A multinational investigation discovered gut bacteria in the damaged parts of the eyes of people whose sight loss was brought on by a specific genetic mutation known to cause eye illnesses that result in blindness.
The results of the recent study, which was co-authored by Chinese researchers and published in Cell, indicate that the genetic mutation may weaken the body’s defences, allowing dangerous germs to enter the eye and result in blindness.
Trillions of bacteria reside in the gut, essential for a balanced digestive system. They might, nonetheless, also be dangerous.
The influence of the Crumbs homolog 1 (CRB1) gene, which is known to be expressed in the retina—the thin layer of cells at the back of the eye was being studied by the researchers. The gene builds the blood-retina barrier and controls fluid flow into and out of the eye.
The CRB1 gene is linked to hereditary eye diseases, most notably variants of retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA); globally, the gene accounts for 10% of instances of RP and 7% of cases of LCA.
The primary cause of blindness among working-age individuals in the UK is inherited eye disorders. Diseases can start at any time from very early infancy to maturity, but once they do, there is no turning back and the effects last a lifetime.
The CRB1 gene is essential for regulating the integrity of the lower gastrointestinal tract, the study team found using mice models—this is the first finding of its kind. There, it controls the information that travels between the gut’s contents and the body’s other tissues, fighting infections and dangerous microorganisms.
The researchers discovered that these barriers in the stomach and the retina may be broken down by a specific mutation that dampens the production of the gene, lowering its function. This allows bacteria from the gut to enter the body and travel to the eye, where it causes lesions in the retina that result in blindness.
Importantly, even though it did not repair the damaged cell barriers in the eye, treating these bacteria with antimicrobial medicines, such as antibiotics, was able to save the mice from losing their vision.
Future research will examine the applicability of this mechanism and possible therapy in humans.
We found an unexpected link between the gut and the eye, which might be the cause of blindness in some patients.Our findings could have huge implications for transforming treatment for CRB1-associated eye diseases. We hope to continue this research in clinical studies to confirm if this mechanism is indeed the cause of blindness in people, and whether treatments targeting bacteria could prevent blindness.
Additionally, as we have revealed an entirely novel mechanism linking retinal degeneration to the gut, our findings may have implications for a broader spectrum of eye conditions, which we hope to continue to explore with further studies.
Professor Richard Lee
The study was an international partnership between the UCL Institute of Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust, and researchers from Zhongshan Ophthalmic Centre, Sun Yat-sen University, China.
Source: UCL News
Journal Reference: Shanzhen Peng, Jing Jing Li, Wanying Song, Ye Li, Lei Zeng, Qiaoxing Liang, Xiaofeng Wen, Haitao Shang, Keli Liu, Peiyao Peng, Wei Xue, Bin Zou, Liu Yang, Juanran Liang, Zhihui Zhang, Shixin Guo, Tingting Chen, Wenxuan Li, Ming Jin, Xiang-Bin Xing, Pengxia Wan, Chunqiao Liu, Haotian Lin, Hong Wei, Richard W.J. Lee, Feng Zhang, Lai Wei. CRB1-associated retinal degeneration is dependent on bacterial translocation from the gut. Cell, 2024; DOI: https://doi.org/10.1016/j.cell.2024.01.040
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