A study in humans demonstrated that pericardial fluid from ST-segment elevation myocardial infarction patients is enriched in pro-fibrotic and anti-fibrotic microRNAs, including the miR-450a-2-3p which was identified in exosomes from pericardial fluid of atrial fibrillation patients and reported to drive cardiac fibrosis [Silva et al. DOI:10.3390/ijms25158329].