BACKGROUND/AIMS: Factors released during liver injury, such as platelet derived growth factor-BB (PDGF), promote accumulation of myofibroblastic hepatic stellate cells (MFB) that drive the pathogenesis of cirrhosis. The hedgehog (Hh) pathway regulates remodeling of other injured tissues. This study evaluates the hypothesis that autocrine production of Sonic hedgehog (Shh) promotes MFB growth. METHODS: Primary rat hepatic stellate cells (HSC) were treated without or with PDGF, a pharmacologic inhibitor of PDGF-regulated kinases, adenovirus expressing activated or dominant negative AKT, or Hh signaling inhibitors. Shh production, expression of Hh inhibitors and target genes, and HSC growth were assessed. RESULTS: HSC expressed Shh, Hh pathway components, and the Hh inhibitor, Hip. During culture Hip expression fell, Shh production increased, and Hh target gene expression was induced. Neutralizing Shh antibodies promoted apoptosis. Adding PDGF increased Shh expression and MFB growth. Both processes followed activation of AKT and were abrogated by AKT inhibitors. Adenoviral delivery of activated AKT up-regulated Shh expression, demonstrating a direct role for AKT in regulating Shh expression. Shh-neutralizing antibodies and other Hh pathway inhibitors blocked the mitogenic effects of PDGF. CONCLUSIONS: These results identify Shh as an autocrine growth factor for MFB and suggest a role for Hh signaling in the pathogenesis of cirrhosis.
BACKGROUND/AIMS: Factors released during liver injury, such as platelet derived growth factor-BB (PDGF), promote accumulation of myofibroblastic hepatic stellate cells (MFB) that drive the pathogenesis of cirrhosis. The hedgehog (Hh) pathway regulates remodeling of other injured tissues. This study evaluates the hypothesis that autocrine production of Sonic hedgehog (Shh) promotes MFB growth. METHODS: Primary rat hepatic stellate cells (HSC) were treated without or with PDGF, a pharmacologic inhibitor of PDGF-regulated kinases, adenovirus expressing activated or dominant negative AKT, or Hh signaling inhibitors. Shh production, expression of Hh inhibitors and target genes, and HSC growth were assessed. RESULTS: HSC expressed Shh, Hh pathway components, and the Hh inhibitor, Hip. During culture Hip expression fell, Shh production increased, and Hh target gene expression was induced. Neutralizing Shh antibodies promoted apoptosis. Adding PDGF increased Shh expression and MFB growth. Both processes followed activation of AKT and were abrogated by AKT inhibitors. Adenoviral delivery of activated AKT up-regulated Shh expression, demonstrating a direct role for AKT in regulating Shh expression. Shh-neutralizing antibodies and other Hh pathway inhibitors blocked the mitogenic effects of PDGF. CONCLUSIONS: These results identify Shh as an autocrine growth factor for MFB and suggest a role for Hh signaling in the pathogenesis of cirrhosis.
Authors: Jason K Sicklick; Yin-Xiong Li; Alaa Melhem; Eva Schmelzer; Marzena Zdanowicz; Jiawen Huang; Montserrat Caballero; Jeff H Fair; John W Ludlow; Randall E McClelland; Lola M Reid; Anna Mae Diehl Journal: Am J Physiol Gastrointest Liver Physiol Date: 2005-12-01 Impact factor: 4.052
Authors: Liu Yang; Che-Chang Chan; Oh-Sang Kwon; Songling Liu; Jason McGhee; Stephen A Stimpson; Lihong Z Chen; W Wallace Harrington; William T Symonds; Don C Rockey Journal: Am J Physiol Gastrointest Liver Physiol Date: 2006-06-22 Impact factor: 4.052
Authors: Jason K Sicklick; Yin-Xiong Li; Aruna Jayaraman; Rajesh Kannangai; Yi Qi; Perumal Vivekanandan; John W Ludlow; Kouros Owzar; Wei Chen; Michael S Torbenson; Anna Mae Diehl Journal: Carcinogenesis Date: 2005-12-08 Impact factor: 4.944
Authors: Natalia A Riobó; Ke Lu; Xingbin Ai; Gwendolyn M Haines; Charles P Emerson Journal: Proc Natl Acad Sci U S A Date: 2006-03-10 Impact factor: 11.205