ABSTRACT
@#【Objective】To provide a rabbit model for dry eye using a dry environment induced by Controlled Drying System.【Methods】Twenty-four male New Zealand rabbits were used in the experiment. They were randomly divided into control group and dry group，each one with 12 rabbits. The dry group was randomly housed in Controlled Drying System（CDS）for 14 days. The relative humidity，airflow and temperature were kept at（22±4）%，3~4 m/s and（23~25）℃， respectively. The control group were fed in a normal environment where relative humidity，airflow and temperature were kept at 60%~70%，0.2 m/s and（23~25）℃. The Schirmer test，corneal fluorescein staining，conjunctival lissamine green staining were performed during the experimental process on days 0，3，7，and 14. On the last day，the rabbits were euthanized and the eye tissues were made into paraffin-cut sections. After staining，we evaluated the corneal epithelial thickness and goblet cell number in the conjunctiva using light microscopy. MUC5AC in the conjunctival epithelium was detected by immunofluorescence. The apoptosis level changes on the ocular surface were evaluated using Caspase- 3 by immunohistochemistry. 【Results】 Decreased tear production ，increased corneal fluorescein staining and increased conjunctival lissamine green staining were found on days 3，7，and 14 in the dry group compared with the control group（P < 0.001）. Corneal epithelial thickness of control group and dry group were （58.0±7.2）μ m and（47.8±7.6）μ m ，which showed corneal epithelial thickness of dry group was decreased（P＜0.05）. Goblet cells in the conjunctiva of control group and dry group were 15 ± 4 and 10 ± 2，which showed goblet cells of dry group was decreased（P＜0.01）. The expression of MUC5AC（consistent with goblet cells deficiency） was also reduced. Caspase- 3 was highly expressed on the corneal epithelium in the dry group. IOD/field of control group and dry group were（17±2）% and（20±2）%（P＜0.01）.【Conclusions】 Dry environment can make rabbits have pathological changes of dry eye on ocular surface epithelium. This dry eye model of rabbit caused by Controlled Drying System would be an effective tool to study the pathogenesis of dry eye.
ABSTRACT
@#【Objective】To test the hypothesis that inhibiting sodium absorption via the epithelial sodium channel（ENaC） will increase ocular hydration and cure the rabbit′ s dry eye induced by scopolamine. 【Methods】In the experiment，24 New Zealand rabbits weighing about 2.0- 2.5 kg were divided into 3 groups：tested group（8 rabbits）， control group （8 rabbits），and treatment group （8 rabbits）. For the rabbits in the tested group，they were given subcutaneous injection of scopolamine 4 times a day for 12 consecutive days to induce the dry eye. For the rabbits in the control group，they accepted subcutaneous injection of saline solution. For the rabbits in the treatment group ，they were firstly given the same treatment as the rabbits in the tested group. Then，the local regions in their right eyes received the application of 100 mmol/L amiloride （a sodium channel inhibitor）. Meanwhile，the local regions in their left eyes received the application of equivalent saline solution. We detected ENAC α and ENAC γ subunits of epithelial sodium channel in conjunctival epithelium by fluorescence quantitative PCR and detected the opening of epithelial sodium channel by short- circuit current technology. Finally，we compared the ENaC α and ENaC γ gene expression，corneal fluorescein sodium staining and tear secretion among the 3 groups. Fluorescence quantitative PCR was used to detect ENaC α and ENaC γ subunits of epithelial sodium channel in conjunctival epithelium and short-circuit current was used to detect the opening of epithelial sodium channel. The ENaC α and ENaC γ gene expression，corneal fluorescein sodium staining and tear secretion （immerged length） were compared among 3 groups.【Results】 The results showed that the quantity of tear secretion was（17.00 ± 0.37）mm for the control group，（4.42 ± 1.34）mm for the tested group（P<0.001 vs Control，n=8） and（14.25 ± 0.54）mm for the treatment group（P>0.05 vs Control，n=8）. The results of short-circuit current detection showed that the sodium current was（5.72 ± 0.35）μA /cm2 in normal model and（12.24 ± 0.54）μA /cm2 in dry eye model（P<0.001）. After Amiloride treatment，the sodium current decreased to（4.00 ± 0.61）μA/cm2 （P>0.05） and there was no statistical difference compared with the normal group. According to the results of fluorescence quantitative PCR，the expression of ENaC α and ENaC γ subunits and IL- β in in dry eye model were up-regulated（P<0.01） compared with that in normal group. After topical amiloride application，there were no statistical differences in inflammatory cytokines IL- 1 β，ENaC α，and ENaC γ between the normal group and treatment group（P>0.05，n=8）. After treatment，tear secretion increased （P<0.001），and ocular surface staining improved significantly.【Conclusion】 Topical application of amiloride increase the quantity of preocular tears owing to inhibition of conjunctival sodium channels and could provide an effective new therapy for chronic dry eye.