MALDI mass spectrometry imaging workflow for the aquatic model organisms Danio rerio and Daphnia magna

Abstract

Lipids play various essential roles in the physiology of animals. They are also highly dependent on cellular metabolism or status. It is therefore crucial to understand to which extent animals can stabilize their lipid composition in the presence of external stressors, such as chemicals that are released into the environment. We developed a MALDI MS imaging workflow for two important aquatic model organisms, the zebrafish (Danio rerio) and water flea (Daphnia magna). Owing to the heterogeneous structure of these organisms, developing a suitable sample preparation workflow is a highly non-trivial but crucial part of this work and needs to be established first. Relevant parameters and practical considerations in order to preserve tissue structure and composition in tissue sections are discussed for each application. All measurements were based on high mass accuracy enabling reliable identification of imaged compounds. In zebrafish we demonstrate that a detailed mapping between histology and simultaneously determined lipid composition is possible at various scales, from extended structures such as the brain or gills down to subcellular structures such as a single axon in the central nervous system. For D. magna we present for the first time a MALDI MSI workflow, that demonstrably maintains tissue integrity during cryosectioning of non-preserved samples, and allows the mapping of lipids in the entire body and the brood chamber inside the carapace. In conclusion, the lipid signatures that we were able to detect with our method provide an ideal basis to analyze changes caused by pollutants in two key aquatic model organisms.

Cross-Species Extrapolation of Biological Data to Guide the Environmental Safety Assessment of Pharmaceuticals—The State of the Art and Future Priorities

“…Such MS‐based approaches could also be used to detect changes in protein expression and more precisely reveal the distribution of a given drug target (Brunner et al, 2022; Lombard‐Banek et al, 2016). These approaches have already started to be applied to ecotoxicologically relevant species groups such as daphnids and zebrafish (Perez et al, 2017; Schirmer et al, 2022), achieving relatively high levels of spatial resolution. Integrating these techniques with those discussed for the investigation of target function (e.g., in vivo imaging and gene editing) could prove incredibly powerful in identifying tissue‐specific drug concentrations needed to trigger phenotypically observable target‐mediated effects.…”