In general, the term viability is the capacity of something to be alive, to develop and reproduce. In biology cell viability count refers to the percentage of the cells in a population that are alive. Typically, when you have a tissue or cluster of cells, a fraction of the cells are naturally dying.
Why is a cell viability count important?
It is important because it generally acts as an indicator of the health of cells. There are many ways to measure the viability of a cell. You can measure metabolic activity. You can measure the ATP content. Or you can look at toxicity measures such as loss of membrane integrity.
The simplest method of obtaining a cell viability count is live/dead cell counting. The healthier the population of cells the more likely it is that they respond accurately to the test compounds and test conditions. Healthier cells will also be better at proliferating or growing, in the future.
What is Live/dead counting?
Live/dead counting is assessing the quantity of both live and dead cells in a sample population. A fluorescence-based assay is typically used. This is where we detect live cells by the conversion of a protein called Calcein-Am to Calcein. This is indicative of enzymatic activity. If a cell can do this conversion, it is enzymatically active and will fluoresce as green.
We detect dead cells by the intake of a red dye called propidium iodide (PI). The dye can only be taken in by a cell if the cell membrane integrity is lost. This means the cell has been damaged or the membrane has been damaged. This happens during the process of cell death known as apoptosis. A microscope or software then looks at the cells which are red and compares them to the cells that are green. The average number of live cells will be different for every cell and tissue type.
How does Acorn use cell viability?
At Acorn Biolabs we store hair follicle cells for future use. Thus cell viability is extremely important for us. We analyze a sample of the collected cells to make sure there are enough live cells before they are cryogenically frozen. Ensuring that cells have the capacity to grow and proliferate in the future when they are thawed. At the end of the day, it’s a numbers game. The more cells you have which are alive the better probability that the cells can be used in the future.