Data from Previous Award Period: To test the hypothesis that adverse remodeling does not occur in children with DCM, we obtained LV myocardial specimens from the apex and lateral wall of non-failing pediatric donor controls (n=11), pediatric DCM patients (n=31), adult non-failing donor controls (n=14), and adult DCM (n=34) patients. To our knowledge, this represents the largest collection of pediatric and adult DCM tissue specimens studied to date. Control tissue was obtained from unused donors with normal cardiac function by echocardiography. DCM specimens were obtained from children and adults with advanced stage idiopathic or familial DCN at the time of cardiac transplantation or implantation of a left ventricular assist device. To evaluate the presence and extent of adverse remodeling at the tissue level, we measured cardiomyocyte and sarcomere size, myocardial fibrosis, and capillary density in pediatric and adult donor control and DCM specimens. In addition, we performed RNA sequencing on pediatric and adult DCM specimens to examine gene expression signatures of adverse remodeling and define pathways that differentiate pediatric from adult DCM. Control and DCM specimens were obtained in collaboration with the Translational Cardiovascular Biobank and Repository at Washington University, University of Colorado, and the Pediatric Cardiomyopathy Registry (PCMR) tissue repository.