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Can reducing stress on the legs of Mice teach us about Spondyloarthritis?

Can reducing stress on the legs of Mice teach us about Spondyloarthritis?

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By Dr Irwin Lim, Rheumatologist

Professor Dirk Elewaut visited us at our Parramatta clinic today. He’s on a speaker tour around Australia and kindly agreed to come to talk to our team (I’m really ticked off that I forgot to get a photo for this post).

He talked about many aspects of Ankylosing Spondylitis (AS) and spondyloarthritis (SpA). It was entertaining and engaging. One particular topic has been playing on my mind so I thought I’d give you my simple man’s interpretation.

In a series of experiments, his group looked at how mechanical stress can lead to enthesitis (learn about enthesitis here) and new bone formation, features common to AS/SpA.

  • They convinced some genetically modified mice to take part. These mice get a spondyloarthritis-type disease.
  • The first signs of inflammation in these mice occur at the enthesis, and typically at the achilles tendon insertion and/or plantar fascia insertion.
  • When they looked under a microscope, these areas in these mice show lots of inflammatory cells. This is what would be expected.
  • They then (as ethically & comfortably as possible) suspended the hind limbs of the mice. This meant that there was much reduced load on these hind limbs.
  • In these unloaded hind limbs, there was very much less accumulation of inflammatory cells at the enthesis. There is also less new bone formation.

The conclusion is that these findings provide proof of the concept that actual mechanical strain drives both entheseal inflammation and new bone formation (click here for the abstract).

Now, mice and humans are quite different.

But, let’s assume that these findings can be applied to patients with SpA.

We know our patients with AS and SpA get a lot of heel pain and achilles problems, in addition to enthesitis elsewhere.

If a trigger for this is mechanical load or stress, some questions arise:

  • is this why males get the disease in their early adulthood when they’re running around and playing more vigorous sport?
  • exercise usually helps patients with AS and SpA greatly but could it possibly be detrimental?
  • perhaps, the type of exercise matters more: high impact like jogging versus lower impact like swimming
  • is a desk-based sit-on-your-bum job better than a stand-all-day type of job?

I am by no means advocating stopping or changing exercise if you have AS or SpA. We just don’t know yet.

A lot more research in mice (they’re convincing some mice to now run very far and very fast to see what this does to the entheseal region) and some research in humans will be needed.

But, I thought it would be interesting for you to ponder.

Dr Irwin Lim is a rheumatologist and a director of BJC Health. You should follow him on twitter here.
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