Stem cell research and female egg synthesis

Stem cell research and female egg synthesis

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In terms of years, how far is stem cell research from being able to produce a female human egg from other female body cells?

I suppose that there is no connection between producing egg from somatic cells and stem cell research. The thing that you have mentioned: "produce a female human egg from other female body cells" was already done in 1996 (!) in sheep. Technically, there is no reason that this procedure will not work in Human as well. So in term of years: this was possible 20 years ago… :-)

Program of early development in the mammal: synthesis and intracellular migration of histone H4 during oogenesis in the mouse

Synthesis of histone H4 by mouse oocytes and unfertilized eggs has been examined by using a modified high-resolution two-dimensional gel electrophoresis procedure capable of resolving basic proteins (M. J. LaMarca and P. M. Wassarman, 1979, Develop. Biol. 73, 103-119). Histones were separated on such gels and observed rates of incorporation of [35S]methionine into histone H4 were converted into absolute rates of synthesis by using previously determined values for the absolute rates of total protein synthesis in mouse oocytes and unfertilized eggs (R. M. Schultz, G. E. Letourneau, and P. M. Wassarman, 1979, Develop. Biol. 68, 341-359 73, 120-133). Histone H4 was synthesized at all stages of oogenesis examined, and accounted for 0.07, 0.05, and 0.04% of total protein synthesis in growing oocytes, fully grown oocytes, and unfertilized eggs, respectively. During oocyte maturation the absolute rate of histone H4 synthesis decreased by about 40%, as compared to a 23% decrease in the rate of total protein synthesis during the same period. These measurements indicate that enough histone is synthesized during oogenesis in the mouse to support two to three cell divisions. Examination of the intracellular location of newly synthesized proteins in fully grown oocytes revealed that histone H4 was highly concentrated in the nucleus (germinal vesicle), whereas total protein and tubulin were not. Nearly 50% of the histone H4 synthesized during a 5-hr period was located in the oocyte's germinal vesicle, as compared to 1.9 and 0.9% for total protein and tubulin, respectively. These results are compared with those obtained using oocytes and eggs from nonmammalian animal species.

Fucntioning egg cells

While the cells looked like mature eggs, the key question was whether they actually were functional egg cells. The team compared their lab-grown eggs with ones from an ovary and found they were the same size and organised their genetic material in similar patterns.

Mouse embryo. Shutterstock

The researchers also showed that their eggs could be fertilised, implanted into a surrogate female and go on to produce live offspring. But only a very small number of their embryos created in this way developed fully to term – just 3.5% of all the embryos they transferred. Importantly though, the team reported that “all the obtained pups grew up normally without evidence of premature death.”

As all good scientists should, the researchers then replicated their experiments to test how robust their technique was. Initially, they used embryonic stem cells in their experiments, but these create an ethical dilemma because an embryo has to be destroyed to produce them.

In 2006, however, another researcher named Shinya Yamanaka and his team found that turning on just four specific genes in normal adult cells gives them all the potential to develop into other cells just like embryonic stem cells, but without the need to destroy a single embryo. The latest research showed that eggs made from these “induced pluripotent stem cells”, or IPSCs, were just as capable of being fertilised and producing healthy adult offspring as embryonic stem cells.

Testing the Life Cycle

The only way to fully assess the quality and functionality of a sperm or egg is to use it to, well, try to fertilize another gamete and produce a baby. That’s why this work has to be approached with the utmost care, says Sebastiano. He hypothesizes that once scientists have developed techniques that they think produce mature human oocytes and sperm, the next step will be testing these techniques in primates. That way, researchers can follow the entire life of individual animals produced from this technique to see if any unexpected problems develop, he says.

Sebastiano has no doubt that one day, these stem cells could help individuals struggling with infertility to produce healthy children. This, along with a fascination with biological development, is what drives Sebastiano’s work. There are also, of course, significant ethical considerations that have to be carefully considered. This technique has the potential to affect human life on a generational level, he notes. And many people also raise concerns about other future consequences, like the ability to create “designer babies” or produce offspring from hairs stolen from unsuspecting celebrities . Bioethics experts have written about the need to start working through the medical and legal issues around this technique now, before it is viable.

“There is a need actually to develop this, but since we are really dealing with a very unique cell type … we need to be cautious,” says Sebastiano.

Egg yolk peptides up-regulate glutathione synthesis and antioxidant enzyme activities in a porcine model of intestinal oxidative stress

Long-term oxidative stress in the gastrointestinal tract can lead to the development of chronic intestinal disorders. Many food-derived antioxidants are effective in vitro, but the variable reports of in vivo efficacy and the pro-oxidant nature of some antioxidants necessitate alternative strategies for the reduction of in vivo oxidative stress. Compounds that up-regulate the production of endogenous antioxidants such as glutathione (GSH) and antioxidant enzymes provide novel approaches for the restoration of redox homeostatis. Egg yolk peptides (EYP) prepared from Alcalase and protease N digestion of delipidated egg yolk proteins were found to exhibit antioxidative stress properties. The effect of EYP supplementation was examined in a hydrogen peroxide-induced human colon cell line and in an animal model of intestinal oxidative stress. EYP significantly reduced the pro-inflammatory cytokine, IL-8, in Caco-2 cells. In piglets given intraperitoneal infusions of hydrogen peroxide, EYP treatment increased GSH and gamma-glutamylcysteine synthetase mRNA expression and activity, significantly increased antioxidant enzyme activities, in particular catalase and glutathione S-transferase activities, and reduced protein and lipid oxidation in the duodenum, jejunum, ileum, and colon. Furthermore, EYP boosted the systemic antioxidant status in blood by increasing the GSH concentration in red blood cells. These results suggest that EYP supplementation is a novel strategy for the reduction of intestinal oxidative stress.

Stem cell breakthrough may allow same gender couples to create babies

Researchers from Cambridge University and Israel’s Weizmann Institute of Science are claiming a stem cell research breakthrough that would allow a baby to be created from the skin cells from two adults, no matter their gender. This potentially allows for infertile couples to have their own children without resorting to sperm or egg donors, and may provide the means for same sex couples to produce their own babies.

Previously only successful in experiments on mice, the new research has been conducted on human cells for the first time. In this study, the researchers paired stem cell lines from embryos with the skin of a range of different adults, with the resultant cells compared to aborted fetuses to determine an identical match.

Techniques devised to create same-sex offspring are not new. Some experiments involve the manipulation of fibroblasts in mice resulting in offspring with the genetic traits of multiple male mice, whilst others have used bone marrow stem cells extracted from males to trigger spermatogonia.

However, in this latest research, stem cells and adult human skin have been combined for the first time to create an entire new germ-cell line (that is, cells that will become embryos). Derived from ten different donor sources, the new germ-cell lines were created from 10 different donor sources – five embryos and five adults.

Intrinsic to this pairing was the SOX17 gene. A master gene, SOX17 usually works to direct stem cells to be “programmed” to become whatever organs or body parts are required – in other research this techniques has been used to create lung, gut, and pancreas cells.

The manipulation of the gene to be part of a primordial germ cell specification (that is, direct it to create cells that will become an entire human), however, is a new development pioneered by the team and has allowed them to follow this discovery with actually making primordial germ cells in the lab. This stage in a baby’s development is known as "specification", and once primordial germ cells become specified, they continue to develop inexorably toward precursor sperm or ova cells.

Creating human egg and sperm cells from the skin of two adults of the same gender immediately raises the possibility of same sex couples procreating and offering an alternate pregnancy path for infertile couples. Of course, it also opens the door to a new minefield of ethical and moral implications, but the researchers note that many people may potentially benefit from the technique.

The results of the research were published in the online journal Cell.

Cycles of failure

Women undergo IVF because either they or their partner has fertility problems. If the problem is female infertility, the most probable causes are tubal or ovulatory dysfunction or the decline of oocyte numbers and fertility associated with maternal age. Ovarian stimulation treatment is designed to maximise the number of oocytes available for a given in vitro fertilisation procedure. Ovarian stimulation is also part of the treatment strategy for male infertility because intracytoplasmic sperm injection (ICSI), the most common clinical treatment for male infertility, depends on ex vivo oocytes and in vitro techniques. Clinic staff attempt to fertilise all the mature oocytes retrieved. For the women interviewed, this point in the process involves the most anxiety and potential disappointment. The IVF patient must wait for between 2 and 5 days to see if a viable blastocyst (early embryo) develops from the process. No successful fertilisation may result, and the entire process may be for naught. They must then decide whether or not to undergo another cycle. Most of the women we spoke to indicated that, before entering IVF, they had overestimated the extent to which the technology could compensate for their own low fertility. They reported being excited and hopeful with their first procedure, but their optimism decreased as the reality of failed cycles came home:

I think [for] your first cycle, you’re kind of excited, and I remember saying to someone, ‘This isn’t as hard as what everyone supposedly reckons it is. I’ve heard IVF is really hard. It’s not that hard’. And the first time, it’s quite exciting, and if that doesn’t work you get to the second time and you’re all excited and gee’d up and that doesn’t work and then, you know … (Caroline, married, no children)

Many women opt for repeated cycles with no guarantee of an improved result. The experience becomes more difficult each time:

This was the fifth go at either embryo transfer or a full cycle, and so there was a lot more emotion. I realise now, when I look back at certain times last year when I was really emotional about it. I hate egg collection. (Eva, married with one child)

Stem cells may make new eggs in women.

Scientists may have to come up with a new explanation for how a woman's biological clock works.

A study in mice appears to overturn the long-held assumption that female mammals are born with all the eggs they'll ever have. Researchers have found evidence that the ovaries of even mature rodents retain a population of cells that can spawn new eggs. The finding may force reproductive biologists to rethink the fundamentals of menopause and female infertility and how to treat either condition.

"We're still somewhat in a state of disbelief," says study leader Jonathan L. Tilly of Massachusetts General Hospital in Boston.

Men typically produce sperm throughout their lives, thanks to a small population of germline stem cells. But biologists have for decades assumed that women start life with a fixed supply of eggs, which steadily dwindles until practically no eggs remain and menopause begins.

Studies early in the past century hinted that the ovaries of adult female mammals had their own version of germline stem cells, but an influential paper in 1951 argued against ongoing egg production and effectively ended the debate. "Everyone was taught that it was settled," says Allan Spradling of the Carnegie Institution in Baltimore. "We have to thank Dr. Tilly for doubting this 'proven fact' and looking again."

Tilly and his colleagues began to question the dogma when they performed the first measurements of the death rate of ovarian follicles in mice. In these capsule-like structures, support cells envelop an immature egg, or oocyte.

Scientists knew that the number of oocyte-containing follicles decreases as female mammals age, but Tilly's team found so high a follicle-death rate in young and adult mice that the animals' ovaries should have been depleted of eggs within days or weeks. Since female mice are fertile for more than a year, their ovaries had to be generating new oocytes, the scientists reasoned.

The team subsequently identified cells on the surface of adult-mouse ovaries that look like the germline stem cells seen previously in fetal ovaries. These putative stem cells proliferate and contain a protein used in the making of an oocyte, Tilly's group reports in the March 11 Nature.

The biologists also found that a drug known to kill male germline stem cells appears to kill the female counterparts as well.

Finally, the investigators grafted healthy ovarian tissue from normal adult mice onto the ovaries of other adult mice that had been genetically engineered to have green-glowing cells. About a month later, green-glowing oocytes were found in the transplanted tissue, indicating that germline cells in the engineered mice had spawned new eggs that migrated into the transplanted tissue.

Tilly's team plans to isolate and characterize the mouse germline stem cells, steps useful for determining whether women possess the same cells. If that turns out to be the case, scientists will be confronted with a new question: Why do a woman's germline stem cells stop replenishing her eggs as she nears menopause?

Fertility scientists might try transplanting ovarian germline stem cells to delay menopause, Tilly suggests. The cells could, in theory, also be harvested from women about to undergo sterilizing radiation or chemotherapy for cancer. Says Tilly: "If these cells can be banked and stored, they can be reintroduced back into a patient to restore fertility."--J. TRAVIS

Scientists developed fertilized eggs from mouse stem cells

Japanese reproductive biologist, Katsuhiko Hayashi at the Kyushu University in Fukuoka, headed the research that published its findings in the journal known as ‘Nature’ on how they had been able to produce mouse eggs from mouse stem cells under laboratory conditions and then pushed the eggs towards fertilisation, yielding a fertile offspring as the end result. This is usually a territory that scientists tread with utmost caution.

The work is a “stunning achievement,” says George Daley of Harvard Medical School in Boston, who was not involved in the project.[1]

Pluripotent stem cells and mouse eggs.

Oocytes, or egg cells were produced from induced pluripotent stem cells derived from mouse skin cells and mouse embryonic stem cells under clinical conditions in a petri-dish. The characteristics of both stem cell types enable them to generate almost any cell type in the human body.

Utilizing the sperm from a healthy male mouse, through IVF or vitro fertilization process, the research team fertilized the egg cells. They team only transplanted the fertilized eggs into female mice only they had been conditioned to grow into two cell embryos. 3.5% of the implanted embryos successfully produced offspring who in turn were able to reproduced post turning into matured adult mice.

“The researchers also showed that they could derive new ES cell lines from embryos generated from the labmade eggs. That recreates, they note, a full cycle of female germ cell development in the lab.”[2]

Not perfect science

The egg-making technique, whilst impressive has been identified with some serious concerns. Only 3.5% of the implanted embryos were able to grow into healthy adult mice. Additionally, the research team also found out that approximately 18% of the stem-cell derived eggs had an unusual number of chromosomes. The presence of the imbalanced chromosomes possibly resulted in less embryos developing and could probably also cause genetic disorders in the offspring.

In order to complete the process, scientists added cells extracted from the mouse embryos in pregnant mice to the culture dish. The egg cells matured and developed with the support of these outside cells. More research is ongoing in evolving artificial reagents that will in future be able to substitute the requirement for cells.

Will human eggs be next?

This investigative study automatically raises reservations about the scientific attempt to produce artificial human eggs in a petri-dish. “If a similar strategy proves successful in human pluripotent stem cells, then the options for reproductive biology, but also genetic modification of the germ line, are profound,” Daley says.[3]

In a Nature news release, Azim Surani who is well known in this area of research, said that these ethical issues should be discussed now and include the general public. “This is the right time to involve the wider public in these discussions, long before and in case the procedure becomes feasible in humans.”[4]

In an interview with , James Adjaye, another expert from Heinrich Heine University in Germany, raised the point that even if we did generate artificial human eggs, “the final and ultimate test for fully functional human ‘eggs in a dish’ would be the fertilization using IVF, which is also ethically not allowed.”[5]

Looking forward, senior author on the Nature study, Katsuhiko Hayashi, predicted that in a decade, lab-grown “oocyte-like” human eggs will be available but probably not at a scale for fertility treatments. Because of the technical issues his study revealed, he commented, “It is too preliminary to use artificial oocytes in the clinic.”[6]

[1] Mouse egg cells made entirely in the lab give rise to healthy offspring – By Gretchen Voge, Oct. 17, 2016

[2] Reconstitution in vitro of the entire cycle of the mouse female germ line – Orie Hikabe, Nobuhiko Hamazaki, Go Nagamatsu, Yayoi Obata, Yuji Hirao, Norio Hamada, So Shimamoto, Takuya Imamura, Kinichi Nakashima, Mitinori Saitou & Katsuhiko Hayashi

[3] Mouse egg cells made entirely in the lab give rise to healthy offspring – By Gretchen Voge, Oct. 17, 2016

[4] Eggciting News: Scientists developed fertilized eggs from mouse stem cells – KAREN RING, OCTOBER 19, 2016

[5] Scientists grow mouse eggs from stem cells in lab – October 17, 2016

[6] Eggciting News: Scientists developed fertilized eggs from mouse stem cells – KAREN RING, OCTOBER 19, 2016

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