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

Objective The proliferation and expansion of human hematopoietic stem cells (HSC) in ex vivo culture was examined with the goal of generating a suitable 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 periods (up to 16 weeks), and sufficient HSC were generated for adult transplantation. In contrast to UCB, FL + TPO/ML did not significantly increase CD34+ peripheral blood stem cell (PBSC) numbers. Conclusion UCB-HSC can be expanded in culture to numbers theoretically adequate for safe, rapid engraftment of adult patients. Additional studies are needed to establish the functional activity of expanded UCB-HSC.