Microbiome in orbital fat under thyroid associated ophthalmopathy

Thyroid associated ophthalmopathy (TAO) manifests as orbital adipose hyperplasia, leading to high intraocular pressure, severe pain, and blindness. The underlying factors that trigger the abnormal immune process in TAO remain unknown. Here, we aim to test the hypothesis thata microbiome exists in TAO adipose tissue and are associated with TAO. We combined 16S rRNA gene sequencing and Tyramide signal amplification-fluorescence in situ hybridization of the orbital fat samples (size of 1 ​cm∗1 ​cm∗0.5 ​cm) from 36 with TAO ophthalmic patients, including 36 with TAO and 38 non-TAO ophthalmic patients as controls. We also collected environmental samples to perform decontamination using source-tracking algorithms. Bacterial staining signals were observed in both TAO and control sections. 6.2% of the bacterial community from orbital fat passed stringent decontamination against environmental samples. We identified four microbiome types in orbital fat, one of which was exclusive to TAO patients. Similarly, we found a higher proportion of Pseudomonas in TAO, but a lower proportion of Enhydrobacter. Flavobacterium was positively correlated with chemosis. For the first time, we provide evidence for the presence of bacteria in orbital fat tissue which are associated with TAO. Whether this orbital fat microbiome plays a causal role in the pathogenesis and manifestation of TAO requires further investigation.