Veterinarians across the globe are constantly being challenged to improve their treatments for diseases such as osteoarthritis, but what criteria should they use to make decisions between promising new treatments and tried and tested practices? In recent years, regenerative medicine has been lauded as a ‘cure’ for osteoarthritis and many other inflammatory diseases but also labelled as the ‘new snake oil’.1 Which is true and how do we know?
Osteoarthritis is a progressive, inflammatory disease that affects approximately one in five of all domestic dogs.2,3 Current treatments rely primarily on symptom relief using non-steroidal anti-inflammatory drugs,4,5 weight loss programmes and nutraceuticals such as chondroitin sulphate and glucosamine. None of these prevents the progression of the disease so that ultimately surgery becomes the only option. This is expensive, traumatic for the dog and not always effective, especially in the case of elbow osteoarthritis. It would therefore be of great benefit to veterinarians and their patients if regenerative treatments were effective.
What is Regenerative Medicine?
Regenerative medicine has been defined as ‘the branch of medicine that develops methods to regrow, repair or replace damaged or diseased cells, organs or tissues’.6 Living organisms have their own inbuilt ability to regenerate tissue after damage. Natural wound healing involves cells from the immune system, mesenchymal stromal cells, growth factors and anabolic cytokines and scaffolds such as fibrin clots in a coordinated sequence of repair. Regenerative medicine uses various combinations of these factors to encourage healing in areas that are not able to heal fully. The main sources of these factors are blood (as a source of platelet rich plasma), bone marrow and adipose tissue (as a source of mesenchymal stromal cells).
Platelet Rich Plasma (PRP)
PRP is a useful source of growth factors contained within the platelets and also contains fibrinogen which will clot upon injection to form a tight mesh of fibrin fibres entrapping and activating the platelets. This provides a natural scaffold which releases growth factors and paracrine signals that act as chemo-attractants to migratory cells such as mesenchymal stem cells.
PRP can be prepared from an anti-coagulated blood sample. There are many PRP preparation systems available on the market: one uses a selective filtration mechanism but most use a simple two-stage centrifugation which allows the removal of most of the red and white blood cells and leaves a platelet concentrate suspended in plasma. The relative concentrations of platelets and other blood cells vary considerably according to which system is used to prepare the PRP7,8 which could go some way to explaining the variability of clinical results reported for the use of PRP to treat osteoarthritis.9,10,11 Whilst the Cook and Fahey studies both found significant improvements in OA compared with the placebo control, the Franklin study did not find any significant improvements. There are many more less well controlled studies and case series that have been published, but until a consistent method of PRP preparation and growth factor level estimation has been established, it will be difficult to ascertain whether PRP on its own is sufficient to treat OA effectively.