P5987Novel model of intensity graded murine wire-induced aortic valve stenosis mimics distinct stages of human aortic valve pathology
Authors: Niepmann S T , Steffen E , Zietzer A , Adam M , Nordsiek J , Gyamfi-Poku I , Piayda K , Sinning J M , Baldus S , Nickenig G , Zimmer S , Quast C 
Published: October 2019

Abstract

Background
Aortic valve stenosis (AS) is the most common valve disease requiring therapeutic intervention. Even though the incidence of AS has been continuously rising and AS is associated with significant morbidity and mortality, to date, no medical treatments have been identified that can modify disease progression. In fact, only invasive interventional or surgical replacement of severely diseased valves is recommended. This unmet medical need is likely attributed to the lack of a clear understanding of the molecular mechanism driving disease development. To investigate the pathophysiology leading to AS, reliable and reproducible animal models that mimic human pathophysiology are needed.

Hypothesis
Induction of a graded wire-induced aortic valve stenosis model in mice is feasible to reflect and study pathophysiological mechanisms underlying the progression of aortic valve stenosis.

Methods
We have tested and expanded the protocols of a novel wire-injury induced aortic valve stenosis mouse model. A spring coronary guide wire or a bare metal wire was used to apply shear stress to the aortic valve cusps with increasing intensity with ultrasound-guided monitoring in male 10 to 12-week-old C57Bl/6j mice. These protocols allowed the induction of distinct models with soft, moderate and intense wire injury. Functional analysis including maximum flow velocity (Vmax), ejection fraction, fractional shortening, left ventricular volumes, diameters and wall thickness were assessed by echocardiography before, one and four weeks after induction of aortic valve stenosis. Immunohistological analysis were performed after eight weeks (hematoxylin and eosin, von-Kossa staining, anti-CD68-staining).

Results
Upon moderate or severe injury, AS developed with a significant increase in aortic valve peak blood flow velocity. While moderate injury promoted solitary AS, severe-injury induced mixed aortic valve disease with concomitant mild to moderate aortic regurgitation. Only 5% of the mice who received a moderate injury displayed a mild aortic regurgitation. In the group of mice with intense injury 50% of the mice had a mild and 18,75% had a moderate aortic insufficiency. The changes in aortic valve function were reflected by dilation and hypertrophy of the left ventricle, as well as a decreased left ventricular ejection fraction after intense injury, while moderate injury did not show significant dilation of the left ventricle. Histological analysis revealed the three classic hallmarks of human disease with aortic valve thickening, increased macrophage infiltration and calcification eight weeks after injury.

Conclusion
Hereby, we demonstrate that the induction of a graded wire induced aortic valve stenosis model in mice mimicking relevant pathophysiological mechanisms is feasible to study disease progression. We extended existing protocols to induce moderate stenosis allowing to solely study aortic valve stenosis without relevant aortic valve regurgitation.

Acknowledgement/Funding
S.N. was funded by Else-Kröner-Fresenius-Foundation of the Medical Faculty of the University of Bonn