Cord Blood Processing
When cord blood of your baby arrives at the storage facility, it is tested to make sure it does not carry any infectious or genetic diseases, like hepatitis, HIV/AIDS, leukemia, or an immune disorder. If there are any problems with the blood, it may not be stored and rejected immediately. However, in some special cases, the blood may still be stored with the associated risks noted. If in the future the blood is needed, parents can assess whether or not the need for the blood stem cells outweigh the associated risks of the blood.
When the blood is transported to the laboratory, the team of skilled lab technicians works to prepare the cells for storage at extremely low temperature (from-180°C to -195°C). They remove the red blood cells and plasma because these aren’t required at the transplantation time. After this an agent called Cryoprotectant is added to the blood that protects cells from damage during freezing and storing.
Blood that will be stored goes through a series of processing before being banked. First, the blood is divided into its parts either through a centrifuge (an apparatus that spins the container of blood until the blood is divided) or by sedimentation (the process of injecting sediment into the container of blood causing the blood to separate).
Once the blood is divided with the red blood cells (RBC) on the bottom, white blood cells (WBC) in the middle and plasma on top, the white blood cells will be removed for storage. It is the middle layer, also known as the “buffy coat” that contains the stem cells; the other parts of the blood are not needed. Some banks, this will be the extent of their processing.
Other banks will go on to process the buffy coat further by removing the mononuclear cells from the WBC. While not everyone agrees with this method, since very little of the mononuclear cells are actually stem cells, it does result in having less to store. It also means that less cryogenic nitrogen needs to be used on the cells.
A few private cord blood banks freeze the blood whole, while most process it. There are two stages of processing: Volume Reduction and Separation.
Volume Reduction can be accomplished either by sedimentation or spinning in a centrifuge . Afterwards, the blood components are separated so that: red cells are on the bottom, plasma (a clear white liquid) is on top, and in the middle is a pinkish layer name the “buffy coat” which contains the white blood cells (WBC), including stem cells. At this point, a gentle spin in a centrifuge is sufficient to isolate the white blood cells (WBC). Most public banks stop processing at this point and store the WBC in bags.
Separation of mononuclear cells is accomplished by further centrifuge spinning of the white cells. One procedure for doing this is called “Ficoll-Hypaque” density gradient centrifuge, which is routinely used by stem cell researchers. The separation step reduces the volume of the collection to only a few milliLiters, which makes storage in vials feasible.
MonoNuclear Cells: Hematopoietic stem cells are identified with a characteristic surface molecule called “CD34+”, but only 1-2% of the MNC are actually stem cells. It is interesting to know that when parents store cord blood in any bank, they generally receive a follow-up lab report saying that so many billions of cells were stored; the lab is actually counting MNC, not stem cells. This is the standard medical procedure.
Let’s try to sum up everything. Processing of cord blood is performed as soon as possible but no later than 48 hours after collection. Processing involves three major steps:
- Removal of red cells
- Volume reduction of White Cell Concentrate
- Freezing and storing
Cord Blood and Maternal Blood Testing: Each sample of maternal blood matching collected cord blood is tested against the panel of recommended tests. The Positive results of these tests may disqualify the cord blood from being used in the future.
But, the next important question comes, are stem cells are lost during processing? Whatever care is taken, it is inevitable that some stem cells will be lost in the process of skimming off the buffy coat or separating the MNC. It is most debatable topic when it comes to specify what fraction of the stem cells is lost. Everybody likes to claim that their method of processing is better because they lose fewer cells.
But studies in the medical literature do not even find a significant difference between the viability of processed versus unprocessed cord blood. There is a large uncertainty, about 20%, in measuring the recovery of viable stem cells, and this uncertainty exceeds the difference between one processing method versus another.
Please note that the transportation of your baby’s umbilical cord blood to the processing and storage facility is a vital step of the process. Due to time and temperature sensitivity, it is vital that a medical courier (who understands the need to preserve the integrity of your shipment and protects the collection from extreme temperatures) ships the cord blood.
cord blood processing video