Mice cloned from skin cells

Abstract

Adult stem cells represent unique populations of undifferentiated cells with self-renewal capacity. In many tissues, stem cells divide less often than their progeny. It has been widely speculated, but largely untested, that their undifferentiated and quiescent state may make stem cells more efficient as donors for cloning by nuclear transfer (NT). Here, we report the use of nuclei from hair follicle stem cells and other skin keratinocytes as NT donors. When keratinocyte stem cells (KSCs) were used as NT donors, 19 liveborn mice were obtained, 9 of which survived to adulthood. Embryonic keratinocytes and cumulus cells also gave rise to cloned mice. Although cloning efficiencies were similar (<6% per transferred blastocyst), success rates were consistently higher for males than for females. Adult keratinocyte stem cells were better NT donors than so-called transit amplifying (TA) keratinocytes in both sexes (1.6% vs. 0% in females and 5.4% vs. 2.8% in males). Our findings reveal skin as a source of readily accessible stem cells, the nuclei of which can be reprogrammed to the pluripotent state by exposure to the cytoplasm of unfertilized oocytes.adult stem cells ͉ embryos ͉ cloning ͉ keratinocyte ͉ nuclear transfer

Paradoxes of Aging

“…Yet evidence both supports and conflicts with the ROS theory of aging. 17 The predictions of the ROS theory do not fit numerous observations: [18][19][20][21][22] animals can be cloned from adult nuclei, 23,24 the accumulation of mutations does not reach significant levels to cause aging 25 and antioxidants do not prolong lifespan in clinical trials. 26,27 Conflicting evidence disproves the theory.…”

Epigenetic reprogramming and induced pluripotency

“…While NT experiments have clearly demonstrated that fully differentiated lymphocytes (Hochedlinger and Jaenisch, 2002a;Inoue et al, 2005) and neurons (Eggan et al, 2004;Li et al, 2004) can be reprogrammed into pluripotent ES cells, these experiments did not exclude the possibility that adult stem cells were the selective donors in most successful cloning experiments. In agreement with this idea, neural stem cells (NSCs) and keratinocyte stem cells give rise to cloned mice with greater efficiency than do mature fibroblasts, epidermal transit amplifying cells, or neurons (Blelloch et al, 2006;Eggan et al, 2004;Li et al, 2007;Li et al, 2004;Wakayama and Yanagimachi, 1999). By contrast, experiments in the hematopoietic system suggest that differentiated granulocytes are more efficient donors for NT than are hematopoietic stem cells Sung et al, 2006), although these experiments have recently been challenged .…”

High-efficiency somatic reprogramming induced by intact MII oocytes

“…Several features could be responsible for the enhanced reprogramming capability of intact MII oocytes. First, the overall inefficiency of NT could be attributable to technical difficulties in nuclear isolation and transfer [20], and direct injection of somatic nuclei into intact oocytes could reduce enucleation trauma to the oocytes. Second, the oocyte nucleus, which supports preimplantation development of the parthenogenetic embryo, could help maintain normal cell division of the reconstructed embryo containing the somatic nucleus.…”