Smooth Muscle Cell MicroRNA‐9 is Transcriptionally Regulated by MicroRNA‐25 in Vascular Disease
Authors: Conti Amanda L , Schickling Brandon M , Miller Francis 
Published: June 2021

Cardiovascular disease (CVD) remains the leading cause of mortality in the United States despite significant research efforts to understand mechanisms of disease and to develop new therapies. Recently, microRNAs (miRs) have been implicated as important regulators of cardiovascular pathologies. These small, non‐coding, RNA molecules act as post‐transcriptional regulators of gene expression. While miR‐9 and miR‐25 have been implicated in several cancer phenotypes, their role in vascular disease is unclear. The goal of this study was to evaluate the relationship between miR‐9 and miR‐25 in vascular disease. The upregulation of miR‐9 and miR‐25 was observed in several model systems of CVD. Vascular smooth muscle cells (VSMC) isolated from the aortae of monkeys administered an atherogenic diet showed a 9‐fold increase in miR‐9 expression and a 5‐fold increase in miR‐25 expression as compared to VSMC isolated from animals on a normal diet. Further, miR‐9 expression was increased in the mouse carotid artery one week after vessel ligation, representing a model of vascular remodeling and neointima formation. In addition, VSMC derived from the intimal layer of rat aorta after balloon injury demonstrated increased levels of miR‐9 and miR‐25 as compared to medial‐derived cells. Finally, the treatment of human VSMCs with proinflammatory cytokines or growth factors significantly increased miR‐9 and miR‐25 levels. These data provide complementary evidence that expression of miR‐9 and miR‐25 are increased in VSMC during vascular disease. We next determined the relationship between the expression of these miRNAs. Exposure of human VSMC or explanted pulmonary artery segments to a miR‐25 mimic induced greater than 100‐fold increase in the expression of miR‐9. This interaction was unidirectional and specific, as miR‐25 did not increase other cardiovascular‐associated miRs such as miR‐21 and miR‐126. Epigenetic analysis showed that a miR‐25 mimic caused decreased methylation of the miR‐9 promoter in VSMC, suggesting miR‐9 transcriptional activation. Additionally, miR‐25 was observed to increase activation of NF‐κB, a versatile signaling molecule involved in inflammation and stress responses in vascular disease. Analysis of the miR‐9 promoter has identified specific regions necessary for miR‐25 dependent activation of miR‐9 expression, including NF‐κB binding sites. Taken together, these results suggest that miR‐25 induces miR‐9 expression in vascular disease as part of a network involving the NF‐κB pathway. In conclusion, the more nuanced understanding of the microRNA pathways involved in cardiovascular disease informs the development of potential therapeutic strategies.Support or Funding InformationFJM is supported by the Office of Research and Development, Department of Veterans Affairs [2I01BX001729] and the National Institutes of Health [HL130039]. BMS is supported by the National Institutes of Health [T32HL007101] and the American Heart Association [PRE29980013].This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.