Cord blood transplantation is a clinically effective form of treatment for many patients with cancer and blood diseases who need a stem cell transplant. More recently, cord blood 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. Smart Cells 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 -170 degrees Celsius, all metabolic activities in cells are suspended, meaning there should be no deterioration. The majority of public and private banks worldwide use similar tried and tested technologies.
Key work undertaken by Professor Hal Broxmeyer, a distinguished world leader in the field of cord blood therapeutics has demonstrated efficient cell recovery at five 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 to 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).
At Smart Cells, six 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. No units older than this have yet been requested.
As part of Smart Cells’ Quality Assurance programme and regulatory compliance, the team regularly undertake validation studies to ensure that the processing, freezing, and storage of cord blood is efficient and that total nucleated and viable CD34+ stem cell recoveries are satisfactory after thawing.
If 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, Smart Cells’ advice aligns with current worldwide expert opinion.