Arginase 1 and L-arginine coordinate fetal lung development and the initiation of labor in mice.

Fetal development and parturition are precisely regulated processes that involve continuous crosstalk between the mother and the fetus. Our previous discovery that wild-type mice carrying steroid receptor coactivator (Src)-1 and Src-2 double-deficient fetuses exhibit impaired lung development and delayed labor, which indicates that the signals for parturition emanate from the fetus. In this study, we perform RNA sequencing and targeted metabolomics analyses of the lungs from fetal Src-1/-2 double-knockout mice and find that expression of arginase 1 (Arg1) is significantly decreased, accompanied by increased levels of the Arg1 substrate L-arginine. Knockdown of Arg1 in the lungs of fetal mice induces apoptosis of epithelial cells and dramatically delays initiation of labor. Moreover, treatment of human myometrial smooth muscle cells with L-arginine significantly inhibits spontaneous contractions by attenuating activation of NF-κB and downregulating expression of contraction-associated protein genes. Transcription factors GR and C/EBPß increase transcription of Arg1 in an Src-1/Src-2-dependent manner. These findings provide new evidence that fetus-derived factors may play dual roles in coordinating fetal lung development and the initiation of labor.

Impact of maternal late gestation undernutrition on surfactant maturation, pulmonary blood flow and oxygen delivery measured by magnetic resonance imaging in the sheep fetus.

Restriction of fetal substrate supply has an adverse effect on surfactant maturation in the lung and thus affects the transition from in utero placental oxygenation to pulmonary ventilation ex utero. The effects on surfactant maturation are mediated by alteration in mechanisms regulating surfactant protein and phospholipid synthesis. This study aimed to determine the effects of late gestation maternal undernutrition (LGUN) and LGUN plus fetal glucose infusion (LGUN+G) compared to Control on surfactant maturation and lung development, and the relationship with pulmonary blood flow and oxygen delivery ( DO2 ) measured by magnetic resonance imaging (MRI) with molecules that regulate lung development. LGUN from 115 to 140 days' gestation significantly decreased fetal body weight, which was normalized by glucose infusion. LGUN and LGUN+G resulted in decreased fetal plasma glucose concentration, with no change in fetal arterial PO2 compared to control. There was no effect of LGUN and LGUN+G on the mRNA expression of surfactant proteins (SFTP) and genes regulating surfactant maturation in the fetal lung. However, blood flow in the main pulmonary artery was significantly increased in LGUN, despite no change in blood flow in the left or right pulmonary artery and DO2 to the fetal lung. There was a negative relationship between left pulmonary artery flow and DO2 to the left lung with SFTP-B and GLUT1 mRNA expression, while their relationship with VEGFR2 was positive. These results suggest that increased pulmonary blood flow measured by MRI may have an adverse effect on surfactant maturation during fetal lung development. KEY POINTS: Maternal undernutrition during gestation alters fetal lung development by impacting surfactant maturation. However, the direction of change remains controversial. We examined the effects of maternal late gestation maternal undernutrition (LGUN) on maternal and fetal outcomes, signalling pathways involved in fetal lung development, pulmonary haemodynamics and oxygen delivery in sheep using a combination of molecular and magnetic resonance imaging (MRI) techniques. LGUN decreased fetal plasma glucose concentration without affecting arterial PO2 . Surfactant maturation was not affected; however, main pulmonary artery blood flow was significantly increased in the LGUN fetuses. This is the first study to explore the relationship between in utero MRI measures of pulmonary haemodynamics and lung development. Across all treatment groups, left pulmonary artery blood flow and oxygen delivery were negatively correlated with surfactant protein B mRNA and protein expression in late gestation.

Decreased 11ß-hydroxysteroid dehydrogenase 1 in lungs of steroid receptor coactivator (Src)-1/-2 double-deficient fetal mice is caused by impaired glucocorticoid and cytokine signaling.

Our previous research revealed that steroid receptor coactivators (Src)-1 and -2 serve a critical cooperative role in production of parturition signals, surfactant protein A and platelet-activating factor, by the developing mouse fetal lung (MFL). To identify the global landscape of genes in MFL affected by Src-1/-2 double-deficiency, we conducted RNA-seq analysis of lungs from 18.5 days post-coitum (dpc) Src-1-/- /-2-/- (dKO) vs. WT fetuses. One of the genes most highly downregulated (~4.8 fold) in Src-1/-2 dKO fetal lungs encodes 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), which catalyzes conversion of inactive 11-dehydrocorticosterone to the glucocorticoid receptor (GR) ligand, corticosterone. Glucocorticoids were reported to upregulate 11ß-HSD1 expression in various cell types via induction of C/EBP transcription factors. We observed that C/ebpα and C/ebpß mRNA and protein were markedly reduced in Src-1/-2 double-deficient (Src-1/-2d/d ) fetal lungs, compared to WT. Moreover, glucocorticoid induction of 11ß-hsd1, C/ebpα and C/ebpß in cultured MFL epithelial cells was prevented by the SRC family inhibitor, SI-2. Cytokines also contribute to the induction of 11ß-HSD1. Expression of IL-1ß and TNFα, which dramatically increased toward term in lungs of WT fetuses, was markedly reduced in Src-1/-2d/d fetal lungs. Our collective findings suggest that impaired lung development and surfactant synthesis in Src-1/-2d/d fetuses are likely caused, in part, by decreased GR and cytokine induction of C/EBP and NF-κB transcription factors. This results in reduced 11ß-HSD1 expression and glucocorticoid signaling within the fetal lung, causing a break in the glucocorticoid-induced positive feedforward loop.

Reversible Fetal Tracheal Occlusion in Mice: A Novel Minimal Invasive Technique.

BACKGROUND: There is a certain need for reversible, cheap, and reproducible animal models for understanding the impact of tracheal occlusion (TO) in the congenital diaphragmatic hernia and pathophysiology. We aimed to present an easy, reversible, and minimally invasive murine TO model with optimized time points for introduction and removal of TO. METHODS: Time-mated C57BL/6 mice underwent laparotomy at embryonic day 16.5 (E16.5) with transuterine TO performed on two fetuses in each uterine horn. In the TO group, the fetuses were harvested at E18.5 without suture removal; the suture was released at E17.5 in the TO-R group, and all fetuses were harvested at E18.5. The lungs of the fetuses were compared by morphometric and histologic analysis. RESULTS: Successful TO was confirmed in 34 of 37 fetuses. Twenty-nine of them survived to E18.5 (90.6%), six of the fetuses had a spontaneous vaginal delivery. Fetal weights were comparable, but there was significant difference in lung weights and lung-to-body weight ratios (0.020 ± 0.006 [control] versus 0.026 ± 0.002 [TO] versus 0.023 ± 0.005 [TO-R]; P = 0.013). DNA/protein and DNA/lung weight ratios were elevated, whereas protein/lung weight ratio was lower in TO compared with the control group. CONCLUSIONS: Reversal of fetal transuterine TO at E17.5, which was put at E16.5 in mice, is feasible with comparable outcomes to other current animal models with certain advantages and potential to translate the studies to the human.

High resolution three-dimensional imaging and measurement of lung, heart, liver, and diaphragmatic development in the fetal rat based on micro-computed tomography (micro-CT).

Understanding of normal fetal organ development is crucial for the evaluation of the pathogenesis of congenital anomalies. Various techniques have been used to generate imaging of fetal rat organogenesis, such as histological dissection with 3-dimensional reconstruction and scanning electron microscopy. However, these techniques did not imply quantitative measurements of developing organs (volumes, surface areas of organs). Furthermore, a partial or total destruction of the embryos prior to analysis was inevitable. Recently, micro-computed tomography (micro-CT) has been established as a novel tool to investigate embryonic development in non-dissected embryos of rodents. In this study, we used the micro-CT technique to generate 4D datasets of rat embryos aged between embryonic day 15-22 and newborns. Lungs, hearts, diaphragms, and livers were digitally segmented in order to measure organ volumes and analyze organ development as well as generate high-resolution 3D images. These data provide objective values compiling a 4D atlas of pulmonary, cardiac, diaphragmatic, and hepatic development in the fetal rat.

Targeted Disruption of Mouse Dip2B Leads to Abnormal Lung Development and Prenatal Lethality.

Molecular and anatomical functions of mammalian Dip2 family members (Dip2A, Dip2B and Dip2C) during organogenesis are largely unknown. Here, we explored the indispensable role of Dip2B in mouse lung development. Using a LacZ reporter, we explored Dip2B expression during embryogenesis. This study shows that Dip2B expression is widely distributed in various neuronal, myocardial, endothelial, and epithelial cell types during embryogenesis. Target disruption of Dip2b leads to intrauterine growth restriction, defective lung formation and perinatal mortality. Dip2B is crucial for late lung maturation rather than early-branching morphogenesis. The morphological analysis shows that Dip2b loss leads to disrupted air sac formation, interstitium septation and increased cellularity. In BrdU incorporation assay, it is shown that Dip2b loss results in increased cell proliferation at the saccular stage of lung development. RNA-seq analysis reveals that 1431 genes are affected in Dip2b deficient lungs at E18.5 gestation age. Gene ontology analysis indicates cell cycle-related genes are upregulated and immune system related genes are downregulated. KEGG analysis identifies oxidative phosphorylation as the most overrepresented pathways along with the G2/M phase transition pathway. Loss of Dip2b de-represses the expression of alveolar type I and type II molecular markers. Altogether, the study demonstrates an important role of Dip2B in lung maturation and survival.

Oxygen Disrupts Human Fetal Lung Mesenchymal Cells. Implications for Bronchopulmonary Dysplasia.

Exogenous mesenchymal stromal cells (MSCs) ameliorate experimental bronchopulmonary dysplasia. Moreover, data from term-born animal models and human tracheal aspirate-derived cells suggest altered mesenchymal signaling in the pathophysiology of neonatal lung disease. We hypothesized that hyperoxia, a factor contributing to the development of bronchopulmonary dysplasia, perturbs human lung-resident MSC function. Mesenchymal cells were isolated from human fetal lung tissue (16-18 wk of gestation), characterized and cultured in conditions resembling either intrauterine (5% O2) or extrauterine (21% and 60% O2) atmospheres. Secretome data were compared with MSCs obtained from term umbilical cord tissues. The human fetal lung mesenchyme almost exclusively contains CD146pos. MSCs expressing SOX-2 and OCT-4, which secrete elastin, fibroblast growth factors 7 and 10, vascular endothelial growth factor, angiogenin, and other lung cell-protecting/-maturing proteins. Exposure to extrauterine atmospheres in vitro leads to excessive proliferation, reduced colony-forming ability, alterations in the cell's surface marker profile, decreased elastin deposition, and impaired secretion of factors important for lung growth. Conversely, umbilical cord-derived MSCs abundantly secreted factors that impaired lung MSCs are unable to produce. Oxygen-impaired human fetal lung MSC function may contribute to disrupted repair capacity and arrested lung growth. Exogenous MSCs may act by triggering the signaling pathways lost by impaired endogenous lung mesenchymal cells.

Fetal tracheal occlusion in mice: a novel transuterine method.

BACKGROUND: Fetal tracheal occlusion (TO) is an emerging surgical therapy in congenital diaphragmatic hernia that improves the fetal lung growth. Different animal models of congenital diaphragmatic hernia and TO present advantages and disadvantages regarding ethical issues, cost, surgical difficulty, size, survival rates, and available genetic tools. We developed a minimally invasive murine transuterine TO model, which will be useful in defining how TO impacts lung molecular biology, cellular processes, and overall lung physiology. MATERIALS AND METHODS: Time-mated C57BL/6 mice underwent laparotomy at embryonic day 16.5 (E16.5) with transuterine TO performed on two fetuses in each uterine horn. At E18.5, dams were sacrificed and fetuses harvested. The lungs of the TO fetuses were compared with the nonmanipulated counterparts by morphometric and histologic analysis. RESULTS: Successful TO was confirmed in 16 of 20 TO fetuses. Twelve of them survived to E18.5 (75%). Fetal weights were comparable, but lung weights were significantly greater in TO (28.41 ± 5.87 versus 23.38 ± 3.09, P = 0.043). Lung to body weight ratio was also greater (0.26 ± 0.003 versus 0.22 ± 0.002, P = 0.006). E18.5 TO lungs demonstrated dilated central and distal airspaces with increased cellularity. DNA/protein and DNA/lung weight ratios were elevated while protein/lung weight ratio was lower in TO compared to control. CONCLUSIONS: Mice fetal transuterine TO is feasible with comparable outcomes to other current animal models. The increase in the lung weight, lung to body weight ratio and the DNA/protein ratio indicate organized lung growth rather than edema or cell hypertrophy.

miR-124 regulates fetal pulmonary epithelial cell maturation.

MicroRNAs are a family of small noncoding RNAs that regulate the expression of their target proteins at the posttranscriptional level. Their functions cover almost every aspect of cell physiology. However, the roles of microRNAs in fetal lung development are not completely understood. The objective of this study is to investigate the regulation and molecular mechanisms of alveolar epithelial cell maturation during fetal lung development by miR-124. We discovered that miR-124 was downregulated during rat fetal lung development and predominantly expressed in the epithelial cells at late stage of the lung development. Overexpression of miR-124 with an adenovirus vector led to the inhibition of epithelial maturation in rat fetal lung organ cultures and fetal alveolar epithelial type II cells, as demonstrated by a decrease in the type II cell marker expression and an increase in glycogen content. We further demonstrated by luciferase reporter assays that miR-124 inhibited the NF-κB, cAMP/PKA, and MAPK/ERK pathways. In addition, nuclear factor I/B (NFIB), a critical protein in fetal lung maturation, was validated as a direct target of miR-124. Furthermore, miR-124 expression was induced by the Wnt/ß-catenin signaling pathway through a direct interaction of LEF1 and the miR-124 promoter region. We concluded that miR-124 downregulation is critical to fetal lung epithelial maturation and miR-124 inhibits this maturation process at least partially through the inhibition of NFIB.

The developmental toxicity of PM2.5 on the early stages of fetal lung with human lung bud tip progenitor organoids.

Exposure to air pollution has been proven to be associated with impaired fetal lung development. However, due to the lack of reliable human source models, it is still challenging to deeply understand the human fetal lung development under PM2.5 exposure. Here, we utilized human embryonic stem cell (hESC) line H9 to generate lung bud tip progenitor organoids (LPOs), a process that mimics early stages of fetal lung development including definitive endoderm (DE) formation, anterior foregut endoderm (AFE) differentiation and lung progenitor cell specification, to evaluate potential pulmonary developmental toxicity of PM2.5. We demonstrated that PM2.5 exposure the entire LPOs induction from hESCs significantly affected cellular proliferation of LPOs, and altered the expression of lung progenitor cell markers NKX2.1, SOX2 and SOX9, which are canonically defined subsequently proximal-distal airways specification. To explore the dynamic influences of PM2.5 exposure at different stages of LPOs specification, we also found that PM2.5 exposure significantly affected the expression of several transcriptional factors that are important for the differentiation of DE and AFE. Mechanistically, we suggested PM2.5-induced developmental toxicity to LPOs was partially linked with the Wnt/ß-catenin signaling pathway. Therefore, our findings further emphasize the substantial health risks in the development of respiratory system associated with prenatal exposure to PM2.5.

Y It Matters-Sex Differences in Fetal Lung Development.

Within this review, sex-specific differences in alveolar epithelial functions are discussed with special focus on preterm infants and the respiratory disorders associated with premature birth. First, a short overview about fetal lung development, the challenges the lung faces during perinatal lung transition to air breathing and respiratory distress in preterm infants is given. Next, clinical observations concerning sex-specific differences in pulmonary morbidity of human preterm infants are noted. The second part discusses potential sex-specific causes of pulmonary complications, including pulmonary steroid receptors and local lung steroid metabolism. With regard to pulmonary steroid metabolism, it is important to highlight which steroidogenic enzymes are expressed at which stage during fetal lung development. Thereafter, we review the knowledge concerning sex-specific aspects of lung growth and maturation. Special focus is given to alveolar epithelial Na+ transport as a driver of perinatal lung transition and the sex differences that were noted in this process.

Expression profiles of long non-coding RNAs during fetal lung development.

With advances in neonatology, a greater percentage of premature infants now survive and consequently, diseases of lung development, including bronchopulmonary dysplasia and neonatal respiratory distress syndrome, have become more common. However, few studies have addressed the association between fetal lung development and long non-coding RNA (lncRNA). In the present study, right lung tissue samples of fetuses at different gestational ages were collected within 2 h of the induction of labor in order to observe morphological discrepancies. An Affymetrix Human GeneChip was used to identify differentially expressed lncRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed. A total of 687 lncRNAs were identified to be differentially expressed among three groups of fetal lung tissue samples corresponding to the three embryonic periods. A total of 34 significantly upregulated and 12 significantly downregulated lncRNAs (fold-change, ≥1.5; P<0.05) were detected at different time points (embryonic weeks 7-16, 16-25 and 25-28) of fetal lung development and compared with healthy tissues Expression changes in lncRNAs n340848, n387037, n336823 and ENST00000445168 were validated by reverse transcription-quantitative PCR and the results were consistent with the GeneChip results. These novel identified lncRNAs may have roles in fetal lung development and the results of the present study may lay the foundation for subsequent in-depth studies into lncRNAs in fetal lung development and subsequent clarification of the pathogenesis of neonatal pulmonary diseases.

Intrauterine Gardnerella vaginalis Infection Results in Fetal Growth Restriction and Alveolar Septal Hypertrophy in a Rabbit Model.

Background: Gardnerella vaginalis (GV) is most frequently associated with bacterial vaginosis and is the second most common etiology causing intrauterine infection after Ureaplasma urealyticum. Intrauterine GV infection adversely affects pregnancy outcomes, resulting in preterm birth, fetal growth restriction, and neonatal pneumonia. The knowledge of how GV exerts its effects is limited. We developed an in vivo animal model to study its effects on fetal development. Materials and Methods: A survival mini-laparotomy was conducted on New Zealand rabbits on gestational day 21 (28 weeks of human pregnancy). In each dam, fetuses in the right uterine horn received intra-amniotic 0.5 × 102 colony-forming units of GV injections each, while their littermate controls in the left horn received sterile saline injections. A second laparotomy was performed seven days later. Assessment of the fetal pups, histopathology of the placenta and histomorphometric examination of the fetal lung tissues was done. Results: Three dams with a combined total of 12 fetuses were exposed to intra-amniotic GV, and 9 fetuses were unexposed. The weights of fetuses, placenta, and fetal lung were significantly lower in the GV group than the saline-inoculated control group [mean gross weight, GV (19.8 ± 3.8 g) vs. control (27.9 ± 1.7 g), p < 0.001; mean placenta weight, GV (5.5 ± 1.0 g) vs. control (6.5 ± 0.7 g), p = 0.027; mean fetal lung weight, GV (0.59 ± 0.11 g) vs. control (0.91 ± 0.08 g), p = 0.002. There was a two-fold increase in the multinucleated syncytiotrophoblasts in the placenta of the GV group than their littermate controls (82.9 ± 14.9 vs. 41.6 ± 13.4, p < 0.001). The mean alveolar septae of GV fetuses was significantly thicker than the control (14.8 ± 2.8 µm vs. 12.4 ± 3.8 µm, p = 0.007). Correspondingly, the proliferative index in the interalveolar septum was 1.8-fold higher in the GV group than controls (24.9 ± 6.6% vs. 14.2 ± 2.9%, p = 0.011). The number of alveoli and alveolar surface area did not vary between groups. Discussion: Low-dose intra-amniotic GV injection induces fetal growth restriction, increased placental multinucleated syncytiotrophoblasts and fetal lung re-modeling characterized by alveolar septal hypertrophy with cellular proliferative changes. Conclusion: This intra-amniotic model could be utilized in future studies to elucidate the acute and chronic effects of GV intrauterine infections.

The science of steroids.

Steroids are complex lipophilic molecules that have many actions in the body to regulate cellular, tissue and organ functions across the life-span. Steroid hormones such as cortisol, aldosterone, estradiol and testosterone are synthesised from cholesterol in specialised endocrine cells in the adrenal gland, ovary and testis, and released into the circulation when required. Steroid hormones move freely into cells to activate intracellular nuclear receptors that function as multi-domain ligand-dependent transcriptional regulators in the cell nucleus. Activated nuclear receptors modify expression of hundreds to thousands of specific target genes in the genome. Steroid hormone actions in the fetus include developmental roles in the respiratory system, brain, and cardiovascular system. The synthetic glucocorticoid steroid betamethasone is used antenatally to reduce the complications of preterm birth. Development of novel selective partial glucocorticoid receptor agonists may provide improved therapies to treat the respiratory complications of preterm birth and spare the deleterious effects of postnatal glucocorticoids in other organs.

Expression of Lung Surfactant Proteins SP-B and SP-C and Their Regulatory Factors in Fetal Lung of GDM Rats.

This study investigated the expression of lung surfactant proteins (SP-B and SP-C), and regulatory factors [forkhead box A2 (FOXA2) and nitrolyogenic FOXA2 (N-FOXA2)] in the fetal lung of rats with gestational diabetes mellitus (GDM) in order to study the mechanism of pulmonary dysplasia. The rat GDM model was established by using streptozotocin intraperitoneally in the first stage of pregnancy. There were 10 rats in the GDM group, and 10 healthy rats in normal control group without any treatment. Fetal lungs of two groups were taken at day 21 of pregnancy. Blood glucose levels of maternal rats and fetal rats were measured by Roche blood glucose meter. The histological changes in the fetal lung were observed under the light microscope in both groups. The SP-B, SP-C and FOXA2 were determined in the fetal lung of two groups immunohistochemically. The expression levels of SP-B, SP-C, total FOXA2, FOXA2 in nucleus (n-FOXA2), N-FOXA2 proteins were detected by Western blotting, and the relative expression levels of SP-B, SP-C, FOXA2 mRNA in the fetal lung of two groups were detected by RTPCR. The results showed that blood glucose levels of maternal rats and fetal rats in GDM group were higher than those in control group. The light microscope revealed fetal lung development retardation in GDM group. The expression of SP-B and SP-C in GDM group was significantly reduced as compared with control group (P<0.05). As compared with control group, the n-FOXA2 expression was significantly decreased in the fetal lung tissue, and N-FOXA2 was significantly increased in control group (P<0.05), but there was no significant changes in the total FOXA2 (P>0.05). It was concluded that GDM can cause fetal lung development and maturation disorders, and FOXA2 in fetal lung tissue decreases while nitrocellulose FOXA2 increases.

The reduction in FOXA2 activity during lung development in fetuses from diabetic rat mothers is reversed by Akt inhibition.

Hyperglycemia during pregnancy is associated with fetal lung development disorders and surfactant protein (SP) deficiency. Here, we examined the role of FOXA2 and Akt signaling in fetal lung development during diabetic pregnancy. Sprague-Dawley rats were injected with streptozocin (STZ) during pregnancy to induce diabetes (DM). DM-exposed fetal lungs exhibited reduced numbers of alveoli, irregularities in the appearance and thickness of the alveolar septum, increased levels of glycogen and lipids in type II alveolar epithelial cells, fewer microvilli and mature lamellar bodies, and swollen mitochondria. SP-B and SP-C in DM amniotic fluid and DM lungs were lower than in the control group (P < 0.05). DM lung nuclear FOXA2 was lower compared with the control group (P < 0.05), but p-FOXA2 was higher (P < 0.05). In murine lung epithelial (MLE) 12 cells, p-AKT levels were increased by high glucose/insulin, but decreased by the Akt inhibitor MK2206 (P < 0.05). Expression of nuclear FOXA2 was increased by MK2206 compared with the high glucose/insulin group (P < 0.05). These results suggest that maternal diabetes induces fetal lung FOXA2 phosphorylation through the Akt pathway, and also affects the maturation of alveolar epithelial cells and reduces levels of SP-B and SP-C in the fetal lungs. An Akt inhibitor reversed the changes in SP expression in vitro.

Cloaca in discordant monoamniotic twins: prenatal diagnosis and consequence for fetal lung development.

Objective Describe a case of cloaca prenatally diagnosed in one of a set of monoamniotic twins. Study Design Retrospective review of a case. Results Cloaca is one of the most complex and severe degrees of anorectal malformations in girls. We present a discordant cloaca in monoamniotic twins. Fetal ultrasound showed a female fetus with a pelvic midline cystic mass, a phallus-like structure, a probable anorectal atresia with absence of anal dimple and a flat perineum, and renal anomalies. The diagnosis was confirmed by fetal magnetic resonance imaging postnatally. Conclusions The rarity of the malformation in a monoamniotic pregnancy, the difficulties of prenatal diagnosis, the pathogenic assumptions, and the consequences of adequate amniotic fluid for fetal lung development are discussed.

The extracellular calcium-sensing receptor, CaSR, in fetal development.

In fetal mammals, serum levels of both total and ionized calcium significantly exceed those in the adult. This relative fetal hypercalcemia is crucial for skeletal development and is maintained irrespectively of maternal serum calcium levels. Elegant studies by Kovacs and Kronenberg have previously addressed the role of the CaSR in creating and maintaining this relative fetal hypercalcemia, through the regulation of parathyroid hormone-related peptide secretion. More recently we have shown that the CaSR is widely distributed throughout the developing fetus, where the receptor plays major, unexpected roles in ensuring growth and maturation of several organs. In this article, we present evidence for a role of the CaSR in the control of skeletal development, and how fetal hypercalcemia, acting through the CaSR, regulates lung development.

Prenatal diagnosis of unilateral pulmonary dysplasia.

Pulmonary hypoplasia is a rare congenital disorder; most cases occur in association with other congenital abnormalities, including congenital diaphragmatic hernia, oligohydramnios, and/or skeletal deformities. The authors report a case of unilateral pulmonary hypoplasia diagnosed prenatally and confirmed at autopsy.

Fetal lung epithelial ion channels relocate in the cell membrane during late gestation.

Near the end of gestation, the direction of ion and fluid flow across the alveolar epithelium rapidly changes from secretion to absorption. Thus, the relative cell membrane location of epithelial Na channels (ENaCs) and cystic fibrosis transmembrane regulator (CFTR) Cl channels during late fetal lung development and after maternal interleukin-1ß (IL-1ß) pretreatment was the focus of our study. Western blot analysis after sucrose gradient separation of caveolin-1-(Cav-1)-rich membrane regions (CRR) and Cav-1-poor membrane (non-CRR) revealed primary CRR ENaC localization at gestation day (GD) 61 in guinea pigs. Correlating with the natural induction of distal lung fluid absorption, ENaC appeared in the non-CRR cell membrane regions at GD68. Conversely, CFTR was present in the non-CRR cell membrane regions at GD61 and in the CRRs at GD68. IL-1ß-induced conversion to distal lung fluid absorption at GD61 was associated with ENaC non-CRR presence and CFTR CRR presence, suggesting that relative ENaC and CFTR locations induced distal lung fluid absorption and decreased fluid secretion. Instilling fetal lungs with the CRR-disrupting agent methyl-ß-cyclodextrin resulted in the conversion from lung fluid secretion to absorption and ENaC non-CRR presence at GD61. Coimmunoprecipitation of Cav-1 with α- and ß-ENaC demonstrated reduced coimmunoprecipitation with increased GD and after IL-1ß pretreatment. On the other hand, coimmunoprecipitation of Cav-1 with CFTR demonstrated increased coimmunoprecipitation with increasing GD and after IL-1ß pretreatment. This concept may provide novel molecular mechanisms for the rapid transition from fetal distal lung fluid secretion to absorption in near-term lungs.