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Platelets in the driving seat of inflammation in MS

  • Platelets play a role in infection and immunity but the role of platelets in MS is not known.
  • New research has identified a role for platelets in MS-like disease in mice.
  • Platelets were found in areas of white and grey matter damage and seem to drive inflammation rather than simply make it worse.
  • Interest in platelets in MS is high as there are already a number of medications approved for use in humans which alter the function of platelets.

Platelets are a very small cell found in the blood that are known for their role in clotting blood to stop bleeding. More recently it has been discovered that platelets play a role in infection and immunity. Researchers led by Professor Karlheinz Peter from the Baker IDI Heart and Diabetes Institute in Victoria are investigating the role of platelets in MS.

Professor Peter and his team have shown in earlier work that platelets are found to rise in the blood early on in the disease in laboratory models of MS. In their new research study, funded by MS Research Australia and partner CharityWorks for MS, and published in the Journal of Neuropathology and Experimental Neurology, they were trying to find out if platelets just make inflammation in the brain worse or whether they have a driving role in the initial development of inflammation in MS.

To do this, they tracked platelets in the blood and mapped the location of platelets throughout the brain during different stages of the disease. The first set of experiments showed that the number of platelets in the blood rises very early in the disease, before any clinical symptoms are seen. This is important as the high levels of platelets in the blood could be used as a marker before symptoms develop. The team also showed that by blocking the rise in platelets in the blood at this early stage, they could prevent the MS-like illness from developing at all.

They then went on to track the platelets within the brain, finding that the platelets were the first cells to enter the brain from the blood and that the immune cells responsible for initiating the damage in MS followed them. This is why, when the platelets were blocked, there was no damage to the brain – as immune cells did not leave the blood and cause inflammation. This result suggests that platelets are in the driving seat when it comes to inflammation in the brain and spinal cord in MS.

Mapping of the platelets in different parts of the brain showed that platelets travelled to both white matter and grey matter, but at different times. In the grey matter areas the platelets were clustered around the nerve cells. These experiments added to the evidence that the platelets were promoting inflammation near the nerve cells and driving disease. When looking at parts of the visual system, one of earliest areas to be damaged in the model they were using, the researchers also identified the platelets were involved at the first stages of disease.

This work is the first to show that platelets may be driving inflammation in MS and overturns the current belief that platelets merely make existing inflammation worse. If the same sequence of events can be replicated in human MS, the fact that platelets are such an early player in the disease process makes them a great candidate for tracking the progression of MS, especially before there are any clinical signs. Interest in platelets in MS is also high as there are already a number of approved medications that target platelet functions in use for other diseases. This means safety trials and other groundwork has already been done, making it an attractive option for new therapies for MS.

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Platelets in the driving seat of inflammation in MS