 1.24 (p = 0.039) and being SGA in a lower tPTEF/tE of 5.75 (p = 0.013) at 0-3-month CA. A higher percentage of human milk out of the total enteral intake was associated with better tPTEF/tE z-scores at 0-3 months (p = 0.004) and 18-24 months of CA (p = 0.041). BPD diagnosis was associated with a relevantly worse tPTEF/tE z-score at 6-12 months of CA (p = 0.003).

CONCLUSION

Preterm infants with higher consumption of HM had significantly less airway obstruction across the first 2 years, suggesting that human milk may contribute in a dose-dependent manner to improve lung function in early childhood in former preterm infants born ELBW.

WHAT IS KNOWN

• Human milk feeding reduces the risk of prematurity-related morbidities, including necrotizing enterocolitis, sepsis, lower respiratory tract infections, and BPD. Both exclusive and partial human milk feeding appear to be associated with a lower risk of BPD in preterm infants.

WHAT IS NEW

• This cohort study of 180 preterm infants with birth weight < 1000 g found that exposure to human milk during hospitalization improves airway obstruction markers tPTEF/tE z-score over the first 2 years of corrected age in a dose-dependent manner.

Bronchodilator-responsive bronchiolar obstruction in term neonates: a case series

BACKGROUND

Bronchiolar obstruction, which causes airway obstruction in hyperresponsive airways, often results from the contraction of the airway's smooth muscles, increased viscid mucous secretions, and mucosal oedema consequent upon a reduced cyclic 3,5-adenosine monophosphate (c-AMP). These processes respond to bronchodilators. The six cases presented to us, in Edward Francis Small Teaching Hospital (EFSTH), Banjul, The Gambia, in the newborn period with clinical features suggesting obstruction with airway reactivity with response to bronchodilator treatment are presented here. Our capacity-limited literature search did not show any such report in neonates. This report highlights the need for this condition to be sought in neonates, medically managed in resource-poor countries without resorting to high-cost equipment use, and for its possible future classification.

CASE PRESENTATION

We report six cases of Gambian neonates consisting of four males and two females ages 2-27 days who presented to us with histories of fast breathing of a few hours duration and expiratory respiratory distress. All were term babies with rhonchi and demonstrable prolonged expiration with terminal effort. They all had a diagnosis of hyperreactive airway disease with bronchiolar obstruction. Five cases were first-time wheezers, while one was a recurrence. All were eventually treated with bronchodilators and steroids with good results. The median duration for resolution of most symptoms with treatment was two days, with a range of 1-5 days.

CONCLUSION

Clinically determined bronchiolar obstructions in term neonates can be relieved with bronchodilators and steroids, and this treatment modality, if employed where the pathological process can be established, can reduce the demand on scarce resources in resource-poor countries.

Oxygen and mechanical stretch in the developing lung: risk factors for neonatal and pediatric lung disease

Chronic airway diseases, such as wheezing and asthma, remain significant sources of morbidity and mortality in the pediatric population. This is especially true for preterm infants who are impacted both by immature pulmonary development as well as disproportionate exposure to perinatal insults that may increase the risk of developing airway disease. Chronic pediatric airway disease is characterized by alterations in airway structure (remodeling) and function (increased airway hyperresponsiveness), similar to adult asthma. One of the most common perinatal risk factors for development of airway disease is respiratory support in the form of supplemental oxygen, mechanical ventilation, and/or CPAP. While clinical practice currently seeks to minimize oxygen exposure to decrease the risk of bronchopulmonary dysplasia (BPD), there is mounting evidence that lower levels of oxygen may carry risk for development of chronic airway, rather than alveolar disease. In addition, stretch exposure due to mechanical ventilation or CPAP may also play a role in development of chronic airway disease. Here, we summarize the current knowledge of the impact of perinatal oxygen and mechanical respiratory support on the development of chronic pediatric lung disease, with particular focus on pediatric airway disease. We further highlight mechanisms that could be explored as potential targets for novel therapies in the pediatric population.

A Modern Look at the Development of Intrauterine Pneumonia in Premature Newborns: Literature Review

Infectious diseases such as malaria, pneumonia, diarrhea and preventable neonatal diseases are common causes of death in children. Globally, neonatal mortality is 44% (2.9 million) annually, with up to 50% of babies dying within the first day of life. Pneumonia kills between 750000 and 1.2 million infants in the neonatal period each year in developing countries. Premature birth, pneumonia, and labor complications are common causes of neonatal mortality. The objective of the study is to present the general characteristics of congenital pneumonia, vitamin D deficiency and micronutrient deficiencies in premature infants. To date, numerous studies confirm the relationship between the inadequate supply of the body with macro- and microelements and the development of diseases of varying severity, including metabolic disorders. Based on this, primary screening, aimed at identifying metabolic disorders of macro- and microelements and further drug correction, should become the main concept for the management of patients in modern times.

Probability of successful inhaled corticosteroids cessation in preschool wheezers: a predictive score

Nearly all asthma predictive tools estimate the future risk of asthma development. However, there is no tool to predict the probability of successful ICS cessation at an early age. Therefore, we aimed to determine the predictors of successful ICS cessation in preschool wheezers, and developed a simple predictive tool for clinical practice. This was a retrospective cohort study involving preschool wheezers who had undergone an ICS therapeutic trial during 2015-2020 at the University Hospital, Southern, Thailand. A predictive scoring system was developed using a nomogram to estimate the probability of successful ICS cessation. We calculated area under ROC curve and used a calibration plot for assessing the tool's performance. A total of 131 medical records were eligible for analysis. Most of the participants were male (68.9%). More than half of the preschool wheezers had successful ICS cessation after an initial therapeutic trial regimen. The predictors of less successful ICS cessation were perinatal oxygen use [OR 0.10 (0.01, 0.70), P = 0.02], allergic rhinitis [OR 0.20 (0.08, 0.56), P = 0.002], blood eosinophil count > 500 cell/mm³ [OR 0.20 (0.06, 0.67), P = 0.008], and previous ICS use > 6 months [OR 0.30 (0.09, 0.72), P = 0.009].

CONCLUSIONS

Predictors of less successful ICS cessation were the following: perinatal oxygen use, allergic rhinitis, blood eosinophil count > 500 cell/mm³, and previous ICS use > 6 months. A simple predictive score developed in this study may help general practitioners to be more confident in making a decision regarding the discontinuation of ICS after initial therapeutic trials.

WHAT IS KNOWN

• Early allergic sensitization is associated with reduced chances of inhaled corticosteroid cessation at school age. • Prolonged ICS is associated with the emergence of adverse effect and discontinuing too early can result in recurrence symptoms.

WHAT IS NEW

• Requirement of oxygen support within 7 days after birth in term neonate is a postnatal factor associated with less successful ICS cessation. • We propose a simple predictive tool with easily available clinical parameters (perinatal oxygen use, allergic rhinitis, blood eosinophil count, parental asthma history, and duration of previous ICS use) to determine the timing of inhalational corticosteroid cessation in preschool wheezers.

Clinical characteristics of recurrent pneumonia in children with or without underlying diseases

BACKGROUND

Recurrent pneumonia is uncommon in children and few studies investigate the clinical impact of underlying diseases on this issue. This study aimed to explore the difference in clinical manifestations, pathogens, and prognosis of recurrent pneumonia in children with or without underlying diseases.

METHODS

We conducted a retrospective study of pediatric recurrent pneumonia from 2007 to 2019 in National Taiwan University Hospital. Patients under the age of 18 who had two or more episodes of pneumonia in a year were included, and the minimum interval of two pneumonia episodes was more than one month. Aspiration pneumonia was excluded. Demographic and clinical characteristics of patients were collected and compared.

RESULTS

Among 8508 children with pneumonia, 802 (9.4%) of them had recurrent pneumonia. Among these 802 patients, 655 (81.7%) had underlying diseases including neurological disorders (N = 252, 38.5%), allergy (N = 211, 32.2%), and cardiovascular diseases (N = 193, 29.5%). Children without underlying diseases had more viral bronchopneumonia (p < 0.001). Children with underlying diseases were more likely to acquire Staphylococcus aureus (p = 0.001), and gram-negative bacteriae, more pneumonia episodes (3 vs 2, p < 0.001), a longer hospital stay (median: 7 vs. 4 days, p < 0.001), a higher ICU rate (28.8% vs 3.59%, p < 0.001), and a higher case-fatality rate (5.19% vs 0%, p < 0.001) than those without underlying diseases.

CONCLUSION

Children with underlying diseases, prone to have recurrent pneumonia and more susceptible to resistant microorganisms, had more severe diseases and poorer clinical outcomes. Therefore, more attention may be paid on clinical severity and the therapeutic plan.

Cigarette Smoke Exposure, Pediatric Lung Disease, and COVID-19

The detrimental effects of tobacco exposure on children's health are well known. Nonetheless, the prevalence of secondhand or direct cigarette smoke exposure (CSE) in the pediatric population has not significantly decreased over time. On the contrary, the rapid incline in use of e-cigarettes among adolescents has evoked public health concerns since increasing cases of vaping-induced acute lung injury have highlighted the potential harm of these new "smoking" devices. Two pediatric populations are especially vulnerable to the detrimental effects of cigarette smoke. The first group is former premature infants whose risk is elevated both due to their prematurity as well as other risk factors such as oxygen and mechanical ventilation to which they are disproportionately exposed. The second group is children and adolescents with chronic respiratory diseases, in particular asthma and other wheezing disorders. Coronavirus disease 2019 (COVID-19) is a spectrum of diseases caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has spread worldwide over the last year. Here, respiratory symptoms ranging from mild to acute respiratory distress syndrome (ARDS) are at the forefront of COVID-19 cases among adults, and cigarette smoking is associated with worse outcomes in this population, and cigarette smoking is associated with worse outcomes in this population. Interestingly, SARS-CoV-2 infection affects children differently in regard to infection susceptibility, disease manifestations, and complications. Although children carry and transmit the virus, the likelihood of symptomatic infection is low, and the rates of hospitalization and death are even lower when compared to the adult population. However, multisystem inflammatory syndrome is recognized as a serious consequence of SARS-CoV-2 infection in the pediatric population. In addition, recent data demonstrate specific clinical patterns in children infected with SARS-CoV-2 who develop multisystem inflammatory syndrome vs. severe COVID-19. In this review, we highlight the pulmonary effects of CSE in vulnerable pediatric populations in the context of the ongoing SARS-CoV-2 pandemic.

Calcium-Sensing Receptor Contributes to Hyperoxia Effects on Human Fetal Airway Smooth Muscle

Supplemental O₂ (hyperoxia), necessary for maintenance of oxygenation in premature infants, contributes to neonatal and pediatric airway diseases including asthma. Airway smooth muscle (ASM) is a key resident cell type, responding to hyperoxia with increased contractility and remodeling [proliferation, extracellular matrix (ECM) production], making the mechanisms underlying hyperoxia effects on ASM significant. Recognizing that fetal lungs experience a higher extracellular Ca²⁺ ([Ca²⁺]_o) environment, we previously reported that the calcium sensing receptor (CaSR) is expressed and functional in human fetal ASM (fASM). In this study, using fASM cells from 18 to 22 week human fetal lungs, we tested the hypothesis that CaSR contributes to hyperoxia effects on developing ASM. Moderate hyperoxia (50% O₂) increased fASM CaSR expression. Fluorescence [Ca²⁺]_i imaging showed hyperoxia increased [Ca²⁺]_i responses to histamine that was more sensitive to altered [Ca²⁺]_o, and promoted IP₃ induced intracellular Ca²⁺ release and store-operated Ca²⁺ entry: effects blunted by the calcilytic NPS2143. Hyperoxia did not significantly increase mitochondrial calcium which was regulated by CaSR irrespective of oxygen levels. Separately, fASM cell proliferation and ECM deposition (collagens but not fibronectin) showed sensitivity to [Ca²⁺]_o that was enhanced by hyperoxia, but blunted by NPS2143. Effects of hyperoxia involved p42/44 ERK via CaSR and HIF1α. These results demonstrate functional CaSR in developing ASM that contributes to hyperoxia-induced contractility and remodeling that may be relevant to perinatal airway disease.

Understanding hydrogen sulfide signaling in neonatal airway disease

INTRODUCTION

Airway dysfunction leading to chronic lung disease is a common consequence of premature birth and mechanisms responsible for early and progressive airway remodeling are not completely understood. Current therapeutic options are only partially effective in reducing the burden of neonatal airway disease and premature decline of lung function. Gasotransmitter hydrogen sulfide (H2S) has been recently recognized for its therapeutic potential in lung diseases.

AREAS COVERED

Contradictory to its well-known toxicity at high concentrations, H2S has been characterized to have anti-inflammatory, antioxidant, and antiapoptotic properties at physiological concentrations. In the respiratory system, endogenous H2S production participates in late lung development and exogenous H2S administration has a protective role in a variety of diseases such as acute lung injury and chronic pulmonary hypertension and fibrosis. Literature searches performed using NCBI PubMed without publication date limitations were used to construct this review, which highlights the dichotomous role of H2S in the lung, and explores its promising beneficial effects in lung diseases.

EXPERT OPINION

The emerging role of H2S in pathways involved in chronic lung disease of prematurity along with its recent use in animal models of BPD highlight H2S as a potential novel candidate in protecting lung function following preterm birth.

Cellular clocks in hyperoxia effects on [Ca2+]i regulation in developing human airway smooth muscle

Supplemental O2 (hyperoxia) is necessary for preterm infant survival but is associated with development of bronchial airway hyperreactivity and childhood asthma. Understanding early mechanisms that link hyperoxia to altered airway structure and function are key to developing advanced therapies. We previously showed that even moderate hyperoxia (50% O2) enhances intracellular calcium ([Ca2+]i) and proliferation of human fetal airway smooth muscle (fASM), thereby facilitating bronchoconstriction and remodeling. Here, we introduce cellular clock biology as a novel mechanism linking early oxygen exposure to airway biology. Peripheral, intracellular clocks are a network of transcription-translation feedback loops that produce circadian oscillations with downstream targets highly relevant to airway function and asthma. Premature infants suffer circadian disruption whereas entrainment strategies improve outcomes, highlighting the need to understand relationships between clocks and developing airways. We hypothesized that hyperoxia impacts clock function in fASM and that the clock can be leveraged to attenuate deleterious effects of O2 on the developing airway. We report that human fASM express core clock machinery (PER1, PER2, CRY1, ARNTL/BMAL1, CLOCK) that is responsive to dexamethasone (Dex) and altered by O2. Disruption of the clock via siRNA-mediated PER1 or ARNTL knockdown alters store-operated calcium entry (SOCE) and [Ca2+]i response to histamine in hyperoxia. Effects of O2 on [Ca2+]i are rescued by driving expression of clock proteins, via effects on the Ca2+ channels IP3R and Orai1. These data reveal a functional fASM clock that modulates [Ca2+]i regulation, particularly in hyperoxia. Harnessing clock biology may be a novel therapeutic consideration for neonatal airway diseases following prematurity.

Patterns of respiratory health services utilization from birth to 5 years of children who experienced adverse birth outcomes

Introduction

Adverse birth outcomes have important consequences for future lung health. We evaluated patterns of respiratory health services utilization in early childhood among children born preterm (PTB), small and large for gestational age at term (SGA and LGA, respectively), and appropriate-for-gestational age at term.

Materials and methods

We conducted a population-based retrospective cohort study using administrative health data of all singleton live births in Alberta, Canada between 2005–2010. Data on hospitalizations and emergency department (ED) visits from birth to 5 years were collected for asthma, bronchitis, bronchiolitis, croup, influenza, pneumonia, and other acute upper and lower respiratory tract infections (other URTI and other LRTI, respectively). Adjusted rate ratios were estimated for respiratory ED visits and hospitalizations for adverse birth outcomes using the appropriate-for-gestational age at term group as reference. Age-specific trajectories of total respiratory health services utilization rates for each group were estimated in Poisson models.

Results

A total of 293,764 episodes of respiratory care from 206,994 children were analyzed. Very PTB children had the highest rates of health services use for all respiratory conditions, particularly for asthma, pneumonia, and bronchiolitis hospitalizations. Moderate/late PTB children also had elevated ED visits and hospitalizations for all respiratory conditions. Children born SGA showed high rates of ED visits for other LRTI, and of hospitalizations for bronchitis, bronchiolitis, and other URTI. Children born LGA had high rates of croup and other URTI ED visits, and of bronchiolitis and bronchiolitis hospitalizations. Age-specific trajectories showed a decreasing trend in the rates of total respiratory health service utilization from birth to five years of age for all groups studied. Children born PTB and LGA at term significantly required more respiratory health services over time compared to the reference group.

Conclusion

Patterns of paediatric respiratory health services utilization vary according to gestational age and fetal growth.

Neurotrophin Regulation and Signaling in Airway Smooth Muscle

Structural and functional aspects of bronchial airways are key throughout life and play critical roles in diseases such as asthma. Asthma involves functional changes such as airway irritability and hyperreactivity, as well as structural changes such as enhanced cellular proliferation of airway smooth muscle (ASM), epithelium, and fibroblasts, and altered extracellular matrix (ECM) and fibrosis, all modulated by factors such as inflammation. There is now increasing recognition that disease maintenance following initial triggers involves a prominent role for resident nonimmune airway cells that secrete growth factors with pleiotropic autocrine and paracrine effects. The family of neurotrophins may be particularly relevant in this regard. Long recognized in the nervous system, classical neurotrophins such as brain-derived neurotrophic factor (BDNF) and nonclassical ligands such as glial-derived neurotrophic factor (GDNF) are now known to be expressed and functional in non-neuronal systems including lung. However, the sources, targets, regulation, and downstream effects are still under investigation. In this chapter, we discuss current state of knowledge and future directions regarding BDNF and GDNF in airway physiology and on pathophysiological contributions in asthma.

Hydrogen sulfide, oxygen, and calcium regulation in developing human airway smooth muscle

Preterm infants can develop airway hyperreactivity and impaired bronchodilation following supplemental O2 (hyperoxia) in early life, making it important to understand mechanisms of hyperoxia effects. Endogenous hydrogen sulfide (H2 S) has anti-inflammatory and vasodilatory effects with oxidative stress. There is little understanding of H2 S signaling in developing airways. We hypothesized that the endogenous H2 S system is detrimentally influenced by O2 and conversely H2 S signaling pathways can be leveraged to attenuate deleterious effects of O2 . Using human fetal airway smooth muscle (fASM) cells, we investigated baseline expression of endogenous H2 S machinery, and effects of exogenous H2 S donors NaHS and GYY4137 in the context of moderate hyperoxia, with intracellular calcium regulation as a readout of contractility. Biochemical pathways for endogenous H2 S generation and catabolism are present in fASM, and are differentially sensitive to O2 toward overall reduction in H2 S levels. H2 S donors have downstream effects of reducing [Ca2+ ]i responses to bronchoconstrictor agonist via blunted plasma membrane Ca2+ influx: effects blocked by O2 . However, such detrimental O2 effects are targetable by exogenous H2 S donors such as NaHS and GYY4137. These data provide novel information regarding the potential for H2 S to act as a bronchodilator in developing airways in the context of oxygen exposure.

Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring

OBJECTIVE

To examine maternal preexisting type 2 diabetes (T2D) and gestational diabetes mellitus (GDM) on risk of childhood asthma.

STUDY DESIGN

This retrospective birth cohort study included 97 554 singletons born in 2007-2011 within hospitals from a single integrated healthcare system. Children were prospectively followed from age 5 until December 31, 2017, using electronic medical records. Relative risks of childhood asthma associated with maternal diabetes in utero were estimated by hazard ratios using Cox regression adjusting for potential confounders.

RESULTS

There were 3119 children (3.2%) who were exposed to preexisting T2D and 9836 (10.1%) to GDM. Among mothers with GDM, 3380 (34.4%) were dispensed antidiabetic medication during pregnancy. During a median of 7.6 years (IQR, 6.3-9.0 years) after birth, 15 125 children (15.5%) were diagnosed with asthma after age 5. Maternal diabetes interacted with maternal asthma history to affect child's asthma risk (P = .05). Among children without maternal asthma (n = 89 487), the adjusted hazard ratios for childhood asthma were 1.21 (95% CI, 1.08-1.36; P < .001) for exposure to T2D, 1.12 (95% CI, 1.01-1.25; P = .04) for GDM requiring antidiabetic medications, and 1.01 (95% CI, 0.93-1.10; P = .82) for GDM not requiring medications compared with no diabetes during pregnancy. The corresponding hazard ratios were 1.53 (95% CI, 1.19-1.96; P < .001), 1.11 (95% CI, 0.65-1.46; P = .44), and 0.84 (95% CI, 0.66-1.08; P = .17) among children without maternal asthma (n = 8067). Gestational age at GDM diagnosis was not associated with childhood asthma (P = .27).

CONCLUSIONS

The risk of childhood asthma was predominately observed for exposure to preexisting T2D, small for GDM requiring medication, and not increased for GDM not requiring medication during pregnancy, compared with no diabetes during pregnancy.

Health gradients in emergency visits and hospitalisations for paediatric respiratory diseases: A population-based retrospective cohort study

BACKGROUND

Socio-economically deprived children face a disproportionate burden of respiratory diseases. The association between area-level material and social deprivation and emergency department (ED) visits and hospitalisations for paediatric respiratory diseases has not been explored.

OBJECTIVES

We evaluated health inequalities in emergency department (ED) visits and hospitalisations for paediatric respiratory diseases according to material and social deprivation indexes.

METHODS

This population-based retrospective cohort study deterministically linked birth, ED visits and hospitalisation data, and census-based, area-level deprivation indexes for all singleton children born in the province of Alberta, Canada, between 2005 and 2010 who had at least one recorded ED visit or hospitalisation for respiratory diseases in their first five years of life. We classified ED visits and hospitalisations for seven respiratory diseases by deprivation indexes. Concentration indexes (CInd) and area-level concentration curves measured health gradients across deprivation groups. Rate ratios (RR) evaluated associations between deprivation indexes and respiratory episodes of care.

RESULTS

The study cohort included 198 572 newborns. The highest CInd were found in ED visits for other acute lower respiratory tract infections (oLRTI; CInd -0.22, 95% confidence interval [CI] -0.32, -0.12) and bronchiolitis (CInd -0.21, 95% CI -0.29, -0.12), and for pneumonia hospitalisations (CInd -0.23, 95% CI -0.33, -0.13). Croup ED visits had a low inequality degree. Compared to social deprivation, the material deprivation index presented a more consistent health gradient of increased episodes of care with increasing deprivation. oLRTI ED visits (RR 2.60, 95% CI 2.34, 2.92) and pneumonia hospitalisations (RR 2.57, 95% CI 2.31, 2.86) presented the largest inequalities between the least and most materially deprived groups.

CONCLUSIONS

We found a concentration of ED visits and hospitalisations for paediatric respiratory diseases in the most deprived groups. However, health inequalities are present across the material and social deprivation spectrum. Compared to the social deprivation index, the material index presented clearer paediatric respiratory health gradients.

Hyperoxia-induced Cellular Senescence in Fetal Airway Smooth Muscle Cells

Supplemental O₂ (hyperoxia; 30-90% O₂) is a necessary intervention for premature infants, but it contributes to development of neonatal and pediatric asthma, necessitating better understanding of contributory mechanisms in hyperoxia-induced changes to airway structure and function. In adults, environmental stressors promote formation of senescent cells that secrete factors (senescence-associated secretory phenotype), which can be inflammatory and have paracrine effects that enhance chronic lung diseases. Hyperoxia-induced changes in airway structure and function are mediated in part by effects on airway smooth muscle (ASM). In the present study, using human fetal ASM cells as a model of prematurity, we ascertained the effects of clinically relevant moderate hyperoxia (40% O₂) on cellular senescence. Fetal ASM exposed to 40% O₂ for 7 days exhibited elevated concentrations of senescence-associated markers, including β-galactosidase; cell cycle checkpoint proteins p16, p21, and p-p53; and the DNA damage marker p-γH2A.X (phosphorylated γ-histone family member X). The combination of dasatinib and quercetin, compounds known to eliminate senescent cells (senolytics), reduced the number of hyperoxia-exposed β-galactosidase-, p21-, p16-, and p-γH2A.X-positive ASM cells. The senescence-associated secretory phenotype profile of hyperoxia-exposed cells included both profibrotic and proinflammatory mediators. Naive ASM exposed to media from hyperoxia-exposed senescent cells exhibited increased collagen and fibronectin and higher contractility. Our data show that induction of cellular senescence by hyperoxia leads to secretion of inflammatory factors and has a functional effect on naive ASM. Cellular senescence in the airway may thus contribute to pediatric airway disease in the context of sequelae of preterm birth.

Caveolin-1 scaffolding domain peptide prevents hyperoxia-induced airway remodeling in a neonatal mouse model

Reactive airway diseases are significant sources of pulmonary morbidity in neonatal and pediatric patients. Supplemental oxygen exposure in premature infants contributes to airway diseases such as asthma and promotes development of airway remodeling, characterized by increased airway smooth muscle (ASM) mass and extracellular matrix (ECM) deposition. Decreased plasma membrane caveolin-1 (CAV1) expression has been implicated in airway disease and may contribute to airway remodeling and hyperreactivity. Here, we investigated the impact of clinically relevant moderate hyperoxia (50% O₂) on airway remodeling and caveolar protein expression in a neonatal mouse model. Within 12 h of birth, litters of B6129SF2J mice were randomized to room air (RA) or 50% hyperoxia exposure for 7 days with or without caveolin-1 scaffolding domain peptide (CSD; caveolin-1 mimic; 10 µl, 0.25 mM daily via intraperitoneal injection) followed by 14 days of recovery in normoxia. Moderate hyperoxia significantly increased airway reactivity and decreased pulmonary compliance at 3 wk. Histologic assessment demonstrated airway wall thickening and increased ASM mass following hyperoxia. RNA from isolated ASM demonstrated significant decreases in CAV1 and cavin-1 in hyperoxia-exposed animals while cavin-3 was increased. Supplementation with intraperitoneal CSD mitigated both the physiologic and histologic changes observed with hyperoxia. Overall, these data show that moderate hyperoxia is detrimental to developing airway and may predispose to airway reactivity and remodeling. Loss of CAV1 is one mechanism through which hyperoxia produces these deleterious effects. Supplementation of CAV1 using CSD or similar analogs may represent a new therapeutic avenue for blunting hyperoxia-induced pulmonary damage in neonates.

Cellular senescence in the lung across the age spectrum

Cellular senescence results in cell cycle arrest with secretion of cytokines, chemokines, growth factors, and remodeling proteins (senescence-associated secretory phenotype; SASP) that have autocrine and paracrine effects on the tissue microenvironment. SASP can promote remodeling, inflammation, infectious susceptibility, angiogenesis, and proliferation, while hindering tissue repair and regeneration. While the role of senescence and the contributions of senescent cells are increasingly recognized in the context of aging and a variety of disease states, relatively less is known regarding the portfolio and influences of senescent cells in normal lung growth and aging per se or in the induction or progression of lung diseases across the age spectrum such as bronchopulmonary dysplasia, asthma, chronic obstructive pulmonary disease, or pulmonary fibrosis. In this review, we introduce concepts of cellular senescence, the mechanisms involved in the induction of senescence, and the SASP portfolio that are relevant to lung cells, presenting the potential contribution of senescent cells and SASP to inflammation, hypercontractility, and remodeling/fibrosis: aspects critical to a range of lung diseases. The potential to blunt lung disease by targeting senescent cells using a novel class of drugs (senolytics) is discussed. Potential areas for future research on cellular senescence in the lung are identified.

Pulmonary function in former very low birth weight preterm infants in the first year of life

BACKGROUND

Pulmonary function in former preterm infants may be compromised during childhood.

OBJECTIVES

To assess pulmonary function in very-low-birth-weight preterm infants at 6-12 months of corrected age and analyze the factors associated with abnormal pulmonary function.

METHODS

Cross-sectional study with preterm infants at 6-12 months of corrected age with birth weight <1500 g. Children with malformations or affected by neuromuscular and respiratory diseases were excluded. Forced expiratory flows were assessed using the chest compression technique, and volumes were measured by total body plethysmography. Pulmonary function parameters in preterm infants were compared to a control group of same-aged children born at term.

RESULTS

We studied 51 preterm and 37 infants born at term. Preterm infants had: gestational age at birth (30.0 ± 2.5 weeks), birth weight (1179 ± 247 g), 27.5% had bronchopulmonary dysplasia, and 45% received mechanical ventilation. Preterm infants had lower median z-scores in comparison to term infants for the following parameters (p < 0.05): FVC (-0.3 vs. 0.7), FEV_0.5 (-0.5 vs. 0.9), FEV_0.5/FVC (-0.6 vs. -0.5), FEF₅₀ (-0.4 vs. 0.9), FEF₇₅ (-0.3 vs. 0.8), FEF₈₅ (-0.1 vs. 0.6) and FEF_25-75 (-0.5 vs. 1.1). No term child had abnormal lung function, compared to 39.2% of preterm infants (p = 0.001). Factors associated with abnormal pulmonary function were lower gestational age at birth, small for gestational age, need for mechanical ventilation and presence of recurrent wheezing.

CONCLUSIONS

Preterms had a high prevalence of abnormal pulmonary function and lower pulmonary function in comparison to term infants. Prematurity, intrauterine growth restriction, respiratory support and recurrent wheezing were associated with abnormal pulmonary function.

Pneumonia

Neonatal pneumonia may occur in isolation or as one component of a larger infectious process. Bacteria, viruses, fungi, and parasites are all potential causes of neonatal pneumonia, and may be transmitted vertically from the mother or acquired from the postnatal environment. The patient's age at the time of disease onset may help narrow the differential diagnosis, as different pathogens are associated with congenital, early-onset, and late-onset pneumonia. Supportive care and rationally selected antimicrobial therapy are the mainstays of treatment for neonatal pneumonia. The challenges involved in microbiological testing of the lower airways may prevent definitive identification of a causative organism. In this case, secondary data must guide selection of empiric therapy, and the response to treatment must be closely monitored.

Are preterm-born survivors at risk of long-term respiratory disease?

BACKGROUND

To evaluate the long-term impact of preterm birth on respiratory function in female patients born preterm, we undertook spirometric examinations twice, as they reached the age of puberty, then follow-up examinations of part of the same cohort in adulthood. We sought evidence that preterm birth is correlated with poorer spirometric results into adulthood.

METHODS

A total of 70 girls (aged 12.2 ± 1.5 years in 1997) who had been born preterm (at 34.7 ± 1.86 weeks, none having experienced bronchopulmonary dysplasia) took part in spriometric examinations in 1997 and again in 1998. Of those, after a gap of 17 years, a group of 12 were successfully recontacted and participated in the 2015 examination as adults (then aged 27.6 ± 2.6 years, born at 34.5 ± 1.92 weeks). We compared spirometric results across the adolescent and adult examinations, and compared the adult results with an adult reference group.

RESULTS

The percentage values of FEV1 (forced expiratory volume in 1 s), FVC (forced vital capacity) and MVV (maximal voluntary ventilation) showed significant improvement between the two examinations in the early adolescent period. In adulthood, FEV1%pred (percentage predicted forced expiratory volume in 1 s) showed no statistically significant difference. The mean values of both FVC and FVC%pred (percentage predicted forced vital capacity) for the preterm-born group were lower than for the reference group, but this was not statistically significant. The preterm-born group showed lower values of such parameters as forced expiratory flow at 25-75% of FVC, MEF25 (maximal expiratory flow at 25% of forced vital capacity) and FEV1/FVC as compared with the reference group, but again without statistical significance.

CONCLUSIONS

(1) A somewhat below-norm level of respiratory parameters among preterm-born girls entering pubescence may attest to continued negative impact on their respiratory system. (2) A significant improvement in their spirometric results 1 year later may indicate that pubescence helps compensate for the earlier negative effect of preterm birth. (3) No significant differences were seen in lung function in preterm-born adults as compared with a reference group of adults, although the preterm-born group did exhibit lower values of all parameters studied and more frequent obstructive disorders.

Effects of antenatal lipopolysaccharide and postnatal hyperoxia on airway reactivity and remodeling in a neonatal mouse model

BACKGROUND

Antenatal inflammation and preterm birth are associated with the development of airway diseases such as wheezing and asthma. Utilizing a newborn mouse model, we assessed the effects of maternal inflammation and postnatal hyperoxia on the neonatal airway.

METHODS

Pregnant C57/Bl6 dams were injected with lipopolysaccharide (LPS) or saline on embryonic day 16. Offspring were placed in room air or hyperoxia (50% O2) for 7 d and then returned to normoxia. Airway mechanics, histology, and laser capture micro-dissection (LCM) were performed.

RESULTS

At postnatal day 21, maternal LPS- and 50% O2-exposed pups exhibited increased resistance and decreased compliance compared to 21% O2 pups; however their effects were not synergistic. LPS and hyperoxia each increased the thickness of airway smooth muscle (ASM), but not the airway epithelial layer. Structural changes were largely limited to the conducting airways. Upregulation of inflammatory markers in the lung was observed at birth. LCM revealed increased collagen-3, transforming growth factor β, and connective tissue growth factor expression with LPS and hyperoxia within the ASM layer.

CONCLUSION

These novel studies provide functional, structural, and molecular evidence that antenatal inflammation is detrimental to the developing airway. Exposure to moderate hyperoxia does not exacerbate LPS effects on the airway.

Long-term effects of pneumonia in young children

Each year an estimated 120 million episodes of pneumonia occur in children younger than 5 years of age, resulting in one million deaths globally. Within this age group the lungs are still developing by increasing alveoli numbers and airway dimensions. Pneumonia during this critical developmental period may therefore adversely affect the lung's structure and function, with increased risk of subsequent chronic lung disease. However, there are few longitudinal studies of pneumonia in otherwise healthy children that extend into adulthood to help address this important question. Birth cohort, longitudinal, case-control and retrospective studies have reported restrictive and obstructive lung function deficits, asthma, bronchiectasis, and chronic obstructive pulmonary disease. In particular, severe hospitalised pneumonia had the greatest risk for long-term sequelae. Most studies, however, were limited by incomplete follow-up, some reliance upon parental recall, risk of diagnostic misclassification, and potential confounders such as nutrition, social deprivation, and pre-existing small airways or lungs. More long-term studies measuring lung function shortly after birth are needed to help disentangle the complex relationships between pneumonia and later chronic lung disease, while also addressing host responses, types of infection, and potential confounding variables. Meanwhile, parents of young children with pneumonia need to be advised about the importance of symptom resolution, post-pneumonia. In addition, paying attention to factors associated with optimising lung growth such as good nutrition, minimising exposure to air pollution, avoiding cigarette smoke, and decreasing the risk of preventable infections through good hygiene and having their children fully vaccinated should be emphasised. Finally, in the developing world and for disadvantaged communities in developed countries, public health policies leading to good quality housing and heating, hygiene, education, and improving socio-economic status are also essential.

TLR3 activation increases chemokine expression in human fetal airway smooth muscle cells

Viral infections, such as respiratory syncytial virus and rhinovirus, adversely affect neonatal and pediatric populations, resulting in significant lung morbidity, including acute asthma exacerbation. Studies in adults have demonstrated that human airway smooth muscle (ASM) cells modulate inflammation through their ability to secrete inflammatory cytokines and chemokines. The role of ASM in the developing airway during infection remains undefined. In our study, we used human fetal ASM cells as an in vitro model to examine the effect of Toll-like receptor (TLR) agonists on chemokine secretion. We found that fetal ASM express multiple TLRs, including TLR3 and TLR4, which are implicated in the pathogenesis of respiratory syncytial virus and rhinovirus infection. Cells were treated with TLR agonists, polyinosinic-polycytidylic acid [poly(I:C)] (TLR3 agonist), lipopolysaccharide (TLR4 agonist), or R848 (TLR7/8 agonist), and IL-8 and chemokine (C-C motif) ligand 5 (CCL5) secretion were evaluated. Interestingly, poly(I:C), but neither lipopolysaccharide nor R848, increased IL-8 and chemokine (C-C motif) ligand 5 secretion. Examination of signaling pathways suggested that the poly(I:C) effects in fetal ASM involve TLR and ERK signaling, in addition to another major inflammatory pathway, NF-κB. Moreover, there are variations between fetal and adult ASM with respect to poly(I:C) effects on signaling pathways. Pharmacological inhibition suggested that ERK pathways mediate poly(I:C) effects. Overall, our data show that poly(I:C) initiates activation of proinflammatory pathways in developing ASM, which may contribute to immune responses to infection and exacerbation of asthma.

Perinatal factors associated with long-term respiratory sequelae in extremely low birthweight infants

OBJECTIVE

To assess lung function at 8 years old in extremely low birthweight (ELBW) survivors and to identify perinatal determinants associated with impaired lung function.

DESIGN

Retrospective cohort study.

SETTING

Level III neonatal intensive care unit.

PATIENTS

ELBW survivors born in 1990-2004 with available spirometry at 8 years old were studied. Children were excluded if they had a Wechsler Intelligence Scale for Children Third Edition full IQ <70.

MAIN OUTCOME MEASURES

Multivariate logistic regression analysis was used to identify perinatal determinants associated with airway obstruction (forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio <80%) at school age and the predictive power of potential determinants. Potential risk factors and predictors assessed in this study were gestational age, birth weight, small for gestational age, sex, chorioamnionitis, premature rupture of membranes, antenatal steroids, surfactant administration, respiratory distress syndrome, postnatal steroids, severe bronchopulmonary dysplasia and bubbly/cystic appearances of the lungs by X-ray during the neonatal period.

RESULTS

Of 656 ELBW survivors, 301 (45.9%) had attended a school-age follow-up at 8 years old. A total of 201 eligible children completed the lung function test. Bubbly/cystic appearance of the lungs (OR 4.84, 95% CI 1.26 to 18.70) was associated with a low FEV1/FVC ratio. Children with bubbly/cystic appearance had characteristics of immaturity and intrauterine inflammation.

CONCLUSIONS

Within a cohort of ELBW infants, a bubbly/cystic appearance of the lungs in the neonatal period was the strongest determinant of a low FEV1/FVC ratio at school age.

Vitamin D attenuates cytokine-induced remodeling in human fetal airway smooth muscle cells

Asthma in the pediatric population remains a significant contributor to morbidity and increasing healthcare costs. Vitamin D3 insufficiency and deficiency have been associated with development of asthma. Recent studies in models of adult airway diseases suggest that the bioactive Vitamin D3 metabolite, calcitriol (1,25-dihydroxyvitamin D3 ; 1,25(OH)2 D3 ), modulates responses to inflammation; however, this concept has not been explored in developing airways in the context of pediatric asthma. We used human fetal airway smooth muscle (ASM) cells as a model of the early postnatal airway to explore how calcitriol modulates remodeling induced by pro-inflammatory cytokines. Cells were pre-treated with calcitriol and then exposed to TNFα or TGFβ for up to 72 h. Matrix metalloproteinase (MMP) activity, production of extracellular matrix (ECM), and cell proliferation were assessed. Calcitriol attenuated TNFα enhancement of MMP-9 expression and activity. Additionally, calcitriol attenuated TNFα and TGFβ-induced collagen III expression and deposition, and separately, inhibited proliferation of fetal ASM cells induced by either inflammatory mediator. Analysis of signaling pathways suggested that calcitriol effects in fetal ASM involve ERK signaling, but not other major inflammatory pathways. Overall, our data demonstrate that calcitriol can blunt multiple effects of TNFα and TGFβ in developing airway, and point to a potentially novel approach to alleviating structural changes in inflammatory airway diseases of childhood.

Perinatal oxygen in the developing lung

Lung diseases, such as bronchopulmonary dysplasia (BPD), wheezing, and asthma, remain significant causes of morbidity and mortality in the pediatric population, particularly in the setting of premature birth. Pulmonary outcomes in these infants are highly influenced by perinatal exposures including prenatal inflammation, postnatal intensive care unit interventions, and environmental agents. Here, there is strong evidence that perinatal supplemental oxygen administration has significant effects on pulmonary development and health. This is of particular importance in the preterm lung, where premature exposure to room air represents a hyperoxic insult that may cause harm to a lung primed to develop in a hypoxic environment. Preterm infants are also subject to increased episodes of hypoxia, which may also result in pulmonary damage and disease. Here, we summarize the current understanding of the effects of oxygen on the developing lung and how low vs. high oxygen may predispose to pulmonary disease that may extend even into adulthood. Better understanding of the underlying mechanisms will help lead to improved care and outcomes in this vulnerable population.

Cigarette smoke enhances proliferation and extracellular matrix deposition by human fetal airway smooth muscle

Cigarette smoke is a common environmental insult associated with increased risk of developing airway diseases such as wheezing and asthma in neonates and children. In adults, asthma involves airway remodeling characterized by increased airway smooth muscle (ASM) cell proliferation and increased extracellular matrix (ECM) deposition, as well as airway hyperreactivity. The effects of cigarette smoke on remodeling and contractility in the developing airway are not well-elucidated. In this study, we used canalicular-stage (18-20 wk gestational age) human fetal airway smooth muscle (fASM) cells as an in vitro model of the immature airway. fASM cells were exposed to cigarette smoke extract (CSE; 0.5-1.5% for 24-72 h), and cell proliferation, ECM deposition, and intracellular calcium ([Ca(2+)]i) responses to agonist (histamine 10 μM) were used to evaluate effects on remodeling and hyperreactivity. CSE significantly increased cell proliferation and deposition of ECM molecules collagen I, collagen III, and fibronectin. In contrast, [Ca(2+)]i responses were not significantly affected by CSE. Analysis of key signaling pathways demonstrated significant increase in extracellular signal-related kinase (ERK) and p38 activation with CSE. Inhibition of ERK or p38 signaling prevented CSE-mediated changes in proliferation, whereas only ERK inhibition attenuated the CSE-mediated increase in ECM deposition. Overall, these results demonstrate that cigarette smoke may enhance remodeling in developing human ASM through hyperplasia and ECM production, thus contributing to development of neonatal and pediatric airway disease.