A gene crucial for making cartilage could be involved in osteoarthritis, say Japanese researchers. Scientists at the Institute of Physical and Chemical Research (RIKEN) have found that a mutated version of a gene called ASPN is more common in people with osteoarthritis. The disease, which affects more than five per cent of adults worldwide, occurs when old cartilage is broken down faster than it is replaced by new tissue. The ASPN gene makes a protein called asporin, which is thought to play a key role in controlling cartilage production.
Osteoarthritis is caused by several genetic and non-genetic factors, and scientists have identified several genes that appear to be involved in the condition. The RIKEN scientists discovered that the ASPN gene is overactive in cartilage tissue from osteoarthritis patients. They think that this could in turn slow down the production of new cartilage, causing the symptoms of osteoarthritis.
The team then looked at the ASPN gene in DNA samples from 548 patients with osteoarthritis of the knee, and 608 healthy controls. They found that affected people were more likely to have a particular version of the ASPN gene, called D14, whilst unaffected individuals were more likely to have the D13 form of the gene.
The scientists also looked at 593 people affected by hip osteoarthritis, and found that they were also more likely than the control group to have the D14 version of the ASPN gene. Further work suggested that asporin works by interacting with a growth factor protein called TGF-beta, and that this process is the key to understanding osteoarthritis. The authors say their findings, published in the journal Nature Genetics, could lead to new therapies for this disease.
Madeleine Devey, of the UK's Arthritis Research Campaign, told BBC News Online that the study was 'a very important paper', saying 'it adds another piece to the jigsaw' of understanding osteoarthritis.