Free of acrylamide sodium dodecyl sulphate (SDS)‐based tissue clearing (FASTClear): a novel protocol of tissue clearing for three‐dimensional visualization of human brain tissues

In recent years, advances in laser microscopy and endogenous fluorescent tagging techniques has led to the development of many tissue clearing strategies, which render tissues optically transparent, allowing large blocks of un-sectioned tissue to be visualised in three-dimensions (3D). CLARITY (Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging/Immunostaining/In situ hybridization-compatible Tissue-hYdrogel) is one of the tissue clearing techniques which works by fixation/hybridisation of brain tissue using hydrogel crosslinks and subsequent detergent-based delipidation to turn the tissue transparent [1]. Since CLARITY enables molecular probing using immunofluorescence, this technique was deemed suitable for post-mortem human brain tissues to demonstrate the potential in visualising pathologies in Alzheimer's [2], Parkinson's [3] and neurodevelopmental disorders [1,4] in 3D. Early attempts using CLARITY were performed on cortical tissue from the brains of children [1,4], which is considered to be less myelinated than adults, or on thinly sectioned tissues of up to 500 μm in thickness [1,2]. This article is protected by copyright. All rights reserved.