Quebec discovery helps to better understand rheumatoid arthritis

Platelets play a key, and until now unsuspected, role in autoimmune diseases such as rheumatoid arthritis, an international team of a dozen Quebec researchers has discovered.

In short, the researchers found that platelets help white blood cells infiltrate a joint, where they cause chronic inflammation.

“We position platelets as an essential player where, in their absence, white blood cells are unable to adhere to antibodies,” said Professor Éric Boilard, from the Faculty of Medicine at Laval University, to explain the crucial role played by platelets in the process.

The role of platelets in wound healing has been documented for over a century. It is also known that platelets, once at the site of the wound, deploy “arms” that allow them to hold white blood cells in place, so that the latter can quickly fight any potential infection.

Professor Boilard and his colleagues therefore wanted to know if this same mechanism could play a role in autoimmune diseases such as rheumatoid arthritis and lupus.

“We thought that this process of recruiting white blood cells could be preserved in pathologies where we are not talking about bleeding or broken blood vessels, for example when white blood cells invade a tissue or organ in a context of autoimmunity,” he explained.

An initial laboratory experiment showed them that the presence of platelets is essential for the adhesion of white blood cells when they are in a moving liquid such as blood.

A second experiment was conducted on transgenic mice that had been given the human gene that codes for the protein that binds platelets to white blood cells. The researchers initially observed that the disease was more severe in mice that possessed this protein than in those without.

However, their symptoms lessened when they were given an antibody that prevents platelets from binding to white blood cells. Professor Boilard even referred to a “cure”.

The same strategy should work in humans, since therapeutic antibodies that can prevent this binding already exist. However, a delicate balance must be struck between the positive and negative outcomes of platelet-white blood cell binding, as the goal would be to alleviate the symptoms of an autoimmune disease while still allowing the patient to defend themselves against infection.

“We don’t think it would cause (the patient) to bleed heavily, but it would prevent platelets from recruiting white blood cells,” Professor Boilard explained. “We’re still weighing the pros and cons.”

The findings of this study were published by The Journal of Clinical Investigation.

–This report by La Presse Canadienne was translated by CityNews