The importance of surfactant on the development of neonatal pulmonary diseases

Surfactant proteins analysis in perinatal deceased preterm twins among the Romanian population

The molecular basis of the evaluation of children suspected of having disorders of surfactant proteins is still under discussion. In this study, we aimed to describe the morphological characteristics and to evaluate the immunohistochemical expression of surfactant proteins (surfactant protein A [SPA], surfactant protein B, and pro-surfactant protein C) in the preterm twins that deceased due to unexplained respiratory distress syndrome (n = 12). Results showed statistically significant positive correlations between surfactant protein B expressions and pulmonary hemorrhage (ρ = 0.678; P < .05), SPA levels, and Apgar score (ρ = 0.605; P < .05) and also expressions of SPA and bronchopneumonia (ρ = 0.695; P < .05). The fetuses and neonates of the same gestational age showed differences among surfactant proteins regarding the immunostaining expression. Our data evidence a marked interindividual variability in the expression of all 3 surfactant proteins among the cases analyzed (n = 12), suggesting the intervention of some individual and epigenetic factors during gestation that might influence surfactant protein production and consequently survival rate.

Surfactant Protein C Deficiency in a Puerto Rican Adolescent With a Rare SFTPC Genetic Variant

Surfactant protein C (SP-C) is a hydrophobic lipoprotein necessary for lowering alveolar surface tension and lung defense mechanisms. Defects in its function due to genetic mutations in the SFTPC gene have been increasingly identified in patients presenting with childhood interstitial lung disease. SFTPC mutations are inherited in an autosomal dominant pattern with reduced penetration and variable expressivity, although de novo mutations have also been documented. In this article, we present the case of an oxygen-dependent 13-year-old male with interstitial lung disease and severe pulmonary hypertension. Genetic analysis and lung biopsy confirmed the diagnosis of SP-C deficiency with the rare heterozygous mutation IVS4+2. To our knowledge, this is the first documented case of SP-C deficiency in the Puerto Rican population and the second worldwide with the IVS4+2 genetic mutation.

Genetic Polymorphisms of SP-A, SP-B, and SP-D and Risk of Respiratory Distress Syndrome in Preterm Neonates

Background

We examined selected polymorphisms in 3 pulmonary surfactant-associated proteins (SP) for their influence on serum SP levels and risk of respiratory distress syndrome (RDS) in preterm neonates.

Material/Methods

Premature infants from a Han population were enrolled, including 100 premature infants with RDS (case group) and 120 premature infants without RDS (control group). SNP genotyping for SP-A (+186A/G and +655C/T), SP-B (−18A/C and 1580C/T), and SP-D (Met11ThrT/C and Ala160ThrG/A) used polymerase chain reaction-restriction fragment length polymorphism. Haplotypes were calculated with Shesis software and serum SP-A/B/D levels were quantified by ELISA.

Results

Case and control groups exhibited significant differences in genotype and allele frequencies of SP-A (+186A/G, +655C/T) and SP-B (1580C/T). However, no statistically significant differences were observed in the allele and genotype frequencies of SP-B −18A/C, SP-D Met11ThrT/C, and SP-D Ala160ThrG/A. Importantly, serum SP-A and SP-B levels were reduced in RDS patients carrying SP-A (+186A/G, +655C/T) and SP-B (1580C/T) polymorphisms. AA genotype of +186A/G, SP-A level, and CC genotype of 1580C/T were independently correlated with increased RDS risk.

Conclusions

SP-A (+186A/G) and SP-B (1580C/T) polymorphisms are strongly associated with the risk of RDS in preterm infants. Notably, reduced serum SP-A levels were correlated with a high risk of RDS and may serve as novel biomarkers for RDS detection and monitoring.

Novel Mutation in the ATP-Binding Cassette Transporter A3 (ABCA3) Encoding Gene Causes Respiratory Distress Syndrome in A Term Newborn in Southwest Iran

INTRODUCTION

ABCA3 glycoprotein belongs to the ATP-binding cassette (ABC) superfamily of transporters, which utilize the energy derived from hydrolysis of ATP for the translocation of a wide variety of substrates across the plasma membrane. Mutations in the ABCA3 gene are knowingly causative for fatal surfactant deficiency, particularly respiratory distress syndrome (RDS) in term babies.

CASE PRESENTATION

In this study, Sanger sequencing of the whole ABCA3 gene (NCBI NM_001089) was performed in a neonatal boy with severe RDS. A homozygous mutation has been identified in the patient. Parents were heterozygous for the same missense mutation GGA > AGA at position 202 in exon 6 of the ABCA3 gene (c.604G > A; p.G202R). Furthermore, 70 normal individuals have been analyzed for the mentioned change with negative results.

CONCLUSIONS

Regarding Human Genome Mutation Database (HGMD) and other literature recherche, the detected change is a novel mutation and has not been reported before. Bioinformatics mutation predicting tools prefer it as pathogenic.

Maternal bile acid transporter deficiency promotes neonatal demise

Intrahepatic cholestasis of pregnancy (ICP) is associated with adverse neonatal survival and is estimated to impact between 0.4 and 5% of pregnancies worldwide. Here we show that maternal cholestasis (due to Abcb11 deficiency) produces neonatal death among all offspring within 24 h of birth due to atelectasis-producing pulmonary hypoxia, which recapitulates the neonatal respiratory distress of human ICP. Neonates of Abcb11-deficient mothers have elevated pulmonary bile acids and altered pulmonary surfactant structure. Maternal absence of Nr1i2 superimposed on Abcb11 deficiency strongly reduces maternal serum bile acid concentrations and increases neonatal survival. We identify pulmonary bile acids as a key factor in the disruption of the structure of pulmonary surfactant in neonates of ICP. These findings have important implications for neonatal respiratory failure, especially when maternal bile acids are elevated during pregnancy, and highlight potential pathways and targets amenable to therapeutic intervention to ameliorate this condition.

Disruption of sorting nexin 5 causes respiratory failure associated with undifferentiated alveolar epithelial type I cells in mice

Sorting nexin 5 (Snx5) has been posited to regulate the degradation of epidermal growth factor receptor and the retrograde trafficking of cation-independent mannose 6-phosphate receptor/insulin-like growth factor II receptor. Snx5 has also been suggested to interact with Mind bomb-1, an E3 ubiquitin ligase that regulates the activation of Notch signaling. However, the in vivo functions of Snx5 are largely unknown. Here, we report that disruption of the Snx5 gene in mice (Snx5^-/- mice) resulted in partial perinatal lethality; 40% of Snx5^-/- mice died shortly after birth due to cyanosis, reduced air space in the lungs, and respiratory failure. Histological analysis revealed that Snx5^-/- mice exhibited thickened alveolar walls associated with undifferentiated alveolar epithelial type I cells. In contrast, alveolar epithelial type II cells were intact, exhibiting normal surfactant synthesis and secretion. Although the expression levels of surfactant proteins and saturated phosphatidylcholine in the lungs of Snx5^-/- mice were comparable to those of Snx5^+/+ mice, the expression levels of T1α, Aqp5, and Rage, markers for distal alveolar epithelial type I cells, were significantly decreased in Snx5^-/- mice. These results demonstrate that Snx5 is necessary for the differentiation of alveolar epithelial type I cells, which may underlie the adaptation to air breathing at birth.

Role of prophylactic surfactant in preterm infants

BACKGROUND

Respiratory distress syndrome (RDS) in preterm neonates is caused by a deficiency or dysfunction of pulmonary surfactant. The physiological function of surfactant includes the ability to lower surface tension, as well as the ability to rapidly adsorb and spread. A wide variety of surfactant products have been formulated and studied in clinical trials. The present study was designed to find out whether prophylactic administration of surfactant leads to a significant decrease in the risk of neonatal mortality and neonatal morbidity.

METHODS

This was an experimental study in which a total of 125 preterm newborns less than 34 weeks gestation were studied. One hundred preterm newborns (controls) less than 34 weeks gestation were managed in the conventional manner as per the existing protocols in the neonatal intensive care unit. Twenty-five consecutively delivered preterm newborns less than 34 weeks gestation were administered surfactant. Data regarding clinical outcomes including mortality and morbidity profile was collected and analysed.

RESULTS

The mean duration of ventilation in the ventilated babies in the control group and the surfactant group was 129.8 ± 43 hours and 85.7 ± 46 hours, respectively; the difference being statistically significant. In the surfactant group, four babies (16%) died and in the control group, 27 babies (27%) died. The difference was not statistically significant. The number of babies developing retinopathy of prematurity and needing laser treatment for retinopathy of prematurity was greater in the surfactant group.

CONCLUSION

Prophylactic administration of surfactant in preterm newborns of gestational age < 34 weeks is associated with a significant decrease in mean duration of ventilation and an increase in the incidence of retinopathy of prematurity.

[Congenital pulmonary alveolar proteinosis related to a surfactant protein B deficiency: report of two cases]

Congenital pulmonary alveolar proteinosis is an uncommon affection, distinct from adult's alveolar proteinosis by its clinical, pathological, etiological and evolutive characteristics. We report two cases of congenital alveolar proteinosis related to a surfactant protein B deficiency. Clinical presentations were similar: the two children were full-term newborns and had swiftly developed respiratory distress. Chest radiography demonstrated bilateral alveolar syndrome. Echocardiography was normal. There was no sign of infection. The two children died respectively at three weeks and two months of life. Lung biopsy showed lesions of alveolar proteinosis in the two cases. Both children were homozygotes for the 121ins2 mutation of the SFTPB gene. Diagnosis of surfactant protein B deficiency must be suspected in congenital alveolar proteinosis. It can be confirmed by the absence of detection of the surfactant B protein by immunohistochemistry on fixed and paraffin-embedded lung tissue or by western blot on bronchoalveolar fluid and by the absence of mRNA by RT-PCR. We report the value of molecular diagnosis for genetic counseling and the possibility of early prenatal diagnosis by trophoblast biopsy.