The Effects of (-)-Epigallocatechin-3-Gallate on the Proliferation and Differentiation of Human Megakaryocytic Progenitor Cells

Epigallocatechin-3-gallate (EGCg) has been widely recognized as a powerful antioxidant and free radical scavenger. The effects of EGCg on the proliferation and differentiation of X-irradiated megakaryocytic progenitor cells (colony-forming unit-megakaryocyte, CFU-Meg) using CD34+ cells prepared from human placental and umbilical cord blood have been shown. In the absence of exogenous thrombopoietin (TPO), no colonies are observed in cultures containing or lacking EGCg (1 nM-100 microM). In the presence of TPO, in contrast, EGCg significantly promotes CFU-Meg-derived colony formations within the 10-100-nM range. A 1.5-fold increase in the total number of CFU-Meg has been counted compared with the control. These favorable effects of EGCg are also observed in the culture of CD34+ cells before and after X irradiation with 2 Gy. Moreover, in order to investigate the function of EGCg promoting megakaryocytopoiesis and thrombopoiesis in ex vivo cultures, both non-irradiated and X-irradiated CD34+ cells are grown in liquid cultures supplemented with TPO. In both cultures, EGCg increases the total number of cells and megakaryocytes. It has been suggested that the favorable effects of EGCg reduce the risk factor from radiation damage in megakaryocytopoiesis.