Ex vivo expansion of megakaryocytes.

We evaluated the capacity of several early acting cytokines (FL, SCF, TPO ± IL3 and IL6) to act on very primitive megakaryocytic progenitor cells residing in BM, CB and MPB [9. W. Piacibello, F. Sanavio, L. Garetto, A. Severino, D. Bergandi, J. Ferrario, F. Fagioli, M. Berger and M. Aglietta, Extensive amplification and self-renewal of human primitive hematopoietic stem cells from cord blood. Blood 89 (1997), p. 2644. View Record in Scopus | Cited By in Scopus (313)9, 10 and 11]. Our study focused on maximizing expansion of Mk lineage without depleting the granulocyte and the more immature progenitor cell lineages. We used purified CD34 + hematopoietic stem cells in order to obtain an enhanced proliferative capacity. The rationale for a preselection step is based on the presence of inhibitory accessory cells in marrow peripheral blood or cord blood, which is supposed to limit the degree of expansion of the progenitor compartment in ex vivo cultures.