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You are here: Contents > 2016 > Volume 25 Number 2 March 2016 > MISCELLANEOUS > MALDI Imaging Mass Spectrometry as a Lipidomic Approach to Heart Valve Research

MALDI Imaging Mass Spectrometry as a Lipidomic Approach to Heart Valve Research

Peggi M. Angel1, Ahmed S. Bayoumi2, Robert B. Hinton3, Yan Ru Su5, David Bichell4, John E. Mayer6, H. Scott Baldwin7, Richard M. Caprioli8

1Department of Cell and Molecular Pharmacology & Experimental Therapeutics Medical University of South Carolina, Charleston, SC, 2Department of Cardiac Surgery, Boston Children’s Hospital, Wyss Institute for Biologically Inspired Engineering & Harvard Medical School, Boston, MA, 3Division of Cardiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, 4Division of Pediatric Cardiac Surgery, Vanderbilt University Medical Center, Nashville, TN, 5Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 6Department of Cardiac Surgery, Boston Children’s Hospital & Harvard Medical School, Boston, MA, 7Department of Pediatrics and Cell Development and Biology, Vanderbilt University Medical Center, Nashville, TN, 8Mass Spectrometry Research Center and Department of Biochemistry, Medicine, Pharmacology and Chemistry, Vanderbilt University Medical Center, Nashville, TN, USA

Background and aim of the study: Valvular disease is characterized in part by lipid deposition, but systematic analysis of the patterns of global lipid expression in healthy and diseased valve tissues are unknown. This is due in part to tissue limitations for lipidomic preparations and technologies for evaluating lipid distribution in tissues. The study aim was to examine the application of matrixassisted laser desorption ionization imaging mass spectrometry (MALDI IMS) to the aortic valve during development and disease, as an approach to detect and map lipids and ultimately better understand valve structure and function.

Methods: Established MALDI IMS strategies were applied to thin tissue sections of heart valves to map lipids to corresponding morphological features. Healthy prenatal and adult ovine aortic valve tissues were evaluated using the developed techniques. Lipid expression levels were compared between prenatal and adult valves using Wilcoxon rank sum testing and area under the receiver operating curves. A classification algorithm was used to determine distinct lipid signatures in adult extracellular matrix (ECM)

substructures, including fibrosa and spongiosa layers. Lipid patterns were examined in heart valve tissue from pediatric patients with congenital aortic valve stenosis (CAVS).

Results: Lipid levels were decreased in adult ovine aortic valves when compared with prenatal valves. Classification algorithms applied to lipid signatures reported distinct lipid signatures mapping to ECM substructures in the adult aortic valve, but could not distinguish amorphous structures at pre-natal day 5. In CAVS, the in-situ lipid aggregation of distinct lipid species showed unique patterning both concurrent and divergent with ECM disarray. Fatty acid content varied between normal and diseased human aortic valves.

Conclusion: MALDI IMS provides a new and useful approach to evaluate lipid biology in heart valve tissue. These findings define a role for lipid regulation in aortic valve development and demonstrate patterns of lipid deregulation in congenital disease.

The Journal of Heart Valve Disease 2016;25:240-252

MALDI Imaging Mass Spectrometry as a Lipidomic Approach to Heart Valve Research

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