Expansion of Non-Enriched Cord Blood Stem/Progenitor Cells CD34+ CD38- Using Liver Cells

Many investigators have used xenogeneic, especially murine stromal cells and fetal calf serum to maintain and expand human stem cells. The proliferation and expansion of human hematopoietic stem cells in ex vivo culture were examined with the goal of generating a suitable protocol for expanding hematopoietic stem cells for patient transplantation. Using primary fetal liver cells, we established a serum-free culture system to expand human primitive stem/progenitors cells. Non-enriched cord blood CD34+ cells were cultured on a monolayer of mouse primary fetal liver cells in the presence of trombopoietin, flt3/flk2 ligand, and/or stem cell factor, IL-6 and IL-3 under serum-free conditions. After 1 or 2 weeks of culture, cells were examined for clonogenic progenitors and percentage of CD34+ CD38- cells.  In the presence of trombopoietin, flt3/flk2 ligand, and stem cell factor, fetal liver cells supported expansion of CD34+ cells more than 10 to 20 fold. In addition, colony forming unit-cell assay was expanded more than 5- and 10-fold after 1 and 2 weeks of culture, respectively.  These results strongly suggest that fetal liver cells may be a suitable feeder layer for expansion of hematopoietic progenitors from umbilical cord blood in vitro