C-Fos Messenger-Rna Constitutive Expression by Mature Human Megakaryocytes

By in situ hybridization with a c-fos probe, we have shown that human bone marrow megakaryocytes cultured in the presence of 20% aplastic anemia plasma constitutively express c-fos mRNA. At day 0, megakaryocytes are mostly immature and only 3% of them are labeled. The number of labeled cells reached 23% after 12 days of culture. Interleukin 3 (IL-3) and IL-6 added together at day 10 further increased this number to 31% 2 days later. Mature labeled megakaryocytes were more numerous and more strongly labeled than immature ones. These results suggest that c-fos could play a role in megakaryocytic terminal differentiation, either in the polyploidization or in the thrombopoietic function unique to these cells

Purification and Release From Quiescence of Umbilical-Cord Blood Early Progenitors Reveal Their Potential to Engraft Adults

Steel factor (SF) increases the frequency of colony formation by CD34(+) CD38(-) cycling cells, but it does not reverse the effect of an autocrine production of transforming growth factor (TGF)-beta(1) by early progenitors of the stem cell compartment. We have used optimal culture conditions supplemented with SF and anti-TGF-beta serum to estimate the proliferative capacity and ability to generate early progenitors in long-term cultures of bone marrow and umbilical cord blood cells. We estimate that the CD34(+) CD38(-) cells from a typical umbilical cord blood sample produce equivalent numbers of granulocyte erythrocyte macrophage megakaryocyte colony-forming units (CFU), twice as many granulocyte-macrophage (GM) CFU, and three times as many erythroid burst-forming units as the same population from an average bone marrow sample used in adult transplantation. These results suggest that umbilical cord blood is a suitable source of cells for adult transplantation