Background: Aortic valve degeneration (DAVD) is a progressive disease beginning with small alterations at the level of cell morphology and function. Emerging evidence suggests that mitochondrial dysfunction may be involved in DAVD. Increased mitochondrial stress might lead to increased generation of reactive oxygen species promoting aortic valve degeneration. There is little known about how mitochondrial function of aortic valve cells is affected by diabetes mellitus type II (DM II), a common risk factor of DAVD. New Zealand Obese mice, a murine model of moderate DM II, were demonstrated to spontaneously develop DAVD.

Hypothesis: We hypothesize that measurement of mitochondrial function is feasible in aortic valve tissue in a murine model of wire injury induced aortic valve stenosis. Key parameters of mitochondrial function may be altered in aortic valve tissue after wire-injury induced aortic valve stenosis and in murine models of DM II.

Methods: In 10-12 weeks old male C57BL/6 (wild type) mice experimental aortic valve stenosis (AVS) was induced by a wire injury procedure. For this purpose, a coronary wire was used to apply shear stress to the aortic valve leaflets. A matching control group underwent a sham operation without advancing the wire across the aortic valve. Echocardiographic assessment of aortic valve peak flow velocity was used to measure severity of AVS. Real time respirometry of aortic valve tissue was used to measure mitochondrial oxygen consumption rate (OCR). Modulators of mitochondrial respiration (ATP-synthase inhibitor, uncoupling agent, complex I and III inhibitor) were added in a plate-based live cell assay to induce mitochondrial stress. To evaluate the influence of DM II on aortic valve mitochondrial function, aortic valve tissue from New Zealand Obese mice (NZO) was analysed in a similar fashion. RNA sequencing was used to evaluate regulation of mitochondrial genes in murine stenotic aortic valve tissue.

Results: Key parameters of mitochondrial function (coupling efficiency, proton leak, spare respiratory capacity) differed significantly in stenotic aortic valve tissue compared to sham operated mice. Analysis of aortic valve tissue of diabetic NZO mice showed increased mitochondrial stress reflected by reduced coupling efficiency, spare respiratory capacity and increased proton leak. RNA sequencing analysis revealed that genes involved in mitochondrial function were the most differently regulated genes in this murine model of wire injury induced AVS.

Conclusion: Analysis of mitochondrial function in a murine model of wire injury induced aortic valve stenosis by real time measurement of mitochondrial OCR is feasible and allows to evaluate key parameters of mitochondrial function in AVS. Mitochondrial function of aortic valve cells is differently regulated in a murine model of AVS and a model of moderate DM II.