It is postulated that volume reduction of umbilical cord blood units inalbumin or dextran before infusion into patients results in improved cellviability. In order to get the best stem cells possible, it is best to takethem in the umbilical cord blood. They can then be stored in a cord blood bankor stem cell bank for the best cord blood collection.
This is based on an in vitro study, which showed that the stem cellviability could actually be improved by volume reducing the umbilical cordblood units before infusion to restore the osmolarity of the suspension.
It was suggested that this process could protect the stem cells from thesevere osmotic stress associated with infusion of cells suspended in medium withhigh concentrations of dimethyl-sulfoxide.
Neutrophils were the major cell population affected by the in vitroincubation whereas mononuclear cells that include the pluripotent stem cellswere relatively resistant to the in vitro toxic effects of dimethyl-sulfoxide.
By reducing the volumes of both dimethyl-sulfoxide and cell lysisproducts, washing may also decrease the adverse reactions associated with theinfusion of cryo preserved units.
However, volume reducing umbilical cord blood grafts after thawing canreduce the number of hematopoietic stem cells infused into the patients becauseof cell loss during manipulation.
Many studies have shown that infusing a high nucleated cell dose is agood prognostic factor for both engraftment and survival in umbilical cordblood transplantation. It is known that the number of cells infused duringumbilical cord blood transplantation is one log less than in a standardallogeneic bone marrow transplant.
In addition, the umbilical cord blood manipulation may cause qualitativechanges in the product that may affect engraftment. The slow engraftmentbecause of the limited number of hematopoietic stem cells available in a singleunit of umbilical cord blood may contribute to high peritransplant mortalityand limit the success of umbilical cord blood transplant especially in adultpatients.
Therefore, any process that may result in hematopoietic stem cells lossor adversely affect hematopoietic stem cells viability, that is, manipulation,should be avoided especially in umbilical cord blood units with low number ofhematopoietic stem cells.
An earlier study observed delayed neutrophil recovery in three patientsreceiving unmanipulated umbilical cord blood. However, these patients receivedMethotrexate that impacts on hematopoietic recovery.
It was found that the hematopoietic recovery and survival of therecipients of unmanipulated umbilical cord blood were comparable to those ofvolume reduced umbilical cord blood.
