Traditional histology and microscope methods require slicing of tissue into thin sections in order to allow light to penetrate through samples. Sectioning can limit precise quantification of histological features (such as total cell populations and/or location of pathological markers) to an estimate based on sampling in ‘representative’ areas. Recent innovations in both tissue clearing methods and imaging technologies have allowed intact tissue to be labelled and imaged, obviating the need for physical sectioning and potentially enabling more accurate assessments of pathology.
The aim of this study was to develop a pipeline to label, image, and quantify neuropathological markers in intact mouse brain samples, for the purpose of later assessing the accuracy of intact tissue analysis relative to traditional methods of analysis. In particular, amyloid plaque pathology was assessed in a mouse model of Alzheimer’s Disease. Whole mouse brain hemispheres and 2 mm sections were processed using different tissue clearing (aqueous- and organic-solvent-based) and labeling (antibody and fluorescent dye) approaches. Plaque pathology was visualised in three-dimensions using a range of imaging modalities including light sheet (LISH) microscopy, confocal laser scanning microscopy (CLSM), and two-photon excitation (2PE) microscopy.
The results demonstrate the utility of different tissue clearing and labeling techniques in interrogating pathology in a three-dimensional context. Features such as plaque morphology, distribution, and quantity could be assessed. This pipeline method for intact tissue quantification will be further bench-marked against stereological analysis. If successful, this approach may be applied to provide a more accurate measurement of the efficacy of various neuroprotective interventions in mitigating Alzheimer’s disease.