Abstract
Pathological ECM remodelling and biomineralization in human aortic valve and bioprosthesis tissue were investigated by Fourier transformed infrared (FT-IR) spectroscopic imaging and multivariate data analysis. Results of histological von Kossa staining to monitor hydroxyapatite biomineralization correlated to the definition of mineralized tissue using FT-IR spectroscopic imaging. Spectra exhibit signals of carbonate and phosphate groups of hydroxyapatite. Proteins could be identified by the amide I and amide II bands. Proteins were detected in the calcified human aortic valve tissue, but no absorption signals of proteins were observed in the mineralized bioprosthesis sample region. A shift of the amide I band from 1654 cm−1 to 1636 cm−1 was assumed to result from β-sheet structures. This band shift was observed in regions where the mineralization process had been identified but also in non-mineralized bioprosthesis tissue independent of prior implantation. The increased occurrence of β-sheet conformation is hypothesized to be a promoter of the biomineralization process. FT-IR spectroscopic imaging offers a wealth of chemical information. For example, slight variations in band position and intensity allow investigation of heterogeneity across aortic valve tissue sections. The exact evaluation of these properties and correlation with conventional histological staining techniques give insights into aortic valve tissue remodelling and calcific pathogenesis.
Highlights
Aortic valve (AV) stenosis has a prevalence of more than 4.6 % in the population older than 75 [1,2].This has social and economic relevance especially for the healthcare system
The correlation of certain spectroscopic parameters in fingerprint regions for characteristics of apatite and/or amide protein characteristics with pathological mechanisms of dystrophic mineralization or osteogenesis is the aim of ongoing research. This demands the histological evaluation of human AV sections in parallel to Fourier transformed infrared (FT-IR) spectroscopy and the definition of chemical properties according to extracellular matrix (ECM) niches and calcified nodule morphology comparable to bone tissue evaluation [50]
This study reports on the use of IR spectroscopy for the characterization and classification of mineralized human AV and bioprosthesis tissues
Summary
Aortic valve (AV) stenosis has a prevalence of more than 4.6 % in the population older than 75 [1,2] This has social and economic relevance especially for the healthcare system. Fibrosis and calcific degeneration of AV tissue are the main pathological features leading to the need for surgical replacement of the AV leaflets by mechanical or preferentially biological prostheses [1,3]. Mineralization is the result of changes in the extracellular matrix (ECM) by dystrophic intercalation, for example, after cell necrosis/apoptosis. It is said to result from an active cell-driven process in neoosteogenesis [1,3,4,5,6,7]. It has been proposed that the deterioration of biological
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