Spatial Localization of Vitamin D Metabolites in Mouse Kidney by Mass Spectrometry Imaging

Abstract

Vitamin D plays a key role in the maintenance of calcium/phosphate homeostasis and elicits biological effects that are relevant to immune function and metabolism. It is predominantly formed through UV exposure in the skin by conversion of 7-dehydrocholsterol (vitamin D3). The clinical biomarker, 25-hydroxyvitamin D (25-(OH)-D), is enzymatically generated in the liver with the active hormone 1,25-dihydroxyvitamin D then formed under classical endocrine control in the kidney. Vitamin D metabolites are measured in biomatrices by liquid chromatography–tandem mass spectrometry (LC–MS/MS). In LC–MS/MS, chemical derivatization (CD) approaches have been employed to achieve the desired limit of quantitation. Recently, matrix-assisted laser desorption/ionization (MALDI) has also been reported as an alternative method. However, these quantitative approaches do not offer any spatial information. Mass spectrometry imaging (MSI) has been proven to be a powerful tool to image the spatial distribution of molecules from the surface of biological tissue sections. On-tissue chemical derivatization (OTCD) enables MSI to image molecules with poor ionization efficiently. In this technical report, several derivatization reagents and OTCD methods were evaluated using different MSI ionization techniques. Here, a method for detection and spatial distribution of vitamin D metabolites in murine kidney tissue sections using an OTCD–MALDI–MSI platform is presented. Moreover, the suitability of using the Bruker ImagePrep for OTCD-based platforms has been demonstrated. Importantly, this method opens the door for expanding the range of other poor ionizable molecules that can be studied by OTCD–MSI by adapting existing CD methods.

Spatial distribution of isobaric androgens in target tissues using chemical derivatization and MALDI-2 on a trapped ion mobility quadrupole time-of-flight instrument

“…Gir-T and dansyl hydrazine reagents were dissolved at 0.1 mg mL −1 in 90 : 10 : 0.1 (v/v/v) methanol : water : trifluoroacetic acid (TFA) (10 mL) and were introduced to the ImagePrep® device (Bruker Daltonik, Bremen GmbH & Co. KG). A custom-edited method was created on the ImagePrep operating system as previously described by Smith et al 17 One-step was programmed to run for approximately 1 hour to achieve reaction completion. Conditions were as follows; ‘matrix thickness’ was manual set to 40 cycles, spray power at 25% and a fixed spray time of 2.2 s. Incubation time was set at 30 s with a fixed drying time of 60 s, which led to a final OTCD time of approximately 60 min per slide and a reagent density of 0.05 mg cm −2 for GT and 0.06 mg cm −2 for DS.…”

On‐tissue chemical derivatization in mass spectrometry imaging

“…Wang et al, 2015). Recently, modified 3D printers have been developed for solvent/reagent deposition on tissues (Tucker et al, 2018;Smith et al, 2020). They are inexpensive compared to commercial systems while allowing a controlled spray with programmable parameters.…”

On‐tissue chemical derivatization reagents for matrix‐assisted laser desorption/ionization mass spectrometry imaging

“…70 It is studied not only in the context of vitamin-D deficiency but also as a potential treatment for cancer and mental disorders. 71 Vitamin D is first metabolized…”