Immuno Tomography (IT) and Imaging Mass Cytometry (IMC) for constructing spatially resolved, multiplexed 3D IMC data sets.

PURPOSE: We have previously used Immuno Tomography (IT) to identify label-retaining stem cell populations in the cornea and meibomian gland. While this method provides the unique ability to quantify stem cell populations comprised of 1-4 cells, the number of antigens that can be sequentially used to characterize these unique cells is limited by antigen stability after antibody stripping and re-probing. To address this deficiency, we have evaluated the capability of Imaging Mass Cytometry™ (IMC™) to generate multiplexed images using metal-conjugated antibodies to label IT plastic sections and generate 3-dimensional IMC data sets (3D IMC). METHODS: K5-H2B-GFP mice, 56 days after doxycycline chase, were sacrificed and eyelid tissue processed for IT. A total of 400 serial, plastic sections, 2 µm thick, were then probed using metal-tagged antibodies specific for sox 9, collagen type I, E-cadherin, Ki67, GFP, αSMA, vimentin, and DNA intercalator. Multiplexed images were then generated using an Imaging Mass Cytometry system (Fluidigm®), and 3D reconstructions were assembled. RESULTS: All 8 metal-labeled tags were detected and their images were successfully assembled into 3D IMC data sets. GFP-labeled nuclei were identified within the meibomian glands in comparable numbers to those previously reported for slow-cycling meibomian gland stem cells. CONCLUSIONS: These findings demonstrate that IMC can be used on plastic sections to generate multiplexed, 3D data sets that can be reconstructed to show the spatial localization of meibomian gland stem cells. We propose that 3D IMC might prove valuable in more fully characterizing stem cell populations in different tissues.

Immunophenotyping of Human Peripheral Blood Mononuclear Cells by Mass Cytometry.

Mass cytometry is a variation of conventional flow cytometry using metal tagged antibodies for cell staining instead of fluorochromes and detection in a mass cytometer, a modified mass spectrometer that allows for separation of discrete masses of these metal tags by time of flight (TOF). Currently, up to 50 different metal tags are available for cell analysis. The lack of any significant mass spectral overlap and autofluorescence background makes mass cytometry uniquely suited for complex high-dimensional phenotypic and functional analysis at the single cell level, thus accelerating biomarker discovery and drug screening. Here we describe a workflow for phenotyping of human peripheral blood mononuclear cells (PBMCs) covering cell staining, instrument setup of a Fluidigm Helios™ mass cytometer, and sample acquisition, and summarize a basic workflow of data analysis.