Most Complete Human Brain Model to Date Is a ‘Brain Changer’

Once licensed, model likely to accelerate study of Alzheimer’s, autism, more

Wednesday, 19 August 2015

Scientists at The Ohio State University have developed a nearly complete human brain in a dish that equals the brain maturity of a 5-week-old foetus.

The brain organoid, engineered from adult human skin cells, is the most complete human brain model yet developed, said Rene Anand, professor of biological chemistry and pharmacology at Ohio State.

The lab-grown brain, about the size of a pencil eraser, has an identifiable structure and contains 99 percent of the genes present in the human foetal brain. Such a system will enable ethical and more rapid and accurate testing of experimental drugs before the clinical trial stage and advance studies of genetic and environmental causes of central nervous system disorders.

“It not only looks like the developing brain, its diverse cell types express nearly all genes like a brain,” Anand said.

“We’ve struggled for a long time trying to solve complex brain disease problems that cause tremendous pain and suffering. The power of this brain model bodes very well for human health because it gives us better and more relevant options to test and develop therapeutics other than rodents.”

Anand reported on his lab-grown brain Tuesday (Aug. 18) at the 2015 Military Health System Research Symposium in Ft. Lauderdale, Florida.

This image of the lab-grown brain is labelled to

show identifiable structures: the cerebral

hemisphere, the optic stalk and the cephalic

flexure, a bend in the mid-brain region, all

characteristic of the human foetal brain. Credit:

courtesy of The Ohio State University.

Anand, who studies the association between nicotinic receptors and central nervous system disorders, was inspired to pursue a model of human neural biology after encountering disappointing results in a rodent study of an experimental autism drug. Taking a chance with a shoestring budget compared to other researchers doing similar projects, he added stem-cell engineering to his research program. Four years later, he had built himself a replica of the human brain.

The main thing missing in this model is a vascular system. What is there – a spinal cord, all major regions of the brain, multiple cell types, signalling circuitry and even a retina – has the potential to dramatically accelerate the pace of neuroscience research, said Anand, also a professor of neuroscience.

“In central nervous system diseases, this will enable studies of either underlying genetic susceptibility or purely environmental influences, or a combination,” he said.

“Genomic science infers there are up to 600 genes that give rise to autism, but we are stuck there. Mathematical correlations and statistical methods are insufficient to in themselves identify causation. You need an experimental system – you need a human brain.”

Converting adult skin cells into pluripotent cells – immature stem cells that can be programmed to become any tissue in the body – is a rapidly developing area of science that earned the researcher who discovered the technique, Shinya Yamanaka, a Nobel Prize in 2012.

“Once a cell is in that pluripotent state, it can become any organ – if you know what to do to support it to become that organ,” Anand said.

“The brain has been the holy grail because of its enormous complexity compared to any other organ. Other groups are attempting to do this as well.”

Anand’s method is proprietary and he has filed an invention disclosure with the university.

He said he used techniques to differentiate pluripotent stem cells into cells that are designed to become neural tissue, components of the central nervous system or other brain regions.

“We provide the best possible environment and conditions that replicate what’s going on in utero to support the brain,” he said of the work he completed with colleague Susan McKay, a research associate in biological chemistry and pharmacology.

High-resolution imaging of the organoid identifies functioning neurons and their signal-carrying extensions – axons and dendrites – as well as astrocytes, oligodendrocytes and microglia. The model also activates markers for cells that have the classic excitatory and inhibitory functions in the brain, and that enable chemical signals to travel throughout the structure.

It takes about 15 weeks to build a model system developed to match the 5-week-old foetal human brain. Anand and McKay have let the model continue to grow to the 12-week point, observing expected maturation changes along the way.

“If we let it go to 16 or 20 weeks, that might complete it, filling in that 1 percent of missing genes. We don’t know yet,” he said.

He and McKay have already used the platform to launch their own projects, creating brain organoid models of Alzheimer’s and Parkinson’s diseases and autism in a dish. They hope that with further development and the addition of a pumping blood supply, the model could be used for stroke therapy studies. For military purposes, the system offers a new platform for the study of Gulf War illness, traumatic brain injury and post-traumatic stress disorder.

Anand hopes his brain model could be incorporated into the Microphysiological Systems program, a platform the Defense Advanced Research Projects Agency is developing by using engineered human tissue to mimic human physiological systems.

Support for the work came from the Marci and Bill Ingram Research Fund for Autism Spectrum Disorders and the Ohio State University Wexner Medical Center Research Fund.

Anand and McKay are co-founders of a Columbus-based start-up company, NeurXstem, to commercialize the brain organoid platform, and have applied for funding from the federal Small Business Technology Transfer program to accelerate its drug discovery applications.

Source: Ohio State University

Contact: Rene Anand

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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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Scientists Finds Key to Making Neurons from Stem Cells

Pnky, a noncoding RNA found in brain stem cells, may have a broad range of clinical applications

Friday, 20 March 2015

A research team at UC San Francisco has discovered an RNA molecule called Pnky that can be manipulated to increase the production of neurons from neural stem cells.

The research, led by neurosurgeon Daniel A. Lim, MD, PhD, and published on March 19, 2015 in Cell Stem Cell, has possible applications in regenerative medicine, including treatments of such disorders as Alzheimer's disease, Parkinson's disease and traumatic brain injury, and in cancer treatment.

In this cluster of neurons, the greens cells have

been infected with a virus to reduce levels of the

RNA molecule called Pnky, resulting in

increased production of neurons. Someday this

finding could be important for regenerative

medicine and cancer treatment.

Pnky is one of a number of newly discovered long noncoding RNAs (lncRNAs), which are stretches of 200 or more nucleotides in the human genome that do not code for proteins, yet seem to have a biological function.

The name, pronounced "Pinky," was inspired by the popular American cartoon series Pinky and the Brain.

"Pnky is encoded near a gene called 'Brain,' so it sort of suggested itself to the students in my laboratory," said Lim. Pnky also appears only to be found in the brain, he noted.

Co-first authors Alex Ramos, PhD, and Rebecca Andersen, who are students in Lim's laboratory, first studied Pnky in neural stem cells found in mouse brains, and also identified the molecule in neural stem cells of the developing human brain. They found that when Pnky was removed from stem cells in a process called knockdown, neuron production increased three to four times.

"It is remarkable that when you take Pnky away, the stem cells produce many more neurons," said Lim, an assistant professor of neurological surgery and director of restorative surgery at UCSF.

"These findings suggest that Pnky, and perhaps lncRNAs in general, could eventually have important applications in regenerative medicine and cancer treatment."

Lim observed that Pnky has an intriguing possible connection with brain tumours.

Using an analytical technique called mass spectrometry, Ramos found that Pnky binds the protein PTBP1, which is also found in brain tumours and is known to be a driver of brain tumour growth. In neural stem cells, Pnky and PTBP1 appear to function together to suppress the production of neurons.

"Take away one or the other and the stem cells differentiate, making more neurons," said Lim.

"It is also possible that Pnky can regulate brain tumour growth, which means we may have identified a target for the treatment of brain tumours."

Lim said that the larger significance of the research is that it adds to a growing store of knowledge about lncRNAs, previously unknown sections of the genome that some biologists have referred to as the "dark matter" of the human genome.

"Recently, over fifty thousand human lncRNAs have been discovered. Thus, there may be more human lncRNAs than there are genes that code for proteins," said Lim.

"It is possible that not all lncRNAs have important biological functions, but we are making a start toward learning which ones do, and if so, how they function. It's a new world of experimental biology, and the students in my lab are right there on the frontier."

Lim had particular praise for Ramos, an MD-PhD student in the UCSF Medical Scientist Training Program, and Andersen, who has a fellowship from the prestigious National Science Foundation (NSF) Graduate Research Fellowship Program.

"They have been a great collaborative team and an inspiration to others in my lab," said Lim.

"I think they represent the pioneering, investigative spirit of the UCSF student body."

Source: UC San Francisco

Contact: Laura Kurtzman

Reference:

The Long Noncoding RNA Pnky Regulates Neuronal Differentiation of Embryonic and Postnatal Neural Stem Cells

Alexander D. Ramos, Rebecca E. Andersen, Siyuan John Liu, Tomasz Jan Nowakowski, Sung Jun Hong, Caitlyn C. Gertz, Ryan D. Salinas, Hosniya Zarabi, Arnold R. Kriegstein, Daniel A. Lim

Cell Stem Cell, March 19, 2015, DOI: http://dx.doi.org/10.1016/j.stem.2015.02.007

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Do Viruses Make Us Smarter?

Do Viruses Make Us Smarter?

Monday, 12 January 2015

A new study from Lund University in Sweden indicates that inherited viruses that are millions of years old play an important role in building up the complex networks that characterise the human brain.

Researchers have long been aware that endogenous retroviruses constitute around five per cent of our DNA. For many years, they were considered junk DNA of no real use, a side-effect of our evolutionary journey.

In the current study, Johan Jakobsson and his colleagues show that retroviruses seem to play a central role in the basic functions of the brain, more specifically in the regulation of which genes are to be expressed, and when. The findings indicate that, over the course of evolution, the viruses took an increasingly firm hold on the steering wheel in our cellular machinery. The reason the viruses are activated specifically in the brain is probably due to the fact that tumours cannot form in nerve cells, unlike in other tissues.

"We have been able to observe that these viruses are activated specifically in the brain cells and have an important regulatory role. We believe that the role of retroviruses can contribute to explaining why brain cells in particular are so dynamic and multifaceted in their function. It may also be the case that the viruses' more or less complex functions in various species can help us to understand why we are so different", says Johan Jakobsson, head of the research team for molecular neurogenetics at Lund University.

The article, based on studies of neural stem cells, shows that these cells use a particular molecular mechanism to control the activation processes of the retroviruses. The findings provide us with a complex insight into the innermost workings of the most basal functions of the nerve cells. At the same time, the results open up potential for new research paths concerning brain diseases linked to genetic factors.

"I believe that this can lead to new, exciting studies on the diseases of the brain. Currently, when we look for genetic factors linked to various diseases, we usually look for the genes we are familiar with, which make up a mere two per cent of the genome. Now we are opening up the possibility of looking at a much larger part of the genetic material which was previously considered unimportant. The image of the brain becomes more complex, but the area in which to search for errors linked to diseases with a genetic component, such as neurodegenerative diseases, psychiatric illness and brain tumours, also increases".

Source: Lund University

Contact: Johan Jakobsson

Reference:

TRIM28 represses transcription of endogenous retroviruses in neural progenitor cells

Liana Fasching, Adamandia Kapopoulou, Rohit Sachdeva, Rebecca Petri, Marie E. Jönsson, Christian Männe, Priscilla Turelli, Patric Jern, Florence Cammas, Didier Trono, Johan Jakobsson

Cell Reports, 2015 Jan 6;10(1):20-8, doi: 10.1016/j.celrep.2014.12.004

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Human Skin Cells Reprogrammed Directly into Brain Cells

Human Skin Cells Reprogrammed Directly into Brain Cells

Wednesday, 22 October 2014

Scientists have described a way to convert human skin cells directly into a specific type of brain cell affected by Huntington's disease, an ultimately fatal neurodegenerative disorder. Unlike other techniques that turn one cell type into another, this new process does not pass through a stem cell phase, avoiding the production of multiple cell types, the study's authors report.

Scientists have described a way to convert

human skin cells directly into a specific type of

brain cell affected by Huntington's disease, an

ultimately fatal neurodegenerative disorder.

Unlike other techniques that turn one cell type

into another, this new process does not pass

through a stem cell phase, avoiding the

production of multiple cell types, the study's

authors report. The researchers, at Washington

University School of Medicine in St. Louis,

demonstrated that these converted cells survived

at least six months after injection into the brains

of mice and behaved similarly to native cells in

the brain. Human skin cells (top) can be

converted into medium spiny neurons (bottom)

with exposure to the right combination of

microRNAs and transcription factors, according

to work by Andrew Yoo and his research team. 

Credit: Yoo lab.

The researchers, at Washington University School of Medicine in St. Louis, demonstrated that these converted cells survived at least six months after injection into the brains of mice and behaved similarly to native cells in the brain.

"Not only did these transplanted cells survive in the mouse brain, they showed functional properties similar to those of native cells," said senior author Andrew S. Yoo, PhD, assistant professor of developmental biology.

"These cells are known to extend projections into certain brain regions. And we found the human transplanted cells also connected to these distant targets in the mouse brain. That's a landmark point about this paper."

The work appears Oct. 22 in the journal Neuron.

The investigators produced a specific type of brain cell called medium spiny neurons, which are important for controlling movement. They are the primary cells affected in Huntington's disease, an inherited genetic disorder that causes involuntary muscle movements and cognitive decline usually beginning in middle-adulthood. Patients with the condition live about 20 years following the onset of symptoms, which steadily worsen over time.

The research involved adult human skin cells, rather than more commonly studied mouse cells or even human cells at an earlier stage of development. In regard to potential future therapies, the ability to convert adult human cells presents the possibility of using a patient's own skin cells, which are easily accessible and won't be rejected by the immune system.

Scientists have described a way to convert

human skin cells directly into a specific type of

brain cell affected by Huntington's disease, an

ultimately fatal neurodegenerative disorder.

Unlike other techniques that turn one cell type

into another, this new process does not pass

through a stem cell phase, avoiding the

production of multiple cell types, report

researchers at Washington University School of

Medicine in St. Louis. The investigators,

including Andrew Yoo, PhD, (from left) Michelle

Richner and Matheus Victor, demonstrated that

these converted cells survived at least six months

after injection into the brains of mice and

behaved similarly to native cells in the brain. 

Credit: Daniel Abernathy.

To reprogram these cells, Yoo and his colleagues put the skin cells in an environment that closely mimics the environment of brain cells. They knew from past work that exposure to two small molecules of RNA, a close chemical cousin of DNA, could turn skin cells into a mix of different types of neurons.

In a skin cell, the DNA instructions for how to be a brain cell, or any other type of cell, are neatly packed away, unused. In past research published in Nature, Yoo and his colleagues showed that exposure to two microRNAs called miR-9 and miR-124 altered the machinery that governs packaging of DNA. Though the investigators still are unravelling the details of this complex process, these microRNAs appear to be opening up the tightly packaged sections of DNA important for brain cells, allowing expression of genes governing development and function of neurons.

Knowing exposure to these microRNAs alone could change skin cells into a mix of neurons, the researchers then started to fine tune the chemical signals, exposing the cells to additional molecules called transcription factors that they knew were present in the part of the brain where medium spiny neurons are common.

"We think that the microRNAs are really doing the heavy lifting," said co-first author Matheus B. Victor, a graduate student in neuroscience.

"They are priming the skin cells to become neurons. The transcription factors we add then guide the skin cells to become a specific subtype, in this case medium spiny neurons. We think we could produce different types of neurons by switching out different transcription factors."

Yoo also explained that the microRNAs, but not the transcription factors, are important components for the general reprogramming of human skin cells directly to neurons. His team, including co-first author Michelle C. Richner, senior research technician, showed that when the skin cells were exposed to the transcription factors alone, without the microRNAs, the conversion into neurons wasn't successful.

The researchers performed extensive tests to demonstrate that these newly converted brain cells did indeed look and behave like native medium spiny neurons. The converted cells expressed genes specific to native human medium spiny neurons and did not express genes for other types of neurons. When transplanted into the mouse brain, the converted cells showed morphological and functional properties similar to native neurons.

To study the cellular properties associated with the disease, the investigators now are taking skin cells from patients with Huntington's disease and reprogramming them into medium spiny neurons using the approach described in the new paper. They also plan to inject healthy reprogrammed human cells into mice with a model of Huntington's disease to see if this has any effect on the symptoms.

Source: Washington University School of Medicine

Contact: Julia Evangelou Strait

Reference:

Generation of human striatal neurons by microRNA-dependent direct conversion of fibroblasts

Victor MB, Richner M, Hermanstyne TO, Ransdell JL, Sobieski C, Deng PY, Klyachko VA, Nerbonne JM, Yoo AS

Neuron. Oct. 22, 2014, Volume 84, Issue 2, p311–323

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Vesicles Influence the Function of Nerve Cells

Neurons react to the transmission activity of exosomes on three fundamental levels

Tuesday, 07 October 2014

The JGU researchers were able to show that

exosomes are absorbed by the nerve cells and

thus help protect these against stress. Credit:

Institute of Molecular Cell Biology. 

Tiny vesicles containing protective substances which they transmit to nerve cells apparently play an important role in the functioning of neurons. As cell biologists at Johannes Gutenberg University Mainz (JGU) have discovered, nerve cells can enlist the aid of mini-vesicles of neighbouring glial cells to defend themselves against stress and other potentially detrimental factors. These vesicles, called exosomes, appear to stimulate the neurons on various levels: they influence electrical stimulus conduction, biochemical signal transfer, and gene regulation. Exosomes are thus multifunctional signal emitters that can have a significant effect in the brain.

Neurons (blue) which have absorbed exosomes

(green) have increased levels of the enzyme

catalase (red), which helps protect them against

peroxides. Credit: Institute of Molecular Cell

Biology, JGU.

The researchers in Mainz already observed in a previous study that oligodendrocytes release exosomes on exposure to neuronal stimuli. These exosomes are absorbed by the neurons and improve neuronal stress tolerance. Oligodendrocytes are a type of glial cell and they form an insulating myelin sheath around the axons of neurons. The exosomes transport protective proteins such as heat shock proteins, glycolytic enzymes, and enzymes that reduce oxidative stress from one cell type to another, but also transmit genetic information in the form of ribonucleic acids.

"As we have now discovered in cell cultures, exosomes seem to have a whole range of functions," explained Dr. Eva-Maria Krämer-Albers. By means of their transmission activity, the small bubbles that are the vesicles not only promote electrical activity in the nerve cells, but also influence them on the biochemical and gene regulatory level.

Cultivated neurons on a multielectrode array

chip: the electrodes register the electrical

impulses of the neurons. Credit: Institute of

Physiology, Mainz University Medical Center.

"The extent of activities of the exosomes is impressive," added Krämer-Albers. The researchers hope that the understanding of these processes will contribute to the development of new strategies for the treatment of neuronal diseases. Their next aim is to uncover how vesicles actually function in the brains of living organisms.

Source: Johannes Gutenberg Universitaet Mainz

Contact: Dr. Eva-Maria Krämer-Albers

Reference:

Multifaceted effects of oligodendroglial exosomes on neurons: impact on neuronal firing rate, signal transduction and gene regulation

Dominik Fröhlich, Wen Ping Kuo, Carsten Frühbeis, Jyh-Jang Sun, Christoph M. Zehendner, Heiko J. Luhmann, Sheena Pinto, Joern Toedling, Jacqueline Trotter and Eva-Maria Krämer-Albers

Philosophical Transactions of the Royal Society B, 18 August 2014 DOI: 10.1098/rstb.2013.0510

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Stem Cells Use 'First Aid Kits' to Repair Damage

Stem Cells Use 'First Aid Kits' to Repair Damage

Thursday, 18 September 2014

Stem cells hold great promise as a means of repairing cells in conditions such as multiple sclerosis, stroke or injuries of the spinal cord because they have the ability to develop into almost any cell type. Now, new research shows that stem cell therapy can also work through a mechanism other than cell replacement.

Confocal super resolution imaging of the rapid

(2h) up-take of CD63-RFP EVs packed via

target cell fEGFP (green) plasma membrane in

vitro. Credit: Design and artwork by CongJian

Zhao.

In a study published today in Molecular Cell, a team of researchers led by the University of Cambridge has shown that stem cells "communicate" with cells by transferring molecules via fluid filled bags called vesicles, helping other cells to modify the damaging immune response around them.

Although scientists have speculated that stem cells might act rather like drugs – in sensing signals, moving to specific areas of the body and executing complex reactions – this is the first time that a molecular mechanism for this process has been demonstrated. By understanding this process better, researchers can identify ways of maximising the efficiency of stem-cell-based therapies.

Dr Stefano Pluchino from the Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, who led the study, said:

"These tiny vesicles in stem cells contain molecules like proteins and nucleic acids that stimulate the target cells and help them to survive – they act like mini "first aid kits".

"Essentially, they mirror how the stem cells respond to an inflammatory environment like that seen during complex neural injuries and diseases, and they pass this ability on to the target cells. We think this helps injured brain cells to repair themselves."

Mice with damage to brain cells – such as the damage seen in multiple sclerosis – show a remarkable level of recovery when neural stem/precursor cells (NPCs) are injected into their circulatory system. It has been suggested that this happens because the NPCs discharge molecules that regulate the immune system and that ultimately reduce tissue damage or enhance tissue repair.

The team of researchers from the UK, Australia, Italy, China and Spain has now shown that NPCs make vesicles when they are in the vicinity of an immune response, and especially in response to a small protein, or cytokine, called Interferon-gamma which is released by immune cells. This protein has the ability to regulate both the immune responses and intrinsic brain repair programmes and can alter the function of cells by regulating the activity of scores of genes.

Their results show that a highly specific pathway of gene activation is triggered in NPCs by IFN-gamma, and that this protein also binds to a receptor on the surface of vesicles. When the vesicles are released by the NPCs, they adhere and are taken up by target cells. Not only does the target cell receive proteins and nucleic acids that can help them self-repair, but it also receives the IFN-gamma on the surface of the vesicles, which activates genes within the target cells.

The researchers, who were funded by the European Research Council and the Italian MS Society, used electron microscopy and super resolution imaging to visualise the vesicles moving between the NPCs and target cells in vitro.

"Our work highlights a surprising novel role for stem-cell-derived vesicles in propagating responses to the environment," added Pluchino.

"It represents a significant advance in understanding the many levels of interaction between stem cells and the immune system, and a new molecular mechanism to explain how stem-cell therapy works."

Source: University of Cambridge

Contact: Louise Walsh

Reference:

Extracellular Vesicles from Neural Stem Cells Transfer IFN-γ via Ifngr1 to Activate Stat1 Signaling in Target Cells

Chiara Cossetti, Nunzio Iraci, Tim R. Mercer, Tommaso Leonardi, Emanuele Alpi, Denise Drago, Clara Alfaro-Cervello, Harpreet K. Saini, Matthew P. Davis, Julia Schaeffer, Beatriz Vega, Matilde Stefanini, CongJian Zhao, Werner Muller, Jose Manuel Garcia-Verdugo, Suresh Mathivanan, Angela Bachi, Anton J. Enright, John S. Mattick, Stefano Pluchino

Molecular Cell, September 18, 2014, DOI: http://dx.doi.org/10.1016/j.molcel.2014.08.020

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In Directing Stem Cells, Study Shows Context Matters

In Directing Stem Cells, Study Shows Context Matters

Tuesday, 09 September 2014

Figuring out how blank slate stem cells decide which kind of cell they want to be when they grow up — a muscle cell, a bone cell, a neuron — has been no small task for science.

When blank slate stem cells are exposed to a soft

as opposed to a hard surface on which to grow,

they begin to transform themselves into neurons,

the large, complex cells of the central nervous

system. Absent any soluble factors to direct cell

differentiation, surface matters, according to

new research from the lab of University of

Wisconsin-Madison chemist and biochemist

Laura Kiessling. Credit: Kiessling Lab/UW-

Madison.

Human pluripotent stem cells, the undifferentiated cells that have the potential to become any of the 220 types of cells in the body, are influenced in the lab dish by the cocktail of chemical factors and proteins upon which they are grown and nurtured. Depending on the combination of factors used in a culture, the cells can be coaxed to become specific types of cells.

Now, in a new study published today, Sept. 8, in the Proceedings of the National Academy of Sciences, a team of researchers from the University of Wisconsin-Madison has added a new wrinkle to the cell differentiation equation, showing that the stiffness of the surfaces on which stem cells are grown can exert a profound influence on cell fate.

"To derive lineages, people use soluble growth factors to get the cells to differentiate," explains Laura Kiessling, a UW-Madison professor of chemistry and biochemistry and stem cell expert.

Past work, she notes, hinted that the qualities of the surface on which a cell lands could exert an influence on cell fate, but the idea was never fully explored in the context of human pluripotent stem cell differentiation.

In the lab, stem cells are grown in plastic dishes coated with a gel that contains as many as 1,800 different proteins. Different factors can be introduced to obtain certain types of cells. But even in the absence of introduced chemical or protein cues, the cells are always working to differentiate — but in seemingly random, undirected ways.

The Wisconsin group, directed by Kiessling and led by chemistry graduate student Samira Musah, decided to test the idea that the hardness of a surface can make a difference. After all, in a living body, cells seek different niches with different qualities and transform themselves accordingly.

"Many cell types grow on a surface. If a cell is near bone, the environment has certain features," says Kiessling, whose group — collaborating with UW-Madison colleagues Sean Palecek, Qiang Chang and William Murphy — has been working to produce precise, chemically defined surfaces on which to grow stem cells.

"A cell will react differently if it lands near soft tissue like the brain."

To fully explore the idea that surface matters to a stem cell, Kiessling's group created gels of different hardness to mimic muscle, liver and brain tissues. The study sought to test whether the surface alone, absent any added soluble factors to influence cell fate decisions, can have an effect on differentiation.

Results, according to Kiessling, showed that a soft, brain tissue-like surface, independent of any soluble factors, was catalyst enough to direct cells to become neurons, the large elaborate cells that make up the central nervous system. Stiffer surfaces favoured the stem cell state.

"We didn't change anything but switch from a hard surface to a soft surface," Kiessling says.

"They all started looking like neurons. It was stunning to me that the surface had such a profound effect."

In the case of the soft, brain-like surface, the Wisconsin researchers believe that the mechanical properties of a surface are influencing a protein called YAP. YAP can be found in the cytoplasm but also the nucleus of a cell, and when it is in the nucleus, YAP regulates gene expression. According to the study results, YAP is excluded from the nucleus on the soft gels, and its depletion there helps drive the stem cells onto a brain cell developmental pathway.

The finding, that the simple mechanical properties of a surface can play a big role in helping stem cells decide what to be, promises to help scientists better define the experimental conditions to direct stem cell fate. It may also ultimately inform the methods that will be used for producing large quantities of cells for therapeutic use and other applications such as the high-throughput screening of chemicals for brain toxicity or therapeutics.

Source: University of Wisconsin-Madison

Contact: Laura Kiessling

Reference:

Substratum-induced differentiation of human pluripotent stem cells reveals the coactivator YAP is a potent regulator of neuronal specification

Samira Musah, Paul J. Wrighton, Yefim Zaltsman, Xiaofen Zhong, Stefan Zorn, Matthew B. Parlato, Cheston Hsiao, Sean P. Palecek, Qiang Chang, William L. Murphy and Laura L. Kiessling

PNAS 2014, September 8, doi: 10.1073/pnas.1415330111

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