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What is Parthenogenesis? Applications of Parthenogenetic Stem Cells

BY: Padma Kumar | Category: Stem-Cells | Submitted: 2011-01-17 20:25:33
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Article Summary: "This article explains whether Parthenogenetic stem cells could be a viable alternative to embryonic stem cells. Parthnogenesis is a biological phenomenon entailing the process of initiating development of the embryo..."


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The question whether it is ethically correct to use human embryos to produce embryonic stem cells remains a bone of contention. There are strong arguments in support and against the use of human embryos----for what is reckoned ultimately as a research endeavor. That being the case, scientists have been looking at other methods to obtain stem cells.

Currently there are three methods to get pluripotent stem cells in primates excluding Homo sapiens. a) From embryos obtained via in vitro fertilization; b) from adult tissues including bone marrow cells c) through parthenogenesis
This article will focus on parthenogenesis.

What is parthenogenesis

Parthnogenesis is a biological phenomenon entailing the process of initiating development of the embryo, without any contribution by the male of the species. In other words, the embryo is made primarily from the female oocyte without any contribution from the male. In parthenogenesis the egg starts developing as if it has already been fertilized keeping the two sets of chromosomes.

In lower organisms parthenogenesis is a fairly common method of reproduction --- examples being snakes, ants, fish, and birds. As regards these creatures, a single egg can develop without male contribution---and this process is parthenogenesis. Placental mammals do not have this type of reproduction.


Parthenogenesis in human context

In the human context the idea is to make an embryo with the full compliment of 46 chromosomes. This could be done by: a) by stimulating eggs which are diploid causing them to divide b) by causing an egg late in its maturation cycle with twenty three chromosomes to replicate genetic material. In that case a full complement of genes is obtained.

Perhaps the first instance of parthenogenetic cells in humans has resulted from the research efforts of Stemron Corporation led by David Wininger who succeeded in making parthenogenetic human embryos to the blastocyst stage from which stem cells could be sourced.


How is parthenogenesis different from cloning

In cloning, an enucleated egg cell is kept ready. Into this is put the nucleus of a diploid cell from a donor. The resulting cell is stimulated so that it undergoes continued mitosis. This results in an offspring that is genetically identical to the donor.

Parthenogenesis is totally different. It is based on the genetic material contained within the egg cell itself. The eggs that are subject to parthenogenesis could be either haploid or diploid depending on whether the eggs were produced by meiosis or mitosis oogenesis. So the outcomes could be different.


Examples of parthenogenesis

In nature there are several examples of parthenogenesis. Some types of sharks have produced offspring without male participation. Examples are the blacktip shark and the hammerhead shark. Another example is the Bdelloid rotifiers which have this asexual reproduction method.

Parthenogenesis as a means of reproduction can also be found in the following creatures:
* Crayfish
* Birds
* Reptiles
* Flies
* Ants
* Lizards
* Plant-lice (Aphides)
* Honey-bee

Applications of parthenogenesis

In parthogenesis also embryos are destroyed to make stem cells. But these embryos in any case could never have progressed to the birth stage. Therefore use of these embryos is not perceived to have ethical concerns unlike embryonic stem cell research.

That apart, theoretically if a defective gene has to be replaced then human parthenogenetic stem cells can be created and can be matched to the egg donor from the immunity aspect. In this regard, human parthenogenetic stem cell lines have been created by International Stem Cell Corporation (ISCO) from unfertilized human eggs. This is a patented technology and it does not have bad effects on the human embryo.

Parthenogenetic stem cells could be used to treat diseases such as:
• Huntington's disease
• Beta Thalessemia
• Tuberous sclerosis
• International Stem Cell Corporation has a range of skin care products using its proprietary Parthenogenic Stem Cells technology in combination with nanotechnology. The underlying basis of these formulations is that human parthenogenetic stem cells are reckoned to have beneficial effects on human skin cells especially anti-aging benefits and skin rejuvenation effects.
• Human Parthenogenic Stem Cells have been differentiated to cells for treatment of diabetes.
• Human Parthenogenic Stem Cells have also been used to make retinal cells to treat age related macular degeneration.
• Ultimately it will be possible to have parthogenic stem cell banks to meet individual needs.



Advantages


Mostly donor tissue is used in regenerative medicine. When that is not available embryonic stem cells are used as source for pluripotent cells. But for getting the embryonic stem cells embryos get destroyed. Destruction of embryos has ethical, political and legal limitations. But parthenogenesis (as egg can be turned into embryo without sperm) can be used for sourcing embryonic stem cells thus avoiding the ethical compulsions.

To make stem cells for an individual would be costly business but not so if parthenogenic stem cells banks were to be created.

In parthenogenesis the two sets of chromosomes are identical. This is unlike the normal practice when one set of chromosome comes from the father and the other from the mother. The cells produced this way will not cause unwanted immune reactions as the surface protein on the cells has less of variation.


Disadvantages

Parthenogenetic stem cells can only be made from eggs. Therefore it is not possible to make suitable stem cells in the case of women post menopause. On the contrary matching stem cells can be made for any person through therapeutic cloning.



Are there any ethical concerns in using this technique akin to obtaining embryonic stem cells

Human embryos have a moral locus standii in that it is reckoned as something that is coming to a life form. Even from the religious point of view, the moment from conception to birth is reckoned as a period of development of the human body and hence has a moral value attached to it.

But in the case of parthenogenic embryos it cannot be reckoned as a typical human embryo. The reason is, it cannot complete the birth process to be born as a human being unless combined with the outer cells of the early embryo (trophoblast cells) which could lead to placenta formation. In other words, the father's gene imprint is necessary for placenta formation. At the same time the parthenogenic embryos have the full complement of human DNA. Now the question is to decide if these embryos are rudiments of life just like normal human embryo. Are they of lesser human origin because they can't come to life by itself?

Even parthenogenic embryos have an ethical issue about it. Isn't this creating embryos designed for early death and hence by itself an ethically debatable event.

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Comments on this article: (8 comments so far)

Comment By Comment
Robert
2011-07-24 09:19:48 197
Hi. It seems to me that the product of parthenogenesis, the combination of two distinct genomes will result in a real girl and not a reduced entity?
Kate
2011-08-02 22:25:15 203
Under disadvantages there is no mention that the treatment wont benefit males, just that it wont be able to be used by woman post menopause.rnrnAm I missing something here or is there some form of DNA replacement (sperm into eggs) possible
Padma Kumar - Author
2011-08-11 06:41:43 208
Robert, I guess you shouldn't confuse the issues discussed in my article-----firstly, parthogenesis or "virgin birth" per se is not a normal form of reproduction in placental mammals (example, in cats, dogs, sheep, cattle and of course humans). Therefore, it is wrong to assume as yet that a combination would result in a "real girl" and so on in humans and other placental mammals, because that has never happened as far as I know. One should reckon with the fact that parthogenic embryos are different from normal human embryos because the former cannot complete the full gestation period to evolve as a human being. Secondly, the essence of my article was on the creation of parthogenic embryos from which embryonic stem cell lines (for research and other purposes) could be obtained. Why? Because such a possibility obviates the need for tinkering with a real human embryo and countering with the religious issues (Christians ,Hindus and some other religions may not deem it ethically correct). That apart, there are some advantages in using parthogenic embryos to get embryonic stem cell lines in the context of regenerative medicine. But of course pathogenesis is a normal reproductive activity for flies, ants and so on. I hope I have answeredyour question.
cherry
2012-01-22 13:11:47 257
A question rather than a comment. Can stem cells be used to cure down syndrome??
Padma Kumar - Author
2012-01-29 18:59:47 260
At this point in time stem cells cannot be used to cure Down syndrome. But there are other possibilities. If not therapeutically, stem cells can be used for research modeling relating to the study of Down syndrome. For instance, stem cells could be cultured into tissues relevant to Down's syndrome. This affords study of the disease parameters at the test tube level with the intention of finding a cure. For example, researchers have discovered a molecular pathway that serves as a signaling mechanism for the production of glial cells. This molecular pathway could possibly serve as a therapeutic target relating to Down's syndrome . The protein Synaptojanin-1 is a key component of this pathway and is a vital factor in the production of glia which are brain cells that offer support and protection to the neurons. One of the characteristics of Down's syndrome is the overproduction of glia cells and this has a correlation to the level of Synaptojanin-1 (which is encoded in chromosome 21). So stem cells could be used to create a mouse model (as mouse do not have chromosome21) of the disease condition so that it could ultimately lead to development of medicines which could possibly fix the proliferation of glial cells as in Down's syndrome. Some research work in this direction is being carried out under the aegis of Anna and John J. Sie Foundation.of the pioneering
Padma Kumar - Author
2012-01-30 07:45:35 261
Correction: The last sentence of my earlier post in response to the question raised by "cherry" should read as follws. "Some pioneering research work in this direction is being carried out under the aegis of Anna and John J. Sie Foundation."
Gabrielle
2013-12-21 15:51:12 736
I have a question, not a comment. How common is it for an unfertilized egg to activate on its own inside a human body? I've been looking all over the internet for an answer to that question ever since I was doing a school project on parthenogenesis and I read that parthenotes could develop on their own inside human bodies and live for up to five days before dying and ever since then I've been freaking out thinking these things are inside me. What I'm really looking for is for someone to tell that it's actually really rare.
Padma Kumar - Author
2013-12-23 11:29:13 738
Your question is "how common is it for an unfertilized egg to activate on its own inside a human body?" It's fairly common occurrence within the human body. Some of these activated eggs may possibly reach the uterus but that's all can't develop to an embryo. They may get to the blastocyte stage with stem cells within and therefore for a woman upto her menopause stage----- this could even possibly be a source of stem-cells for any stem-cell therapies she may need!

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