EM-BSEM outperformed immunostaining in characterizing bioprosthetic heart valves, where cells with uncertain immunophenotypes comprised ≥80% of cells, by distinguishing functional macrophage phenotypes.
Is EM-BSEM preferential over immunophenotyping for studying the cellular landscape of bioprosthetic heart valves?
EM-BSEM is proposed as a superior technique compared to immunostaining for studying the cellular landscape and function in failing bioprosthetic heart valves.
Hitherto, calcified aortic valves (AVs) and failing bioprosthetic heart valves (BHVs) have been investigated by similar approaches, mostly limited to various immunostaining techniques. Having employed multiple immunostaining combinations, we demonstrated that AVs retain a well-defined cellular hierarchy even at severe stenosis, whilst BHVs were notable for the stochastic degradation of the extracellular matrix (ECM) and aggressive infiltration by ECM-digesting macrophages. Leukocytes (CD45+) comprised ≤10% cells in the AVs but were the predominant cell lineage in BHVs (≥80% cells). Albeit cells with uncertain immunophenotype were rarely encountered in the AVs (≤5% cells), they were commonly found in BHVs (≥80% cells). Whilst cell conversions in the AVs were limited to the endothelial-to-mesenchymal transition (represented by CD31+α-SMA+ cells) and the formation of endothelial-like (CD31+CD68+) cells at the AV surface, BHVs harboured numerous macrophages with a transitional phenotype, mostly CD45+CD31+, CD45+α-SMA+, and CD68+α-SMA+. In contrast to immunostaining, which was unable to predict cell function in the BHVs, our whole-specimen, nondestructive electron microscopy approach (EM-BSEM) was able to distinguish between quiescent and matrix-degrading macrophages, foam cells, and multinucleated giant cells to conduct the ultrastructural analysis of organelles and the ECM, and to preserve tissue integrity. Hence, we suggest EM-BSEM as a technique of choice for studying the cellular landscape of BHVs.
Kostyunin et al. (Sat,) conducted a other in Calcified aortic valves and failing bioprosthetic heart valves. Embedding and Backscattered Scanning Electron Microscopy (EM-BSEM) vs. Immunostaining was evaluated on Distinguishing cell types and predicting cell function. EM-BSEM outperformed immunostaining in characterizing bioprosthetic heart valves, where cells with uncertain immunophenotypes comprised ≥80% of cells, by distinguishing functional macrophage phenotypes.