High-spatial resolution matrix-assisted laser desorption ionization imaging analysis of glucosylceramide in spleen sections from a mouse model of Gaucher Disease

Abstract

MALDI mass spectrometric imaging (MSI) enables spatially resolved mass and intensity information to be obtained directly from tissue sections, thereby illustrating how analytes are distributed within these sections. Here we have used an oversampling technique on a commercially available MALDI orthogonal acceleration TOF mass spectrometer with ion mobility separation capability to produce high spatial resolution images of the glycosphingolipid, glucosylceramide (GC). To exemplify the biological application of our approach, GC was imaged in spleen sections from a conditional knockout mouse model of type 1 Gaucher disease in which the catabolism of this glycosphingolipid is impaired. The laser was continually fired at one position until no more ions were observed and then the sample was moved by 15 μm (laser diameter ~150 μm). Ions were generated from only the unirradiated surface at each of these positions achieving an effective spacing of 15 μm. At 15 μm laser step-size, it was possible to visualize macrophages enriched in GC, which could be distinguished from other cell types in the spleen. Current MALDI MSI spatial resolution is typically limited by the diameter of the laser spot-size, which is usually between 50 and 100 μm, covering an area equivalent to tens of mammalian cells.