Abstract
Human hematopoietic stem cells (HSC) in cord blood (CB) are increasingly being used as an alternative to those in adult bone marrow (BM) for treating patients with various hematological disorders. However, the difference in the hematopoietic activity of HSC between CB and adult BM is still unclear. We then compared CD34+ cells, a hematopoietic cell population, in CB with those in adult BM, using their phenotypic subpopulations, colony-forming activity and long-term repopulating ability. Although the proportion of CD34+ cells was higher in adult BM than CB mononuclear cells in flow cytometry, more immature subpopulations, CD34+CD33- and CD34+CD38- cells, were present in CB CD34+ cells. Clonal culture assay showed that more multipotential progenitors were present in CB CD34+ cells. When transplanted into immunodeficient NOD/SCID mice, adult BM CD34+ cells could not reconstitute human hematopoiesis in recipient BM, but CB CD34+ cells achieved a high level of engraftment, indicating that CB CD34+ cells possess greater repopulating ability. Thus, CB CD34+ cells contain more primitive hematopoietic cells including HSC, suggesting the usefulness of CB CD34+ cells not only as a graft for therapeutic HSC transplantation, but as a target cell population of ex vivo expansion of transplantable HSC.
