Umbilical cord blood as a source of hematopoietic stem cells: from research to clinical application.

The clonogenic capacity of human umbilical cord blood (UCB) has been evaluated in several studies which found high numbers of primitive hematopoietic progenitor cells. Recently, UCB progenitor cells were shown to possess significant advantages over bone marrow (BM) in terms of proliferative capacity and immunologic reactivity. Therefore UCB has come to be considered an attractive source of hematopoietic stem cells for both research and clinical applications. UCB has been used in the treatment of diseases potentially curable by bone marrow transplantation (BMT). Seventy-one transplants have been performed world-wide using UCB cells, and the results have been reported to the International Cord Blood Transplant Registry (ICBTR). Since UCB cells appear to be less alloreactive than BM cells, studies have been carried out to determine the most successful procedures for collection and fractionation of UCB and to quantify precisely the progenitor/stem cell content. The different techniques for quantifying progenitor/stem cells as well as the results of related and unrelated UCB treatments will be reviewed. Further clinical applications of UCB involving gene therapy and stem cell expansion will be discussed.