Optical clearing for multiscale biological tissues

Abstract

Three-dimensional reconstruction of tissue structures is essential for biomedical research. The development of light microscopes and various fluorescent labeling techniques provides powerful tools for this motivation. However, optical imaging depth suffers from strong light scattering due to inherent heterogeneity of biological tissues. Tissue optical clearing technology provides a distinct solution and permits us to image large volumes with high resolution. Until now, various clearing methods have been developed. In this study, from the perspective of the end users, we review in vitro tissue optical clearing techniques based on the sample features in terms of size and age, enumerate the methods suitable for immunostaining and lipophilic dyes and summarize the combinations with various imaging techniques. We hope this review will be helpful for researchers to choose the most suitable clearing method from a variety of protocols to meet their specific needs.

Hydrogen bound water profiles in the skin influenced by optical clearing molecular agents—Quantitative analysis using confocal Raman microscopy

“…In order to increase the probing depth, light‐focusing ability, spatial resolution of optical systems and image contrast, the optical clearing (OC) technique, allowing for control of tissue optical properties, has been proposed. Fundamentals and advances of OC technologies for in vitro and in vivo applications were recently reviewed in a number of publications . The influence of different OC agents (OCAs), for example, glycerol , glucose , dimethyl sulfoxide (DMSO) , scale , Sca/eS , PEG 400 and thiazone , was studied by various optical techniques such as OCT , MPT , RS , CRM and so on .…”

Optical clearing methods: An overview of the techniques used for the imaging of 3D spheroids

“…preserves the lipidic content of each sample, thus allowing the imaging of these structures using lipophilic tracer dyes (e.g., DiI and FM 1-43FX; Yu et al, 2018). preserves the lipidic content of each sample, thus allowing the imaging of these structures using lipophilic tracer dyes (e.g., DiI and FM 1-43FX; Yu et al, 2018).…”

“…Currently, the combination of the strengths of different methods has been supporting the development of procedures that allow to obtain better clearing and imaging without affecting the structure and the endogenous/exogenous fluorescence of the sample, as discussed by Yu et al (2018). Nevertheless, it is expected that future research will further result in increased clearing efficacies and improved imaging of thick samples.…”

“…The clearing methods were originally developed for processing large samples obtained from animals (e.g., bone, brain, embryo, heart, intestine, kidney, lung, muscle, pancreas, spinal cord, spleen, testis, among others), as already reviewed in detail in (Feuchtinger et al, 2016;Genina et al, 2010;Lee, Kim, & Sun, 2016;Richardson & Lichtman, 2015;Seo et al, 2016;Silvestri, Costantini, Sacconi, & Pavone, 2016;Susaki & Ueda, 2016;Tainaka, Kuno, Kubota, Murakami, & Ueda, 2016;Tuchin, 2015;Yu, Qi, Gong, Luo, & Zhu, 2018;Zhu, Larin, Luo, & Tuchin, 2013 (1.4-1.5; Figure 2; Ariel, 2017;Seo et al, 2016). Due to the osmotic pressure, the water content in the sample (that has low RI ≈ 1.33) will be passively replaced by the clearing solution.…”

Molecular mobility and activity in an intravital imaging setting – implications for cancer progression and targeting

“…Furthermore, new optical clearing techniques for large mammalian systems, such as Clarity, Scale, CUBIC (clear, unobstructed brain/body imaging cocktails and computational analysis), 3DISCO (3-dimensional imaging of solvent-cleared organs), SeeDB (see deep brain), ISDoT (in situ decellularization of tissues) or PACT (photoacoustic computed tomography), have improved the imaging resolution at depth by removing the cellular components of tissues that cause its opacity (Chung and Deisseroth, 2013;Fischer et al, 2017;Mayorca-Guiliani et al, 2017;Richardson and Lichtman, 2015;Tainaka et al, 2014;Tomer et al, 2014;Yu et al, 2017). Future combination of intravital studies with post-intravital optical clearing and subsequent high-resolution imaging, similar to CLEM, may provide new insight into disease aetiology and treatment.…”