Find out more about why it is best to store cord blood using the volume reduction method

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Why do we choose to store volume reduced blood instead of whole blood?

The first reason is that it’s the industry standard in the UK, and globally. Both the NHS Cord Blood Bank and the Anthony Nolan Trust store volume reduced samples, as do the majority of public and private banks around the world. Smart Cells use processing technologies similar to those employed by many public banks. Volume reduction prior to freezing using the methodology we use, specifically preserves the all-important stem cells.


The second reason is that it’s safer. The freezing process used to preserve the stem cells in the sample damages the red blood cells, which means there’s a lot of debris and free haemoglobin in the sample when it’s thawed. In turn this can result in post-transplant complications. The volume reduction method reduces the red blood cell content.

The reason why red blood cells are dangerous to patients is that they tend not to survive the freezing and thawing process. Red blood cells undergo “lysis” during cryopreservation, a rupture of the cell membrane that spills the cell’s contents, which include the haemoglobin and empty membrane sacks called red cell ”ghosts”. These lysed red cell elements can cause complications for patients including kidney, cardiac and respiratory problems at the time of transplant.

As the volume reduced method reduces the red blood cell content, this has the added benefit of minimizing reactions in the patient due to blood type incompatibility if the sample is being used for a brother or a sister.

Volume reduced blood v’s whole blood
Volume Reduced BloodAn example of a sample being processed using our volume reduction method

What do the experts think?

“Our processing depletes red cells (not totally though) and plasma to retain the so called “buffy coat” fraction that is rich in mononuclear cells. This means we are retaining the critical cells with proliferative capacity.

It is misleading for a whole blood storage company to say that the volume reduced method will only ever be useful in the treatment of haematological conditions. The volume reduced sample is just as likely to be useful in regenerative medicine in the future as whole blood. However when it comes to clinical use, red cell depleted products are acknowledged widely to be preferable thus the volume reduced method has the advantage.

The assertion by whole blood companies that volume is the critical factor is irrelevant – it is the progenitor/stem cell count that matters. For example, sometimes transplants in adults take place with single volume reduced cord blood units because the cell count is high enough. If it is not sufficient, two units can be used – this is not volume dependant. Volume reduced cord blood is used clinically to regenerate an entire haematopoietic system in individuals who have had high dose chemotherapy and also possibly total body irradiation so the product has to work or the results are catastrophic. Furthermore, when thinking about future innovative therapies such as regenerative medicine – for example in the treatment of stroke, cardiac disease or cerebral palsy– as yet we cannot be sure what doses of product will be optimal”

Dr. Ann Smith - Smart Cells Scientific Director

Dr. Ann Smith - Smart Cells Scientific Director

“Cord blood units that have not had their red cells removed are more difficult to use for patients. When the frozen unit is thawed, the red cells undergo lysis and break apart. The medical literature reports serious and life-threatening reactions when these products are infused without any dilution or wash. The current recommendation from the National Marrow Donor Program (Be The Match) is NOT to infuse units holding red cells as they are, but to wash or at least dilute them.

Washing cord blood units that hold red cells after they have been thawed is technically challenging. The free hemoglobin and the cellular debris released from the lysed (broken) red cells makes it difficult for laboratory scientists to see the demarcation between the nucleated stem cells that they want to keep versus the residual “supernatant” to be removed. The separation of different cell types becomes more difficult than it was in the pre-freezing cord blood unit, leading to some loss of desirable cells. In addition, post-thaw tests of cord blood potency with the Colony-Forming-Unit (CFU) assay may be difficult to interpret.

In summary, given the problems with handling cord blood units that hold red cells, both in the laboratory and in the patient care setting, the current industry standard is for most cord blood banks to perform partial depletion of RBC and removal of plasma before cryopreservation. In addition, those public cord blood banks that have been licensed by the FDA all use a system to deplete RBCs and plasma.”

Andromachi Scaradavou MD - Medical Director of the New York Blood Center's National Cord Blood Program

Andromachi Scaradavou MD - Medical Director of the New York Blood Center's National Cord Blood Program

Why store volume reduced?

Volume reduced blood v’s whole blood

Concentrated sample improves quality

Plasma contains proteins, but no stem cells, so it is not needed for transplant therapy. Plasma removed during volume reduction(1)

Lower risk of infusion reactions for patient

Red blood cells tend not to survive the freezing and thawing process. They are not believed to help during transplant, so they are not needed either(2)

Contains growth factors vital for regenerative medicine

Contains cells that may be useful in future regenerative medicine such as VSEL cells, MSC’s and HSC’s

Fewer complications for patients during a transplant

Less red cell debris which minimises incompatibilities when stem cells are being used for a sibling

References: (1) (2) parentsguidecordblood.org – Andromachi Scaradavov, MD – Medical Director of the New York Blood Center’s National Cord Blood Program

“Cryopreservation of ‘whole blood’ refers to freezing and storing the cord blood unit without removing any red blood cells or plasma. Red blood cells have been associated with harmful or fatal side effects if too many of them are used in a transplant (FACT Spring 2013). This means that some of the red blood cells need to be removed from the unit before it can be used in a transplant, and this can be done before or after cryopreservation. ‘Red cell depletion’ (also called ‘red cell reduction’) refers to the removal of most of the red blood cells before cryopreserving the cord blood unit. Units stored without red cell depletion must be washed after they are thawed and before use in a transplant (FACT-JACIE Cellular Therapy Standards).”

Reference: Human Tissue Authority (HTA)

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