Storing Cord Blood
Once your cord blood has been collected, it may be out of sight, but it is unlikely to be out of mind. What happens to that blood when it arrives at the cord blood bank? And how are the stem cells retrieved from the sample? Read on to find out!
Arriving at Storage
To ensure that your baby’s blood and stem cells are healthy, cord blood services will test the sample. Some of these tests include hepatitis, HIV/AIDS, and leukemia. Unfortunately, if a problem with the blood is found, it may not be stored, particularly if it is donated cord blood. If you have chosen to go with private cord blood storage, you may be given the option to bank the blood with the associated risks noted. In future, if you do need to use the blood, you can consider whether the need for the stem cells outweigh the risks of using the blood.
After the blood has been tested, the process of separating the stem cells from the blood can begin. In order to divide the blood into red blood cells, white blood cells and plasma, the blood is put through a centrifuge or sedimentation is used. A centrifuge is a machine that spins a container of blood until the blood has separated. Sedimentation refers to sediment that is injected into a container of blood that causes the blood to separate.
Now that the blood is separated, the white blood cells (WBC), which contain the stem cells, will be sandwiched between the red blood cells (RBC) on the bottom and plasma on the top. This middle layer, also known as the "buffy coat," will be removed and sent for storage. The other layers are not needed. In fact, storing the stem cells with RBC may compromise the stem cells as RBCs can burst when they are thawed. Additionally, keeping the RBCs would mean that the recipient of the stem cells would need to be a blood match in addition to being an HLA match. By removing the RBCs, more people can benefit from the stem cell therapy with minimal consequences.
Some cord blood banks may choose to continue their processing by removing mononuclear cells from the buffy coat before sending the sample to storage. By removing these cells, which are mainly not stem cells, there is less that needs to be stored. This extra step is contended by some.
From processing, the stem cells are then ready to be preserved, or frozen, which must be done slowly so that the stem cells aren’t damaged. The first step in the freezing process is introducing the cord blood stem cells to a solution, known as the cryopreservation solvent or cryoprotectant. This solution helps to prevent a stem cell from being harmed while it is frozen.
Once the stem cells have received the cryoprotectant, they will be slowly frozen until they reach a freezing temperature of -196°C. It is important that the stem cells are frozen slowly so that they will not be damaged in the process. When the stem cells reach the appropriate temperature, they will be transferred to a more permanent home: a storage freezer. Here, stem cells will remain frozen through the use of either vapor or liquid nitrogen.
Stem Cells Preservation
While inside the freezer, cord blood cells are kept in either bags or vials. The majority of cord blood banks use just one storage method since the racks inside the freezers are capable of accommodating only one type of storage container. Although some cord blood banks do use both vials and bags to store their blood, they use separate freezers to accomplish this.
So, what types of freezers are used for stem cell preservation? The most common is the dewar. Because this freezer is simply a well-insulated container with a lid, there is a potential risk that blood samples could be compromised every time a sample needs to be put in or removed due to the lid being removed. To make sure stem cells are not compromised, dewars are vigorously maintained and monitored to ensure that the freezers retain a consistent temperature.
A newer, more advanced type of freezer is the BioArchive. In addition to freezing the blood, the BioArchive is also capable of inventorying and managing as many as 3,626 blood bags. Furthermore, this freezer has a robotic arm that will retrieve a particular blood sample when needed, thereby ensuring that the other samples are not disturbed.
How Long Will it Last?
A common question among those considering cord blood banking is: how long can my stem cells remain frozen for and still be viable? A conservative estimate puts the stem cell’s freezer life at 10 years. Other estimates suggest 15 years. Although stem cell research still needs to conclusively determine just how long stem cells can be viable, many scientists are anticipating that stem cells will be able to survive the freezer for as much as 20 years.