The Microbiome, Ocular Surface, and Corneal Disorders

Bacterial 16S rRNA gene alterations in the conjunctival sac and lacrimal sac in chronic dacryocystitis

PURPOSE

Dysbiosis of the microbial community in the lacrimal sac has been associated with the occurrence and development of chronic dacryocystitis. The aim of this study was to investigate the microbial characteristics of the conjunctival sac and lacrimal sac in patients with chronic dacryocystitis using 16S rRNA sequencing and explore their relevance to this condition.

METHODS

This was achieved through the application of Illumina MiSeq technology for the comprehensive sequencing of 16S rRNA genes in bacterial DNA samples isolated from the conjunctival and lacrimal sacs of 20 patients with chronic dacryocystitis.

RESULTS

The conjunctival sac microbiota showed slightly higher diversity compared to the lacrimal sac. However, their microbial communities were similar. In the cohort representing the lacrimal sac, there was a notable reduction in the relative abundance of Proteobacteria. Conversely, an increase in the relative richness of phyla such as Firmicutes, Actinobacteria, and Bacteroidetes was observed. Linear discriminant analysis and effect size analysis elucidated a significant enrichment of the Methylobacterium and Cetobacterium genera within the conjunctival sac cohort, in contrast to the lacrimal sac cohort. The dominant pathway in both sites was biosynthesis according to Kyoto Encyclopedia of Genes and Genomes analysis.

CONCLUSION

In individuals suffering from chronic dacryocystitis, the microbiota of the lacrimal sac exhibits a reduced α-diversity and a comparable β-diversity, alongside exhibiting distinct taxonomic profiles when contrasted with the microbiota of the conjunctival sac.

Antibiotic-induced dysbiosis of the ocular microbiome affects corneal circadian rhythmic activity in mice

The ocular surface microbiota plays a critical role in maintaining corneal homeostasis, but its disruption and subsequent effects on corneal functions remain poorly understood. This study investigates how antibiotic-induced microbial depletion affects the corneal circadian transcriptome in C57BL/6J mice. Dysbiosis was induced using a topical antibiotic cocktail, and RNA sequencing was employed to analyze gene expression across eight time points over 24 h. Antibiotic treatment disrupted corneal circadian rhythms, eliminating rhythmicity in 1,812 genes and introducing rhythmicity in 1,928 previously arrhythmic genes. Furthermore, epithelial adhesion was impaired, inflammation was elevated, and neural sensitivity was reduced. More than 50 % of ocular microbial genera exhibited daily oscillations, with six genera showing significant correlations with corneal rhythmic transcripts. Additionally, the administration of TLR agonists restored circadian gene expression patterns, with partial recovery of corneal barrier function and immune homeostasis, further highlighting the potential of microbiota-targeted therapies in treating ocular surface disorders. These findings underscore the critical role of the ocular microbiota in regulating corneal health and suggest that restoring microbial balance via TLR activation may offer new therapeutic avenues for eye diseases.

Unveiling the gut-eye axis: how microbial metabolites influence ocular health and disease

The intricate interplay between the gut microbiota and ocular health has surpassed conventional medical beliefs, fundamentally reshaping our understanding of organ interconnectivity. This review investigates into the intricate relationship between gut microbiota-derived metabolites and their consequential impact on ocular health and disease pathogenesis. By examining the role of specific metabolites, such as short-chain fatty acids (SCFAs) like butyrate and bile acids (BAs), herein we elucidate their significant contributions to ocular pathologies, thought-provoking the traditional belief of organ sterility, particularly in the field of ophthalmology. Highlighting the dynamic nature of the gut microbiota and its profound influence on ocular health, this review underlines the necessity of comprehending the complex workings of the gut-eye axis, an emerging field of science ready for further exploration and scrutiny. While acknowledging the therapeutic promise in manipulating the gut microbiome and its metabolites, the available literature advocates for a targeted, precise approach. Instead of broad interventions, it emphasizes the potential of exploiting specific microbiome-related metabolites as a focused strategy. This targeted approach compared to a precision tool rather than a broad-spectrum solution, aims to explore the therapeutic applications of microbiome-related metabolites in the context of various retinal diseases. By proposing a nuanced strategy targeted at specific microbial metabolites, this review suggests that addressing specific deficiencies or imbalances through microbiome-related metabolites might yield expedited and pronounced outcomes in systemic health, extending to the eye. This focused strategy holds the potential in bypassing the irregularity associated with manipulating microbes themselves, paving a more efficient pathway toward desired outcomes in optimizing gut health and its implications for retinal diseases.