Tissue clearing and its applications in human tissues: A review

In three-dimensional (3D) space, an unbiased and systemic view of human specimens between structures and functions is required. However, conventional histological sections from specimens have made only limited progress in exploring intact information about 3D biological tissues. With significant advances in optical physics and chemical engineering, state-of-the-art tissue-clearing methods can revolutionize the intact subcellular level of human tissue histological analysis, from thick human tissues to intact human organs. The present review summarizes the principle of tissue clearing so that a trainee researcher can implement effective human tissue-clearing protocols. Furthermore, this review highlights existing tissue-clearing methods in specific human tissue applications, describes imaging strategies, and presents various efficient computational approaches for processing and visualizing large image data. Finally, potential future directions for developing tissue-clearing methods for human tissues are also discussed.