Angiotensin II Promotes Mitral Valve and Left Atrial Pathology in Fibrillin-1C1041G/+ Mice

Authors

Franklin, M. K., Howatt, D. A., Pettey, A. C., Moorleghen, J. J., Levitan, B. M., Mullick, A. E., Saffitz, J., Lu, H. S., Daugherty, A.

Abstract

Background: Activation of the renin-angiotensin system (RAS) contributes to aortic diseases caused by fibrillin-1 haploinsufficiency (Fbn1C1041G/+). However, whether RAS activation influences mitral valve disease associated with FBN1 variants remains undefined. This study determined whether inhibition or augmentation of the RAS affects mitral valve pathology in Fbn1C1041G/+ mice. Methods: Angiotensinogen (AGT) antisense oligonucleotides (ASOs) were administered for 12 weeks to inhibit the RAS in male and female Fbn1C1041G/+ mice. To augment the RAS, mice were infused with angiotensin II (AngII; 1,000 ng/kg/min) for 28 days. Mitral valve and heart function were monitored by ultrasound. At termination, hearts were dissected free and tissue sectioned to assess mitral valve leaflet thickness and pathology. Results: Mitral valve leaflet thickness was significantly increased in Fbn1C1041G/+ mice compared to Fbn1+/+ littermates of both sexes. ASO-mediated AGT inhibition did not alter this phenotype despite markedly reduced plasma AGT concentrations. AngII infusion increased mitral valve leaflet thickness in Fbn1C1041G/+ mice with increased proteoglycan and collagen content, while exerting minimal effects in Fbn1+/+ mice. Twenty-five percent of AngII-infused Fbn1C1041G/+ mice died of non-vascular causes. Ultrasound showed mitral valve dysfunction in AngII-infused Fbn1C1041G/+ mice. Grossly expanded left atria were common in AngII-infused Fbn1C1041G/+ mice. These markedly enlarged left atria contained increased fibrosis, macrophage accumulation, and platelet-rich masses. Conclusions: Mitral valves of Fbn1C1041G/+ mice did not respond to AGT inhibition but were markedly more susceptible to AngII infusion, with greater increases in thickness and compositional changes than mitral valves of Fbn1+/+ mice. In addition, AngII promoted mitral valve dysfunction that were associated with pronounced left atrial pathology.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 10 Oct 2026.

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