Abstract
Purpose: :
In the past several years, certain contact lens cleaning solutions have been linked to ocular surface infection. Loss of mucins from the ocular surface has also been linked with increased susceptibility to infection, and certain preservatives previously used in these solutions have been shown to result in loss of corneal mucins (Gipson et al. 2007; Kim et al. 2006). The purpose of this study was to determine if the components of commonly used contact lens solutions alter corneal surface integrity.
Methods: :
An immortalized line of human corneal limbal epithelial cells (HCLEs; a generous gift from Dr. I.K. Gipson) were used for these studies. HCLEs were plated into 6 well culture dishes at 175,000 cells per well, grown to confluence, then cultured for 7 more days until then became stratified (method described by Gipson et a l., 2007). Cells were then treated with one of four commercially available contact lens cleaning solutions (A, B, C, or D) or a 0.01% solution of benzalkonium chloride (BAC) in PBS. After one hour, the following assessments were made in parallel cultures: 1) loss of cell surface mucins by rose bengal staining, 2) cytotoxicity using an MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, 3) presence of Mucins -1,-4, and -16 in cell extracts and cleavage of these mucins into the media by western blotting, 4) mucin mRNA levels by semi-quantitative RT-PCR. Statistical significance between treated and untreated samples was determined using a two tailed student’s t-test.
Results: :
Only BAC treatment had a significant cytotoxic effect on HCLEs. Treatment with either BAC or solution C (containing aldox, polyquad, and EDTA) significantly reduced the ability of HCLEs to exclude the rose bengal dye, which indicates increased susceptibility to infection. In contrast, treatment with solution B (containing polyhexamethylene biguanide) increased dye exclusion. There was no significant change in mRNA or intracellular protein levels for any treatment. However, treatment with solution C increased the levels of Muc-16 cleavage into the culture medium. Cells treated with solutions containing EDTA exhibited significantly less adherence to the culture dish though cell survival rates were unaffected.
Conclusions: :
Different contact lens cleaning solutions have varying effects on the ocular surface. This information will be valuable in creating future solution formulations.
Keywords: contact lens • cornea: epithelium • cornea: surface mucins