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

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

Recent technological developments in MALDI-MSI based hair analysis

Hair is a common piece of trace evidence found at a crime scene, however, often it is not possible to obtain DNA (due to the lack of a follicular root). These hair samples could potentially provide other intelligence, based on the molecular history of an individual that it contains. Currently, this type of analysis is performed using traditional hyphenated techniques gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS). However, these techniques require a large amount of hair, not a few single strands such as those typically found at a crime scene and also involve extensive sample preparation. Recently new technologies such as matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) have been used to monitor the distribution of drugs of abuse in single hair strands. Using this technology it is possible to reveal the distribution of compounds in the hair more accurately and in single strands as opposed to milligram quantities required by traditional hyphenated methods. The use of MALDI-MSI could provide law enforcement agencies with lifestyle information on an individual and help to narrow down the pool of suspects