We investigate for the first time the influence of heart failure (HF) on nucleolar organization and proteins in patients with ischemic (ICM) or dilated cardiomyopathy (DCM). A total of 71 human hearts from ICM (n = 38) and DCM (n = 27) patients, undergoing heart transplantation and control donors (n = 6), were analysed by western-blotting, RT-PCR and cell biology methods. When we compared protein levels according to HF etiology, nucleolin was increased in both ICM (117%, p < 0.05) and DCM (141%, p < 0.01). Moreover, mRNA expression were also upregulated in ICM (1.46-fold, p < 0.05) and DCM (1.70-fold, p < 0.05. Immunofluorescence studies showed that the highest intensity of nucleolin was into nucleolus (p < 0.0001), and it was increased in pathological hearts (p < 0.0001). Ultrastructure analysis by electron microscopy showed an increase in the nucleus and nucleolus size in ICM (17%, p < 0.05 and 131%, p < 0.001) and DCM (56%, p < 0.01 and 69%, p < 0.01). Nucleolar organization was influenced by HF irrespective of etiology, increasing fibrillar centers (p < 0.001), perinucleolar chromatin (p < 0.01) and dense fibrillar components (p < 0.01). Finally, left ventricular function parameters were related with nucleolin levels in ischemic hearts (p < 0.0001). The present study demonstrates that HF influences on morphology and organization of nucleolar components, revealing changes in the expression and in the levels of nudeolin protein. (C) 2012 Elsevier Inc. All rights reserved.