Primary Human Cardiac Myocytes (HCM) are isolated from the ventricles of the adult heart. Unlike freshly isolated rod-shaped myocytes, cultured HCM can be used for long-term experiments like investigating the long-term effects of cytokines, mechanical strain, or cell-cell interactions, as they are prepared according to a special protocol.Initially, the HCM act more like progenitor cells in that they are not yet fully differentiated. They express the markers of early stage differentiation such as GATA-4 and sarcomeric alpha-actin and have a high capacity for proliferation. When they are grown to confluency and cultivated for an extended period of time, the differentiation process begins. Markers of late differentiation (e.g. sarcomeric alpha-actinin, slow muscle myosin) are increased and the cells begin to form myotube-like structures.Our HCM are now also available from HLA-typed and Diabetes Diabetes Type I and Type II/Cardiomypathy donors.