Advances in CLARITY-based tissue clearing and imaging

CLARITY is a novel tissue clearing technique that transforms intact biological tissues into a nanoporous hydrogel-tissue hybrid, preserving anatomical structures, proteins and nucleic acids. The hydrogel-based structure is transparent after the removal of lipids and permits several rounds of immunostaining and imaging. This technique provides an ideal way for researchers to examine the central nervous system (i.e., mouse brain and spinal cord) intact. CLARITY was selected as one of ten breakthroughs in 2013 by Science. However, the original CLARITY technique still has severe technical limitations which impede its application in wider fields. Therefore, many modified clearing methods based on CLARITY have emerged. As all CLARITY-based tissue clearing techniques involve similar procedures, the present review attempted to divide these methods into individual procedures in order to provide new ways to test and combine tissue clearing methods. Furthermore, the combination of clearing methods could help to determine the optimal method for clearing and imaging large samples.