Takeshi Kato1, Akiko Sekiguchi2, Koichi Sagara2, Hiroaki Tanabe2, Masayuki Takamura3, Shuichi Kaneko2, Tadanori Aizawa2, Long-Tai Fu2, Takeshi Yamashita2. 1. Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan; The Cardiovascular Institute, Tokyo, Japan. Electronic address: takeshikato@me.com. 2. The Cardiovascular Institute, Tokyo, Japan. 3. Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan.
Abstract
BACKGROUND: Atrial fibrosis is a hallmark of atrial structural remodeling leading to the persistence of atrial fibrillation. Although fibroblasts play a major role in atrial fibrosis, their source in the adult atrium is unclear. We tested the hypothesis that endothelial cells contribute to fibroblast accumulation through an endothelial-mesenchymal transition in the atrium of patients with atrial fibrillation. METHODS AND RESULTS: The study group consisted of patients with atrial fibrillation and valvular disease or atrial septal defect who underwent left atrial appendectomy during cardiac surgery (n=38). The amount of fibrotic depositions in the left atrium positively correlated with left atrial dimension. Furthermore, snail and S100A4, indicative of endothelial-mesenchymal transition, were quantified in the left atrium using western blot analysis, which showed statistically significant correlations with left atrial dimension. Immunofluorescence assay of the left atrial tissue identified snail and S100A4 being expressed within the endocardium which is composed of CD31+ cells. The snail-positive endocardium also showed the expression of membrane type 1-matrix metalloproteinase. Immunofluorescence multi-labeling experiments identified that heat shock protein 47, prolyl-4-hydroxylase, and procollagen type 1 co-localized with snail and S100A4 within the endothelial cells of the left atrium, indicating the mesenchymal phenotype to produce collagen. CONCLUSIONS: In this study, we showed that the endothelial-mesenchymal transition occurs in the atrium of patients with atrial fibrillation. This observation should help in constructing a novel therapeutic approach for preventing atrial structural remodeling.
BACKGROUND:Atrial fibrosis is a hallmark of atrial structural remodeling leading to the persistence of atrial fibrillation. Although fibroblasts play a major role in atrial fibrosis, their source in the adult atrium is unclear. We tested the hypothesis that endothelial cells contribute to fibroblast accumulation through an endothelial-mesenchymal transition in the atrium of patients with atrial fibrillation. METHODS AND RESULTS: The study group consisted of patients with atrial fibrillation and valvular disease or atrial septal defect who underwent left atrial appendectomy during cardiac surgery (n=38). The amount of fibrotic depositions in the left atrium positively correlated with left atrial dimension. Furthermore, snail and S100A4, indicative of endothelial-mesenchymal transition, were quantified in the left atrium using western blot analysis, which showed statistically significant correlations with left atrial dimension. Immunofluorescence assay of the left atrial tissue identified snail and S100A4 being expressed within the endocardium which is composed of CD31+ cells. The snail-positive endocardium also showed the expression of membrane type 1-matrix metalloproteinase. Immunofluorescence multi-labeling experiments identified that heat shock protein 47, prolyl-4-hydroxylase, and procollagen type 1 co-localized with snail and S100A4 within the endothelial cells of the left atrium, indicating the mesenchymal phenotype to produce collagen. CONCLUSIONS: In this study, we showed that the endothelial-mesenchymal transition occurs in the atrium of patients with atrial fibrillation. This observation should help in constructing a novel therapeutic approach for preventing atrial structural remodeling.
Authors: Maria Laggner; Philipp Hacker; Felicitas Oberndorfer; Jonas Bauer; Thomas Raunegger; Christian Gerges; Tamás Szerafin; Jürgen Thanner; Irene Lang; Nika Skoro-Sajer; Hendrik Jan Ankersmit; Bernhard Moser Journal: Biology (Basel) Date: 2022-01-12