Editors' ChoiceImaging

Uncovering the Unseen

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Science Translational Medicine  19 Dec 2012:
Vol. 4, Issue 165, pp. 165ec229
DOI: 10.1126/scitranslmed.3005488

Human nature aims to explore; to make the unseen, seen. This is what drives the National Aeronautics and Space Administration’s rover—aptly named “Curiosity”—to send detailed pictures of Mars, which is large, but so far away. Similarly, scientists are interested in the small, yet close and unseen. To this end, molecular imaging has become more and more sophisticated. Nevertheless, visualization of biological processes within whole tissues is still limited by current technologies. Brede et al. now propose multicolor “light sheet” fluorescence microscopy as a new technique for imaging large intact animal and human tissues.

Brede and colleagues injected specific fluorochrome-labeled antibodies intravenously into mice or applied to tissue samples ex vivo. Tissues such as heart, testicle, skin, and lymph nodes were then illuminated with three different laser wavelengths set up on a commercial inverted microscope, and the resulting multicolor fluorescence was detected in image stacks. This imaging procedure allowed for an accurate three-dimensional computational tissue reconstruction. Bleaching and peroxidase-treatment protocols were applied to circumvent fluorescence interaction of hemoglobin or within optically dense organs. With this technology, Brede et al. were able to identify the nature, migration, and dispersal of immune cells over time within organs and tissues of interest (such as small intestine, tonsils, and lymph nodes). This microscopy-based cell-tracking approach was also demonstrated in a mouse model of graft-versus-host disease, in which the authors studied the time course and extent of T cell interaction with high endothelial venules. Furthermore, the technique allowed for the identification of rare events, such as homing of T cell subsets to Peyer’s patches at micrometer resolution within large tissue samples.

The technique demonstrated by Brede and colleagues will enhance our understanding of cell-cell interactions within tissues in vivo. More work needs to be addressed to overcome current limitations of this novel technique, such as reducing background autofluorescence and enhancing protein stability. Nevertheless, with the help of myriad antibodies available today and this imaging approach, more precise cellular therapies could be developed for diseases of the immune system and other malignancies.

C. Brede et al., Mapping immune processes in intact tissues at cellular resolution. J Clin. Invest. 122, 4439–4446 (2012). [Abstract]

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