title: Neovessel formation promotes liver fibrosis via providing latent transforming growth factor-β.
abstract: OBJECTIVE
  Hepatic fibrosis and angiogenesis occur in parallel during the progression of liver disease. Fibrosis promotes angiogenesis via inducing vascular endothelial growth factor (VEGF) from the activated hepatic stellate cells (HSCs). In turn, increased neovessel formation causes fibrosis, although the underlying molecular mechanism remains undetermined. In the current study, we aimed to address a role of endothelial cells (ECs) as a source of latent transforming growth factor (TGF)-β, the precursor of the most fibrogenic cytokine TGF-β.
  
  
  METHODS
  After recombinant VEGF was administered to mice via the tail vein, hepatic angiogenesis and fibrogenesis were evaluated using immunohistochemical and biochemical analyses in addition to investigation of TGF-β activation using primary cultured HSCs and liver sinusoidal ECs (LSECs).
  
  
  RESULTS
  In addition to increased hepatic levels of CD31 expression, VEGF-treated mice showed increased α-smooth muscle actin (α-SMA) expression, hepatic contents of hydroxyproline, and latency associated protein degradation products, which reflects cell surface activation of TGF-β via plasma kallikrein (PLK). Liberating the PLK-urokinase plasminogen activator receptor complex from the HSC surface by cleaving a tethering phosphatidylinositol linker with its specific phospholipase C inhibited the activating latent TGF-β present in LSEC conditioned medium and subsequent HSC activation.
  
  
  CONCLUSIONS
  Neovessel formation (angiogenesis) accelerates liver fibrosis at least in part via provision of latent TGF-β that activated on the surface of HSCs by PLK, thereby resultant active TGF-β stimulates the activation of HSCs.
authors.affiliation: Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan; Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan; Drug Discovery Laboratory, Wakunaga Pharmaceutical Co., Ltd., Akitakata, Hiroshima 739-1195, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Sakata
authors.affiliation: Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Eda
authors.affiliation: Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan.
authors.forename: Eun-Seo
authors.initials: ES
authors.lastname: Lee
authors.affiliation: Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan.
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Hara
authors.affiliation: Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Imoto
authors.affiliation: Micro-signaling Regulation Technology Unit, RIKEN Center for Life Science Technologies, Wako, Saitama 351-0198, Japan. Electronic address: skojima@riken.jp.
authors.forename: Soichi
authors.initials: S
authors.lastname: Kojima
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D055166:Hepatic Stellate Cells; D007610:Kallikreins / Q000097:blood; D008103:Liver Cirrhosis / Q000097:blood / Q000209:etiology* / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009389:Neovascularization, Pathologic / Q000097:blood / Q000150:complications* / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000008:administration & dosage
chemical_list: D017077:Culture Media, Conditioned; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A; D007610:Kallikreins
keywords: Hepatic stellate cells; Liver fibrosis; Liver sinusoidal endothelial cells; Transforming growth factor-β