New endocannabinoid treatment pathway for osteoarthritis discovered

Scientists from the University of Edinburgh have discovered a potential new pathway for treating osteoarthritis by targeting certain cells and functions found in the joints.

Presented at the European Calcified Tissue Society Congress, the study has highlighted a link between the development of osteoarthritis and the endocannabioid system, which is found in the synovial tissue and fluid that surround joints.

The endocannabinoid system is composed of cannabinoid receptors - known for managing the body's response to the psychoactive effects of cannabis - and endocannabinoid ligands. It has now been found that the type 2 cannabinoid receptor (CB2) can play a key role in defending osteoarthritis.

A study of mice with destabilised knee joints showed cartilage degeneration was up to 40 per cent more severe in those who were deficient in these CB2 receptors than healthy specimens. Moreover, the impact on cartilage was 60 per cent more severe among older mice that developed spontaneous osteoarthritis and were deficient in CB2 receptors.

It was also shown that a synthetic cannabinoid ligand, HU308, was able to significantly inhibit the progression of arthritis in younger mice with normal levels of CB2, while having no effect on animals with CB2 receptor deficiencies.

Stuart Ralston, Arthritis Research UK professor of rheumatology at the University of Edinburgh, said: "Learning what provides natural protection against osteoarthritis can potentially give us a much greater insight into how we can develop treatments … Our next step, we hope, is to investigate the role of the CB2 pathway in humans with osteoarthritis."

A spokesperson for Arthritis Research UK said: "Millions of people are living with the severe, debilitating pain caused by osteoarthritis and better pain relief is urgently needed. This research does not support the use of recreational cannabis; what is does suggest is that there is potential to develop future treatments that mimic the behaviour of cannabinoid receptors without causing serious side effects."