Tissue Section Imaging

Importance

Tissue section imaging is a vital step in advancing scientific understanding across many disciplines. It is effective for detailed ex vivo identification of targeting agent locations within an organ, such as the cellular localization of mRNA, RNA, or any protein of interest.

Two main applications are targeted therapeutics development and optical probe development. For targeted therapeutics development, tissue section imaging can determine the presence or absence of diseased tissue, such as cancer. It also aids in understanding a probe or therapeutic agent’s efficacy, toxicity, specificity, and biodistribution. For optical probe development, it is useful in assessing the biological performance of a given molecular probe. In both types of studies, tissue section imaging can help researchers histologically profile disease pathology.

Process Overview

In the near-infrared (NIR) tissue section imaging process, an optical probe or therapeutic agent is first developed and introduced into an animal. A tissue or organ is excised, preserved, sectioned, and mounted onto slides. Proteins or other targets of interest—such as mRNA, RNA, and DNA—can then either be directly detected by the injected labeled agent or with the aid of dye-labeled antibodies or optical probes. Finally, tissues and whole organs are imaged ex vivo using an NIR imager like the Odyssey® CLx Infrared Imaging System.

For more detailed steps, check out the Tissue Section Imaging Guide.

Optical Probe Development

Tissue section imaging is an important step in optical probe development because it helps verify if the given probe has reached its intended destination within the tissue. To begin, a dye such as IRDye® Infrared Fluorescent Dye is conjugated to a molecule, forming a molecular probe. The probe is then introduced into an animal. Because the dye allows the probe’s movement to be tracked, the probe’s activity can be recorded in vivo. Finally, tissue section imaging verifies the optical probe’s location ex vivo.

Learn how to design and validate your own optical probe with the Optical Probe Development page.

Targeted Therapeutics Development

Likewise, tissue section imaging is vital in the development of targeted therapeutics. A therapeutic agent is a specific molecule that can be used in various disease models; for instance, it is often used for cancer therapy because it can be designed to act on a cancer-associated target.

Check out the Targeted Therapeutics Development for further information.

In targeted therapeutics development, tissue section imaging differs from optical probe development in significant ways. Instead of simply determining whether the therapeutic agent has reached the desired destination, it seeks to determine its efficacy, toxicity, or specificity upon arrival. Additionally, the therapeutic agent is typically identified by staining the tissue rather than detecting a molecule that is conjugated to an NIR fluorescent dye.

You can advance your targeted therapeutics development with DigiWest® Protein Profiling Services, offered through a partnership between LI-COR and NMI TT Pharmaservices. DigiWest Protein Profiling Services offers a library of over 1,200 prevalidated antibodies and 50+ predefined pathways. Importantly, DigiWest technology may be used to perform protein profiling of frozen or formalin-fixed paraffin-embedded (FFPE) tissue or laser-capture-microdissected material from cryosections—using as little as 10 mg starting material or 20-60 μg of total proteins for the analysis of 80-800 protein targets.1 DigiWest Protein Profiling Services can consequently help narrow down the most promising targets or pathways for your therapeutic agent and lead to insight on how it works.

Validation

Once your optical probe or therapeutic agent has reached its destination, the tissue section is ready to be excised, sectioned, and—if necessary—stained before imaging.

The Odyssey CLx can help validate your probes or targeted therapeutics with high quality in vitro or ex vivo imaging. It can measure uptake, localization, and biodistribution within the tissue section or organ. For example, a study by Kearn, C.S., used an Odyssey imaging system to determine receptor expression and co-localization in a mouse brain to better understand Huntington’s disease markers (Fig. 1).

figure 1
Figure 1. Mapping of G protein-coupled receptors (GPCRs) in mouse brain using fluorescence immunohistochemistry (IHC) detection. Overlaid images of sagittal sections of mouse brain show a potential dual-expression pattern of the GPCRs cannabinoid CB1 (red) and dopamine D2 (green). Images were acquired on an Odyssey Imager at 21 µm resolution. Reprinted with permission from Kearn, CS.2

In another study by Pelekanos, M., et al., the Odyssey CLx assessed Evans blue uptake into a sheep brain to better understand how therapeutic ultrasounds may achieve transient blood-brain barrier opening in large animal models (Fig. 2).

figure 2
Figure 2. Histological staining to visualize the blood-brain barrier opening in sheep brain. Tissue sections of sheep brain were stained with Evans blue dye to visualize the transient opening of the blood-brain barrier. The heat map coloration of images acquired at 700 nm on an Odyssey CLx demonstrates the presence of Evans blue. Reprinted with permission from Pelekanos, M., et al.2.3

Summary

Overall, targeted therapeutics development and optical probe development are primary applications for tissue section imaging. Use tissue section imaging to help determine the presence or absence of diseased tissue in targeted therapeutics research, or assess a molecular probe’s biological performance. When looking to narrow down targets and pathways, DigiWest Protein Profiling Services is an ideal tool for both applications. Finally, characterize a therapeutic or optical probe with imagers like the Odyssey CLx for high quality in vitro and ex vivo images.

References

  1. Treindl, F., Ruprecht, B., Beiter, Y., Schultz, S., Döttinger, A., Staebler, A., Joos, T. O., Kling, S., Poetz, O., Fehm, T., Neubauer, H., Kuster, B., & Templin, M. F. (2016). A bead-based western for high-throughput cellular signal transduction analyses. Nature Communications, 7:12852.
  2. Kearn, C.S. (2004). Immunofluorescent mapping of cannibinoid CB1 and dopamine D2 receptors in the mouse brain. LI-COR Biosciences application note.
  3. Pelekanos, M., Leinenga, G., Odabaee, M., Odabaee, M., Saifzadeh, S., Steck, R., & Götz, J. (2018) Establishing sheep as an experimental species to validate ultrasound-mediated blood-brain barrier opening for potential therapeutic interventions. Theranostics, 8(9), 2583-2602.

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