TGF-beta1 is an autocrine mediator of renal tubular epithelial cell growth and collagen IV production.
Recent studies in cultured cells have provided evidence that a variety of pathobiologic stimuli, including high glucose, angiotensin II, and thromboxane A(2), trigger a signaling pathway leading to autocrine induction of TGF-beta1. TGF-beta1 production through this pathway may profoundly affect cell growth, matrix synthesis, and response to injury. This study examines the role of autocrine versus exogenously added TGF-beta1 in cellular proliferation and collagen IV production, critical targets of TGF-beta1 signaling, using renal cells derived from TGF-beta1 knockout (KO) animals or wild-type (WT) controls. Growth of WT and KO cells was assessed by cell counting and [(3)H]thymidine uptake. Basal and TGF-beta1-stimulated collagen production was assessed by Northern and Western blotting; transcriptional activity of the alpha1(IV) collagen gene was assessed by transient transfection analysis. KO cells grew at a faster rate than WT cells carefully matched for plating density and passage number. This increased growth rate was paralleled by increases in [(3)H]thymidine uptake. KO cells expressed lower levels of the cell cycle inhibitors p21 and p27 than WT cells. KO cells failed to express TGF-beta1, as expected. Basal TGF-beta3 mRNA levels were higher in KO cells than in WT cells. WT cells expressed higher basal levels of TGF-beta2 mRNA than KO cells. Basal alpha1(IV) and alpha2(IV) collagen mRNA and protein expression were significantly lower in KO cells than WT cells. Administration of exogenous TGF-beta1 induced collagen IV production in both KO and WT cells. Although basal transcriptional activity of an alpha1(IV) collagen-CAT construct was lower in KO cells than WT cells, administration of exogenous TGF-beta1 was associated with significant increases in transcriptional activity of this construct in both KO and WT cells. These studies provide evidence that autocrine production of TGF-beta1 may play a critical role in regulation of growth and basal collagen IV production by renal tubular epithelial cells.
Grande
Joseph P
JP
Renal Pathophysiology Laboratory, Department of Laboratory Medicine and Pathology, and Division of Nephrology, Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. grande.joseph@mayo.edu
Warner
Gina M
GM
Walker
Henry J
HJ
Yusufi
Ahad N K
AN
Cheng
Jingfei
J
Gray
Catherine E
CE
Kopp
Jeffrey B
JB
Nath
Karl A
KA
D000818:Animals; D019898:Autocrine Communication / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D024141:Collagen Type IV / Q000096:biosynthesis* / Q000235:genetics; D007684:Kidney Tubules / Q000166:cytology* / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000494:pharmacology / Q000502:physiology*; D053773:Transforming Growth Factor beta1
D024141:Collagen Type IV; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1