Establishment of Fetal Human Liver Hematopoietic Progenitor Cells in Long-Term Cultures Maintained on Engineered Murine Stromal Cells

Abstract 899 Poster Session II, Sunday, 5/2 (poster 143) Fetal human liver (FHL) contains hematopoietic progenitor cells. These cells, as an alternative to adult bone marrow (BM) or human umbilical cord blood (CB) cells, are considered good candidates for gene transfer and transplantation. Previous attempts to purify progenitor stem cells from FHL using flow cytometry sorted CD 34 positive cells yielded insufficient and unhealthy cells. We have now adapted a co-culture system in which highly purified FHL mononuclear cells are seeded onto irradiated murine fibroblasts that were engineered by retroviral-mediated gene transfer to produce specific human growth factors. The co-cultures were then maintained as standard long-term cultures (LTC) with half-media changes and removal of half the non-adherent cells each week. The remaining cells, after 5 weeks, were found to be capable of forming colonies. We compared CD34+CD38- cells sorted by flow cytometry with LTC-initiating cells derived from FHL for their ability to form colonies. Using equal numbers of CD34+CD38- and LTC-IC, we observed that the former population produced only one tenth the number of colonies that the LTC-IC produced. This study suggests that there is a greater potential for colony forming cells in a highly enriched population of FHL LTC-IC than in sorted CD34+CD38- cells. USPHS grant MH46815 and Children's Research of Michigan