New Advances in iPS Cell Research Do Not Obviate the Need for Human Embryonic Stem Cells

Abstract

Recently three different studies were published demonstrating that mouse fibroblast (skin) cells can be directly reprogrammed to behave like embryonic stem cells (Okita et al., 2007; Wernig et al., 2007; Maherali et al., 2007). These studies advanced a breakthrough announced last year in which a quartet of genes (Oct-3/4, Sox2, c-Myc, and Klf4) were discovered to induce pluripotency in mouse cells, albeit incompletely (Takahashi and Yamanaka, 2006). Now a second generation of these induced pluripotent stem cells (called iPS cells) has been made to do almost everything mouse embryonic stem cells can do. When mouse iPS cells were injected into mouse blastocysts, they contributed to all tissue types in the resulting adult mice, including sperm and oocytes (Okita et al., 2007; Wernig et al., 2007; Maherali et al., 2007). And one research team produced fetal mice derived entirely from iPS cells-a key criterion for embryonic stem cells (Wernig et al., 2007). © 2007 Elsevier Inc. All rights reserved.