Advances in tissue optical clearing for 3D imaging in large animal.

Three-dimensional reconstruction of tissue architecture is crucial for biomedical research. Tissue optical clearing technology overcomes light scattering limitations in biological tissues, providing an essential tool for high-resolution three-dimensional imaging. Given the high degree of similarity between large model animals (e.g., pigs, non-human primates) and humans in terms of anatomical structure, physiologic function, and disease mechanisms, the application of this technology in these models holds significant value for biomedical research. While well-established tissue clearing protocols exist for tissue sections, whole organs, and even entire bodies in rodents, scaling up to large animal specimens presents substantial challenges due to dimensional effects and compositional variations. This review systematically examines the methodological translation from rodent to large animals, particularly on species-specific differences in brain architecture and parenchymal organ composition that critically impact clearing efficiency. We comprehensively summarize recent applications in large animals, focusing on representative areas including neural circuit mapping, sensory organ imaging, and other related research domains, while proposing optimization strategies to overcome cross-species compatibility barriers. We hope this review will serve as a valuable reference for advancing tissue optical clearing applications in large-animal biomedical research.