title: Disruption of Notch1 induces vascular remodeling, intussusceptive angiogenesis, and angiosarcomas in livers of mice.
abstract: OBJECTIVE
  Notch signaling mediates embryonic vascular development and normal vascular remodeling; Notch1 knockout mice develop nodular regenerative hyperplasia (NRH). The pathogenesis of NRH is unclear, but has been associated with vascular injury in the liver sinusoids in clinical studies. We investigated the role of Notch1 signaling in liver sinusoidal endothelial cells (LSECs).
  
  
  METHODS
  We studied MxCre Notch1(lox/lox) mice (conditional knockout mice without tissue-specific disruption of Notch1); mice with hepatocyte-specific knockout were created by crossing Notch1(lox/lox) with AlbCre(+/-) mice. Portal vein pressure was measured; morphology of the hepatic vasculature was assessed by histologic and scanning electron microscopy analyses. We performed functional and expression analyses of isolated liver cells.
  
  
  RESULTS
  MxCre-induced knockout of Notch1 led to NRH, in the absence of fibrosis, with a persistent increase in proliferation of LSECs. Notch1 deletion led to de-differentiation, vascular remodeling of the hepatic sinusoidal microvasculature, intussusceptive angiogenesis, and dysregulation of ephrinB2/EphB4 and endothelial tyrosine kinase. Time-course experiments revealed that vascular changes preceded node transformation. MxCre Notch1(lox/lox) mice had reduced endothelial fenestrae and developed portal hypertension and hepatic angiosarcoma over time. In contrast, mice with hepatocyte-specific disruption of Notch1 had a normal phenotype.
  
  
  CONCLUSIONS
  Notch1 signaling is required for vascular homeostasis of hepatic sinusoids; it maintains quiescence and differentiation of LSECs in adult mice. Disruption of Notch1 signaling in LSECs leads to spontaneous formation of angiosarcoma, indicating its role as a tumor suppressor in the liver endothelium.
authors.affiliation: Department of Biomedicine, University Basel, Basel, Switzerland.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Dill
authors.forename: Sonja
authors.initials: S
authors.lastname: Rothweiler
authors.forename: Valentin
authors.initials: V
authors.lastname: Djonov
authors.forename: Ruslan
authors.initials: R
authors.lastname: Hlushchuk
authors.forename: Luigi
authors.initials: L
authors.lastname: Tornillo
authors.forename: Luigi
authors.initials: L
authors.lastname: Terracciano
authors.forename: Silvia
authors.initials: S
authors.lastname: Meili-Butz
authors.forename: Freddy
authors.initials: F
authors.lastname: Radtke
authors.forename: Markus H
authors.initials: MH
authors.lastname: Heim
authors.forename: David
authors.initials: D
authors.lastname: Semela
mesh_terms: D000818:Animals; D054337:Cell Dedifferentiation; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism* / Q000473:pathology; D036388:Ephrin-B2 / Q000378:metabolism; D020518:Focal Nodular Hyperplasia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005838:Genotype; D006394:Hemangiosarcoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology; D006801:Humans; D006975:Hypertension, Portal / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D008099:Liver / Q000098:blood supply* / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008855:Microscopy, Electron, Scanning; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D017082:Portal Pressure; D036224:Receptor, EphB4 / Q000378:metabolism; D051881:Receptor, Notch1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D036388:Ephrin-B2; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; C086681:Ephb4 protein, mouse; D036224:Receptor, EphB4