Lipocalin–2 Up–Regulation in Patients With Dry–Eye

Abstract

Purpose: : Lipocalin–2 is a member of the lipocalin family. These are small, secreted proteins mostly known because of the studies conducted on lipocalin–1 in tear film. Lipocalins are known to be involved in a variety of biological processes including the regulation of homeostasis, antimicrobial activities, immunomodulation, and epithelial cell growth turn–over. Here, we investigated the presence and the expression of lipocalin–2 in human conjunctiva of healthy subjects and dry eye patients both Sjögren and non Sjögren.

Methods: : Conjunctival samples were obtained by impression cytology by means of PVD membranes and then processed for poly–A RNA extraction. Initial screening of the cDNA transcripts in the different samples was conducted by differential display analysis. Differentially expressed cDNA bands were then sequenced and identified. Southern–blot analysis was later used to confirm differential expression of the transcripts identified. The level of expression of the corresponding genes was then quantified by real–time PCR on total RNA from each sample.

Results: : Several genes including ribosomal proteins, annexin–2, and lipocalin–2 were identified and were found to correspond to differential expression. However, southern blot analysis confirmed only the differential expression of lipocalin–2 and quantitative analyses were performed on lipocalin–2 transcripts. Lipocalin–2 was found to be up–regulated by at least 50–fold in non Sjögren dry–eye (54.6±20.27), and 10–fold in Sjögren patients (9.2±4.7) when compared to healthy subjects (1.00±0.5).

Conclusions: : In this study we describe for the first time the expression of lipocalin–2 gene in human conjunctival epithelium. The expression of this gene was dramatically increased in dry eye patients, both Sjögren and non Sjögren. Indeed, our findings suggest that lipocalin–2 may well play a primary role in the physiopathology of dry eye.

Keywords: cornea: tears/tear film/dry eye • conjunctiva • clinical laboratory testing