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Intact signaling by transforming growth factor beta is not required for termination of liver regeneration in mice

Oe, S; Lemmer, ER; Conner, EA; Factor, VM; Levéen, Per LU ; Larsson, Jonas LU ; Karlsson, Stefan LU and Thorgeirsson, SS (2004) In Hepatology 40(5). p.1098-1105
Abstract
Transforming growth factor beta (TGF-beta) is a potent inhibitor of hepatocyte proliferation in vitro and is suggested to be a key negative regulator of liver growth. To directly address the role of TGF-beta signaling in liver regeneration in vivo, the TGF-beta type II receptor gene (Tgfbr2) was selectively deleted in hepatocytes by crossing "floxed" Tgfbr2 conditional knockout mice with transgenic mice expressing Cre under control of the albumin promoter. Hepatocytes isolated from liver-specific Tgfbr2 knockout (R2LivKO) mice were refractory to the growth inhibitory effects of TGF-beta1. The peak of DNA synthesis after 70% partial hepatectomy occurred earlier (36 vs. 48 hours) and was 1.7-fold higher in R2LivKO mice compared with... (More)
Transforming growth factor beta (TGF-beta) is a potent inhibitor of hepatocyte proliferation in vitro and is suggested to be a key negative regulator of liver growth. To directly address the role of TGF-beta signaling in liver regeneration in vivo, the TGF-beta type II receptor gene (Tgfbr2) was selectively deleted in hepatocytes by crossing "floxed" Tgfbr2 conditional knockout mice with transgenic mice expressing Cre under control of the albumin promoter. Hepatocytes isolated from liver-specific Tgfbr2 knockout (R2LivKO) mice were refractory to the growth inhibitory effects of TGF-beta1. The peak of DNA synthesis after 70% partial hepatectomy occurred earlier (36 vs. 48 hours) and was 1.7-fold higher in R2LivKO mice compared with controls. Accelerated S-phase entry by proliferating R2LivKO hepatocytes coincided with the hyperphosphorylation of Rb protein and the early upregulation of cyclin D1 and cyclin E. However, by 120 hours after partial hepatectomy, hepatocyte proliferation was back to baseline in both control and R2LivKO liver. Regenerating R2LivKO liver showed evidence of increased signaling by activin A and persistent activity of the Smad pathway. Blockage of activin A signaling by the specific inhibitor follistatin resulted in increased hepatocyte proliferation at 120 hours, particularly in R2LivKO livers. In conclusion, TGF-beta regulates G(1) to S phase transition of hepatocytes, but intact signaling by TGF-beta is not required for termination of liver regeneration. Increased signaling by activin A may compensate to regulate liver regeneration when signaling through the TGF-beta pathway is abolished, and may be a principal factor in the termination of liver regeneration. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Hepatology
volume
40
issue
5
pages
1098 - 1105
publisher
John Wiley & Sons
external identifiers
  • pmid:15389868
  • wos:000225049500010
  • scopus:7044228192
ISSN
1527-3350
DOI
10.1002/hep.20426
language
English
LU publication?
yes
id
753aca6d-31c3-417c-a830-f3ec8590f2fb (old id 261774)
date added to LUP
2007-10-29 10:25:49
date last changed
2017-09-03 04:38:19
@article{753aca6d-31c3-417c-a830-f3ec8590f2fb,
  abstract     = {Transforming growth factor beta (TGF-beta) is a potent inhibitor of hepatocyte proliferation in vitro and is suggested to be a key negative regulator of liver growth. To directly address the role of TGF-beta signaling in liver regeneration in vivo, the TGF-beta type II receptor gene (Tgfbr2) was selectively deleted in hepatocytes by crossing "floxed" Tgfbr2 conditional knockout mice with transgenic mice expressing Cre under control of the albumin promoter. Hepatocytes isolated from liver-specific Tgfbr2 knockout (R2LivKO) mice were refractory to the growth inhibitory effects of TGF-beta1. The peak of DNA synthesis after 70% partial hepatectomy occurred earlier (36 vs. 48 hours) and was 1.7-fold higher in R2LivKO mice compared with controls. Accelerated S-phase entry by proliferating R2LivKO hepatocytes coincided with the hyperphosphorylation of Rb protein and the early upregulation of cyclin D1 and cyclin E. However, by 120 hours after partial hepatectomy, hepatocyte proliferation was back to baseline in both control and R2LivKO liver. Regenerating R2LivKO liver showed evidence of increased signaling by activin A and persistent activity of the Smad pathway. Blockage of activin A signaling by the specific inhibitor follistatin resulted in increased hepatocyte proliferation at 120 hours, particularly in R2LivKO livers. In conclusion, TGF-beta regulates G(1) to S phase transition of hepatocytes, but intact signaling by TGF-beta is not required for termination of liver regeneration. Increased signaling by activin A may compensate to regulate liver regeneration when signaling through the TGF-beta pathway is abolished, and may be a principal factor in the termination of liver regeneration.},
  author       = {Oe, S and Lemmer, ER and Conner, EA and Factor, VM and Levéen, Per and Larsson, Jonas and Karlsson, Stefan and Thorgeirsson, SS},
  issn         = {1527-3350},
  language     = {eng},
  number       = {5},
  pages        = {1098--1105},
  publisher    = {John Wiley & Sons},
  series       = {Hepatology},
  title        = {Intact signaling by transforming growth factor beta is not required for termination of liver regeneration in mice},
  url          = {http://dx.doi.org/10.1002/hep.20426},
  volume       = {40},
  year         = {2004},
}