Researchers in Belgium have demonstrated a link between macrophages, a type of white blood cell, and the development of certain types of inflammatory rheumatism.
The findings could lead to new treatments, according to life sciences research institute VIB.
Professor Dirk Elewaut, in collaboration with Professor Geert van Loo at VIB´s inflammation research centre, found that macrophages can play a key role in a condition known as enthesitis — inflammation of tendons where they attach to the bone — which underlies various forms of inflammatory rheumatism.
Prof Elewaut explained: “Achilles enthesitis is one of the most typical forms of chronic tendinitis. Our research demonstrates that macrophages which lack the anti-inflammatory protein A20 develop early on in their disease an enthesitis of the Achilles tendon.
“We were also able to demonstrate the underlying cause: A20 suppresses the activation of STAT1, a signalling molecule which seems to be key in initiating this inflammation. The absence of A20 therefore leads to a significant increase in STAT1, which promotes the development of enthesitis.”
JAK is one of the key molecules that controls STAT1. In the study, by blocking this molecule using a so-called JAK inhibitor, the researchers were able to prevent the increase of STAT1 and successfully treat the Achilles enthesitis.
In some countries, JAK inhibitors are already available for the treatment of rheumatoid arthritis.
Other existing anti-inflammatory treatments include TNF inhibitors, and this research opens up new prospects for patients in whom TNF inhibitors offer no relief, Prof Elewaut said.
“In the first place, we wish to check whether this mechanism also plays a role in other places in the body, such as the spine. If so, the discovery may offer new options for patients with other forms of inflammatory rheumatic diseases such as spondyloarthritis, an umbrella term for several diseases characterised by inflammation of the spine and joints. It may also offer new treatment options for psoriatic arthritis, a very common form of joint inflammation in patients with psoriasis.”