Understanding the structure-function relationships at cellular, circuit, and organ-wide
scale requires 3D anatomical and phenotypical maps, currently unavailable for many
organs across species. At the root of this knowledge gap is the absence of a method
that enables whole-organ imaging. Herein, we present techniques for tissue clearing
in which whole organs and bodies are rendered macromolecule-permeable and optically
transparent, thereby exposing their cellular structure with intact connectivity. We
describe PACT (passive clarity technique), a protocol for passive tissue clearing
and immunostaining of intact organs; RIMS (refractive index matching solution), a
mounting media for imaging thick tissue; and PARS (perfusion-assisted agent release
in situ), a method for whole-body clearing and immunolabeling. We show that in rodents
PACT, RIMS, and PARS are compatible with endogenous-fluorescence, immunohistochemistry,
RNA single-molecule FISH, long-term storage, and microscopy with cellular and subcellular
resolution. These methods are applicable for high-resolution, high-content mapping
and phenotyping of normal and pathological elements within intact organs and bodies.
Copyright © 2014 Elsevier Inc. All rights reserved.