Improvements of TArgeted multiplex mass spectrometry IMaging

Abstract

MALDI mass spectrometers have become popular tools for imaging histological sections. Currently this technology is primarily used for imaging naturally occurring molecules. Here we report on the improvement of TArgeted multiplex MS IMaging (TAMSIM) technology. For TAMSIM we attach photocleavable mass tags to antibodies. Staining histological sections is done analogously to standard immunohistochemical procedures with chemiluminescent or fluorescent detection with the sole difference that multiple antibodies each with a distinct mass tag are used in a single reaction. Mass tags are released from their respective antibodies by a laser pulse at 355 nm without added matrix. After scanning, MS images are created for each tag mass. The enhancements of TAMSIM presented here relate to four elements, the use of an improved generation of tags, their conjugation directly to primary antibodies, the comparison of fresh frozen sections with paraffin embedded ones for the TAMSIM imaging technology and finally, the increase of multiplex detection. Sections of healthy human pancreatic tissue were imaged to visualize different specific biomarkers (synaptophysin, chromogranin, insulin, calcitonin, somatostatin) in neuroendocrine cells of Langerhans islets. The aim was to localize these biomarkers on the tissue sections simultaneously.

MALDI imaging mass spectrometry for direct tissue analysis: technological advancements and recent applications

“…The released tag can even be detected without the use of a matrix, which leads to an easier sample preparation and a better signal-to-noise ratio. Histochem Cell Biol (2011) 136:227-244 235 This, in addition to the fact that there is no signal quenching between different tags, as is the case for fluorescence tags, allows simultaneous detection of multiple molecules at femtomole levels (Lemaire et al 2007c;Thiery et al 2008). Furthermore, TAMSIM can be easily combined with other methods of analysis, such as immunohistochemistry, due to the minor alterations of the tissue that occur during the preparation and works on tissues independent of the fixation method used (Cazares et al 2011).…”

“…To this end, a molecular tag with a known mass is attached to a probe (e.g., an oligonucleotide or an antibody) by a photo-cleavable linker. During the MALDI measurement, the linker is exposed to the UV laser used for ionization and thus cleaved, releasing the tag, which can then be measured (Lemaire et al 2007c;Stauber et al 2010a;Thiery et al 2008). The released tag can even be detected without the use of a matrix, which leads to an easier sample preparation and a better signal-to-noise ratio.…”

Imaging mass spectrometry of thin tissue sections: A decade of collective efforts

“…Such samples, especially those with a fully annotated medical history, are invaluable for biomarker validation or discovery. Other more targeted in situ chemistries designed for the imaging MS of specific endogenous or administered compounds are also being developed [111][112][113].…”

Probe-based chemical modulations of tissues for IMS

“…Targeted specific multiplex imaging mass spectrometry is a powerful approach to obtain co-localization maps of proteins, peptides, or drugs and could potentially be used for diagnostic purposes [24][25][26]. TAMSIM was first introduced by Thiery et al, in 2007, with the aim of detecting and visualizing simultaneously two cancer biomarkers, PS100 and HMB45, in tissue sections from a human lymph node and liver invaded by metastatic melanoma.…”