Extracellular and Intracellular microRNA Gene Regulatory Networks in Cardiovascular Disease

Abstract

Epidemiological studies have demonstrated an inverse correlation between high-density lipoproteins (HDL) cholesterol and cardiovascular disease (CVD) risk; however therapeutic approaches aimed at raising HDL cholesterol have not alleviated cardiovascular events. Furthermore, chronic kidney disease patients have an increased risk of developing CVD, and dysfunctional HDL and endothelium may contribute to this increased risk. Interestingly, plasma HDL stably transports miRNAs, which are small non-coding RNAs that post-transcriptionally regulate gene expression. Furthermore, the HDL-miRNAs are transferred to endothelial cells in vitro where they regulate gene expression. A novel cell-to-cell communication network of HDL-miRNAs may confer the alternative functions of HDL and provide protection from disease; however, the HDL-miRNA cell-to-cell communication network has not been demonstrated in vivo. To evaluate this novel network in vivo, bone marrow transplants between wild-type (WT) and miR-223 knockout (Mir223-/-) mice were utilized since miR-223 is a myeloid specific miRNA that is highly abundant on HDL. Transplantation of Mir223-/- bone marrow into WT mice depleted miR-223-3p levels on HDL and in aortic endothelium. Conversely, the reciprocal transplant restored HDL and endothelial cell miR-223-3p levels. Ultimately, restoring endothelial miR-223-3p levels resulted in altered gene expression not observed in blood cell isolates. Better understanding of this HDL-miRNA cell-to-cell communication network contributes to development of RNA based therapeutic delivery to aortic endothelial cells. To evaluate the therapeutic potential, HDL was used to deliver miRNA inhibitors to aortic endothelium in apolipoprotein E deficient (Apoe-/-) mice with impaired renal damage (5/6 nephrectomy, 5/6Nx). Endothelial miR-92a-3p and miR-489-3p were elevated with renal damage and delivery of inhibitors by HDL significantly reduced both miRNAs. Furthermore, dual miRNA inhibition significantly reduced atherosclerosis burden by 28% and significantly altered endothelial gene expression. Putative target genes involved in TGF-beta and STAT3 pathways were identified to be dysregulated in disease and restored with miRNA inhibition. This work demonstrates a novel HDL-miRNA cell-to-cell communication network in vivo, which can be used as a therapeutic treatment to influence disease physiology.