No longer a biological waste product: umbilical cord blood.

Haematopoietic stem cell transplantation is an accepted curative therapy for many cancers and inherited non-malignant diseases, including bone marrow failure syndromes, haemoglobinopathies, and inborn errors of metabolism. Stem cells can be used from the bone marrow or blood of matched siblings or appropriately matched unrelated volunteers, but many patients do not have a suitably matched donor. Umbilical cord blood (UCB) has been successfully used as an alternative stem cell source. It has the advantage of tolerance for a degree of human leukocyte antigen (HLA) incompatibility not possible with adult bone marrow, resulting in greater likelihood of finding an appropriate match. UCB is also stored fully tested and cryopreserved, leading to rapid availability. Greatest clinical experience in UCB transplants has been in treating paediatric leukaemia. Results using well matched UCB grafts are equivalent or better than with unrelated bone marrow transplant. Cell dose and the degree of HLA matching are critical determinants in the success of UCB transplant. The use of UCB in older children and adult patients has been limited by the fixed, low cell dose available in a UCB unit, relative to recipient weight. This can be overcome by strategies such as using two or more UCB units. Early animal studies suggest that UCB may have the potential to differentiate into other cell types, including nervous tissue, and may in future play a role in the treatment of disorders such as Alzheimer disease and Parkinson disease.