Sex-specific dysregulation of cardiac-enriched microRNAs with age in <i>Drosophila melanogaster</i>

Dysregulation of cardiac-enriched microRNA (miRNA) expression is linked to age-associated cardiovascular diseases (CVDs). However, the sex-specificity and age at which dysregulation occurs remain unclear. Given the conserved nature of miRNAs and short lifespan of <i>Drosophila melanogaster</i> (fruit flies), we investigated age-related changes in the expression of cardiac enriched miRNAs (miR-1, -9, -34a, and -133, target miRNAs) and their impact on the cardiac tube in male and female flies. Cardiac tube tissues were collected from male and female flies (<i>n</i> = 5/group) at 7-day intervals from <i>day 7</i> to <i>day 70</i>. miRNAs and predicted target mRNA gene (<i>KCNQ</i>, <i>MRTF</i>, and <i>CCN</i>) expression were quantified by RT-qPCR (<i>n</i> = 4-6/group). Myofibril diameter was assessed by Masson's trichrome staining (<i>n</i> = 4-6) to determine the structural effects of hypertrophic miR-9. In females, miR-1 was downregulated with age (<i>P</i> ≤ 0.0001), whereas in males, miR-9 (<i>P</i> ≤ 0.0001) and miR-34a (<i>P</i> = 0.0017) were downregulated. Interestingly, miR-133 was downregulated in both sexes (<i>P</i> ≤ 0.0001). In males, <i>MRTF</i> (miR-9 target) and <i>CCN</i> (miR-133 target) expression increased with age (<i>P</i> = 0.016 and <i>P</i> = 0.013, respectively), whereas in females, <i>KCNQ</i> (miR-1 target) and <i>CCN</i> expression decreased (<i>P</i> = 0.03 and <i>P</i> = 0.002, respectively). Myofibril thickness significantly increased with age in both sexes (<i>P</i> < 0.0001). miR-9 downregulation may contribute to this effect in males, whereas the mechanism in females remains unclear. This study provides novel insights into sex-specific miRNA dysregulation in cardiac aging, emphasizing the need to consider sex differences in miRNA-mediated cardiovascular aging and the potential of miRNAs as diagnostic tools in age-related CVDs.<b>NEW & NOTEWORTHY</b> Advancements in healthcare and diet have increased life expectancy, doubling the population aged 60 and above by 2050. However, this longevity raises the risk of chronic diseases, especially cardiovascular diseases. We examined age-related changes in cardiovascular-enriched microRNAs in the <i>Drosophila melanogaster</i> heart. This first-of-its-kind observational study tracks microRNA changes across life stages. It highlights sex-specific expression of miRNAs, providing crucial insights into cardiac aging. It lays a strong foundation for future research on microRNA in heart health.