TRANSPLANTATION Brief report Cord blood transplantation provides better reconstitution of hematopoietic reservoir compared with bone marrow transplantation

Delayed hematopoietic recovery is the main factor precluding a wider use of cord blood (CB) transplants. We hypoth-esized that this delayed engraftment might not be related to an insufficient number of stem cells in the graft, but to an intrinsic difficulty of these cells to undergo differ-entiation. To test our hypothesis, 2 groups of children were compared; 12 received a CB transplant and 12 an adult bone mar-row (BM) transplant. We studied neutro-phil and platelet recovery and, at a me-dian time of approximately 1 year after transplantation, the frequency of colony-forming cells (CFCs) and long-term cul-ture initiating cells (LTC-ICs) in the BM of the 2 groups. Recipients of BM trans-plants received 1-log more cells and had significantly faster neutrophil and plate-let recovery. Conversely, the frequency of committed and early progenitors was sig-nificantly higher in the BM of children given CB cells compared with BM trans-plant recipients (median count of CFC/ 2 104 BM mononuclear cells, 20 versus 11, P .007; median count of LTC-IC/106 BM mononuclear cells, 8.2 versus 0.2 P .001). CB, but not adult BM stem cells, can better restore the host hemato-poietic progenitor cell reservoir; the de-layed engraftment after CB transplanta-tion may reflect the difficulty of CB progenitors to reprogram themselves to-ward differentiation. (Blood. 2003;102