EX-VIVO HEMATOPOIETIC-CELL EXPANSION - A THEORETICAL AND TECHNOLOGICAL CHALLENGE

Preclinical experience has shown that it is possible to maintain and e xpand hematopoietic cells in liquid culture systems by provision of op timal combinations of colony-stimulating factors (CSF). Ex vivo hemato poietic cell expansion (HCE) would be expected to reduce harvesting ti me and effort and could also decrease the infusion dose necessary for hematopoietic reconstitution after bone marrow transplantation. In add ition, ex vivo expanded cells might be of value for therapeutic gene t ransfer. The central question in ex vivo HCE is whether the CSF combin ations employed provide not only amplification of the late progenitor pools, but also maintenance or expansion of the stem cell compartment to ensure long term engraftment. Choice of CSF and experimental parame ters in the culture system appear to be the most critical factors infl uencing the outcome of strategies for ex vivo HCE. Moreover, it is ess ential to define the goal of HCE and to adapt the experimental conditi ons to obtain the required cell populations. In future work, it remain s to test the potential applicability of ex vivo expanded cells and to carefully monitor the possibility of the expansion of tumoral cells i n ex vivo proliferation systems.