Current Strategies to Improve Engraftment in Cord Blood Transplantation

Umbilical cord blood (UCB) remains an important alternative source of hematopoietic stem cells (HSC) for allogeneic transplantation when suitable HLA-matched donors are unavailable. Cord blood (CB) offers many benefits including rapid availability, absence of risk to the donor, and a low incidence of graft-versus-host disease. However, although the overall survival of patients receiving unrelated CB transplants is comparable to using other HSC sources, UCB transplantation is associated with delayed engraftment and poor immune reconstitution, particularly in adults. While this is partly due to the lower cell dose in UCB grafts, it may also reflect the relative immaturity of cord blood. Therefore, many different strategies to enhance hematopoietic engraftment following UCB transplantation are currently under investigation. This article will review the latest techniques including improved collection, HLAmatching, homing and expansion of CB, and the use of double CB grafts, third-party donors, and accessory cells. As many of these methods are now in clinical trials, it is anticipated that UCB transplantation will continue to improve, further expanding our understanding of CB biology and HSC transplantation.