Abstract
Abstract: :
Purpose: Clinically, the use of extended wear soft contact lenses (CL) has been correlated with chronic up-regulation of inflammatory mediators and infection. Experimentally, a rat model of extended CL wear has been developed and we have demonstrated that infection does not develop during 4 weeks of continuous wear. Nor did we detect elevated levels of various cytokines and chemokines (Szliter et al. CLAO. 2002; 28:119-23). The purpose of the current study was to develop an experimental model of P. aeruginosa-induced corneal infection in CL-wearing animals in the absence of trauma and to test molecularly for inflammatory mediators. Methods: Rats wore extended wear lotrafilcon A hydrogel lenses in their left eye and the right eye served as a control. After 3-4 days of CL wear, the worn lenses were removed, soaked in a bacterial suspension (1.0 x 108 cfu), and then replaced onto the respective cornea. Following this, the CL-wearing eye of each rat received bacteria topically (1.0 x 108 cfu) and animals were monitored at least 3x/day until corneal opacity was visualized. Ribonuclease protection assays (RPA) were used to detect corneal cytokine and chemokine gene expression, and densitometric analyses of autoradiographs were used to semi-quantitate mRNA levels. Results: Bacterial infection was detected in all CL-wearing eyes within 48 hours following bacterial challenge. For RPA analysis, panels rCK-2 (IL-1α, IL-1ß, IL-1RA, IL-6, IL-10, IL-12 p40, IL-18, MIF, IFN-γ) and rCK-3 (IFN-ß, IFN-γ, TNF-α, TNF-ß, GM-CSF, TGF-ß1, TGF-ß2, TGF-ß3, Lt-ß, MIF) were used. Of these, mRNA expression levels for IL-1α, IL-1ß, IL-1RA, IL-6, GM-CSF and Lt-ß were up-regulated between 2- to 200-fold in experimental CL-wearing, P. aeruginosa-infected versus control corneas. In contrast, IL-18 mRNA expression levels were decreased at least 2.5-fold in experimental versus control corneas. Conclusions: An in vivo animal model of experimental CL-wear in which infection with P. aeruginosa can be produced in the absence of corneal trauma has been established. This rat model will allow further testing and analysis of bacterial keratitis associated with CL wear.
Keywords: contact lens • cytokines/chemokines • keratitis