Abstract
Megakaryocytic progenitor cells with different radiosensitivity are detected in normal human peripheral blood (PB). CD34+ cells were purified by two and three isolation columns (i.e., CD34+(low) cells and CD34+(high) cells). Their purities were 74.8% and 88.8%, indicating a statistical significant difference. Thrombopoietin (TPO) supported 80.2 colonies per 1,000 CD34+(low) cells, but CD34+(high) cells were 42.2 colonies. X-irradiated CD34+(high) cells stimulated with TPO alone showed an exponential survival curve, however, no colonies were observed at dose over 4Gy. In the case of CD34+(low) cells, there were a few colonies also at 5Gy. TPO plus interleukin-3, which supports maximum radioprotection (Kashiwakura, Radiat Res 158, 202, 2002), showed that no significant differences in the survival curves between the both cells were observed. These findings suggest that different radiosensitivity observed in the both cells were depending on the differentiation pathway of CD34+ cells. Especially, there is a possibility that the expressions of Mpl receptor on the surface of CD34+ cells are different. [J Radiat Res 44:406 (2003)]
