Umbilical Cord Blood Transplantation: A New Alternative Option
Allogeneic hematopoietic stem cell transplantation is a life-saving procedure for hematopoietic malignancies, marrow failure syndromes, and hereditary immunodeficiency disorders. Umbilical cord
blood (UCB) has being increasingly used as an alternative hematopoietic stem cell source for these patients. To date, over 6000 UCB transplant procedures in children and adults have been performed
worldwide using UCB donors. Broader use of UCB for adult patients is however limited by the available infused cell dose. This has prompted intensive research on ex vivo expansion of UCB stem cells and UCB graft-engineering including accessory cells able to improve UCB engraftment and reconstitution and for tissue regenerative potential. UCB is anticipated to address needs in both transplantation and regenerative medicine fields. It has advantages of easy procurement, no risk to donors, low risk of transmitting infections, immediate availability and immune tolerance allowing successful transplantation despite HLA disparity.
Transplantation of unrelated UCB permits a greater degree of HLA mismatching without an unacceptably high incidence of graft-versus-host disease (GVHD). Graft characteristics known to allow rapid donor engraftment in recipients.
Advantages of umbilical cord blood (UCB) as hematopoietic stem cells for allogeneic transplantation.
1. Umbilical cord blood is an abundantly available source of stem cells, which can be harvested at no risk to the mother or infant.
2. Since collection occurs after birth of a full term normal infant, UCB is not associated with current ethical concerns raised in use of embryonic stem cells.
3. Ethnic balance in a cord blood repository can be maintained automatically in heterogeneous populations or can be controlled via collection from birthing centers representing targeted minority populations.
4. There is low viral contamination of UCB including cytomegalovirus and Epstein-Barr virus.
5. UCB, cryopreserved and banked, is available on demand particularly for patients with unstable disease, eliminating delays and uncertainties that now complicate marrow collection from unrelated donors.
6. To date, no malignant transformation of infused UCB has been observed in any transplant recipient.
7. The amplification of allogeneic responses including Th1- associated cytokine production by neonatal T lymphocytes has been shown to be less than that of adult T cells, which may underlie UCB reduced graft-versus-host reactivity compared with adult-derived marrow grafts.
8. Frozen UCB can be easily shipped and thawed for use when needed, compared to freshly donated bone marrow, which has a limited shelf-life, necessitating coordination between harvesting physicians, transportation personnel, and transplantation teams.
9. Advancing age of the donor to hematopoietic and immune function in the recipient; pediatric patients transplanted with newborn HSC would expectedly maintain normal hematopoietic and immune function during advancing.
Banked unrelated umbilical cord blood (UCB) has emerged as an alternative allogeneic stem cell source, providing available and suitably HLA-matched donors for patients requiring allogeneic transplantation.
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