Parthogenesis - An Alternative to Cloning?

Stem cells are the holy grail of modern biology. These root cells can, with proper stimulation, be used to produce virtually any type of cell in the body. Until now, the best source of stem cells has been human embryos. These have typically been obtained from fertility clinics. Considerable research is also underway to clone stem cells derived from non-embryonic tissue. The possibility of deriving stem cells from nonviable, asexually produced blastocysts might solve, at least for some, the ethical debate currently raging on the direction of therapeutic stem cell research. The other problem with present human ES cell technology is the critical problem of histocompatibility as the cells obtained from embryos derived during in vitro fertilization procedures, or from foetal sources, are essentially cells from another individual (allogeneic). This means that they, or any cells made from them, would be at risk of being rejected if transplanted into a human being. To solve this problem, the biotechnology industry is trying to manufacture embryonic cells identical to a human adult, this is to say, autologous embryonic cells. To do this one of the following methods will eventually certainly have to be employed and recent research shows that parthenogenesis might not only be pssible but less ethically controversial.

(1) Somatic Cell Nuclear Transfer: In this technique, commonly known as "Human Therapeutic Cloning" a patient's body cell is combined with an egg cell that has its DNA removed. As a result the body cell's DNA is reprogrammed back to an embryonic state, and totipotent stem cells are produced identical to the patient.

(2) Ooplasmic Transfer: In the reverse of nuclear transfer, ooplasmic transfer involves the removal of the cytoplasm of an oocyte and transferring it into the body cell of a patient thereby transforming the patient's cell into a primitive stem cell.

(3) Parthenogenesis: In this technique a woman's oocyte is directly activated without the removal of its DNA to begin development on its own, forming a preimplantation embryo from which totipotent stem cells are isolated.

Tell us more about the technique of parthenogenesis, which appears to both reduce transplantation problems and possibly be less controversial:

Parthenogenesis is derived from the Greek words for 'virgin birth'. In modern biology, it refers to a form of reproduction in which an ovum develops into a new individual without having been fertilised. In many social insects, such as the honeybee and the ant, the unfertilised eggs give rise to the male drones and the fertilized eggs to the female workers and queens. Charles Bonnet discovered the phenomenon of parthenogenesis in the 18th century. In 1900, biologists were able to encourage artificial parthenogenesis in some species. Jacques Loeb reported in that year that he was able to induce unfertilised frog eggs to grow by scratching them with a needle. Since that time various chemical and mechanical means have been used to produce artificial parthenogenesis in numerous animals including rabbits. However, in most cases the resulting developments abnormal.

In 1936, Gregory Pincus induced parthenogenesis in mammalian (rabbit) eggs by temperature change and chemical agents. No successful experiments with human parthenogenesis have been reported. The phenomenon is rarer among plants (where it is called parthenocarpy) than among animals. Unusual patterns of heredity can occur in parthenogenesis organisms and offspring produced by some types are identical in all inherited respects to the mother. While the ancient Greeks may have been mystified by many elements of molecular biology, they would have easily been able to grasp parthenogenesis, a concept rooted in their oldest myths. Athena, daughter of Zeus, was among the most important of the Greek deities. The Parthenon is the name of the temple of Athena on the Acropolis. She was the patron goddess of Athens, and was associated with everything from warfare and urban development to fertility and weaving. The birth of Athena was most unusual. Those classical scholars amongst you will probably recall that Zeus swallowed his first wife Thetis when she became pregnant, because he feared that she would bear him a son would steal his throne. After a few months he developed a severe headache and he went to his fellow god Hephaestus who history declares was good enough to split his head open with an axe. It is documented that Athena then emerged fully-grown and wearing a suit of armour, from the head of Zeus.

Would parthenogenesis really be ethically acceptable?

The parthenogenetic creation of primate embryos with subsequent production of stem cells suggests a new, perhaps somewhat less ethically controversial direction in research aimed at treating human diseases with stem cell-derived therapies. There is no doubt that the Catholic Church would denounce it on the basis of two couples not being involved in the creation of the initial embryo but they would have certain difficulties explaining when exactly a life force actually entered the cell to make it a potential human being. This would become more difficult if human parthenogenesis was found to occur by some simple method such as heating or electrifying the cell, which is one of the reasons that I maintain that life is a continium. Anyway, it is now known that a team of scientists from Mayo Clinic, Sloan Kettering Cancer Centre and Wake Forest University working with a Massachusetts biotechnology company recently managed to create primate embryos parthenogenetically. The research involved stimulating a monkey egg to grow without any help from sperm. The researchers used chemicals to signal the eggs not to eject half of their chromosomes (as they would do in sexual reproduction) and command the eggs to start dividing. In this case the resulting mass of 100 or so cells, known as the blastocyst, cannot become a viable organism when produced with the new technique. Four of 28 parthogenetic eggs developed into blastocysts. The researchers were able to derive a single stem cell line from one of the blastocysts.

Moreover, they were able to tease stem cells derived from the asexually derived embryos to produce numerous types of cells including brain, heart and smooth muscle cells. A particularly promising development was the report that the researchers were also able to produce midbrain dopamine neurons, with the hope is that some day such cells could replace dysfunctional cells in the brains of patients with central nervous disorders such as Parkinson's disease and Huntington's disease. This study suggests an alternative to human therapeutic cloning as differentiated cell types derived in vitro by parthenogenesis eliminate the requirement to produce or disaggregate a normal, competent embryo and may circumvent the ethical concerns voiced by some, positively impacting the debate in stem cell research," the researchers noted in Science.

How long will it be before human parthenogenesis is achieved?

Researchers from the same biotech company that supported the current research, Advanced Cell Technologies, created considerable controversy in November of last year when they announced they had cloned human embryos. The embryos had not grown beyond six cells and had not produced stem cells. While the race is on to create parthenogenetic human embryos, considerable doubts remain regarding the safety and efficacy of this approach. Researchers believe that the male DNA that mixes with the females DNA in the egg probably has an important role to play in gene activation in at least some kinds of stem cells. For example, studies in mice produced parthenogenetically suggest that those stem cells differentiate more readily into neurons than into other cell types such a muscle. The hypothesis that such cells would indeed be immune-privileged also remains unproven.

Dr. Patrick Treacy is Medical Director of Ailesbury Clinics Ltd and the Cosmetic Medical Group. He is also Medical Director of OnboardSpa Ltd. He is Chairman of the Irish Association of Cosmetic Doctors and is Irish Regional Representative of the British Association of Cosmetic Doctors. He is European Medical Advisor to Network Lipolysis and the UK's largest cosmetic website Consulting Rooms. He practices cosmetic medicine in his clinics in Dublin, Cork, London and the Middle East.

He was amongst the first doctors worldwide to use the permanent facial endoprosthesis BioAlcamid for HIV Lipodystrophy patients. He was also the first person to introduce many techniques such as Radiofrequency assisted lasers, Fibroblast transplant and Contour Threads to Irish patients.

Dr. Treacy is an advanced aesthetic trainer and has trained over 300 doctors and nurses from around the world. He is also a renowned international guest speaker and features regularly on national television and radio programmes. He was invited to speak about stem cells and cosmetic medicine at the World Aesthetic Conference in Moscow this year.

The Irish College of Cosmetic Doctors
The British Association of Cosmetic Doctors
The British Medical Laser Association
The American Society for Aesthetic Medicine
The American Society for Lasers in Medicine and Surgery
The European Society of Laser Dermatology
The European Society for Dermatological Surgery (ESDS)
The International Society for Dermatologic Surgery
The International Academy of Cosmetic Dermatology

Dr. Treacy is the European Representative for the NetWork-Lipolysis where he is on the Medical Advisory Board and the Scientific Advisory Board.
Ailesbury Clinics Ltd Suite 6 Merrion Road Ailesbury Road Dublin 4 Ireland
Ailesbury Clinic Cosmetics Surgery Phone +35312692255/2133 Fax +35312692250