[Studies on ex vivo expansion of megakaryocytic progenitor and its application--review]

Application of ex vivo expanded megakaryocytic progenitor cells (MKPC) is a strategy for the treatment of thrombocytopenia after hematopoietic stem cell transplantation. Some growth factors including thrombopoietin (TPO), megakaryocyte growth and development factor (MGDF), interleukin (IL)-1, IL-3, IL-6, IL-11, platelet-derived growth factor (PDGF), and serotonin (5-HT) have been demonstrated to play an important role on the regulation of megakaryocyte/platelet development, the efficient conditions for the expansion of the megakaryocyte (MK) progenitors from hematopoietic stem/progenitor cells were discussed in this review article. TPO alone produced a high proportion of MK progenitors but a low total cell count. The addition of IL-1 beta, IL-3, IL-6 and Flt-3L improved the expansion outcome. The combination of three to five cytokines produced more efficient expansions of hematopoietic stem and MK progenitors. PDGF also enhanced the ex vivo expansion of CD61+ CD41+ cells and CD34+ cells in combination with TPO, IL-1 beta, IL-3, IL-6 and Flt-3L. PDGF is a suitable growth factor to improve the ex vivo expansion of MKPC without promoting their in vitro maturation. More importantly, PDGF also enhanced the engraftment of human stem and progenitor cells in NOD/SCID mice. It has been reported that MKPC can be safely administered to autologous peripheral blood progenitor cell transplant recipients. In short, MKPC can be expanded ex vivo and safely applied to autologous transplant.