| Because microRNAs have recently been involved in cardiac disease, we analyzed microRNA (miRNA) expression profiles of failing human ischemic hearts and uncovered several differentially expressed miRNAs, with miRNA-216a (miR-216a) being strongly increased in expression. Interestingly, predictive algorithms identified many cell-death-related genes as potential direct target genes of miR-216a, one of them being Beclin-1 (Becn1), an autophagy-regulating gene. Because cardiomyocyte demise due to apoptosis and autophagy is a major cellular event in heart failure, this proposal focuses not only on miR-216a and its role in cell death during myocardial repair, but also on identifying other miRNAs that are involved in regulating autophagy in cardiomyocytes. We hypothesize 1) that post-transcriptional mechanisms regulate cell viability by autophagy and 2) that changes in miR-216a expression directly influences cardiac autophagy and remodeling The key objectives are: 1) Identify genes that are directly regulated by miR-216a and 2) define the role of miR-216a regulating cell death in ischemic heart disease; 3) Establish the therapeutic value of miR-216 silencing in cardiac disease and 4) identify other autophagy-regulating miRNAs by high-throughput screening. For objective 1, we will take a bioinformatics approach by combining large-scale proteomics and microarray analyses on genetic and pharmacological models of miR-216a silencing. In objective 2 we will modulate miR-216a expression in vitro and in vivo and expect miR-216a expression levels to directly reflect the degree of cardiac remodeling, by directly affecting autophagy. For objective 3, we will use a pharmacological approach to silence miR-216a in the setting of ischemic heart disease and anticipate subsequent attenuation of post-MI remodeling, revealing a new potential therapeutic strategy in human cardiac disease. For objective 4, we will establish a high content screening (HCS) assay to identify all miRNAs that functionally regulate autophagy in cardiomyocytes in response to cell stresses inducing/inhibiting autophagy and pathological cardiac remodeling. |
