Has Human Cloning Really Arrived?

I. The Aim of Cloning Human Embryos: Does it Serve its Purpose?

Advanced Cell Technology (ACT), in Worcester, Massachusetts, claims that it is pursuing human cloning for therapeutic, and not reproductive reasons. They state that their intention is not to make a baby, but to develop a way of obtaining embryonic stem cells matched to patients. Their method calls for transferring genes from a patient into an experimental embryo and generating new cells that can be put back into the patient without causing an immune reaction.

One of the fist steps in this "therapeutic cloning" process is the production of human embryos that can be mined for stem cells. Stem cells are the "master" cells that have the ability to form nearly all the body's tissue. Many scientists believe that if the development of these cells can be carefully controlled, they could be used to replace the failing cells that cause degenerative diseases such as Parkinson's, stroke or diabetes. They theorize that since the transplanted cells would be derived from a patient's own clone, they would be less likely to be rejected by the patient's immune system.

However, all this may not be possible for many years - if at all. In the experiments detailed by ACT the researchers were never able to isolate the all-important stem cells in any of the embryos they created.

II. Methods of Producing the First Human Embryo Clones

(1) Nuclear Transfer

Jose Cibelli and his colleagues made their first human clone on October 13th, 2001. They used eggs from female volunteers in the Boston area. These women were all aged between 24 and 32, and had at least one child. The researchers injected the donated eggs - which had the nuclei removed - with the genetic material taken from the nuclei of cumulus cells. Cumulus cells are the tiny clouds of support cells that surround and nourish a developing egg in the ovaries. This is how the world's first mice clones were made and the technique differs slightly from the one that produced Dolly the sheep. Nuclear transfer was pioneered at the University of Hawaii.

ACT says it actually produced three clones using the Hawaii method and that it took 71 eggs to make the first clone. Their report showed that two eggs divided to form early embryos of four cells, and one progressed to at least six cells before growth stopped.

(2) Parthenogenesis or "Virgin Birth"

In parthenogenesis, egg cells start to divide and form embryos; even through they have not been fertilized by a sperm, or been enucleated and injected with the genetic material from a donor cell as in "traditional" cloning. In laymen's terms, it is basically a "virgin" birth. Technically, it is called parthenogenesis.

There are two kinds of parthenogenesis - natural and artificial. Natural parthenogenesis has been observed in many lower animals, especially insects such as aphids. In many social insects, like the honeybee and the ant, parthenogenesis gives rise to male drones. Fertilized eggs produce female workers and queens. However, no higher animals reproduce this way.

Artificial parthenogenesis does not naturally occur in nature. It has been induced in frogs and snakes, although it quite often results in abnormal development. Researchers have also reported that they have promoted eggs from mice and rabbits to divide into embryos by exposing them to chemicals. As early as 1983, scientists demonstrated that stem cells isolated from parthenogenetic mouse embryos could form a variety of tissue, including nerve and muscle.

Parthenogenetic Human Embryos

In ACT's parthenogenesis experiments, 22 human eggs were exposed to chemical activation. If the human egg cell were to develop into an embryo without the addition of any genetic material from a sperm cell it would be a clone of the mother. After five days of growing in culture dishes, six eggs had developed into blastocoele cavities. This means the embryo has developed an inner and outer group of cells - the inner cells are the potential source of embryonic stem cells that can be grown into replacement tissues and organs to treat degenerative diseases.

• Theoretical Use

The ACT scientists suggest that one way this technique could be used would be for a woman with heart disease to have her own egg cells collected and activated in the laboratory to produce stem cells. The stem cells could then be implanted back into the woman to patch up the diseased area of the heart.

• Ethical Dilemmas

There are, however, ethical dilemmas in using this method. Because parthenogenesis would involve female egg cell manipulation with no additional genetic materials, some scientists believe that it is a more ethically acceptable method of producing stem cells than the conventional transfer of nuclear DNA material from another person. Others, however, still think that it is still just another example of science going too far.

III. Producing the Human Clone… A Success?

Despite all their good intentions, ACT scientists are still far from producing genetically matched stem cells for sick patients. Ian Wilmut, one of the scientists that produced Dolly the sheep clone, even doubted whether the evidence produced in ACT's scientific paper amounted to proof that cloning had actually taken place. He said a human embryo is expected to double its number of cells every 24 hours, but even ACT's most developed embryo had not done this. "The furthest it got was to have six cells, at a time it should have had 60, so it had already died."

This was also the position taken up by John Gearhart, of Johns Hopkins University, who was one of the first scientists to isolate and maintain human embryonic stem cells in the lab. "They are promoting this very hard as a scientific advance based on a very preliminary and unconvincing evidence. And I think that from that standpoint it should not have been published."

The fact that the embryos died so early in development suggests that the inserted nucleus was not working properly, says developmental biologist John Eppig of the Jackson Laboratory in Bar Harbor, Maine. In normal human embryos, the nucleus begins to express its genes between the four and eight-cell stages. The embryos' failure to survive to eight cells "strongly suggests that you are not getting gene activation" in the transferred nucleus, he says. "And if you are not getting that, what have you got? Nothing."

Sources:

• Cibelli, Jose; Kiessling, Ann; Cunniff, Kerrianne; Richards, Charlotte: Lanze, Robert and West, Michael. "Somatic Cell Nuclear Transfer In Human: Pronuclear And Early Embryonic Development." The Journal of Regenerative Medicine. 2: 25-31.
• Marshall, Eliot. "Human Embryo Cloned." Science. November 26, 2001.
• Pearson, Helen. "Human Clone Not Miracle Cure" Nature. November 27, 2001.
• Sawahel, Wagdy. "Human Genetic Engineering." Academy of Scientific Research and Technology. Egypt: Cairo.
• Sawahel, Wagdy. "Genetic Engineering Revolution." Kuwait Foundation for the Advancement of Science. 1999.
• Sawahel, Wagdy. "Genetic Engineering: From A To Z." Daya Publishing House. India: New Delhi . 1998.

Wagdy A. Sawahel is a professor of gene technology at Vienna Bio-Center, Austria, the general editor of "International Series of Genetic Engineering & Biotechnology", and the author of the first Arabic encyclopedia in genetic engineering. He has received converted scientific awards and honors such as the Third World Academy of Science's prize in Biological Sciences. If you have any question about genetic engineering technology, please feel free to contact him at SAWAHEL@gem.univie.ac.at