Hematopoietic capability of CD34(+) cord blood cells: A comparison with CD34(+) adult bone marrow cells

The characteristics of hematopoietic progenitor and stem cell (HPC/HSC) pop ulations in mammals vary according to their ontogenic stage. In humans, HPC /HSCs from umbilical cord blood (CB) are increasingly used as an alternativ e to HPC/HSCs from adult bone marrow (BM) for the treatment of various hema tologic disorders. How the hematopoietic activity of progenitor and stem ce lls in CB differs from that in adult BM remains unclear, however. We compar ed CD34(+) cells, a hematopoietic cell population, in CB with those in adul t BM using phenotypic subpopulations analyzed by Row cytometry, the colony- forming activity in methylcellulose clonal cultures, and the repopulating ability of these: cells in NOD/Shi-scid (NOD/SCID) mice. Although the propo rtion of CD34(+) cells was higher in adult BM than in CB mononuclear cells, the more immature subpopulations, CD34(+)CD33(-) and CD34(+)CD38(-) cells, were present in higher proportions in CD34(+) CB cells. Clonal culture ass ay showed that more multipotential progenitors were present in CD34(-) CB c ells. When transplanted into NOD/SCID mice, CD34(+) adult BM cells could no t reconstitute human hematopoiesis in recipient BMI but CD34- CB cells achi eved a high level of engraftment, indicating that CD34(+) CB cells possess a greater repopulating ability. These results demonstrated that human hemat opoiesis changes with development from fetus to adult. Furthermore. CD34(+) CB cells contained a greater number of primitive hematopoietic cells, incl uding HSCs, than did adult BM, suggesting the usefulness of CD34(+) CB cell s not only as a graft for therapeutic HSC transplantation but also as a tar get cell population for ex vivo expansion of transplantable HSCs and for ge ne transfer in gene therapy. Int J Hematol. 2001;73:457-462. (C) 2001 The J apanese Society of Hematology.