Objective A cardinal feature of Marfan syndrome is thoracic aortic aneurysm (TAA). The contribution of ligand-dependent stimulation of angiotensin II receptor type 1a (AT1aR) to TAA progression remains controversial because the beneficial effects of angiotensin receptor blockers have been ascribed to off-target effects. This study used genetic and pharmacologic modes of attenuating angiotensin receptor and ligand, respectively, to determine their roles on TAA in mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+).
Approach and Results TAA in Fbn1C1041G/+ mice were determined in both sexes and found to be strikingly sexual dimorphic. Males displayed progressive dilation over 12 months while ascending aortic dilation in Fbn1C1041G/+ females did not differ significantly from wild type mice. To determine the role of AT1aR, Fbn1C1041G/+ mice that were either +/+ or −/− for AT1aR were generated. AT1aR deletion reduced progressive expansion of ascending aorta and aortic root diameter from 1 to 12 months of age in males. Medial thickening and elastin fragmentation were attenuated. An antisense oligonucleotide against angiotensinogen (AGT-ASO) was administered to male Fbn1C1041G/+ mice to determine the effects of angiotensin II depletion. AGT-ASO administration, at doses that markedly reduced plasma AGT concentrations, attenuated progressive dilation of the ascending aorta and aortic root. AGT-ASO also reduced medial thickening and elastin fragmentation.
Conclusions Genetic approaches to delete AT1aR and deplete AngII production exerted similar effects in attenuating pathology in the proximal thoracic aorta of male Fbn1C1041G/+ mice. These data are consistent with ligand (AngII) dependent stimulation of AT1aR being responsible for aortic disease progression.
Highlights
Profound sexual dimorphism of aortic disease occurs in Fbn1C1041G/+ mice, with female mice being more resistant and male mice being more susceptible.
Inhibition of the AngII-AT1aR axis attenuates aortic pathology in male Fbn1C1041G/+ mice.
MS, AD, HL, and JC have submitted a patent application for use of antisense oligonucleotides targeted against angiotensinogen in thoracic aneurysmal disease. AM is an employee of Ionis Pharmaceuticals, who provided the Control ASO and AGT ASO. Ionis Pharmaceuticals did not provide funding for this study.
