It is postulated that volume reduction of umbilical cord blood units in albumin or dextran before infusion into patients results in improved cell viability. In order to get the best stem cells possible, it is best to take them in the umbilical cord blood. They can then be stored in a cord blood bank or stem cell bank for the best cord blood collection.
This is based on an in vitro study, which showed that the stem cell viability could actually be improved by volume reducing the umbilical cord blood units before infusion to restore the osmolarity of the suspension.
It was suggested that this process could protect the stem cells from the severe osmotic stress associated with infusion of cells suspended in medium with high concentrations of dimethyl-sulfoxide.
Neutrophils were the major cell population affected by the in vitro incubation whereas mononuclear cells that include the pluripotent stem cells were relatively resistant to the in vitro toxic effects of dimethyl-sulfoxide.
By reducing the volumes of both dimethyl-sulfoxide and cell lysis products, washing may also decrease the adverse reactions associated with the infusion of cryo preserved units.
However, volume reducing grafts after thawing can reduce the number of hematopoietic stem cells infused into the patients because of cell loss during manipulation.
Many studies have shown that infusing a high nucleated cell dose is a good prognostic factor for both engraftment and survival in umbilical cord blood transplantation. It is known that the number of cells infused during transplantation is one log less than in a standard allogeneic bone marrow transplant.
In addition, the manipulation may cause qualitative changes in the product that may affect engraftment. The slow engraftment because of the limited number of hematopoietic stem cells available in a single unit of umbilical cord blood may contribute to high peritransplant mortality and limit the success of umbilical cord blood transplant especially in adult patients.
Therefore, any process that may result in hematopoietic stem cells loss or adversely affect hematopoietic stem cells viability, that is, manipulation, should be avoided especially in umbilical cord blood units with low number of hematopoietic stem cells.
An earlier study observed delayed neutrophil recovery in three patients receiving unmanipulated umbilical cord blood. However, these patients received Methotrexate that impacts on hematopoietic recovery.
It was found that the hematopoietic recovery and survival of the recipients of unmanipulated umbilical cord blood were comparable to those of volume reduced umbilical cord blood.