Granulocyte/Macrophage Colony-Forming Units from Cord Blood of Premature and Full-Term Neonates: Its Role in Ontogeny of Human Hemopoiesis

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Abstract
It is still uncertain whether the yolk sac is the only origin of hemopoietic stem cells during fetal development. We studied the level of circulating granulocyte/macrophage colony-forming unit (CFU-GM) from the 23rd week of gestation to fullterm, trying to delineate its role in the ontogeny of human hemopoiesis. Cord blood samples were collected from 45 healthy premature neonates and 91 healthy full-term neonates. CFU-GM assays were performed using a single agar layer system with human placental conditioned medium as a source of colony stimulating activity. The mean numbers of colonies produced from the cord blood samples of the premature and full-term neonates were 116 ± 185 (SD) and 96 ± 113/2 × 105 mononuclear cells, respectively. There was no statistical difference between the numbers of colonies of the two groups (Mann-Whitney test, p > 0.05). These results indicate that the level of circulating CFU-GM from the 23rd week of gestation to full term is constantly high and add credence to the assumption that CFU-GM are produced not only from the yolk sac but also from other hemopoietic sites.