title: Notch signaling in descending thoracic aortic aneurysm and dissection.
abstract: BACKGROUND
  Descending thoracic aortic aneurysm and dissection (DTAAD) is characterized by progressive medial degeneration, which may result from excessive tissue destruction and insufficient repair. Resistance to tissue destruction and aortic self-repair are critical in preventing medial degeneration. The signaling pathways that control these processes in DTAAD are poorly understood. Because Notch signaling is a critical pathway for cell survival, proliferation, and tissue repair, we examined its activation in DTAAD.
  
  
  METHODS
  We studied descending thoracic aortic tissue from patients with sporadic thoracic aortic aneurysm (TAA; n = 14) or chronic thoracic aortic dissection (TAD; n = 16) and from age-matched organ donors (n = 12). Using western blot, real-time RT-PCR, and immunofluorescence staining, we examined aortic tissue samples for the Notch ligands Delta-like 1, Delta-like 4 (DLL1/4), and Jagged1; the Notch receptor 1 (Notch1); the Notch1 intracellular domain (NICD); and Hes1, a downstream target of Notch signaling.
  
  
  RESULTS
  Western blots and RT-PCR showed higher levels of the Notch1 protein and mRNA and the NICD and Hes1 proteins in both TAA and TAD tissues than in control tissue. However, immunofluorescence staining showed a complex pattern of Notch signaling in the diseased tissue. The ligand DLL1/4 and Notch1 were significantly decreased and NICD and Hes1 were rarely detected in medial vascular smooth muscle cells (VSMCs) in both TAA and TAD tissues, indicating downregulation of Notch signaling in aortic VSMCs. Interestingly Jagged1, NICD, and Hes1 were highly present in CD34+ stem cells and Stro-1+ stem cells in aortas from TAA and TAD patients. NICD and Hes1 were also detected in most fibroblasts and macrophages that accumulated in the aortic wall of DTAAD patients.
  
  
  CONCLUSIONS
  Notch signaling exhibits a complex pattern in DTAAD. The Notch pathway is impaired in medial VSMCs but activated in stem cells, fibroblasts, and macrophages.
authors.affiliation: Division of Cardiothoracic Surgery, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Sili
authors.initials: S
authors.lastname: Zou
authors.forename: Pingping
authors.initials: P
authors.lastname: Ren
authors.forename: Mary
authors.initials: M
authors.lastname: Nguyen
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Coselli
authors.forename: Ying H
authors.initials: YH
authors.lastname: Shen
authors.forename: Scott A
authors.initials: SA
authors.lastname: LeMaire
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D053687:Adult Stem Cells / Q000378:metabolism; D000368:Aged; D000784:Aortic Dissection / Q000378:metabolism* / Q000473:pathology; D018952:Antigens, CD34 / Q000378:metabolism; D000954:Antigens, Surface / Q000378:metabolism; D001013:Aorta, Thoracic / Q000378:metabolism* / Q000473:pathology; D017545:Aortic Aneurysm, Thoracic / Q000378:metabolism* / Q000473:pathology; D002135:Calcium-Binding Proteins; D016022:Case-Control Studies; D015536:Down-Regulation; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018952:Antigens, CD34; D000954:Antigens, Surface; D002135:Calcium-Binding Proteins; C424126:DLL4 protein, human; D036341:Intercellular Signaling Peptides and Proteins; C497761:NOTCH1 protein, human; D051881:Receptor, Notch1; C525591:STRO-1 antigen, human