Abstract 522: TGF-beta Neutralization Augments Development of Angiotensin II-induced Aneurysms in Both Ascending and Abdominal Aortic Regions

Abstract

Introduction and Objectives Angiotensin II (AngII) infusion induces ascending and abdominal aortic aneurysms (AAs) in mice. In a mouse model of Marfan Syndrome expressing Fbn1 C1039G/+ , ascending AAs were reduced by administration of a transforming growth factor-beta (TGF-beta) neutralizing antibody. In contrast, administration of TGF-beta neutralizing antibodies to AngII-infused mice increased aortic rupture. The purpose of this study was to compare the effects of TGF-beta neutralization on formation and progression of AngII-induced ascending and abdominal AAs. Methods and Results Male C57BL/6 mice were fed a normal diet and infused subcutaneously with AngII (1,000 ng/kg/min). Five days prior to initiating infusion, mice were injected i.p. with either a mouse monoclonal TGF-beta antibody (1D11) or an isotype matched IgG at a dose of either 0.3 or 5 mg/kg x 3/per week. 1D11 administration significantly decreased serum TGF-beta concentrations. TGF-beta neutralization at 5 mg/kg greatly increased the incidence of aortic rupture, which was attributed to rupture in both the ascending and abdominal regions. For mice that remained viable after 28 days of infusion, there were equivalent increases in aortic dilation in both the ascending and abdominal regions. Prior to rupture, aortic diameters determined by ultrasound demonstrated no significant effect on AngII-induced dilation of the ascending or abdominal aorta. We also studied the effects of TGF-beta neutralization in mice with established AngII-induced AAs following AngII-infusion for 28 days. C57BL/6 mice were injected with the mouse TGF-beta neutralizing antibody or IgG control (5 mg/kg x 3/per week, n=10 per group), while AngII infusion was continued for a further 28 days. Although TGF-beta antibody administration significantly decreased serum TGF-beta concentrations in mice with established AAs, there was no effect on aortic rupture or dilation of either the ascending or abdominal aortic region. Conclusion TGF-beta inhibition augmented AngII-induced aortic rupture in both the ascending and abdominal regions but had no effect on dilation. Furthermore, TGF-beta neutralization had no effect on either aortic rupture or expansion in established AAs.