Chemical-only Cell Reprogramming Transforms Human and Mouse Skin Cells into Neurons

Chemical-only Cell Reprogramming Transforms Human and Mouse Skin Cells into Neurons

Friday, 07 August 2015

Two labs in China have independently succeeded in transforming skin cells into neurons using only a cocktail of chemicals, with one group using human cells from healthy individuals and Alzheimer's patients, and the other group using cells from mice. The two studies reinforce the idea that a purely chemical approach is a promising way to scale up cell reprogramming research that may avoid the technical challenges and safety concerns associated with the more popular method of using transcription factors. Both papers appear on August 6 in the journal Cell Stem Cell.

One of the challenges of forcing cells to change identity is that the cells you end up with may look normal but have different internal activities than their naturally forming counterparts. The two papers provide evidence that similar gene expression, action potentials, and synapse formation can be detected in transcription-factor-induced neurons as those generated from the chemical cocktails. (Both groups used mixtures of seven small molecules, but different recipes – outlined in detail in the supplemental information section of each paper – because they focused on different species.)

This is an image of mouse chemical-induced

neurons. Credit: Courtesy of Hongkui Deng.

"We found that the conversion process induced by our chemical strategy is accompanied by the down-regulation of [skin-cell] specific genes and the increased expression of neuronal transcription factors," said human study co-author Jian Zhao, of the Shanghai Institutes for Biological Sciences and Tongji University.

"By coordinating multiple signalling pathways, these small molecules modulate neuronal transcription factor gene expression and thereby promote the neuronal cell transition."

The authors add that the direct conversion bypasses a proliferative intermediate progenitor stage, which circumvents safety issues posed by other reprogramming methods.

This is an image of human chemical induced

neurons. Credit: Courtesy of Gang Pei and

Jian Zhao.

Zhao's paper, co-led with cell biologist Gang Pei, also shows that the pure chemical protocol can be used to make neurons from the skins cells of Alzheimer's patients. Most of the work using patient stem cells has been done by using transcription factors – molecules that affect which genes are expressed in a cell – to create induced pluripotent stem cells. Chemical cell reprogramming is seen as an alternative for disease modelling or even potential cell replacement therapy of neurological disorders, but the "proof-of-concept" is still emerging.

"In comparison with using transgenic reprogramming factors, the small molecules that are used in this chemical approach are cell permeable; cost-effective; and easy to synthesize, preserve, and standardize; and their effects can be reversible," says mouse study co-author Hongkui Deng of the Peking University Stem Cell Research Center.

"In addition, the use of small molecules can be fine-tuned by adjusting their concentrations and duration, and the approach bypasses the technical challenges and safety concerns of genetic manipulations, which may be promising in their future applications."

Deng worked for four years with Zhen Chai and Yang Zhao, also of Peking University, to identify the small molecules that could create chemically induced mouse neurons. Researchers had been close for years, but a transcription factor was always necessary to complete the transformation. Through many chemical screens they identified the key ingredient, I-BET151, which works to suppress transcription in skin cells. They then found the right steps and conditions to mature the neurons post-transformation.

The authors of both papers aim to learn more about the biology behind chemically induced reprogramming and to make the protocols more efficient. While their success is promising, there are still a number of hurdles to overcome.

"We hope in the future that the chemical approaches would be more robust in inducing functional mature neurons," Deng says.

"In addition, we are attempting to generate specific neuronal subtypes and patient-specific functional neurons for translational medicine by using pure chemicals."

Jian Zhao, of the human study, says:

"It should be possible to generate different subtypes of neurons with a similar chemical approach but using slightly modified chemical cocktails."

"It also needs to be explored whether functional neurons could be induced by chemical cocktails in living organisms with neurological diseases or injury," she adds.

Source: Cell Press

Contact: Joseph Caputo

References:

Small-Molecule-Driven Direct Reprogramming of Mouse Fibroblasts into Functional Neurons

Xiang Li, Xiaohan Zuo, Junzhan Jing, Yantao Ma, Jiaming Wang, Defang Liu, Jialiang Zhu, Xiaomin Du, Liang Xiong, Yuanyuan Du, Jun Xu, Xiong Xiao, Jinlin Wang, Zhen Chai, Yang Zhao, Hongkui Deng

Cell Stem Cell Volume 17, Issue 2, p195–203, 6 August 2015

Direct Conversion of Normal and Alzheimer's Disease Human Fibroblasts into Neuronal Cells by Small Molecules

Wenxiang Hu, Binlong Qiu, Wuqiang Guan, Qinying Wang, Min Wang, Wei Li, Longfei Gao, Lu Shen, Yin Huang, Gangcai Xie, Hanzhi Zhao, Ying Jin, Beisha Tang, Yongchun Yu, Jian Zhao, Gang Pei

Cell Stem Cell Volume 17, Issue 2, p204–212, 6 August 2015

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Recovery of Sensory Function by Stem Cell Transplants

Recovery of Sensory Function by Stem Cell Transplants

Monday, 08 June 2015

New research from Uppsala University shows promising progress in the use of stem cells for treatment of spinal cord injury. The results, which are published in the scientific journal Scientific Reports, show that human stem cells that are transplanted to the injured spinal cord contribute to restoration of some sensory functions.

Traffic accidents and severe falls can cause ruptures of nerve fibres that enter/exit the spinal cord. Most commonly, these avulsion injuries affect the innervation of the arm and hand, and lead to paralysis, loss of sensation and cause chronic pain. Surgical interventions can help the patient regain some muscle function, but there is currently no treatment able to restore sensory functions. The reason for this is the emergence of a "barrier" at the junction between the ruptured nerve fibres and the spinal cord which prevents them from growing into the spinal cord and restore lost nerve connections.

In a new study the PhD students Jan Hoeber, Niclas König and Carl Trolle, working in Dr.Elena Kozlova's research group transplanted human stem cells to an avulsion injury in mice with the aim to restore a functional route for sensory information from peripheral tissues into the spinal cord.

The results show that the transplanted stem cells act as a "bridge" which allows injured sensory nerve fibres to grow into the spinal cord, rebuilds functional nerve connections, and thereby achieve long term restoration of major parts of the lost sensory functions. The transplanted stem cells differentiated to different types of cells with variable level of maturation, specific for the nervous system. No signs of tumour development or any functional abnormalities from the transplants were observed in the study, outcomes which are important in view of potential risks with transplantation of embryonic stem cells.

The results encourage further research on the use of stem cells for treatment of injury and disease in the spinal cord, and may contribute to the development of novel treatment strategies in these disorders.

Source: Uppsala University

Contact: Elena Kozlova

Reference:

Human embryonic stem cell-derived progenitors assist functional sensory regeneration after dorsal root avulsion injury

Hoeber J, Trolle C, König N, Du Z, Gallo A, Hermans E, Aldskogius H, Shortland P, Zheng, S-C, Deumens R, Kozlova EN. 

Scientific Reports 5, 08 June 2015, Article number: 10666, doi:10.1038/srep10666

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Master Orchestrator of the Genome Is Discovered

Master Orchestrator of the Genome Is Discovered

Thursday, 07 May 2015

One of developmental biology’s most perplexing questions concerns what signals transform masses of undifferentiated cells into tremendously complex organisms, a process called ontogeny.

UB research suggests a new paradigm, visualized

in this diagram, for developmental global genome

programming by the nuclear FGFR1 protein.

New research by University at Buffalo scientists, published last week in PLOS ONE, provides evidence that it all begins with a single “master” growth factor receptor that regulates the entire genome.

“The finding provides a new level of understanding of the fundamental aspects of how organisms develop,” says senior author Michal K. Stachowiak, PhD, professor in the Department of Pathology and Anatomical Sciences in the UB School of Medicine and Biomedical Sciences and senior author. He also directs the Stem Cell Engraftment and In Vivo Analysis Facility and the Stem Cell Culture and Training Facility at the Western New York Stem Cell Culture and Analysis Center at UB.

“Our research shows how a single growth factor receptor protein moves directly to the nucleus in order to program the entire genome,” he said.

Michal Stachowiak, PhD, Professor, Department

of Pathology and Anatomical Sciences. 

The research challenges a long-held supposition in biology that specific types of growth factors only functioned at a cell’s surface. For two decades, Stachowiak’s team has been intrigued by the possibility that growth factors function from within the nucleus, a point, he says, this current paper finally proves.

A more advanced understanding of how organisms form, based on this work, has the potential to significantly enhance the understanding and treatment of cancers, which result from uncontrolled development as well as congenital diseases, the researchers say. The new research also will contribute to the understanding of how stem cells work.

This work was conducted on mouse embryonic stem cells, not human cells.

Organizing ‘this cacophony of genes’

“We’ve known that the human body has almost 30,000 genes that must be controlled by thousands of transcription factors that bind to those genes,” Stachowiak said, “yet we didn’t understand how the activities of genes were coordinated so that they properly develop into an organism.”

“Now we think we have discovered what may be the most important player, which organizes this cacophony of genes into a symphony of biological development with logical pathways and circuits,” he said.

At the centre of the discovery is a single protein called nuclear Fibroblast Growth Factor Receptor 1 (nFGFR1).

“FGFR1 occupies a position at the top of the gene hierarchy that directs the development of multicellular animals,” said Stachowiak.

The FGFR1 gene is known to govern gastrulation, occurring in early development, where the three-layered embryonic structure forms. It also plays a major role in the development of the central and peripheral nervous systems and the development of the body’s major systems, including muscles and bones.

To study how nuclear FGFR1 worked, the UB team used genome-wide sequencing of mouse embryonic stem cells programmed to develop cells of the nervous system, with additional experiments in which nuclear FGFR1 was either introduced or blocked. The researchers found that the protein was responsible, either alone or with so-called partner nuclear receptors, for ensuring that embryonic stem cells develop into differentiated cells. By targeting thousands of genes, it controls the development of the major points of growth in the body (known as axes) as well as neuronal and muscle development.

The research shows that nuclear FGFR1 binds to promoters of genes that encode transcription factors, the proteins that control which genes are turned on or off in the genome.

“We found that this protein works as a kind of ‘orchestration factor,’ preferably targeting certain gene promoters and enhancers. The idea that a single protein could bind thousands of genes and then organize them into a hierarchy, that was unknown,” Stachowiak said.

“Nobody predicted it.”

Sequencing advances

The discovery that a single protein can exert such a global genomic function stems from recent advances in DNA sequencing technologies, which allow for the sequencing of a complex genome in just hours.

“NextGen DNA sequencing allows us to analyse millions of DNA sequences selected by the interacting protein,” Stachowiak said.

In the UB research, the DNA sequencing data were processed by the supercomputer at the university’s Center for Computational Research (CCR). Stachowiak and his colleagues then spent weeks aligning these data to the genome and conducting further analyses.

“We imposed nuclear FGFR1 on every little corner of genome,” he said.

“The computer spit out which genes are affected by nuclear FGFR1: it was an enormously complex network of genome activity.”

They found that the protein binds to genes that make neurons and muscles as well as to an important oncogene, TP63, which is involved in a number of common cancers.

Other studies in Stachowiak’s laboratory demonstrate that these interactions also take place in the human genome, controlling function and possibly underlying diseases like schizophrenia. Targeting of the nuclear FGFR1 allows for the reactivation of neural development in the adult brain in preclinical studies and thus, Stachowiak says, may offer unprecedented opportunity for regenerative medicine. Nuclear accumulation of nuclear FGFR1 may be altered in some cancer cells, and thus could become a focus in cancer therapy, he added.  

“This seminal discovery lends new perspectives to the origin, nature and treatment of a variety of human disease,” Stachowiak concluded.

Source: University at Buffalo, New York

Contact: Ellen Goldbaum

Reference:

Global Developmental Gene Programing Involves a Nuclear Form of Fibroblast Growth Factor Receptor-1 (FGFR1)

Christopher Terranova,Sridhar T. Narla, Yu-Wei Lee, Jonathan Bard, Abhirath Parikh, Ewa K. Stachowiak, Emmanuel S. Tzanakakis, Michael J. Buck, Barbara Birkaya, Michal K. Stachowiak

PLoS ONE 2015 10(4):e0123380, doi:10.1371/journal.pone.0123380

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New Stem Cell May Overcome Hurdles for Regenerative Medicine

Salk Institute scientists discover new type of stem cell that could potentially generate mature, functional tissues

Thursday, 07 May 2015

In this image, a novel type of human stem cell is

shown in green integrating and developing into

the surrounding cells of a nonviable mouse

embryo. Red indicates cells of endoderm lineage.

Endoderm cells can give rise to tissue that covers

organs from the digestive and respiratory

systems. The new stem cell, developed at the

Salk Institute, holds promise for one day growing

replacement functional cells and tissues. Credit:

Courtesy of the Salk Institute for Biological

Studies.

Scientists at the Salk Institute have discovered a novel type of pluripotent stem cell – cells capable of developing into any type of tissue – whose identity is tied to their location in a developing embryo. This contrasts with stem cells traditionally used in scientific study, which are characterized by their time-related stage of development.

In the paper, published May 6, 2015 in Nature, the scientists report using these new stem cells to develop the first reliable method for integrating human stem cells into nonviable mouse embryos in a laboratory dish in such a way that the human cells began to differentiate into early-stage tissues.

“The region-specific cells we found could provide tremendous advantages in the laboratory to study development, evolution and disease, and may offer avenues for generating novel therapies,” says Salk Professor Juan Carlos Izpisua Belmonte, senior author of the paper and holder of Salk’s Roger Guillemin Chair.

The researchers dubbed this new class of cells “region-selective pluripotent stem cells,” or rsPSCs for short. The rsPSCs were easier to grow in the laboratory than conventional human pluripotent stem cells and offered advantages for large-scale production and gene editing (altering a cell’s DNA), both desirable features for cell replacement therapies.

Juan Carlos Izpisua Belmonte and Jun Wu

Credit: Courtesy of the Salk Institute for

Biological Studies.

To produce the cells, the Salk scientists developed a combination of chemical signals that directed human stem cells in a laboratory dish to become spatially oriented.

They then inserted the spatially oriented human stem cells (human rsPSCs) into specific regions of partially dissected mouse embryos and cultured them in a dish for 36 hours. Separately, they also inserted human stem cells cultured using conventional methods, so that they could compare existing techniques to their new technique.

While the human stem cells derived through conventional methods failed to integrate into the modified embryos, the human rsPSCs began to develop into early stage tissues. The cells in this region of an early embryo undergo dynamic changes to give rise to all cells, tissues and organs of the body. Indeed the human rsPSCs began the process of differentiating into the three major cell layers in early development, known as ectoderm, mesoderm and endoderm. The Salk researchers stopped the cells from differentiating further, but each germ layer was theoretically capable of giving rise to specific tissues and organs.

The new stem cell (green), developed at the Salk

Institute, holds promise for one day growing

replacement functional cells and tissues. Credit:

Courtesy of the Salk Institute for Biological

Studies.

Collaborating with the labs of Salk Professors Joseph Ecker and Alan Saghatelian, the Izpisua Belmonte team performed extensive characterization of the new cells and found rsPSCs showed distinct molecular and metabolic characteristics as well as novel epigenetic signatures – that is, patterns of chemical modifications to DNA that control which genes are turned on or off without changing the DNA sequence.

“The region selective-state of these stem cells is entirely novel for laboratory-cultured stem cells and offers important insight into how human stem cells might be differentiated into derivatives that give rise to a wide range of tissues and organs,” says Jun Wu, a postdoctoral researcher in Izpisua Belmonte’s lab and first author of the new paper.

“Not only do we need to consider the timing, but also the spatial characteristics of the stem cells. Understanding both aspects of a stem cell’s identity could be crucial to generate functional and mature cell types for regenerative medicine.”

Source: Salk Institute

Contact: Salk Communications

Reference:

An alternative pluripotent state confers interspecies chimaeric competency

Authors: Jun Wu, Daiji Okamura, Mo Li, Keiichiro Suzuki, Chongyuan Luo,Li Ma, Yupeng He, Zhongwei Li, Chris Benner, Isao Tamura, Marie N. Krause, Joseph R. Nery, Tingting Du, Zhuzhu Zhang, Tomoaki Hishida, Yuta Takahashi, Emi Aizawa, Na Young Kim, Jeronimo Lajara, Pedro Guillen, Josep M. Campistol, Concepcion Rodriguez Esteban, Pablo J. Ross, Alan Saghatelian, Bing Ren, Joseph R. Ecker and Juan Carlos Izpisua Belmonte

Nature, 06 May 2015, doi:10.1038/nature14413

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Mammalian Heart Regenerative Capacity Depends on Severity of Injury

Full recovery and normal function restored in mouse models following mild injury

Friday, 23 January 2015

This is a neonatal mouse heart showing basal

level of proliferating cardiomyocytes. (Red-

cardiomyocytes; Green- proliferating

cardiomyocytes; RV-right ventricle; LV-left

ventricle.) Credit: The Saban Research Institute

of Children's Hospital Los Angeles. 

A new study by researchers at Children's Hospital Los Angeles has shown that neonatal mouse hearts have varying regenerative capacities depending upon the severity of injury. Using cryo-injury - damaging the heart through exposure to extreme cold in order to mimic cellular injury caused by myocardial infarction - investigators found that neonatal mouse hearts can fully recover normal function following a mild injury, though fail to regenerate after a severe injury.

Published online by the journal Developmental Biology, the study suggests that cardiac regeneration strategies should be based on the type and severity of heart injury.

"Using models such as zebrafish and neonatal mice that regenerate their hearts naturally, we can begin to identify important molecules that enhance heart repair," said Ellen Lien, PhD, of The Saban Research Institute of Children's Hospital Los Angeles. Lien, who was senior author on the paper, is also an assistant professor at the Keck School of Medicine of the University of Southern California.

New born mice have shown the capacity for heart regeneration, but it is rapidly lost by seven days after birth. Approaches to extend this regenerative capacity in a mammalian model, from the neonatal period to the juvenile or adult period, could help identify new treatment options for humans.

Acute myocardial infarction, commonly known as a heart attack, can be classified according to the extent of damage to the heart muscle. Severe, or trans-mural injury, is associated with a blood supply blockage to the full thickness of the heart. Non-trans-mural injury indicates a blockage that penetrates only partially through the heart muscle. The investigators were able to develop models for both types of injury.

In addition to differences in regenerative capacity, the investigators also found an indicator of tissue fibrosis or "scarring", profibrotic marker PAI-1, was markedly elevated only after trans-mural injury. In both models post-injury, the cells that form heart muscle, cardiomyocytes, did not increase significantly. However, responses to cardiac injury repair in the outer layer of the heart (epicardium) and blood vessels (revascularization) - were present.

"If we can figure out how to activate this youthful type of myocardial regeneration program in humans, it will be a major clinical breakthrough," said David Warburton, OBE, DSc, MD, director of Developmental Biology and Regenerative Medicine at The Saban Research Institute of CHLA. Warburton is also a professor at the Keck School of Medicine of USC and was co-author on the paper.

Source: Children's Hospital Los Angeles

Contact: Jennifer Jing

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Stem Cells Faulty in Duchenne Muscular Dystrophy

Stem Cells Faulty in Duchenne Muscular Dystrophy

Thursday, 18 December 2014

Like human patients, mice with a form of Duchenne muscular dystrophy undergo progressive muscle degeneration and accumulate connective tissue as they age. Now, researchers at the Stanford University School of Medicine have found that the fault may lie at least partly in the stem cells that surround the muscle fibres.

They've found that during the course of the disease, the stem cells become less able to make new muscle and instead begin to express genes involved in the formation of connective tissue. Excess connective tissue – a condition called fibrosis – can accumulate in many organs, including the lungs, liver and heart, in many different disorders. In the skeletal muscles of people with muscular dystrophy, the fibrotic tissue impairs the function of the muscle fibres and leads to increasing weakness and stiffness, which are hallmarks of the disease.

The researchers discovered that this abnormal change in stem cells could be inhibited in laboratory mice by giving the animals a drug that is already approved for use in humans. The drug works by blocking a signalling pathway involved in the development of fibrosis. Although much more research is needed, the scientists are hopeful that a similar approach may one day work in children with muscular dystrophy.

"These cells are losing their ability to produce muscle, and are beginning to look more like fibroblasts, which secrete connective tissue," said Thomas Rando, MD, PhD, professor of neurology and neurological sciences.

"It's possible that if we could prevent this transition in the muscle stem cells, we could slow or ameliorate the fibrosis seen in muscular dystrophy in humans."

A paper describing the researchers' findings will be published Dec. 17 in Science Translational Medicine. Rando, the paper's senior author, is director of the Glenn Laboratories for the Biology of Aging and founding director of the Muscular Dystrophy Association Clinic at Stanford. Former postdoctoral scholar Stefano Biressi, PhD, is the lead author. Biressi is now at the Centre for Integrative Biology at the University of Trento in Italy.

A devastating disease

Duchenne muscular dystrophy is a devastating disease that affects about 1 in every 3,600 boys born in the United States. Patients usually experience severe, progressive muscle weakness that confines them to a wheelchair in early adolescence and eventually leads to paralysis. It's caused by mutations in the dystrophin gene, which encodes the dystrophin protein. The dystrophin protein serves to connect muscle fibres to the surrounding external matrix. This connection stabilizes the fibres, enhancing their strength and preventing injury. Sufferers are nearly always boys because the dystrophin gene is located on the X chromosome. (Girls would need to inherit two faulty copies, which is unlikely because male carriers often die in early adulthood.)

Under normal conditions, muscle stem cells respond to muscle damage by dividing into cells, one of which becomes new muscle, while the other remains a stem cell. However, in the mice missing the dystrophin gene, the muscle stem cells slowly assume a different fate. They begin to resemble fibroblasts instead of muscle-making machines.

To conduct the research, Biressi and Rando used a strain of laboratory mice in which the muscle stem cells were engineered to glow with a fluorescent light when treated with a drug called tamoxifen. They then bred the mice with another strain in which the dystrophin gene is mutated, and followed the fate of the cells over time.

The researchers found that the expression of myogenic genes, which are associated with the regeneration of muscle in response to injury, was nearly completely lacking in many of the muscle stem cells in the mice after just 11 months, while the expression of fibrotic genes had increased compared with that of control animals. The cells from the dystrophic animals were also oddly located: Rather than being nestled next to the muscle fibres, they had begun to move away into the spaces between tissues.

The role of a signalling pathway

Rando and Biressi knew that a similar, but much less pronounced, accumulation of connective tissue in muscle fibres occurs during normal aging. That process is governed by signalling proteins, which include the Wnt and TGF-beta protein families. Wnt plays a critical role in embryonic development and cancer; TGF-beta controls cell division and specialization. They wondered whether blocking the Wnt/TGF-beta pathway in the dystrophic mice would inhibit fibrosis in the animals' muscles.

The researchers turned to a drug called losartan, which is used to treat high blood pressure. Losartan inhibits the expression of the genes for TGF-beta types 1 and 2. The researchers thought it would probably interrupt the signalling pathway that leads the muscle stem cells astray.

Treating the mice with losartan, they found, did in fact prevent the muscle stem cells from expressing fibrosis-associated genes and partially maintained their ability to form new muscle.

"This scar tissue, or fibrosis, leaves the muscle less elastic and impairs muscle function," Rando said.

"So we'd like to understand why it happens, and how to prevent it. It's also important to limit fibrosis to increase the likelihood of success with other possible therapies, such as cell therapy or gene therapy."

Next steps

Because TGF-beta type 1 plays many roles throughout the body, the researchers are now working to find ways to specifically inhibit TGF-beta type 2, which is involved in the transition of the muscle stem cells. They're also interested in learning how to translate the research to other diseases.

"Fibrosis seems to occur in a vicious cycle," Rando said.

"As the muscle stem cells become less able to regenerate new muscle, the tissue is less able to repair itself after damage. This leads to fibrosis, which then further impairs muscle formation. Understanding the biological basis of fibrosis could have a profound effect on many other diseases."

Source: Stanford University Medical Center

Contact: Krista Conger

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Cell Biologists Discover On-off Switch for Key Stem Cell Gene

Discovery may propel advances in regenerative medicine

Sunday, 14 December 2014

Consider the relationship between an air traffic controller and a pilot. The pilot gets the passengers to their destination, but the air traffic controller decides when the plane can take off and when it must wait. The same relationship plays out at the cellular level in animals, including humans. A region of an animal's genome - the controller - directs when a particular gene - the pilot - can perform its prescribed function.

These are images of mouse embryonic stem cells

which grow in a round colony of cells (A) and

express Sox2 (B), shown in red. Sox2 control

region-deleted cells have lost the typical

appearance of embryonic stem cells (C) and do

not express Sox2 (D). The DNA is shown in blue

in B and D. Credit: Jennifer Mitchell/University

of Toronto. 

A new study by cell and systems biologists at the University of Toronto (U of T) investigating stem cells in mice shows, for the first time, an instance of such a relationship between the Sox2 gene which is critical for early development, and a region elsewhere on the genome that effectively regulates its activity. The discovery could mean a significant advance in the emerging field of human regenerative medicine, as the Sox2 gene is essential for maintaining embryonic stem cells that can develop into any cell type of a mature animal.

"We studied how the Sox2 gene is turned on in mice, and found the region of the genome that is needed to turn the gene on in embryonic stem cells," said Professor Jennifer Mitchell of U of T's Department of Cell and Systems Biology, lead investigator of a study published in the December 15 issue of Genes & Development.

"Like the gene itself, this region of the genome enables these stem cells to maintain their ability to become any type of cell, a property known as pluripotency. We named the region of the genome that we discovered the Sox2 control region, or SCR," said Mitchell.

Since the sequencing of the human genome was completed in 2003, researchers have been trying to figure out which parts of the genome made some people more likely to develop certain diseases. They have found that the answers are more often in the regions of the human genome that turn genes on and off.

"If we want to understand how genes are turned on and off, we need to know where the sequences that perform this function are located in the genome," said Mitchell.

"The parts of the human genome linked to complex diseases such as heart disease, cancer and neurological disorders can often be far away from the genes they regulate, so it can be difficult to figure out which gene is being affected and ultimately causing the disease."

It was previously thought that regions much closer to the Sox2 gene were the ones that turned it on in embryonic stem cells. Mitchell and her colleagues eliminated this possibility when they deleted these nearby regions in the genome of mice and found there was no impact on the gene's ability to be turned on in embryonic stem cells.

"We then focused on the region we've since named the SCR as my work had shown that it can contact the Sox2 gene from its location 100,000 base pairs away," said study lead author Harry Zhou, a former graduate student in Mitchell's lab, now a student at U of T's Faculty of Medicine.

"To contact the gene, the DNA makes a loop that brings the SCR close to the gene itself only in embryonic stem cells. Once we had a good idea that this region could be acting on the Sox2 gene, we removed the region from the genome and monitored the effect on Sox2."

The researchers discovered that this region is required to both turn Sox2 on, and for the embryonic stem cells to maintain their characteristic appearance and ability to differentiate into all the cell types of the adult organism.

"Just as deletion of the Sox2 gene causes the very early embryo to die, it is likely that an abnormality in the regulatory region would also cause early embryonic death before any of the organs have even formed," said Mitchell.

"It is possible that the formation of the loop needed to make contact with the Sox2 gene is an important final step in the process by which researchers practicing regenerative medicine can generate pluripotent cells from adult cells."

"Though the degree to which human embryonic stem cells possess this feature is not entirely clear, by understanding how another complex organism's genome works we ultimately learn more about how our own genome works," said Zhou.

Source: University of Toronto

Contact: Sean Bettam

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Pluripotent Cells Created by Nuclear Transfer Can Prompt Immune Reaction

Pluripotent Cells Created by Nuclear Transfer Can Prompt Immune Reaction

Friday, 21 November 2014

Mouse cells and tissues created through nuclear transfer can be rejected by the body because of a previously unknown immune response to the cell's mitochondria, according to a study in mice by researchers at the Stanford University School of Medicine and colleagues in Germany, England and at MIT.

The findings reveal a likely, but surmountable, hurdle if such therapies are ever used in humans, the researchers said.

Stem cell therapies hold vast potential for repairing organs and treating disease. The greatest hope rests on the potential of pluripotent stem cells, which can become nearly any kind of cell in the body. One method of creating pluripotent stem cells is called somatic cell nuclear transfer, and involves taking the nucleus of an adult cell and injecting it into an egg cell from which the nucleus has been removed.

The promise of the SCNT method is that the nucleus of a patient's skin cell, for example, could be used to create pluripotent cells that might be able to repair a part of that patient's body.

"One attraction of SCNT has always been that the genetic identity of the new pluripotent cell would be the same as the patient's, since the transplanted nucleus carries the patient's DNA," said cardiothoracic surgeon Sonja Schrepfer, MD, PhD, a co-senior author of the study, which will be published online Nov. 20 in Cell Stem Cell.

"The hope has been that this would eliminate the problem of the patient's immune system attacking the pluripotent cells as foreign tissue, which is a problem with most organs and tissues when they are transplanted from one patient to another," added Schrepfer, who is a visiting scholar at Stanford's Cardiovascular Institute. She is also a Heisenberg Professor of the German Research Foundation at the University Heart Center in Hamburg, and at the German Center for Cardiovascular Research.

Possibility of rejection

A dozen years ago, when Irving Weissman, MD, professor of pathology and of developmental biology at Stanford, headed a National Academy of Sciences panel on stem cells, he raised the possibility that the immune system of a patient who received SCNT-derived cells might still react against the cells' mitochondria, which act as the energy factories for the cell and have their own DNA. This reaction could occur because cells created through SCNT contain mitochondria from the egg donor and not from the patient, and therefore could still look like foreign tissue to the recipient's immune system, said Weissman, the other co-senior author of the paper. Weissman is the Virginia and D.K. Ludwig Professor for Clinical Investigation in Cancer Research and the director of the Stanford Institute for Stem Cell Biology and Regenerative Medicine.

That hypothesis was never tested until Schrepfer and her colleagues took up the challenge.

"There was a thought that because the mitochondria were on the inside of the cell, they would not be exposed to the host's immune system," Schrepfer said.

"We found out that this was not the case."

Schrepfer, who heads the Transplant and Stem Cell Immunobiology Laboratory in Hamburg, used cells that were created by transferring the nuclei of adult mouse cells into enucleated eggs cells from genetically different mice. When transplanted back into the nucleus donor strain, the cells were rejected although there were only two single nucleotide substitutions in the mitochondrial DNA of these SCNT-derived cells compared to that of the nucleus donor.

"We were surprised to find that just two small differences in the mitochondrial DNA were enough to cause an immune reaction," she said.

"We didn't do the experiment in humans, but we assume the same sort of reaction could occur," Schrepfer added.

Until recently, researchers were able to perform SCNT in many species, but not in humans. When scientists at the Oregon Health and Science University announced success in performing SCNT with human cells last year, it reignited interest in eventually using the technique for human therapies. Although many stem cell researchers are focused on a different method of creating pluripotent stem cells, called induced pluripotent stem cells, there may be some applications for which SCNT-derived pluripotent cells are better suited.

Handling the reaction

The immunological reactions reported in the new paper will be a consideration if clinicians ever use SCNT-derived stem cells in human therapy, but such reactions should not prevent their use, Weissman said.

"This research informs us of the margin of safety that would be required if, in the distant future, we need to use SCNT to create pluripotent cells to treat someone," he said.

"In that case, clinicians would likely be able to handle the immunological reaction using the immunosuppression methods that are currently available."

In the future, scientists might also lessen the immune reaction by using eggs from someone who is genetically similar to the recipient, such as a mother or sister, Schrepfer added.

Source: Stanford University Medical Center

Contact: Christopher Vaughan 

Reference:

SCNT-Derived ESCs with Mismatched Mitochondria Trigger an Immune Response in Allogeneic Hosts

Tobias Deuse, Dong Wang, Mandy Stubbendorff, Ryo Itagaki, Antje Grabosch, Laura C. Greaves, Malik Alawi, Anne Grünewald, Xiaomeng Hu, Xiaoqin Hua, Joachim Velden, Hermann Reichenspurner, Robert C. Robbins, Rudolf Jaenisch, Irving L. Weissman, Sonja Schrepfer

Cell Stem Cell, November 20, 2014, DOI: http://dx.doi.org/10.1016/j.stem.2014.11.003

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Cardiac Stem Cell Therapy may Heal Heart Damage Caused by Duchenne Muscular Dystrophy

Late-breaking basic science research presented at American Heart Association Scientific Sessions shows stem cell treatment restores heart function damaged by muscular disease

Tuesday, 18 November 2014

Researchers at the Cedars-Sinai Heart Institute have found that injections of cardiac stem cells might help reverse heart damage caused by Duchenne muscular dystrophy, potentially resulting in a longer life expectancy for patients with the chronic muscle-wasting disease.

The study results were presented today at a Breaking Basic Science presentation during the American Heart Association Scientific Sessions in Chicago. After laboratory mice with Duchenne muscular dystrophy were infused with cardiac stem cells, the mice showed steady, marked improvement in heart function and increased exercise capacity.

Duchenne muscular dystrophy, which affects 1 in 3,600 boys, is a neuromuscular disease caused by a shortage of a protein called dystrophin, leading to progressive muscle weakness. Most Duchenne patients lose their ability to walk by age 12. Average life expectancy is about 25. The cause of death often is heart failure because the dystrophin deficiency leads to cardiomyopathy, a weakness of the heart muscle that makes the heart less able to pump blood and maintain a regular rhythm.

"Most research into treatments for Duchenne muscular dystrophy patients has focused on the skeletal muscle aspects of the disease, but more often than not, the cause of death has been the heart failure that affects Duchenne patients," said Eduardo Marbán, MD, PhD, director of the Cedars-Sinai Heart Institute and study leader.

"Currently, there is no treatment to address the loss of functional heart muscle in these patients."

During the past five years, the Cedars-Sinai Heart Institute has become a world leader in studying the use of stem cells to regenerate heart muscle in patients who have had heart attacks. In 2009, Marbán and his team completed the world's first procedure in which a patient's own heart tissue was used to grow specialized heart stem cells. The specialized cells were then injected back into the patient's heart in an effort to repair and regrow healthy muscle in a heart that had been injured by a heart attack. Results, published in The Lancet in 2012, showed that one year after receiving the experimental stem cell treatment, heart attack patients demonstrated a significant reduction in the size of the scar left on the heart muscle.

Earlier this year, Heart Institute researchers began a new study, called ALLSTAR, in which heart attack patients are being infused with allogeneic stem cells, which are derived from donor-quality hearts.

Recently, the Heart Institute opened the nation's first Regenerative Medicine Clinic, designed to match heart and vascular disease patients with appropriate stem cell clinical trials being conducted at Cedars-Sinai and other institutions.

"We are committed to thoroughly investigating whether stem cells could repair heart damage caused by Duchenne muscular dystrophy," Marbán said.

In the study, 78 lab mice were injected with cardiac stem cells. Over the next three months, the lab mice demonstrated improved pumping ability and exercise capacity in addition to a reduction in heart inflammation. The researchers also discovered that the stem cells work indirectly, by secreting tiny fat droplets called exosomes. The exosomes, when purified and administered alone, reproduce the key benefits of the cardiac stem cells.

Marbán said the procedure could be ready for testing in human clinical studies as soon as next year. The process to grow cardiac-derived stem cells was developed by Marbán when he was on the faculty of Johns Hopkins University. Johns Hopkins has filed for a patent on that intellectual property and has licensed it to Capricor, a company in which Cedars-Sinai and Marbán have a financial interest. Capricor is providing funds for the ALLSTAR clinical trial at Cedars-Sinai.

The Cedars-Sinai Heart Institute has been at the forefront of developing investigational stem cell treatments for heart attack patients.

Source: Cedars-Sinai Medical Center

Contact: Sally Stewart

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