Scientists in the US have developed a new technique for multiplying the small number of stem cells found in umbilical cord blood and have tested it on leukaemia patients for the first time. It is hoped that the new technique could ultimately remove the need for tissue-matched bone marrow transplants.
Colleen Delaney and colleagues at the Fred Hutchinson Cancer Research Centre in Seattle reported an average 164-fold increase in stem cell numbers. The stem cells were coaxed to multiply in culture by applying a protein which activates the so-called 'Notch pathway', a cell signalling cascade involved in embryo development.
The authors also describe the early results of a phase one clinical trial where the expanded cells 'engrafted' quicker and contributed more than non-expanded transplants. Engrafting is the process by which transplanted cells are accepted by the body and begin producing infection-fighting white blood cells. Delayed engraftment increases the risk of patients catching life-threatening infections. However, much larger clinical trials are needed.
'We have shown that we can decrease the time to engraftment. Now we have to show a clinical benefit to the patient', Dr Delaney said. During the trial, ten patients with leukaemia aged between three and 43 received one unit of standard cord blood and one in which the stem cells had been expanded. The work was published in the journal Nature Medicine.
Stem cells extracted from cord blood can give rise to all blood cell types and offer huge promise for the treatment of leukaemia and other disorders treatable by bone marrow transplant. Unlike conventional bone marrow transplants, cord blood stem cells need not be perfectly matched to the recipient as they lack the characteristics which can normally trigger immune rejection, potentially overcoming the major problem of finding a suitable donor.
Previous research has been hampered by the low number of stem cells present in units of cord blood, approximately one-tenth of those in standard transplants. Without further enrichment, there are not enough stem cells present in cord blood to treat adult patients and previously only young children have been treated successfully. This is also thought to explain why these cells take longer to 'engraft',
In the UK, very limited amounts of cord blood are currently harvested and stored, an issue which recently attracted media attention when MP David Burrowes led a parliamentary debate on the subject of cord blood banking earlier this month, during which he stressed the need to 'alleviate the severe shortage of life-saving cells'.
Responding to this latest study, Henry Braund, chief executive of the Anthony Nolan Trust, said: 'we really need a properly resourced UK cord blood collection programme... if we are to capitalise on this amazing resource and save more lives'.
