SPP1 and dilated cardiomyopathy: Immunohistochemical analysis of myocardial biopsies obtained from patients with heart failure due to dilated cardiomyopathy demonstrated increased OPN expression in cardiac myocytes, which correlated positively with impaired left ventricle (LV) function (Stawowy et al., 2002), and collagen type I levels (Satoh et al., 2005).