Monday 12th October was World Arthritis Awareness Day and people from around the world showed their support by sharing a high five image to raise awareness of rheumatic and musculoskeletal diseases (RMDs). The theme of the day was ‘its’s in your hands, take action’, and we were all asked to take action and really make a difference to the quality of life of people with RMDs. This week’s blog talks about AKU as a model of studying arthritis and what we have learnt from AKU research.

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Arthritis causes pain and inflammation in the joints and affects around 10 million people in the UK. Here, at The AKU Society we are very proud to show our support for World Arthritis Awareness Day. Early onset osteoarthritis (OA) is amajor symptom of AKU and the fast progression and severity of OA means that AKU is a very good model to study Arthritis.

Osteoarthritis (OA) is the most common form of arthritis. It is caused by wear and tear and is associated with the breakdown of cartilage in joints. Despite being common, OA has no effective therapy and treatment is limited to pain killers, anti-inflammatories and joint replacements.

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In AKU, OA is caused by homogentisic acid (HGA) attacking bone and cartilage, which causes cartilages to become black and brittle and rub against each other, damaging them and the bone underneath them. Physically both have th

esame effects; causing damage to cartilage and bone and resulting in severe pain. OA has different levels of progression, making it difficult to pinpoint one group of patients. In AKU, OA progresses much faster and is much more severe. This makes AKU an ideal model for investigating the underlying mechanisms of OA.

So, what have we learnt about arthritis from AKU research? Our partners in Liverpool and Lancaster have done a large amount of research in this area and have found two major discoveries!

One of these discoveries involved the identification of a new type of bone. Liverpool and Lancaster University scientists discovered novel microanatomical structures in the bone of AKU patients, which they termed trabecular excrescences.

‘Following on from this initial discovery, we then sought and discovered them in some common OA samples’

The discovery of trabecular excrescences in non-AKU OA samples clearly shows that this new bone formation is not caused by excess HGA levels. By analysing this in more detail, researchers were able to propose another potential cause for this discovery: abnormal modelling.

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The identification of high density mineralised protusions (HDMPs) was another major discovery by University of Liverpool scientists. These HDMPs are produced in response to microdamage, with the body acting to fill in the cracks.

‘Although we first identified HDPMs in patients with AKU, we then discovered them in non-AKU OA and ageing joints’

While they are initially produced to protect, over time these HDMPs act like sandpaper and wear away at the soft cartilage, causing significant long-term damage.

AKU research has clearly demonstrated that AKU is a good model for arthritis and we’ve had a fantastic response from AKU patients wanting to help with research. The two big bone and cartilage discoveries are really important in determining the underlying mechanisms of OA and by determining these mechanisms, we are in a far better position to develop effective treatment.