title: Atrial extracellular matrix remodeling and the maintenance of atrial fibrillation.
abstract: BACKGROUND
  Remodeling occurs in both ventricle and atrium in dilated cardiomyopathy and heart failure. However, the alteration of atrial extracellular matrix components during remodeling and its effect on the electrical remodeling and atrial arrhythmia have never been explored.
  
  
  RESULTS
  Atrial tissue samples of 53 explanted hearts from patients with dilated cardiomyopathy and end-stage heart failure who underwent heart transplantation were examined. Nineteen patients had permanent atrial fibrillation (PmAF), 18 had persistent AF (PsAF), and 16 had no documented AF (NAF). Sixteen donor left atria (LA) were used as controls (CNs). Western Blot analysis revealed a selective downregulation of tissue inhibitor of metalloproteinase (TIMP)-2 in PmAF and PsAF groups compared with the NAF and CN groups and an upregulation of atrial metalloproteinase (MMP)-2 that was most pronounced in the PmAF group followed by the PsAF and NAF groups. Immunofluorescent staining revealed that in the LA, type I collagen volume fraction (CVF-I) increased significantly in the PmAF group followed by the PsAF and NAF groups compared with that in CN. LA CVF-I significantly correlated with LA dimension and TIMP-2 to MMP-2 ratio. In the PsAF group, CVF-I/CVF-III ratio was significantly correlated with AF duration and the frequency of AF recurrence.
  
  
  CONCLUSIONS
  Atrial extracellular matrix remodeling manifested by the selective downregulation of TIMP-2 along with upregulation of MMP-2 and CVF-I in the atrium is associated with the development of sustained atrial fibrillation in patients with cardiomyopathy and heart failure.
authors.affiliation: Division of Cardiology, UCLA Medical Center, 10833 Le Conte Ave, 47-123 CHS, Los Angeles, CA 90095-1679, USA. lsen@mednet.ucla.edu
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.forename: Guanggen
authors.initials: G
authors.lastname: Cui
authors.forename: Fardad
authors.initials: F
authors.lastname: Esmailian
authors.forename: Mark
authors.initials: M
authors.lastname: Plunkett
authors.forename: Daniel
authors.initials: D
authors.lastname: Marelli
authors.forename: Abbas
authors.initials: A
authors.lastname: Ardehali
authors.forename: Jonah
authors.initials: J
authors.lastname: Odim
authors.forename: Hillel
authors.initials: H
authors.lastname: Laks
authors.forename: Luyi
authors.initials: L
authors.lastname: Sen
mesh_terms: D001281:Atrial Fibrillation / Q000201:enzymology / Q000209:etiology* / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism; D024061:Collagen Type III / Q000378:metabolism; D005109:Extracellular Matrix / Q000201:enzymology / Q000378:metabolism*; D005260:Female; D018093:Gelatinases / Q000378:metabolism; D006325:Heart Atria / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008875:Middle Aged; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III; D019714:Tissue Inhibitor of Metalloproteinases; D018093:Gelatinases; D020782:Matrix Metalloproteinases