title: Disruption of THY-1 signaling in alveolar lipofibroblasts in experimentally induced congenital diaphragmatic hernia.
abstract: OBJECTIVE
  Pulmonary hypoplasia (PH), characterized by alveolar immaturity, remains the main cause of neonatal mortality and long-term morbidity in infants with congenital diaphragmatic hernia (CDH). Lipid-containing interstitial fibroblasts (LIFs) are critically important for normal alveolar development. Thymocyte antigen 1 (Thy-1) is a highly expressed cell-surface protein in this specific subset of lung fibroblasts, which plays a key role in fetal alveolarization by coordinating the differentiation and lipid homeostasis of alveolar LIFs. Thy-1 increases the lipid content of LIFs by upregulation of adipocyte differentiation-related protein (ADRP), a lipogenic molecular marker characterizing pulmonary LIFs. Thy-1 (-/-) mice further show impaired alveolar development with reduced proliferation of pulmonary LIFs, resulting in a PH-similar phenotype. We hypothesized that pulmonary Thy-1 signaling is disrupted in experimentally induced CDH, which may has an adverse effect on the lipid content of alveolar LIFs.
  
  
  METHODS
  Timed-pregnant Sprague-Dawley rats were treated with either 100 mg nitrofen or vehicle on embryonic day 9.5 (E9.5). Fetuses were killed on E21.5, and lungs were divided into controls (n = 14) and CDH-associated PH (n = 14). Pulmonary gene expression levels of Thy-1 and ADRP were assessed by quantitative real-time PCR. ADRP immunohistochemistry and oil-red-O staining were used to localize alveolar LIF expression and lipid droplets. Immunofluorescence double staining for Thy-1 and oil-red-O was performed to evaluate Thy-1 expression and lipid content in alveolar LIFs.
  
  
  RESULTS
  Radial alveolar count was significantly reduced in CDH-associated PH with significant downregulation of pulmonary Thy-1 and ADRP mRNA expression compared to controls. ADRP immunoreactivity and lipid droplets were markedly diminished in alveolar interstitial cells, which coincided with decreased alveolar LIF expression in CDH-associated PH compared to controls. Confocal laser scanning microscopy confirmed markedly decreased Thy-1 expression and lipid content in alveolar LIFs of CDH-associated PH compared to controls.
  
  
  CONCLUSIONS
  Our study provides strong evidence that disruption of pulmonary Thy-1 signaling results in reduced lipid droplets in alveolar LIFs and may thus contribute to PH in the nitrofen-induced CDH model. Treatment modalities aimed at increasing lipid content in alveolar LIFs may therefore have a therapeutic potential in attenuating CDH-associated PH.
authors.affiliation: National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin 12, Ireland.
authors.forename: Florian
authors.initials: F
authors.lastname: Friedmacher
authors.forename: Alejandro Daniel
authors.initials: AD
authors.lastname: Hofmann
authors.forename: Hiromizu
authors.initials: H
authors.lastname: Takahashi
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Takahashi
authors.forename: Jan-Hendrik
authors.initials: JH
authors.lastname: Gosemann
authors.forename: Prem
authors.initials: P
authors.lastname: Puri
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics; D006548:Hernia, Diaphragmatic / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D065630:Hernias, Diaphragmatic, Congenital; D051379:Mice; D011247:Pregnancy; D011650:Pulmonary Alveoli / Q000196:embryology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000235:genetics*; D018800:Thy-1 Antigens / Q000235:genetics*; D015854:Up-Regulation
chemical_list: D018800:Thy-1 Antigens