ABSTRACT
Although recent evidences indicate that the adult human heart has a limited capacity for regeneration in physiological and pathological conditions (Becker et al. 1974; Fukuda and Yuasa 2006; Yuasa et al. 2004; Beltrami et al. 2001; Bergmann et al. 2009), the mechanisms of regeneration remain unknown and it continues to be diffi cult to control cardiac regeneration in diseased human heart (Yuasa and Fukuda 2008a,b). For cardiac regenerative medicine using cell replacement therapy to become a viable option, which of the stem cells is most suitable (i.e., embryonic stem (ES) or somatic stem cells) needs to be determined at fi rst. Thus far, there is no clear consensus as to which is better, because each has its own advantages and disadvantages. Somatic stem cells can be obtained from adult tissues with less ethical problems; autologous somatic stem cells don’t have immunological problems after transplantation. But its proliferative capacity and differentiation ability is limiting compared to those of ES cells. Although ES cells are promising pluripotent cells with a strong proliferative capacity and multi-potency, there are ethical considerations that constrain the use (and destruction) of early human embryos to establish new human ES
Cardiology Division, Department of Internal Medicine; Center for Integrated Medical Research, Keio University School of Medicine Email: yuasa@a8.keio.jp
cells; furthermore, the ES cells do not display the autologous genotype of the patients in whom they are to be used, which suggests that we have to take immunosuppressive drugs after cell-transplantation (Evans and Kaufman 1981). In an attempt to overcome these problems and yet maintain pluripotent stem cell characteristics, many studies had investigated various techniques, such as cell fusion and somatic nuclear transplantation; however, as yet, none has progressed to successful clinical application (Cowan et al. 2005; Wilmut et al. 1997).
