Related Experiment Video
Updated: May 31, 2026
Isolation of Lung Retinoid-Containing Cells by Cell Sorting
Published on: April 11, 2025
Apolipoprotein A-I, A-II, and H mRNA and protein accumulation sites in the developing lung in late gestation
Mélissa Côté1, Pierre R Provost, Yves Tremblay
1Reproduction Axis, Perinatal and Child Health, Rm T-1-49, CHUQ Research Center, Québec City, Québec, Canada. yves.tremblay@crchul.ulaval.ca.
Background:
Expression of apolipoprotein A-I (apoA-I), A-II, and H was previously observed at 16 to 50-fold higher levels in the fetal than the adult mouse lung. Here, sites of apoA-I, A-II, and H mRNA and protein accumulation were determined in mouse fetal lungs by in situ hybridization and immunohistochemistry in late gestation.
Results:
Expression sites vary for the three genes and change for the distal epithelium before the end of the canalicular stage, thus where and when the surge of surfactant synthesis occurs. Messenger of apoH, but not those of apoA-I and A-II, was also observed in the proximal epithelium and smooth muscles surrounding arteries. In contrast to apoC-II protein, none of the three studied apolipoproteins accumulated within secretory granule-like structures. Immunohistochemistry revealed that apoA-I and apoH accumulated mainly in capillaries. Three different positive signals with the anti-apoA-II antibody were found: one transient signal in the nucleus of a portion of mesenchymal cells, a second at lower levels throughout the mesenchyme, and another in capillaries with a specific increase from gestation day 17.5/18.5.
Conclusion:
Temporal and geographic co-expression of apoAI, AII, and H genes with surfactant production site suggests that the three apolipoproteins are secreted to play roles supporting the lung-specific surfactant lipid-related metabolism.
Insights
Apolipoprotein A-I, A-II, and H are highly expressed in fetal mouse lungs, particularly near surfactant production sites. These apolipoproteins likely support lung-specific lipid metabolism during development.
Area of Science:
- Pulmonary Biology
- Molecular Biology
- Developmental Biology
Background:
- Apolipoprotein A-I (apoA-I), A-II, and H expression is significantly higher in fetal mouse lungs compared to adult lungs.
- Previous studies indicated 16 to 50-fold higher levels in fetal lung tissue.
Purpose of the Study:
- To determine the specific sites of apolipoprotein A-I, A-II, and H mRNA and protein accumulation in late gestation mouse fetal lungs.
- To investigate the spatial and temporal relationship between apolipoprotein expression and lung development, particularly surfactant synthesis.
Main Methods:
- In situ hybridization to detect mRNA accumulation.
- Immunohistochemistry to identify protein localization.
- Analysis of late gestation mouse fetal lungs.
Main Results:
- Expression sites for apoA-I, A-II, and H vary and change in the distal epithelium during the canalicular stage, coinciding with surfactant synthesis.
- ApoH mRNA was found in proximal epithelium and arterial smooth muscle, unlike apoA-I and A-II.
- ApoA-I and apoH proteins primarily accumulated in capillaries, while apoA-II showed transient nuclear signals in mesenchymal cells, broader mesenchymal distribution, and increased capillary presence late in gestation.
Conclusions:
- The temporal and geographic co-expression of apoAI, AII, and H genes with surfactant production sites suggests a role for these apolipoproteins.
- These apolipoproteins are likely secreted to support lung-specific, surfactant-related lipid metabolism during fetal development.
Related Concept Videos
02:28Leaky Scanning
02:23RNA Editing
01:15Transcytosis of IgG
IgG molecules from a mother undergo transcytosis starting around 13 weeks of gestation. The amount of IgG transferred and entering the fetal blood circulation increases with...