Evaluation of dry eye syndrom in C57BL/6.NOD-Aec1Aec2 mice

Abstract

Background C57BL/6. NOD-AeclAec2 mouse is considered to be an idea model for the study of the pathogenesis of Sjtigren syndrome,but the cause of dry eye in these mice is unclear. Objective This study was to investigate the histopathological change of the ocular surfaces of C57BL/6. NOD-AeclAec2 mice, and to determine whether dry eye is developed spontaneously in these mice. Methods Forty-five clean C57BL/6. NOD- AeclAee2 mice were used as the experiment group and forty-five C57BL/6J mice（ both male and female）were used as the control group in this study. Detection of fasting blood-glucose, Schirmer＇ s test I （S I t） , lissamine green staining and scoring of the corneal and conjunctival epithelium in the mice were performed at the age of 4,8,12,16 and 20 weeks. Five mice from each group were sacrificed and their corneas were obtained to measure the central corneal epithelium thickness and to count the number of conjunctival goblet cells. In addition,lymphocyte infiltration in the lacrimal gland of the mice was examined with hematoxylin-eosin staining. The ultrastructure of the corneal epithelial cells and microvilli were assessed by scanning electron microscopy. The use and care of the mice were approved by the Experimental Animal Care Committee of the Third Military Medical University. Results No sign of dry eye wasseen in both the 4-week-old C57BL/6. NOD-AeclAec2 mice and 4-week-old C57BL/6J mice. The S I t values in 8- week-old,12-week-old,16-week-old and 20 week-old mice from the experiment group were（ 2.7±0. 9 ）mm, （2.5 ± 0.8 ）mm, （1.8±0.6）mm and（ 1.9±0. 1 ）mm, respectively, showing a significant reduction in comparison with those of the control mice of the same age（ all P〈0.01 ）. The amount of lissamine green staining in the C57BL/6. NOD- AeclAec2 mice gradually increased with age, showing elevated scores in 12-week-old, 16-week-old and 20-week-old mice in the experiment group （all P〈0.01 ）. The central corneal epithelium thicknesses were （20. 18 ± 3.75 ） μm, （ 17.01±5.25 ）μm, （ 14. 19±5.72 ）μm and （ 12.00±3.25 ）μm in the 8-week-old, 12-week-old, 16-week-old and 20- week-old C57BL/6. NOD-AeclAee2 mice, respectively, which were significantly lower than those of the C57BL/6J mice of the same age（all P〈0. 01 ）. The numbers of conjunctival goblet cells were（8.2±2.4） , （6.2±2. 1 ） , （6.1± 2.2） and（4.1±2.0） in the 8-week-old, 12-week-old, 16-week-old and 20-week-old C57BL/6. NOD-AeclAec2 mice, respectively,showing a gradual decrease with age and a significant decline in comparison with those of the C57BL/6J mice of the same age（ all P〈0. 01 ）. Lymphocyte infiltration in the lacrimal gland and destruction of gland ducts were seen by hematoxylin-eosin staining,and acinar abnormality aggravated with aging. Reduction of corneal epithelial cells and the number of mierovilli were distinguished with aging under the scanning electron microscope. The fasting blood- glucose levels of the two groups were both less than 6.0 mmol/L, and no significant difference was found between them at any age（P=0. 637,0. 610,0. 163,0. 086,0. 938）. Conclusions C57BL/6. NOD-AeelAec2 mice develop dry eye spontaneously with aging. The course of disease and characteristics of dry eye in C57BL/6. NOD-AeelAec2 mice is similar to human dry eye. The C57BL/6NOD-Aecl Aec2 mouse is the perfect model to study the pathogenesis of dry eye. Key words: Sjogren syndrome; Dry eye; C57BL/6. NOD-AeclAec2 mouse; Histopathology; Inflammation