MURINE LONG-TERM REPOPULATING ABILITY IS COMPROMISED BY EX-VIVO CULTURE IN SERUM-FREE MEDIUM DESPITE PRESERVATION OF COMMITTED PROGENITORS

Hematopoietic progenitor cells can be maintained and expanded ex vivo in standard or serum-free culture medium supplemented with a variety o f stimulatory cytokines, The use of serum-free medium allows specifica tion of reproducible and precise growth conditions optimal for various applications and is more acceptable from a safety and regulatory poin t of view, Human and murine committed progenitor cells have been shown to be equivalently or better supported by serum-free culture conditio ns in the presence of multicytokine combinations, but there is little information on the effects of such culture conditions on repopulating stem cells, We used a murine competitive repopulation model to assess the effect of serum-free versus serum-containing ex vivo culture on lo ng-term reconstituting cells, Despite equivalent numbers of committed CFU-C and day 12 CFU-S present after 4 days of culture of murine marro w in serum-free or serum-containing conditions in the presence of IL-3 , IL-6, and SCF, long-term reconstituting activity was significantly i mpaired by serum-free culture, These findings may have important impli cations for transplantation and gene therapy applications.