Cloning and Stem Cell
Human embryonic stem cells are stem cells that are derived from the developing human embryo. They are most useful in research because of their ability to change into any type of cell, tissue or organ in the human body – that is, their pluripotency. As such they can be used in the treatment of a very large number of conditions. The main ethical issues arise from their source – donated embryos, most often left over from the IVF process.
Non-embryonic stem cells are stem cells that are not derived from an embryo. Two examples of these are cord-blood stem cells and induced pluripotent stem cells. Because they are not derived from embryos there is substantially less moral controversy about the use of these stems cells in research. However, there are limits to the use of non-embryonic stem cells. First, for all but induced pluripotent stem cells, other stem cells are not as versatile as the embryonic version and so they cannot give rise to the same range of human cells; and second, they do not help with research that is aimed at understanding the developmental mechanisms involved in these processes.
Admixed human embryos are a range of ‘combined’ human-animal embryonic cells. The most commonly used in research are ‘cybrids’. Cybrids are made by inserting the nucleus of a human cell into an animal egg from which the nucleus has been removed. They are useful in research because they are an easy way to create embryos so that the understanding and control of human embryos and development can be understood. Chimeras are usually formed by merging human and animal embryos whilst hybrids have human and animal chromosomes. The most common objection to these techniques involves claims about interfering with nature – by creating ‘half-human, half-animals’. A further objection points to the lack of dignity associated with the creation of these embryos. Such an objection relies on a particular conception of the moral status of the embryo.
Therapeutic cloning is cloning that is aimed at producing stem cells, tissue or organs for the therapeutic use of the individual from whom they are cloned. The advantage of therapeutic cloning is that the stem cells or other tissue created will have matched DNA to the recipient and so there will be little risk of tissue rejection. The main ethical issue associated with therapeutic cloning is that it requires the creation and destruction of an embryo, which on some views on the moral status of embryos is wrong.