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Abstract
Vascular remodeling resulting from the smooth muscle cell (SMC) phenotypic switching from a quiescent state to a proliferative state is a crucial pathological process following vascular injury, which often occurs after percutaneous coronary intervention, cardiac transplantation, and bypass surgery. Therefore, identifying novel targets that regulate SMC phenotypic modulation and vascular remodeling is pivotal for developing new therapeutic strategies. Recently, circular RNA (circRNA), a novel type of non-coding RNA with closed-loop structure, has been discovered, displaying high stability and cell- and disease-specific expression patterns. The objective of this study is to determine the role and mechanism of circular Superoxide Dismutase 2 (circSOD2) and circular Cysteine-Rich Motor neuron 1 (circCRIM1) in SMC phenotypic modulation and vascular remodeling.Using next-generation sequencing (NGS), we have identified circSOD2 and circCRIM1 as our targets highly expressed in platelet-derived growth factor-BB (PDGF-BB)-induced SMC. Blockade or forced expression of circSOD2 suppresses and promotes SMC proliferation, respectively. Mechanistically, in SMC, circSOD2 can act as a micro RNA 206 (miR-206) sponge which is an upstream inhibitory factor of NOTCH3 and consequently boosts phosphorylation of extracellular signal‑regulated protein kinase 1/2 (ERK1/2), leading to the increase of SMC G1-to-S cell cycle transition and eventually promotes SMC proliferation. In vivo, suppression of circSOD2 decreases injury-induced neointimal formation, indicating targeting circSOD2/miR-206/NOTCH3 axis may be a promising strategy to hinder injury-induced vascular remodeling in proliferative vascular diseases.
We also demonstrate for the first time that circCRIM1 is involved in SMC phenotypic modulation and has the capability of continuous loop-translation encoding a protein. Knockdown or overexpression of circCRIM1 restores and further suppresses PGDF-BB induced downregulation of SMC marker genes, respectively. Mechanistically, circCRIM1 can bind with miR-16 to modulate SMC phenotypic modulation. Using liquid chromatography-mass spectrometry (LC/MS), we have identified circCRIM1 encoded protein. Furthermore, circCRIM1 translation is found to be driven by N6-Methyladenosine (m6A) modification and recognized explicitly by YTH domain-containing family protein 3 (YTHDF3). Our results suggest that circCRIM1 is a novel regulator for SMC phenotypic modulation with continuous loop translation ability.