MALDI-Imaging Mass Spectrometry: a step forward in the anatomopathological characterization of stenotic aortic valve tissue.

Fernando De La Cuesta,Mikel Azkargorta,Pedro L Sanchez,Luis R Padial,Felix Elortza,Maria G Barderas,Harkaitz Urreta,Finn Akerström,Laura Mourino-Alvarez,Francisco Fernandez-Aviles,Ibon Iloro,Iraide Escobes,Angel Pinto,Tamara Sastre-Oliva,Luis F Lopez-Almodovar

doi:10.1038/srep27106

Abstract

Aortic stenosis (AS) is the most common form of valve disease. Once symptoms develop, there is an inexorable deterioration with a poor prognosis; currently there are no therapies capable of modifying disease progression, and aortic valve replacement is the only available treatment. Our goal is to study the progression of calcification by matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) and get new insights at molecular level that could help in the understanding of this disease. In this work, we analyzed consecutive slices from aortic valve tissue by MALDI-IMS, to establish the spatial distribution of proteins and peptides directly from the surface of the histological sections. The analysis showed different structures corresponding to regions observed in conventional histology, including large calcification areas and zones rich in collagen and elastic fibers. Peptide extraction from the tissue, followed by liquid chromatography mass spectrometry analysis, provided the identification of collagen VI α-3 and NDRG2 proteins which correlated with the masses obtained by MALDI-IMS and were confirmed by immunohistochemistry. These results highlighted the molecular mechanism implied in AS using MALDI-IMS, a novel technique never used before in this pathology. In addition, we can define specific regions proving a complementary resolution of the molecular histology.

Highlights

Aortic valve stenosis (AS) is the most common valvular heart disease and the third most common cardiovascular disease affecting mainly people who are over 65 years of age
We present a more focused study in which we have followed the progression of the lesion on tissue with the purpose of elucidating specific molecular mechanisms involved in CAS and novel proteomic alterations
We present that novel MALDI-IMS analysis applied to 3 human AV tissue sections of the same valve, with different injury severity, revealed the existence of different regions which correlate to conventional histology

Summary

Introduction

Aortic valve stenosis (AS) is the most common valvular heart disease and the third most common cardiovascular disease affecting mainly people who are over 65 years of age. This study did not allow the localization of the proteins/peptides in a specific area of the tissue neither the follow-up of the lesion along the valve. To solve this limitation, we present a more focused study in which we have followed the progression of the lesion on tissue with the purpose of elucidating specific molecular mechanisms involved in CAS and novel proteomic alterations. We present that novel MALDI-IMS analysis applied to 3 human AV tissue sections of the same valve, with different injury severity, revealed the existence of different regions which correlate to conventional histology. Noteworthy these, two proteins have been previously related with matrix mineralization and apoptosis, which are mechanisms involved in the development of the CAS

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Conclusion