The number of nucleated cells reflects: the hematopoietic content of umbilical cord blood for transplantation

A single umbilical cord blood (UCB) collection may contain sufficient hemat opoietic stem cells to achieve engraftment and repopulation of the hematopo ietic system of children and adults after myeloablative therapy. The hemato poietic potential of a UCB unit is often defined by the number of CD34(+) c ells or the number of colony-forming units as measured in semisolid hematop oietic progenitor cell (HPC) cultures. However, these assays are relatively difficult to standardize between UCB banks. The number of nucleated cells infused per kilogram body weight of the recipient is also reported to be a significant factor in the speed of recovery of neutrophils and platelets af ter transplantation. To analyze which parameters could be used to evaluate the hematopoietic potential of a UCB graft, we evaluated almost 300 UCB uni ts that were collected for banking for unrelated transplantation. A strong correlation was found between the frequencies of CD34(+) cells and the HPC as measured in semi-solid medium cultures. From the various leukocyte subpo pulations, the concentration and total numbers of nucleated cells correlate d best with both the HPC content and the number of CD34(+) cells. Different iation of these nucleated cells into subsets of leukocytes offered no advan tage for better prediction of HPC or CD34(+) cells, These results indicate that the nucleated cell count probably reflects the hematopoietic potential of a UCB graft, and may for that reason correlate with the speed of engraf tment after transplantation.