Human liver and pancreas innervation: resolving 3D neurohistological challenges and advancing insights

The human liver and pancreas are central to metabolic regulation, with the autonomic nervous system orchestrating processes that maintain glucose homeostasis and respond to dynamic physiological demands-ranging from acute energy mobilization during stress to postprandial glucose uptake and storage. However, visualizing and examining the intricate three-dimensional (3D) neural networks within clinical liver and pancreas specimens remains challenging, as conventional two-dimensional (2D) histological methods cannot fully resolve the spatial complexity of autonomic innervation in the liver and pancreas. This review identifies and discusses key biological and technical factors-including tissue autofluorescence, autolysis, photobleaching, and steatosis-that compromise the reliability of 3D neurohistological analysis of the human liver and pancreas. We also highlight emerging optical and chemical methodologies that enable high- and super-resolution 3D tissue imaging, improving signal fidelity, preserving structural detail, and supporting consistent, reproducible analysis. Ultimately, these advances aim to facilitate precise mapping of human liver and pancreas innervation, offering deeper insight into the neural regulation of nutrient assimilation, glucose utilization, and metabolic homeostasis in both physiological and pathological contexts.