Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) enables acquisition of spatial distribution maps for molecular species in situ. This can provide comprehensive insights on the pathophysiology of different diseases. However, current sample preparation and MALDI-IMS acquisition methods have limitations in preserving molecular and histological tissue morphology, resulting in interfered correspondence of MALDI-IMS data with subsequently acquired immunofluorescent staining results. We here investigated the histology compatibility of MALDI-IMS to image neuronal lipids in rodent brain tissue with subsequent immunohistochemistry and fluorescent staining of histological features. This was achieved by sublimation of a low ionization energy matrix compound, 1,5-diaminonapthalene (1,5-DAN), minimizing the number of low-energy laser shots. This yielded improved lipid spectral quality and speed of data acquisition and reduced matrix cluster formation along with preservation of specific histological information at cellular levels. This gentle, histology-compatible MALDI-IMS protocol also diminished thermal effects and mechanical stress created during nanosecond laser ablation processes that were prominent in subsequent immunofluorescent staining images but not with classical hematoxylin and eosin (H&E) staining on the same tissue section. Furthermore, this methodology proved to be a powerful strategy for investigating β-amyloid (Aβ) plaque-associated neuronal lipids as exemplified by performing high-resolution MALDI-IMS with subsequent fluorescent amyloid staining in a transgenic mouse model of Alzheimer's disease (tgSwe).

Radiotherapy in children causes debilitating cognitive decline, partly linked to impaired neurogenesis. Irradiation targets primarily cancer cells but also endogenous neural stem/progenitor cells (NSPCs) leading to cell death or cell cycle arrest. Here we evaluated the effects of lithium on proliferation, cell cycle and DNA damage after irradiation of young NSPCs in vitro.NSPCs were treated with 1 or 3 mM LiCl and we investigated proliferation capacity (neurosphere volume and bromodeoxyuridine (BrdU) incorporation). Using flow cytometry, we analysed apoptosis (annexin V), cell cycle (propidium iodide) and DNA damage (γH2AX) after irradiation (3.5 Gy) of lithium-treated NSPCs.Lithium increased BrdU incorporation and, dose-dependently, the number of cells in replicative phase as well as neurosphere growth. Irradiation induced cell cycle arrest in G1 and G2/M phases. Treatment with 3 mM LiCl was sufficient to increase NSPCs in S phase, boost neurosphere growth and reduce DNA damage. Lithium did not affect the levels of apoptosis, suggesting that it does not rescue NSPCs committed to apoptosis due to accumulated DNA damage.Lithium is a very promising candidate for protection of the juvenile brain from radiotherapy and for its potential to thereby improve the quality of life for those children who survive their cancer.

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