Three-dimensional analysis revealed that microglia have different structural features in different brain regions of mice

Microglia are immune cells of the central nervous system, and can constantly monitor the changes in surrounding environment by extending or retracting their ramified processes. To investigate the differences in morphological features of microglia in different brain regions, brain slices of transgenic mice expressing green fluorescent protein (GFP) were prepared and the structure of microglia in the cortex, striatum and polymorph layer of the dentate gyrus (PoDG) were imaged and quantified by combining techniques of tissue clearing, laser scanning confocal microscopy and three-dimensional reconstruction. The individual microglia with complex ramified processes was segmented based on the fact that microglial processes are extended from the cell body and have three-dimensional continuity. The results revealed that the occupied volume of a microglia in the striatum was significantly higher than that in the cortex or PoDG, but there was no significant difference in the occupied volume between the cortex and PoDG. The results of three-dimensional analysis indicated that the total length, the total number, the number of branching points, the total number of endpoints, and the maximum branching level of the microglial processes were significantly different between the cortex, striatum and PoDG. The tissue clearing technique combined with three-dimensional reconstruction can be used to analyze the features of microglial structures from multiple perspectives, and provide a novel approach for further analysis of the relationship between microglial structures and functions and their changes under different pathological conditions.