Umbilical cord derived stem cell transplants
Stem cell transplantation from human donors has been established as an effective prospect of cure for certain types of leukaemia. However, shortages of suitable (related) human donor cells have led to trials of cells from unrelated donors. In this article Dr John Davies reviews the latest research underpinning the use of umbilical cord cell transplants for leukaemia.
- Haemopoietic stem cell transplants from an adult donor remain the best prospect for cure in haematological malignancy, inherited bone marrow dysfunction, and severe immunodeficiency.
- Currently optimal donors are siblings who have human leucocyte (white blood cell) antigens (HLA) identical to the patient.
- Lack of HLA compatible donors is a constraint on treatment even with international registries.
- Umbilical cord blood contains haemopoietic stem cells capable of repopulating the bone marrow which are readily available and may have immunological advantages.
- Umbilical cord derived stem cells are established in the treatment of children, but limitations in stem cell numbers makes treatment in adults less well-established.
- Recent reports indicate that umbilical cord stem cell transplants in adults can give good results even when one or two HLA mismatches are present.
- Current research aims to increase stem cell numbers in the laboratory and investigate the use of multiple cord donations in adults.
- Use of these new treatment methods should currently be restricted to research studies.
Declaration of interests: No conflict of interests declared
Despite advances in chemotherapy and supportive care, allogeneic, haemopoietic stem cell transplantation offers the best prospect of cure for certain categories of patients suffering from haematological malignancies. For non-malignant haematological conditions, including those associated with severe immunodeficiency and inherited abnormalities of bone marrow function, allogeneic stem cell transplantation may offer the only prospect of long term survival.
Sibling human leucocyte antigen matched donor
Traditionally, allogeneic stem cell transplantation depended upon the availability of a sibling HLA-matched donor. Although there are clearly many recipient-related considerations around the use of allogeneic transplantation, one of the major constraints to the expansion of sibling allogeneic transplantation arose from issues surrounding donor availability. Various methods have and continue to be explored to solve this problem, with the now best established being the use of unrelated donors recruited worldwide onto various international registries. Even with the time and resource that has been devoted to the development of this donor network, there are still significant numbers of patients for whom no suitable donor can be found.
One approach to resolving this issue is to relax the requirements for HLA compatibility between the donor and recipient. However, this increases the complexity and toxicity of the transplant, which, in turn, directly translates into higher transplant-related morbidity and mortality. For example, although the use of haplo-identical (half-matched) donors is being explored, the problems of delayed or partial immune reconstitution, graft rejection and graft-versus-host disease have not been fully resolved and this treatment remains essentially experimental.
Umbilical cord derived stem cells
It has been known for many years that umbilical cord blood contains haemopoietic stem cells with the ability to repopulate and reconstitute bone marrow. Early clinical attempts to use Umbilical cord derived stem cells (UCDSC) as a transplant source go back over 30 years. However, it is really only in the last decade that the use of such stem cells has become sufficiently common for useful data on biology and outcomes to be accrued.1
The potential advantages of UCDSC as a donor source, compared to adult donors, include ready availability, ease and low cost of harvesting, the ability to select or discard on the basis of required HLA types, a decreased risk of transmission of transplant-related infection, such as cytomegalovirus infection, a