Ex vivo expansion of human umbilical cord blood and peripheral blood CD34(+) hematopoietic stem cells

Objective, The proliferation and expansion of human hematopoietic stem cell s (HSC) in ex vivo culture was examined with the goal of generating a suita ble clinical protocol for expanding HSC for patient transplantation. Materials and Methods, HSC were derived from umbilical cord blood (UCB) and adult patient peripheral blood stem cell collections. HSC were stimulated to proliferate ex vivo by a combination of two growth factors, flt-3 ligand (FL) and thrombopoietin/c-mpl ligand (TPO/ML), and assessed for expansion by flow cytometry. Results, Ex vivo expansion cultures of UCB were maintained for prolonged pe riods (up to 16 weeks), and sufficient HSC were generated for adult transpl antation. In contrast to UCB, FL + TPO/ML did not significantly increase CD 34(+) peripheral blood stem cell (PBSC) numbers. Conclusion. UCB-HSC can be expanded in culture to numbers theoretically ade quate for safe, rapid engraftment of adult patients. Additional studies are needed to establish the functional activity of expanded UCB-HSC. (C) 2000 International Society for Experimental Hematology, Published by Elsevier Sc ience Inc.