Introduction: Ocular allergy (OA) is characterised by ocular surface itchiness, redness and inflammation. Inflammation and eye-rubbing, due to allergy-associated itchiness, are common in OA and may trigger changes to the ocular surface biochemistry. The primary aim of this study was to assess differences in human tear miRNA expression between OA sufferers and healthy controls during peak allergy season in Victoria, Australia.
Methods: 17 participants (5 healthy controls, 10 mild OA sufferers' and 2 moderate OA sufferers’) aged 18-45 were recruited. OA status was defined using a validated symptoms questionnaire. Tear samples were collected using a minimally invasive microcapillary flow technique. Tear samples were pooled by OA status; and miRNAs were extracted using the Qiagen miRNeasy Serum/Plasma Kit (Qiagen, Germany). miRNAs were assessed by RNA-Seq and data were analysed using Qiagen GeneGlobe, FunRich and IBM SPSS software. Differentially expressed miRNAs were filtered by significance (p<1e-10) and log2 fold-change of +/-2.
Results: 3033 miRNAs were quantified in all tear samples, of which 159 showed a significant difference in expression between the different OA groups (FDR-adjusted p<0.05). 29 differentially expressed miRNAs were unique to the moderate vs control group, 54 were unique to mild vs control and 76 were differentially expressed in both mild and moderate groups compared to controls. After filtering, 8 miRNAs were identified as potential biomarkers of OA, including miR-126-3p, miR-223-3p and additional novel miRNAs with a high level of significance (p<1e-15) and large log2 fold-change.
Conclusion: Of the highly novel potential miRNA biomarkers identified by this study, some were linked to wound healing, angiogenesis, and inflammation. These biopathways may manifest as symptoms pathognomonic to OA, such as of inflammation, redness, and itchiness on the ocular surface; thus, providing novel drug targets for the treatment and management of OA.