PROGRESS IN THE EX-VIVO EXPANSION OF HEMATOPOIETIC PROGENITORS

In this review we describe how studies on the cytokine-stimulated grow th of murine bone marrow (BM) progenitors have lead to the observation s that large increases in progenitor numbers can be achieved in short- term cytokine-stimulated liquid cultures. Transplantation of these ex vivo expanded murine BM cells was shown to decrease the number of BM c ells required to confer radioprotection and to increase the recovery r ate of both myeloid and erythroid peripheral blood cells. The ex vivo expansion of murine BM cells does not, however, markedly diminish stem cells capable of long-term hematopoietic reconstitution. Investiga- t ions on the expansion of human BM, peripheral blood, umbilical cord bl ood and fetal hematopoietic progenitors have demonstrated that clinica lly useful increases in progenitor numbers from these tissues are poss ible. Thus, ex vivo progenitor expansion may soon be of use in transpl antation protocols to accelerate hematopoietic reconstitution and in g ene therapy protocols if hematopoietic stem cells can be maintained du ring ex vivo culture.