RELEASE FROM QUIESCENCE OF CD34- HUMAN UMBILICAL-CORD BLOOD-CELLS REVEALS THEIR POTENTIALITY TO ENGRAFT ADULTS( CD38)

Using optimal culture conditions in which the transforming growth fact or beta1 (TGF-beta1) inhibitory loop has been interrupted by antisense TGF-beta1 oligonucleotides or anti-TGF-beta serum, we have compared t he proliferative capacities and the abilities of the CD34+ CD38- cell populations from bone marrow and umbilical cord blood to generate earl y progenitors in long-term cultures. The CD34+ CD38- fraction of umbil ical cord blood accounts for 4% of the CD34+ fraction compared to only 1% in bone marrow, indicating that umbilical cord blood may be relati vely enriched in stem cells. We estimate that the CD34+ CD38- cells fr om a typical umbilical cord blood sample produce equivalent numbers of colony-forming units -granulocyte/erythrocyte/macrophage/megakaryocyt e, twice as many CFU-granulocyte/macrophage (GM) and 3 times as many b urst-forming units-erythroid as the same population from an average bo ne marrow sample used in adult transplantation. In addition, the colon ies resulting from the umbilical cord blood samples were significantly larger than those from bone marrow, indicating a greater growth poten tial. However, the content of later progenitors, which may be importan t for short-term reconstitution, was less in umbilical cord blood-deri ved than in bone marrow-derived cell preparations, as estimated by a 4 -fold lower production of CFU-GM in long-term cultures of CD34+ CD38cells. This deficit is partially compensated by the higher growth capa city of the resulting CFU-GM. These studies suggest that umbilical cor d blood is a suitable source of cells for adult transplantation.