Biomedical subjects

Susan E Wert

Publications and source records attributed to Susan E Wert.

28 records · Page 2Linked to original sources

PubMed2004

Immunohistochemical localization of Foxa1 and Foxa2 in mouse embryos and adult tissues.

Members of the Forkhead box (Fox) transcription factors family Foxa1 (Hnf-3 alpha), Foxa2 (Hnf-3 beta) are known to influence gene expression in endodermally derived tissues including lung, liver, pancreas, stomach, and intestine. In the present study, we have generated highly specific antibodies for Foxa1 and Foxa2 and determined their expression patterns in the developing and adult mouse. Foxa1 and Foxa2 were detected in the nuclei of tissues derived from both foregut and hindgut endoderm (liver, lung, pancreas, stomach, intestine, prostate and bladder). Foxa2 and Foxa1 were also detected in organs deriving from ectodermal (several brain structures and olfactory epithelium) and mesodermal origins (kidney, vagina and uterus, seminal and coagulating glands) during development. Colocalization and distinct sites of expression of Foxa1 and Foxa2 indicate unique as well as overlapping roles of Foxa1 or Foxa2 during morphogenesis and in the function of different adult organs.

Adult↗

PubMed2004

Stat-3 is required for pulmonary homeostasis during hyperoxia.

Acute lung injury syndromes remain common causes of morbidity and mortality in adults and children. Cellular and physiologic mechanisms maintaining pulmonary homeostasis during lung injury remain poorly understood. In the present study, the Stat-3 gene was selectively deleted in respiratory epithelial cells by conditional expression of Cre-recombinase under control of the surfactant protein C gene promoter. Cell-selective deletion of Stat-3 in respiratory epithelial cells did not alter prenatal lung morphogenesis or postnatal lung function. However, exposure of adult Stat-3-deleted mice to 95% oxygen caused a more rapidly progressive lung injury associated with alveolar capillary leak and acute respiratory distress. Epithelial cell injury and inflammatory responses were increased in the Stat-3-deleted mice. Surfactant proteins and lipids were decreased or absent in alveolar lavage material. Intratracheal treatment with exogenous surfactant protein B improved survival and lung histology in Stat-3-deleted mice during hyperoxia. Expression of Stat-3 in respiratory epithelial cells is not required for lung formation, but plays a critical role in maintenance of surfactant homeostasis and lung function during oxygen injury.

Adult↗

PubMed2003

Progressive lung disease and surfactant dysfunction with a deletion in surfactant protein C gene.

Mutations in the surfactant protein (SP)-C gene are responsible for familial and sporadic interstitial lung disease (ILD). The consequences of such mutations on pulmonary surfactant composition and function are poorly understood. To determine the effects of a mutation in the SP-C gene on surfactant, we obtained lung tissue at the time of transplantation from a 14-mo-old infant with progressive ILD. An in-frame 9-bp deletion spanning codons 91-93 in Exon 3 of the SP-C gene was present on one allele; neither parent carried this deletion. SP-C mRNA was present in normal size and amount. By immunofluorescence, proSP-C was aggregated within alveolar Type II cells in a compartment separate from SP-B. In airway surfactant, there was little or no mature SP-B or SP-C; SP-A content was increased. Minimum surface tension was increased (20 mN/m, normal < 5 mN/m). Type II cells contained normal and disorganized appearing lamellar bodies by electron microscopy. This spontaneous deletion on one allele of the SP-C gene was associated with sporadic ILD and abnormalities in surfactant composition and function. We propose that a dominant negative effect on surfactant protein metabolism and function results from aggregation of misfolded proSP-C and subsequent cell injury and inflammation.

Adult↗

PubMed2003

Expression of a human surfactant protein C mutation associated with interstitial lung disease disrupts lung development in transgenic mice.

Surfactant Protein C (SP-C) is a secreted transmembrane protein that is exclusively expressed by alveolar type II epithelial cells of the lung. SP-C associates with surfactant lipids to reduce surface tension within the alveolus, maintaining lung volume at end expiration. Mutations in the gene encoding SP-C (SFTPC) have recently been linked to chronic lung disease in children and adults. The goal of this study was to determine whether a disease-linked mutation in SFTPC causes lung disease in transgenic mice. The SFTPC mutation, designated g.1728 G --> A, results in the deletion of exon4, generating a truncated form of SP-C (SP-C(Deltaexon4)). cDNA encoding SP-C(Deltaexon4) was constitutively expressed in type II epithelial cells of transgenic mice. Viable F0 transgene-positive mice were not generated after two separate rounds of pronuclear injections. Histological analysis of lung tissue harvested from embryonic day 17.5 F0 transgene-positive fetuses revealed that SP-C(Deltaexon4) caused a dose-dependent disruption in branching morphogenesis of the lung associated with epithelial cell cytotoxicity. Transient expression of SP-C(Deltaexon4) in isolated type II epithelial cells or HEK293 cells resulted in incomplete processing of the mutant proprotein, a dose-dependent increase in BiP transcription, trapping of the proprotein in the endoplasmic reticulum, and rapid degradation via a proteasome-dependent pathway. Taken together, these data suggest that the g.1728 G --> A mutation causes misfolding of the SP-C proprotein with subsequent induction of the unfolded protein response and endoplasmic reticulum-associated degradation pathways ultimately resulting in disrupted lung morphogenesis.

Animals↗

PubMed2003

Pulmonary surfactant protein A, B, and C mRNA and protein expression in the nitrofen-induced congenital diaphragmatic hernia rat model.

Neonates with congenital diaphragmatic hernia (CDH) suffer from a diaphragmatic defect, lung hypoplasia, and pulmonary hypertension, with poor lung function forming the major clinical challenge. Despite prenatal diagnosis and advanced postnatal treatment strategies, the mortality rate of CDH is still high. CDH has been subject of extensive research over the past decades, but its etiology remains unknown. A major problem with CDH is the failure to predict the individual response to treatment modalities like high-frequency ventilation, inhaled nitric oxide, and extracorporeal membrane oxygenation. In this study, we tested the possibility that CDH lungs are surfactant protein deficient, which could explain the respiratory failure and difficulties in treating CDH infants. We investigated this hypothesis in the nitrofen-induced CDH rat model and assessed the cellular concentrations of surfactant protein (SP)-A, -B, and -C mRNA with a quantitative radioactive in situ hybridization technique. No differences were observed between control and CDH lungs for SP mRNA expression patterns. The cellular concentration (mean OD) of SP-A and SP-B mRNA was similar at all stages whereas the mean OD of SP-C mRNA and the volume fraction of cells (% Area) expressing SP mRNA was higher in CDH lungs at term. Immunohistochemical analysis revealed no differences between control and CDH lungs for SP protein expression. No differences in the mean OD or % Area for the SP mRNAs were found between the ipsi- and contralateral side of CDH lungs. We conclude that there is no primary deficiency of surfactant proteins in the nitrofen-induced CDH rat model.

Animals↗

PubMed2003

beta-Catenin is required for specification of proximal/distal cell fate during lung morphogenesis.

The lungs are divided, both structurally and functionally, into two distinct components, the proximal airways, which conduct air, and the peripheral airways, which mediate gas exchange. The mechanisms that control the specification of these two structures during lung development are currently unknown. Here we show that beta-catenin signaling is required for the formation of the distal, but not the proximal, airways. When the gene for beta-catenin was conditionally excised in epithelial cells of the developing mouse lung prior to embryonic day 14.5, the proximal lung tubules grew and differentiated appropriately. The mice, however, died at birth because of respiratory failure. Analysis of the lungs by in situ hybridization and immunohistochemistry, using molecular markers of the epithelial and mesenchymal components of both proximal and peripheral airways, showed that the lungs were composed primarily of proximal airways. These observations establish, for the first time, both the sites and timing of specification of the proximal and peripheral airways in the developing lung, and that beta-catenin is one of the essential components of this specification.

Animals↗

PubMed2003

TTF-1 phosphorylation is required for peripheral lung morphogenesis, perinatal survival, and tissue-specific gene expression.

Thyroid transcription factor-1 (TTF-1) is a 43-kDa, phosphorylated member of the Nkx2 family of homeodomain-containing proteins expressed selectively in lung, thyroid, and the central nervous system. To assess the role of TTF-1 and its phosphorylation during lung morphogenesis, mice bearing a mutant allele, in which seven serine phosphorylation sites were mutated, Titf1PM/PM, were generated by homologous recombination. Although heterozygous Titf1PM/+ mice were unaffected, homozygous Titf1PM/PM mice died immediately following birth. In contrast to Titf1 null mutant mice, which lack peripheral lung tissues, bronchiolar and peripheral acinar components of the lung were present in the Titf1PM/PM mice. Although lobulation and early branching morphogenesis were maintained in the mutant mice, abnormalities in acinar tubules and pulmonary hypoplasia indicated defects in lung morphogenesis later in development. Although TTF-1PM protein was readily detected within the nuclei of pulmonary epithelial cells at sites and abundance consistent with that of endogenous TTF-1, expression of a number of known TTF-1 target genes, including surfactant proteins and secretoglobulin 1A, was variably decreased in the mutant mice. Vascular endothelial growth factor mRNA was decreased in association with decreased formation of peripheral pulmonary blood vessels. Genes mediating surfactant homeostasis, vasculogenesis, host defense, fluid homeostasis, and inflammation were highly represented among those regulated by TTF-1. Thus, in contrast to the null Titf1 mutation, the Titf1PM/PM mutant substantially restored lung morphogenesis. Direct and indirect transcriptional targets of TTF-1 were identified that are likely to play important roles in lung formation and function.

Animals↗

PubMed2002

Early restriction of peripheral and proximal cell lineages during formation of the lung.

To establish the timing of lineage restriction among endodermal derivatives, we developed a method to label permanently subsets of lung precursor cells at defined times during development by using Cre recombinase to activate floxed alkaline phosphatase or green fluorescent protein genes under control of doxycycline-dependent surfactant protein C promoter. Extensive or complete labeling of peripheral lung, thyroid, and thymic epithelia, but not trachea, bronchi, or gastrointestinal tract occurred when mice were exposed to doxycycline from embryonic day (E) 4.5 to E6.5. Nonoverlapping cell lineages of conducting airways (trachea and bronchi), as distinct from those of peripheral airways (bronchioles, acini, and alveoli), were established well before formation of the definitive lung buds at E9-9.5. At E11.5, the labeled precursors of peripheral lung were restricted to relatively few cells along the bronchial tubes and clusters in bronchial tips and lateral buds. Thereafter, these cells underwent marked expansion to form the entire gas-exchange region in the lung. This study demonstrates early restriction of endodermal progenitor cells forming peripheral as compared with proximal airways, identifies distinct cell lineages in conducting airways, and distinguishes neuroepithelial and tracheal-bronchial gland cell lineages from those lining peripheral regions of the lung. This system for conditional gene addition or deletion is useful for the study of lung morphogenesis and gene function in vivo, and identifies progenitor cells that may serve as useful targets for cell or gene replacement for pulmonary disorders.

Animals↗

PubMed2002

Fibroblast growth factor 18 influences proximal programming during lung morphogenesis.

The structure and functions of the airways of the lung change dramatically along their lengths. Large-diameter conducting airways are supported by cartilaginous rings and smooth muscle tissue and are lined by ciliated and secretory epithelial cells that are involved in mucociliary clearance. Smaller peripheral airways formed during branching morphogenesis are lined by cuboidal and squamous cells that facilitate gas exchange to a network of fine capillaries. The factors that mediate formation of these changing cell types and structures along the length of the airways are unknown. We report here that conditional expression of fibroblast growth factor (FGF)-18 in epithelial cells of the developing lung caused the airway to adopt structural features of proximal airways. Peripheral lung tubules were markedly diminished in numbers, whereas the size and extent of conducting airways were increased. Abnormal smooth muscle and cartilage were found in the walls of expanded distal airways, which were accompanied by atypically large pulmonary blood vessels. Expression of proteins normally expressed in peripheral lung tubules, including SP-B and pro-SP-C, was inhibited. FGF-18 mRNA was detected in normal mouse lung in stromal cells surrounding proximal airway cartilage and in peripheral lung mesenchyme. Effects were unique to FGF-18 because expression of other members of the FGF family had different consequences. These data show that FGF-18 is capable of enhancing proximal and inhibiting peripheral programs during lung morphogenesis.

Animals↗

PubMed2002

Increased expression of thyroid transcription factor-1 (TTF-1) in respiratory epithelial cells inhibits alveolarization and causes pulmonary inflammation.

Thyroid transcription factor-1 (TTF-1), a member of the Nkx2 family of homeodomain-containing transcription factors, is expressed in the epithelium of the lung. TTF-1 is a critical regulator of transcription for the surfactant proteins (SP) A, B, and C and is essential for lung morphogenesis. Sites and levels of TTF-1 expression vary during lung morphogenesis and following injury. In order to determine the role of TTF-1 in lung formation, transgenic mice were generated in which TTF-1 was expressed in respiratory epithelial cells of wild-type and Ttf1 null mutant (-/-) mice, using the lung-specific SP-C promoter. The SP-C-Ttf1 transgene did not rescue the severe pulmonary hypoplasia characteristic of the Ttf1 (-/-) mice. Increased expression of TTF-1, however, caused dose-dependent alterations in postnatal lung morphology of wild-type mice. Modest overexpression of TTF-1 caused type II cell hyperplasia and increased the cellular content of SP-B. In contrast, higher expression levels of TTF-1 disrupted alveolar septation, causing emphysema. In mice with the highest transgene expression, TTF-1 caused severe inflammation, pulmonary fibrosis, respiratory failure, and death, associated with eosinophil infiltration and increased expression of eotaxin and IL-6. Increased expression of TTF-1 altered alveolarization and caused chronic pulmonary inflammation, demonstrating that precise regulation of TTF-1 is critical for homeostasis in the postnatal lung.

Animals↗