Identification of a microRNA signature in the serum of non-infectious uveitis patients

Purpose : The cause of non-infectious uveitis (NIU) is poorly understood, but is considered to be mediated by a complex interplay between multiple genetic, epigenetic and environmental factors. MicroRNAs (miRNAs) are non-coding small RNAs that control gene translation into protein. MiRNAs have been shown to be critical mediators in several pathological and inflammatory processes.

Methods : To identify changes in circulating miRNA levels of patients with non-infectious uveitis compared with healthy controls, we exploited a high dimensional and multiple-level approach assessing and integrating the miRNA-ome and leukocyte composition in patients with NIU.
Serum was collected from 54 untreated patients with active and eye-restricted disease and compared with 26 age-matched controls distributed over 2 independent cohorts. TaqMan OpenArray sequencing technology was used to screen for 753 miRNAs in serum in the first cohort. TaqMan single quantitative reverse transcription PCR (RT-qPCR) was used to validate the findings in a second, independent, cohort. Paired flow cytometry results were integrated with the miRNA data to study the relationship between miRNAs and leukocyte composition.

Results : Using stringent selection criteria we identified and independently validated a NIU associated miRNA cluster consisting of seven microRNAs. Pathway enrichment analysis for genes targeted by these miRNAs revealed significant enrichment for the PI3K/Akt, MAPK, FOXO and VEGF signaling pathways as well as for photoreceptor development; all considered to be central pathways for various inflammatory eye conditions. In addition, high dimensional multi-level analysis of the miRNA cluster - guided by proteome and cytome data - linked the presence of the NIU-associated miRNA cluster to a different composition of leukocyte subsets, more specifically CD16+lindimCD11c+HLA-DR- cells, in these patients.

Conclusions : Together, this study identifies a unique miRNA cluster associated with non-infectious uveitis and describes a novel approach to map circulating miRNAs to leukocyte subsets. Furthermore, our data refute the prevailing paradigm that uveitis does not go beyond the eye by demonstrating systemic changes in epigenetic regulation underlying non-infectious uveitis.