Vitronectin promotes TTR deposition and mitochondrial damage in ATTR-CA mice

Abstract Background Transthyretin cardiac amyloidosis (ATTR-CA) is an increasingly recognized disorder that leads to heart failure and cardiovascular death. However, the pathogenesis of ATTR-CA is still poorly understood. Vitronectin (VTN), a common component of the extracellular matrix, has been reported to be associate with amyloidosis. However, the role of VTN in TTR deposition has not been clarified. Purpose Here we aimed to elucidate the TTR deposition mechanism in ATTR-CA and test therapeutic interventions using a gene-edited ATTR-CA mice model. Methods We used CRISPR/Cas9-mediated genome engineering to create humanized wild-type TTR knock-in mice (hTTRWT). Cardiac function was examined by echocardiography and pressure-volume analysis. VTN expression was assessed by immunofluorescence and western blotting. Interactions among VTN and TTR are analyzed with in vitro pull-down and co-immunoprecipitation (Co-IP) assays. Recombinant TTR protein was added in the culture of VTN overexpressed mice primary cardiomyocytes (CMs) to simulate the TTR deposition process in vitro. Mitochondrial function was determined by the Seahorse assay and mitochondrial ultrastructure was evaluated with the transmission electron microscope.Additionally, we assessed the mitochondrial damage with mitoSOX staining. Results In the hTTRWT group, pressure-volume analysis and echocardiography revealed significant diastolic dysfunction and increased left ventricle chamber stiffness at 52 weeks. Compared to WT group, the hTTRWT group showed a dramatic elevation of VTN in hearts. Co-IP and pull-down assays confirmed a direct interaction between VTN and TTR. In cultured CMs exposed to recombinant TTR protein, VTN overexpression promotes the deposition of TTR. Damaged mitochondrial ultrastructure, elevated oxidative stress and decreased mitochondrial numbers were found. In accordance with observed mitochondrial abnormalities, seahorse experiments demonstrated impaired mitochondrial respiration capacity. Conclusion These results suggest that the VTN contributes to ATTR-related pathological and cardiac function changes and mitochondrial dysfunction as a contributor of disease progression from ATTR-CA to heart failure.