In vitro studies on the roles of transforming growth factor-beta 1 in rat metanephric development.
BACKGROUND
The development of the permanent kidney (metanephros) involves the interplay between both positive and negative regulatory molecules. Transforming growth factor-beta1 (TGF-beta 1) has previously been shown to negatively regulate ureteric duct growth. However, its potential role in nephron development and glomerulogenesis has been largely ignored.


METHODS
In situ hybridization and reverse transcription-polymerase chain reaction were employed to examine the temporal and spatial localization of TGF-beta 1 mRNA and a TGF-beta type I receptor (activin-like receptor kinase-5; ALK-5) mRNA in developing rat metanephroi. The addition of exogenous TGF-beta 1 to rat metanephric organ culture at different time points was used to examine the role of TGF-beta 1 in ureteric duct growth and nephron development.


RESULTS
TGF-beta 1 mRNA did not colocalize with ALK-5 mRNA. Instead, TGF-beta1 mRNA colocalized with the TGF-beta type II receptor mRNA. The addition of recombinant human TGF-beta 1 to rat metanephric organ culture at the beginning of the culture period inhibited total metanephric growth and the growth of the ureteric tree, resulting in a decrease in nephron number. Similarly, the addition of TGF-beta 1 to metanephroi after 48 hours of culture inhibited ureteric duct growth, decreasing nephron number. The addition of TGF-beta 1 at days 0 or 2 of culture promoted hypertrophy of the renal capsule.


CONCLUSIONS
These findings confirm that TGF-beta 1 inhibits ureteric duct growth and thereby nephron endowment in developing rat metanephroi in vitro. However, TGF-beta 1 does not appear to play a significant role in nephron development per se once the epithelial vesicle has formed.
Clark
A T
AT
Department of Pathology, Baylor College of Medicine, Houston, Texas, USA.
Young
R J
RJ
Bertram
J F
JF
D030201:Activin Receptors, Type I; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D017403:In Situ Hybridization; D007668:Kidney / Q000187:drug effects / Q000196:embryology* / Q000502:physiology; D007678:Kidney Glomerulus / Q000187:drug effects / Q000196:embryology / Q000502:physiology; D008297:Male; D009924:Organ Culture Techniques; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*
D017931:DNA Primers; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625843:Tgfbr1 protein, rat