Author Correction: Next generation histology methods for three-dimensional imaging of fresh and archival human brain tissues.

In the original version of this Article, the concentration of boric acid buffer for the SDS clearing solution was given incorrectly as '1 M sodium borate' and should have read '0.2 M boric acid'. Also, the composition of PBST incorrectly read '1% Triton X-100 (vol/vol) and 0.1% sodium azide (wt/vol)' and should have read '0.1% Triton X-100 (vol/vol) and 0.01% sodium azide (wt/vol)'. Further, the pH of the OPTIClear solution was not stated, and should have read 'with a pH between 7 to 8 adjusted with hydrochloric acid'. These errors have been corrected in both the PDF and HTML versions of the Article.

Next generation histology methods for three-dimensional imaging of fresh and archival human brain tissues.

Modern clearing techniques for the three-dimensional (3D) visualisation of neural tissue microstructure have been very effective when used on rodent brain but very few studies have utilised them on human brain material, mainly due to the inherent difficulties in processing post-mortem tissue. Here we develop a tissue clearing solution, OPTIClear, optimised for fresh and archival human brain tissue, including formalin-fixed paraffin-embedded material. In light of practical challenges with immunostaining in tissue clearing, we adapt the use of cresyl violet for visualisation of neurons in cleared tissue, with the potential for 3D quantification in regions of interest. Furthermore, we use lipophilic tracers for tracing of neuronal processes in post-mortem tissue, enabling the study of the morphology of human dendritic spines in 3D. The development of these different strategies for human tissue clearing has wide applicability and, we hope, will provide a baseline for further technique development.

Rationalisation and Validation of an Acrylamide-Free Procedure in Three-Dimensional Histological Imaging.

Three-dimensional visualization of intact tissues is now being achieved by turning tissues transparent. CLARITY is a unique tissue clearing technique, which features the use of detergents to remove lipids from fixed tissues to achieve optical transparency. To preserve tissue integrity, an acrylamide-based hydrogel has been proposed to embed the tissue. In this study, we examined the rationale behind the use of acrylamide in CLARITY, and presented evidence to suggest that the omission of acrylamide-hydrogel embedding in CLARITY does not alter the preservation of tissue morphology and molecular information in fixed tissues. We therefore propose a novel and simplified workflow for formaldehyde-fixed tissue clearing, which will facilitate the laboratory implementation of this technique. Furthermore, we have investigated the basic tissue clearing process in detail and have highlighted some areas for targeted improvement of technologies essential for the emerging subject of three-dimensional histology.