Motor neurone disease: Researchers hope existing drugs can reverse deadly nerve damage
Have researchers in Scotland truly found a way to reverse the damage done to nerve cells by motor neurone disease (MND)?
A new study suggests that it all comes down to boosting the energy output from the mitochondria, the cells’ power supply.
How can that be done? Possibly with drugs that already exist.
The researchers, from the University of Edinburgh, are already looking “for existing drugs that boost mitochondrial function and may be able to be repurposed to treat MND.”
Overall, this is a startling development, albeit one that has to be tempered with wait-and-see caution. There are thousands of people around the world, sufferers and their families, desperate for even a glimmer of good news.
People with MND progressively lose the use of their limbs and ability to speak, swallow and breathe, whilst their mind and senses usually remain intact.
The average life expectancy is two and a half years.
What is this all about?
Motor neuron cells are nerve cells that control movement. An axon is the long part of the motor neuron cell that connects to the muscle – and it can be up to a metre long.
The starting point in the study was examining “axonal dysfunction” – a common problem in neurodegenerative disorders, including in amyotrophic lateral sclerosis (ALS), a form of MND.
The axon is the part of the cell that carries messages to and from the muscle. In people with MND, the axon is shorter and the messages aren’t properly conveyed. Scientists have shown this is because the axon isn’t getting enough energy from the cell’s mitochondria.
For axons to function properly, they need a lot of energy. The scientists wondered if the production of energy in the cells is put out of whack by MND. And if that was true, could it be fixed – and if so, could the axon be restored to full function?
How did the scientists investigate this?
The researchers – from the Euan MacDonald Centre for MND Research at the University of Edinburgh – used stem cells taken from people with the C9orf72 gene mutation that causes both MND and frontotemporal dementia.
They discovered that, in these human stem cell models of MND, the axon was shorter than in healthy cells.
The study then found the back-and-forth movement along the axon was impaired.
Dr Arpan Mehta led the research, which strongly suggests nerve function can be restored to a damaged axon. Photo: University of Edinburgh
And then, bingo! Once the mitochondrial performance was boosted, the axon – think of a stunted tree suddenly getting water and nourishment – regained its healthy function. Back to normal.
This then allowed the mitochondria to travel freely along the axon.
The study also examined human post-mortem spinal cord tissue from people with MND. The tissue was obtained from the Medical Research Council Edinburgh Brain and Tissue Bank.
These examinations supported the findings from the stem cells.
Time-lapse films below illustrate this effect
The first film shows mitochondria travelling along an axon in a healthy motor neuron:
This second film shows how the mitochondria becomes stalled as it attempts to travel along damaged motor neuron with the C9orf72 gene:
In this third film we see a damaged motor neuron with the C9orf72 gene restored to function after boosting the mitochondria:
Clinical trials with existing drugs the next step
Dr Arpan Mehta, the Lady Edith Wolfson Fellow and a PhD student at the University of Edinburgh, led the study. In a prepared statement he said:
“The importance of the axon in motor nerve cells cannot be understated. Our data provides hope that by restoring the cell’s energy source we can protect the axons and their connection to muscle from degeneration.
“Work is already underway to identify existing licensed drugs that can boost the mitochondria and repair the motor neurons. This will then pave the way to test them in clinical trials.”
Although the research focused on the people with the commonest genetic cause of the ALS (amyotrophic lateral sclerosis) type of MND, researchers are hopeful that the results will also apply to other forms of the disease.
By the way: Frontotemporal dementia is a consequence of progressive damage to the frontal and/or temporal lobes of the brain. The right and left frontal lobes at the front of the brain are involved in mood, social behaviour, attention, judgement, planning and self-control.
Hence, damage can lead to reduced intellectual abilities and changes in personality, emotion and behaviour.
More than 2000 people have MND in Australia, of whom 60 per cent are male and 40 per cent female, according to figures from MND Australia.
The mean time from onset to confirmation of diagnosis is 10 to 18 months, and approximately 58 per cent of people with MND are under 65.