An HLG professor makes the complicated procedure simple
By Donald R. Colborn, Ph.D.
March 10, 2005
HANNIBAL – Somatic Cell Nuclear Transfer (SCNT), or therapeutic cloning as it is commonly known, is a procedure utilized to produce cells that can be implanted in the patient with the goal of replacing cells damaged by injury or disease.
While this procedure is relatively new in humans, the technique was first utilized in the 1960s in frogs. Researchers used nuclear transfer to test the ability of DNA to form a complete adult frog from DNA extracted from epithelial cells taken from the gut of frogs. In these experiments, the nucleus and the DNA it contained were removed from epithelial cells and placed into an egg that had its own nucleus removed (enucleated). Following incubation of this new cell, the researchers were able to produce normal frogs. A few years later, these same techniques were used to create Dolly, the famous cloned sheep.
This same basic approach is used today. In SCNT, somatic cells are removed from the patient. Somatic cells are cells of the body that contain the full complement of 46 chromosomes common to all humans. Somatic cells are different from the sex cells that are responsible for normal fertilization because the sex cells only contain 23 chromosomes. The nucleus and DNA of the somatic cells are removed and transplanted into an enucleated egg that has been donated by another individual. This insures that all genetic information in the developing embryo is from the patient.
Upon creation of this newly formed embryo, the original cell begins to divide and produce additional cells that have yet to differentiate into specialized cells of muscles, nerves, bones, skin or any of the other cell types necessary for normal human formation. It is these undifferentiated cells known as stem cells that are the desired cell types. These cells are said to be pluripotent. This means that they have the potential to differentiate into all the various types of cells of the body. These cells can then be implanted into the original patient, and since the cells contain only his DNA, the chance of rejection by the immune system is minimal. It is thought that these undifferentiated stem cells can be coaxed into forming and replacing the types of cells that are damaged in the patient, thereby correcting the original affliction.
Some of the diseases that are current candidates for this type of stem cell replacement are Parkinson’s, Alzheimer’s, and spinal cord injuries. This is where the therapeutic aspect comes from because these cells are allegedly being used as part of a treatment therapy for patients with these and other diseases.
This leads to the question of what exactly has been created during SCNT.
Technically, the original cell created after insertion of the DNA is not fertilized because it did not involve the sex cells associated with the traditional method of fertilization. However, does this mean that it is no less human? It contains all the genetic information present in any other cell of the individual from which the original somatic cells were taken. It has the ability to divide and create new cells and could potentially develop into a clone of the original person if this embryo was not prematurely destroyed in order to harvest the stem cells. All that is needed is the time necessary for normal development to occur and a proper place for implantation.
Was Dolly any less a sheep because she developed from a non-fertilized nuclear transplanted embryo? It is claimed by some who support SCNT that this newly created embryo is not capable of forming a human. However, this has occurred in other species, including frogs, mice and sheep, so one must be open to the possibility that it could be done in humans. With further experimentation, it is entirely possible that these cloned embryos could in fact develop into a normal human fetus.
Most people express strong opposition to cloning of humans but have little difficulty in supporting therapeutic cloning. Perhaps it is the therapeutic nature of the technique that causes people to overlook the obvious negatives of this procedure. Few people could find fault in allowing research that is alleged to have the potential to treat people with a wide variety of debilitating medical conditions. But at what cost are we willing to pursue this line of research?
Once this technology is fully developed, it becomes impossible to control it in the global arena. As long as there is a profit motive for using these techniques for purposes other than purely therapeutic, there will be those willing to exploit it for their financial advantage. It may very well prove to be that therapeutic cloning will serve as a back door entrance for the widespread development of human cloning. (Donald R. Colborn, associate professor of biology at Hannibal LaGrange College, holds bachelor’s and master’s degrees from the University of Missouri and a Ph.D. from Lousiana State University.)