Association between premature vascular smooth muscle cells senescence and vascular inflammation in Takayasu's arteritis.

Objectives: Arterial wall inflammation and remodelling are the characteristic features of Takayasu's arteritis (TAK). It has been proposed that vascular smooth muscle cells (VSMCs) are the main targeted cells of inflammatory damage and participate in arterial remodelling in TAK. Whether VSMCs are actively involved in arterial wall inflammation has not been elucidated. Studies have shown that cellular senescence in tissue is closely related to local inflammation persistence. We aimed to investigate whether VSMCs senescence contributes to vascular inflammation and the prosenescent factors in TAK.

Methods: VSMCs senescence and senescence-associated secretory phenotype were detected by histological examination, bulk RNA-Seq and single-cell RNA-seq conducted on vascular surgery samples of TAK patients. The key prosenescent factors and the downstream signalling pathway were investigated in a series of in vitro and ex vivo experiments.

Results: Histological findings, primary cell culture and transcriptomic analyses demonstrated that VSMCs of TAK patients had the features of premature senescence and contributed substantially to vascular inflammation by upregulating the expression of senescence-associated inflammatory cytokines. IL-6 was found to be the critical cytokine that drove VSMCs senescence and senescence-associated mitochondrial dysfunction in TAK. Mechanistically, IL-6-induced non-canonical mitochondrial localisation of phosphorylated STAT3 (Tyr705) prevented mitofusin 2 (MFN2) from proteasomal degradation, and subsequently promoted senescence-associated mitochondrial dysfunction and VSMCs senescence. Mitochondrial STAT3 or MFN2 inhibition ameliorated VSMCs senescence in ex vivo cultured arteries of TAK patients.

Conclusions: VSMCs present features of cellular senescence and are actively involved in vascular inflammation in TAK. Vascular IL-6-mitochondrial STAT3-MFN2 signalling is an important driver of VSMCs senescence.