title: [Cord blood transplantation and ex vivo expansion of hematopoietic stem cells].
abstract: Umbilical cord blood has provides an alternative source to bone marrow for transplantation in children and some adults. However it has been thought to be necessary to expand hematopoietic stem cells in cord blood for adult-size transplantation. Flow-cytometric analysis revealed that most immature hematopoietic progenitors express gp130 but not interleukin-6 receptor (IL-6R). We established an ex vivo expansion system of human hematopoietic stem/progenitor cells using soluble IL-6R (sIL-6R). A combination of sIL-6R/IL-6 complex and SCF expanded CFU-Mix approximately 60-fold in both serum-containing and serum-free cultures by day 14. Addition of anti-gp130 mAbs and anti-IL-6R mAb to the above cultures dose-dependently inhibited the expansion of progenitors, suggesting that gp130 signalling initiated by the sIL-6R/IL-6 complex is important for significant expansion of human hematopoietic stem/progenitor cells. Addition of thrombopoetin and/or Flk2/Flt3 ligand (FL) to culture with sIL-6R/IL-6/SCF augmented the expansion of not only hematopoietic progenitors assayable in clonal culture but also hematopoietic stem cells estimated by NOD/SCID mice. Recent evidence shows that hematopoietic stem cells first occur and expand in aorta-gonad-mesonephros(AGM) region at 10 to 11 days post coitum(dpc) in murine, which suggests that AGM region at this stage provides a microenvironment suitable for development for hematopoietic stem cells. We reported here on a novel stromal cell line derived from the AGM region at day 10.5 dpc, which supported for 6 weeks generation of human multipotential hematopoietic progenitors from cord blood CD34+38- primitive hematopoietic cells in a co-culture system. This cell line is expected to elucidate molecular mechanisms regulating early hematopoiesis, and pave the way for developing strategies for ex vivo expansion of human transplantable hematopoietic stem cells.
authors.affiliation: Department of Pediatric Hematology and Oncology, University of Tokyo.
authors.forename: T
authors.initials: T
authors.lastname: Nakahata
mesh_terms: D000818:Animals; D005312:Fetal Blood; D019650:Hematopoietic Stem Cell Mobilization; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D013234:Stem Cells / Q000502:physiology*