The Promise of Somatic Cell Nuclear Transfer (SCNT)
What is cloning and why are researchers pursuing this area of stem cell research?
Answer: This is a confusing terminology that gets distorted. Cloning has been called by several names: cloning, therapeutic cloning and somatic cell nuclear transfer (SCNT). All of these terminologies are the same. Cloning takes an unfertilized egg and under artificial conditions, the nucleus (the portion of the cell that contains the genetic material) is removed and replaced with the nucleus of cell that typically comes from an adult donor. The new cell receives a jolt of electricity and an artificially created embryo is formed. The resulting embryo can be implanted into the uterus to create an offspring and the process is called reproductive cloning. This process is what created Dolly the sheep, which took 277 attempts to achieve. Alternatively, if the embryo is destroyed to remove the stem cells the process is called therapeutic cloning. The process is very inefficient, requires many eggs and, more importantly, therapeutic cloning has not been well established in humans or in experimental animal models. Scientists are interested in cloning in order to overcome the tissue rejection of embryonic stem cells. Embryonic stem cells derived from discarded embryos from in vitro fertilization clinics would result in a tissue rejection and would require a patient to take anti-rejection medications to prevent the foreign tissue from being rejected. Such medications carry a risk of lowering a patient's immune system and making them vulnerable to an infection. The main goal of cloning would be to reduce the possibility of tissue rejection by using the genetic material of the donor who would ultimately be the recipient of the stem cell therapy.
Scientists at the Oregon Health and Science University recently accomplished human cloning. This has created a renewed interest among some scientist to pursue human cloning.