title: Effects of dexamethasone exposure on rat metanephric development: in vitro and in vivo studies.
abstract: Maternal administration of dexamethasone (DEX) for 48 h early in rat kidney development results in offspring with a reduced nephron endowment. However, the mechanism through which DEX inhibits nephrogenesis is unknown. In this study, we hypothesized that DEX may indirectly inhibit nephrogenesis by inhibiting ureteric branching morphogenesis. Whole metanephroi from embryonic day 14.5 (E14.5) rat embryos were cultured in the presence of DEX. DEX (10(-5) M) exposure for 2 days significantly inhibited ureteric branching compared with metanephroi grown in control media or DEX (10(-7) M). Culturing metanephroi for a further 3 days (in control media only) reduced total glomerular number in metanephroi previously exposed to DEX (10(-5) M) or (10(-7) M) compared with control cultures. Expression of genes known to regulate ureteric branching morphogenesis was determined by real-time PCR in metanephroi after 2 days in culture. DEX exposure in vitro decreased expression of glial cell line-derived neurotrophic factor (GDNF) and increased expression of bone morphogenetic protein-4 (BMP-4) and transforming growth factor-beta1 (TGF-beta1). Similar gene expression changes were found in E16.5 metanephroi in which the dam had been exposed to 2 days of DEX (0.2 mg.kg(-1).day(-1)) at E14.5/15.5 in vivo. However, in kidneys collected at E20.5 after in vivo exposure for 2 days, GDNF expression was increased and BMP-4 and TGF-beta1 expression decreased suggesting a biphasic response in gene expression to DEX exposure. These results show for the first time that inhibition of ureteric branching morphogenesis may be a key mechanism through which DEX exposure results in a reduced nephron endowment.
authors.affiliation: Dept. of Anatomy and Cell Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Reetu R
authors.initials: RR
authors.lastname: Singh
authors.forename: Karen M
authors.initials: KM
authors.lastname: Moritz
authors.forename: John F
authors.initials: JF
authors.lastname: Bertram
authors.forename: Luise A
authors.initials: LA
authors.lastname: Cullen-McEwen
mesh_terms: D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D057912:Angiotensin II Type 2 Receptor Blockers; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000378:metabolism; D007150:Immunohistochemistry; D007668:Kidney / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D037102:Lectins / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D014599:Uterus / Q000196:embryology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D057912:Angiotensin II Type 2 Receptor Blockers; D000893:Anti-Inflammatory Agents; C525811:Bmp4 protein, rat; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D051100:Glial Cell Line-Derived Neurotrophic Factor; D037102:Lectins; D053773:Transforming Growth Factor beta1; D003907:Dexamethasone