Hybrid embryos as a source of embrionic stem cells

The HFEA (Human Fertilisations & Embryology Authority) recently accepted to perform research in hybrid embryos generated by transferring human somatic cell nucleus to cow enucleated oocytes, named cytoplasmatic hybrids. The aim is to obtain a source of embryonic stem cells without the use of human oocytes. The arguments for the approval are to avoid the risk of obtaining human oocytes and that these embryos will not be transferred to a female's womb for its development. Those who oppose the technique argue that it is a manipulation of the beginning of life and a disrespect to the dignity of human life because of the destruction of embryos. Nevertheless, the real nature of this new entity has not been established. Biologically it is an embryo with 99% of human genome and animal's cytoplasm, not generated from human gametes, it is not a new genome and it will be used only to cultivate stem cells. It does not seem possible to define its nature beyond any doubts. If it were considered as a human embryo it should be respected and protected as every human being. Once more, scientific progress opens new ethical and legal questions that we cannot answer in a definitive way. Researchers are exploring new roads to obtain pluripotential stem cells which should favor the development of innovative therapies. The main objection is the unavoidable destruction of human embryos, although in this case its origin and nature are not clear. © 2008 Sociedad Médica de Santiago.