Inflammation in the CNS is driven by platelets

RESEARCH SUMMARY:  Platelets Drive Inflammation and Target Gray Matter and the Retina in Autoimmune-Mediated Encephalomyelitis.

In this article, we are summarising recent research that has investigated the potential link between platelets and inflammation in multiple sclerosis.  As always, we value your feedback – please feel free to leave any comments or questions under this article, on the Facebook post related to this summary or via Twitter.

WHO?

A team of researchers from La Trobe University and the Baker IDI Heart and Diabetes Institute in Melbourne, Australia.

WHAT?

The study aimed to determine whether platelets (small cells in the blood associated with clotting) are essential for inflammation to occur in the central nervous system (CNS) or whether they just contribute to it.  The abstract of the study can be found here.

HOW?

This research involved using mice with an animal model of multiple sclerosis, known as experimental autoimmune encephalomyelitis or EAE. 

FACT #1: Platelets are cells in the blood that are commonly associated with blood clotting.  However, they have also been shown to be involved in inflammation, tissue repair and the immune response.

FACT #2: Studies have shown that platelets may play a role in a number of diseases, such as stroke, Alzheimer’s disease and multiple sclerosis.

FACT #3:  It is unclear how important the role of platelets is in inflammation in the CNS.  Previous studies have shown differing results that suggest a range of influence, from just being a contributor to the inflammation to being more of a driving factor.

FINDING #1:  The number of platelets increased just prior to when the first signs and symptoms of  EAE (MS-like disease) appeared in the mice.

FINDING #2: The EAE could effectively be treated in the mice by targeting and depleting/reducing the amount of platelets.  However, this treatment only worked if it was started at the time when the platelets were known to begin increasing in number and also required it to be sustained for days (i.e. a couple of treatments were not enough to stop the disease from developing).

FINDING #3: The increase in platelet numbers in the spinal cord occurred before the increase in T cells.  T cells are cells of the immune system that have long thought to be major contributors to the damage to myelin observed in multiple sclerosis.

FINDING #4: Platelets accumulated in both white and gray matter in the central nervous system.

FINDING #5: Platelets were found to leak from blood vessels and accumulate in the retina (an important structure in the eye).  The researchers looked at this specifically due to the fact that optic neuritis (inflammation of the optic nerve) is a common, early symptom in multiple sclerosis.

THOUGHT: This study provides some really interesting new evidence that platelets are an important driving force in CNS inflammation in an animal model of multiple sclerosis.

THOUGHT:  This is at an early stage and the results have been generated from experiments performed in a mouse model of multiple sclerosis.  It is unclear whether these results will translate across to human studies.

THOUGHT:  Whilst there is still more to learn about how exactly platelets may play a role in multiple sclerosis, this avenue presents an opportunity for a new treatment approach.  As many treatments that target platelets already exist and have been approved for use in other diseases, a large amount of safety information is already known and this may help fast-track their use in multiple sclerosis (if future studies do prove this to be a valuable approach).