Abstract MP13: Small RNA Profiling Identifies Mir-200b As A Repressor Of Vascular Smooth Muscle Cell Migration And Proliferation

Abstract

Background and Objectives: A large body of research has identified miRNA as pivotal regulators of smooth muscle cell (SMC) fate in various vascular diseases. However, global changes of miRNA expression profile during SMC phenotypic modulation have not been well characterized. As the targetome of a given miRNA is highly dependent on the cell type and context, comparative analysis of mRNA and miRNA expression profiles can provide decisive information for assessing the versatility in miRNA functions and discovering novel miRNA modulating SMC phenotype. Our goal is to define the miRNA signatures in differentiated and de-differentiated SMC, the miRNA overall contribution to the transcriptome, and novel functionally relevant miRNA. Methods: By performing RNAseq and small RNAseq, we defined the mRNA/miRNA expression profiles in aortic SMC cultured in differentiation or de-differentiation media with Platelet Derived Growth Factor-BB (PDGF-BB) and performed functional studies on differentially expressed miRNAs (DEmiR). Results: We found that PDGF-BB-induced SMC de-differentiation generated 48 significant DEmiRs, including 15 downregulated and 33 upregulated DEmiRs. Integrative analysis predicted that nearly 40% (1335 of 3523) of differentially expressed transcripts were direct targets of DEmiRs. The miR-200 cluster (miR-200a, miR-200b and miR-429) was found potently downregulated after PDGF-BB treatment, as well as Tet2 and Myocardin knockdown, while its expression increased in rapamycin treated SMC. We found that miR-200b overexpression prevented PDGF-BB-induced SMC migration and proliferation, while miR-200b inhibition had an opposite effect. Finally, we identified Quaking, a potent inducer of SMC phenotypic switching, as a primary target of miR-200b. Conclusion: Our study predicted a marked contribution of miRNA in regulating SMC transcriptomic profile. miR-200b was identified as a novel pro-differentiation miRNA in SMC through inhibition of phenotypic switching.