Abstract
Abstract: :
Purpose: To compare and evaluate the changes in the density slow cycling cells at the corneal limbus and mucocutaneous junctional epithelium (MCJ) in dry eye rabbits. Two types of dry eye models were used; one was acute section of the parasympathetic pre–ganglionic, the other by extended wear of soft contact lenses (SCLs). Methods: Two rabbit dry eye models were used for this study: 1) unilateral sectioning of the greater superficial petrosal nerve, the preganglionic input to the pterygopalatine ganglion, 2) bilateral removal of the nictitating membranes followed by extended SCL wear (2 week Pure TM, Seed, Tokyo, Japan) by eyelid suturing or simple eyelid suturing on one side. The control side received tarsorrhaphy. Clinical observations and Schirmer’s tear tests (STT) were performed prior to and during the experiment in both groups of rabbits. BrdU (50mg/kg) was injected (i.p) for 14 days after surgery. At 2 months after final injection of BrdU was given, the corneal limbus and lower eyelid were removed and sectioned. A fluorescence method was used to detect BrdU–incorporating cells in the limbus and MCJ. The number of BrdU–labeled cells was automatically counted using the Scion image software (Scion Corporation, MD, USA). Results: The STT values in both the denervated (5.3±0.4mm) and extended SCL wear (12.4±2mm) models decreased compared to the levels prior to surgery (16.2±2.4mm, 16.5±3.2mm each). The density of BrdU–incorporating cells in the corneal limbus in denervated eyes increased (49.6±2.4cells/0.5mm) compared to the contra–lateral eyes (22.3±2.9cells/0.5mm). The same pattern is seen in the MCJ. In contrast, no observed changes in the density of BrdU–incorporating cells were found in the extended wear SCL model. Conclusions: These results show that parasympathetic nerve is involved in maintaining the density of slow cycling cells in the corneal limbus and MCJ.
Keywords: cornea: epithelium • conjunctiva • proliferation