Abstract
Purpose: :
The aim of this pilot study was to analyze the cytokine expression in tears of patients with different subtypes of the dry-eye syndrome as well as healthy control subjects. We developed an advanced antibody-microarray approach, which allows customized screening of patient samples with only a minimal amount of sample.
Methods: :
143 patients, subdivided into healthy subjects (n=38) and dry-eye patients with aqueous deficiency (n=35), lipid phase alterations (n=36) or a combination of both (n=34), were examined. The antibody-microarrays were prepared by spotting antibodies (IL-1-beta, IL-6, IL-8, TNF-alpha, IFN-gamma) with a non-contact arrayer. Schirmer strips were eluted and proteins were labeled with DyLight prior to incubation. Afterwards, slides were scanned with an array-scanner and fluorescence signals were digitized. Spot intensities were determined using microarray evaluation software, normalized and compared using diverse statistic techniques.
Results: :
In each sample protein levels for various cytokines could be measured. Analysis of discriminance demonstrated highly significant differences in cytokine levels between dry-eye patients and healthy subjects (P<0.001). On average cytokines were elevated nearly 2x in dry-eye patients compared to the control group. IL-6 showed the most distinct relative alteration (2.11x). Moreover the dry-eye subgroups differed significantly from each other (P<0.001). Intensities were found to be elevated up to 2.5x in the aqueous deficient and 3x in the combined group in comparison to the control group, showing the strongest difference for IL-6 and IL-8 (P<0.01, P<0.05). Interestingly the groups with lipid phase alteration revealed no significant differences in comparison to the control group for any of the tested proteins.
Conclusions: :
We detected several highly significant differences in the cytokine levels of dry-eye patients vs. healthy subjects. Further, our results support the hypothesis that inflammation plays an important role in the pathogenesis of dry-eye. The fact that the cytokine profiles of the control group and those with a lipidlayer insufficiency are hardly discriminable suggests that in this case other mechanisms are more decisive than inflammation - a finding which should be considered in therapy. The new insight to the different pathomechanisms of dry-eye could provide further hints for the development of a curative treatment in future.
Keywords: cornea: tears/tear film/dry eye • cytokines/chemokines • inflammation