The Effects Of Hyperosmotic Stress On Rabbit Ocular Surface Epithelium And MUC5AC Expression

Purpose To investigate the effects of hyperosmotic stress on rabbit ocular surface epithelium and MUC5AC expression.Methods Twelve New Zealand white rabbits were randomly divided into three groups. One group was treated with hyperosmolar saline solution(HOSS),another with normal saline(NS).Both eyes received two drops of the solution six times per day for 14 days. The rest served as controls.Before and after treatments on days 7,14,we performed Shirmer test,measured tear break-up time(BUT) and collected conjunctical impression cytology specimens.The rabbits were killed after day 14.Corneal and conjunctival structures were observed under light and electron microscope.Western blot were carried out to evaluate the expression of conjunctival MUC 5AC.Results Compared with controls and NS-treated eyes,HOSS-treated eyes showed no difference in Shirmer scores on days 7 and 14(P＞0.05,all time points).BUT was significantly shorter either on day 7 or 14.Decreases in conjunctival goblet cell density occurred on days 7.The expression of conjunctival MUC5AC declined.Conjunctival subepithelial inflammatory cell infiltration and cornification of corneal epithelium were observed under light microscope.By examination under electron microscope,we found that microvilli and intercellular junction of corneal epithelium were destroyed with superficial cells swelling,desquamation and increased autophagic vesicles in deep cells.Conclution Hyperosmotic stress can induce decrease of conjunctival goblet cell density and MUC5AC expression,destroy ocular surface epithelial cells,and finally lead to tear film instability.