How long can cord blood be stored?
Cord blood transplantation is a clinically effective form of treatment for many patients with cancer and blood diseases who need a stem cell transplant and more recently, has become a relevant source of cells in regenerative medicine.
There is no definitive consensus on how long frozen cord blood can be stored but scientists and clinicians worldwide are of the opinion that if cryopreserved and stored properly, then storage can be for decades or more. At Smart Cells we use state of the art processing, cryopreservation and 24/7 monitored storage technologies designed to optimise the viability of stem cells. In vapour phase nitrogen temperatures below -170oC, all metabolic activities in cells are suspended therefore there should be no deterioration. The majority of public and private banks worldwide use similar technologies as they are tried and tested.
Key work undertaken by Professor Hal Broxmeyer, a distinguished world leader in the field of cord blood therapeutics has demonstrated efficient cell recovery at 5 years, 10 years, 15 years, and most recently 23.5 years after cells were cryopreserved (1). Cord blood storage has been available for around 29 years, although in the early years not many units were being stored and used. It is therefore not possible to look at empirical data beyond that time point, however Professor Broxmeyer’s team plan perform a 30 year assessment on the oldest cord blood specimens (2). Realistically, it is in the last 18 years approximately, that transplantation using cord blood has become a fully accepted therapeutic option and experts in the field have confidence that ongoing banking and use should continue (3).
As far as Smart Cells is concerned, 6 years is the longest interval between storage and thawing of frozen cord blood cells that were given to a patient as a transplant which was satisfactory in terms of cell recovery and engraftment. So far no older units have yet been requested.
At Smart Cells, as part of our Quality Assurance programme and regulatory compliance, we regularly undertake validation studies to ensure that our processing, freezing and storage of cord blood is efficient and that total nucleated and viable CD34+ stem cell recoveries are satisfactory after thawing.
Provided that procedures to process, store and thaw stem cells are of a high standard, the main factor that can potentially affect the ultimate post thaw recovery is the original quality of the cord blood sample itself. Those with initial low viability/low cell numbers may not withstand the thawing process in the same way as a more cellular and robust product.
It may take some time before clinical studies demonstrate conclusively that cord blood stem cells are viable after long-term frozen storage beyond 30 or more years. Clinical proof will require treating of patients with cord blood units that have been in storage for decades but for now, at SCI we are aligning our advice with current worldwide expert opinion.
(1) Blood. 2011; 5; 117(18): 4773–4777 (2) https://parentsguidecordblood.org/en/news/how-long-can-cord-blood-be-stored (3) Stem Cells Translational Medicine S2017;6:1309–1311