Différences sexuelles, androgènes et glucocorticoïdes dans le poumon foetal durant une période gestationnelle tardive qui chevauche la montée de la production du surfactant pulmonaire

Authors: Simard, Marc
Advisor: Provost, PierreTremblay, Yves
Abstract: Respiratory distress syndrome (RDS) is more frequent in male neonates than female neonates. Androgens and glucocorticoids are known to delay and accelerate, respectively, the fetal lung maturation. Firstly, we studied the sex differences in the mouse fetal lung transcriptome during a gestational period that overlaps the surge of surfactant synthesis, which occurs earlier in females than in males. Using DNA microarrays, 88 transcripts showing a sex difference in expression at gestational days (GD) 15.5, 16.5, or 17.5 were identified. Those genes were associated to several functional categories, including hormone metabolism and regulation, apoptosis, transcriptional regulation, and lipid metabolism, and are candidates for roles in lung maturation and in the physiopathology of RDS. Secondly, the expression of 17β-hydroxysteroid dehydrogenases (17βHSD) type 2 and 5, which are respectively involved in androgen inactivation and synthesis, and of the androgen receptor (AR), was characterized in human fetal lungs. Statistically significant relationships between expression levels and gestational age were observed. In particular, 17βHSD2 and AR were co-localized in epithelial cells, while 17βHSD5 was localized in a subset of epithelial cells mostly in conducting zones. AR protein levels showed an important interindividual variability. The obtained results support the presence of a local androgen metabolism and a fine-tuning of AR occupancy in human male and female fetal lungs during a gestational period associated with high-risk premature birth. Thirdly, the expression of hypothalamic-pituitary-adrenal (HPA) axis-related genes was quantified and localized in murine fetal lungs at GD 15.5, 16.5, and 17.5. Also, the capability of corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) to stimulate the pulmonary expression of enzymes involved in the “adrenal” pathway of glucocorticoid synthesis was addressed, as well as the glucocorticoid production. Several distinct gene expression profiles were established, the incubation of fetal lung explants with CRH led to increased levels of 21-hydroxylase gene expression, whereas deoxycorticosterone accumulation was detected. The observed temporal and spatial modulations suggest roles for HPA axis-related genes in the developing lung.
Document Type: Thèse de doctorat
Issue Date: 2011
Open Access Date: 18 April 2018
Permalink: http://hdl.handle.net/20.500.11794/22909
Grantor: Université Laval
Collection:Thèses et mémoires

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