Expression of VEGF in atrial myocardium from patients with sinus rhythm (SR) and atrial fibrillation (AF).

<p>A, B: Atrial samples from patients with SR. (A) A strong immunoreactivity for VEGF is localized to the capillaries, while cardiomyocytes display rather low level of VEGF expression. (B) High level of VEGF immunoreactivity in mesothelial cells and in adipocytes of epicardium. C, D: Atrial samples from patients with AF. (C) A strong immunoreactivity for VEGF is localized to mesothelium. There are VEGF-positive capillaries and moderately positive cardiomyocytes in the atrial myocardium. (D) A strong VEGF immunoreactivity in the myocardium (mainly cardiomyocytes) and in mesothelial cells. Scale bar in A-D = 50μm. (E) A graph showing a result of semiquantitative analysis of VEGF immunoreactivity in the atrial samples from all patients as described in Methods (score 0–3). A comparison between different structures from different anatomical locations is shown: RA–right appendage, LA–left appendage, LAt–left atrium.</p

Collagen III in the atrial myocardium.

<p>A-D: Immunohistochemical reaction shows collagen III in endomysial and partly also perimysial extracellular matrix. In atria of both patient groups (SR in A, B and AF in C, D) it is possible to detect higher (A, C) as well as lower (B, D) amount of collagen III-positive ECM. Immunoperoxidase reaction with DAB as a substrate (brown precipitate). No nuclear counterstaining. For all images scale bar = 50μm. (E) A graph showing the result of quantification of collagen III volume fraction (CIIIVF) in atrial myocardial samples. A comparison between different anatomical locations is shown: right appendage–RA (n = 37), left appendage–LA (n = 19), left atrium—LAt (n = 9), LA+LAt (n = 28).</p

Microvessel pericyte coverage in atria of patients with sinus rhythm (SR) and atrial fibrillation (AF).

<p>(A-D) Confocal images of human atria. (A) Immunodetection of desmin (green) shows its expression in cardiomyocytes. Capillaries labeled with UEA-lectin (red) are devoid of desmin immunoreactivity (arrowheads). Scale bar = 50μm. (B) Desmin is present in cardiomyocytes, while SMA-positive capillary pericyte (arrowhead) does not display desmin signal. Scale bar = 10μm. (C) A representative section of myocardium used for the quantitative analysis of microvessel pericyte coverage index. Blood vessel endothelium is labeled using UEA lectin (red) and pericytes are visualized using anti-SMA antibody (green). Scale bar = 100μm. (D) A high magnification image shows SMA-positive smooth muscle cells surrounding a small arteriole and also SMA-positive pericytes in association with the capillaries (arrowheads). Scale bar = 25μm. (A, B, D) Nuclei are stained with DAPI (blue). (E) A graph showing results of quantification of microvessel pericyte coverage index (MPI) in atrial samples of all patients as described in Methods. RA–right appendage (n = 8), LA–left appendage (n = 9), LAt–left atrium (n = 7), LA + LAt (n = 16).</p

Analysis of immune cell populations in atrial myocardium of patients with atrial fibrillation or sinus rhythm

<div><p>Background</p><p>Atrial fibrillation (AF) is the most common arrhythmia and despite obvious clinical importance remains its pathogenesis only partially explained. A relation between inflammation and AF has been suggested by findings of increased inflammatory markers in AF patients.</p><p>Objective</p><p>The goal of this study was to characterize morphologically and functionally CD45-positive inflammatory cell populations in atrial myocardium of patients with AF as compared to sinus rhythm (SR).</p><p>Methods</p><p>We examined 46 subjects (19 with AF, and 27 in SR) undergoing coronary bypass or valve surgery. Peroperative bioptic samples of the left and the right atrial tissue were examined using immunohistochemistry.</p><p>Results</p><p>The number of CD3+ T-lymphocytes and CD68-KP1+ cells were elevated in the left atrial myocardium of patients with AF compared to those in SR. Immune cell infiltration of LA was related to the rhythm, but not to age, body size, LA size, mitral regurgitation grade, type of surgery, systemic markers of inflammation or presence of diabetes or hypertension. Most of CD68-KP1+ cells corresponded to dendritic cell population based on their morphology and immunoreactivity for DC-SIGN. The numbers of mast cells and CD20+ B-lymphocytes did not differ between AF and SR patients. No foci of inflammation were detected in any sample.</p><p>Conclusions</p><p>An immunohistochemical analysis of samples from patients undergoing open heart surgery showed moderate and site-specific increase of inflammatory cells in the atrial myocardium of patients with AF compared to those in SR, with prevailing population of monocyte-macrophage lineage. These cells and their cytokine products may play a role in atrial remodeling and AF persistence.</p></div

CD3-positive T-lymphocytes and CD68-KP1-positive cells in the atrial myocardium.

<p>Sections of atrial myocardium from patients with atrial fibrillation showing a result of immunoperoxidase reaction for CD3 and CD68-KP1. A) CD3-positive T-lymphocytes localized among atrial cardiomyocytes and in the interstitial spaces (arrowheads). Scale bar = 50 μm. B) CD68-KP1-positive cells are found in the interstitium and have mainly elongated morphology (arrowheads). Scale bar = 50 μm. C) Frequency of CD3-positive T-lymphocytes in the atrial myocardium of patients with atrial fibrillation (AF) and sinus rhythm (SR). An average number of CD3-positive T-lymphocytes cells per square mm of cross-sectioned atrial myocardium is given +- SD. Right appendage–SR (n = 17), AF (n = 11); Left appendage—SR (n = 8), AF (n = 10); Left atrial free wall + left appendage—SR (n = 9), AF (n = 16). *—p<0,05 D) Frequency of CD68-KP1-positive cells in the atrial myocardium of patients with atrial fibrillation (AF) and sinus rhythm (SR). An average number of CD68-KP1-positive cells per square mm of cross-sectioned atrial myocardium is given +- SD. Right appendage–SR (n = 22), AF (n = 9); Left appendage—SR (n = 11), AF (n = 9); Left atrial free wall + left appendage—SR (n = 13), AF (n = 19). *—p<0,05</p

CD45-positive cells in the atrial myocardium.

<p>Sections of atrial wall from patients with sinus rhythm (A, B, D) and atrial fibrillation (C) showing a result of immunoperoxidase reaction for CD45. A) Epicardial and myocardial layer of atrial wall contains scattered as well as clustered (arrowhead) CD45-positive cells. Scale bar = 100μm. B) Endocardial layer with CD45-positive cells (arrowhead) next to the atrial lumen (L). Scale bar = 20μm. C) A section through the trabecular part of the atrial wall with CD45-positive cells in the myocardium (M) and endocardium (E). Scale bar = 50 μm. D) A detailed view on the atrial myocardium with CD45-positive cells having rather rounded (arrowhead) or elongated (arrow) cell shape. Scale bar 50 = μm. E) Frequency of CD45+ cells in the atrial myocardium of patients with atrial fibrillation (AF) and sinus rhythm (SR). An average number of CD45+ cells per square mm of cross-sectioned atrial myocardium is given +- SD. Right appendage–SR (n = 22), AF (n = 15); Left appendage—SR (n = 8), AF (n = 8); Left atrial free wall—SR (n = 4), AF (n = 8); Left atrial free wall + left appendage—SR (n = 12), AF (n = 16).</p