Stem cell Storage Methods
Stem cell storage is a very essential step for further experiments and research on stem cells.
As a parent, you might want to store the stem cells from the umbilical cord of your child for future use. These cells can prove to be a life saver, if your child develops diseases such as leukemia or sickle cell anaemia later in life.
Stem cell storage and transportation takes place in a cryopreserved state. In this state, they are frozen to -320 degrees Fahrenheit in a liquid nitrogen bath. However, the stem cells have a very low survival rate after undergoing this storage technique. Hardly 10% of the cells successfully “wake up” and resume their undifferentiated state. This state is essential for cells that can be used for further experimentation. Scientists have to try to generate new colonies of stem cells from the few survivors. Moreover, these surviving stem cells may become genetically altered due to natural selection. This is highly undesirable.
Liquid Phase Nitrogen: Stem cells are kept in a storage tank that is cooled by liquid nitrogen to about -190 degree Celsius. The stem cells can be preserved for a long period of time using this method… The method of storage using liquid nitrogen as the cooling agent is the oldest one. It should be remembered that there are samples of many stem cells belonging to different people kept together in one tank. Liquid nature of the nitrogen poses a risk of contamination of samples. Transfer of Hepatitis B virus between samples has been seen when infected and healthy samples were stored together in liquid nitrogen cryo tank.
Vapor Phase Nitrogen: This design also uses liquid nitrogen but only the vapor comes in contact with the sample. This minimizes any chance of cross contamination.
Stem cell storage using liquid nitrogen requires a lot of labor but still the results are not good. Therefore, scientists are looking for newer and more efficient ways for stem cell storage.
Instead of suspending the cells in a liquid medium, the cells are attached to a gel matrix. A disaccharide sugar known as trehalose is added to it. This sugar is produced by animals to protect their cells and survive in low temperatures. Almost 20% of the cells survive this process successfully which is a huge increase compared to the 10% rate obtained by liquid nitrogen. The chances of genetic variation and uncontrolled differentiation also decrease significantly.
Scientists are also trying to develop sub zero non- freezing methods for stem cell storage. It offers the advantage of keeping the cells in an unfrozen state without running the risk of ice crystal formation that takes place at sub zero temperatures. This method decreases the cell metabolism and prolongs the life of the cell.
The ultimate method that the researchers are trying to perfect for stem cell storage is the freeze drying method. Some bacterial cultures and blood products have been successfully freeze-dried. Efforts are on to extend this technology to stem cells also.
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