METTL14-dependent m6A regulates vascular calcification induced by indoxyl sulfate.

Aims: Although the functional importance of N6-methyladenosine (m6A) in various fundamental bioprocesses are well known, its effect on vascular calcification is not well studied. We investigated the role of methyltransferase-like 14 (METTL14), an m6A methylase, in vascular calcification.

Main Methods: We used clinical human samples as well as rat models and primary human artery smooth muscle cell (HASMC) cultures to study the functional role of m6A and METTL14 in vascular calcification and in HASMCs. We modulated the expression of METTL14 using siRNAs (in vitro) to study its function in regulating HASMCs m6A, osteoblasts induced by indoxyl sulfate. We performed the MeRIP-qPCR assays to map and validate m6A in individual transcripts, controls, and calcific HASMCs.

Key Findings: We discovered that the METTL14 expression increases in calcific arteries and in HASMCs induced by indoxyl sulfate, thereby increasing the m6A level in RNA and decreasing the vascular repair function. Decreasing the expression of METTL14 in calcified arteries attenuated the indoxyl sulfate-induced increase in m6A and decrease in HASMCs calcification. We performed the methylation activity of METTL14, which selectively methylates vascular osteogenic transcripts, thereby promoting their degradation and improving their protein expression induced by indoxyl sulfate. Moreover, we demonstrated that the METTL14 de-expression in HASMCs models of calcification decreased the calcification and enhanced the vascular repair function.

Significance: Collectively, our results demonstrated the functional importance of METTL14-dependent vascular m6A methylome in vascular functions during calcification and provided a novel mechanistic insight to the therapeutic mechanisms of METTL14.