Eye diseases that until now were solely attributed to genetic causes may be due – at least in part – to gut bacteria that “escape” from the gastrointestinal system and “travel” to the retina of the eye, according to a new study published in scientific journal “Cell”.
A complete turn to the current knowledge
Until now it was believed that our eyes are protected by a layer of tissue that bacteria cannot penetrate.
“So these results are surprising,” Martin Kriegel, a microbiome researcher at the University of Münster in Germany, who was not involved in the study, who was not involved in the study, commented on the Nature journal’s website, adding that “we are talking about a complete reversal of what we knew as today”.
The role of the CRB1 gene
Inherited retinal diseases such as retinitis pigmentosa affect approximately 5.5 million people worldwide. Mutations in a gene called CRB1 (Crumbs homolog 1) are a major cause of such serious eye diseases, some of which cause blindness.
Previous studies have shown that the presence of bacteria in the eyes is not as rare as ophthalmologists thought, leading the authors of the new study to wonder whether bacteria can cause retinopathy, said study lead author Richard Lee, an ophthalmologist who at the time conducting her work at University College London.
“Loose” of cell bonds
Mutations in CRB1 weaken the bonds between the cells that make up the “lining” of the gut while also playing an important role in weakening the protective barrier that surrounds the eyes, Li and his colleagues found.
Mutant mice
This discovery prompted Lai Wei, also an author of the new study, an ophthalmologist at Guangzhou Medical University in China, to create mice with Crb1 mutations and reduced levels of bacteria in the gut.
As it turned out, these mice did not show problems in the cell layers of the retina unlike other mice that had the “typical” intestinal flora.
Successful administration of antibiotics
Additionally – and this was particularly important – giving the mutant mice antibiotics led to a reduction in damage to their retinas. This suggests that patients with CRB1 mutations may benefit from antibiotics or anti-inflammatory drugs that reduce the effect of bacteria.
“If this is a new mechanism that leads to retinopathies that can be treated, then the lives of many people will be changed,” noted Dr. Lee. However, he hastened to add that we do not know if these findings from mice will be able to be “translated” into effective treatment for humans.
The doubts
Although the new knowledge may lead to testing antibiotic therapy in patients with genetic eye diseases (which may be possible without particular risks and side effects), scientists do not yet know whether CRB1 mutations cause harmful genetic changes in the eyes, even when no bacteria.
So probably in humans antibiotics can help to some extent in case of retinal damage but not completely cure or reverse its diseases.
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