C1QTNF9 and myocardial infarction: The aims of this study were (1) to determine the role of cardiac-derived CTRP9 in MI/R injury; (2) to investigate whether cardiac-derived CTRP9 regulates myocardial dysfunction after MI/R in an autocrine or paracrine manner; (3) to elucidate the underlying mechanisms responsible for the actions of cardiac-derived CTRP9 upon MI/R injury.