Abstract 1989: Regulation of Compensatory Angiogenesis During Cardiac Hypertrophy by a p300 - miR-17392 Feedback Loop
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 6 –9 months of age. Hypothesis: p300 drives the transition of hypertrophy to heart failure by regulating an angiogenic transcriptional program, which includes major angiogenic genes, transcription factors, and microRNAs.
Results: p300-driven hypertrophy was initially accompanied by robust angiogenic gene expression and blood vessel growth. Onset of heart failure was preceded by a steep fall in angiogenic transcripts and a rise in miR-17~92 transcripts. Consistently, in vivo, all members of the miR-17~92 cluster were upregulated in cardiac myocytes over-expressing p300. p300 bound directly to a regulatory sequence within the miR17~92 cluster in vivo, in inverse proportion to HDAC9 binding. MiR-20a suppressed both p300 (FC=0.05; p=0.001) and HIF-1A (FC=0.03; p=0.05) transcripts, and blocked vasculogenic differentiation of cardiac stem cells. MiR-20a reduced HIF-1A protein level in CSCs in the cytosol (in air) and in the nucleus (in 2 hour hypoxia). MiR-20a significantly (p<.01) decreased proliferation of CSCs relative to untransduced CSCs and CSCs with the scrambled miR, without affecting cell viablility. Cell cycle analysis showed that miR-20a significantly reduced the progression of CSCs through the cell cycle. Both cardiomyocytes and cardiac stem cells over-expressing miR-20a had reduced F-actin content and sarcomere organization, consistent with p300 loss, while loss of miR-20a changed CSC morphology by inducing cellular projections, a vasculogenic gene profile and increased vasculogenesis in both matrigel assay and co-culture with cardiomyocytes.
Conclusion: We propose that both angiogenic genes and anti-angiogenic miRs are transcription targets of p300. The p300 target miR-20a negatively regulates proliferation and angiogenic potential of CSCs, and induction of miR-20a is part of a negative feedback loop that suppresses p300 and secondarily blunts compensatory angiogenesis, leading to heart failure.
This research has received full or partial funding support from the American Heart Association, National Center.