Fiducial Markers for Combined 3-Dimensional Mass Spectrometric and Optical Tissue Imaging

Abstract

Mass Spectrometric Imaging (MSI) has become widely used in the analysis of a variety of biological surfaces. Biological samples are spatially, morphologically, and metabolically complex. Multimodal molecular imaging is an emerging approach that is capable of dealing with this complexity. In a multimodal approach, different imaging modalities can provide precise information about the local molecular composition of the surfaces. Images obtained by MSI can be co-registered with images obtained by other molecular imaging techniques such as microscopic images of fluorescent protein expression or histologically stained sections. In order to properly co-register images from different modalities, each tissue section must contain points of reference, which are visible in all data sets. Here, we report a newly developed co-registration technique using fiducial markers such as cresyl violet, Ponceau S, and bromophenol blue that possess a combination of optical and molecular properties that result in a clear mass spectrometric signature. We describe these fiducial markers and demonstrate an application that allows accurate co-registration and 3-dimensional reconstruction of serial histological and fluorescent microscopic images with MSI images of thin tissue sections from a breast tumor model.

Imaging mass spectrometry to visualize biomolecule distributions in mouse brain tissue following hemispheric cortical spreading depression

“…Andersson et al have published an experimental workflow [30], and alignment procedures have been reported to combine 3D imaging MS with 3D magnetic resonance imaging [31] and 3D optical imaging techniques [40]. These studies have focused on reproducing the histo-architectures of the tissues, such as mouse or crustacean brain architecture [30,38,41] and localizing tumors [31].…”

Mass spectrometry images acylcarnitines, phosphatidylcholines, and sphingomyelin in MDA-MB-231 breast tumor models

“…Tissue sections were stained using a modifi ed H and E staining protocol as previously described (43)(44)(45). Briefl y, 10 µm sections attached to Superfrost Slides (VWR International, Cat.…”

“…MSI employing MAL-DI-MSI visualized the distribution of intact phospholipid molecular ions. All modalities were combined through the presence of fi ducial markers visible in all imaging modalities ( 45 ). Figure 1 presents results obtained from a representative breast tumor xenograft using our multimodal imaging approach.…”

Mass Spectrometric Imaging of Red Fluorescent Protein in Breast Tumor Xenografts

“…When tumors reached a volume of approximately 500-mm 3 , mice were sacrificed and tumors were removed. Each tumor was embedded into a gelatin block prepared using 15-mm×l5-mm×5-mm cryomolds (Sakura Finetek, Torrance, CA, USA), 10 % gelatin, cooled to 30 °C in order to prevent tissue degradation, and three cresyl violet fiducial markers, which were injected inside the gelatin block next to the tumor as previously described [12-14]. This block was sectioned into serial 2-mm thick fresh tumor sections using an acrylic adjustable tissue slicer (12-mm depth up to 25-mm width; Braintree Scientific, Inc., Braintree, MA, USA) and tissue slicer blades (Braintree Scientific, Inc.).…”