Fluorescence activated cell sorting (FACS) as a separation method for neurofibrillary tangles in Alzheimer's disease

We have developed a fluorescence cell sorting (FACS) method for the separation of neurofibrillary tangles from post-mortem brain from cases of Alzheimer's disease and Down's syndrome. Neurofibrillary tangles in brain homogenate were selectively labelled with the fluorescent dye congo red. Using FACS the tangles were separated from other tissue components on the basis of fluorescence and forward-angle light scatter to give a fraction highly enriched in tangles, which were identified by light and crossed polarisation microscopy. Tangles were not observed in a comparison fraction, collected at the same time, of weakly fluorescent particles of similar size to the tangles. Thus FACS provides a non-denaturing method for obtaining preparations of neurofibrillary tangles for purposes of further analysis.