Therapeutic cloning is cloning that is performed for the purpose of medical treatment. It could theoretically be used to grow a replacement organ, for example, to generate skin for a burn victim, or to create nerve cells for someone suffering from brain damage or a neurological condition. The process is closely related to reproductive cloning, in which a copy of an organism is produced, but the two have very different end goals.
Formally, this type of cloning is called somatic cell nuclear transfer. It involves extracting the nucleus of a cell, and putting it into an egg that has had its nucleus removed. The egg is then allowed to divide and grow. In therapeutic cloning, the growing egg is used as a source of stem cells, which are undifferentiated cells that can grow into a wide variety of different types of cells. In reproductive cloning, the egg is allowed to grow into a baby.
The advantage to this type of cloning in medical treatment is that it would allow medical professionals to grow replacements for missing and damaged body parts for their patients. This would eliminate organ and tissue shortages, ensuring that every patient who required something like a new liver or new kidneys could get what he or she needed. Using cloned body parts would also eliminate the need for immunosuppressive drugs, and reduce the risk of rejection and other problems that are commonly associated with transplants.
In addition to being used for conventional transplant medicine, therapeutic cloning has far-reaching potential applications. For example, cloning research on mice has suggested that new nerve cells can be grown with reproductive cloning techniques and used to repair damaged brains, an application that could be useful for people with dementia, Alzheimer's disease, or strokes. It could also potentially be used to produce replacement limbs and in a variety of other therapeutic applications. Using recombinant DNA technology, scientists could even create customized biological material.
There are some ethical concerns with cloning, including that used for therapeutic purposes. For people who believe that life begins at the time of conception, the product of somatic cell nuclear transfer could be viewed as a human life, and choosing to cultivate stem cells from that egg would be a questionable ethical decision. For people who do not share these beliefs, many types of cloning are still fraught with ethical problems, ranging from questions about how accessible such techniques are to the general public to concerns that problems might arise with cloned tissue, which will only be apparent after years of use.