Blog by Dr Lindsay Marshall, Humane Society International
To artificially create an arthritic-like knee in a perfectly healthy dog requires an awful instrument known as the dropping tower. This device drops a 2 kg weight onto the bent hind leg of an anaesthetised dog – most commonly a beagle, but Labradors, golden retrievers and German shepherd dogs are also used for this. The beagle in the photo is about to have more than 2000 N of force applied to her flexed knee. To put this in some context, a person bench pressing 100 lbs uses around 450 N of force.
Experiments such as these are often couched as “scientific advances,” yet if the point of this to create something that resembles the human osteoarthritic knee, I am not convinced. I doubt that any person with osteoarthritis has laid on a bed with their leg bent whilst a machine applies force to their joint. I am sure that I cannot be alone in wondering how this instant, traumatic event on a dog’s knee resembles the gradual, progressive change in the tissue that occurs due to an inflammatory response, in the way osteoarthritis develops in people.
Osteoarthritis results in an ongoing inflammatory reaction that drives cartilage breakdown, reducing the joint’s shock absorbing capacity, and leads to obvious issues with mobility and pain. For people, there is currently no cure for the condition, and limited understanding of how it arises.Osteoarthritis is an incredibly complex disease. It is the most common form of arthritis, affecting up to 15 percent of adults over 60 and is a major public health priority given the millions of working days lost to this condition every year.
So what can we do? We can stop dropping heavy weights on dogs’ knees for a start, because research using alternatives to animals is finding more solutions and offering additional hope.
To address the issue of the chronic pain that people with the condition have to deal with, we can try and understand human pain better. Techniques such as neuroimaging, (looking at how and where the brain is involved in pain), microdialysis (sampling fluids from all over the body to see what is being released in the pain response) and even re-examining the possible analgesic effects of ‘failed’ drugs (i.e. those that have passed safety and toxicity testing but didn’t help a particular disease) are all options here. As with most conditions, better understanding of what is happening in people is the way to treat a human condition. For older people with osteoarthritis, a clinical trial looking at exercise found that chair yoga was more effective at reducing arthritis-related pain than general health education sessions talking about fitness and osteoarthritis.
More recently, osteoarthritis has been described as a metabolic disorder. This is because in osteoarthritis, a switch in the metabolism of the cells that produce protective cartilage makes them release glucose, which activates inflammatory cells – stimulating them to wreak havoc in the joints. Deeper understanding of how this metabolic shift occurs is likely to give us an idea of how better to treat the inflammation, the underlying cause of osteoarthritis.
In those poor damaged dogs, it is obvious when the ‘arthritis’ started (when the weight was smashed into their leg), but this is not the case for people with the condition – and for people, early detection could be key to reducing further joint damage and minimising their pain and discomfort. This may now be a possibility: a blood test has just been developedshowing that the characteristic damage to proteins from early stage arthritic joints in people is distinguishable from non-arthritic samples.
Computer algorithms can be used to predict how an individual’s disease might progress, and non-surgical management of osteoarthritis has been carefully evaluated as a short-term option. And finally, how about some seaweed with that? Alginate sulphate from the stems of brown algae has shown promising anti-inflammatory effects in laboratory cultures of the human cells implicated in osteoarthritic joint damage- this may lead to new biomaterials for joint repair.
Considering these examples of human-relevant research – none of which relied on animals and all of which were published in the last few weeks – we can see how much great research for this condition is likely to happen in one year, and how much more could happen if we diverted funding away from studies of healthy young dogs being deliberately damaged and focus on more opportunities to apply 21st century science!