Optical Tissue Clearing: Illuminating Brain Function and Dysfunction

Abstract

Tissue optical clearing technology has been developing rapidly in the past decade due to advances in microscopy equipment and various labeling techniques. Consistent modification of primary methods for optical tissue transparency has allowed observation of the whole mouse body at single-cell resolution or thick tissue slices at the nanoscale level, with the final aim to make intact primate and human brains or thick human brain tissues optically transparent. Optical clearance combined with flexible large-volume tissue labeling technology can not only preserve the anatomical structure but also visualize multiple molecular information from intact samples in situ. It also provides a new strategy for studying complex tissues, which is of great significance for deciphering the functional structure of healthy brains and the mechanisms of neurological pathologies. In this review, we briefly introduce the existing optical clearing technology and discuss its application in deciphering connection and structure, brain development, and brain diseases. Besides, we discuss the standard computational analysis tools for large-scale imaging dataset processing and information extraction. In general, we hope that this review will provide a valuable reference for researchers who intend to use optical clearing technology in studying the brain.

Tissue Clearing and Its Application in the Musculoskeletal System

“…Additionally, in this method, the selected clearing agents must have the ability to dissolve the residual lipids in the delipidated tissue. Light scattering in tissues is primarily caused by lipids and hydrophobic clearing reagents have a higher RI (1.43∼1.47) than reagents used in other techniques, 51 resulting in a significant clearing effect in a relatively short amount of time with the hydrophobic method. Through the hydrophobic clearing method, water is removed from the sample, which is essential for maintaining the proteins fluorophores.…”

Obesity-Related Neuroinflammation: Magnetic Resonance and Microscopy Imaging of the Brain

“…These microscope developments have been complemented by substantive innovations in sample preparation, such as optical tissue clearing (OTC) [ 91 , 92 , 93 ]. OTC methods remove lipids (delipidation), pigments (decolorization), and calcium phosphate (decalcification), and they aim to match the refractive indices of the tissue sample and imaging media, reaching an almost complete level of transparency [ 91 ].…”

Volumetric refractive index measurement and quantitative density analysis of mouse brain tissue with sub-micrometer spatial resolution

“…Moreover, the combination of tissue-clearing techniques has been extended to volumetric fluorescence imaging (6,7). However, conventional fluorescence imaging approaches do not directly provide structural information; thus, high-resolution structural information is largely acquired using electron microscopy (EM) (8).…”

“…Recent advances in fluorescence microscopy have enabled sub-diffraction molecular-specific imaging of subcellular organelles and protein distribution (4, 5). Moreover, the combination of tissue-clearing techniques has been extended to volumetric fluorescence imaging (6, 7). However, conventional fluorescence imaging approaches do not directly provide structural information; thus, high-resolution structural information is largely acquired using electron microscopy (EM) (8).…”