High-Speed Clearing and High-Resolution Staining for Analysis of Various Markers for Neurons and Vessels.

Background: Tissue clearing enables deep imaging in various tissues by increasing the transparency of tissues, but there were limitations of immunostaining of the large-volume tissues such as the whole brain.

Methods: Here, we cleared and immune-stained whole mouse brain tissues using a novel clearing technique termed high-speed clearing and high-resolution staining (HCHS). We observed neural structures within the cleared brains using both a confocal microscope and a light-sheet fluorescence microscope (LSFM). The reconstructed 3D images were analyzed using a computational reconstruction algorithm.

Results: Various neural structures were well observed in three-dimensional (3D) images of the cleared brains from Gad-green fluorescent protein (GFP) mice and Thy 1-yellow fluorescent protein (YFP) mice. The intrinsic fluorescence signals of both transgenic mice were preserved after HCHS. In addition, large-scale 3D imaging of brains, immune-stained by the HCHS method using a mild detergent-based solution, allowed for the global topological analysis of several neuronal markers such as c-Fos, neuronal nuclear protein (NeuN), Microtubule-associated protein 2 (Map2), Tuj1, glial fibrillary acidic protein (GFAP), and tyrosine hydroxylase (TH) in various anatomical regions in the whole mouse brain tissues. Finally, through comparisons with various existing tissue clearing methodologies such as CUBIC, Visikol, and 3DISCO, it was confirmed that the HCHS methodology results in relatively less tissue deformation and higher fluorescence retention.

Conclusion: In conclusion, the development of 3D imaging based on novel tissue-clearing techniques (HCHS) will enable detailed spatial analysis of neural and vascular networks present within the brain.