Tag Archive for: oligodendrocyte

girl with down syndrome

Study finds delayed oligodendrocyte progenitor maturation in Down syndrome

girl with down syndrome

People with Down syndrome (DS) can have moderate to severe intellectual disability, which is thought to be associated with changes in early brain development.

People with Down syndrome (DS) can have moderate to severe intellectual disability, which is thought to be associated with changes in early brain development. Children’s National Hospital experts discovered delayed maturation in oligodendrocyte progenitors in DS. Oligodendrocytes produce the white matter which insulates neural pathways and ensures speedy electrical communication in the brain. The researchers identified these delays by measuring gene expression at key steps in cell development, according to a new study published in Frontiers in Cellular Neuroscience.

The findings further suggest that brain and spinal cord oligodendrocytes differ in their developmental trajectories and that “brain-like” oligodendrocyte progenitors were most different from control cells, indicating that oligodendrocytes in the brains of people with DS are not equally affected by the trisomy 21.

“This is one of the critical steps towards identifying the key stages and molecular players in the DS white matter deficits,” said Tarik Haydar, Ph.D., director of the Center for Neuroscience Research. “With this knowledge, and with further work in this direction, we envision future therapies that may improve nerve cell communication in the brains of people with Down syndrome.”

The hold-up in the field

The mechanisms that lead to the reduction of white matter in the brains of people with DS are unknown. To better understand early neural precursors, they used isogenic pluripotent stem cell lines derived from two individuals with Down syndrome to study the brain development and spinal cord oligodendrocytes.

“I was excited that we discovered another example of how important it is not to generalize when studying DS brain development,” said Haydar. “This is one of several papers, from our group and others, that demonstrate how important it is to be very specific about the brain area and the developmental stage when investigating the causes of DS brain dysfunction.”

What’s next

Dysmaturation of oligodendrocyte cells are a relatively new discovery by the Haydar Lab, one of the preeminent labs in DS research. These results isolate specific steps that are affected in human cells with trisomy 21. They are using these results to develop a drug screening platform that may prevent altered generation of oligodendrocytes in the future.

You can read the full study “Sonic Hedgehog Pathway Modulation Normalizes Expression of Olig2 in Rostrally Patterned NPCs With Trisomy 21” in Frontiers in Cellular Neuroscience.

microglia cells damage the myelin sheath of neuron axons

Katrina Adams, Ph.D., awarded fellowship to help restore functions in MS patients

microglia cells damage the myelin sheath of neuron axons

Multiple sclerosis is a demyelinating disease in which the insulating covers of nerve cells are damaged. Microglia cells (orange) attack the oligodendrocytes that form the insulating myelin sheath around neuron axons, leading to the destruction of the myelin sheath and to the loss of nerve function.

For her contributions to Multiple Sclerosis (MS) research, Katrina Adams, Ph.D., postdoctoral researcher at Children’s National Hospital, received the career transition fellowship from The National Multiple Sclerosis Society. The $600,000 fellowship will support a two-year period of advanced postdoctoral training in MS research and the first three years of research support in a new faculty appointment.

MS symptoms, including vision loss, pain, fatigue and reduced motor coordination, result from the demyelination of neuronal axons that transport critical information across the brain and spinal cord. Demyelination is the loss of myelin protein, which is normally produced by oligodendrocyte cells.

In the healthy brain, oligodendrocytes repair demyelinated areas by replacing damaged or lost myelin in a process called remyelination. Recent evidence has shown that oligodendrocytes display differences in their molecular and functional properties. One source of new oligodendrocytes in the adult brain is neural stem cells, which have been shown to generate oligodendrocytes that contribute to remyelination.

“The goal of this project is to determine whether neural stem cell-derived oligodendrocytes are distinct from other oligodendrocytes, both in the healthy brain and in MS,” said Adams. “I aim to understand the molecular mechanisms that regulate generation of oligodendrocytes from neural stem cells, with the goal of identifying signals that could be targeted in MS patients to promote remyelination.”

Remyelination is very limited in MS patients and current therapies for MS have very little impact on promoting remyelination.

This study will take advantage of the state-of-the-art facilities for single-cell analysis, transcriptomics, microscopy, and animal research in Children’s Research Institute at Children’s National. Adams also added that her postdoctoral mentor, Vittorio Gallo, Ph.D., interim chief academic officer and interim director of the Children’s National Research Institute, and principal investigator for the DC-IDDRC, has renowned expertise in glial biology, animal models of MS and white matter injury.

“This research will be the first to directly compare neural stem cell-derived oligodendrocytes with other resident oligodendrocytes in MS brain samples,” said Adams. “The results of this study will provide critical insight into the role that neural stem cells play in repair of MS demyelinated lesions.”

Adams received her doctorate in molecular biology from the University of California, Los Angeles where she used pluripotent stem cells to study motor neuron development. She currently investigates signaling pathways that regulate neural stem and progenitor cell maintenance and differentiation in the developing postnatal and adult brain, with a focus on the Endothelin-1 pathway. She is interested in understanding how stem and progenitor cells respond to disease or injury, such as in Multiple Sclerosis, with the hope of identifying new therapeutic targets.

Vittorio Gallo

Special issue of “Neurochemical Research” honors Vittorio Gallo, Ph.D.

Vittorio Gallo

Investigators from around the world penned manuscripts that were assembled in a special issue of “Neurochemical Research” that honors Vittorio Gallo, Ph.D., for his leadership in the field of neural development and regeneration.

At a pivotal moment early in his career, Vittorio Gallo, Ph.D., was accepted to work with Professor Giulio Levi at the Institute for Cell Biology in Rome, a position that leveraged courses Gallo had taken in neurobiology and neurochemistry, and allowed him to work in the top research institute in Italy directed by the Nobel laureate, Professor Rita Levi-Montalcini.

For four years as a student and later as Levi’s collaborator, Gallo focused on amino acid neurotransmitters in the brain and mechanisms of glutamate and GABA release from nerve terminals. Those early years cemented a research focus on glutamate neurotransmission that would lead to a number of pivotal publications and research collaborations that have spanned decades.

Now, investigators from around the world who have worked most closely with Gallo penned tributes in the form of manuscripts that were assembled in a special issue of “Neurochemical Research” that honors Gallo “for his contributions to our understanding of glutamatergic and GABAergic transmission during brain development and to his leadership in the field of neural development and regeneration,” writes guest editor Arne Schousboe, of the University of Copenhagen in Denmark.

Dr. Gallo as a grad student

Vittorio Gallo, Ph.D. as a 21-year-old mustachioed graduate student.

“In spite of news headlines about competition in research and many of the negative things we hear about the research world, this shows that research is also able to create a community around us,” says Gallo, chief research officer at Children’s National Hospital and scientific director for the Children’s National Research Institute.

As just one example, he first met Schousboe 44 years ago when Gallo was a 21-year-old mustachioed graduate student.

“Research can really create a sense of community that we carry on from the time we are in training, nurture as we meet our colleagues at periodic conferences, and continue up to the present. Creating community is bi-directional: influencing people and being influenced by people. People were willing to contribute these 17 articles because they value me,” Gallo says. “This is a lot of work for the editor and the people who prepared papers for this special issue.”

In addition to Gallo publishing more than 140 peer-reviewed papers, 30 review articles and book chapters, Schousboe notes a number of Gallo’s accomplishments, including:

  • He helped to develop the cerebellar granule cell cultures as a model system to study how electrical activity and voltage-dependent calcium channels modulate granule neuron development and glutamate release.
  • He developed a biochemical/neuropharmacological assay to monitor the effects of GABA receptor modulators on the activity of GABA chloride channels in living neurons.
  • He and Maria Usowicz used patch-clamp recording and single channel analysis to demonstrate for the first time that astrocytes express glutamate-activated channels that display functional properties similar to neuronal counterparts.
  • He characterized one of the spliced isoforms of the AMPA receptor subunit gene Gria4 and demonstrated that this isoform was highly expressed in the cerebellum.
  • He and his Children’s National colleagues demonstrated that glutamate and GABA regulate oligodendrocyte progenitor cell proliferation and differentiation.
Purkinje cells

Purkinje cells are large neurons located in the cerebellum that are elaborately branched like interlocking tree limbs and represent the only source of output for the entire cerebellar cortex.

Even the image selected to grace the special issue’s cover continues the theme of continuity and leaving behind a legacy. That image of Purkinje cells was created by a young scientist who works in Gallo’s lab, Aaron Sathyanesan, Ph.D. Gallo began his career working on the cerebellum – a region of the brain important for motor control – and now studies with a team of scientists and clinician-scientists Purkinje cells’ role in locomotor adaptive behavior and how that is disrupted after neonatal brain injury.

“These cells are the main players in cerebellar circuitry,” Gallo says. “It’s a meaningful image because goes back to my roots as a graduate student and is also an image that someone produced in my lab early in his career. It’s very meaningful to me that Aaron agreed to provide this image for the cover of the special issue.”

effects of cardiopulmonary bypass surgery on the white matter of piglets.

The effects of cardiopulmonary bypass on white matter development

 cardiopulmonary bypass

Nobuyuki Ishibashi, M.D., and a team of researchers looked the effects of cardiopulmonary bypass surgery on the white matter of an animal model.

Mortality rates for infants born with congenital heart disease (CHD) have dramatically decreased over the past two decades, with more and more children reaching adulthood. However, many survivors are at risk for neurodevelopmental abnormalities  associated with cardiopulmonary bypass surgery (CPB), including long-term injuries to the brain’s white matter and neural connectivity impairments that can lead to neurological dysfunction.

“Clinical studies have found a connection between abnormal neurological outcomes and surgery, but we don’t know what’s happening at the cellular level,” explains Nobuyuki Ishibashi, M.D., Director of the Cardiac Surgery Research Laboratory at Children’s National. To help shed light on this matter, Ishibashi and a team of researchers looked at the effects of CPB on the white matter of an animal model.

The research team randomly assigned models to receive one of three CPB-induced insults: a sham surgery (control group); full-flow bypass for 60 minutes; and 25°C circulatory arrest for 60 minutes. The team then used fractional anisotropy — a technique that measures the directionality of axon mylenation — to determine white matter organization in the models’ brains. They also used immunohistology techniques to assess the integrity of white matter oligodendrocytes, astrocytes and microglia.

The results, published in the Journal of the American Heart Association, show that white matter experiences region-specific vulnerability to insults associated with CPB, with fibers within the frontal cortex appearing the most susceptible. The team also found that fractional anisotropy changes after CPB were insult dependent and that regions most resilient to CPB-induced fractional anisotropy reduction were those that maintained mature oligodendrocytes.

From these findings, Ishibashi and his co-authors conclude that reducing alterations of oligodendrocyte development in the frontal cortex can be both a metric and a goal to improve neurodevelopmental impairment in the congenital heart disease population. “Because we are seeing cellular damage in these regions, we can target them for future therapies,” explains Ishibashi.

The study also demonstrates the dynamic relationship between fractional anisotropy and cellular events after pediatric cardiac surgery, and indicates that the technique is a clinically relevant biomarker in white matter injury after cardiac surgery.

newborn

Sirtuin could repair common neonatal brain injury

A sirtuin might help repair a common neonatal brain injury

A team of researchers  investigated the molecular mechanisms behind oligodendrocyte progenitor cell proliferation in neonatal hypoxia.

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What’s known

Hypoxia, or a lack of oxygen, is a major cause of diffuse white matter injury (DWMI). This condition leads to permanent developmental disabilities in prematurely born infants. The long-term abnormalities of the brain’s white matter that characterize DWMI are caused by the loss of a specific type of cells known as oligodendrocytes, which support nerve cells and produce myelin, a lipid and protein sheath that electrically insulates nerve cells. Oligodendrocytes are produced by a population of immature cells known as oligodendrocyte progenitor cells (OPCs). Previous research has shown that hypoxia can trigger OPCs to proliferate and presumably produce new oligodendrocytes. The molecular pathways that hypoxia triggers to make new OPCs remain unclear.

What’s new

A team of researchers led by Vittorio Gallo, Ph.D., director of the Center for Neuroscience Research and the Intellectual and Developmental Disabilities Research Center at Children’s National Health System, investigated the molecular mechanisms behind what prompts OPCs to proliferate in a preclinical model of neonatal hypoxia. The researchers found that a molecule known as Sirt1 acts as a major regulator of OPC proliferation and regeneration. Sirt1 is a sirtuin, a class of molecules that has attracted interest over the past several years for its role in stem cells, aging and inflammation. Hypoxia appears to induce Sirt1 formation. When the researchers prevented brain tissues in petri dishes from making Sirt1 or removed this molecule in preclinical models, these actions prevented OPC proliferation. What’s more, preventing Sirt1 production also inhibited OPCs from making oligodendrocytes. These findings suggest that Sirt1 is essential for replacing oligodendrocytes to repair DWMI after hypoxia. Additionally, finding ways to enhance Sirt1 activity eventually could provide a novel way to help infants recover after hypoxia and prevent DWMI.

Questions for future research

Q: How can Sirt1 activity be enhanced in preclinical models and humans?
Q: Can deficits triggered by diffuse white matter injury be prevented or reversed with Sirt1?
Q: Which other treatments might be useful for diffuse white matter injury?

Source: Sirt1 regulates glial progenitor proliferation and regeneration in white matter after neonatal brain injury.” Jablonska, M., M. Gierdalski, L. Chew, T. Hawley, M. Catron, A. Lichauco, J. Cabrera-Luque, T. Yuen, D. Rowitch and V. Gallo. Published by Nature Communications on Dec. 19, 2016.