1. From the Division of Hematopoiesis, Research Center for Regenerative Medicine, Tokai University School of Medicine, Isehara, Kanagawa; the Department of Hematology, Tokai University School of Medicine, Isehara, Kanagawa; the Central Institute for Experimental Animals, Kawasaki, Kanagawa; the BioResource Center, RIKEN Tsukuba Institute, Tsukuba, Ibaraki; and the Department of Cell Transplantation & Regenerative Medicine, Tokai University School of Medicine, Isehara, Kanagawa, Japan.