Increased vascular smooth muscle cell senescence in aneurysmal Fibulin-4 mutant mice

Aortic aneurysms are dilations of the aorta that can rupture when left untreated. We used aneurysmal Fibulin-4R/R to further unravel the underlying mechanisms of aneurysm formation. RNA sequencing of 3-month-old Fibulin-4R/R aortas revealed significant upregulation of senescence-associated secretory phenotype (SASP) factors and key senescence factors, indicating involvement of senescence. Analysis of aorta histology and of vascular smooth muscle cells (VSMCs) in vitro confirmed the senescent phenotype of Fibulin-4R/R VSMCs by revealing increased SA-ß-gal, p21 and p16 staining, increased IL-6 secretion, increased presence of DNA damage foci and increased nuclei size. Additionally, we found that p21 luminescence was increased in the dilated aorta of Fibulin-4R/R|p21-Luciferase mice. Our studies identify a cellular aging cascade in Fibulin-4 aneurysmal disease, by revealing that Fibulin-4R/R aortic VSMCs have a pronounced SASP and a senescent phenotype that may underlie aortic wall degeneration. Additionally, we demonstrated the therapeutic effect of JAK/STAT and TGF-ß pathway inhibition as well as senolytic treatment on Fibulin-4R/R VSMCs in vitro. These findings can contribute to improved therapeutic options for aneurysmal disease aimed at reducing senescent cells. Overall design: To investigate the underlying molecular mechanism of aneurysm formation, we performed RNA sequencing on the aortic arch of Fibulin-4 R/R mice and wildtype littermates at 3 months of age. Next, differential expression analysis was performed to compare the RNA expression in Fibulin-4 R/R aorta's to the RNA expression in wildtype aorta's.