GREM1 and hydrops fetalis: This study aimed to detect and document the significant expression changes of OPN and Grem1 proteins in cardiomyocytes at different stages of ischemic HF, including stage A (at-risk for HF), stage B (pre-HF), and stages C/D HF (symptomatic and advanced HF) according to the American College of Cardiology (ACC)/American Heart Association (AHA) classification [29], by applying validated semi-quantitative immunohistochemical evaluation.