Distinguishing core from penumbra by lipid profiles using Mass Spectrometry Imaging in a transgenic mouse model of ischemic stroke

I A Mulder,A M J M Van Den Maagdenberg,R M A Heeren,L A M Broos,A Prop,N Ogrinc Potočnik,M J H Wermer

doi:10.1038/s41598-018-37612-5

I A Mulder, A M J M Van Den Maagdenberg + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-37612-5

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Abstract

Detecting different lipid profiles in early infarct development may give an insight on the fate of compromised tissue. Here we used Mass Spectrometry Imaging to identify lipids at 4, 8 and 24 hours after ischemic stroke in mice, induced by transient middle cerebral artery occlusion (tMCAO). Combining linear transparency overlay, a clustering pipeline and spatial segmentation, we identified three regions: infarct core, penumbra (i.e. comprised tissue that is not yet converted to core), and surrounding healthy tissue. Phosphatidylinositol 4-phosphate (m/z = 965.5) became visible in the penumbra 24 hours after tMCAO. Infarct evolution was shown by 2D-renderings of multiple phosphatidylcholine (PC) and Lyso-PC isoforms. High-resolution Secondary Ion Mass Spectrometry, to evaluate sodium/potassium ratios, revealed a significant increase in sodium and a decrease in potassium species in the ischemic area (core and penumbra) compared to healthy tissue at 24 hours after tMCAO. In a transgenic mouse model with an enhanced susceptibility to ischemic stroke, we found a more pronounced discrimination in sodium/potassium ratios between penumbra and healthy regions. Insight in changes in lipid profiles in the first hours of stroke may guide the development of new prognostic biomarkers and novel therapeutic targets to minimize infarct progression.

Highlights

Ischemic stroke is a severe neurological event and its incidence in Western society is increasing[1]
We revealed the presence of cardiolipin (CL) lipids and ganglioside (GM) lipids, no changes with respect to spatial or temporal distribution relevant to ischemic infarct evolution were observed (Supplementary Table S2)
High-resolution Secondary Ion Mass Spectrometry (SIMS) imaging combined with rapid lipid detection with Matrix-Assisted Laser Desorption Ionization (MALDI)-Mass Spectrometry Imaging (MSI) is able to identify molecular profiles that can distinguish the ischemic and non-ischemic regions after experimentally induced stroke

Summary

Introduction

Ischemic stroke is a severe neurological event and its incidence in Western society is increasing[1]. Identification of the molecular species in the different regions of the ischemic area, especially in the early stages of infarct development, is crucial to identify the molecular mechanisms that may determine the fate of the penumbra. Mass Spectrometry Imaging (MSI) is a powerful technique for identifying hundreds of molecules simultaneously within a single tissue section in a histological context[8,9]. Later studies reduced the matrix effect, by either desalting the tissue sections prior to MALDI or using an internal standard as a normalization factor, and revealed different distributions of phospholipids[14,15]. An increase of LPC (16:0) was observed in the ischemic region with concomitant membrane degradation of free fatty acids and the degradation of PCs into LPCs4,6

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