ABSTRACT
To investigate the role of angiotensin II (ANG II) in nephrogenesis, a developmental study of renal AT1 and AT2 receptor mRNA expression was performed in parallel with the quantitative and qualitative analysis of metanephros development in fetal lamb from 60 to 140 days of gestation. Both ANG II receptor subtypes were expressed early during nephrogenesis but displayed specific spatial and temporal distribution during gestation. High-AT2 mRNA expression took place in the outermost nephrogenic area and in the undifferentiated mesenchymal cells surrounding the ampulla; level of AT2 expression in this localization followed closely glomeruli proliferation rate and disappeared after nephrogenesis completion (>120 days). AT2 mRNA was also detected in the differentiated epithelial cells of macula densa of maturing glomeruli. Although most of AT1 mRNA labeling was found in the mesangial cells of maturing glomeruli, where it persisted after nephrogenesis completion, additional labeling was found in undifferentiated cells, in cells invading the inferior cleft of S-shaped bodies (80 days), and in medullar cells between tubules (120 days). Our results suggest that each receptor subtype has a specific role in renal morphogenesis, i.e., AT2 in mesenchymal proliferation or apoptosis and AT1 in vascular smooth muscle cells differentiation.
Subject(s)
Kidney/embryology , Receptors, Angiotensin/genetics , Animals , Fetus , Gene Expression Regulation, Developmental , In Situ Hybridization , RNA, Messenger/metabolism , SheepABSTRACT
To gain insight into the role of transforming growth factor-beta 1 (TGF-beta 1) in the development of kidney pathology following fetal obstruction, we measured TGF-beta 1 gene expression, the active peptide, and the urinary concentration in a model of fetal bilateral urinary obstruction (BUO) in sheep. Fetal lambs underwent BUO at 60 (FO-60) or 80 days (FO-80) of gestation and were studied at 120 days. Independently of the onset or duration of obstruction, all fetuses developed type IV dysplasia (IV) associated with an arrest in the nephrogenesis or hydronephrosis. Fetal glomerular filtration rate was not significantly modified, whereas sodium tubular reabsorption was significantly decreased, and urinary TGF-beta 1 concentration was elevated in hydronephrosis but not in IV. Levels of TGF-beta 1 mRNA were increased in hydronephrosis compared with normal kidneys, and active TGF-beta 1 immunoreactivity was increased in both hydronephrotic and IV kidneys. In summary, TGF-beta 1 may play a role in the development of hydronephrosis and dysplasia in kidneys following fetal BUO. Its role in the arrest of nephrogenesis observed in the IV kidneys remains to be proved.
