Expansion of stem and progenitor cells.

An increasing interest exists in strategies to manipulate hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) in vitro for clinical purposes by use of recombinant hematopoietic growth factors. A major goal of these ex vivo expansion strategies is to expand repopulating HSCs or to generate lineage-committed progenitors in the context of autologous or allogeneic stem cell transplantation. The ex vivo HSC/HPC expansion approach may have several clinical applications: 1) in the autologous setting, reduction of tumor cell contamination within the amplified transplantation product, 2) purging effects through possible growth advantage of HSCs/HPCs over contaminating tumor cells under appropriate in vitro conditions and purging effects of certain HGFs and antitumor agents during ex vivo culture, 3) the possibility of multiple transplants through repetitive use of cryopreserved HSC/HPC samples from one individual, 4) production of dendritic cells for immunotherapy, 5) production of mature blood cells for transfusion therapies including nadir rescue, and 6) gene therapy. Here, we summarize recent developments in the field of HSC/HPC expansion.