MicroRNA expression profiling of zebrafish heart regeneration. Danio rerio

Cardiovascular disease is the leading cause of morbidity and mortality in the Western world due to a limited regenerative capacity. In lieu of new muscle synthesis, the human heart replaces necrotic tissue with deposition of a non-contractile scar. In contrast, the adult zebrafish is endowed with a remarkable regenerative capacity, capable of de novo cardiomyocyte (CM) creation and scar tissue resolution when challenged with an acute injury. In these studies, we examined the contributions of the dynamically regulated microRNA, miR-101a, during adult zebrafish heart regeneration. We demonstrate that miR-101a expression is rapidly depleted within 3 days post-amputation (dpa) but is highly upregulated by 7-14 dpa, before returning to uninjured levels at the completion of the regenerative process. Employing heat-inducible transgenic strains and antisense oligonucleotides, we demonstrate that decreases in miR-101a levels at the onset of cardiac injury enhanced CM proliferation. Interestingly, prolonged suppression of miR-101a activity stimulates new muscle synthesis but with defects in scar tissue resolution. Upregulation of miR-101a expression between 7-14 dpa is critical to stimulate remodeling of the scar. Through a series of studies, we identified the proto-oncogene, fosab (cfos) as a potent miR-101a target gene, stimulator of CM proliferation, and inhibitor of scar tissue remodeling. Importantly, combinatorial depletion of fosab and miR-101a activity rescued defects in scar tissue resolution mediated by miR-101a inhibition alone. In summation, our studies indicate that the precise temporal modulation in the miR-101a/fosab genetic axis is critical for coordinating CM proliferation and scar tissue resolution during zebrafish heart regeneration. Overall design: Pooled cardiac samples from uninjured and regenerating (6hpa) adult fish in biological triplicate.