Based on existing tissue clearing technology, an optimized three-dimensional (3D) tissue-staining and observation technique based has been established by a RIKEN research team. The study, published in the journal Nature Communications, details how the new technique can be used to stain tissue and label cells in whole marmoset bodies, human brains, and mouse brains. Detailed anatomical analysis and whole-organ comparisons between species at the cellular level can be achieved through this technique.
3D observation of organs using an optical microscope can be obtained by tissue clearing. In Japan, at the RIKEN Center for Biosystems Dynamics Research (BDR), a research team led by Etsuo Susaki and Hiroki Ueda developed CUBIC, a 3D tissue clearing technology which can image the whole body at the single-cell level by making tissue transparent, in 2014.
Tissue clearing by itself does not have much scientific value though it can result in fantastical images. Scientists should be able to stain and label specific cell types and cells, which then can be studied, in order for tissue clearing to be meaningful. A system capable of working with a wide range of antibodies and staining agents is required for this. None of the 3D staining and labeling methods have been versatile enough although there are several types of them been attempted.
Detailed physical and chemical analyses were performed by the team at BDR and their colleagues after realizing that they needed a better understanding of body tissue. It was found that biological tissues can be described as a type of electrolyte gel.
Using artificial gels that can mimic biological tissues, they constructed a screening system to examine a series of conditions, based on the tissue properties they discovered. They were able to establish CUBIC-HistoVIsion, a fine-tuned, versatile 3D-staining/imaging method, by analyzing the staining and antibody labeling of artificial gels with CUBIC. They were successful in staining and imaging a square centimeter of human brain tissue, half a marmoset brain, and the whole brain of a mouse, and whole-body 3D imaging of an infant marmoset, using this optimized system with high-speed 3D microscopic imaging.
From studying the brain to studying kidney function, scientists can use this in many fields, as the system worked well with about 30 different antibodies and nuclear staining agents. One of the many purposes that the system can be used for is to compare whole-organ anatomical features among species.
In the brains of mice and marmosets, the overall distribution patterns of blood vessels seemed likely evolutionarily preserved as CUBIC-HistonVIsion revealed that the patterns are very similar. They also found that between humans, mice, and marmosets, the glia-cell distribution in the brain’s cerebellum differed.
Susaki says, “At present, the 3D staining method developed in our study is the best method in the world as it surpasses the performance of the typical staining methods published so far. Also, in the development of methods in tissue chemistry, such as constructing staining protocols based on tissue properties, it provides a paradigm shift. These results are expected to improve the diagnostic accuracy and objectivity of 3D clinical pathology examination and to contribute to the understanding of biological systems at organ and organism scales.”