Stem cell source and harvesting

Bone marrow

Until recently, HSC have been harvested by aspiration from the bone marrow. However, the need for complete anesthesia as well as the fatigue and pain the donor might suffer from has encouraged the harvesting of HSC from peripheral blood.

Peripheral blood

Under normal conditions, the hematopoietic stem cells in the blood are in equilibrium with the HSC in the marrow and circulate in the peripheral blood at a steady state of less than 0.1%. The administration of recombinant growth factors (G-CSF) temporarily shifts this equilibrium so that a high enough number of peripheral blood stem cells (PBSC) can be harvested by leukopheresis. G-CSF has now been administrated to thousands of donors with only minor side effects such as headache, fatigue and nausea, which remain limited to the period during which the G-CSF is given.

Umbilical cord blood

Umbilical cord blood may be an alternative source of HSC. The number of HSC in cord blood is considerably lower than in classical marrow of PBSC donation. Therefore, it can only be used for the transplantation of children and small adolescents. The advantage of using cord blood is that the immature immune system of the newborn is less aggressive than that of an adult and as a result, the alloreactive T cells in the graft cause less GVHD. This allows transplantation with a higher degree of HLA-mismatches. Hence, in a situation where no HLA-matched donor is available or when it would take too long to wait for the results of a donor search, a mismatched cord blood donation might be taken into consideration.

At present, umbilical cord blood banks have been established in many transplantation centers and more than 100'000 units are available.