Induction of Let-7d-5p miRNA modulates aortic smooth muscle inflammatory signaling and phenotypic switching.

Background and aims Activation of vascular smooth muscle cell inflammation is recognised as an important early driver of vascular disease. We have previously identified the let-7 miRNA family as important regulators of inflammation in in vitro and in vivo models of atherosclerosis. Here we investigated a dual statin/let-7d-5p miRNA combination therapy approach to target human aortic SMC (HAoSMC) activation and inflammation. Methods In vitro studies using primary HAoSMCs were performed to investigate the effects of let-7d-5p miRNA overexpression and inhibition. HAoSMCs were treated with combinations of the inflammatory cytokine tumor necrosis factor-α (TNF-α), and atorvastatin or lovastatin. HAoSMC Bulk RNA-seq transcriptomics of HAoSMCs revealed downstream regulatory networks modulated by let-7d-5p miRNA overexpression and statins. Proteome profiler cytokine array, western blotting and quantitative PCR analyses were performed on HAoSMCs to validate key findings. Results Let-7d-5p overexpression significantly attenuated TNF-α-induced upregulation of IL-6, ICAM-1, VCAM-1, CCL2, CD68, MYOCD gene expression in HAoSMCs (p<0.05). Statins (atorvastatin, lovastatin) significantly attenuated inflammatory gene expression and upregulated Let-7d levels in HAoSMCs (p<0.05). Bulk RNA-seq analysis of a dual Let-7d-5p overexpression/statin therapy in HAoSMCs revealed that let-7d-5p activation and statins converge on key inflammatory pathways (IL-6, IL-1β, TNF-α, IFN-γ). Let-7d-5p overexpression led to reduced expression of the ox-LDL receptor OLR1, and this was associated with lower ox-LDL uptake in HAoSMCs. In silico analysis of smooth muscle cell phenotypic switching shows that overexpression of let-7d-5p in HAoSMCs maintains a contractile phenotype. Conclusions Targeting the Let-7 network alongside statins can modulate HAoSMC activation and attenuate key inflammatory pathway signals.