Distinct hematopoietic progenitor compartments are delineated by the expression of aldehyde dehydrogenase and CD34

Abstract

A broad range of hematopoietic stem cells and progenitors reside within a fraction of umbilical cord blood (UCB) that exhibits low light scatter properties (SSClo) and high expression of aldehyde dehydrogenase (ALDHbr). Many SSClo ALDHbr cells coexpress CD34; however, other cells express either ALDH or CD34. To investigate the developmental potential of these cell subsets, purified ALDHbr CD34+, ALDHneg CD34+, and ALDHbr CD34neg UCB cells were characterized within a variety of in vivo and in vitro assays. Primitive progenitors capable of multilineage development were monitored in long- and short-term repopulation assays performed on nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice, and in primary and secondary long-term culture assays. These progenitors were highly enriched within the ALDHbr CD34+ fraction. This cell fraction also enriched short-term myeloid progenitors that were detected in vitro. By comparison, ALDHneg CD34+ cells contained few primitive progenitors and had diminished short-term myeloid potential but exhibited enhanced short-term natural killer (NK) cell development in vitro. The ALDHbr CD34neg cells were not efficiently supported by any of the assays used. These studies suggested that in particular the expression of ALDH delineated distinct CD34+ stem cell and progenitor compartments. The differential expression of ALDH may provide a means to explore normal and malignant processes associated with myeloid and lymphoid development.