Effects of multipurpose solutions on corneal epithelial tight junctions.

To compare the effects of four commercially available multipurpose solutions (MPSs) on the structure and barrier function of corneal epithelial tight junctions. Human corneal epithelial cells were cultured on collagen-coated slides and then exposed to MPS A (polyhexamethylene biguanide, macrogolglycerol hydroxystearate), MPS B (polyhexamethylene biguanide, poloxamine), MPS C (Alexidine, poloxamine), and MPS D (POLYQUAD, poloxamine) for 60 minutes. Tight junction integrity of the corneal epithelial cells was evaluated with ZO-1 (tight junction-related protein) labeling under laser confocal microscopy. To investigate the changes of ultrastructure in tight junctions of human corneal epithelial cells, an ultrathin cross-section of the cell on collagen membrane was also observed by transmission electron microscopy. For quantitative evaluation of barrier functions, transepithelial electrical resistance of the epithelial cell was measured 30, 60, and 120 minutes after MPS exposure by using a volt ohmmeter. The control (i.e., without MPS treatment) and MPS A-treated epithelial cells showed a normal, continuous linear pattern in ZO-1 staining along with cell-cell junctions. However, epithelial cells treated with MPS B, MPS C, and MPS D showed discontinuous, disrupted line structures at cell-cell borders. This may correspond to a partial breakdown of epithelial tight junctions. Treatment of epithelial monolayers with MPS B, MPS C, and MPS D caused a time-dependent decrease in transepithelial electrical resistance, whereas there was no significant difference between the MPS A-treated group and the control group. These results suggest the possibility that frequent use of a MPS with high cytotoxicity may lead to the breakdown of epithelial barrier functions and increase the risk of associated microbial infections in hydrogel lens wearers.