Human cord blood progenitors sustain thymic T-cell development and a novelform of angiogenesis

There is growing interest in using human umbilical cord blood (CB) for allo geneic bone marrow transplantation (BMT), particularly in children. Thus, C B has been identified as a rich source of hematopoietic progenitors of the erythroid, myeloid, and B-cell lineages. Whether CB blood cells engrafting in the BM space also comprise T-cell progenitors capable of trafficking to the thymus and reconstituting a functional thymopoiesis in young recipients is presently unknown, Here, we show that CB progenitors, engrafted in the BM of immunodeficient mice, sustain human thymopoiesis by generating circul ating T-cell progenitors capable of homing to and developing within a human thymic graft. Surprisingly, development of CB stem cells in this in vivo m odel extended to elements of the endothelial cell lineage, which contribute d to the revascularization of transplants and wound healing. These results demonstrate that human CB stem cell transplantation can reconstitute thymic -dependent T-cell lymphopoiesis and show a novel role of CB-derived hematop oietic stem cells in angiogenesis. (C) 1999 by The American Society of Hema tology.