We are performing in-depth characterizations of the ocular microbiota of dry eye disease sufferers, with the aim of identifying microbial risk profiles for disease development and severity.
Dry eye disease (DED) affects millions of individuals worldwide. It is characterized by a loss in tear film homeostasis with accompanying chronic inflammation.
However, the initiating and perpetuating factors remain unclear. The ocular microbiome, specifically the interplay between resident microbes and the ocular immune system, alters surface inflammation and may influence DED development and progression.
This project has provided a detailed description of the ocular microbiota associated with good eye-health and identified specific changes in this baseline state which characterize DED.
There is growing evidence from other diseases and conditions that restoration of microbiomes to natural states, so-called microbiota-therapy, is a valid approach to treatment.
More about the project
Causal links between imbalances in bodily microbiomes (usually referred to as dysbioses) are now strongly suspected for several human pathologies, including inflammatory bowel disease, Clostridium difficile infection, and cardiovascular disorders.
Re-establishing the natural balance is known to alleviate symptoms in C. difficile-induced colitis and the condition has been treated post antibiotic-therapy by microbiota transplantation.
This approach might also hold promise for DED or other ocular conditions. Symptom alleviation and treatment possibilities would here lie in addressing imbalances and restoration of protective commensals with associated health and cost benefits.
However, a prerequisite for evaluating this approach is robust characterization of the microbiota of the healthy and DED-states.
There are few comprehensive studies on the ocular microbiota and a current lack of consensus on what can be defined as a natural core set of microbes. This is a necessary reference point for describing the diseased state.
There is also an incomplete understanding of the mechanisms that integrate microbiome-derived signals into host signaling pathways.
The current project, which seems to be the largest of its kind to date, has used both next generation sequencing (NGS) and culture studies (work completed and submitted for publication) in a unique manner to suggest “healthy” core microbiota.
It has also identified DED-associated changes. The addition of a culturing step was propitious and made it possible to proceed to whole genome sequencing, WGS and transcriptomics studies of isolates shown to be significantly linked to DED.
The current work and follow up studies ultimately aim to inform pathophysiological mechanisms of DED and suggest interventions to ameliorate the condition.
The project has two major and mutually informative phases. Initially swabs were taken by a trained opthalmologist at the Norwegian dry eye clinic from both confirmed DED-sufferers and controls. Swabs were cultured for phenotypic characterization and identification, and also used to produce NGS libraries.
Results and future prospects
Using both approaches in artificial intelligence and more traditional statistical models, we have been able to identify some robust markers of the DED state.
Inclusion of culturing studies has allowed phenotypic characterization and WGS of DED-signature microbes. As an example, certain Corynebacterium species were shown to be among the most robust biomarkers of ocular dysbiosis.
We have observed in some patients that a Corynebacterium (usually one clone) came to dominate (greater than 90 percent) of the total DNA sequence reads on the eye.
Against this background we applied for funding to the Intelligent Health Initiative at OsloMet and the Pasteur legacy fund, to perform de novo WGS on Corynebacterium and other isolates of particular interest.
Genome analysis followed by additional phenotyping analyses have provided important clues as to the reasons for dominance of certain clones in DED sufferers.
The work is currently being prepared for submission later this year.
- Oslo University Hospital
- The Norwegian Dry Eye Clinic