Differences in megakaryocyte expansion potential between CD34(+) stem cells derived from cord blood, peripheral blood, and bone marrow from adults and children.

OBJECTIVE: Reinfusion of ex vivo expanded autologous megakaryocytes together with stem cell transplantation may be useful to prevent or reduce the period of chemotherapy-induced thrombocytopenia. We compared the megakaryocyte expansion potential of CD34(+) stem cells derived from different sources: cord blood (CB), peripheral blood (PB), bone marrow from adults (ABM), and bone marrow from children (ChBM). Three different growth factor combinations were tested to identify the best combination for each of the sources.
MATERIALS AND METHODS: CD34(+) cells were isolated from CB, PB, ABM, or ChBM and cultured in an in vitro liquid culture system in the presence of thrombopoietin (Tpo), Tpo + interleukin (IL-1), or Tpo + IL-3. After 8 days, proliferation was determined and the cultured cells were identified with lineage-specific surface markers by flow cytometry.
RESULTS: Cultures with ChBM-derived CD34(+) cells showed the lowest level of expansion of megakaryocytes and gave rise to more profound formation of myeloid and monocytic cells. In cultures with BM- or PB-derived cells, presence of IL-3 reduced the number of immature megakaryocytes (CD34(+)CD41(+) cells). However, in CB cultures, the number of CD34(+)CD41(+) cells was highest in cultures with Tpo + IL-3. Overall, cultures with CB CD34(+) cells yielded the highest number of megakaryocytes, but these cells showed reduced ploidization and lower level of CD41 expression, suggesting less maturation.
CONCLUSIONS: Each of the different CD34(+) cell sources responded differently to cytokine stimulation. For PB and ABM, the cytokine combination Tpo + IL-1 is most suitable to obtain high numbers of both immature and mature megakaryocytes for transfusion purposes. For CB, Tpo + IL-3 is better.