The role of cellular senescence in aortic dissection

Abstract Background Aortic dissection (AD) is a catastrophic disease with high mortality. Survived patients frequently suffer from serious complications due to progressive destruction of the aortic walls. Recently we have reported that cell proliferation precedes the inflammatory response which is important in AD development and progression. Since cell proliferation promotes cellular senescence that can induce inflammatory response through SASP (senescence-associated secretary phenotype), we hypothesized that cellular senescence plays a critical role in AD pathogenesis. Purpose To investigate if cellular senescence contributes to AD pathogenesis in mouse AD model. Methods and Results A mouse AD model was created by the continuous infusion of beta-aminopropionitrile and angiotensin II (BAPN+AngII) for 14days. BAPN+AngII infusion induced senescence markers and senescent cells in mouse AD model. Senescent cells, as demonstrated by the expression of senescence-associated beta-galactosidase, were evident in intimal endothelial cells, medial smooth muscle cells, adventitial macrophages, and fibroblasts. Rapamycin, an inhibitor of mTOR pathway, suppressed the expression of senescent cells on the aortic tissue and the senescent marker protein expression. To examine the role of cellular senescence in AD, we orally administrated ABT263 known as "senolytics" that eliminates senescent cells. ABT263 treatment prevented cellular senescence in mouse AD model. The AD mortality of ABT263 group was 35%, which was lower than that of vehicle group (66.7%, P < 0.05 by log-rank test). The severity of AD, as assessed by the lesion length in vehicle group was 33.2 ± 3.1mm, whereas that in ABT263 group was 24.6 ± 1.8mm (P < 0.05). Transcriptome analysis revealed that ABT263 treatment suppressed the immune and inflammatory response in the aorta before AD onset. Quantitative RT-PCR confirmed that ABT263 treatment prevented the induction of p21Cip1, interleukin-6, several chemokines and M1 macrophage marker CD80 and CD86. It is known that Jnk activation induces SASP and accelerates cellular senescence. Western blotting confirmed that ABT263 reduced the ratio of pJnk to total Jnk, which was induced by BAPN + AngⅡ. Moreover, aortic smooth muscle cells（SMCs）remained contractile phenotype in ABT263 group, whereas BAPN+AngII reduced that phenotype in vehicle group. Conclusions Cell proliferation via mTOR pathway causes cellular senescence in mouse AD model. Jnk activation was confirmed in mouse AD model. Cellular senescence contributes to AD progression and death associated with inflammatory responses including SASP, the differentiation to M1 macrophage, and the phenotype change of SMCs.Cellular senescence represents a potential predictor and a therapeutic target for AD.