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'iSCNT' -interspecies somatic cell nuclear transfer:Animal eggs sources for patient specific stem cells

Scientific research about stem cells continues to burgeon. One recently published research paper compares the reprogramming of human somatic nuclei using oocytes obtained from animal and human sources; their data calls into question the potential use of discordant animal oocyte sources to generate patient-specific stem cells.(1)
Press release 2/2/09:

[Advanced Cell Technology and its collaborators... demonstrated] that although human-to-human clones (human clones) and human-to-animal clones (hybrids) appear similar, the pattern of reprogramming of the donor human cell is dramatically different. In contrast to the human-animal hybrids, the gene expression pattern of the human clones was highly similar to normal human embryos.
Robert Lanza, MD, Chief Scientific Officer at ACT, and senior author of the study stated:
We examined the factors recently used to reprogram skin cells (to induce pluripotent stem cells). At the center of cellular reprogramming lies the activation of the transcription factors Oct4, Sox2, and nanog. These core factors were activated in both the normal and cloned human embryos. In striking contrast, the human-animal hybrids showed no difference or a down-regulation of these critical pluripotency genes −effectively silencing them—thus making the generation of stem cells impossible. Without appropriate reprogramming, these data call into question the potential use of animal egg sources to generate patient-specific stem cells. It also renders the moral controversy surrounding the use of human-animal hybrids mute....the study shows for the first time that the donor DNA in the cloned human embryos is extensively reprogrammed through extensive up-regulation ('turning on' of genes) with similar expression patterns to normal human embryos. Nearly all of the key differentially-expressed genes were activated in the human clones. In distinct contrast, the majority of these genes were down-regulated or silenced in the human-animal hybrids.

Previous studies have confirmed the ability of animal eggs to support interspecies cell division to the embryo stage, and in a few closely-related bovine species, successful development to term. However, there are clear differences in compatibility. Distantly-related animal combinations generally arrest at the cleavage-stage, although there have been reports of blastocyst formation. Our group and others have successfully used eggs to clone closely-related species (for instance, we cloned two endangered species – the guar and banteng − using cow eggs). Rabbit eggs have also been used to generate embryos using cells from cats and panda, among others. However, it remains unknown whether the DNA in the later combinations was fully reprogrammed. Importantly, except for a study carried out in China (which to-date has proven irreproducible despite attempts by numerous groups in the last half-decade), there is no evidence that patient-specific stem cells can be generated using animal eggs.

Due to the shortage of human donor eggs, cows, rabbits, and other animals have long been considered attractive surrogate sources of oocytes and egg cytopasm for SCNT.
(1)http://www.advancedcell.com/files/Cloned-Human-Embryos-Successfully-Reprogrammed-Using-Human.pdfThe research appears online ahead of print in the journal Cloning and Stem Cells doi:10.1089/clo.2009.0004.(Editor-in-Chief: Sir Ian Wilmut; published by Mary Ann Liebert, Inc.)
(2)http://www.advancedcell.com/press-release/Cloned-Human-Embryos-Successfully-Reprogrammed-Using-Human-Eggs Advanced Cell Technology, Inc. (ACT) is a biotechnology company applying cellular technology in the field of regenerative medicine.
For Reader's convenience, below find a few ISSCR FAQs on SCNT

From ISSCR 'FAQ"http://www.isscr.org/public/glossary.htm

11. Why are researchers interested in developing disease-specific or patient-specific pluripotent stem cells?
The development of patient-specific or disease-specific pluripotent stem cells has great therapeutic promise for three reasons. Firstly, these cells could provide a powerful new tool for studying the basis of human disease and for discovering new drugs. Secondly, the resulting embryonic stem cells could be developed into a needed cell type, and if transplanted into the original donor, would be recognized as 'self', thereby avoiding the problems of rejection and immunosuppression that occur with transplants from unrelated donors.
12. What is somatic cell nuclear transfer (SCNT)?
Somatic cell nuclear transfer (SCNT) is a technique in which the nucleus of a somatic cell, that is any cell of the body apart from the sperm or egg, is transferred into an egg that has had its original nucleus removed. The egg now has the same DNA, or genetic material, as the donor somatic cell. Given the right signals, the egg can be coaxed into developing as if it had been fertilized. The egg would divide to form 2 cells, then 4 cells, then 8 cells and so on until the blastocyst is formed. Embryonic stem cells can be derived from this blastocyst to create cell lines that are genetically identical to the donor somatic cell.
13. Why derive embryonic stem cell lines following somatic cell nuclear transfer (SCNT)?
The derivation of patient-specific human embryonic stem cell lines using this technique (see ‘What is somatic cell nuclear transfer?’) Firstly, these cells could provide a powerful new tool for studying the basis of human disease and for discovering new drugs. Secondly, the resulting embryonic stem cells could be developed into a needed cell type, and if transplanted into the original donor, would be recognized as 'self', thereby avoiding the problems of rejection and immunosuppression that occur with transplants from unrelated donors.
14. Can induced pluripotent cells replace research on embryonic stem cells or somatic cell nuclear transfer?
No. The derivation of human induced pluripotent stem cells opens up exciting new areas of stem cell research, however, this technology is at a very early stage and many fundamental questions remain. While iPS cells and embryonic stem cells share many characteristics they are not identical. The similarities and differences are still being explored.
Research on human embryonic stem cells, somatic cell nuclear transfer and ‘adult’ or tissue-specific stem cells needs to continue in parallel. All are part of a research effort that seeks to expand our knowledge of how cells function, what fails in the disease process, and how the first stages of human development occur. It is this combined knowledge that will ultimately generate safe and effective therapies.

http://www.isscr.org/public/faq.htm#12
From the ISSCR glossary:
Somatic cell nuclear transfer:A technique in which the nucleus of a somatic cell (any cell of the body except sperm cells and egg cells) is injected, or transfered, into an egg, that has had its nucleus removed. If the new egg is then implanted into the womb of an animal, an individual will be born that is a clone. The clone has the identical genetic material as the somatic cell, which supplied the nucleus that carries the genetic material. This procedure is very inefficient and was first developed for agricultural purposes. However, in human medicine, this technique can be used to isolate embryonic stem cells from eggs that have undergone nuclear transfer. When the somatic cell is supplied from the cells of a person, the stem cells isolated from the developing eggs can be used to make a tissue that will not be rejected by that person, because they have the same genetic material. In this way, 'customized' embryonic stem cells could be made for everyone who needed them.

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