Therapeutic cloning uses a process known as somatic cell nuclear transplant (nucleus replacement, exploratory cloning, and embryo cloning), which involves removing an egg (oocyte) from which the nucleus has been removed and replacing that nucleus with DNA from another organism. After many mitotic culture divisions (culture mitoses), the cell forms a blastocyst (an early stage of the embryo consisting of approximately 100 cells) with DNA almost identical to the primary organism.
The purpose of this procedure is to obtain stem cells that are genetically compatible with the donor organism. For example, embryonic stem cells can be obtained from the DNA of a patient with Parkinson’s disease, which can be used to treat it, while they will not be rejected by the patient’s immune system.
Stem cells obtained by therapeutic cloning are used to treat many diseases. In addition, a number of methods using them are currently under development (treatment of some types of blindness, spinal cord injuries, Parkinson’s disease, etc.)
This method often causes controversy in the scientific environment, the term describing the created blastocyst is called into question. Some believe that it is incorrect to call it a blastocyst or an embryo since it was not created by fertilization, but others argue that under appropriate conditions, a fetus can develop from it, and, ultimately, a child – therefore it is more appropriate to call the result an embryo.
The potential for therapeutic cloning in the medical field is enormous. Some opponents of therapeutic cloning argue against the fact that this procedure uses human embryos while destroying them. To others, it seems that such an approach instrumentalizes human life or that it will be difficult to allow therapeutic cloning without allowing reproductive cloning.
According to data from 2006, cloning for therapeutic purposes is used in the UK, Belgium and Sweden. Research in this area is permitted in Japan, Singapore, Israel and Korea.
In the UK, therapeutic cloning is authorized for research purposes and is included in the Human Fertilization and Embryology Act in 2001.
In many other countries, therapeutic cloning is prohibited, although laws are constantly debated and changed. On December 8, 2003, UN countries voted against the prohibition on reproductive and therapeutic cloning proposed by Costa Rica.