The influence of gender on respiratory outcomes in children with bronchopulmonary dysplasia during the first 3 years of life

Exploring the Association of Male Sex With Adverse Outcomes in Severe Bronchopulmonary Dysplasia: A Retrospective, Multicenter Cohort Study

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a significant contributor to morbidity and death in infants who are born premature. Male sex is an independent risk factor for the development of BPD. However, whether male sex is associated with adverse outcomes that occur after formal diagnosis of severe BPD prior to hospital discharge remains unclear.

RESEARCH QUESTION

Is male sex associated with a higher risk of adverse outcomes in infants with established severe BPD?

STUDY DESIGN AND METHODS

A retrospective, multicenter cohort study of infants enrolled in the BPD Collaborative Registry from January 1, 2015, to June 29, 2022, was performed. Demographics, clinical characteristics, and outcomes were stratified by sex (ie, male vs female). Regression modeling was used to estimate the association of sex with the primary composite outcome of death or tracheostomy at hospital discharge.

RESULTS

We identified 1,156 infants with severe BPD, defined at 36 weeks postmenstrual age by the National Institutes of Health 2001 consensus definition. The cohort was predominantly male (59% male infants, 41% female infants). However, rates of mechanical ventilation at 36 weeks postmenstrual age (ie, type 2 severe BPD) did not differ by sex. Overall mortality rates within the cohort were low (male infants, 5.3%; female infants, 3.6%). The OR of death or tracheostomy for male-to-female infants was 1.0 (95% CI, 0.7-1.5).

INTERPRETATION

Our results lead us to speculate that, although sex is an important variable that contributes to the development and pathogenesis of severe BPD, it does not appear to be associated with adverse outcomes in this cohort of infants with established disease. The surprising results raise important questions surrounding the temporal role of biological sex in the development of severe BPD and its progression during the neonatal ICU stay. As we explore the phenotypes and endotypes of BPD, it is imperative to consider how sex modulates the disease from birth through hospital discharge.

Five-year follow-up of phase II trial of stromal cells for bronchopulmonary dysplasia

BACKGROUND

We previously performed a phase II randomised double-blind clinical trial of mesenchymal stromal cell (MSCs) transplantation to prevent bronchopulmonary dysplasia in extremely premature infants. Subsequently, we followed the infants enrolled in this clinical trial to determine the safety and effectiveness of MSCs against bronchopulmonary dysplasia at 5-year follow-up.

METHODS

We evaluated infants at 5 years of age receiving placebo or MSCs in a prospective follow-up study.

RESULTS

In terms of the primary end point of composite respiratory morbidities, including respiratory problem-related readmission, emergency department visits or oxygen therapy, the MSC group had a rate of 60.7% for composite morbidities, while the control group showed a tendency of higher rate of 83.9% for the same outcomes without statistical significance. In terms of the secondary outcomes, the MSC group infants showed a tendency of being less likely to visit emergency department (control 67.7% vs MSC 35.7%) and to receive oxygen therapy (control 29.0% vs MSC 3.6%). No difference was observed in the incidence of respiratory problem-related hospital readmission or wheezing episodes between the groups.

CONCLUSION

Intratracheally instilled MSCs showed the possibility of potential to decrease respiratory symptom-related emergency department visits and oxygen therapy episodes in infants born extremely preterm during the 5 years after a phase II randomised controlled, double-blind trial of MSCs transplantation for bronchopulmonary dysplasia. This small size study suggests preliminary insights that can be further tested using larger sample sizes.

TRIAL REGISTRATION NUMBER

NCT01897987.

Timing and cell specificity of senescence drives postnatal lung development and injury

Senescence causes age-related diseases and stress-related injury. Paradoxically, it is also essential for organismal development. Whether senescence contributes to lung development or injury in early life remains unclear. Here, we show that lung senescence occurred at birth and decreased throughout the saccular stage in mice. Reducing senescent cells at this stage disrupted lung development. In mice (<12 h old) exposed to hyperoxia during the saccular stage followed by air recovery until adulthood, lung senescence increased particularly in type II cells and secondary crest myofibroblasts. This peaked during the alveolar stage and was mediated by the p53/p21 pathway. Decreasing senescent cells during the alveolar stage attenuated hyperoxia-induced alveolar and vascular simplification. Conclusively, early programmed senescence orchestrates postnatal lung development whereas later hyperoxia-induced senescence causes lung injury through different mechanisms. This defines the ontogeny of lung senescence and provides an optimal therapeutic window for mitigating neonatal hyperoxic lung injury by inhibiting senescence.

Sex-related external factors influence pulmonary vascular angiogenesis in a sex-dependent manner

Bronchopulmonary dysplasia (BPD) is a disease with a significant sexual dimorphism where males have a disadvantage compared with their female counterparts. Although mechanisms behind this sexual dimorphism are poorly understood, sex differences in angiogenesis have been identified as one possible source of the male disadvantage in BPD. Pulmonary angiogenesis was assessed in vitro using a bead sprouting assay with pooled male or female human pulmonary microvascular endothelial cells (HPMECs, 18-19 wk gestation, canalicular stage of human lung development) in standard (sex-hormone containing) and hormone-stripped medium. We identified sex-specific phenotypes in angiogenesis where male HPMECs produce fewer but longer sprouts compared with female HPMECs. The presence of sex hormones from standard culture medium modifies the male HPMEC phenotype with shorter and fewer sprouts but does not influence the female phenotype. Using a conditioned medium model, we further characterized the influence of the sex-specific secretome. Male and female HPMECs secrete factors that increase the maximum length of sprouts in female, but not male HPMECs. The presence of sex hormones abolishes this response. The male HPMEC secretome inhibits angiogenic sprouting in male HPMECs in the absence of sex hormones. Taken together, these results demonstrate that the pulmonary endothelial cell phenotypes are influenced by sex hormones and sex-specific secreted factors in a sex-dependent manner.NEW & NOTEWORTHY We identified a sex-specific phenotype wherein male HPMECs produce fewer but longer sprouts than females. Surprisingly, the presence of sex hormones only modifies the male phenotype, resulting in shorter and even fewer sprouts. Furthermore, we found the sex-specific secretome has a sex-dependent influence on angiogenesis that is also sex-hormone sensitive. These new and surprising findings point to the unappreciated role of sex and sex-related exogenous factors in early developmental angiogenesis.

Severity of respiratory disease is correlated with time of first oral feeding and need for a gastrostomy tube at discharge in premature infants born at <30 weeks of gestation

BACKGROUND

Premature infants who cannot achieve full oral feeds may need a gastrostomy tube (GT) to be discharged from the neonatal intensive care unit (NICU). We previously developed a model to predict which infants born <30 weeks (w) gestational age (GA) will require a GT before discharge. Here we report the detailed respiratory variable data to describe the general respiratory course for infants in the NICU < 30 w GA at birth and the association between different levels of respiratory support with postmenstrual age (PMA) at the time of first oral feeding attempt (PMAff), including later need for GT for discharge.

METHODS

Retrospective chart review of 391 NICU admissions comprising test (2015-2016) and validation (2017-2018) cohorts. Data, including respiratory support, were collected on 204 infants, 41 GT and 163 non-GT, in the test cohort, and 187 infants, 37 GT, and 150 non-GT, in the validation cohort.

RESULTS

Respiratory data were significantly different between GT and non-GT infants. Infants who required GT for discharge were on significantly higher respiratory support at 30 days of age, 32 w PMA, and 36 w PMA. Respiratory parameters were highly correlated with PMAff.

CONCLUSION

Respiratory status predicts PMAff, which was the variable in our previously described model that was most predictive of failure to achieve full oral feeding. These data provide a catalyst to develop strategies for improving oral feeding outcome for infants requiring prolonged respiratory support in the NICU.

Single-cell transcriptomics reveals lasting changes in the lung cellular landscape into adulthood after neonatal hyperoxic exposure

Ventilatory support, such as supplemental oxygen, used to save premature infants impairs the growth of the pulmonary microvasculature and distal alveoli, leading to bronchopulmonary dysplasia (BPD). Although lung cellular composition changes with exposure to hyperoxia in neonatal mice, most human BPD survivors are weaned off oxygen within the first weeks to months of life, yet they may have persistent lung injury and pulmonary dysfunction as adults. We hypothesized that early-life hyperoxia alters the cellular landscape in later life and predicts long-term lung injury. Using single-cell RNA sequencing, we mapped lung cell subpopulations at postnatal day (pnd)7 and pnd60 in mice exposed to hyperoxia (95% O2) for 3 days as neonates. We interrogated over 10,000 cells and identified a total of 45 clusters within 32 cell states. Neonatal hyperoxia caused persistent compositional changes in later life (pnd60) in all five type II cell states with unique signatures and function. Premature infants requiring mechanical ventilation with different durations also showed similar alterations in these unique signatures of type II cell states. Pathologically, neonatal hyperoxic exposure caused alveolar simplification in adult mice. We conclude that neonatal hyperoxia alters the lung cellular landscape in later life, uncovering neonatal programing of adult lung dysfunction.

Hyperoxia-induced bronchopulmonary dysplasia: better models for better therapies

Bronchopulmonary dysplasia (BPD) is a chronic lung disease caused by exposure to high levels of oxygen (hyperoxia) and is the most common complication that affects preterm newborns. At present, there is no cure for BPD. Infants can recover from BPD; however, they will suffer from significant morbidity into adulthood in the form of neurodevelopmental impairment, asthma and emphysematous changes of the lung. The development of hyperoxia-induced lung injury models in small and large animals to test potential treatments for BPD has shown some success, yet a lack of standardization in approaches and methods makes clinical translation difficult. In vitro models have also been developed to investigate the molecular pathways altered during BPD and to address the pitfalls associated with animal models. Preclinical studies have investigated the efficacy of stem cell-based therapies to improve lung morphology after damage. However, variability regarding the type of animal model and duration of hyperoxia to elicit damage exists in the literature. These models should be further developed and standardized, to cover the degree and duration of hyperoxia, type of animal model, and lung injury endpoint, to improve their translational relevance. The purpose of this Review is to highlight concerns associated with current animal models of hyperoxia-induced BPD and to show the potential of in vitro models to complement in vivo studies in the significant improvement to our understanding of BPD pathogenesis and treatment. The status of current stem cell therapies for treatment of BPD is also discussed. We offer suggestions to optimize models and therapeutic modalities for treatment of hyperoxia-induced lung damage in order to advance the standardization of procedures for clinical translation.

Serious neonatal morbidities are associated with differences in DNA methylation among very preterm infants

Background

Infants born very preterm are more likely to experience neonatal morbidities compared to their term peers. Variations in DNA methylation (DNAm) associated with these morbidities may yield novel information about the processes impacted by these morbidities.

Methods

This study included 532 infants born < 30 weeks gestation, participating in the Neonatal Neurobehavior and Outcomes in Very Preterm Infants study. We used a neonatal morbidity risk score, which was an additive index of the number of morbidities experienced during the NICU stay, including bronchopulmonary dysplasia (BPD), severe brain injury, serious neonatal infections, and severe retinopathy of prematurity. DNA was collected from buccal cells at discharge from the NICU, and DNAm was measured using the Illumina MethylationEPIC. We tested for differential methylation in association with the neonatal morbidity risk score then tested for differentially methylated regions (DMRs) and overrepresentation of biological pathways.

Results

We identified ten differentially methylated CpGs (α Bonferroni-adjusted for 706,278 tests) that were associated with increasing neonatal morbidity risk scores at three intergenic regions and at HPS4, SRRD, FGFR1OP, TNS3, TMEM266, LRRC3B, ZNF780A, and TENM2. These mostly followed dose–response patterns, for 8 CpGs increasing DNAm associated with increased numbers of morbidities, while for 2 CpGs the risk score was associated with decreasing DNAm. BPD was the most substantial contributor to differential methylation. We also identified seven potential DMRs and over-representation of genes involved in Wnt signaling; however, these results were not significant after Bonferroni adjustment for multiple testing.

Conclusions

Neonatal DNAm, within genes involved in fibroblast growth factor activities, cellular invasion and migration, and neuronal signaling and development, are sensitive to the neonatal health complications of prematurity. We hypothesize that these epigenetic features may be representative of an integrated marker of neonatal health and development and are promising candidates to integrate with clinical information for studying developmental impairments in childhood.

Bronchopulmonary dysplasia: what are its links to COPD?

Emerging evidence suggests that adverse early life events can affect long-term health trajectories throughout life. Preterm birth, in particular, is a significant early life event that affects approximately 10% of live births. Worldwide, prematurity is the number one cause of death in children less than 5 years of age and has been shown to disrupt normal lung development with lasting effects into adult life. Along with impaired lung development, interventions used to support gas exchange and other sequelae of prematurity can lead to the development of bronchopulmonary dysplasia (BPD). BPD is a chronic respiratory disease of infancy characterized by alveolar simplification, small airways disease, and pulmonary vascular changes. Although many survivors of BPD improve with age, survivors of BPD often have chronic lung disease characterized by airflow obstruction and intermittent pulmonary exacerbations. Long-term lung function trajectories as measured by FEV1 can be lower in children and adults with a history BPD. In this review, we discuss the epidemiology and manifestations of BPD and its long-term consequences throughout childhood and into adulthood. Available evidence suggests that disrupted lung development, genetic susceptibility and subsequent environment and infectious events that occur in prenatal and postnatal life likely increase the predisposition of children with BPD to develop early onset chronic obstructive pulmonary disease (COPD). The reviews of this paper are available via the supplemental material section.

Respiratory Phenotypes for Preterm Infants, Children, and Adults: Bronchopulmonary Dysplasia and More

Ongoing advancements in neonatal care since the late 1980s have led to increased numbers of premature infants surviving well beyond the neonatal period. As a result of increased survival, many individuals born preterm manifest chronic respiratory symptoms throughout infancy, childhood, and adult life. The archetypical respiratory disease of prematurity, bronchopulmonary dysplasia, is the second most common chronic pediatric respiratory disease after asthma. However, there are several commonly held misconceptions. These misconceptions include that bronchopulmonary dysplasia is rare, that bronchopulmonary dysplasia resolves within the first few years of life, and that bronchopulmonary dysplasia does not impact respiratory health in adult life. This focused review describes a spectrum of respiratory conditions that individuals born prematurely may experience throughout their lifespan. Specifically, this review provides quantitative estimates of the number of individuals with alveolar, airway, and vascular phenotypes associated with bronchopulmonary dysplasia, as well as non-bronchopulmonary dysplasia respiratory phenotypes such as airway malacia, obstructive sleep apnea, and control of breathing issues. Furthermore, this review illustrates what is known about the potential for progression and/or lack of resolution of these respiratory phenotypes in childhood and adult life. Recognizing the spectrum of respiratory phenotypes associated with individuals born preterm and providing comprehensive and personalized care to these individuals may help to modulate adverse respiratory outcomes in later life.

Former-preterm lambs have persistent alveolar simplification at 2 and 5 months corrected postnatal age

Preterm birth and mechanical ventilation (MV) frequently lead to bronchopulmonary dysplasia, the histopathological hallmark of which is alveolar simplification. How developmental immaturity and ongoing injury, repair, and remodeling impact completion of alveolar formation later in life is not known, in part because of lack of suitable animal models. We report a new model, using former-preterm lambs, to test the hypothesis that they will have persistent alveolar simplification later in life. Moderately preterm lambs (~85% gestation) were supported by MV for ~6 days before being transitioned from all respiratory support to become former-preterm lambs. Results are compared with term control lambs that were not ventilated, and between males (M) and females (F). Alveolar simplification was quantified morphometrically and stereologically at 2 mo (4 M, 4 F) or 5 mo (4 M, 6 F) corrected postnatal age (cPNA) compared with unventilated, age-matched term control lambs (4 M, 4 F per control group). These postnatal ages in sheep are equivalent to human postnatal ages of 1-2 yr and ~6 yr, respectively. Multivariable linear regression results showed that former-preterm lambs at 2 or 5 mo cPNA had significantly thicker distal airspace walls ( P < 0.001 and P < 0.009, respectively), lower volume density of secondary septa ( P < 0.007 and P < 0.001, respectively), and lower radial alveolar count ( P < 0.003 and P < 0.020, respectively) compared with term control lambs. Sex-specific differences were not detected. We conclude that moderate preterm birth and MV for ~6 days impedes completion of alveolarization in former-preterm lambs. This new model provides the opportunity to identify underlying pathogenic mechanisms that may reveal treatment approaches.

Predictors of length of stay for initial hospitalization in infants with bronchopulmonary dysplasia

OBJECTIVE

Longer initial hospitalizations for preterm infants with bronchopulmonary dysplasia (BPD) can delay family bonding and attainment of developmental milestones, increase the risk for hospital acquired complications, and increase healthcare costs. The goal of the study was to identify the characteristics associated with longer lengths of hospitalization in this high-risk population.

STUDY DESIGN

A retrospective analysis was performed on 660 children (born ≤32 weeks gestation) discharged from 13 Maryland NICUs recruited into an outpatient BPD registry.

RESULT

The mean age of discharge was 4.3 ± 2.9 months (median: 3.7 months). Subjects born with lower birthweights and covered by public insurance had longer lengths of hospitalization. Clinical characteristics at discharge associated with longer initial hospitalizations included gastrostomy tube, mechanical ventilation, tracheostomy, pulmonary hypertension, and supplemental oxygen.

CONCLUSION

Identifying the risk factors associated with longer lengths of stay could prompt the implementation of personalized in-hospital interventions to improve outcomes and minimize length of stay in infants with BPD.

2017 pediatric pulmonology year in review part 2-neonatology

The articles published in 2017 in topic areas relevant to neonatal pulmonology are reviewed in Part 2 of the Year-in-Review.

Does the sex of the preterm baby affect respiratory outcomes?

Being born very preterm is associated with later deficits in lung function and an increased rate of respiratory symptoms compared with term-born children. The rates of early respiratory infections are higher in very preterm-born subjects, which may independently lead to deficits in lung function in later life. As with very preterm-born children, deficits in lung function, increased respiratory symptoms and an increased risk of respiratory infections in early life are observed in late -preterm-born children. However, the rates of respiratory symptoms are lower compared with very preterm-born children. There is some evidence to suggest that respiratory outcomes may be improving over time, although not all the evidence suggests improvements. Male sex appears to increase the risk for later adverse respiratory illness. Although not all studies report that males have worse long-term respiratory outcomes than females. It is essential that preterm-born infants are followed up into childhood and beyond, and that appropriate treatment for any lung function deficits and respiratory symptoms is prescribed if necessary. If these very preterm-born infants progress to develop chronic obstructive airway disease in later life then the impact, not only on the individuals, but also the economic impact on healthcare services, is immense.

Educational aims

To report the effect of the sex of the preterm baby on respiratory outcomes.To explore the short- and long-term respiratory outcomes of preterm birth.

Aberrant activation of the human sex-determining gene in early embryonic development results in postnatal growth retardation and lethality in mice

Sexual dimorphisms are prevalent in development, physiology and diseases in humans. Currently, the contributions of the genes on the male-specific region of the Y chromosome (MSY) in these processes are uncertain. Using a transgene activation system, the human sex-determining gene hSRY is activated in the single-cell embryos of the mouse. Pups with hSRY activated (hSRY^ON) are born of similar sizes as those of non-activated controls. However, they retard significantly in postnatal growth and development and all die of multi-organ failure before two weeks of age. Pathological and molecular analyses indicate that hSRY^ON pups lack innate suckling activities, and develop fatty liver disease, arrested alveologenesis in the lung, impaired neurogenesis in the brain and occasional myocardial fibrosis and minimized thymus development. Transcriptome analysis shows that, in addition to those unique to the respective organs, various cell growth and survival pathways and functions are differentially affected in the transgenic mice. These observations suggest that ectopic activation of a Y-located SRY gene could exert male-specific effects in development and physiology of multiple organs, thereby contributing to sexual dimorphisms in normal biological functions and disease processes in affected individuals.