Collagen volume fraction, CTGF and TGF-beta expression in patients with end-stage heart failure and atrial fibrillation

Atrial fibrillation is a common disorder and its relation to myocardial fibrosis is currently under investigation. The aim of our study was to evaluate the level of fibrosis manifested as collagen volume fraction (CVF), together with the immunohistochemical detection of transforming growth factor-beta (TGF-beta) and connective tissue growth factor (CTGF) in patients suffering from end stage heart failure with or without atrial fibrillation. TGF-beta and CTGF are involved in fibrotic processes in various organs and their role in myocardial fibrosis has been proposed, as well. The study was performed in two groups of patients - one group with atrial fibrillation and one group with sinus rhythm. In both of these groups were patients indicated for heart transplantation, who were diagnosed with ischemic heart disease or cardiomyopathy. The atrial and the ventricular samples were fixed with paraformaldehyde and embedded into paraffin. Histochemical detection of collagen for quantification of collagen volume fraction (CVF) was performed using Sirius red staining. Immunohistochemical detection of TGF-beta and CTGF was performed using three-step immunoperoxidase reaction. Image analysis software was used for the quantitation of CVF and immunohistochemical reaction product. When the CVF was quantified in the right atrial myocardium and in the left ventricular myocardium, there was nosignificant difference in CVF between the atrial fibrillation and the sinus rhythm group. CTGF was detected in all samples obtained from both groups of patients. It was constantly expressed in cardiomyo-cytes. TGF-beta was also detected in all samples. However, its expression in atria was not as widespread as that of CTGF. TGF-beta was found mainly in the endothelial lining of atria and in the capillary endothelium. Cardiomyocytes expressed TGF-beta in some of the samples; mainly in regions adjacent to endocardium. TGF-beta was more abundant in ventricles than in atria. In summary, we found that in patients with end stage heart failure there was no difference in CVF between groups of patients with atrial fibrillation and with sinus rhythm. In addition, we detected both CTGF and TGF-beta in atria and ventricles of patients from these two groups.

Supported by MSMT Grant No. 0021620807.