Critical factors for a successful stem cell transplantation.


We consider a transplantation to be successful when the transplant unit (graft) has been accepted by the recipient.


Quantity. In order for a cord blood unit to be useful it should contain a sufficient number of stem cells. The cord blood units, even when they have a sufficient number of stem cells for a certain bodyweight, are useful for a single application only, based on current scientific facts. So, the question arises as to whether we could overcome the limitation that cord blood unit s have, i.e. the limited number of stem cells?

  • The proliferation of cord blood stem cells remains experimental and has also reached the level of clinical applications. There are some encouraging data on the proliferation of stem cells in clinical practice and scientists have high expectations regarding the improvement of patients' prognosis.


  • An alternative clinical approach to the proliferation of stem cells, as a way to overcome the limited number of stem cells in cord blood units, is the simultaneous transplantation of an autologous cord blood unit with a compatible cord blood unit from another person (allogeneic). In this way we can increase the available number of stem cells, thus expanding their therapeutic potential in children and adults. Many such dual-unit transplants have been performed to date. Since 1999, 993 adults with hematological diseases have undergone a double umbilical cord blood transplant. (Hematologica. 2011; 96: 1213-1220). In fact recent studies prove that more patients have received double transplant units than those that have received a single unit. (Bone Marrow Transplant. 2012; 47: 924–933).
  • Dual transplants can also be successfully performed by combining an autologous cord blood unit with a compatible bone marrow unit. Such transplants have effectively been transplanted to treat thalassemia.(Pediatr Hematol Oncol. 2000 Jun;17:307-314).
  • Finally, if a cord blood unit has a low count of stem cells and is not considered adequate to treat hematological diseases it can still be quite useful in future applications of regenerative medicine



When a person uses his own stem cells (autologous transplant) we have naturally full compatibility. In all other cases (allogeneic transplants), the probability that a transplantation will be successful is enhanced when there is full compatibility between donor and recipient. However, if the graft comes from a compatible sibling we observe a higher probability of success than when the graft comes from another compatible person, even in cases of partial compatibility between the siblings.  



The sooner after a diagnosis the patient undergoes transplantation, the better the chances of long term survival. This is why the units stored in family banks are so valuable because they can be made available on short notice.


Graft versus host disease.

The greatest risk to patients who undergo cord blood or bone marrow transplants is the devastating effect of the Graft vs. Host Disease (Graft Versus Host Disease, GvHD). This disease is an "attack" of the immune system of the donor cells against the recipient cells, which they recognize as 'foreign'. Cord blood transplants present a lower risk of GvHD due to the fact that cord blood stem cells are “immature” and have not yet differentiated into other types of cells. This is an important advantage of cord blood transplantations when compared to transplantations with bone marrow.