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Metabolism is vital to cellular function and tissue homeostasis during human lung development. In utero, embryonic pluripotent stem cells undergo endodermal differentiation toward a lung progenitor cell fate that can be mimicked in vitro using induced human pluripotent stem cells (hiPSCs) to study genetic mutations. To identify differences between wild-type and surfactant protein B (SFTPB)-deficient cell lines during endoderm specification toward lung, we used an untargeted metabolomics approach to evaluate the developmental changes in metabolites. We found that the metabolites most enriched during the differentiation from pluripotent stem cell to lung progenitor cell, regardless of cell line, were sphingomyelins and phosphatidylcholines, two important lipid classes in lung development. The SFTPB mutation had no metabolic impact on early endodermal lung development. The identified metabolite signatures during lung progenitor cell differentiation may be utilized as biomarkers for normal embryonic lung development.

Surfactant protein B (SFTPB) deficiency is a fatal disease affecting newborn infants. Surfactant is produced by alveolar type II cells which can be differentiated in vitro from patient specific induced pluripotent stem cell (iPSC)-derived lung organoids. Here we show the differentiation of patient specific iPSCs derived from a patient with SFTPB deficiency into lung organoids with mesenchymal and epithelial cell populations from both the proximal and distal portions of the human lung. We alter the deficiency by infecting the SFTPB deficient iPSCs with a lentivirus carrying the wild type SFTPB gene. After differentiating the mutant and corrected cells into lung organoids, we show expression of SFTPB mRNA during endodermal and organoid differentiation but the protein product only after organoid differentiation. We also show the presence of normal lamellar bodies and the secretion of surfactant into the cell culture medium in the organoids of lentiviral infected cells. These findings suggest that a lethal lung disease can be targeted and corrected in a human lung organoid model in vitro.

Prenatal exposures to immunogenic stimuli, such as bacterial LPS, have shown to influence the neonatal immune system and lung function. However, no detailed analysis of the immunomodulatory effects of LPS on postnatal T helper cell differentiation has been performed. Using a rat model, we investigated the effect of prenatal LPS exposure on postnatal T cell differentiation and experimental allergic airway disease. Pregnant rats were injected with LPS on day 20 and 21 (term = 22 days). Some of the offspring were sensitized and challenged with ovalbumin. Positive control animals were placebo exposed to saline instead of LPS, whereas negative controls were sensitized with saline. Expression of T cell-related transcription factors and cytokines was quantified in the lung, and airway hyperresponsiveness was measured. Prenatal LPS exposure induced a T helper 1 ([T.sub.H]1) immune milieu in the offspring of rats [i.e., increased T-bet and [T.sub.H]1 cytokine expression while expression of [T.sub.H]2-associated transcription factors (GATA3 and STAT6) and cytokines was decreased]. Prenatal LPS exposure did not trigger [T.sub.H]17 cell differentiation in the offspring. Furthermore, prenatal LPS exposure reduced ovalbumin-induced ([T.sub.H]2-mediated) airway inflammation, eosinophilia, and airway responsiveness. Thus, in utero exposure to endotoxin promotes a [T.sub.H]1 immune environment, which suppresses the development of allergic airway disease later in life. asthma; lipopolysaccharide; pulmonary inflammation; ovalbumin; airway hyperresponsiveness doi: 10.1152/ajplung.00399.2009.

Maternal bacterial infections adversely affect lung development by crossing the placental barrier and infecting the developing fetus. The underlying mechanism negatively affecting pulmonary development remains unknown. Herein, we investigated whether a systemic maternal infection affects postnatal inflammation and alveolar development. Pregnant rats were injected with 2.5 mg/kg LPS on day 20 and 21 (term = 22 days). Postnatal (PN0-21) mRNA and protein expression of cytokines (IL-1[beta], IL-6, IL-10, CXCL1/2, TNF[alpha]) and genes implicated in alveologenesis [tropoelastin, lysyl oxidase (LOX), lysyl oxidase-like (LOXL)1, tenascin-C (TNC), fibulin 5, vascular endothelial growth factor (VEGF-A), VEGF receptor (VEGFR)2, VEGFR1, platelet-derived growth factor (PDGF)A, PDGFB, and PDGFR[alpha]] were quantified by real-time PCR and beadlyte technology. Lung transcript and protein levels of IL-1[beta], IL-6, and CXCL1/2 were significantly greater in LPS-exposed pups than those of control pups at PN0, 2, 6, 10, and 14. Bronchoalveolar lavage fluid (BALF) of LPS-exposed animals contained significantly more macrophages at PN2 and 14 than BALF of control pups. Morphometric analysis revealed that LPS-exposed animals had fewer and larger alveoli, fewer secondary septa, and decreased peripheral vessel density when compared with control pups. This morphological delay in alveolar development disappeared after PN14. Tropoelastin, LOXL1, VEGF, VEGFR2, and PDGFR[alpha] mRNA expression of LPS-exposed animals was significantly greater than those of control animals in PN2-14 lungs. TNC, LOX, fibulin 5, VEGFR1, PDGFA, and PDGFB expression was not affected by maternal LPS exposure. Together, the data demonstrate that maternal exposure to endotoxin results in a prolonged pulmonary inflammation postnatally, altered gene expression of molecules implicated in alveologenesis, and delayed morphological maturation of the lung. antenatal endotoxin; pulmonary inflammation

Classical tissue recombination experiments have reported that at early gestation both tracheal and distal lung epithelium have the plasticity to respond to mesenchymal signals. Herein we examined the role of epithelial-mesenchymal interactions in maintaining epithelial differentiation at late (E19-E21, term = 22 days) fetal gestation in the rat. Isolated distal lung epithelial cells were recombined with mesenchymal cells from lung, skin, and intestine, and the homotypic or heterotypic recombinant cell aggregates were cultured for up to 5 days. Recombining lung epithelial cells with mesenchyme from various sources induced a morphological pattern that was specific to the type of inducing mesenchyme. In situ analysis of surfactant protein (SP)-C, SP-B, and Clara cell secretory protein (CCSP) expression, as well as SP-C and CCSP promoter transactivation experiments, revealed that distal lung epithelium requires lung mesenchyme to maintain the alveolar, but not bronchiolar, phenotype. Incubation of lung recombinants with an anti-FGF7 antibody resulted in a partial inhibition of mesenchyme-induced SP-C promoter transactivation. Immunoreactivity for Delta and Lunatic fringe, components of the Notch pathway that regulates cell differentiation, was downregulated in the heterotypic recombinants. In contrast, Hes1 mRNA expression was increased in these recombinants. Cumulatively, these results suggest that at late fetal gestation, distal lung epithelial cells are not fully committed to a specific phenotype and still have the plasticity to respond to various signals. Their alveolar phenotype is likely maintained by Notch/Notch ligand interactions and mesenchymal factors, including FGF7. epithelial-mesenchymal interactions; cell differentiation; Notch signaling; fibroblast growth factors

Research was conducted to examine the intracellular signaling pathway by which platelet-derived growth factor (PDGF) homodimer PDGF-BB-induced GAG synthesis is relayed in primary cultures of fetal lung fibroblasts. Their activities after PDGF-BB stimulation were measured. Results indicate that P13K acts as a downstream mediator of PDGF-BB-induced GAG synthesis in fetal rat lung fibroblasts.

The increased regulation of tropoelastin (TE) synthesis in lung fibroblasts during late gestation by glucocorticoids is mediated by transforming growth factor (TGF)-beta(sub 3). TE mRNA is expressed in a developmental, organ, and cell specific way. Exogenous glucocorticoids increase the number of TE transcripts in fetal rat lung fibroblasts. Antisense TGF-beta(sub 3) and TGF-beta type I receptor oligonucleotides, and neutralizing antibodies to TGF-beta(sub 3) inhibit cortisol-stimulated TE mRNA expression. Induction of TGF-beta(sub 3) in the transfected cDNA is accompanied by increased TE mRNA.

Prenatal exposures to immunogenic stimuli, such as bacterial LPS, have shown to influence the neonatal immune system and lung function. However, no detailed analysis of the immunomodulatory effects of LPS on postnatal T helper cell differentiation has been performed. Using a rat model, we investigated the effect of prenatal LPS exposure on postnatal T cell differentiation and experimental allergic airway disease. Pregnant rats were injected with LPS on day 20 and 21 (term = 22 days). Some of the offspring were sensitized and challenged with ovalbumin. Positive control animals were placebo exposed to saline instead of LPS, whereas negative controls were sensitized with saline. Expression of T cell-related transcription factors and cytokines was quantified in the lung, and airway hyperresponsiveness was measured. Prenatal LPS exposure induced a T helper 1 (TH1) immune milieu in the offspring of rats [i.e., increased T-bet and TH1 cytokine expression while expression of TH2-associated transcription factors (GATA3 and STAT6) and cytokines was decreased]. Prenatal LPS exposure did not trigger TH17 cell differentiation in the offspring. Furthermore, prenatal LPS exposure reduced ovalbumin-induced (TH2-mediated) airway inflammation, eosinophilia, and airway responsiveness. Thus, in utero exposure to endotoxin promotes a TH1 immune environment, which suppresses the development of allergic airway disease later in life. [ABSTRACT FROM AUTHOR]

Maternal bacterial infections adversely affect lung development by crossing the placental barrier and infecting the developing fetus. The underlying mechanism negatively affecting pulmonary development remains unknown. Herein, we investigated whether a systemic maternal infection affects postnatal inflammation and alveolar development. Pregnant rats were injected with 2.5 mg/kg LPS on day 20 and 21 (term =22 days). Postnatal (PN0-21) mRNA and protein expression of cytokines (IL-1β, IL-6, IL-10, CXCL1/2, TNFα) and genes implicated in alveologenesis [tropoelastin, lysyl oxidase (LOX)~ lysyl oxidase-like (LOXL)l, tenascin-C (TNC), fibulin 5, vascular endothelial growth factor (VEGF-A), VEGF receptor (VEGFR)2, VEGFR1, platelet-derived growth factor (PDGF)A, PDGFB, and PDGFRα were quantified by real-time PCR and beadlyte technology. Lung transcript and protein levels of IL-1β, IL-6, and CXCL1/2 were significantly greater in LPS-exposed pups than those of control pups at PN0, 2, 6, 10, and 14. Bronchoalveolar lavage fluid (BALF) of LPS-exposed animals contained significantly more macrophages at PN2 and 14 than BALF of control pups. Morphometric analysis revealed that LPS-exposed animals had fewer and larger alveoli, fewer secondary septa, and decreased peripheral vessel density when compared with control pups. This morphological delay in alveolar development disappeared after PN14. Tropoelastin, LOXL1, VEGF, VEGFR2, and PDGFRα mRNA expression of LPS-exposed animals was significantly greater than those of control animals in PN2-14 lungs. TNC, LOX, fibulin 5, VEGFR1, PDGFA, and PDGFB expression was not affected by maternal LPS exposure. Together, the data demonstrate that maternal exposure to endotoxin results in a prolonged pulmonary inflammation postnatally, altered gene expression of molecules implicated in alveologenesis, and delayed morphological maturation of the lung. [ABSTRACT FROM AUTHOR]

Mechanical ventilation induces pulmonary apoptosis and inhibits alveolar development in preterm infants, but the molecular basis for the apoptotic injury is unknown. The objective was to determine the signaling mechanism(s) of ventilation (stretch)-induced apoptosis in newborn rat lung. Seven-day-old rats were ventilated with room air for 24 h using moderate tidal volumes (8.5 ml/kg). Isolated fetal rat lung epithelial and fibroblast cells were subjected to continuous cyclic stretch (5, 10, or 17% elongation) for up to 12 h. Prolonged ventilation significantly increased the number of apoptotic alveolar type II cells (i.e., terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling and anti-cleaved caspase-3 immunochemistry) and was associated with increased expression of the apoptotic mediator Fas ligand (FasL). Fetal lung epithelial cells, but not fibroblasts, subjected to maximal (i.e., 17%, but not lesser elongation) cyclic stretch exhibited increased apoptosis (i.e., nuclear fragmentation and DNA laddering), which appeared to be mediated via the extrinsic pathway (increased expression of FasL and cleaved caspase-3, -7, and -8). The intrinsic pathway appeared not to be involved [minimal mitochondrial membrane depolarization (JC-1 flow analysis) and no activation of caspase-9]. Universal caspases inhibition and neutralization of FasL abrogated the stretch-induced apoptosis. Prolonged mechanical ventilation induces apoptosis of alveolar type II cells in newborn rats and the mechanism appears to involve activation of the extrinsic death pathway via the FasL/Fas system.