Apolipoprotein A-I, A-II, and H mRNA and protein accumulation sites in the developing lung in late gestation
1 Reproduction Axis, Perinatal and Child Health, Rm T-1-49, CHUQ Research Center, Québec City, Québec, Canada
2 Department of Obstetrics and Gynecology, Faculty of Medicine, Laval University, Québec City, Québec, Canada
3 Centre de Recherche en Biologie de la Reproduction (CRBR), Laval University, Québec City, Québec, Canada
BMC Research Notes 2011, 4:235 doi:10.1186/1756-0500-4-235Published: 14 July 2011
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.
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.
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.