Related Experiment Video
Updated: Jun 22, 2026
A Murine Model of Fetal Exposure to Maternal Inflammation to Study the Effects of Acute Chorioamnionitis on Newborn Intestinal Development
Published on: June 24, 2020
Endotoxin alters early fetal lung morphogenesis
Christopher S Muratore1, Francois I Luks, Yonghong Zhou
1Department of Surgery, Pediatric Surgery, Hasbro Children's Hospital, Brown University, Providence, Rhode Island 02095, USA. christopher_muratore@brown.edu
Insights
Early gestational exposure to lipopolysaccharides (LPS) impairs fetal rat lung development, affecting branching and potentially leading to bronchopulmonary dysplasia. This inflammation impacts endothelial cells and alters gene expression crucial for lung formation.
Area of Science:
- Developmental Biology
- Pulmonology
- Toxicology
Background:
- Premature lung hypoplasia and immaturity are exacerbated by inflammatory stimuli.
- Bronchopulmonary dysplasia can result from acute lung injury and metabolic issues.
- Previous studies focused on late gestational inflammation; this study examines early gestational effects.
Purpose of the Study:
- To investigate the impact of early gestational endotoxin exposure on fetal rat lung branching morphogenesis.
- To determine if lipopolysaccharides (LPS) affect lung development during the pseudoglandular stage.
Main Methods:
- Fetal rat lung explants from gestational day 15 were exposed to varying doses of LPS.
- Explants were examined daily using phase microscopy and fixed for histological analysis.
- Immunohistochemistry and real-time PCR assessed endothelial cells, growth factors, and inflammatory markers.
Main Results:
- LPS exposure caused dose-dependent airway sac contraction and interstitial thickening.
- High-dose LPS led to stunted branching, thickened airways, and increased matrix deposition.
- LPS increased COX-2 and iNOS expression while decreasing FGF9, FGF10, and FGFr2 gene expression.
Conclusions:
- Early fetal LPS exposure negatively impacts lung branching morphogenesis during the pseudoglandular phase.
- Inflammation affects fetal endothelial cells and suggests an inflammatory cascade involving COX-2.
- FGF-directed mechanisms may underlie abnormal lung development due to early inflammatory stimuli.
Background:
The effects of immaturity and hypoplasia of the premature lung can be affected by proinflammatory stimuli in late gestation or the postnatal period from acute lung injury secondary to intensive ventilatory management or the metabolic consequences of surgery. These stimuli alter alveolarization and contribute to bronchopulmonary dysplasia. While prior research has focused primarily on late gestational effects of inflammation on alveolar development, we sought to study whether early gestational exposure to endotoxin affects branching morphogenesis, during the critical pseudoglandular stage of lung development.
Method:
Gestational day 15 (E15) fetal rat lung explants (term = 22 d) were treated with either 200 ng/mL or 2 microg/mL lipopolysaccharides (LPS) with controls and examined daily by phase microscopy. After 5 d, explants were fixed in 4% formaldehyde, paraffin embedded, and sectioned at 5 mum in the coronal plane. Immunohistochemical analysis was performed with platelet endothelial cell adhesion molecule (PECAM) to define endothelial cells, vascular endothelial growth factor (VEGF) to examine endothelial mitogenesis, and COX-2 antibodies as a marker for prostaglandin synthesis. Real-time PCR examined inducible nitric oxide synthase (iNOS), FGF9, FGF10, and FGFr2 gene expression. Air space fraction and airway epithelium were analyzed with Image J software.
Results:
Phase contrast microscopy and hematoxylin-eosin histology revealed progressive, dose-related changes in air sac contraction and interstitial thickening. Compared with control E15 explants, day 5 explants incubated with high dose LPS demonstrated thickened and shrunken airway sacs with stunted branching and increased matrix deposition in interstitial areas. By immunohistochemical staining, COX-2 was quantitatively increased after high dose LPS exposure, while PECAM was reduced. VEGF expression was unaltered. LPS increased iNOS, but decreased FGF9, FGF10, and FGFr2 gene expression.
Conclusions:
These data support evidence for an inflammatory effect of LPS on the early phase of lung development in the fetal rat, affecting branching morphogenesis during the pseudoglandular phase. Fetal endothelial cells are clearly affected, while COX-2 elevation suggests activation of an as yet undefined fetal pulmonary inflammatory cascade. We speculate that proinflammatory stimuli may ultimately lead to abnormal pulmonary development via fibroblastic growth factor (FGF)-directed mechanisms that affect epithelial-mesenchymal interaction and differentiation at a much earlier gestational age than was previously recognized.
