Embryonic Stem Cells From Cloned Embryos Vs Induced Pluripotent Stem Cells: Let the Debate Begin


In May of 2013, Shoukhrat Mitalipov and his coworkers from the Oregon Health and Science University, reported the derivation of human embryonic stem cells from cloned human embryos. Other stem cell scientists have confirmed that Mitalipov’s protocol works as well as he says it does.

Mitalipov and others have also examined the genetic integrity of embryonic stem cells made from cloned human embryos and induced pluripotent stem cells made from mature adult cells through genetic engineering and cell culture techniques. This paper was published in Nature in June 2014 and used genetically matched sets of human Embryonic Stem cells made from embryos donated from in vitro fertilization clinics, induced Pluripotent Stem cells and nuclear transfer ES cells (NT-ES cells) derived by somatic cell nuclear transfer (SCNT). All three of these sets of stem cells were subjected to genome-wide analyses. These analyses sowed that both NT-ES cells and iPS cells derived from the same somatic cells contained comparable numbers of genetic variations. However, DNA methylation, a form of DNA modification for regulatory purposes and gene expression profiles of NT-ES cells corresponded closely to those of IVF ES cells. However, the gene expression provide of iPS cells differed from these other two cell types and iPS cells also retained residual DNA methylation patterns typical of the parental somatic cells. From this study, Mitalipov stated that “human somatic cells can be faithfully reprogrammed to pluripotency by SCNT (that means cloning) and are therefore ideal for cell replacement therapies.”

Now a new study by Dieter Egli of the New York Stem Cell Foundation (NYSCF) in New York City, which included Mitalipov as a collaborator, has failed to demonstrate significant genetic differences between iPS cells and NT-ES cells. This is significant because Eglin has long been a rather vigorous proponent of cloning to make patient-specific stem cells. Egli gave an oral preview of his forthcoming paper on October 22nd, at the NYSCF annual conference. Egli told his audience, “This means that all of you who are working on iPS cells are probably working with cells that are actually very good. So I have good news for you,” he told them, eliciting murmurs and chuckles. “What this exactly means for the SCNT program, I don’t know yet.”

Egli and colleagues used skin cells from two people—a newborn and an adult—to create both stem cells from cloned embryos (using donor eggs) and iPS cells. Then they compared the genomes of these two types of cell lines with the genomes of the original skin cells in terms of genetic mutations, changes in gene expression, and differences in DNA methylation. Both methods resulted in about 10 mutations compared with the average genome of the mature source cells. These changes didn’t necessarily happen during reprogramming, however, Egli says, since many of these mutations were likely present in the original skin cells, and some could have arisen during the handling of cells before they were reprogrammed.

Both types of stem cells also carried a similar amount of methylation changes. Overall, the method didn’t seem to matter, Egli and his team concluded. Because he is a longtime proponent of SCNT, Egli says it would have been “more attractive” to reveal significant differences between the two kinds of stem cells. “This is simply not what we found.”

Now it would be premature to conclude that iPS cells are as good as NT-ES cells for regenerative purposes, but this certainly seems to throw a monkey wrench in the cloning bandwagon. Cloning would be quite complicated and expensive and also requires young, fertile women to donate their eggs. These egg donors must undergo potentially risky procedures to donate their eggs. Jennifer Lahl’s documentary Eggsploitation provides just a few of some of the horror stories that some women experienced donating their eggs. The long-term effects of this procedure is simply not known and asking young women to do this and potentially compromise their health or future fertility seems beyond the pale to me.

Alternatively, iPS technology keeps improving and may come to the clinic sooner than we think. Also, is a cloned embryo essentially different from one made through IVF or “the old-fashioned way.?” This whole things seems to me to involved the creation of very young human beings just so that we can dismember them and use them as spare parts. Such a practice is barbaric in the extreme.

For those who are interested, please see chapters 18 and 19 of my book The Stem Cell Epistles to read more about this important topic.

Making Better Induced Pluripotent Stem Cells


On July 2nd of this year, a paper appeared in the journal Nature that performed complete genomic analyses of embryonic stem cells derived from embryos or cloned embryos, and induced pluripotent stem cells (iPSCs), which are made from reprogrammed adult cells.  They found that both embryonic stem cells made from cloned embryos and iPSCs derived from the same types of adult cells contained comparable numbers of newly introduced mutations.  However, when it came to the epigenetic modification of the genome (the small chemical tags attached to specific bases of DNA that gives the cell hints as to which genes to turn off), the epigenetic pattern of the embryonic stem cells made from cloned embryos more closely resembled that from embryonic stem cells.  The iPSCs still had some similarities with the adult cells from which they were derived whereas the embryonic stem cells made from cloned embryos were more completely reprogrammed.  From this the authors claimed that making embryonic stem cells by means of cloning is ideal for cell replacement therapies.

There is a big problem with this conclusion:  This was tried in animals and it did not work because of immunological rejection of the products from the stem cells.  For more information on this, see my book, The Stem Cell Epistles, chapter 18.

Despite this “bad news” for iPSCs, two recent papers have actually provided some good news for stem cells that can heal without destroying embryos.  The first paper comes from Timothy Nelson’s laboratory at the Mayo Clinic in Rochester, Minnesota.  Differentiation of iPSCs is, in some cases, rather efficient and the isolation procedures fail to effectively isolate the differentiated cells from potentially tumor-causing cells.  However, in other cases, the differentiation is inefficient and the isolation procedures are also rather poor, which leaves a large enough population of undifferentiated tumor-causing cells.

Nelson’ group has discovered that treating iPSCs and their derivatives with anti-cancer drugs like etoposide (a topoisomerase II inhibitor for those who are interested) increases engraftment efficiency and decreases the incidence of tumors.  My only problem with Nelson’s paper is that he and his colleagues used lentiviral vectors to make their iPSCs.  These vectors tend to produce iPSCs that are rather good at causing tumors.  I would have rather that he tried making iPSCs with other methods that do not leave permanent transgenes in the cells.  Nelson and his group transplanted their iPSC-derived cells into the hearts of mice where they could use high-resolution imaging to determine the number of cells that integrated into the heart and the presence of cell masses that were indicative of tumors.  None of the ectoposide-treated cell transplants caused tumors whereas 4 of the 5 transplants not treated with ectoposide caused tumors.  This paper appeared in Stem Cells and Development.

The second “good news” paper for iPSCs comes from Junji Takeda at the University of Osaka and Ken Igawa from the Tokyo Medical and Dental University, Japan.   In their paper from Stem Cells Translational Medicine, the Japanese groups collaborated to make iPSCs from skin based fibroblasts and then differentiate them into skin cells (keratinocytes).  However, they made the iPSCs in two different ways.  The first protocol utilized the piggyBac transposon system to make iPSCs.  The piggyBac system comes from moths, but it is highly active in mammalian cells.  It can deliver the genes to the cells, but the segment of DNA is then easily excised from the host cells without causing any mutations.  This system, therefore, will generate iPSCs that do not have any transgenes in them.  The second protocol used a system based on cytomegalovirus that leaves the transgenes in the cells but gradually inactivates their expression.

When these two types of iPSCs were compared, they seems to be essentially identical when grown in culture.  Thus in the pluripotent state, the cells were equivalent for the most part.  But once the iPSC lines were differentiated into skin cells, the transgene-free iPSCs formed skin cells that looked, behaved and had the same gene expression profile as normal human skin cells.  The transgene-containing iPSCs differentiated into skin cells, but they did not look quite like skin cells, did not have the same gene expression profile as normal human skin cells, and did not behave like normal human skin cells.

The moral of this story is that not all iPSC lines are created equally and the way you derive them is as important as the cell type from which they were derived.  Also, even incomplete differentiation does not need to be an obstacle for iPSCs, since the cancer-causing cells can be removed by means of specific drugs.  Finally, not all that glitters is gold.  Cloned embryos may give you stem cells that look more like embryonic stem cells, but so what.  These might still suffer from many of the same set backs.  Add to that the ethical problems with getting women to give up their eggs for research and cures (see Jennifer Lahl’s movie Eggsploitation for more disturbing information about that), and you have a losing combination.

Scientists Make Cloned Stem Cells from Adult Cells


For the first time, stem cell scientists have derived stem cells from cloned human embryos that were made from adult cells.  This brings them closer to developing patient-specific lines of cells that can be used to treat a whole host of human maladies, but at a cost.  This research was described in the April 17th online edition of the journal Cell Stem Cell.

In May of last year, Shoukhrat Mitalipov from the Oregon Health and Science University, reported the derivation of human embryonic stem cells from cloned human embryos.  However, these cloned were made using cells that came from infants.  Miltalipov worked out a new protocol for cloning human embryos by using nonhuman primate embryos, in particular those from a Rhesus monkey.

In this study, the donor cells came from two men, a 35-year-old and a 75-year-old.  By using the protocol developed by Mitalipov and his group, Robert Lanza, Young Gie Chung, and Dong Ryul Lee and their colleagues made personalized embryonic stem cells from these two men.

Stem cell biologist Paul Knoepfler, an associate professor at the University of California at Davis who runs the widely read Stem Cell Blog, called the new research “exciting, important, and technically convincing.”  He continued: “In theory you could use those stem cells to produce almost any kind of cell and give it back to a person as a therapy.”

In their paper, Young Gie Chung from the Research Institute for Stem Cell Research for CHA Health Systems in Los Angeles, Robert Lanza from Advanced Cell Technology in Marlborough, Mass., and their co-authors pointed out the potential promise of this technology for new regenerative therapies.  However, their work is also an important discovery for human cloning, since it shows that age-associated changes are not necessarily an impediment to SCNT-based nuclear reprogramming of human cells.

Even though it was the intent of Chung and others to gestate these cloned embryos to form cloned children, this work could be the first step toward creating a baby with the same genetic makeup as a donor.  Thus, this technology presents a so-called “dual-use dilemma.”

Marcy Darnovsky, executive director of the Berkeley, Calif.-based Center for Genetics and Society, explained that many technologies developed for good can be used in ways that the inventor may not have intended and may not like.

“This and every technical advance in cloning human tissue raises the possibility that somebody will use it to clone a human being, and that is a prospect everyone is against,” Darnovsky said.

This paper represents a collaboration between members of academic laboratories and industry.  Funding for this work came from a private medical foundation and South Korea’s Ministry of Science.

Technically, the somatic-cell nuclear transfer protocols used in paper are still somewhat inefficient.  Chung’s team had to attempt 39 times to produce only two blastocyst-stage embryos.  Their first attempts were complete failures, but when they modified the Mitalipov protocol and activated the cloned embryos 2 hours after fusion rather than 30 minutes after fusion, the embryos grew successfully.

“We have reaffirmed that it is possible to generate patient-specific stem cells using [this] technology,” Chung said.

Shoukhrat Mitalipov, director of the Center for Embryonic Cell and Gene Therapy at Oregon Health & Science University, who developed the method that Chung’s group built upon, said that this work involves eggs that have not been fertilized.

“There will always be opposition to embryonic research, but the potential benefits are huge,” Mitalipov said.

Yes, there will be opposition to destructive research on embryos because they are the youngest among us.  No they do not have the right to vote, drive a car, or buy a hunting license, but they have the right to not be harmed.  To deny them that right because they cannot presently exercise particular capacities assumes that the embryo undergoes essential changes as it develops.  But human embryos develop into the kinds of entities they become because of their intrinsic human nature that drives them to do so.  Yes development is a progressive program that causes the embryo to acquire new structures and capabilities that it previously did not have, but what kind of entity can develop into a human adult that is not itself human?  It takes a human embryo to make a human fetus, which makes a human new-born baby, which makes a human toddler, and do on.  This continuum or development and change occurs throughout or lives and this continuum begins at the end of fertilization.

Cloned embryos begin this continuum at the completion of somatic cell nuclear transfer (SCNT).  SCNT works as a stand-in for fertilization, but the result is still the same – a human embryo.  It also should have the right not to be harmed, but instead she is being produced solely for the purpose of being dismembered.  Is this the way we should treat the smallest and most defenseless among us? surely not.  All this talk about, “well we did not form a fully human being” is a crock.  Yes you did.  You formed a fully formed human embryo.  We were all human embryos at one time and these embryos developed into you and me.  We were inarticulate and incapable at the time, but we gained those capacities over time.  Again, how can something that gives rise to a human child not be human?  The embryo is a human being, but it is a very young human being.  Youth should not disqualify it from being able to live.

Seventeen years ago, when Ian Wilmut from the Roslin Institute in Edinburgh, Scotland announced news about the birth of the first sheep cloned from somatic cells named Dolly, several legislators called for a ban on human cloning.  Several countries took measures to limit or outlaw such work, but in the United States.  The cloning issue was obfuscated by dividing it into “reproductive cloning” for the purposes of making cloned children, and “therapeutic cloning” for the development of new therapies.  Unfortunately, this dichotomy is slightly disingenuous since the techniques for both of these procedures are exactly the same except that reproductive cloning uses a surrogate mother to gestate the cloned embryo and bring her to term.  Both of these procedures produce human embryos, but one uses them to make a baby and the other destroys them before they can do so.

President George W. Bush tried to split the difference by restricting federal funding for stem cell research that harms to a human embryo.  This led to talk of Bush’s “embryonic stem cell ban,” which was inaccurate and was used unfairly used to paint Bush as an idiot.  However, some 15 states have laws addressing human cloning, and about half of them ban both reproductive and therapeutic cloning.

Embryonic stem cell research has typically used embryos that are left over from the fertility industry.  However, some religious groups such as the U.S. Conference of Catholic Bishops and others as well  objected to this, since it destroys a very young human being.

However, about seven years ago, Shinya Yamanaka and his colleagues discovered a way to make induced pluripotent stem cells from mature adult cells.  Genetic engineering techniques could convert ordinary cells into pluripotent stem cells without the need for human eggs.  While this technique did not present the same ethical issues, some induced pluripotent stem cells lines contain significant genetic abnormalities and there is still debate over how safe these cells are for clinical use.

The research conducted by Mitalipov and Chung provides a second way of producing pluripotent cells through laboratory techniques that is, in my view, far less ethical and will almost certainly also have unintended consequences as well.

Histones Might Hold the Key to the Generation of Totipotent Stem Cells


Reprogramming adult cells into pluripotent stem cells remains a major challenge to stem cell research. The process remains relatively inefficient and slow and a great deal of effort has been expended to improve the speed, efficiency and safety of the reprogramming procedure.

Researchers from RIKEN in Japan have reported one piece of the reprogramming puzzle that can increase the efficiency of reprogramming. Shunsuke Ishii and his colleagues from RIKEN Tsukuba Institute in Ibaraki, Japan have identified two variant histone proteins that dramatically enhance the efficiency of induced pluripotent stem cell (iPS cell) derivation. These proteins might be the key to generating iPS cells.

Terminally-differentiated adult cells can be reprogrammed into a stem-like pluripotent state either by artificially inducing the expression of four factors called the Yamanaka factors, or as recently shown by shocking them with sublethal stress, such as low pH or pressure. However, attempts to create totipotent stem cells capable of giving rise to a fully formed organism, from differentiated cells, have failed.  However, a paper recently published in the journal Nature has shown that STAP or stimulus-triggered acquisition of pluripotency cells from mouse cells have the capacity to form placenta in culture and therefore, are totipotent.

The study by Shunsuke Ishii and his RIKEN colleagues, which was published in the journal Cell Stem Cell, attempted to identify molecules in mammalian oocytes (eggs) that induce the complete reprograming of the genome and lead to the generation of totipotent embryonic stem cells. This is exactly what happens during normal fertilization, and during cloning by means of the technique known as Somatic-Cell Nuclear Transfer (SCNT). SCNT has been used successfully to clone various species of mammals, but the technique has serious limitations and its use on human cells has been controversial for ethical reasons.

Ishii’s research group focused on two histone variants named TH2A and TH2B, which are known to be specific to the testes where they bind tightly to DNA and influence gene expression.

Histones are proteins that bind to DNA non-specifically and act as little spool around which the DNA winds.  These little wound spools of DNA then assemble into spirals that form thread-like structures.  These threads are then looped around a protein scaffold to form the basic structure of a chromosome.  This compacted form of DNA is called “chromatin,” and the DNA is compacted some 10,000 to 100,000 times.  Histones are the main arbiters of chromatin formation.  In the figure below, you can see that the “beads on a string” consist of histones with DNA wrapped around them.

DNA_to_Chromatin_Formation

There are five “standard” histone proteins: H1, H2A, H2B, H3, and H4.  H2A, H2B, H3 and H4 form the beads and the H1 histone brings the beads together to for the 30nm solenoid.  Variant histones are different histones that assemble into beads that do not wrap the DNA quite as tightly or wrap it differently than the standard histones.  Two variant histones in particular, TH2A and TH2B, tend to allow DNA wrapped into chromatin to form and more loosely packed structure that allows the expression of particular genes.

When members of Ishii’s laboratory added these two variant histone proteins, TH2A/TH2B, to the Yamanaka cocktail (Oct4, c-Myc, Sox2, and Klf4) to reprogram mouse fibroblasts, they increased the efficiency of iPSC cell generation about twenty-fold and the speed of the process two- to threefold. In fact, TH2A and TH2B function as substitutes for two of the Yamanaka factors (Sox2 and c-Myc).

Ishii and other made knockout mice that lacked the genes that encoded TH2A and TH2B. This work demonstrated that TH2A and TH2B function as a pair, and are highly expressed in oocytes and fertilized eggs. Furthermore, these two proteins are needed for the development of the embryo after fertilization, although their levels decrease as the embryo grows.

Graphical Abstract1 [更新済み]

In early embryos, TH2A and TH2B bind to DNA and induce an open chromatin structure in the paternal genome (the genome of sperm cells), which contributes to its activation after fertilization.

These results indicate that TH2A/TH2B might induce reprogramming by regulating a different set of genes than the Yamanaka factors, and that these genes are involved in the generation of totipotent cells in oocyte-based reprogramming as seen in SCNT.

“We believe that TH2A and TH2B in combination enhance reprogramming because they introduce a process that normally operates in the zygote during fertilization and SCNT, and lead to a form of reprogramming that bears more similarity to oocyte-based reprogramming and SCNT” explains Dr. Ishii.

Misrepresentation of the Embryological Facts of Cloning by Reporters


Wesley Smith at National Review Online has been keeping tabs on the reporting of the Cell paper by Shoukhrat Miltalipov from the Oregon Health and Science University. The misrepresentation has been extensive but it’s not really all that surprising given the ignorance and lack of clear thinking on this issue. Nevertheless, Smith has kept up his yeoman’s work, cataloging the factual errors for reporters in multiple publications.

For his first example, see here, where Loren Grush on Fox News.com wrote:

Through a common laboratory method known as somatic cell nuclear transfer (SCNT), ONPRC scientists, along with researchers at Oregon Health & Science University, essentially swapped the genetic codes of an unfertilized egg and a human skin cell to create their new embryonic stem cells…The combination of the egg’s cytoplasm and the skin cell’s nucleus eventually grows and develops into the embryonic stem cell.

Grush, as Smith points out, is quite wrong. Introducing a nucleus from a body cell into the unfertilized egg and inducing it does not turn the egg into embryonic stem cells, but turns it into a zygote. The zygote them undergoes cleavage (cell division) until it reaches the early/mid blastocyst stage 5-6 days later, then immunosurgery is used to isolated the inner cell mass cells, after which they are cultured. Somatic cell nuclear transfer is a stand-in for fertilization. It produces an embryo and all the redefinition in the world will not change that.

Next comes my favorite newspaper, the Wall Street Journal, which normally has decent to pretty good scientific reporting, but this one story from Gautam Naik contains a real howler:

Scientists have used cloning technology to transform human skin cells into embryonic stem cells, an experiment that may revive the controversy over human cloning. The researchers stopped well short of creating a human clone. But they showed, for the first time, that it is possible to create cloned embryonic stem cells that are genetically identical to the person from whom they are derived.

As Smith points out, Miltalipov and others did not stop short of creating a human clone, then explicitly made a cloned human embryo and therefore made a cloned young human being.

Then there is this humdinger from an online Australian news report:

US researchers have reported a breakthrough in stem cell research, describing how they have turned human skin cells into embryonic stem cells for the first time. The method described on Wednesday by Oregon State University scientists in the journal Cell, would not likely be able to create human clones, said Shoukhrat Mitalipov, senior scientist at the Oregon National Primate Research Center. But it is an important step in research because it doesn’t require the use of embryos in creating the type of stem cell capable of transforming into any other type of cell in the body.

Oh my gosh, folks the paper describes the production of cloned embryos expressly for the purpose of dismembering them and destroying them. This “doesn’t require the use of embryos” crap reveals a very basic ignorance of how the experiment was done. See Smith’s excellent post for more details.

Then there is this story from one of my least favorite papers, the LA Times:

Some critics continue to argue that it’s unethical to manipulate the genetic makeup of human eggs even if they’re unfertilized, and others warn about potential harm to egg donors. The biggest ethical issue for the OHSU team, though, is that it artificially created a human embryo, albeit one that was missing the components needed for implantation and development as a fetus.

Come on people! The cloned embryo does not have the components needed to implant because there is no womb into which it can be implanted. Dolly was made the same way. Surely Dolly had the components required to implant.  The problem here is one of will, since these embryos were made to be destroyed. Not capacity. What was done to those embryos was dismemberment. Would we object if they were toddlers?

Just to show that obfuscation is not wholly an American news feature, there is this story from the German newspaper Deutche Welle:

Scientists, for the first time, have cloned embryonic stem cells using reprogrammed adult skin cells, without using human embryos…The process used by Mitalipov is an important step in research because it does not require killing a human embryo–that is, a potential human being–to create transformative stem cells.

As Smith points out, this research made a human embryo that was then killed to make embryonic stem cells. Calling this research humane is to redefine humane to the point of absurdity.

Finally this jewel of blithering ignorance from bioethicist Jonathan Moreno in his column in the Huffington Post:

Despite some confused media reports, the Oregon scientists did not clone a human embryo but a blastocyst that lacks some of the cells needed to implant in a uterus.

And you wonder why people like me have lost all faith in American bioethics. As a developmental biologist, this one just grates on me.  A blastocyst has two cell populations; an outer trophectoderm composed of trophoblast cells that will form the placenta and the inner cell mass cells on the inside of the embryo, which will form the embryo proper and a few placental structures. To be a blastocyst is to have the equipment to implant.

To drive the nail into the coffin, Smith quotes the father of embryonic stem cells James Thomson from an MSNBC interview:

See, you are trying to redefine it away…If you create an embryo by nuclear transfer, if you gave it to somebody who didn’t know where it came from, there would be no test you could do on that embryo to say where it came from. It is what it is. By any reasonable definition, at least as some frequency, you are creating an embryo. If you try to redefine it away, you are being disingenuous.

Check out Smith’s posts. They are all worth reading. Maybe the press will learn some embryology, but I doubt it.

Postscript:  Brendan P. Foht writes at the Corner on National Review Online that in 2010 Shoukhrat Mitalipov, the leader of the Oregon cloning team, reported that he had achieved a single pregnancy using cloned monkey embryos that were made with exactly the same technology as was employed with human eggs in his 2013 Cell paper.  The fetus developed long enough to have a heartbeat detectable through ultrasound. Although the pregnancy failed after 81 days (about half the normal gestation period for that species), the fact that a pregnancy would develop so far indicates that reproductive cloning of primates is in principle possible.  This definitively shows that all this talk about the embryos made in Mitalipov’s lab not being able to implant is pure drek.

Human Stem Cells From Cloned Embryos: What Horrors WIll Follow?


First the news, then the commentary. Here’s the news:

In the May 14th edition of the international journal Cell, Shoukhrat Miltalipov from the Oregon Health and Science University, reported the derivation of human embryonic stem cells from cloned human embryos. This is the first time this has been successfully reported. In 2004, a South Korean researcher, Woo Suk Hwang, reported that his laboratory had succeeded in making patient-specific human embryonic stem cells from cloned embryos, but his papers were later shown to be completely fraudulent, and Hwang, in a word, walked. For more on this sad, sordid event, see my “Catastrophic Cloning Caper” here.

Many laboratories have tried and failed to get cloned human embryos to live long enough to get embryonic stem cells from them. The cloning procedure produces a very abnormal embryo that dies very early during development.

How did Mitalipov succeed when so many others before him had failed? Mitalipov honed his cloning protocol in work with early embryos from Rhesus macaques, and during this work, Mitalipov and his coworkers discovered that including caffeine with the mix of chemicals used during donor removal and transplantation into the host egg prevents the oocytes that have just had their nuclei removed from dividing prematurely, and if these oocytes are used in a cloning experiment, they survive longer than oocytes treated with standard cloning techniques.

“It was a huge battery of changes to the protocols over a number of different steps,” said Mitalipov. “I was worried that we might need a couple of thousand eggs to make all these optimizations, to find that winning combination.”

The procedure used in this paper, cloning, is more technically known as “somatic cell nuclear transfer” or SCNT. SCNT requires human eggs that are extracted from female volunteers of reproductive age who are given several drugs to hyperstimulate their ovaries, which then ovulate several eggs at a time. The eggs are harvested by means as aspiration, and used in SCNT.

For SCNT, the egg nucleus is removed by means of a micropipette. The egg is ever so gently squeezed until the nucleus, which is usually off to one side in the egg, protrude through the cell membrane, and the nucleus is sucked off with the micropipette. Then a body cell; in this paper, fibroblasts from the skin were used, is laid next to the nucleus-less egg, and an electric current is pulsed through the two cells, which causes them to fuse. This fusion converts the egg, which used to have one set of every chromosome, into a cell that now has two sets of every chromosome, and the egg cell, begins to divide and recapitulate the events of early development. This is also referred to as cloning.

Somatic_cell_nuclear_transfer-image

Sperm and eggs have chromosomes that have been modified in specific ways. When the sperm and egg fuse, the process of fertilization begins, and the modifications to the chromosomes serve their purpose during the early stages of development, but those modifications and gradually undone as development proceeds. This phenomenon is known as genetic imprinting and it is very common in mammals. For a good paper on genetic imprinting see Wood AJ, Oakey RJ (2006) Genomic Imprinting in Mammals: Emerging Themes and Established Theories. PLoS Genet 2(11): e147. doi:10.1371/journal.pgen.0020147.

Since cloned embryos have a genome that is not properly imprinted, its development is hamstrung to one degree or another. Most researchers were unable to get cloned human embryos to survive past the 8-cell stage. However, by including caffeine in the SCNT medium during egg nucleus removal and transplantation of the donor nucleus into the host egg, enough of the cloned embryos survived to the 150-cell blastocyst stage to allow for the derivation of embryonic stem cells. Even though SCNT is an exceedingly inefficient process, Mitalipov was able to derive six embryonic stem cells lines from 128 eggs, which is about a 4% success rate.

George Daley of Boston Children’s Hospital and the Harvard Stem Cell Institute, who was not involved in the research, said of it: ““I think it is a beautiful piece of work.” He continued: “This group has become remarkably proficient at a very technically demanding procedure and [has] shown that SCNT-ESCs may in fact be a practical source of cells for regenerative medicine.”

Mitalipov and his group analyzed four of the cloned embryonic stem cell lines and found that their NT-hESCs could successfully differentiate into beating heart cells in culture dishes. Also, they could differentiate into a variety of cell types in teratoma tumors when transplanted into live, immunocompromised mice. These stem cells also had no chromosomal abnormalities, and displayed fewer problematic epigenetic leftovers from parental somatic cells than are typically seen in induced pluripotent stem cells (although, for the life of me, no one has shown that these epigenetic holdovers are a big problem for regenerative medicine). Mitalipov said more comparisons are required, however.

“We are now left to analyze the detailed molecular nature of SCNT-ES cells to determine how closely they resemble embryo-derived ES cells and whether they have any advantages over iPS cells,” added Daley. “iPS cells are easier to produce and have wide applications in research and regenerative medicine, and it remains to be shown whether SCNT-ES cells have any advantages.”

Mitalipov, however, did point out one fundamental difference between NT-ESCs and iPSCs: their nuclear genomes come from the donor cell, but NT-hESCs contain mitochondrial DNA (mtDNA) from the host egg cell. Therefore, SCNT reprograms the cell but also corrects any mtDNA mutations that the donor may carry. Thus, patient-specific NT-hESCs could be used to treat people with diseases caused by mitochondrial mutations. “That’s one of the clear advantages with SCNT,” Milatipov said.

The cells used for this cloning experiment came from infants.  It still remains for cloning to succeed with adult cells as the donor cells.

Now for the commentary:

Regular readers of this blog will already know that I am deeply opposed to human cloning in any form.  It is the equivalent of making people for spare parts.  This is immoral and barbaric.  I predicted some time ago (OK not so long ago, 4 years to be exact), that the technical problems with human cloning would be solved and scientists would one day clone a human embryo.  Now that it is here, I hope that people are as horrified by it as I am.

“Get over it.  It’s an embryo and a cloned one at that.” you might say.  But what if the malady that doctors want to cure is poorly served by embryonic stem cells made from cloned embryos and a cloned fetus is a better source of cells?  Do we allow gestation of the cloned embryo to the fetal stage so that we can dismember it and take its tissue?  Let’s bring this home.  What if the cells needed to come from a five-year old?  Can we justify that because the kid was cloned?

“But wait, that’s a five-year old and this is an embryo,” you say.  But you were once a blastocyst.  You did not pass through the blastocyst stage, you WERE a blastocyst.  The only difference between the blastocyst and you now is time, environment, degree of dependence, and size.  Are any of these differences morally significant when it comes to whether or not we can kill you?  Can we kill all the short people?  Can we kill all the younger people because they are not as well-developed?  Can we kill people who are dependent on others (that includes everyone mate, so put your hand down)?  Can we kill those in a different location (genocide anyone)?  None of these categories constitutes a good reason for terminating someone’s life.  Likewise, none of these changes renders you essentially different from who and what you are.  To kill someone at the earliest stages for their tissue is simple murder, and we use size, location, extent of development, location and degree of dependence to salve of consciences for doing it, but that won’t define what we are doing.

People will go on and on about the great advances that could lead to.  Sorry, I’m not buying that one.  Embryonic stem cells have been promising that one for the last 15 years with pert near little to nothing to show for it.  This discovery is a great technical advance, but it opens to door to reproductive cloning – an even bigger mistake, and fetus farming, in which we destroy our own children in the womb, not because they are in inconvenience to us, but because we want their tissues to save our lives.  Now children, rather than being a blessing, are merely tissues to be harvested.  We have become like the Greek gods from the stories of old who ate their own children.  May God forgive us.