Ex vivo expansion of mobilized peripheral blood stem cells.

The scarcity of donors for allogeneic bone marrow transplantation, the limited number of haematopoietic stem cell (HSC)/progenitors in cord blood samples and the sometimes insufficient number of mobilized peripheral blood cells collected from heavily treated cancer patients may benefit from ex vivo expansion of these cells for clinical transplantation. Depending on the clinical application, expansion of different haematopoietic cell subsets is required. HSC transplantation requires expansion of all cellular subsets including precursors, progenitors and HSCs for the short and long-term engraftment of patients. Quiescent HSCs may also be required for gene therapy by retrovirus. Finally, amplification of cells such as dendritic cells (DC) and different subsets of T and natural killer (NK) cells is required for immunotherapy. The different haematopoietic lineages are produced under different experimental conditions and the starting population is a critical parameter for the proposed clinical application. So it is essential to define the aims of haematopoietic cell expansion and to adapt the experimental conditions to obtain the required cell population. Mobilized peripheral blood cells are increasingly used as a source of haematopoietic cells. We review the biological characteristics of mobilized peripheral blood and the expansion of the different components according to the aims of their clinical use in the context of the progress currently achieved.