Angiogenic Factors in Cord Blood of Preterm Infants Predicts Subsequently Developing Bronchopulmonary Dysplasia

Systemic Cytokines in Retinopathy of Prematurity

Retinopathy of prematurity (ROP), a vasoproliferative vitreoretinal disorder, is the leading cause of childhood blindness worldwide. Although angiogenic pathways have been the main focus, cytokine-mediated inflammation is also involved in ROP etiology. Herein, we illustrate the characteristics and actions of all cytokines involved in ROP pathogenesis. The two-phase (vaso-obliteration followed by vasoproliferation) theory outlines the evaluation of cytokines in a time-dependent manner. Levels of cytokines may even differ between the blood and the vitreous. Data from animal models of oxygen-induced retinopathy are also valuable. Although conventional cryotherapy and laser photocoagulation are well established and anti-vascular endothelial growth factor agents are available, less destructive novel therapeutics that can precisely target the signaling pathways are required. Linking the cytokines involved in ROP to other maternal and neonatal diseases and conditions provides insights into the management of ROP. Suppressing disordered retinal angiogenesis via the modulation of hypoxia-inducible factor, supplementation of insulin-like growth factor (IGF)-1/IGF-binding protein 3 complex, erythropoietin, and its derivatives, polyunsaturated fatty acids, and inhibition of secretogranin III have attracted the attention of researchers. Recently, gut microbiota modulation, non-coding RNAs, and gene therapies have shown promise in regulating ROP. These emerging therapeutics can be used to treat preterm infants with ROP.

Forced expiratory flows and diffusion capacity in infants born from mothers with pre-eclampsia

RATIONALE

Animal models suggest pre-eclampsia (Pre-E) affects alveolar development, but data from humans are lacking.

OBJECTIVE

Assess the impact of Pre-E on airway function, diffusion capacity, and respiratory morbidity in preterm and term infants born from mothers with Pre-E.

METHODS

Infants born from mothers with and without Pre-E were recruited for this study; term and preterm infants were included in both cohorts. Respiratory morbidity in the first 12 months of life was assessed through monthly phone surveys. Raised volume rapid thoracoabdominal compression and measurement of diffusion capacity of the lung to carbon monoxide (DLCO) were performed at 6 months corrected age.

MEASUREMENTS AND MAIN RESULTS

There were 146 infants in the Pre-E cohort and 143 in the control cohort. The Pre-E cohort was further divided into nonsevere (N = 41) and severe (N = 105) groups. There was no significant difference in DLCO and DLCO/alveolar volume among the three groups. Forced vital capacity was similar among the three groups, but the nonsevere Pre-E group had significantly higher forced expiratory flows than the other two groups. After adjusting for multiple covariates including prematurity, the severe Pre-E group had a lower risk for wheezing in the first year of life compared to the other two groups.

CONCLUSIONS

Pre-E is not associated with reduced DLCO, lower forced expiratory flows, or increased wheezing in the first year of life. These results differ from animal models and highlight the complex relationships between Pre-E and lung function and respiratory morbidity in human infants.

Plasma apelin and vascular endothelial growth factor levels in preterm infants: relationship to neonatal respiratory distress syndrome

AIM

The study aimed to determine the association between cord plasma levels of apelin and vascular endothelial growth factor (VEGF) with respiratory distress syndrome (RDS) in preterm infants.

METHODS

This case-control study included 120 preterm infants admitted to the neonatal intensive care unit of our hospital between January 2019 and January 2020. The infants were divided into RDS (n = 60) and non-RDS groups (n = 60). The cord plasma apelin and VEGF levels, perinatal characteristics, and neonatal complications were compared between the two groups.

RESULTS

The plasma apelin levels in the RDS group were significantly higher than in the non-RDS group (158.9 ± 24.8 vs. 125.2 ± 18.2 pg/mL, respectively), whereas VEGF levels in the non-RDS group were significantly higher than in the RDS group (187.4 ± 28.5 vs. 245.1 ± 44.8 pg/mL, respectively) (both p < .001). Infants with more severe RDS had higher plasma apelin levels and lower plasma VEGF levels. In the receiver operating characteristic curve analysis for the prediction of RDS, a cutoff of 148.4 pg/mL for apelin level yielded a sensitivity of 63.3% and a specificity of 95.0%, whereas a cutoff of 214.2 pg/mL for VEGF level showed a sensitivity of 86.7% and a specificity of 75.0%. Apelin levels were negatively correlated with VEGF levels in infants with RDS (r = 0.84, p < .001).

CONCLUSION

Differences in cord plasma apelin and VEGF levels may aid in the early diagnosis and treatment of RDS in preterm infants.

Molecular mechanisms underlying hyperoxia-induced lung fibrosis

Supplemental oxygen is often used to treat newborns with respiratory disorders. Exposure to high concentration of oxygen and long-term oxygen causes inflammation and acute lung injury. The acute inflammatory phase is followed by a fibroproliferative repair phase, leading to lung fibrosis. Many infants with lung fibrosis develop significant respiratory morbidities including reactive airways dysfunction and obstructive lung disease during childhood. Despite the absence of effective treatments and the incomplete understanding regarding mechanisms underlying fibrosis, extensive literature regarding lung fibrosis from in vitro and in vivo hyperoxia-exposed models is available. In this review, we discuss molecular mediators and signaling pathways responsible for increased fibroblast proliferation and collagen production, excessive extracellular matrix accumulation, and eventually, lung fibrosis. We discuss each of these mediators separately to facilitate clear understanding as well as significant interactions occurring among these molecular mediators and signaling pathways.

The value of plasma insulin-like growth factor 1 and interleukin-18 in the diagnosis of bronchopulmonary dysplasia in premature infants

OBJECTIVE

To explore the diagnostic value of IGF-1 and IL-18 in premature infants with BPD.

METHODS

Through a prospective observational study, the serum samples of infants in the BPD group and the non-BPD group were collected at different targeted time points, and the serum IGF-1 and IL-18 concentrations were dynamically monitored by ELISA. The Student t-test and one-way analysis of variance were adopted to analyze data, and the receiver operating characteristic (ROC) curve was used to test the diagnostic value.

RESULT

A total of 90 VLBW premature infants admitted to NICU between January 2020 and 2021 were finally included. Compared with the non-BPD group, infants diagnosed with BPD had a significantly lower serum concentration of IGF-1 (P < 0.05) but a higher level of IL-18 (P < 0.05) on days 1, 7, 14, and 28 after birth. With the ROC curve analysis, the serum concentration IGF-1 on day 14 and IL-18 on day 28 reported high sensitivity and specificity to predict the risk of BPD (IGF-1: sensitivity: 89.29%, specificity: 77.78%, AUC: 0.8710; IL-18: sensitivity: 53.57%, specificity: 83.33%, AUC: 0.7887). And more substantial predictive power was found in combined analysis of IGF-1 and serum IL-18 on day 14: the sensitivity was 91.07% and the specificity was 83.33%, with the AUC of 0.9142.

CONCLUSION

IGF-1 and IL-18 might be closely involved in the occurrence and development of BPD. The serum concentration of IGF-1 combined with IL-18 could be potentially sensitive markers for the early diagnosis and severity of BPD.

MicroRNA-214 promotes alveolarization in neonatal rat models of bronchopulmonary dysplasia via the PlGF-dependent STAT3 pathway

BACKGROUND

Recently, the role of several microRNAs (miRNAs or miRs) in pulmonary diseases has been described. The molecular mechanisms by which miR-214 is possibly implicated in bronchopulmonary dysplasia (BPD) have not yet been addressed. Hence, this study aimed to investigate a putative role of miR-214 in alveolarization among preterm neonates with BPD.

METHODS

Microarray-based gene expression profiling data from BPD was employed to identify differentially expressed genes. A BPD neonatal rat model was induced by hyperoxia. Pulmonary epithelial cells were isolated from rats and exposed to hyperoxia to establish cell injury models. Gain- and loss-of-function experiments were performed in BPD neonatal rats and hyperoxic pulmonary epithelial cells. MiR-214 and PlGF expression in BPD neonatal rats, and eNOS, Bcl-2, c-myc, Survivin, α-SMA and E-cadherin expression in hyperoxic pulmonary epithelial cells were measured using RT-qPCR and Western blot analysis. The interaction between PlGF and miR-214 was identified using dual luciferase reporter gene and RIP assays. IL-1β, TNF-a, IL-6, ICAM-1 and Flt-1 expression in the rat models was measured using ELISA.

RESULTS

The lung tissues of neonatal rats with BPD showed decreased miR-214 expression with elevated PlGF expression. PlGF was found to be a target of miR-214, whereby miR-214 downregulated PlGF to inactivate the STAT3 pathway. miR-214 overexpression or PlGF silencing decreased the apoptosis of hyperoxic pulmonary epithelial cells in vitro and restored alveolarization in BPD neonatal rats.

CONCLUSION

Overall, the results demonstrated that miR-214 could facilitate alveolarization in preterm neonates with BPD by suppressing the PlGF-dependent STAT3 pathway.

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.

S-endoglin expression is induced in hyperoxia and contributes to altered pulmonary angiogenesis in bronchopulmonary dysplasia development

Altered pulmonary angiogenesis contributes to disrupted alveolarization, which is the main characteristic of bronchopulmonary dysplasia (BPD). Transforming growth factor β (TGFβ) plays an important role during lung vascular development, and recent studies have demonstrated that endoglin is engaged in the modulation of TGFβ downstream signalling. Although there are two different isoforms of endoglin, L- and S-endoglin, little is known about the effect of S-endoglin in developing lungs. We analysed the expression of both L- and S-endoglin in the lung vasculature and its contribution to TGFβ-activin-like kinase (ALK)-Smad signalling with respect to BPD development. Hyperoxia impaired pulmonary angiogenesis accompanied by alveolar simplification in neonatal mouse lungs. S-endoglin, phosphorylated Smad2/3 and connective tissue growth factor levels were significantly increased in hyperoxia-exposed mice, while L-endoglin, phosphor-Smad1/5 and platelet-endothelial cell adhesion molecule-1 levels were significantly decreased. Hyperoxia suppressed the tubular growth of human pulmonary microvascular endothelial cells (ECs), and the selective inhibition of ALK5 signalling restored tubular growth. These results indicate that hyperoxia alters the balance in two isoforms of endoglin towards increased S-endoglin and that S-endoglin attenuates TGFβ-ALK1-Smad1/5 signalling but stimulates TGFβ-ALK5-Smad2/3 signalling in pulmonary ECs, which may lead to impaired pulmonary angiogenesis in developing lungs.

Association of serum angiogenic factors with bronchopulmonary dysplasia. The ANGIODYS cohort study

OBJECTIVES

Angiogenic factors may be involved in lung development. To evaluate the relations between maternal and cord blood angiogenic factors (sFlt-1, placental growth factor [PlGF], soluble endogline [sEng], transforming growth factor β [TGF-beta]) and their association with moderate and severe bronchopulmonary dysplasia (BPD) in very preterm growth-restricted infants.

STUDY DESIGN

Prospective monocentric cohort study. Twenty-four mother-child dyads featuring antepartum preeclampsia, intra-uterine growth restriction (IUGR) and birth before 30 weeks' gestation were included. This ensured a 80% power to test whether sFlt-1 maternal levels would be twice as high in cases of BPD as in the absence of BPD.

MAIN OUTCOME MEASURES

Four pro/anti-angiogenic factors from two pathways (sFlt-1, PlGF and sEng, TGF-beta) were measured in maternal serum before delivery (at the time of hospitalization or the day of birth) and in neonates' cord blood. Neonatal outcome was moderate to severe BPD, defined as oxygen requirement for at least 28 days and persistent need for oxygen or ventilatory support at 36 weeks' postmenstrual age.

RESULTS

sFlt-1 levels were positively correlated in maternal serum and cord blood (r_s = 0.83, p < .001) but levels of PlGF and TGF-beta and its receptor sEng were not. Among all the factors studied in cord and maternal blood, none was associated with BPD.

CONCLUSIONS

In IUGR preterm babies born before 30 weeks' gestation from preeclamptic mothers, serum sFlt-1, PlGF and sEng, TGF-β levels were not correlated with BPD. The increased BPD risk in preterm neonates born from preeclamptic mothers cannot be related to high sFlt-1 levels.

Recent advances in our understanding of the mechanisms of late lung development and bronchopulmonary dysplasia

The objective of lung development is to generate an organ of gas exchange that provides both a thin gas diffusion barrier and a large gas diffusion surface area, which concomitantly generates a steep gas diffusion concentration gradient. As such, the lung is perfectly structured to undertake the function of gas exchange: a large number of small alveoli provide extensive surface area within the limited volume of the lung, and a delicate alveolo-capillary barrier brings circulating blood into close proximity to the inspired air. Efficient movement of inspired air and circulating blood through the conducting airways and conducting vessels, respectively, generates steep oxygen and carbon dioxide concentration gradients across the alveolo-capillary barrier, providing ideal conditions for effective diffusion of both gases during breathing. The development of the gas exchange apparatus of the lung occurs during the second phase of lung development-namely, late lung development-which includes the canalicular, saccular, and alveolar stages of lung development. It is during these stages of lung development that preterm-born infants are delivered, when the lung is not yet competent for effective gas exchange. These infants may develop bronchopulmonary dysplasia (BPD), a syndrome complicated by disturbances to the development of the alveoli and the pulmonary vasculature. It is the objective of this review to update the reader about recent developments that further our understanding of the mechanisms of lung alveolarization and vascularization and the pathogenesis of BPD and other neonatal lung diseases that feature lung hypoplasia.

Cord Blood Biomarkers of Placental Maternal Vascular Underperfusion Predict Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension

OBJECTIVE

To assess whether cord blood biomarkers associated with placental maternal vascular underperfusion (MVU) are predictive of bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH).

STUDY DESIGN

Premature infants enrolled in a longitudinal cohort study were randomly sampled from 4 gestational age strata (n?=?190, range 23-36 weeks). Fifteen factors from a human angiogenesis panel were measured in cord blood using multiplex immunoassay. Multivariate linear regression was used to compare biomarker levels according to placental histologic MVU, taking into account acute/chronic inflammation and fetal vascular pathology. Biomarkers associated with MVU were further evaluated in the subgroup of extremely low gestational age infants (gestational age ? 28 weeks; n?=?48), and measured by enzyme-linked immunoassay in an additional 39 infants to determine associations with BPD (defined using the National Institutes of Health workshop criteria) and PH (identified by echocardiogram at 36 weeks of gestation).

RESULTS

Cord blood placental growth factor (PIGF), granulocyte-colony stimulating factor (G-CSF), and vascular endothelial growth factor-A were decreased with MVU (P?<?.003), and decreased with BPD-PH (P?<?.05). The findings were validated for PIGF and G-CSF in 39 additional extremely low gestational age infants. In the combined group (n?=?87), PIGF was decreased in infants with BPD-PH (n?=?21) versus controls without PH (median 3 pg/mL [IQR 2-7] vs median 15 pg/mL [IQR 6-30], respectively; P?<?.001). G-CSF was similarly decreased with BPD-PH (median, 55 pg/mL [IQR 38-85] vs median 243 pg/mL [IQR 48-1593], respectively; P?=?.001). Receiver operator curve analysis revealed that decreased PIGF and G-CSF were predictive of BPD-PH (area under the curve 0.83 and 0.76, respectively).

CONCLUSIONS

Cord blood angiogenic factors that are decreased with placental MVU may serve as predictors of BPD-PH.