Analyzing COS1 Cells for Studying Alzheimer's Disease

Alzheimer’s disease is a common type of dementia that affects millions of people around the world. It is characterized by two pathological hallmarks in the brain, extracellular amyloid plaques, composed of amyloid-beta (Aβ) protein, and intracellular neurofibrillary tangles (NFTs), composed of tau protein. Dysfunction of Aβ and tau proteins can lead to neuronal cell death, which in turn can cause Alzheimer’s. This cell death assay is analyzed with COS1 cells (a cancerous African green monkey kidney cell line). These cells do not express tau and can easily propagate. Thus, COS1 cells, if transfected with tau, serve as a model system for studying the underlying molecular mechanisms of Alzheimer’s disease. The cell alive/death ratio is one of important measurements to analyze the function of Aβ and tau protein. Alive and dead cells can be discriminated by staining with bio-reactive molecules such as propidium iodide and calcein AM. However, the ratio is currently computed by manually counting live and death cells from micrographs. The main goal of the project is to develop an automatic method to count alive and dead cells from confocal microscope images. Cells are segmented by thresholding followed by morphological operations. The segmented cells are classified into two classes (normal and clustered cells) to exclude clustered cells for further segmentation. The classified normal cells are used to compute a cell density from the images of wild type untreated COS1 cells. The developed method approximates the cell density found by earlier study. The cell counts will be used to determine the alive/dead cell ratio under different experimental conditions, which will test the hypothesis that tau-transfected cells are more sensitive to amyloid-beta treatments than non-tau expressing cells.