Using microscopy to understand mechanisms of action of toxic substances

The successful development of alternative methods to animal testing requires working with the latest technology. The BioImagingCenter of the Bf3R has a number of state-of-the-art microscopes at its disposal to understand mechanisms of action of toxic substances and to develop alternative methods.

According to the specific questions of different projects for the development of alternative methods, researchers of the Bf(3)R can choose among wide-field, confocal, multiphoton or super-resolution microscopy systems, which allow the visualization of single cells up to entire model organisms. The PALM/STORM imaging technology, which was awarded the Nobel Prize in Chemistry in 2014, can be used, for example, to resolve cellular structures in the nanometer range, and thus allows investigating a possible influence of environmental chemicals and pesticides on important (patho-) physiological processes, e.g. the development of cancer.

A particular strength of many alternative methods is their ability to efficiently investigate effects that could be caused by a combination of different chemicals and pesticides. For this reason, the BioImagingCenter is additionally equipped with an automated high-content, high-throughput screening system that allows cell-based testing of a large number of toxicologically relevant substances both individually and in combination. This screening system is also used for the development and validation of cell-based screening methods in order to assess their potential as predictive test methods based on extensive data sets, as well as for the development of organoids, and development and validation of model organism-based test methods (C. elegans).

Screeningsystem and laser scanning microscope of the BioImagingCenter. The High-Content High-Throughput Screening System is equipped with a pipetting robot (top left and right), a plate washer (bottom left), a spinning-disc confocal microscope, and a multimodal plate reader. Using a confocal microscope with FLIM / FCS upgrade (bottom right), the dynamics of cellular structures and molecules can be studied with high resolution.

Instrumentation/ Equipment

The following microscopes and accessories are available at the Bf3R:

• Wide-field fluorescence microscope with structured illumination for improved axial resolution and contrast in living or fixed samples
• Confocal laser scanning microscope with FLIM / FCS upgrade and spectral detector for imaging of fluorescently labeled living or fixed specimens; equipped with an area detector for improved spatial resolution (axial and lateral) and increased sensitivity  
• Wide-field fluorescence microscope suitable for high-resolution microscopy techniques PALM/STORM and SIM, which allows imaging of structures below the optical resolution limit
• Upright confocal multiphoton microscope for thick as well as sensitive (living) samples, enabling imaging of fluorescence signals up to 1 mm into the specimen
• Spinning-Disc High-Content Screening System for automated confocal fluorescence imaging in multiwell format (also in 3D)
• Automated robotics-based high throughput screening platform with integrated plate washer, liquid handling workstation, multimodal plate reader, incubator and confocal microscope
• Upright wide-field fluorescence microscope for morphological and stereological analysis of  cells and biological structure regarding e.g. number, length, area and volume

For analysis and evaluation of microscopic image data, the BfR uses commercial or open source software and individually created analysis pipelines. In addition, open source in-house software is developed at the German Center for the Protection of Laboratory Animals, ranging from simple image analysis to machine learning algorithms and modern deep learning methods.