Neuroscience

Scientists at the Gladstone Institutes have defined for the first time a key underlying process implicated in multiple sclerosis (MS)—a disease that causes progressive and irreversible damage to nerve cells in the brain and spinal cord. This discovery offers new hope for the millions who suffer from this debilitating disease for which there is no cure.

Researchers in the laboratory of Gladstone Investigator Katerina Akassoglou, PhD, have identified in animal models precisely how a protein that seeps from the blood into the brain sets off a response that, over time, causes the nerve cell damage that is a key indicator of MS. These findings, which are reported in the latest issue of Nature Communications, lay the groundwork for much-needed therapies to treat this disease.

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Professor José Miguel Soria, a member of the Institute of Biomedical Sciences, Universidad CEU Cardenal Herrera, has co-directed with Professor Manuel Monleón of the Universitat Politècnica de València a study on the compatibility of polymeric biomaterials in the brain and its effectiveness to favour neuroregeneration in areas with some kind of damage or brain injury.  

The research carried out has shown that these types of implants, made of a biocompatible synthetic material, are colonized within two months by neural progenitor cells and irrigated by new blood vessels. This allows the generation, within these structures, of new neurons and glia, capable of repairing injured brain tissue caused by trauma, stroke or neurodegenerative disease, among other causes.

The synthetic structures used in this study are made with a porous and biocompatible polymeric material called acrylate copolymer. In the first phase of the project, the structures have been studied in vitro by implanting them into neural tissue, and subsequently also in vivo, when implanted in two areas of the adult rat brain: the cerebral cortex and the subventricular zone, the most important source of generation of adult neural stem cells.

The study has confirmed the high biocompatibility of polymeric materials, such as acrylate copolymer, with brain tissue and opens new possibilities of the effectiveness of the implementation of these structures in the brain, seeking optimum location for developing regenerative strategies of the central nervous system.

Furthermore, the results are particularly relevant when one considers that in the adult brain neuroregeneration capacity is more limited than in younger individuals and that the main impediment for this is the lack of revascularization of damaged tissue, something that the biomaterial studied has shown to favour.

New research suggests that the molecular mechanism leading to schizophrenia may be different in patients who fail to respond to anti-psychotic medication compared to patients who do respond.

The research, from King’s College London’s Institute of Psychiatry may help explain why up to one third of patients with schizophrenia do not respond to traditional anti-psychotic medication.

Schizophrenia is known to be associated with an overactive dopamine system, meaning that the brain processes abnormally high levels of dopamine. Traditional dopamine-blocking anti-psychotic medication attempts to normalise this process. However, approximately one third of patients with schizophrenia do not respond to this treatment, and until now, no study has examined whether dopamine abnormality is present in patients resistant to antipsychotic treatment.

The study was led by Dr Arsime Demjaha, Dr Oliver Howes, Professor Shitij Kapur, Professor Sir Robin Murray and Professor Philip McGuire from King’s Institute of Psychiatry and published in the American Journal of Psychiatry. 

Dr Arsime Demjaha and co-authors, say: ‘Despite considerable scientific and therapeutic progress over the last 50 years, we still do not know why some patients with schizophrenia respond to treatment whilst others do not. Treatment resistance in such a disabling condition is one of the greatest clinical and therapeutic challenges to psychiatry, significantly affecting patients, their families and society in general.’

The authors conclude: ‘Our findings suggest that there may be a different molecular mechanism leading to schizophrenia in patients who do not respond to anti-psychotic medication. Identifying the precise molecular pathway particularly in these patients is of utmost importance and will help inform the development of much-needed novel treatments.’

Researchers used PET scan imaging to investigate dopamine synthesis capacity in 12 patients with schizophrenia who did not respond to treatment, 12 who did, and 12 healthy controls. They found that schizophrenia patients whose illness was resistant to antipsychotic treatment have relatively normal levels of dopamine synthesis capacity which would explain why the dopamine blocking anti-psychotic medication was not effective in this group. 

However, the authors add that the findings need to be replicated in larger samples before the research can affect clinical practice. They add that future research will need to focus on long-term prospective studies of patients who have never taken anti-psychotics to determine whether presynaptic dopamine synthesis capacity was normal in patients in the treatment-resistant group at the onset of their illness, and predates antipsychotic exposure.

Autism spectrum disorders (ASD) are neurodevelopmental disorders typically characterized by difficulties in social interactions and delayed or abnormal language development. Although ASD reportedly affects 1 in 88 people in the United States, to date there have been no distinctive biomarkers to diagnose the disease. In a special themed issue of Disease Markers, investigators report on the current understanding of ASD genetics and the possibilities of translating genetic research toward biomarker development in ASD.

"Although some individuals with ASD are highly functional, many are severely impaired and require permanent care. The significant level of impairment combined with the fact that no specific therapy is yet available for ASD, make ASD a devastating illness for patients and families, and a heavy financial burden for the healthcare system," says guest editor, Irina Voineagu, MD, PhD, RIKEN Omics Science Center, Yokohama, Japan. "The most effective intervention for ASD has proven to be early behavioral therapy. Thus the identification of biological markers for ASD, allowing very early detection, even before the onset of symptoms, would be of tremendous value."

Five articles comprise this comprehensive issue, providing an overview of ASD genetic models, an exploration of several key emerging concepts in understanding ASD’s molecular basis, and discussion of current biomarker development, focusing on genomic data.

Following an introduction by Voineagu, Yuri Bozzi and colleagues review the phenotype characteristics of currently available mouse models of ASD. Carmen Panaitof then discusses the role of the songbird as an experimental model system for investigating the genetic basis of human language and its ASD-related impairments. Michael Bowers and Genevieve Konopka further explore language deficits and provide new evidence for the role of the FOXP gene to regulate language. Alka Saxena, Dave Tang, and Piero Carninci focus on the functional roles of the gene MECP2, which is mutated in most cases of Rett syndrome, one of the ASDs.

A review rounding out the issue is “Subphenotype-Dependent Disease Markers for Diagnosis and Personalized Treatment of Autism Spectrum Disorders,” by Valerie W. Hu, PhD, The George Washington University, School of Medicine and Health Sciences, Washington, DC, PhD, which discusses current progress toward identifying ASD biomarkers based on genome-wide data.

"Without genetic or molecular markers for screening, individuals with ASD are typically not diagnosed before the age of 2, with milder cases diagnosed much later," writes Dr. Hu. "Because early diagnosis is tantamount to early behavioral intervention, which has been shown to improve individual outcomes, an objective biomarker test that can diagnose at-risk children perinatally is a medical imperative."

Hu demonstrates the possibility and importance of developing ASD subtypes to help identify relevant disease markers, which can ultimately aid in developing specific targeted therapies.

Voineagu concludes, “It is exciting times for genetic research and although the phenotypic and genetic heterogeneity of ASD often seem to be a daunting conundrum, well-defined diagnostic criteria, larger cohort sizes for genetic studies and integrative approaches of genomic and epigenomic data already delineate a promising avenue for elucidating the mechanisms of ASD.”

Scientists at NYU Langone Medical Center have identified two genes involved in establishing the neuronal circuits required for breathing. They report their findings in a study published in the December issue of Nature Neuroscience. The discovery, featured on the journal’s cover, could help advance treatments for spinal cord injuries and neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), which gradually kill neurons that control the movement of muscles needed to breathe, move, and eat.

The study identifies a molecular code that distinguishes a group of muscle-controlling nerve cells collectively known as the phrenic motor column (PMC). These cells lie about halfway up the back of the neck, just above the fourth cervical vertebra, and are “probably the most important motor neurons in your body,” says Jeremy Dasen, PhD, assistant professor of physiology and neuroscience and a member of the Howard Hughes Medical Institute, who led the three-year study with Polyxeni Philippidou, PhD, a postdoctoral fellow.

Harming the part of the spinal cord where the PMC resides can instantly shut down breathing. But relatively little is known about what distinguishes PMC neurons from neighboring neurons, and how PMC neurons develop and wire themselves to the diaphragm in the fetus.

The PMC cells relay a constant flow of electrochemical signals down their bundled axons and onto the diaphragm muscles, allowing the lungs to expand and relax in the natural rhythm of breathing. “We now have a set of molecular markers that distinguish those cells from other populations of motor neurons, so that we can study them in detail and look for ways to selectively enhance their survival,” Dr. Dasen says. Degeneration of PMC neurons is the primary cause of death in patients with ALS and spinal cord injuries.

To find out what distinguishes PMC neurons from their spinal neighbors in mice, Dr. Philippidou injected a retrograde fluorescent tracer into the phrenic nerve, which wires the PMC to the diaphragm, and then looked for the spinal neurons that lit up as the tracer worked its way back to the PMC. He used transgenic mice that express green fluorescent protein (GFP) in motor neurons and their axons in order to see the phrenic nerve. After noting the characteristic gene expression pattern of these PMC neurons, Dr. Philippidou began to determine their specific roles. Ultimately, a complicated strain of transgenic mice, based partly on mice supplied by collaborator Lucie Jeannotte, PhD, at the University of Laval in Quebec, revealed two genes, Hoxa5 and Hoxc5, as the prime controllers of proper PMC development. Hox genes (39 are expressed in humans) are well known as master gene regulators of animal development.

When Hoxa5 and Hoxc5 are silenced in embryonic motor neurons in mice, the scientists reported, the PMC fails to form its usual, tightly columnar organization and doesn’t connect correctly to the diaphragm, leaving a newborn animal unable to breathe. “Even if you delete these genes late in fetal development, the PMC neuron population drops and the phrenic nerve doesn’t form enough branches on diaphragm muscles,” Dr. Dasen says.

Dr. Dasen plans to use the findings to help understand the wider circuitry of breathing—including rhythm-generating neurons in the brain stem, which are in turn responsive to carbon dioxide levels, stress, and other environmental factors. “Now that we know something about PMC cells, we can work our way through the broader circuit, to try to figure out how all those connections are established,” he says.

"Once we understand how the respiratory network is wired we can begin to develop novel treatment options for breathing disorders such as sleep apneas," adds Dr. Philippidou.

In late October Dr. Dasen lost many of his transgenic mice when Hurricane Sandy flooded the basement of the Smilow building at NYU Langone Medical Center. But just before the hurricane hit, he sent an important group of these mice back to Dr. Jeannotte in Quebec, “so we didn’t lose everything,” he says.

Borrowing from microfabrication techniques used in the semiconductor industry, MIT and Harvard Medical School (HMS) engineers have developed a simple and inexpensive way to create three-dimensional brain tissues in a lab dish.

The new technique yields tissue constructs that closely mimic the cellular composition of those in the living brain, allowing scientists to study how neurons form connections and to predict how cells from individual patients might respond to different drugs. The work also paves the way for developing bioengineered implants to replace damaged tissue for organ systems, according to the researchers.

"We think that by bringing this kind of control and manipulation into neurobiology, we can investigate many different directions," says Utkan Demirci, an assistant professor in the Harvard-MIT Division of Health Sciences and Technology (HST).

Demirci and Ed Boyden, associate professor of biological engineering and brain and cognitive sciences at MIT’s Media Lab and McGovern Institute, are senior authors of a paper describing the new technique, which appears in the Nov. 27 online edition of the journal Advanced Materials. The paper’s lead author is Umut Gurkan, a postdoc at HST, Harvard Medical School and Brigham and Women’s Hospital.

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Reduced production of myelin, a type of protective nerve fiber that is lost in diseases like multiple sclerosis, may also play a role in the development of mental illness, according to researchers at the Graduate School of Biomedical Sciences at Mount Sinai School of Medicine. The study is published in the journal Nature Neuroscience.

Myelin is an insulating material that wraps around the axon, the threadlike part of a nerve cell through which the cell sends impulses to other nerve cells. New myelin is produced by nerve cells called oligodendrocytes both during development and in adulthood to repair damage in the brain of people with diseases such as multiple sclerosis (MS).

A new study led by Patrizia Casaccia, MD, PhD, Professor of Neuroscience, Genetics and Genomics; and Neurology at Mount Sinai, determined that depriving mice of social contact reduced myelin production, demonstrating that the formation of new oligodendrocytes is affected by environmental changes. This research provides further support to earlier evidence of abnormal myelin in a wide range of psychiatric disorders, including autism, anxiety, schizophrenia and depression.

“We knew that a lack of social interaction early in life impacted myelination in young animals but were unsure if these changes would persist in adulthood,” said Dr. Casaccia, who is also Chief of the Center of Excellence for Myelin Repair at the Friedman Brain Institute at Mount Sinai School of Medicine. “Social isolation of adult mice causes behavioral and structural changes in neurons, but this is the first study to show that it causes myelin dysfunction as well.”

Dr. Casaccia’s team isolated adult mice to determine whether new myelin formation was compromised. After eight weeks, they found that the isolated mice showed signs of social withdrawal. Subsequent brain tissue analyses indicated that the socially isolated mice had lower-than-normal levels of myelin-forming oligodendrocytes in the prefrontal cortex, but not in other areas of the brain. The prefrontal cortex controls complex emotional and cognitive behavior.

The researchers also found changes in chromatin, the packing material for DNA. As a result, the DNA from the new oligodendrocytes was unavailable for gene expression.

After observing the reduction in myelin production in socially-isolated mice, Dr. Casaccia’s team then re-introduced these mice into a social group. After four weeks, the social withdrawal symptoms and the gene expression changes were reversed.

“Our study demonstrates that oligodendrocytes generate new myelin as a way to respond to environmental stimuli, and that myelin production is significantly reduced in social isolation,” said Dr. Casaccia. “Abnormalities occur in people with psychiatric conditions characterized by social withdrawal. Other disorders characterized by myelin loss, such as MS, often are associated with depression. Our research emphasizes the importance of maintaining a socially stimulating environment in these instances.”

At Mount Sinai, Dr. Casaccia’s laboratory is studying oligodendrocyte formation to identify therapeutic targets for myelin repair. They are screening newly-developed pharmacological compounds in brain cells from rodents and humans for their ability to form new myelin.

Scientists have revealed the minutely detailed pain map of the hand that is contained within our brains, shedding light on how the brain makes us feel discomfort and potentially increasing our understanding of the processes involved in chronic pain. 

The map, uncovered by scientists at UCL, is the first to reveal how finely-tuned the brain is to pain. Published in the Journal of Neuroscience, the study uses fMRI techniques in conjunction with laser stimuli to the fingers to plot the exact response to pain across areas of the brain.

“The results reveal that pain can be finely mapped in the brain,” said lead author Dr Flavia Mancini (UCL Institute of Cognitive Neuroscience). “While many studies have examined the brain response to pain before, our study is the first to map pain responses for the individual digits of the human hand.”

Using an fMRI brain imaging technique originally created to map the visual field, the researchers were able to distinguish the brain’s responses to painful laser heat stimuli on each finger in seven healthy participants, and to study their organisation in the brain. 

This enabled the team to produce a fine-grained map showing how pain in the right hand results in certain parts of the brain being activated in the primary somatosensory cortex, an area in the left hemisphere of the brain which is involved in processing bodily information.

When comparing this pain map to ones generated by non-painful touch to the right hand, the researchers found that the two were very similar, with each map aligning with one another in each of the seven volunteers tested.

“The cells in the skin that respond to pain and the cells that respond to touch have very different structures and distributions, so we were surprised to find that the maps of pain and of touch were so similar in the brain,” said Dr Mancini. “The striking alignment of pain and touch maps suggests powerful interactions between the two systems.”

The pain maps could be used to provide markers for the location of pain in the human brain, enabling clinicians to see how patients’ brains reorganise following chronic pain. 

“We know that the organisation of other sensory maps in the brain is altered in patients with chronic pain,” said Professor Patrick Haggard (UCL Institute of Cognitive Neuroscience). “Our method could next be used to track the reorganisation of brain maps that occurs in chronic pain, providing new insights into how the brain makes us feel pain. Therefore, measuring the map for pain itself is highly important.”

A small molecule known to regulate white blood cells has a surprising second role in protecting brain cells from the deleterious effects of stroke, Johns Hopkins researchers report. The molecule, microRNA-223, affects how cells respond to the temporary loss of blood supply brought on by stroke — and thus the cells’ likelihood of suffering permanent damage.

“We set out to find a small molecule with very specific effects in the brain, one that could be the target of a future stroke treatment,” says Valina Dawson, Ph.D., a professor in the Johns Hopkins University School of Medicine’s Institute for Cell Engineering. “What we found is this molecule involved in immune response, which also acts in complex ways on the brain. This opens up a suite of interesting questions about what microRNA-223 is doing and how, but it also presents a challenge to any therapeutic application.” A report on the discovery is published in the Nov. 13 issue of the Proceedings of the National Academy of Sciences.

RNA is best known as a go-between that shuttles genetic information from DNA and then helps produce proteins based on that information. But, Dawson explains, a decade ago researchers unearthed a completely different class of RNA: small, nimble fragments that regulate protein production. In the case of microRNA, one member of this class, that control comes from the ability to bind to RNA messenger molecules carrying genetic information, and thus prevent them from delivering their messages. “Compared with most ways of shutting genes off, this one is very quick,” Dawson notes.

Reasoning that this quick action, along with other properties, could make microRNAs a good target for therapy development, Dawson and her team searched for microRNAs that regulate brain cells’ response to oxygen deprivation.

To do that, they looked for proteins that increased in number in cells subjected to stress, and then examined how production of these proteins was regulated. For many of them, microRNA-223 played a role, Dawson says.

In most cases, the proteins regulated by microRNA-223 turned out to be involved in detecting and responding to glutamate, a common chemical signal brain cells use to communicate with each other. A stroke or other injury can lead to a dangerous excess of glutamate in the brain, as can a range of diseases, including autism and Alzheimer’s.

Because microRNA-223 is involved in regulating so many different proteins, and because it affects glutamate receptors, which themselves are involved in many different processes, the molecule’s reach turned out to be much broader than expected, says Maged M. Harraz, Ph.D., a research associate at Hopkins who led the study. “Before this experiment, we didn’t appreciate that a single microRNA could regulate so many proteins,” he explains.

This finding suggests that microRNA-223 is unlikely to become a therapeutic target in the near future unless researchers figure out how to avoid unwanted side effects, Dawson says.

As part of the European study TRANSEURO, five patients with Parkinson’s disease will undergo brain cell transplants at Skåne University Hospital in Lund, Sweden, in early 2013. These are the first operations of their kind in Europe for over 10 years.

The TRANSEURO study, which in Sweden is led by Lund University, is now taking a critical approach to the viability of cell therapy as a future treatment for Parkinson’s disease. Can we replace cells that die as a result of our most common neurological diseases? What are the therapies of the future for neurodegenerative diseases like Parkinson’s and Alzheimer’s?

Under the leadership of Professor of Neurology Olle Lindvall, brain researchers in Lund had already developed a method of transplanting nerve cells in the 1980s. In 1987, brain surgeon Stig Rehncrona operated on the very first patient. That study was historic and marked the first repair of the human nervous system. The news was cabled out to all the world’s media and the Swedish researchers soon graced the front page of the New York Times.

"Since the advances made in the 1980s and 1990s, the research field has encountered many obstacles. In the early 2000s, two American studies produced negative results, which meant that cell transplants for Parkinson’s disease came to a dead end," says Professor Anders Björklund, who in the 1980s was responsible for the ground-breaking discoveries in the laboratory.

Despite the unsatisfactory results presented in the American trials, cell therapy has still been seen to have effects that are entirely unique in the history of research on Parkinson’s. A third of the transplant patients have seen significant benefits of cell therapy over a very long period without medication, in some cases up to 20 years.

"For a disease with a very demanding medication regime, and for which the effects of the standard medication begin to diminish after 5 years, cell therapy represents a hope of a different life for many Parkinson’s sufferers", says Professor Håkan Widner, who is in charge of patient recruitment in Lund.

"The results of TRANSEURO will play an important role in the immediate future of cell therapy as a viable treatment. We have scrutinized the failed American studies in an attempt to optimise the technique, improve patient selection and conduct more personalised follow-up. We are hopeful that the results will be different this time", says Professor Widner.

A “sonar vision” system that enables people who are blind from birth to perceive the shape of a face, a house or even words and letters, is being developed by a team at the Hebrew University of Jerusalem. Using this device, the researchers have shown that, in people that are blind from birth, the areas of the cerebral cortex normally devoted to reading become activated in response to stimulation. The results of this study, conducted in conjunction with researchers at the ICM Brain and Bone Marrow Institute Research Center (Inserm/UPMC/AP-HP) and NeuroSpin (CEA-Inserm), were published in Neuron on November 8.

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A short burst of moderate exercise enhances the consolidation of memories in both healthy older adults and those with mild cognitive impairment, scientists with UC Irvine’s Center for the Neurobiology of Learning & Memory have discovered.

Most research has focused on the benefits of a long-term exercise program on overall health and cognitive function with age. But the UCI work is the first to examine the immediate effects of a brief bout of exercise on memory.

In their study, post-doctoral researcher Sabrina Segal and neurobiologists Carl Cotman and Lawrence Cahill had people 50 to 85 years old with and without memory deficits view pleasant images – such as photos of nature and animals – and then exercise on a stationary bicycle for six minutes at 70 percent of their maximum capacity immediately afterward.

One hour later, the participants were given a surprise recall test on the previously viewed images. Results showed a striking enhancement of memory by exercise in both the healthy and cognitively impaired adults, compared with subjects who did not ride the bike.

“We found that a single, short instance of moderately intense exercise particularly improved memory in individuals with memory deficits,” Segal said. “Because of its implications and the need to better understand the mechanism by which exercise may enhance memory, we’re following up this study with an investigation of potential underlying biological factors.”

She believes the improved memory may be related to the exercise-induced release of norepinephrine, a chemical messenger in the brain known to play a strong role in memory modulation. This hypothesis is based on previous work demonstrating that increasing norepinephrine through pharmacological manipulation sharpens memory and that blocking norepinephrine impairs memory.

In the more recent research, Segal and her colleagues discovered that levels of salivary alpha amylase, a biomarker that reflects norepinephrine activity in the brain, significantly increased in participants after exercise. This correlation was especially strong in people with memory impairment.

“The current findings offer a natural and relatively safe alternative to pharmacological interventions for memory enhancement in healthy older individuals as well as those who suffer from cognitive deficits,” Segal noted. “With a growing population of the aged, the need for improvement of quality of life and prevention of mental decline is more important than ever before.”

Study results appear in the November issue (Volume 32, Number 4) of the Journal of Alzheimer’s Disease.