Validating MALDI-IMS Feasibility in Ex Vivo Brain Slices

Matrix-assisted laserdesorption ionization imaging massspectrometry(MALDI-IMS) generates unique mass spectra in X/Y coordinates across a tissue sample, thus allowing forthe spatial detection and relative quantification of biologic compounds in situ. The soft ionization of MALDI-IMS makes it an idealtechnique for high-resolution imaging of complex lipid species. Lipid-basedspatial chemical maps derived from MALDI-IMS provide critical insightinto the unique molecular profiles of a variety of neurologic diseases. Ex vivo brain slice preparations are a prominent alternativeto in vivo animal models for studying many differentneurologic conditions. For the first time, we present a feasible protocolfor achieving reproducible lipidomic MALDI-IMS data from exvivo rat brain slices and provide evidence that exvivo brain slices maintain spatiochemical lipidomic profilesrepresentative of an intact whole brain. We conducted a methods comparisonassessing the lipid profiles within the neocortex, striatum, and corpuscallosum between coronal sections taken from ex vivo brain slices and the current gold standard tissue preparation method,fresh frozen whole brains. For the first time we demonstrate a techniqueby which 400 & mu;m ex vivo brain slices can beextracted from an imaging chamber and prepared for MALDI-IMS in away that preserves their lipidomic integrity. We demonstrate the feasibilityof MALDI-IMS in ex vivo brain slices and providea roadmap for MALDI-IMS utilization in uncharted neuroscience fields.