Analysis of Th17-associated cytokines and clinical correlations in patients with dry eye disease

We aimed to investigate the expressions of three Th17-associated cytokines, interleukin (IL)-17A, IL-6 and IL-23, in protein and mRNA levels and their correlations with ocular surface parameters in patients with dry eye disease (DED) through a small sample size case control study. A total of 45 female subjects were divided into Sjögren's syndrome (SS) DED group, non-Sjögren's syndrome (non-SS) DED group and control group. Ocular surface disease index (OSDI) was self-answered and clinical tests including tear-film breakup time (BUT), Schirmer I test, cornea fluorescein staining (CFS) were performed. The conjunctival mRNA expressions of these cytokines were investigated by real-time polymerase chain reaction (PCR) and the levels of protein in tears were measured by mutiplex bead analysis. The correlations between cytokines and ocular surface parameters were analyzed. Results show that the expressions of IL-17A and IL-6 in protein and mRNA levels were both significantly increased in the DED group (P<0.05), and also higher in SS group comparing to the non-SS group (P<0.05). Moreover, IL-17A and IL-6 correlated well with ocular surface parameters (all P<0.05, R values range from 0.5-0.8). Despite the expression of IL-23 was significantly increased in the DED group (P<0.05), there was no significant difference found between the expressions of IL-23 in SS group and non-SS group (P>0.05) and no correlation found between the IL-23 and any ocular surface parameter (P>0.05). These findings indicates that the three Th17-associated cytokines, IL-17A, IL-6 and IL-23, play roles in the pathogenesis of DED and the expressions of IL-17A and IL-6 in tears have potential to be diagnostic biomarkers for DED.