Abstract 125: Sex-dependent Effects of Sortilin Antisense Oligonucleotide on Vascular Calcification

Background: The development of atherosclerotic calcification is a complex process associated with an increased risk of cardiovascular events. Despite decades of extensive studies, this disorder has no effective therapeutic strategies. Previous studies demonstrated that genetic deletion of sortilin (Sort1) decreased vascular smooth muscle cell (SMC) calcification in experimental atherosclerosis. We hypothesized that silencing sortilin expression in vivo using antisense oligonucleotide (ASO-Sort1) will offer a promising strategy to prevent vascular calcification. Methods and Results: Male and female Ldlr-/- mice (n=10 per group) were fed a high-fat diet and administered with ASO-Sort1 for 15 weeks. While ASO treatment reduced aortic sortilin expression at a similar range of 52% and 57% in female and male mice, respectively, female mice displayed lower basal expression of Sort1 than male. After ASO-Sort1 treatment, we assessed atherosclerotic lesion formation and calcification of the aorta using molecular imaging and histology. While treatment had no effect on body weight, plasma cholesterol, and progression of atherosclerosis in either sex, it prevented the development of aortic calcification exclusively in male mice. To assess the sex-dependent mechanism involved, we analyzed the changes of the aortic proteome in both groups of mice treated with ASO-Sort1. Our results showed a reduction of vesicular trafficking pathways in both male and female mice; however, other biological processes including autophagy showed sex-dependent inhibitions only in male mice. To validate our findings, we explored in vitro whether 17β-estradiol (E2) treatment of mouse SMCs promotes calcification independently of sortilin. Results showed that E2 induces calcification in SMC treated with ASO-Sort1. Conclusion: Targeting sortilin using antisense technology is efficient to prevent vascular calcification in male mice; however, this effect was lost in female mice due to a sortilin-independent development of calcification mediated by E2. This unexpected outcome highlighted a novel sex-dependent discrepancy of the calcification pathway mediated by sortilin.