Saturday, 26 July 2014
Researchers Create 'Naïve' Pluripotent Human Embryonic Stem Cells
Saturday, 26 July 2014
For years, researchers and patients have hoped that embryonic stem cells (ESCs) — capable of forming nearly any cell type in the body — could provide insight into numerous diseases perhaps even be used to treat them. Yet progress has been hampered by the inability to transfer research and tools from mouse ESC studies to their human counterparts, in part because human ESCs are "primed" and slightly less plastic than the mouse cells.
Now Thorold Theunissen, Benjamin Powell, and Haoyi Wang, who are scientists in the lab of Whitehead Institute Founding Member Rudolf Jaenisch, have discovered how to manipulate and maintain human ESCs in a "naïve" or base pluripotent state similar to that of mouse ESCs without the use of any reprogramming factors. Their work is described in this week's issue of the journal Cell Stem Cell.
Naïve mice ESCs are well-studied, and scientists have a strong understanding of how they function and mature into more specialized cells. But this understanding is of limited use in human ESC research, as the human cells look different, grow differently, and rely on different genes than mouse ESCs. According to Theunissen, the disparities between mouse and human ESCs are attributable not to species-specific differences but rather to differences of cell state.
In naïve mouse ESCs, a particular enhancer of the gene OCT4 is active, prompting the researchers to look for the presence of this marker as a means to identify rare naïve human ESCs. With this unbiased reporter system in hand, the Jaenisch team determined that a cocktail of five small molecules with a few additional growth factors can induce and support the conversion of primed human ESCs to a naïve state with or without using reprogramming factors to jumpstart the process.
By applying this cocktail to human blastocysts, the scientists could also isolate naïve human stem cells.
"This is important because if this cocktail only works in existing lines of human ESCs, you might wonder, does this really capture a distinct state or is this artificial?" says Theunissen.
"Since the cocktail works directly on human blastocysts, I think it suggests that we're really capturing a cell state that is already present in the early human embryo."
Although other labs have recently reported creating naïve human ESCs, Theunissen, Powell, and Wang question these results as the cells produced through these techniques lack the gene expression and epigenetic profiles of naïve human ESCs. Yet, the Jaenisch lab believes they have now finally unlocked a way to create and maintain this important type of cell and are looking forward to exploring its potential.
"We have discovered a new pathway to generate something we believe is a totally different state of pluripotency in human ESCs that is very close to the mouse naïve state," says Jaenisch, who is also a professor of biology at MIT.
"These cells may be essential for ESC technology, and that is an area we're looking forward to investigating. Now the big question for us is, does this state exist in vivo in embryos? Right now, we don't know, and that is a very interesting line of research."
Contact: Nicole Giese Rura
Systematic Identification of Culture Conditions for Induction and Maintenance of Naive Human Pluripotency
Thorold W. Theunissen, Benjamin E. Powell, Haoyi Wang, Maya Mitalipova, Dina A. Faddah, Jessica Reddy, Zi Peng Fan, Dorothea Maetzel, Kibibi Ganz, Linyu Shi, Tenzin Lungjangwa, Sumeth Imsoonthornruksa, Yonatan Stelzer, Sudharshan Rangarajan, Ana D'Alessio, Jianming Zhang, Qing Gao, Meelad M. Dawlaty, Richard A. Young, Nathanael S. Gray, and Rudolf Jaenisch
Cell Stem Cell, July 24, 2014, http://www.cell.com/cell-stem-cell/abstract/S1934-5909(14)00298-7
For more on stem cells and cloning, go to CellNEWS at
Thursday, 17 July 2014
From: Al Jazeera America’s TECHKNOW Presents
Thursday, 17 July 2014
This Saturday, July 19th at 7:30 pm ET/4:30 pm PT, Al Jazeera America’s “TechKnow” shows us one of the most exiting areas of medical research – how umbilical cord blood is being used to treat brain disease and injury.
|Dr. Joanne Kurtzberg. Credit: Al Jazeera.|
The medical equivalent of gold, we’re just at the tip of understanding how stem cells from cord blood, harvested at the time of birth, can be used to help the brain regenerate and heal from injuries and damage.
“I personally believe cell therapy, and regenerative medicine, is going to be the next big advance in medicine, and that cells like cord blood are going to drive that forward,” reports Dr. Joanne Kurtzberg, Chief of the Division of Pediatric Blood and Marrow Transplantation at Duke University Medical Center in Durham, North Carolina.
The program is airing Saturday, July 19th at 7:30PET/4:30P PT;
Repeats 10:30P ET/7:30P PT
Find Al Jazeera America near you: www.aljazeera.com/getajam
About Al Jazeera America’s “TechKnow”:
Al Jazeera America’s “TechKnow” is a half hour documentary show that airs weekly on Saturdays at 7:30 pm ET/4:30 pm PT. A show about innovations that can change lives, “TechKnow” explores the intersection of hardware and humanity in a unique way – it’s a show about science, by scientists. “TechKnow” rotating cast of hosts includes mechanical engineer Dr. Shini Somara, molecular neuroscientist Dr. Crystal Dilworth, entolomologist Phil Torres, biologist Marita Davison, engineer Kosta Grammatis, science writer Kyle Hill, former CIA operative and analyst Lindsay Moran, neuroscientist Rachelle Oldmixon and neurobiologist Cara Santa Maria.
Source: Al Jazeera America’s “TechKnow”
Contact: Jocelyn Austin, Director, Publicity
For more on stem cells and cloning, go to CellNEWS at
Thursday, 3 July 2014
Nuclear transfer appears superior for creating embryonic stem cells
Thursday, 03 July 2014
Researchers around the world have turned to stem cells, which have the potential to develop into any cell type in the body, for potential regenerative and disease therapeutics.
Now, for the first time, researchers at the Salk Institute, with collaborators from Oregon Health & Science University and the University of California, San Diego, have shown that stem cells created using two different methods are far from identical. The finding could lead to improved avenues for developing stem cell therapies as well as a better understanding of the basic biology of stem cells.
The researchers discovered that stem cells created by moving genetic material from a skin cell into an empty egg cell — rather than coaxing adult cells back to their embryonic state by artificially turning on a small number of genes — more closely resemble human embryonic stem cells, which are considered the gold standard in the field.
Joseph R. Ecker, Professor, Genomic Analysis
Laboratory. Credit: Courtesy of the Salk
Institute for Biological Studies.
Human embryonic stem cells (hESCs) are directly pulled from unused embryos discarded from in-vitro fertilization, but ethical and logistical quandaries have restricted their access. In the United States, federal funds have limited the use of hESCs so researchers have turned to other methods to create stem cells. Most commonly, scientists create induced pluripotent stem (iPS) cells by starting with adult cells (often from the skin) and adding a mixture of genes that, when expressed, regress the cells to a pluripotent stem-cell state. Researchers can then coax the new stem cells to develop into cells that resemble those in the brain or in the heart, giving scientists a valuable model for studying human disease in the lab.
Over the past year, a team at OHSU built upon a technique called somatic cell nuclear transfer (the same that is used for cloning an organism, such as Dolly the sheep) to transplant the DNA-containing nucleus of a skin cell into an empty human egg, which then naturally matures into a group of stem cells.
Ecker, holder of the Salk International Council Chair in Genetics, teamed up with Shoukhrat Mitalipov, developer of the new technique and director of the Center for Embryonic Cell and Gene Therapy at OHSU, and UCSD assistant professor Louise Laurent to carry out the first direct comparison of the two approaches. The scientists created four lines of nuclear transfer stem cells all using eggs from a single donor, along with seven lines of iPS cells and two lines of the gold standard hESCs. All cell lines were shown to be able to develop into multiple cell types and had nearly identical DNA content contained within them.
But when they looked closer at the cells, the researchers spotted some differences: the patterns of methylation — chemical flags that are added to genes to control their expression — varied between the cell lines. This indicates a difference in how and when genes, despite having identical sequences, might be expressed. The methylation of nuclear transfer cells more closely resembled hESCs than the iPS cells did. And when the investigators looked at patterns of actual gene expression — by measuring the levels of particular RNA strands produced by each cell — the differences continued. Once again, nuclear transfer cells had RNA levels closer to embryonic cells, making them more accurate for basic research and therapeutic studies.
"Both the DNA methylation and gene expression data show that nuclear transfer does a better job at erasing the signature of the original skin cell," says Laurent, who is a co-senior author of the paper.
"If you believe that gene expression is important, which we do, then the closer you get to the gene expression patterns of embryonic stem cells, the better," Ecker says.
"Right now, nuclear transfer cells look closer to the embryonic stem cells than do the iPS cells."
Ecker doesn't expect labs to race to make the switch to nuclear transfer protocols — after all, the method falls within those restricted for federal funding. But he thinks the new observation likely holds lessons that could help improve the protocols for making iPS cells.
"What this is telling us is that you can use the standard mix of genes and they do a pretty good job of creating iPS cells," Ecker says.
"But they're not perfect. The material in an egg does a better job than just those four genes alone."
If researchers can pin down what it is within an egg that drives the production of pluripotent stem cells, they may be able to integrate that knowledge into iPS methods to improve stem cell therapy for disease.
"At this point, nuclear transfer stem cells combine the key advantages of both hESCs and iPS cells and, as such, are ideal for clinical applications in regenerative therapy," adds Mitalipov.
Other researchers on the study were Ryan C. O'Neil, Yupeng He, Matthew D. Schultz, Manoj Heriharan, Joseph R. Nery, and Rosa Castanon of the Salk Institute for Biological Studies; Hong Ma, Brittany Daughtry, Masahito Tachibana, Eunju Kang, Rebecca Tippner-Hedges, Riffat Ahmed, Nuria Marti Gutierrez, Crystal Van Dyken, Alimujiang Fulati, Atsushi Sugawara, Michelle Sparman, Paula Amato and Don P. Wolf of Oregon Health & Science University; Robert Morey, Karen Sabatini and Rathi D. Thiagarajan of the University of California, San Diego; and Sumita Gokhale of the Boston University School of Medicine.
Contact: Kristina Grifantini
Abnormalities in human pluripotent cells due to reprogramming mechanisms
Hong Ma, Robert Morey, Ryan C. O'Neil, Yupeng He, Brittany Daughtry, Matthew D. Schultz, Manoj Hariharan, Joseph R. Nery, Rosa Castanon, Karen Sabatini, Rathi D. Thiagarajan, Masahito Tachibana, Eunju Kang, Rebecca Tippner-Hedges, Riffat Ahmed, Nuria Marti Gutierrez, Crystal Van Dyken, Alim Polat, Atsushi Sugawara, Michelle Sparman, Sumita Gokhale, Paula Amato, Don P.Wolf, Joseph R. Ecker, Louise C. Laurent & Shoukhrat Mitalipov
Nature (2014), doi:10.1038/nature13551
For more on stem cells and cloning, go to CellNEWS athttp://cellnews-blog.blogspot.com/