Mass Spectrometry Imaging of Drug Related Crystal-Like Structures in Formalin-Fixed Frozen and Paraffin-Embedded Rabbit Kidney Tissue Sections

Abstract

A multimodal mass spectrometry imaging (MSI) based approach was used to characterize the molecular content of crystal-like structures in a frozen and paraffin embedded piece of a formalin-fixed rabbit kidney. Matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) imaging and desorption electrospray ionization (DESI) mass spectrometry imaging were combined to analyze the frozen and paraffin embedded sample without further preparation steps to remove the paraffin. The investigated rabbit kidney was part of a study on a drug compound in development, in which severe renal toxicity was observed in dosed rabbits. Histological examination of the kidney showed tubular degeneration with precipitation of crystal-like structures in the cortex, which were assumed to cause the renal toxicity. The MS imaging approach was used to find out whether the crystal-like structures were composed of the drug compound, metabolites, or an endogenous compound as a reaction to the drug administration. The generated MALDI-MSI data were analyzed using principal component analysis. In combination with the MS/MS results, this way of data processing demonstrates that the crystal structures were mainly composed of metabolites and relatively little parent drug.Graphical Abstractᅟ

Detection of small molecule concentration gradients in ocular tissues and humours

“…A variety of section thicknesses (20‐70 μm) were trialled, however sections from whole fresh‐frozen eyeball sections could not be collected consistently without additional sectioning aid. While the ability to study small molecule distributions from fixed tissue has been shown, generally, these distributions have been generated from tissue areas . Therefore, whole eyeball fixation (crosslinking or dehydration) was not considered since the more water‐soluble small molecules and metabolites were unlikely to maintain their in vivo localisation during the fixation process, particularly in the highly aqueous ocular humours.…”

Label-free molecular imaging of the kidney

“…82,112–114 Nilsson et al . 112 utilized IMS to examine the accumulation of preclinical crystalline deposits within the kidney, which are common phenotypes of nephrotoxicity that are often difficult to identify.…”

Integration of 3D multimodal imaging data of a head and neck cancer and advanced feature recognition

“…In pathology it is inevitable to have standard protocols for the use of formalin fixed paraffin embedded (FFPE) tissue including deparaffinization, tryptic digestion, and matrix application [38][39][40][41]. The data processing pipeline with registration and segmentation tools has to be adapted for a specific diagnostic question as well.…”