Tears of joy

The dry eyes and mouths of half a million people in the UK affected by autoimmune disease Sjogren’s syndrome could, in coming years, be treated with a newly discovered gene therapy.

There is currently no effective treatment for the primary form of the disease, which reduces the tears and saliva the body can produce.

At a cellular level, the damage caused by the immune system attacking the tear and saliva glands means specialised liquid-transporting cells can no longer move water into the ducts of these glands.

To address this, a team of scientists gave the saliva cells in affected mice another water-transporting protein, one found in the kidneys and red blood cells but not in the tear or saliva glands.

The researchers were able to do this permanently by inserting the gene that makes the protein into the DNA of these saliva gland cells, using a specially designed virus.

Senior investigator of the US National Institute of Dental and Craniofacial Research and study co-author, Dr John Chiorini, told OT: “[We] created a new way for fluid to move into the ducts of the salivary gland that opens into the mouth.”

This technique restored saliva secretion in the mice, according to the paper published in online journal PNAS.

However, despite the fact that the virus only inserted the gene into the saliva glands of the mice, there were surprising, positive results seen in the animals’ eyes as well, with tear production boosted.

Dr Chiorini said his team’s leading theory was that the restoration of saliva production may decrease overall inflammation in the body and, therefore, increase tear production.

“More research needs to be conducted to explain why tear production was observed,” he emphasised.

Dr Chiorini said that the introduced protein had already showed exciting results for patients with radiation-induced xerostomia, or dry mouth.

He said a Phase 1 trial with patients with this condition was due to begin in the summer, though a similar clinical trial for Sjogren’s syndrome patients may be a few more years away.

 “Because Sjogren’s syndrome is a complex disease that is poorly understood, additional research is needed to help define the patients who would best respond to gene therapy. This work is underway in my lab,” Dr Chiorini explained.

This DNA insertion technique, known as gene therapy, is being trialled around the world for its medical potential, Dr Chiorini said, adding: “This approach is being used now to develop therapies for many genetic diseases including haemophilia, blindness, and immune disorders.”