Abstract 13758: A MicroRNA-20a - p300 Circuit in Cardiac Myocytes and Cardiac Stem Cells Regulates Compensatory Angiogenesis during Cardiac Hypertrophy
Background: Failure of compensatory angiogenesis may contribute to decompensation of cardiac hypertrophy. We previously showed that a myocyte-restricted p300 transgene drives adaptive cardiac hypertrophy that leads to heart failure between 7–9 months of age.
Hypothesis: p300 drives the transition of hypertrophy to heart failure by regulating an angiogenic transcriptional program in cardiac myocytes and cardiac stem cells (CSCs), which includes major angiogenic genes, transcription factors, and microRNAs.
Results: Here we show that the adaptive phase of p300-driven hypertrophy is accompanied by robust angiogenic gene expression and blood vessel growth. However, a steep fall in angiogenic transcripts occurs after 5 months together with a corresponding rise in expression of members of the miR-17∼92 cluster, two of which (miR-17–3p and miR-20a) have predicted target sites in the 3′UTRs of HIF1A, VEGFA as well as in p300 itself. In p300tg myocardium in vivo, p300 bound to a novel enhancer directly upstream of miR-20a, displacing HDAC9. Lentiviral-mediated overexpression of miR-20a suppressed (p<.05) basal and hypoxia-induced HIF-1A, VEGFA, a-actinin and p300 mRNA and protein levels in CSCs, and reduced F-actin content and cytoskeletal organization in both cardiac myocytes and CSCs, consistent with p300 loss. CSCs overexpressing miR-20a expressed reduced levels of 28 angiogenic genes, nearly identical to the levels in p300tg myocardium at 9 months, with significantly (p<.01) reduced proliferation rates and tube forming potential in Matrigel. Conversely, CSCs with miR-20a knockdown had enhanced angiogenic gene expression, more efficient tube formation, and increased endothelial differentiation in co-culture with cardiomyocytes as measured by significant (p<.01) induction of vWF and lumen formation. In vivo, lentiviral-mediated induction of miR-20a delayed reperfusion in hind limb ischemia at 1, 2 and 3wks relative to a scrambled miR or VEGFA controls.
Conclusion: These findings indicate that p300 induces angiogenic genes and anti-angiogenic microRNAs, including miR-20a, as part of a circuit that reduces p300 levels during hypertrophy and secondarily blunts compensatory angiogenesis in cardiac myocytes and CSCs leading to heart failure.
- © 2010 by American Heart Association, Inc.