Written by Dr Hannah K Shorrock Edited by Dr. Maria do Carmo Costa
Neurofilament light chain predicts cerebellar atrophy across multiple types of spinocerebellar ataxia
A team led by Alexandra Durr at the Paris Brain Institute identified that the levels of neurofilament light chain (NfL) protein are higher in SCA1, 2, 3, and 7 patients than in the general population. The researchers also discovered that the level of NfL can predict the clinical progression of ataxia and changes in cerebellar volume. Because of this, identifying patients’ NfL levels may help to provide clearer information on disease progression in an individualized manner. This in turn means that NfL levels may be useful in refining inclusion criteria for clinical trials.
The group enrolled a total of 62 SCA patients with 17 SCA1 patients, 13 SCA2 patients, 19 SCA3 patients, and 13 SCA7 patients alongside 19 age-matched healthy individuals (“controls”) as part of the BIOSCA study. Using an ultrasensitive single-molecule array, the group measured NfL levels from blood plasma that was collected after the participants fasted.
The researchers found that NfL levels were significantly higher in SCA expansion carriers than in control participants at the start of the study (baseline). In control individuals, the group identified a correlation between age and NfL level that was not present among SCA patients. This indicates that disease stage rather than age plays a larger role in NfL levels in SCAs.
Looking at each disease individually, the group was able to generate an optimal disease cut-off score to differentiate between control and SCA patients. By comparing the different SCAs, the research group found that SCA3 had the highest NfL levels among the SCAs studied. As such, SCA3 had the most accurate disease cut-off level with 100% sensitivity and 95% specificity of defining SCA3 patients based on NfL levels.
Riluzole, often sold under the trade name Rilutek, is a medication used for the treatment of amyotrophic lateral sclerosis (ALS). ALS is a fatal neurodegenerative disease that mainly affects neurons controlling muscle movements. The drug was approved by the FDA (1995), Health Canada (1997), and the European Commission (1996). It helps slow down disease progression and may extend patient survival. The medication is available in tablet and liquid form, generally well-tolerated. There are sometimes mild side effects, which may include loss of appetite, nausea, and abdominal pain.
How does it work?
Exactly how Riluzole slows disease progression remains unknown. However, it is thought that its neuroprotective effects likely stem from reducing a phenomenon known as excitotoxicity.
Neurons communicate with each other through chemical messengers called neurotransmitters. The signalling of these messengers needs to be tightly controlled. Too little or too much signaling will disrupt normal functions of the brain and cause damage to cells. Excitotoxicity is the result of excessive signaling by glutamate, one of the most abundant neurotransmitters in the brain. Glutamate is also associated with many neurodegenerative diseases.
Riluzole prevents this excessive signaling through several mechanisms. It is hypothesized that the effectiveness of riluzole in ALS treatment is the result of this neuroprotective property.
Riluzole for Ataxia
The neuroprotective function of riluzole has been a point of interest for the treatment of other neurodegenerative diseases since its approval. Multiple clinical trials have been conducted for patients with neurodegenerative diseases including Parkinson’s disease, Huntington’s disease, multiple system atrophy, and ataxia.
In 2010, a pilot trial was conducted with 40 patients with cerebellar ataxia who showed a lower level of motor impairment, measured by the International Cooperative Ataxia Rating Scale. A follow-up trial was then performed in 2015 for 55 patients with spinocerebellar ataxia (SCA) or Friedreich’s ataxia. Similarly, patient impairment had improved by an alternative measurement using the Scale for the Assessment and Rating of Ataxia. These findings indicate the possibility of riluzole being an effective treatment for cerebellar ataxia. However, more long-term studies and ones that are specific to different types of SCA need to be conducted to confirm the results.
Riluzole in Development
Even though riluzole was discovered more than 25 years ago, variations of the drug are still under development. As ALS often affects a patient’s ability to swallow, a new formulation of riluzole that is absorbed by placing it under your tongue is being developed under the name Nurtec.
Another prodrug version of riluzole, named Troriluzole (BHV-4157), may be better absorbed by the body with fewer side effects. Troriluzole is currently in phase three clinical trial for patients with different types of SCA. The trial is expected to be complete by November 30, 2021, and will hopefully provide more insight into the effectiveness of Troriluzole in SCA patients.
What shared research questions is your group investigating?
We use high field, multi-nuclear magnetic resonance imaging (MRI) and spectroscopy (MRS) to explore how diseases impact the central nervous system. These changes can be structural, functional, biochemical and metabolic alterations. For example, we apply advanced MRI and MRS methods in neurodegenerative diseases and diabetes.
We also lead efforts in research taking place at multiple different cities across the United States and the world. As you can imagine, studies spread out across such a big area require a lot of coordination and standardization. We design robust MRI and MRS methods to be used in clinical settings like these.
Another important question for our team is how early microstructural, chemical and functional changes can be detected in the brain and spinal cord by these advanced MR methods. We are interested in looking at these changes across all stages of disease.
Why does your group do this research?
The methods we use (MRI and MRS) can provide very helpful information to be used in clinical trials. These biomarkers we look at can provide quantitative information about how a disease is progressing or changing.
There is good evidence that subtle changes in the brain can be detected by these advanced MR technologies even before patients start having symptoms. If we better understand the earliest changes that are happening in the brain, this can in turn enable interventions at a very early stage. For example, we could treat people even before brain degeneration starts to take place.
Why did you form a research group connecting multiple labs?
We came together to form the CMRR Ataxia Imaging Team to benefit from our shared and complementary expertise, experience, and personnel. We can do more together than we could apart.
Are you recruiting human participants for research?
Our focus is on MR spectroscopy, specifically neurochemistry and metabolism studies. We focus on spinocerebellar ataxias. Also, we have been leading MRS technology harmonization across different sites and vendors.
The Henry Lab
Principal Investigator: Dr. Pierre-Gilles Henry
Year Founded: 2006
We develop advanced methods for MR spectroscopy and motion correction. Then apply these new methods to the study of biochemistry and metabolism in the brain and spinal cord in various diseases. We have been working on ataxias since 2014.
Fun Fact about the Henry Lab: The French language can often be heard in discussions in our lab!
The Lenglet Lab
Principal Investigator: Dr. Christophe Lenglet
Year Founded: 2011
We develop mathematical and computational strategies for human brain and spinal cord connectivity mapping. We do this using high field MRI. Our research aims at better understanding the central nervous system anatomical and functional connectivity. We are especially interested in looking at this in the context of neurological and neurodegenerative diseases.
Members of our team have their roots in 7 countries (US, Turkey, France, India, Mauritius, South Korea, Ghana) and 4 continents (North America, Europe, Asia, Africa)
We study how mishaps and damage in the cerebellum lead to the symptoms experienced by ataxia and tremor patients. By looking at human brains, as well as brains from mouse models, we study how different changes in brain structure can lead to symptoms. This includes how well different parts of the brain can communicate with each other.
Why do you do this research?
When you ask patients about the challenges living with ataxia or tremor, they will talk to you about their symptoms. Symptoms can make different activities of daily living very challenging! By connecting specific brain changes to specific symptoms, we want to develop treatment options that target specific diseases. By doing this, we hope to improve patient’s quality of life.
The Kuo lab is part of the Initiative for Columbia Ataxia and Tremor. It’s a new Initiative at Columbia University to bring a group of physicians, scientists, surgeons, and engineers to advance the knowledge of the cerebellum and to develop effective therapies for ataxia and tremor.
Are you recruiting human participants for research?
Yes, we are! We are looking for participants for clinical research and trials. You can learn more about the studies we are currently recruiting for at this link.
In the Kuo Lab, we call ourselves “the Protector of the Cerebellum in New York City”.
Neurons are the cells that serve as building blocks of the nervous system. The brain contains an enormous variety of neurons, and they all need to get a start somewhere. The process by which neurons are formed is called neurogenesis.
When does neurogenesis happen?
Nearly all neurogenesis occurs before the age of 2 when the brain is in the early stages of being formed and refined. While most cells in the body are replaced as they wear out or get injured, neurons in the brain do not. By young adulthood, the brain has largely stopped making new neurons. Other than serving as an excellent reason to wear a helmet and otherwise protect your head from injury, this lack of new neuron formation doesn’t have a noticeable effect on how we go about our daily lives. After all, neurons are an incredibly adaptable cell type that readily change in response to a person’s environment and experiences.
In the past few decades, we have learned that there is an exception to the “all neurons are born early in life” rule. Some research has shown that new neurons can, in fact, be formed during adulthood in specific brain areas. For example, the hippocampus, a brain structure important for its role in forming and maintaining memories, continues to create neurons over the course of one’s life.
The purpose of these newly generated neurons is still debated. However, numerous studies have shown that neuron formation in the hippocampus is reduced in instances of psychiatric and neurodegenerative disorders. This includes certain types of ataxia like SCA1. This is thought to contribute to changes in cognitive function and mood, though the exact mechanisms are still being determined.
Why is neurogenesis interesting for the spinocerebellar ataxias (SCAs), aren’t these neurodegenerative disorders?
Since the discovery of neurodegenerative disorders, most research has focused on symptoms and how to delay symptom onset. This view sees neurodegenerative disorders, like the SCAs, as outcomes of mid to late-life when the toxic effects of mutant proteins become suddenly rampant. However, these disorders are caused by proteins that are present from the very earliest stages of brain formation.
In 2018, researchers studying SCA1 found that neurogenesis is increased in the cerebellum of young mice. This changed how the cerebellum communicates with the rest of the brain. This suggests that cerebellar function can be affected by more than neuronal loss. It could be of wider interest in the SCAs given the cerebellar dysfunction that is common between them. No research on cerebellar neurogenesis has been performed in other SCAs by this point. However, there are some indications that neurogenesis may also be altered in SCA2.
Additionally, Huntington’s Disease, a polyglutamine repeat disorder in the same disease family as several SCAs, has been shown to have increased neurogenesis in the cortex in both young mice and prenatal babies. The combination of these recent studies has made early neuron formation an area of key interest in the study of neurodegenerative disorders.
Current theories in the field contend that while the brain can compensate for changes in neuron numbers in early life, altered neurogenesis could be creating unique brain circuitry in individuals with known disorder-causing protein mutations. These changes could make them more vulnerable to neuronal dysfunction and neurodegeneration later in life.
Evidence for changed neurogenesis in SCAs, both early and late in life, adds a new layer of consideration to what we broadly think of as a mid- to late-life neurodegenerative disease. Additional research in coming years will hopefully provide more insight into how these additional facets of neural health may inform the development of new therapies.
Snapshot written by Carrie Sheeler and edited by Dr. Chloe Soutar.
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