Researchers Reconstruct Early Stages of Embryo Development

Researchers Reconstruct Early Stages of Embryo Development

Tuesday, 04 November 2014

Researchers at the University of Cambridge have managed to reconstruct the early stage of mammalian development using embryonic stem cells, showing that a critical mass of cells – not too few, but not too many – is needed for the cells to being self-organising into the correct structure for an embryo to form.

All organisms develop from embryos: a cell divides generating many cells. In the early stages of this process, all cells look alike and tend to aggregate into a featureless structure, more often than not a ball. Then, the cells begin to 'specialise' into different types of cell and space out asymmetrically, forming an axis which begins to provide a structure for the embryo to develop along.

In animal embryos this stage is followed by a process known as gastrulation: a choreographed movement of the cells that, using the initial axis as a reference, positions the head and the tail, the front and the back. During the process, the cells begin to form three distinct layers: the endoderm, mesoderm and ectoderm, determining which tissues or organs the cells will then develop into.

Professor Alfonso Martinez-Arias from the Department of Genetics at the University of Cambridge, who led the research, says:

"Gastrulation was described by biologist Professor Lewis Wolpert as being 'truly the most important event in your life' because it creates the blueprint of an organism. Axis formation and gastrulation are the two central processes that initiate the development of an organism and are inextricably associated with the embryo. We have managed to recreate this for the first time in the lab."

Professor Martinez-Arias and colleagues, supported by the European Research Council and the Wellcome Trust, have reconstructed these early stages of development using mouse embryonic stem cells. Embryonic stem cells, discovered in the Department of Genetics in the 1980s (for which Sir Martin Evans was awarded the Nobel Prize in Physiology or Medicine 2007), have become an important tool for developmental biology, understanding disease, and in regenerative medicine due to the ability to give rise to all cell types in culture. Over the last few years, they have been used to 'grow' organs including the eye and the cerebral cortex; surprisingly, these structures develop without an axis.

In research published today in the journal Development, the researchers report a way to coax cells to reorganize in the manner that they do in an embryo, creating an axis and undergoing movements and organisations that mimic the process of gastrulation. Over the years researchers have been making aggregates of embryonic stem cells to obtain certain cell types, for example red blood cells. However, these aggregates lack structure and the different cell types emerge in a disorganised fashion. This is the first time that researchers have been able to elicit axis formation, spatial organisation and gastrulation-like movements from aggregates of embryonic stem cells.

The researchers show that if the number of cells aggregated initially is similar to that of a mouse embryo, the cells generate a single axis and this serves as a template for a sequence of events that mimics those of the early embryo. By manipulating the signals that the cells see at a particular time, the researchers were able to influence what type of cell they become and how they are organised. In one of the experiments, for example, activation of a particular signal at the correct time elicits the appearance of the mesoderm, endoderm and ectoderm – the precursors of all cell types – with a spatial organization similar to that of an embryo.

Using this experimental system, the researchers were able to generate the early stages of a spinal cord, which they showed forms as part of the process of gastrulation. This finding complements previous research from the University of Edinburgh and the National Institute for Medical Research which showed that embryonic stem cells can be coaxed into this spinal cord cells; however, the Cambridge researchers showed that in the embryo-like aggregates, the structural organization is more robust and allows for the polarised growth of the tissue.

Professor Martinez-Arias adds:

"It is early days but this system promises insights into the early stages of development and what determines the specification of the different cell types. This will allow more robust protocols for differentiation with cues that mimic those that the cells are subject to in embryos.”

"Most significantly, the system will provide a means to test, experimentally, how a homogeneous group of cells organizes itself in space, a central process in the development of any organism, and the ability to recreate in culture the niches that adult stem cells create during embryogenesis and which have remained elusive experimentally."

Source: University of Cambridge

Contact: Craig Brierley

References:

Symmetry breaking, germ layer specification and axial organisation in aggregates of mouse ES cells

Susanne C. van den Brink, Peter Baillie-Johnson, Tina Balayo, Anna-Katerina Hadjantonakis, Sonja Nowotschin, David A. Turner, and Alfonso Martinez Arias

Development 2014 141:4231-4242; doi:10.1242/dev.113001

Wnt/β-catenin and FGF signalling direct the specification and maintenance of a neuromesodermal axial progenitor in ensembles of mouse ES cells

David A. Turner, Penelope C. Hayward, Peter Baillie-Johnson, Pau Rué, Rebecca Broome, Fernando Faunes, and Alfonso Martinez Arias

Development; 2014 141:4243-4253; doi:10.1242/dev.112979

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'Master Switch' for Myelination in Human Brain Stem Cells is Identified

Finding is key to developing MS treatments using stem cells

Tuesday, 01 July 2014

The identification of the transcription factor,

SOX10, in human brain cells, brings researchers

closer to the goal of treating multiple sclerosis

(MS) by transplanting into patients the brain cells

that make myelin. Credit: Jing Wang. 

Scientists at the University at Buffalo have identified the single transcription factor or "master switch" that initiates the critical myelination process in the brain. The research will be published online in Proceedings of the National Academy of Sciences (PNAS) on June 30.

The identification of this factor, SOX10, in human brain cells, brings researchers closer to the goal of treating multiple sclerosis (MS) by transplanting into patients the brain cells that make myelin.

"Now that we have identified SOX10 as an initiator of myelination, we can work on developing a viral or pharmaceutical approach to inducing it in MS patients," says Fraser Sim, PhD, senior author on the paper and assistant professor in the UB Department of Pharmacology and Toxicology in the School of Medicine and Biomedical Sciences.

"If we could create a small molecule drug that would switch on SOX10, that would be therapeutically important," he adds.

Stem cell therapy is seen as having dramatic potential for treating MS, but there are key obstacles, especially the length of time it takes for progenitor cells to turn into oligodendrocytes, the brain's myelin-making cells.

Using currently available methods, Sim explains, it can take as long as a year to generate a sufficient number of human oligodendrocyte cells to treat a single MS patient.

That's partly because there are so many steps: the skin or blood cell must be turned into induced pluripotent stem cells, which can differentiate into any other type of cell and from which neural progenitor cells can be produced. Those progenitor cells then must undergo differentiation to oligodendrocyte progenitors that are capable of ultimately producing the oligodendrocytes.

"Ideally, we'd like to get directly to oligodendrocyte progenitors," says Sim.

"The new results are a stepping stone to the overall goal of being able to take a patient's skin cells or blood cells and create from them oligodendrocyte progenitors," he says.

Using foetal (not embryonic) brain stem cells, the UB researchers searched for transcription factors that are absent in neural progenitor cells and switched on in oligodendrocyte progenitor cells.

While neural progenitor cells are capable of producing myelin, they do so very poorly and can cause undesirable outcomes in patients, so the only candidate for transplantation is the oligodendrocyte progenitor.

"The ideal cell to transplant is the oligodendrocyte progenitor cell," Sim says.

"The question was, could we use one of these transcription factors to turn the neural progenitor cell into an oligodendrocyte progenitor cell?"

To find out, they looked at different characteristics, such as mRNA expression, protein and whole gene expression and functional studies.

"We narrowed it down to a short list of 10 transcription factors that were made exclusively by oligodendrocyte progenitor cells," says Sim.

"Among all 10 factors that we studied, only SOX10 was able to make the switch from neural progenitor to oligodendrocyte progenitor cell," says Sim.

In addition, the UB researchers found that SOX10 could expedite the transformation from oligodendrocyte progenitor cell to differentiation as an oligodendrocyte, the myelin-producing cell and the ultimate treatment goal for MS.

"SOX10 facilitates both steps," says Sim.

That's tantalizing, he says, because one of the biggest problems with MS is that cells get stuck in the step between the oligodendrocyte progenitor cell and the oligodendrocyte.

"In MS, first the immune system attacks the brain, but the brain is unable to repair itself effectively," explains Sim.

"If we could boost the regeneration step by facilitating formation of oligodendrocytes from progenitor cells, then we might be able to keep patients in the relapsing remitting stage of MS, a far less burdensome stage of disease than the later, progressive stage."

Sim is also an investigator with other scientists at UB and the University of Rochester on the $12.1 million New York State Stem Cell Science award led by SUNY Upstate Medical Center. The research will test the safety and effectiveness of implanting stem cells that can reproduce myelin into the central nervous system of MS patients.

Source: University at Buffalo 

Contact: Ellen Goldbaum

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Ability to Isolate and Grow Breast Tissue Stem Cells Could Speed Cancer Research

Salk scientists find two key proteins that regulate the growth of mammary stem cells and could contribute to breast cancer 

Monday, 05 May 2014

By carefully controlling the levels of two proteins, researchers at the Salk Institute have discovered how to keep mammary stem cells – those that can form breast tissue – alive and functioning in the lab. The new ability to propagate mammary stem cells is allowing them to study both breast development and the formation of breast cancers.

Peter C. Gray, Benjamin T. Spike and Geoffrey

M. Wahl. Credit: Courtesy of the Salk Institute

for Biological Studies. 

"What we've shown is that we can take these cells out of a mouse and study them and regulate them in the laboratory by providing them with a specific factor," says Peter C. Gray, a staff scientist in Salk's Clayton Foundation Laboratories for Peptide Biology, who collaborated on the new work with Benjamin T. Spike, a senior research associate in the laboratory of Salk Professor Geoffrey M. Wahl.

The results of the study were published in the April 8th, 2014 issue of the journal Stem Cell Reports.

Mammary stem cells can give rise to new breast cells during foetal development, adolescence or lactation and may also play a role in breast cancer, so they represent a highly promising avenue for breast cancer research. But isolating the stem cells and maintaining them in the lab to study has been difficult.

"There was a lot of prior work demonstrating that mammary-specific stem cells exist, but it was virtually impossible to isolate them in numbers from an adult," says Spike.

"But we previously found we could turn to early development, when the stem cells are present in higher proportions."

When scientists add CRIPTO to a population of

breast stem cells, they retain their ability to

produce more stem cells, keeping the population

constant. But when CRIPTO's action is blocked

with the molecule ALK4, the cells differentiate

into mature cells and the population of stem cells

shrinks. Credit: Salk Institute for Biological

Studies. 

When the researchers used foetal breast tissue rather than adult tissue from mice, they were able to pinpoint which cells were stem cells but the cells would rapidly change when grown in a dish. A defining property of all stem cells is that when they divide into two new cells, they can form both stem cells and differentiated cells (cells on their way to becoming a specific type of tissue).

Spike and Gray grew the mammary stem cells in culture dishes and stained them so that new stem cells appeared a different colour from differentiated mammary cells. Then, they began testing the effects of two proteins – known as CRIPTO and GRP78 – that play significant roles in both stem cell biology and embryonic development.

"In normal conditions, we first see the cells as yellow – the combination of red and green within a single cell – then later see cells that are either red or green, showing that our cells had the capacity to make two different types of mature cells," says Spike.

"But then when we do the experiment again and start changing protein levels, the ratio of these cells becomes very different."

Isolated foetal mammary cells show high levels

of CRIPTO (green) and GRP78 (red), which have

been found to help control the differentiation of

mammary stem cells. Credit: Salk Institute for

Biological Studies. 

The researchers found that when they blocked CRIPTO, the cells mostly formed differentiated cells instead of new stem cells. Over time, this stem cell population shrank since they weren't repopulating themselves. When they instead boosted levels of CRIPTO, the stem cell colony grew as new stem cells were produced more often than differentiated cells.

In studies in mice, the scientists also found that CRIPTO helped the animals form new mammary tissues, which led the team to hypothesize that CRIPTO may be produced by nearby cells in the fat to spur the growth of breast tissue.

In a previous study, Gray's group had discovered that the protein GRP78 binds CRIPTO on the surface of cells and regulates CRIPTO function. This prompted the scientists to test whether GRP78 had an effect on the mammary stem cells. As they suspected, when cells lacked GRP78 on their surfaces, they didn't respond to CRIPTO.

Both CRIPTO and GRP78 have been implicated in cancers, including breast cancer and lung cancers. Scientists think high levels of either protein could encourage tumour growth using similar pathways that they use to spur breast tissue growth. With the new ability to isolate and sustain mammary stem cells, Spike and Gray hope they can uncover details on exactly what cellular programs CRIPTO and GRP78 activate. Understanding this in stem cells could further understanding on how these proteins are involved in tumour growth.

Additionally the researchers think that targeting CRIPTO and GRP78 – which are ideal drug targets since they are present outside of cells – could halt or slow cancer growth. 

"It's looking more and more like what's required to target cancer is to have many therapeutics hitting different pathways," says Gray.

"We think targeting CRIPTO and GRP78 could be a unique way of supplementing existing treatment modalities by targeting stem cell-like cells in cancer."

Source: Salk Institute

Contact: Chris Emery

Reference:

CRIPTO/GRP78 Signaling Maintains Fetal and Adult Mammary Stem Cells Ex Vivo

Benjamin T. Spike, Jonathan A. Kelber, Evan Booker, Madhuri Kalathur, Rose Rodewald, Julia Lipianskaya, Justin La, Marielle He, Tracy Wright, Richard Klemke, Geoffrey M. Wahl, Peter C. Gray

Stem Cell Report, 8 April 2014, Volume 2, Issue 4, p427–439

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First Disease-specific Human Embryonic Stem Cell Line by Nuclear Transfer

Major step toward cell-based therapies for life-threatening diseases

Tuesday, 29 April 2014

Using somatic cell nuclear transfer, a team of scientists led by Dr. Dieter Egli at the New York Stem Cell Foundation (NYSCF) Research Institute and Dr. Mark Sauer at Columbia University Medical Center has created the first disease-specific embryonic stem cell line with two sets of chromosomes.

Embryonic stem cells from an adult with type 1

diabetes were created by transferring the nucleus

from a skin cell of the patient into a donor oocyte.

Credit: Bjarki Johannesson, NYSCF. 

As reported today in Nature, the scientists derived embryonic stem cells by adding the nuclei of adult skin cells to unfertilized donor oocytes using a process called somatic cell nuclear transfer (SCNT). Embryonic stem cells were created from one adult donor with type 1 diabetes and a healthy control. In 2011, the team reported creating the first embryonic cell line from human skin using nuclear transfer when they made stem cells and insulin-producing beta cells from patients with type 1 diabetes. However, those stem cells were triploid, meaning they had three sets of chromosomes, and therefore could not be used for new therapies.

The investigators overcame the final hurdle in making personalized stem cells that can be used to develop personalized cell therapies. They demonstrated the ability to make a patient-specific embryonic stem cell line that has two sets of chromosomes (a diploid state), the normal number in human cells. Reports from 2013 showed the ability to reprogram foetal fibroblasts using SCNT; however, this latest work demonstrates the first successful derivation by SCNT of diploid pluripotent stem cells from adult and neonatal somatic cells.

"From the start, the goal of this work has been to make patient-specific stem cells from an adult human subject with type 1 diabetes that can give rise to the cells lost in the disease," said Dr. Egli, the NYSCF scientist who led the research and conducted many of the experiments.

"By reprograming cells to a pluripotent state and making beta cells, we are now one step closer to being able to treat diabetic patients with their own insulin-producing cells."

"I am thrilled to say we have accomplished our goal of creating patient-specific stem cells from diabetic patients using somatic cell nuclear transfer," said Susan L. Solomon, CEO and co-founder of NYSCF.

"I became involved with medical research when my son was diagnosed with type 1 diabetes, and seeing today's results give me hope that we will one day have a cure for this debilitating disease. The NYSCF laboratory is one of the few places in the world that pursues all types of stem cell research. Even though many people questioned the necessity of continuing our SCNT work, we felt it was critical to advance all types of stem-cell research in pursuit of cures. We don't have a favourite cell type, and we don't yet know what kind of cell is going to be best for putting back into patients to treat their disease."

The research is the culmination of an effort begun in 2006 to make patient-specific embryonic stem cell lines from patients with type 1 diabetes. Ms. Solomon opened NYSCF's privately funded laboratory on March 1, 2006, to facilitate the creation of type 1 diabetes patient-specific embryonic stem cells using SCNT. Initially, the stem cell experiments were done at Harvard and the skin biopsies from type 1 diabetic patients at Columbia; however, isolation of the cell nuclei from these skin biopsies could not be conducted in the federally funded laboratories at Columbia, necessitating a safe-haven laboratory to complete the research. NYSCF initially established its lab, now the largest independent stem cell laboratory in the nation, to serve as the site for this research.

In 2008, all of the research was moved to the NYSCF laboratory when the Harvard scientists determined they could no longer move forward, as restrictions in Massachusetts prevented their obtaining oocytes. Dr. Egli left Harvard University and joined NYSCF; at the same time, NYSCF forged a collaboration with Dr. Sauer who designed a unique egg-donor program that allowed the scientists to obtain oocytes for the research.

"This project is a great example of how enormous strides can be achieved when investigators in basic science and clinical medicine collaborate. I feel fortunate to have been able to participate in this important project," said Dr. Sauer. Dr. Sauer is vice chair of the Department of Obstetrics and Gynecology, professor of obstetrics and gynaecology, and chief of reproductive endocrinology at Columbia University Medical Center and program director of assisted reproduction at the Center for Women's Reproductive Care.

Patients with type 1 diabetes lack insulin-producing beta cells, resulting in insulin deficiency and high blood-sugar levels. Therefore, producing beta cells from stem cells for transplantation holds promise as a treatment and potential cure for type 1 diabetes. Because the stem cells are made using a patient's own skin cells, the beta cells for replacement therapy would be autologous, or from the patient, matching the patient's DNA.

Generating autologous beta cells using SCNT is only the first step in developing a complete cell replacement therapy for type 1 diabetes. In type 1 diabetes, the body's immune system attacks its own beta cells; therefore, further work is underway at NYSCF, Columbia, and other institutions to develop strategies to protect existing and therapeutic beta cells from attack by the immune system, as well as to prevent such attack.

The technique described in the report published today can also be translated for use in the development of personalized autologous cell therapies for many other diseases and conditions including Parkinson's disease, macular degeneration, multiple sclerosis, and liver diseases and for replacing or repairing damaged bones.

As part of the work, the scientists systematically analysed the factors that affect stem-cell derivation after SCNT. The reprogramming of skin cells from a type 1 diabetes patient by SCNT has long been sought, but has been challenging to achieve because of logistical difficulties in obtaining human oocytes for research, as well as an incomplete understanding of the biology of human oocytes.

The scientists found that the addition of specific chemicals, called histone deacetylase inhibitors, and an efficient protocol for human oocyte activation were critical to achieving development to the stage at which embryonic stem cells are derived. These findings are consistent with the 2013 report by Tachibana and colleagues that used foetal cells. Though the authors of the 2013 paper also performed studies with cells of an infant with Leigh syndrome, they did not demonstrate that diploid pluripotent stem cells could be derived from these cells. Because foetal cells are less mature than the cells after birth, it was critical to determine if diploid pluripotent stem cells could be derived from the cells of both infants and adults.

As an additional optimization of the SCNT protocol, the scientists found that it was important to maintain the integrity of the plasma membrane during manipulation, and that to do so, the agent used in the manipulations had to be at a low dose. The scientists applied this optimized protocol to skin cells of a male new-born and the cells of the adult patient with type 1 diabetes. From these two cell lines, the scientists produced a total of four SCNT-derived embryonic stem cell lines. All cell lines were diploid and could give rise to neurons, pancreatic cells, and cartilage, as well as various other cell types, demonstrating their pluripotency. Importantly, the cells of the type 1 diabetes patient also gave rise to insulin-producing beta cells.

Therefore, this is the first report of the derivation of diploid pluripotent stem cells from a patient. And together with a paper published this month in Cell Stem Cell by Chung et al., it is also the first report of diploid embryonic stem cell lines derived from a human after birth.

Dr. Nissim Benvenisty and his laboratory at Hebrew University of Jerusalem collaborated on this report by demonstrating that the cells produced were, in fact, embryonic stem cells by using microarrays to perform gene expression analysis of the cells.

Dr. Rudolph Leibel, a co-author and co-director with Dr. Robin Goland of the Naomi Berrie Diabetes Center, where aspects of these studies were conducted, said:

"This accomplishment is the product of an ongoing inter-institutional collaboration across scientific and clinical disciplines, supported by thoughtful philanthropy. The resulting technical and scientific insights bring closer the promise of cell replacement for a wide range of human disease."

NYSCF continues pursuing SCNT research despite many scientific obstacles and in light of the advent of induced pluripotent stem (iPS) cells, as it is not yet clear which type of stem cells will prove best for personalized treatments. Many thought that iPS cells, first created from human cells in 2007, would replace the need for patient-specific embryonic stem cells because they allow patient- and disease-specific stem cell lines to be generated by genetically reprogramming adult cells into becoming pluripotent cells. However, it is not clear how similar iPS cells are to naturally occurring embryonic stem cells, which remain the gold standard, and what will be the preferred cell type for therapies.

Though it is now possible to derive stem cell lines with a patient's genotype using iPS technology, the generation of stem cells using oocytes may have an advantage for use in cell replacement for diseases such as type 1 diabetes. The generation of pluripotent stem cell lines by SCNT uses human oocytes, while iPS cells use recombinant DNA, RNA, or chemicals, each of which requires its own safety testing and approval for clinical use. Human oocytes are already used routinely around the world to generate clinically relevant cells. The generation of pluripotent stem cell lines using human oocytes may therefore be particularly suitable for the development of cell-replacement therapies. Therefore, this work brings the scientists a significant step closer to this goal.

Drs. Mitsutoshi Yamada and Bjarki Johannesson, postdoctoral fellows at the NYSCF Research Institute, were the co-first authors of the paper.

Source: New York Stem Cell Foundation

Contact: David McKeon

Reference:

Human oocytes reprogram adult somatic nuclei of a type 1 diabetic to diploid pluripotent stem cells

Mitsutoshi Yamada, Bjarki Johannesson, Ido Sagi, Lisa Cole Burnett, Daniel H. Kort, Robert W. Prosser, Daniel Paull, Michael W. Nestor, Matthew Freeby, Ellen Greenberg, Robin S. Goland, Rudolph L. Leibel, Susan L. Solomon, Nissim Benvenisty, Mark V. Sauer& Dieter Egli

Nature 28 April 2014, doi:10.1038/nature13287

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Rewinding Development

A step forward for stem cell research

Thursday, 06 June 2013

Scientists at the Danish Stem Cell Center, DanStem, at the University of Copenhagen have discovered that they can make embryonic stem cells regress to a stage of development where they are able to make placenta cells as well as the other foetal cells. This significant discovery, published in the journal Cell Reports today, has the potential to shed new light on placenta related disorders that can lead to problematic pregnancies and miscarriages.

The picture shows a 9.5-day-old mouse
embryo including extra-embryonic tissue.
The red region marks embryonic stem cells
in the extra-embryonic yolk sac. Embryonic
stem cells are not normally able to do this,
but when cells are pushed backwards in
development as described in Morgani et al..
Credit: Sophie Morgani, University of
Copenhagen. 

Embryonic stem cells can make all kinds of adult cells in the human body such as muscle, blood or brain cells. However, these embryonic stem cells are created at a point when the embryo has already lost the ability to make extra-embryonic tissue such as placenta and yolk sac. Extra-embryonic tissues are formed at the very earliest stage of development right after fertilization and are essential for the growth of the embryo and its implantation in the womb.

A team of scientists at the Danish Stem Cell Center, DanStem, at the University of Copenhagen have shown that it is possible to rewind the developmental state of embryonic stem cells. By maintaining mouse embryonic stem cells under certain conditions, they found that cells appear to regress and resemble extremely early embryo cells that can form any kind of cell including placenta and yolk sac cells.

"It was a very exciting moment when we tested the theory," says Professor Josh Brickman from DanStem.

"We found that not only can we make adult cells but also placenta, in fact we got precursors of placenta, yolk sac as well as embryo from just one cell."

"This new discovery is crucial for the basic understanding of the nature of embryonic stem cells and could provide a way to model the development of the organism as a whole, rather than just the embryonic portion. In this way we may gain greater insight into conditions where extra-embryonic development is impaired, as in the case of miscarriages," added Sophie Morgani, PhD student at DanStem and first author of the paper.

LIF protein plays a crucial role

Brickman and colleagues grew their embryonic stem cells in a solution containing LIF, which is a protein known to somehow support embryonic stem cells but also for its role in implantation of the embryo into the uterus. As implantation is stimulated by the cells that will become the placenta, not the embryo, these roles appeared to be contradictory. The DanStem study resolved this contradiction by revealing that LIF helps maintain the cells in their regressed, early stage of development.

"In our study we have been able to see the full picture unifying LIF's functions: What LIF really does, is to support the very early embryo state, where the cells can make both embryonic cells and placenta. This fits with LIFs' role in supporting implantation," Josh Brickman says.

Source: University of Copenhagen 

Contact: Joshua Brickman

Reference:

Totipotent Embryonic Stem Cells Arise in Ground-State Culture Conditions

Sophie M. Morgani, Maurice A. Canham, Jennifer Nichols, Alexei A. Sharov, Rosa Portero Migueles, Minoru S.H. Ko, and Joshua M. Brickman
Cell Reports, 06 June 2013, 10.1016/j.celrep.2013.04.034

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Spine Function Improves Following Cell Replacement Therapy with Foetal Human Stem Cells

Spine Function Improves Following Cell Replacement Therapy with Foetal Human Stem Cells

Tuesday, 28 May 2013

Human foetal stem cell grafts improve both motor and sensory functions in rats suffering from a spinal cord injury, according to research published this week in BioMed Central's open access journal Stem Cell Research and Therapy. This cell replacement therapy also improves the structural integrity of the spine, providing a functional relay through the injury site. The research gives hope for the treatment of spinal cord injuries in humans.

Grafting human neural stem cells into the spine is a promising approach to promote the recovery of function after spinal injury. Sebastian van Gorp, from the University of California San Diego, and team's work looks specifically at the effect of intraspinal grafting of human foetal spinal cord-derived neural stem cells on the recovery of neurological function in a rats with acute lumbar compression injuries.

A total of 42 three month-old female Sprague-Dawley rats, with spinal compression injuries, were allocated to one of three groups. The rats in the first group received a spinal injection with the stem cells, those in the second group received a placebo injection, while those in the third group received no injection.

Treatment effectiveness was assessed by a combination of measures, including motor and sensory function tests, presence of muscle spasticity and rigidity which causes stiffness and limits residual movement. The team also evaluated of how well the grafted cells had integrated into the rodents' spines.

Gorp and colleagues found that, compared to rats who received either the placebo injection or no injection, those who received the stem cell grafts showed a progressive and significant improvement in gait/paw placement, reduced muscle spasticity as well as improved sensitivity to both mechanical and thermal stimuli. In addition to these behavioural benefits, the researchers observed long-term improvements in the structural integrity of previously injured spinal cord segments.

The authors say: "Importantly, spinal cavity formation and muscle spasticity are frequently observed in human patients with high-speed, high-impact induced spinal cord injuries. Our findings demonstrate that human foetal spinal cord-derived neural stem cells, with an already established favourable clinical safety profile, represent a potential cell candidate for cell replacement therapy in patients with traumatic spinal injuries."

Source: BioMed Central 

Contact: Hilary Glover

Reference:

Amelioration of motor/sensory dysfunction and spasticity in a rat model of acute lumbar spinal cord injury by human neural stem cell transplantation 

Sebastiaan van Gorp, Marjolein Leerink, Osamu Kakinohana, Oleksandr Platoshyn, Camila Santucci, Jan Galik, Elbert A Joosten, Marian Hruska-Plochan, Danielle Goldberg, Silvia Marsala, Karl Johe, Joseph D Ciacci and Martin Marsala 

Stem Cell Research & Therapy 2013 4:57

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First Evidence of Foetal DNA Persisting in Female Human Brain Tissue

Long-lasting foetal microchimerism in maternal brain is common, affects many brain regions

Thursday, 27 September 2012

Small portions of male DNA, most likely left over in a mother's body by a male foetus can be detected in the maternal brain relatively frequently, according to a report published Sep. 26 in the open access journal PLOS ONE by William Chan of Fred Hutchinson Cancer Research Center and his colleagues.

This shows a male cell in female human brain.

Credit: Citation: Chan WFN, Gurnot C, 

Montine TJ, Sonnen JA, Guthrie KA, et al. 

(2012) Male Microchimerism in the Human 

Female Brain. PLoS ONE 7(9): e45592, 

doi:10.1371/journal.pone.0045592.

The process, called foetal 'microchimerism (Mc)’, is common in other tissues such as blood, but this is the first evidence of male Mc in the human female brain. Microchimerism can be both beneficial and harmful to maternal health, since it is associated with processes such as tissue repair, as well as to autoimmune diseases.

Testing for the presence of a particular region of the Y-chromosome in autopsied brain tissues, the research team discovered that 63% of their samples showed potentially long-lasting Mc in multiple brain regions. They also found that women with Alzheimer's disease (AD) had less Mc than women without the disease.

According to the authors, this result warrants further investigation because previous reports have suggested that AD may be more prevalent in women with a higher number of pregnancies compared to childless women. The researchers commented that changes to the blood-brain barrier that occur during pregnancy could facilitate the process by which Mc is acquired into the human brain.

"This is the first evidence that microchimerism can cross the blood-brain barrier to establish male foetal tissue in the human female brain" says Chan.

Source: Public Library of Science 

Contact: Jyoti Madhusoodanan

Reference:

Male Microchimerism in the Human Female Brain 

Chan WFN, Gurnot C, Montine TJ, Sonnen JA, Guthrie KA, Nelson JL

PLoS ONE 7(9): e45592 (2012), doi:10.1371/journal.pone.0045592

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Microchimerism: Foetal Cells Can Migrate Into Maternal Organs During Pregnancy

Some mothers literally carry pieces of their children in their bodies

Saturday, 09 June 2012

A pregnant woman's blood stream contains not only her own cells, but a small number of her child's, as well, and some of them remain in her internal organs long after the baby is born. Understanding the origin and identity of these cells is vital to understanding their potential effects on a mother's long-term health. For example, foetal cells have been found at tumour sites in mothers, but it is unknown whether the cells are helping to destroy the tumour or to speed its growth.

Three types of foetal cells have now been identified in the lungs of late-term pregnant mice by a team led by Dr. Diana Bianchi of Tufts Medical Center. The research, published 6 June 2012 in Biology of Reproduction's Papers-in-Press, used publicly available databases to extract important genetic information from as few as 80 foetal cells. A combination of two different analytical techniques to characterize the rare foetal cells revealed a mixed population of trophoblasts (placental cells that provide nutrients to the foetus), mesenchymal stem cells (cells that later develop into fat, cartilage, or bone cells), and immune system cells.

Researchers suspect that foetal cells in a mother's blood stream help her immune system tolerate and not attack the foetus. The detection of trophoblasts and immune cells in the maternal lung should aid future studies on this subject, as well as research into pregnancy-related complications like preeclampsia. The presence of foetal mesenchymal stem cells corresponds with previous studies that reported foetal and placental cells differentiating to repair injured maternal organs in both mice and humans.

Using this team's techniques of gene expression analysis, researchers should now be better able to identify the types of cells present in maternal organs and in doing so determine their potential short- and long-term effects on a mother's internal systems.

Source: Society for the Study of Reproduction 

Contact: Jeremy Lechan

Reference:

Comprehensive analysis of genes expressed by rare microchimeric fetal cells in maternal lung

Pritchard S, Wick HC, Slonim DK, Johnson KL, Bianchi DW.

Biol Reprod 2012; Published online ahead of print 6 June 2012; DOI 10.1095/biolreprod.112.101147

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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at

http://cellnews-blog.blogspot.com/

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Embryonic Stem Cells Shift Metabolism in Cancer-like Way upon Implanting in Uterus

Switch may release fuel and materials for rapid growth and formation of layers that later become organs 
Friday, 23 March 2012

This is stem cell biologist Dr. Hannele
Ruohola-Baker of the University of
Washington in Seattle. Credit: Univ.
of Wash..

Shortly after a mouse embryo starts to form, some of its stem cells undergo a dramatic metabolic shift to enter the next stage of development, Seattle researchers report today. These stem cells start using and producing energy like cancer cells.

This discovery is published today in EMBO Journal, the European Molecular Biology Organization journal.

"These findings not only have implications for stem cell research and the study of how embryos grow and take shape, but also for cancer therapy," said the senior author of the study, Dr. Hannele Ruohola-Baker, University of Washington professor of biochemistry. The study was collaborative among several research labs in Seattle.

The metabolic transition they discovered occurs very early as the mouse embryo, barely more than a speck of dividing cells, implants in the mother's uterus. The change is driven by low oxygen conditions, Ruohola-Baker explained.

The researchers also saw a specific type of biochemical slowdown in the stem cells' mitochondria – the cells' powerhouses. The phenomenon previously was associated with aging and disease. This was the first example of the same downshift controlling normal early embryonic development.

This is a microscopic image from the mouse
embryonic stem cell metabolism study in
Seattle. Credit: Hannele Ruohola-Baker lab.

"This downshift coincides with the time when the germ line, the keeper of the genome for the next generation, is set aside," Ruohola-Baker said.

"Hence reduction of mitochondrial reactive oxygen species may be nature's way to protect the future."

Embryonic stem cells are called pluripotent because they have the ability to renew themselves and have the potential to become any cell in the body. Self-sustaining and versatile are qualities necessary for the growth, repair and maintenance of the body – and for regenerative medicine therapies.

Although they share these sought-after qualities, "Pluripotent stem cells come in several flavours," Ruohola-Baker explained. They differ in subtle ways that expand or shrink their capacities as the raw living material from which animals are shaped.

There's a big reason why the researchers wanted to understand the distinction between the stem cells that make up the inner cell mass of the free-floating mouse embryo, and those in the epiblast, or implantation stage. Mouse embryonic cells at the epiblast stage more closely resemble human embryonic stem cells - and cancer cells.

Human stem cells and mouse epiblast stem cells have lower mitochondrial respiration activity than do earlier stage mouse stem cells. This reduction occurs despite the fact that the later stage stem cells have more mature mitochondria. The researchers confirmed that certain genes that control mitochondria are turned down during the transition from inner cells mass to epiblast cells.

Instead, the transitioning cells obtain their energy exclusively from breaking down a sugar, glucose. In contrast, the earlier stage mouse embryonic stem cells have more energy options, dynamically switching from mitochondrial respiration to glucose breakdown on demand.

As the embryo enlarges from a few dividing cells to a dense mass that buries into uterus for further development, oxygen comes at a premium.

The researchers discovered that the low-oxygen conditions activate a transcription factor called hypoxia-inducible factor 1alpha. This factor is sufficient to drive mouse embryonic stem cells to rely exclusively on glucose metabolism for their energy. The next challenge is to reveal whether the metabolic switch is deterministic for the fate of these stem cells, in normal as well as in cancer development.

This forced metabolic switch may determine the functional fate of some of the tiny mass of cells making up the primordial embryo. They transition first into epiblast stem cells and, afterward produce the entire developing embryo.

In cancer cells, the shift to a sugar-busting metabolism is known as the Warburg effect, the researchers explain. The Warburg effect sets in motion the biochemical activities that provide the fuel and materials required for rapid tumour cell growth and division.

The Warburg effect in embryonic cells, the researcher proposed, "may serve a similar function in preparation for the dramatic burst of embryonic growth and for the formation of the layers of the early embryo that later will become organs and other body structures."

Source: University of Washington

Contact: Leila Gray

Reference:

HIF1α induced switch from bivalent to exclusively glycolytic metabolism during ESC-to-EpiSC/hESC transition
Wenyu Zhou, Michael Choi, Daciana Margineantu, Lilyana Margaretha, Jennifer Hesson, Christopher Cavanaugh, C Anthony Blau, Marshall S Horwitz, David Hockenbery, Carol Ware and Hannele Ruohola-Baker
The EMBO Journal advance online publication 23 March 2012; doi:10.1038/emboj.2012.71
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ZenMaster

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For more on stem cells and cloning, go to CellNEWS at
http://cellnews-blog.blogspot.com/

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