ABSTRACT
INTRODUCTION The debates in the society about the ethics of using leftover IVF embryos for derivation of embryonic stem (ES) cell lines have been going on for years. ES cells, first derived in 1981 by Evans and Kaufman (1), have been studied extensively as a model of mammalian development and differentiation. Isolation of human ES (hES) cells from leftover IVF embryos in 1998 (2) has boosted the research in this field, leading to great hopes for cell therapies. ES cells, the progeny of the inner cell mass (ICM) of a blastocyst, remain pluripotent, maintain normal karyotype through multiple passages in culture, and can differentiate into derivatives of all three germ layers in vitro and in vivo (4,5). Among their differentiation derivatives that can be produced in vitro are such sought-after cells as cardiomyocytes, neurons, oligodendrocytes, retinal pigment epithelium, insulin-producing cells, and others (4,6-11). Such cells and tissues, if robustly produced from ES cells, would satisfy an unmet medical need for tissue and organ repair and could be generated to decrease the risk of immune rejection either through banking a variety of genetically diverse cell lines or via patient-specific technologies.
