Affiliation:
1. From Stem Cell Laboratory, Division of Hematology, the Department of Medicine and the Department of Medicine and Laboratory Medicine and Pathology, University of Minnesota, Minneapolis.
Abstract
Abstract
We have recently shown that more than 90% of long-term culture initiating cells (LTC-IC) mobilized in the peripheral blood (PB) of normal individuals express HLA-DR and CD38 antigens and can sustain hematopoiesis for only 5 weeks. However, 10% of LTC-IC in mobilized PB are CD34+HLA-DR− and CD34+CD38− and can sustain hematopoiesis for at least 8 weeks. We now examine the ex vivo expansion potential of CD34+HLA-DR+ cells (rich in mature LTC-IC) and CD34+HLA-DR− cells (rich in primitive LTC-IC) in granulocyte colony-stimulating factor (G-CSF ) mobilized PB progenitor cells (PBPC). Cells were cultured in contact with M2-10B4 cells (contact) or in transwells above M2-10B4 (noncontact) without and with interleukin-3 (IL-3) and macrophage inflammatory protein (MIP-1α) for 2 and 5 weeks. Progeny were evaluated for the presence of colony-forming cells (CFC) and LTC-IC. When CD34+HLA-DR+ PB cells were cultured in contact cultures without cytokines, a threefold expansion of CFC was seen at 2 weeks, but an 80% decrease in CFC was seen at week 5. Further, the recovery of LTC-IC at week 2 was only 17% and 1% at week 5. This confirms our previous observation that although CD34+HLA-DR+ mobilized PB cells can initiate long-term cultures, they are relatively mature and cannot sustain long-term hematopoiesis. In contrast, when CD34+HLA-DR− mobilized PB cells were cultured in contact cultures without cytokines, CFC expansion persisted until week 5 and 49% and 11% of LTC-IC were recovered at week 2 and 5, respectively. As we have shown for steady state bone marrow (BM) progenitors, recovery of LTC-IC was threefold higher when CD34+HLA-DR− PBPC were cultured in noncontact rather than contact cultures, and improved further when IL-3 and MIP-1α were added to noncontact cultures (96 ± 2% maintained at week 5). We conclude that although G-CSF mobilizes a large population of “mature” CD34+HLA-DR+ LTC-IC with a limited proliferative capacity, primitive CD34+HLA-DR− LTC-IC present in mobilized PB have similar characteristics as LTC-IC from steady state BM: (1) they can be maintained in noncontact cultures containing IL-3 and MIP-1α for at least 5 weeks; (2) they are subject to the same proliferation inhibitory influences of contact with stroma. Since the absolute number of primitive LTC-IC (week 8 LTC-IC) per mL of G-CSF mobilized PB is similar to that per mL of steady state BM, these studies further confirm that G-CSF mobilized PBPC may have similar long-term repopulating abilities as steady state BM.
Publisher
American Society of Hematology
Subject
Cell Biology,Hematology,Immunology,Biochemistry
Cited by
41 articles.
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