Dry eye: taking a probiotic would be effective in mice

Tingling, itching, burning sensations, sand or foreign body in the eyes… Dry eyes cause very uncomfortable symptoms. In question, a poor quality or a decrease in the production of tears. Today, almost a third of the adult population is affected. The number of people suffering from dry eye has been steadily increasing in recent years due to our living conditions (computer work, air conditioning, pollution).

The treatment is based on the use of products that replace tears because currently it is impossible to regenerate a lacrimal gland (which produces tears). But a recent study could give rise to a new treatment capable of acting on the lacrimal gland.

The probiotic strain Limosilactobacillus reuteri DSM17938

Researchers at Baylor College of Medicine in Houston, Texas have identified a probiotic bacterial strain capable of alleviating dry eye symptoms. The Limosilactobacillus reuteri DSM17938 probiotic strain was successfully tested on mice with dry eye. The study results were presented at ASM Microbe 2023, the annual meeting of the American Society for Microbiology.

“Dry eye syndrome is a common disorder, affecting 1 in 20 people in the United States. Currently available treatments only relieve patients’ discomfort but do not cure the disease. And in some patients, these treatments are not very effective, or even not effective”, said Dr. Laura Schaefer, professor of microbiology at Baylor College of Medicine and co-author of the study. Faced with this observation, Dr. Schaefer and his team set out to find new, more effective treatments. They wanted to test a probiotic strain found in the gut microbiota to treat dry eye syndrome because their previous work had shown a link between gut bacteria and dry eye symptoms.

“We performed several experiments on mice, in which we used gut bacteria from patients with Sjögren’s syndrome* and gut bacteria from patients without eye disease”, explained the researcher. “When mice are colonized with gut bacteria from patients with Sjögren’s syndrome, they develop greater dry eye than mice colonized with gut bacteria from healthy patients, under the effect of exposure to conditions that promote dry eyes”, explained Dr. Schaefer.

“This shows that gut bacteria present in the microbiota of healthy people protect the surface of the eye in dry conditions. Which means that a treatment with probiotic bacteria could be effective in treating dry eye”, suggests the researcher.

An intact ocular surface in mice given the probiotic

To verify their hypothesis, Dr. Schaefer and his team wanted to test a probiotic strain on mice suffering from dry eye syndrome (they were given an antibiotic that “killed” the good bacteria in the intestinal microbiota). These mice were then exposed to severe drought conditions and received either the probiotic strain Limosilactobacillus reuteri DSM17938, or a saline solution (control group). After 5 days of treatment, the scientists noticed that the mice that had received the probiotic strain were in better shape and had an intact ocular surface. This was not the case with the mice that received the saline solution. In addition, the probiotic-fed mice had a higher number of goblet cells (which secrete mucus) than the others.

“Our hypothesis was that the probiotic protects the eye, and our work has shown this to be true.”, welcomed Dr. Schaefer. “This strain in particular, DSM17938, has been extensively studied. It is known to reduce inflammation in other tissues, including the gut, and improve the barrier function of the gut. On the other hand, this is the first time that its effectiveness on eye health has been evaluated.”, concluded the researcher.

Although this work is promising and represents hope for all dry eye sufferers, additional studies need to be conducted on humans to confirm the effectiveness of this probiotic treatment.

*An autoimmune disease that causes dry mouth and eyes.