Genetic risk factors of bronchopulmonary dysplasia

Unravelling the respiratory health path across the lifespan for survivors of preterm birth

Many survivors of preterm birth will have abnormal lung development, reduced peak lung function and, potentially, an increased rate of physiological lung function decline, each of which places them at increased risk of chronic obstructive pulmonary disease across the lifespan. Current rates of preterm birth indicate that by the year 2040, around 50 years since the introduction of surfactant therapy, more than 700 million individuals will have been born prematurely-a number that will continue to increase by about 15 million annually. In this Personal View, we describe current understanding of the impact of preterm birth on lung function through the life course, with the aim of putting this emerging health crisis on the radar for the respiratory community. We detail the potential underlying mechanisms of prematurity-associated lung disease and review current approaches to prevention and management. Furthermore, we propose a novel way of considering lung disease after preterm birth, using a multidimensional model to determine individual phenotypes of lung disease-a first step towards optimising management approaches for prematurity-associated lung disease.

Genetics of bronchopulmonary dysplasia: An update

Bronchopulmonary dysplasia (BPD) is a multi-factorial disease that results from multiple clinical factors, including lung immaturity, mechanical ventilation, oxidative stress, pulmonary congestion due to increasing cardiac blood shunting, nutritional and immunological factors. Twin studies have indicated that susceptibility to BPD can be strongly inherited in some settings. Studies have reported associations between common genetic variants and BPD in preterm infants. Recent genomic studies have highlighted a potential role for molecular pathways involved in inflammation and lung development in affected infants. Rare mutations in genes encoding the lipid transporter ATP-binding cassette, sub-family A, member 3 (ABCA3 gene) which is involved in surfactant synthesis in alveolar type II cells, as well as surfactant protein B (SFTPB) and C (SFTPC) can also result in severe form of neonatal-onset interstitial lung diseases and may also potentially affect the course of BPD. This chapter summarizes the current state of knowledge on the genetics of BPD.

Genetic Polymorphisms of Vascular Endothelial Growth Factor in Neonatal Pathologies: A Systematic Search and Narrative Synthesis of the Literature

(1) Background: Vascular endothelial growth factor (VEGF) is essential in vasculo- and angiogenesis due to its role in endothelial cell proliferation and migration. As a vascular proliferative factor, VEGF is one of the hallmarks of cancer and, in adult populations, the relationship between genetic polymorphism and neoplasm was widely investigated. For the neonatal population, only a few studies attempted to uncover the link between the genetic polymorphism of VEGF and neonatal pathology, especially related to late-onset complications. Our objective is to evaluate the literature surrounding VEGF genetic polymorphisms and the morbidity of the neonatal period. (2) Methods: A systematic search was initially conducted in December 2022. The PubMed platform was used to explore MEDLINE (1946 to 2022) and PubMed Central (2000 to 2022) by applying the search string ((VEGF polymorphism*) and newborn*). (3) Results: The PubMed search yielded 62 documents. A narrative synthesis of the findings was undertaken considering our predetermined subheadings (infants with low birth weight or preterm birth, heart pathologies, lung diseases, eye conditions, cerebral pathologies, and digestive pathologies). (4) Conclusion: The VEGF polymorphisms seem to be associated with neonatal pathology. The involvement of VEGF and VEGF polymorphism has been demonstrated for retinopathy of prematurity.

Vascular Endothelial Growth Factor as Molecular Target for Bronchopulmonary Dysplasia Prevention in Very Low Birth Weight Infants

Bronchopulmonary dysplasia (BPD) still represents an important burden of neonatal care. The definition of the disease is currently undergoing several revisions, and, to date, BPD is actually defined by its treatment rather than diagnostic or clinic criteria. BPD is associated with many prenatal and postnatal risk factors, such as maternal smoking, chorioamnionitis, intrauterine growth restriction (IUGR), patent ductus arteriosus (PDA), parenteral nutrition, sepsis, and mechanical ventilation. Various experimental models have shown how these factors cause distorted alveolar and vascular growth, as well as alterations in the composition and differentiation of the mesenchymal cells of a newborn's lungs, demonstrating a multifactorial pathogenesis of the disease. In addition, inflammation and oxidative stress are the common denominators of the mechanisms that contribute to BPD development. Vascular endothelial growth factor-A (VEGFA) constitutes the most prominent and best studied candidate for vascular development. Animal models have confirmed the important regulatory roles of epithelial-expressed VEGF in lung development and function. This educational review aims to discuss the inflammatory pathways in BPD onset for preterm newborns, focusing on the role of VEGFA and providing a summary of current and emerging evidence.

Molecular Polymorphisms of Vascular Endothelial Growth Factor Gene and Bronchopulmonary Dysplasia in Very Low Birth Weight Infants

Background

Bronchopulmonary dysplasia (BPD) is a chronic lung disease affecting primarily preterm and very low birth weight (VLBW) infants. Despite the advances in perinatal care, BPD remains a major clinical and costly complication in premature infants. The pathogenesis of BPD is complex and multifactorial. Prematurity, mechanical ventilation, oxidative stress, and inflammation are recognized as major interrelated contributing factors. Recently, some candidate genes involved in angiogenesis and alveolarization regulating mechanisms have been associated to BPD risk development. The aim of this study was to evaluate the role of vascular endothelial growth factor (VEGF) polymorphisms on BPD onset in VLBW newborns.

Methods

Eighty-two VLBW infants, without major anomalies, were consecutively enrolled: 33 developed BPD (BPD group) and 49 infants without BPD served as controls (control group). In all infants, two polymorphisms, respectively (VEGF receptor) VEGFR1-710 C/T and VEGF +936 C/T, were determined through salivary brush. Genomic DNA was extracted and purified from saliva samples by using the MasterAmp Buccal Swab DNA Extraction Kit (Tebu-bio, Milan, Italy).

Results

Significant statistic differences were found between BPD newborns and controls with regard to gestational age, birth weight, mechanical ventilation, duration of oxygen therapy, maternal preeclampsia, and chorioamnionitis. No differences were detected between genotypic and allelic levels regarding VEGFR1 and VEGF molecular polymorphisms.

Conclusions

Two single nucleotide polymorphisms within VEGF and VEGFR1 genes are not associated with BPD. Further researches are needed to reveal gene polymorphisms involved in vascular development as contributors to the onset of BPD.

Bronchopulmonary dysplasia and wnt pathway-associated single nucleotide polymorphisms

AIM

Genetic variants contribute to the pathogenesis of bronchopulmonary dysplasia (BPD). The aim of this study is to evaluate the association of 45 SNPs with BPD susceptibility in a Turkish premature infant cohort.

METHODS

Infants with gestational age <32 weeks were included. Patients were divided into BPD or no-BPD groups according to oxygen need at 28 days of life, and stratified according to the severity of BPD. We genotyped 45 SNPs, previously identified as BPD risk factors, in 192 infants.

RESULTS

A total of eight SNPs were associated with BPD risk at allele level, two of which (rs4883955 on KLF12 and rs9953270 on CHST9) were also associated at the genotype level. Functional relationship maps suggested an interaction between five of these genes, converging on WNT5A, a member of the WNT pathway known to be implicated in BPD pathogenesis. Dysfunctional CHST9 and KLF12 variants may contribute to BPD pathogenesis through an interaction with WNT5A.

CONCLUSIONS

We suggest investigating the role of SNPs on different genes which are in relation with the Wnt pathway in BPD pathogenesis. We identified eight SNPs as risk factors for BPD in this study. In-silico functional maps show an interaction of the genes harboring these SNPs with the WNT pathway, supporting its role in BPD pathogenesis.

TRIAL REGISTRATION

NCT03467828.

IMPACT

It is known that genetic factors may contribute to the development of BPD in preterm infants. Further studies are required to identify specific genes that play a role in the BPD pathway to evaluate them as a target for therapeutic interventions. Our study shows an association of BPD predisposition with certain polymorphisms on MBL2, NFKBIA, CEP170, MAGI2, and VEGFA genes at allele level and polymorphisms on CHST9 and KLF12 genes at both allele and genotype level. In-silico functional mapping shows a functional relationship of these five genes with WNT5A, suggesting that Wnt pathway disruption may play a role in BPD pathogenesis.

Verification of immunology-related genetic associations in BPD supports ABCA3 and five other genes

BACKGROUND

Inflammatory processes are key drivers of bronchopulmonary dysplasia (BPD), a chronic lung disease in preterm infants. In a large sample, we verify previously reported associations of genetic variants of immunology-related genes with BPD.

METHODS

Preterm infants with a gestational age ≤32 weeks from PROGRESS and the German Neonatal Network (GNN) were included. Through a consensus case/control definition, 278 BPD cases and 670 controls were identified. We identified 49 immunity-related genes and 55 single-nucleotide polymorphisms (SNPs) previously associated with BPD through a comprehensive literature survey. Additionally, a quantitative genetic association analysis regarding oxygen supplements, mechanical ventilation, and continuous positive air pressure (CPAP) was performed.

RESULTS

Five candidate SNPs were nominally associated with BPD-related phenotypes with effect directions not conflicting the original studies: rs11265269-CRP, rs1427793-NUAK1, rs2229569-SELL, rs1883617-VNN2, and rs4148913-CHST3. Four of these genes are involved in cell adhesion. Extending our analysis to all well-imputed SNPs of all candidate genes, the strongest association was rs45538638-ABCA3 with CPAP (p = 4.9 × 10^-7, FDR = 0.004), an ABC transporter involved in surfactant formation.

CONCLUSIONS

Most of the previously reported associations could not be replicated. We found additional support for SNPs in CRP, NUAK1, SELL, VNN2, and ABCA3. Larger studies and meta-analyses are required to corroborate these findings.

IMPACT

Larger cohort for improved statistical power to detect genetic associations with bronchopulmonary dysplasia (BPD). Most of the previously reported genetic associations with BPD could not be replicated in this larger study. Among investigated immunological relevant candidate genes, additional support was found for variants in genes CRP, NUAK1, SELL, VNN2, and CHST3, four of them related to cell adhesion. rs45538638 is a novel candidate SNP in reported candidate gene ABC-transporter ABCA3. Results help to prioritize molecular candidate pathomechanisms in follow-up studies.

Genetic and Epidemiological Similarities, and Differences Between Postoperative Intraperitoneal Adhesion Development and Other Benign Fibro-proliferative Disorders

Intraperitoneal adhesions complicate over half of abdominal-pelvic surgeries with immediate, short, and long-term sequelae of major healthcare concern. The pathogenesis of adhesion development is similar to the pathogenesis of wound healing in all tissues, which if unchecked result in production of fibrotic conditions. Given the similarities, we explore the published literature to highlight the similarities in the pathogenesis of intra-abdominal adhesion development (IPAD) and other fibrotic diseases such as keloids, endometriosis, uterine fibroids, bronchopulmonary dysplasia, and pulmonary, intraperitoneal, and retroperitoneal fibrosis. Following a literature search using PubMed database for all relevant English language articles up to November 2020, we reviewed relevant articles addressing the genetic and epidemiological similarities and differences in the pathogenesis and pathobiology of fibrotic diseases. We found genetic and epidemiological similarities and differences between the pathobiology of postoperative IPAD and other diseases that involve altered fibroblast-derived cells. We also found several genes and single nucleotide polymorphisms that are up- or downregulated and whose products directly or indirectly increase the propensity for postoperative adhesion development and other fibrotic diseases. An understanding of the similarities in pathophysiology of adhesion development and other fibrotic diseases contributes to a greater understanding of IPAD and these disease processes. At a very fundamental level, blocking changes in the expression or function of genes necessary for the transformation of normal to altered fibroblasts may curtail adhesion formation and other fibrotic disease since this is a prerequisite for their development. Similarly, applying measures to induce apoptosis of altered fibroblast may do the same; however, apoptosis should be at a desired level to simultaneously ameliorate development of fibrotic diseases while allowing for normal healing. Scientists may use such information to develop pharmacologic interventions for those most at risk for developing these fibrotic conditions.

Vascular endothelial growth factor polymorphism rs2010963 status does not affect patent ductus arteriosus incidence or cyclooxygenase inhibitor treatment success in preterm infants

BACKGROUND

Vascular endothelial growth factor is critically involved in ductus arteriosus closure. Polymorphisms in the vascular endothelial growth factor gene have been associated with several diseases in neonates and adults.

AIM

Herein, we investigated if vascular endothelial growth factor polymorphism rs2010963 status is associated with patent ductus arteriosus incidence and/or pharmacological treatment success.

METHODS

We assessed rs2010963 status in 814 preterm infants (<1500 g birth weight) by means of restriction fragment length polymorphism analysis. DNA samples were obtained from dry-spot cards used for the German national newborn screening program. Clinical data were obtained by retrospective chart review.

RESULTS

We could not find any statistically significant difference in the incidence of patent ductus arteriosus depending on vascular endothelial growth factor rs2010963 polymorphism status. Furthermore, no statistically significant associations between vascular endothelial growth factor polymorphism rs2010963 status and cyclooxygenase inhibitor treatment success were observed.

CONCLUSION

Our results indicate that there is no association between vascular endothelial growth factor polymorphism rs2010963 status and the occurrence of patent ductus arteriosus or the response to cyclooxygenase inhibitor treatment in a large cohort of preterm infants. Additional studies are needed to determine the role of genetic factors on patent ductus arteriosus incidence and treatment response.

Immune System Regulation Affected by a Murine Experimental Model of Bronchopulmonary Dysplasia: Genomic and Epigenetic Findings

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common cause of abrupted lung development after preterm birth. BPD may lead to increased rehospitalization, more severe and frequent respiratory infections, and life-long reduced lung function. The gene regulation in lungs with BPD is complex, with various genetic and epigenetic factors involved.

OBJECTIVES

The aim of this study was to examine the regulatory relation between gene expression and the epigenome (DNA methylation) relevant for the immune system after hyperoxia followed by a recovery period in air using a mouse model of BPD.

METHODS

Newborn mice pups were subjected to an immediate hyperoxic condition from birth and kept at 85% O2 levels for 14 days followed by a 14-day period in room air. Next, mice lung tissue was used for RNA and DNA extraction with subsequent microarray-based assessment of lung transcriptome and supplementary methylome analysis.

RESULTS

The immune system-related transcriptomeregulation was affected in mouse lungs after hyperoxia. A high proportion of genes relevant in the immune system exhibited significant expression alterations, e.g., B cell-specific genes central to the cytokine-cytokine receptor interaction, the PI3K-AKT, and the B cell receptor signaling pathways. The findings were accompanied by significant DNA hypermethylation observed in the PI3K-AKT pathway and immune system-relevant genes.

CONCLUSIONS

Oxygen damage could be partly responsible for the increased susceptibility and abnormal response to respiratory viruses and infections seen in premature babies with BPD through dysregulated genes.

Hyperoxia induces epigenetic changes in newborn mice lungs

Supplemental oxygen exposure is a risk factor for the development of bronchopulmonary dysplasia (BPD). Reactive oxygen species may damage lung tissue, but hyperoxia also has the potential to alter genome activity via changes in DNA methylation. Understanding the epigenetic potential of hyperoxia would enable further improvement of the therapeutic strategies for BPD. Here we aimed to identify hyperoxia-related alterations in DNA methylation, which could affect the activity of crucial genetic pathways involved in the development of hyperoxic lung injury. Newborn mice (n = 24) were randomized to hyperoxia (85% O₂) or normoxia groups for 14 days, followed by normoxia for the subsequent 14 days. The mice were sacrificed on day 28, and lung tissue was analyzed using microarrays developed for the assessment of genome methylation and expression profiles. The mean DNA methylation level was higher in the hyperoxia group than the normoxia group. The analysis of specific DNA fragments revealed hypermethylation of > 1000 gene promoters in the hyperoxia group, confirming the presence of the DNA-hypermethylation effect of hyperoxia. Further analysis showed significant enrichment of the TGF-β signaling pathway (p = 0.0013). The hypermethylated genes included Tgfbr1, Crebbp, and Creb1, which play central roles in the TGF-β signaling pathway and cell cycle regulation. Genome expression analysis revealed in the hyperoxia group complementary downregulation of genes that are crucial for cell cycle regulation (Crebbp, Smad2, and Smad3). These results suggest the involvement of the methylation of TGF-β pathway genes in lung tissue reaction to hyperoxia. The data also suggest that hyperoxia may be a programming factor in newborn mice.

Association of cytokine gene polymorphisms with bronchopulmonary dysplasia in Han Chinese newborns

OBJECTIVE

To investigate the association of 14 cytokine gene polymorphisms with bronchopulmonary dysplasia (BPD) among Han Chinese newborns. The 14 polymorphisms investigated were IL18 rs1946519, rs1946518, rs187238, rs360718, and rs360717 polymorphisms, IL10 rs3024493 polymorphism, IL6 rs1800795, rs1800796, and rs1800797 polymorphisms, TNF rs361525 and rs1800629 polymorphisms, and TGFB1 rs1800469, rs1800468, and rs1800471 polymorphisms.

WORKING HYPOTHESIS

The polymorphisms could be associated with the risk of BPD among Han Chinese newborns.

STUDY DESIGN, PATIENT-SUBJECT SELECTION, AND METHODOLOGY

This is a retrospective study. Genotyping of these polymorphisms were performed on BPD cases (N = 1022) and non-BPD controls (N = 1039) who were ascertained using the established Jobe and Bancalari criteria. The odds ratios (ORs) of polymorphisms whose genotype distribution in the controls fulfilled the Hardy-Weinberg equilibrium (HWE) were calculated to evaluate the strengths of genetic association.

RESULTS

Genotype distributions of IL6 rs1800795 and rs1800797 polymorphisms deviated significantly from HWE and were omitted from the analysis. Among the 12 remaining polymorphisms, only TNF rs361525 polymorphism demonstrated a statistically significant association with BPD risk. The heterozygous GA genotype of TNF rs361525 polymorphism showed an OR of 1.932 (1.512-2.470), while the homozygous AA variant genotype showed an OR of 2.927 (1.216-7.048) (P = 0.000 and P = 0.017, respectively). Besides, the allelic OR was also analyzed, and it was found that the variant A allele of TNF rs361525 polymorphism showed an OR of 2.146 (1.718-2.680) (P = 0.000).

CONCLUSION

TNF rs361525 polymorphism could influence BPD risk among Han Chinese newborns.

A Pathogenic Relationship of Bronchopulmonary Dysplasia and Retinopathy of Prematurity? A Review of Angiogenic Mediators in Both Diseases

Bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) are common and significant morbidities of prematurely born infants. These diseases have in common altered and pathologic vascular formation in the face of incomplete organ development. Therefore, it is reasonable to question whether factors affecting angiogenesis could have a joint pathogenic role for both diseases. Inhibition or induced expression of a single angiogenic factor is unlikely to be 100% causative or protective of either of BPD or ROP. It is more likely that interactions of multiple factors leading to disordered angiogenesis are present, increasing the likelihood of common pathways in both diseases. This review explores this possibility by assessing the evidence showing involvement of specific angiogenic factors in the vascular development and maldevelopment in each disease. Theoretical interactions of specific factors mutually contributing to BPD and ROP are proposed and, where possible, a timeline of the proposed relationships between BPD and ROP is developed. It is hoped that future research will be inspired by the theories put forth in this review to enhance the understanding of the pathogenesis in both diseases.

The significance of IL-1β +3953C>T, IL-6 -174G>C and -596G>A, TNF-α -308G>A gene polymorphisms and 86 bp variable number tandem repeat polymorphism of IL-1RN in bronchopulmonary dysplasia in infants born before 32 weeks of gestation

Introduction

Bronchopulmonary dysplasia (BPD) is a chronic lung disease that affects primarily preterm infants. Genetic factors are also taken into consideration in the pathogenesis of BPD. Genetic predispositions to higher production of inflammation mediators seem to be crucial.

Material and methods

The aim of this study was to evaluate the possible relationship between polymorphisms: interleukin-1β +3953 C>T, interleukin-6 -174 G>C and -596 G>A, tumour necrosis factor -308 G>A and interleukin-1RN VNTR 86bp and the occurrence of BPD in a population of 100 preterm infants born from singleton pregnancy, before 32+0 weeks of gestation, exposed to antenatal steroids therapy, and without congenital abnormalities.

Results

In the study population BPD was diagnosed in 36 (36%) newborns. Among the studied polymorphisms we found the higher prevalence for BPD developing of the following genotypes: 1/2 (OR 1.842 [0.673-5.025] and 2/2 IL-1RN (OR 1.75 [0.418-6.908] 86bpVNTR; GC (2.222 [0.658-8.706]) and CC IL-6 -174G>C (1.6 [0.315-8.314]) and GA (2.753 [0.828-10.64]) and AA (1.5 [0.275-8.067] IL-6 -596G>A), GA 1.509 (0.515-4.301) TNF-α -308G>A. However, these finding were not statistically significant.

Conclusions

Genetic factors are undeniably involved in the pathogenesis of BPD. In the times of individualised therapy finding genes responsible for BPD might allow the development of new treatment strategies. A new way of specific therapy could ensure the reduction of complications connected with BPD and treatment costs.

The genetic predisposition to bronchopulmonary dysplasia

PURPOSE OF REVIEW

Bronchopulmonary dysplasia (BPD) is a prevalent chronic lung disease in premature infants. Twin studies have shown strong heritability underlying this disease; however, the genetic architecture of BPD remains unclear.

RECENT FINDINGS

A number of studies employed different approaches to characterize the genetic aberrations associated with BPD, including candidate gene studies, genome-wide association studies, exome sequencing, integrative omics analysis, and pathway analysis. Candidate gene studies identified a number of genes potentially involved with the development of BPD, but the etiological contribution from each gene is not substantial. Copy number variation studies and three independent genome-wide association studies did not identify genetic variations significantly and consistently associated with BPD. A recent exome-sequencing study pointed to rare variants implicated in the disease. In this review, we summarize these studies' methodology and findings, and suggest future research directions to better understand the genetic underpinnings of this potentially life-long lung disease.

SUMMARY

Genetic factors play a significant role in the development of BPD. Recent studies suggested that rare variants in genes participating in lung development pathways could contribute to BPD susceptibility.

Genetic predisposition to bronchopulmonary dysplasia

The objective of this study is to review the candidate gene and genome-wide association studies relevant to bronchopulmonary dysplasia, and to discuss the emerging understanding of the complexities involved in genetic predisposition to bronchopulmonary dysplasia and its outcomes. Genetic factors contribute much of the variance in risk for BPD. Studies to date evaluating single or a few candidate genes have not been successful in yielding results that are replicated in GWAS, perhaps due to more stringent p-value thresholds. GWAS studies have identified only a single gene (SPOCK2) at genome-wide significance in a European White and African cohort, which was not replicated in two North American studies. Pathway gene-set analysis in a North American cohort confirmed involvement of known pathways of lung development and repair (e.g., CD44 and phosphorus oxygen lyase activity) and indicated novel molecules and pathways (e.g., adenosine deaminase and targets of miR-219) involved in genetic predisposition to BPD. The genetic basis of severe BPD is different from that of mild/moderate BPD, and the variants/pathways associated with BPD vary by race/ethnicity. A pilot study of whole exome sequencing identified hundreds of genes of interest, and indicated the overall feasibility as well as complexity of this approach. Better phenotyping of BPD by severity and pathophysiology, and careful analysis of race/ethnicity is required to gain a better understanding of the genetic basis of BPD. Future translational studies are required for the identification of potential genetic predispositions (rare variants and dysregulated pathways) by next-generation sequencing methods in individual infants (personalized genomics).

Biomarkers in neonatology: the new "omics" of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a complex disorder resulting from gene-environmental interactions. An improved understanding of the pathogenesis of this most common chronic lung disease in infants has been made by utilizing animal models and correlating with human data. Currently, while some (vitamin A, caffeine) pharmacotherapeutic options are being utilized to ameliorate this condition, there is still no specific or effective treatment for BPD. It would be helpful for prognostication and targeted potential novel therapeutic strategies to identify those babies accurately who are at risk for developing this disease. A reliable biomarker would have the capacity to be detected in the initial phase of the disease, to allow early interventions to avoid or minimize the detrimental effects of the disease. This review will focus on human studies performed with the "omic" techniques, specifically genomics, epigenomics, microbiomics, transciptomics, proteomics and metabolomics, and summarize the information available in the literature, as it pertains to biomarker identification for BPD. Using "omics" technologies, investigators have reported markers that have the potential to be used as biomarkers of BPD: SPOCK2, VEGF -624C > G, VEGF -460T > C, mast cells specific markers, miR-219 pathway, miR-152, -30a-3p, -133b, -206, -7, lactate, taurine, trimethylamine-N-oxide, gluconate, myoinositol and alterations in surfactant lipid profile.

Genes Encoding Vascular Endothelial Growth Factor A (VEGF-A) and VEGF Receptor 2 (VEGFR-2) and Risk for Bronchopulmonary Dysplasia

BACKGROUND

Bronchopulmonary dysplasia (BPD) is one of the main consequences of prematurity, with notably high heritability. Vascular endothelial growth factor A (VEGF-A) and its main receptor, vascular endothelial growth factor receptor 2 (VEGFR-2), have been implicated in the pathogenesis of BPD.

OBJECTIVE

To study whether common polymorphisms of the genes encoding VEGF-A and VEGFR-2 are associated with BPD.

METHODS

In this association study, six tagging single nucleotide polymorphism (tSNPs) for VEGFA and 25 tSNPs for VEGFR2 were genotyped in a prospectively collected, genetically homogeneous discovery population of 160 infants (44 infants with grade 2-3 BPD) born before 30 completed gestational weeks. The replication population of 328 infants included 120 cases of BPD.

RESULTS

VEGFR2 SNP rs4576072 was associated with BPD grade 2-3 with a minor allele frequency in 23.9% of the cases compared to 9.1% in controls (p = 0.0005, odds ratio 3.15, 95% CI: 1.62-6.12) in the discovery population. This association was not observed in the more heterogeneous replication population.

CONCLUSIONS

In line with the results of recent large-scale genetic studies, our findings indicate that common polymorphisms of the genes encoding VEGF-A and VEGFR-2 are not consistently associated with BPD. This finding does not rule out the involvement of VEGFA and VEGFR2 in BPD pathogenesis since, in addition to common variations within the gene region, other mechanisms also play important roles in the regulation of gene function.

Association of a vascular endothelial growth factor polymorphism with the development of bronchopulmonary dysplasia in Japanese premature newborns

Our objective was to correlate vascular endothelial growth factor (VEGF) genetic polymorphisms with the risk of bronchopulmonary dysplasia (BPD) development in premature newborns. Fifty-five newborns with BPD (BPD: median gestational age [GA]: 27 weeks, birthweight [BW]: 786 g) and 42 newborns without BPD (non-BPD: median GA: 29 weeks, BW: 1,165 g), who were born at <32 weeks gestational age and were admitted to Kobe University Hospital, were included. BPD was defined as oxygen dependency at 36 weeks postmenstrual age. Genomic DNA was extracted from the umbilical cord, cord blood, or buccal mucosa. Six VEGF genotypes (-1498T > C, -1154G > A, -634C > G, -7C > T, 936C > T, and 1612G > A) were determined by DNA sequencing. Clinical characteristics, and allele and genotype frequencies of VEGF in the BPD and non-BPD groups were analyzed. G allele frequencies in -634C > G of the BPD group were significantly higher than in the non-BPD group (66.4% vs. 50%, P = 0.02). -634C > G genotype distributions differed significantly between the BPD and non-BPD groups (BPD: CC 7%/CG 53%/GG 40%; non-BPD: CC 24%/CG 52%/GG 24%; P = 0.04). Multivariate logistic regression showed that duration of ventilation, VEGF-634G > C G alleles, and male gender were independent risk factors for BPD. In conclusion, polymorphism VEGF -634C > G may influence the risk of BPD.

Are preterm infants at high altitude at greater risk for the development of bronchopulmonary dysplasia?

OBJECTIVES

To assess the association between altitudes of neonatal intensive care units (NICUs) and the incidence of bronchopulmonary dysplasia (BPD) in preterm infants.

METHODS

Data from infants born at <32 weeks' gestation admitted to NICUs at high altitude (2200 m above sea level) between 2002 and 2011 were analyzed and compared with the data from a lower altitude NICU in Saudi Arabia.

RESULTS

Of 942 preterm infants admitted to the high altitude NICUs, 266 (28.2%) infants developed BPD. The incidence of BPD was significantly higher in infants admitted to the NICU at high altitude than in those at lower altitude (28.2 vs. 17.7%, respectively, p = 0.003). In multivariable analysis, high altitude was significantly associated with a higher risk of BPD (odds ratio: 0.54, 95% confidence interval: 0.36-0.81).

CONCLUSION

Findings suggest that high altitude may increase the risk of BPD development among preterm infants.

Human amniotic fluid stem cells protect rat lungs exposed to moderate hyperoxia

BACKGROUND

Treatment of bronchopulmonary dysplasia (BPD) remains as yet an unmet clinical need and recently stem cells have been proposed as a therapeutic tool in animal models. We investigated the role of amniotic fluid stem cells (AFS) in an adult rat model of hyperoxia lung injury.

METHODS

Fifty Sprague-Dawley rats were, at birth, randomly exposed to moderate hyperoxia or room air for 14 days and a single dose of human amniotic fluid stem (hAFS) or human Fibroblasts (hF), cells was delivered intratracheally (P21). At P42 animals were euthanized and lung tissue examined using histology, immunohistochemistry, PCR, and ELISA. hAFS cells characterization and homing were studied by immunofluorescence.

RESULTS

In rats treated with hAFS and hF cells 16S human rRNA fragment was detected. Despite a low level of pulmonary hAFS cell retention (1.43 ± 0.2% anti-human-mitochondria-positive cells), the lungs of the treated animals revealed higher secondary crest numbers and lower mean linear intercept and alveolar size, than those exposed to hyperoxia, those left untreated or treated with hF cells. Except for those treated with hAFS cells, moderate hyperoxia induced an increase in protein content of IL-6, IL-1β, as well as IF-γ and TGF-1β in lung tissues. High VEGF expression and arrangement of capillary architecture in hAFS cell group were also detected.

CONCLUSIONS

Treatment with hAFS cells has a reparative potential through active involvement of cells in alveolarization and angiogenesis. A downstream paracrine action was also taken into account, in order to understand the immunodulatory response.

Association of surfactant protein B gene polymorphisms (C/A-18, C/T1580, intron 4 and A/G9306) and haplotypes with bronchopulmonary dysplasia in chinese han population

This study aimed to investigate the association between surfactant protein B (SP-B) polymorphisms and bronchopulmonary dysplasia (BPD) in Chinese Han infants. We performed a casecontrol study including 86 infants with BPD and 156 matched controls. Genotyping was performed by sequence specific primer-polymerase chain reaction (PCR) and haplotypes were reconstructed by the fastPHASE software. The results showed that significant differences were detected in the genotype distribution of C/A-18 and intron 4 polymorphisms of SP-B gene between cases and controls. No significant differences were detected in the genotype distribution of C/T1580 or A/G9306 between the two groups. Haplotype analysis revealed that the frequency of A-del-C-A haplotype was higher in case group (0.12 to 0.05, P=0.003), whereas the frequency of C-inv-C-A haplotype was higher in control group (0.19 to 0.05, P=0.000). In addition, a significant difference was observed in the frequency of C-inv-T-A haplotype between the two groups. It was concluded that the polymorphisms of SP-B intron 4 and C/A-18 could be associated with BPD in Chinese Han infants, and the del allele of intron 4 and A allele of C/A-18 might be used as markers of susceptibility in the disease. Haplotype analysis indicated that the gene-gene interactions would play an important part in determining susceptibility to BPD.

Progress in understanding the genetics of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease in infants. Its treatment imposes considerable healthcare burden and costs in the perinatal and early childhood period and patients are usually left with lifelong deficits in lung function. Evidence exists for different pathophysiologic pathways that can promote the structural changes that characterize BPD, including the impairment in alveolarization; however, there is increasing interest regarding heritable factors that may predispose very low birth weight infants to BPD. Our review focuses on recent publications that have investigated genetic factors that may potentially contribute to such reported heritability. These publications point us toward some possible genomic candidates for further study, but certainly do not identify any particular gene or gene pathway that would be inferred to be contributing substantially to the underlying etiology of BPD.

Regional variation on rates of bronchopulmonary dysplasia and associated risk factors

Background. An abnormally high incidence (44%) of bronchopulmonary dysplasia with variations in rates among cities was observed in Colombia among premature infants. Objective. To identify risk factors that could explain the observed high incidence and regional variations of bronchopulmonary dysplasia. Study Design. A case-control study was designed for testing the hypothesis that differences in the disease rates were not explained by differences in city-of-birth specific population characteristics or by differences in respiratory management practices in the first 7 days of life, among cities. Results. Multivariate analysis showed that premature rupture of membranes, exposure to mechanical ventilation after received nasal CPAP, no surfactant exposure, use of rescue surfactant (instead of early surfactant), PDA, sepsis and the median daily FIO(2), were associated with a higher risk of dysplasia. Significant differences between cases and controls were found among cities. Models exploring for associations between city of birth and dysplasia showed that being born in the highest altitude city (Bogotá) was associated with a higher risk of dysplasia (OR 1.82 95% CI 1.31-2.53). Conclusions. Bronchopulmonary dysplasia was manly explained by traditional risk factors. Findings suggest that altitude may play an important role in the development of this disease. Prenatal steroids did not appear to be protective at high altitude.

Definition and outpatient management of the very low-birth-weight infant with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), also known as chronic lung disease of prematurity, is the major cause of pulmonary disease in infants. The pathophysiology and management of BPD have evolved over the past four decades as improved neonatal intensive care unit (NICU) modalities have increased survival rates. The likelihood for developing BPD increases with the degree of prematurity and reaches 25-35% in very low-birth-weight and extremely low-birth-weight infants. BPD affects many organ systems, and infants with BPD are at increased risk for rehospitalization and numerous complications following NICU discharge. The management of BPD and medically related problems, particularly during the first 2 years of life, remains a continuing challenge for parents and healthcare providers. It is important that a multidisciplinary team consisting of the neonatologist/attending physician, primary care physician, and other specialized support staff work in concert and meet regularly to provide continuity of care and accurate patient assessments.

IL-18R1 and IL-18RAP SNPs may be associated with bronchopulmonary dysplasia in African-American infants

INTRODUCTION

The genetic contribution to the development of bronchopulmonary dysplasia (BPD) in prematurely born infants is substantial, but information related to the specific genes involved is lacking.

RESULTS

Genotype analysis revealed, after multiple comparisons correction, two significant single-nucleotide polymorphism (SNPs), rs3771150 (IL-18RAP) and rs3771171 (IL-18R1), in African Americans (AAs) with BPD (vs. AAs without BPD; q < 0.05). No associations with Caucasian (CA) BPD, AA or CA respiratory distress syndrome (RDS), or prematurity in either AAs or CAs were identified with these SNPs. Respective frequencies were 0.098 and 0.093 in infants without BPD and 0.38 for each SNP in infants with BPD. In the replication set (82 cases; 102 controls), the P values were 0.012 for rs3771150 and 0.07 for rs3771171. Combining P values using Fisher's method, overall P values were 8.31 × 10(-7) for rs3771150 and 6.33 × 10(-6) for rs3771171.

DISCUSSION

We conclude that IL-18RAP and IL-18R1 SNPs identify AA infants at risk for BPD. These genes may contribute to AA BPD pathogenesis via inflammatory-mediated processes and require further study.

METHODS

We conducted a case-control SNP association study of candidate genes (n = 601) or 6,324 SNPs in 1,091 prematurely born infants with gestational age <35 weeks, with or without neonatal lung disease including BPD. BPD was defined as a need for oxygen at 28 days.

Identification of SPOCK2 as a susceptibility gene for bronchopulmonary dysplasia

RATIONALE

Bronchopulmonary dysplasia is the most common chronic respiratory disease in premature infants. Genetic factors might contribute to bronchopulmonary dysplasia susceptibility.

OBJECTIVES

To identify genetic variants involved in bronchopulmonary dysplasia through a genome-wide association study.

METHODS

We prospectively evaluated 418 premature neonates (gestational age <28 wk), of whom 22% developed bronchopulmonary dysplasia. Two discovery series were created, using a DNA pooling strategy in neonates from white and African ancestry. Polymorphisms associated with the disease were confirmed in an independent replication population. Genes were then explored by fine mapping and associations were replicated in an external Finnish population of 213 neonates. Validated genes expression patterns were studied in rat lung, after air or hyperoxia exposure.

MEASUREMENTS AND MAIN RESULTS

SPOCK2 gene was identified by both discovery series. The most significant polymorphism (rs1245560; P = 1.66 × 10(-7)) was confirmed by individual genotyping, and in the replication population (P = 0.002). Fine mapping confirmed the association of rs1245560 with bronchopulmonary dysplasia in both white and African populations with adjusted odds ratios of 2.96 (95% confidence interval [CI], 1.37-6.40) and 4.87 (95% CI, 1.88-12.63), respectively. In white neonates, rs1049269 was also associated with the disease (odds ratio, 3.21; 95% CI, 1.51-6.82). These associations were replicated in the Finnish population. In newborn rat lungs, SPOCK2 mRNA levels markedly increased during the alveolar stage of lung development. After rat exposure to hyperoxia, SPOCK2 expression increased relative to air-exposed controls.

CONCLUSIONS

We identified SPOCK2 as a new possible candidate susceptibility gene for bronchopulmonary dysplasia. Its lung expression pattern points toward a potential role in alveolarization.

Targeting inflammation to prevent bronchopulmonary dysplasia: can new insights be translated into therapies?

Bronchopulmonary dysplasia (BPD) frequently complicates preterm birth and leads to significant long-term morbidity. Unfortunately, few therapies are known to effectively prevent or treat BPD. Ongoing research has been focusing on potential therapies to limit inflammation in the preterm lung. In this review we highlight recent bench and clinical research aimed at understanding the role of inflammation in the pathogenesis of BPD. We also critically assess currently used therapies and promising developments in the field.

A polymorphism in the macrophage migration inhibitory factor promoter is associated with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a common adverse outcome of prematurity, causing severe morbidity and mortality. The cytokine macrophage migration inhibitory factor (MIF) has been recently shown to favor murine fetal lung development. In this prospective study, we evaluate the expression of MIF in the lung and in the serum of preterm infants (n = 50) and investigate whether the -173 G/C MIF promoter polymorphism is associated with the risk of BPD (n = 103). MIF was highly expressed in lung tissue from preterm infants. Serum MIF levels were measured by ELISA at d 1 after birth. MIF levels were increased [median (interquartile range), 71.01 (44.9-162.3) ng/mL], particularly in those infants with RDS [110.4 (59.4-239.2) ng/mL] compared with healthy adults [2.4 (1.2-5.0) ng/mL], (p < 0.001). The MIF -173*C allele, which predisposes to higher MIF production, was associated with a lower incidence of BPD (OR, 0.2; 95% CI, 0.04-0.93), independently from mechanical ventilation and oxygen exposure (p = 0.03). In conclusion, these data show that MIF expression is increased in lung and serum of preterm infants and suggest that the high producing MIF -173*C allele may be a protective factor for BPD.

Preterm birth and respiratory disease in later life

Chronic respiratory diseases are a common complication of preterm birth, particularly among very immature infants or those suffering from bronchopulmonary dysplasia. Major progress in the treatment of preterm newborns has changed the pattern of late respiratory complications. The major respiratory problem in infancy and early childhood is respiratory exacerbations caused by infections (particularly viral ones), which need hospitalization. The symptoms become mild in school-age children; however, a group of children still present with chronic airway obstruction defined by recurrent episodes of wheezing and decreased lung function tests (decreased forced expiratory volume). For some preterm infants, particularly those with bronchopulmonary dysplasia, obstructive lung disease persists into adulthood. They are very likely to develop chronic obstructive pulmonary disease or similar disease later in life. In these patients, a program of lung function monitoring and pulmonary prophylaxis by means of elimination of specific risk factors in adulthood is advisable.

Genetics of bronchopulmonary dysplasia in the age of genomics

PURPOSE OF REVIEW

According to recent evidence, susceptibility to bronchopulmonary dysplasia (BPD) in preterm infants is predominantly inherited. The purpose of this review is to discuss current published genetic association studies in light of the accumulated knowledge in genomics.

RECENT FINDINGS

Major advances in the development of next-generation genotyping and sequencing platforms, statistical methodologies, inventories of functional outcome of some common genetic polymorphisms and large-scale cataloguing of genetic variability among many of the world's ethnic populations have greatly facilitated the study of polygenic conditions. For BPD, genetic-association studies have primarily focused on components of innate (e.g. first-line) immune and antioxidant defences, mechanisms of vascular and lung remodelling, and surfactant proteins. However, studies have been limited in sample size and therefore fraught with a high probability of false-positive and false-negative associations. Nonetheless, candidate gene associations have indicated some novel biological pathways and provide a conceptual framework for the design of larger, collaborative population-based studies.

SUMMARY

Although studies to date have not been able to identify reproducible genetic risk markers for BPD, they have directed us towards new, promising research avenues.

Lack of association between FXIII-Val34Leu, FVII-323 del/ins, and transforming growth factor beta1 (915G/T) gene polymorphisms and bronchopulmonary dysplasia: a single-center study

Bronchopulmonary dysplasia (BPD) is a multifactorial disease of preterm infants that is characterized by airway injury, inflammation, and parenchymal remodeling. Extravascular fibrin deposits in septae and alveoli due to the altered fibrin turnover are the pathological hallmarks of BPD that strongly indicates the importance of the imbalance in the competing activities of coagulation and fibrinolysis. Activation of the coagulation cascade leads to intraalveolar fibrin deposition in many inflammatory pulmonary disorders. Increased fibrin formation or decreased fibrinolysis may cause extravascular fibrin deposition. We evaluated the association between FXIII-Val34Leu, FVII-323 del/ins, and transforming growth factor beta1 (TGF-beta(1)) (915G/T) gene polymorphisms in patients with BPD. The study group consisted of 98 preterm infants with BPD. Ninety-four of the 192 preterm neonates were without BPD and sampled for the control group. Restriction fragment size analyses were performed by examining digested PCR products for FXIII-Val34Leu, FVII-323 del/ins, and TGF-beta(1) (915G/C) genotypes. No significant associations were found between FXIII-Val34Leu, FVII-323 del/ins, TGF-beta(1) (915G/C) gene polymorphisms and BPD phenotype in our population. Further studies with other genes are required for the identification of molecular predisposing factors for BPD that may help in the development of new treatments and hence might allow for targeting of this treatment to a "high-risk" subgroup, reducing unnecessary exposure to potentially harmful therapies.

Epidemiology of bronchopulmonary dysplasia

First described more than 40 years ago, bronchopulmonary dysplasia (BPD) remains one of the most serious and vexing challenges in the care of very preterm infants. Affecting approximately one-quarter of infants born <1500g birth weight, BPD is associated with prolonged neonatal intensive care unit hospitalization, greater risk of neonatal and post-neonatal mortality and a host of associated medical and neurodevelopmental sequelae. This seminar focuses on the epidemiology and definition of BPD as well as the current evidence pertaining to a number of potential preventive treatments for BPD: non-invasive respiratory support technologies, inhaled nitric oxide, vitamin A, and caffeine.

Can we improve outcome of congenital diaphragmatic hernia?

This review gives an overview of the disease spectrum of congenital diaphragmatic hernia (CDH). Etiological factors, prenatal predictors of survival, new treatment strategies and long-term morbidity are described. Early recognition of problems and improvement of treatment strategies in CDH patients may increase survival and prevent secondary morbidity. Multidisciplinary healthcare is necessary to improve healthcare for CDH patients. Absence of international therapy guidelines, lack of evidence of many therapeutic modalities and the relative low number of CDH patients calls for cooperation between centers with an expertise in the treatment of CDH patients. The international CDH Euro-Consortium is an example of such a collaborative network, which enhances exchange of knowledge, future research and development of treatment protocols.