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Gel used to smooth out facial wrinkles could be used to treat dry mouth after scientists grow saliva gland in a dish
A gel normally used to smooth out facial wrinkles could also help millions of people who suffer with chronic dry mouth.
The gel – hyaluronic acid – is a viscous substance that occurs naturally in the body, helping to lubricate joints, keep skin moist and stop the eyes from drying out. In recent years, man-made versions of the jelly-like material have become a popular cosmetic treatment among those seeking younger-looking skin – making it look plump and banishing unsightly lines.
Now a team of scientists have found that synthetic hyaluronic acid is also the perfect environment for growing the cells that release saliva in our mouths. It's the first time that fully functioning cells like this have been grown outside the body – and it's hoped the breakthrough, reported in the International Journal of Oral Science last month, will lead to a new treatment of lab-grown cells that can be transplanted into the mouths of patients suffering persistent dry mouth.
The average healthy adult produces up to two litres of saliva every day, which most people swallow without noticing.
But up to ten million people in the UK suffer from dry mouth – known as xerostomia – when salivary glands under the tongue and around the jaw don't produce enough saliva.
This is often temporary but for some people, dry mouth can become a chronic condition that severely affects their quality of life.
Causes range from nasal infections and diabetes to certain medications (including decongestants) and simply not drinking enough fluids, because 99 per cent of saliva is water.
Studies have also shown salivary gland cells become less efficient as we age, and no longer produce saliva and enzymes.
Patients who have undergone radiotherapy treatment for head and neck cancers, which can damage the glands permanently, are often the most affected. Up to 90 per cent of them develop permanent damage to the salivary glands and dry mouth.
Current treatments for dry mouth range from over-the-counter sprays and pastilles that stimulate saliva production, to artificial saliva – usually available only on prescription.
But in patients whose salivary glands have been damaged or destroyed, there is little that doctors can offer for effective symptom relief.
The hope is that using hyaluronic acid to grow new salivary gland cells and then transplanting them into the mouth could be a better solution – in much the same way that skin is grafted on to wounds or burns to boost healing.
Researchers at McGill University in Canada took a small number of human acinar cells – which produce saliva – and placed them in a hyaluronic acid gel in a petri dish.
Within a week, the cells started to form into large round clusters that mimicked the appearance of human salivary glands.
After two weeks, the cells were still replicating and were metabolically active – for example, producing all the proteins they needed to stay alive and to stimulate the secretion of saliva.
The cells also produced the digestive enzyme alpha-amylase, which is important for stimulating the production of saliva.
Previous attempts to grow these acinar cells in the lab have had little success, as they don't thrive on the type of 'scaffolds' normally used to regrow tissue – such as collagen. The make-up of salivary glands is also complex, with many specialised cells that are difficult to replicate and grow.
Simon Tran, a professor of dentistry at McGill University, who led the research, said it was 'a significant step forward'.
'This study demonstrates that by fine-tuning [hyaluronic acid] gel composition, we can closely replicate the native environment of salivary acinar cells.
'These engineered salivary cells could potentially be delivered via injection directly into the patient's damaged salivary gland, acting much like a graft to restore function.'
But he stressed that it's not yet clear if a one-off injection would suffice, or whether repeat treatments might be necessary to maintain healthy saliva production.
Commenting on the findings, Austen Smith, a consultant oral and maxillofacial surgeon at Sheffield and Barnsley NHS Foundation Trusts, said the new research is a 'valuable move forward to helping damaged tissue heal to its maximal potential'.
And Caroline Geraghty, a specialist information nurse at Cancer Research UK, said: 'It would be a real breakthrough if people could regain full function in their own salivary glands one day so they don't have to rely on temporary fixes.'
But she warned larger human trials are needed to see if the gel jabs are safe and effective.
