Changing phenotypes of hematopoietic stem cells.

Abstract

Identification of the surface phenotypes of hematopoietic stem cells is an important subject in both clinical stem cell transplantation and basic research in hematopoiesis. Transplantation of pure populations of stem cells should eliminate the occurrence of graft-vs-host disease (GVHD) in allogeneic transplantation and may reduce the recurrence rate of malignancies in autologous transplantation. Availability of highly enriched populations of stem cells should facilitate investigations in a number of areas such as in vitro expansion, cryogenic storage, and gene therapy using stem cells. An ultimate goal is to develop a method to quantitate the number of living stem cells based on their surface characteristics. During the last two decades, investigators identified a number of surface molecules, which, in combinations, were thought to provide exact definition of murine and human stem cells. Recent studies of murine stem cells, however, clearly demonstrated that expression of the surface antigens of stem cells is under the influence of developmental stages and the kinetic state of the stem cells. This review summarizes the concept of the changing phenotypes of hematopoietic stem cells.