Expansion of hematopoietic stem/progenitor cells.

Hematopoietic stem/progenitor cells (HSPCs) transplantation is hampered by the low number of stem cells per sample. To tackle this obstacle, several protocols for expansion of HSPCs in vitro are currently in development, such as the use of cytokine cocktails, coculture with mesenchymal stem cells as feeder cells, and cell culture in bioreactors. With the progress in the understanding of the molecular and cellular mechanisms regulating HSPCs maintenance and expansion, more recent approaches have involved transcription regulation, cell cycle regulation, telomerase regulation, and chromatin-modifying agents. The potential clinical application and safety issues relevant to the expanded HSPCs are also discussed in this review. Copyright 2008 Wiley-Liss, Inc.