Whole-brain 3D imaging of dopaminergic neurons and glial cells in the mouse model of Parkinson's disease induced by 6-OHDA.

OBJECTIVE: Parkinson's disease (PD) is the second most common neurodegenerative disease. Current understanding of the abnormal neural network in PD is limited, which may be one of the reasons for the lack of effective treatments. Tissue-clearing techniques allow visualization of neurons and gliocytes that form the structural basis of the abnormal neuronal network, thus enabling a deeper understanding of the pathological neuronal network in PD and contributing to the study of therapeutic strategies. The aim of this study was to create pathological maps of PD and perform 3D visualization of the neural network. METHODS: We induced the PD model using 6-OHDA and a predesigned rotation test. We then performed tissue-clearing and 3D imaging of the whole-brain and brain slices of the mice using SHIELD and CUBIC. RESULTS: The rotation test showed that the 6-OHDA group had a significant increase than the sham group. SHIELD results showed a significant reduction in tyrosine hydroxylase (TH) signals in the substantia nigra (SN) + ventral tegmental area (VTA) and caudate putamen (CPu) regions in the 6-OHDA group compared to the sham group. Additionally, we performed 3D imaging and reconstruction of astrocytes, microglia, dopaminergic neurons, and blood vessels in the SN + VTA to visualize the neuronal network. CONCLUSION: This study performed 3D imaging of the composition and spatial arrangement of neuronal vascular units at both macroscopic and microscopic levels, laying the foundation for the creation of a whole-brain pathological map of PD. It also provides a basis for exploring unknown neural circuits and visualizing them.