Expression of inflammatory factors in conjunctiva and assessment of dry-eye associated examination in ovariectomized rat

Abstract

Background Dry eye is increasing gradually recently,but its etiology and manifestation are very diverse.Studies showed that menopause of adult females was one of the risk factors of dry eye.In addition,some inflammatory factors also participate in the pathogenesis and development.But the study on the relationship of sex hormone with inflammation and ocular surface damage is still below understanding.Objective This study was to investigate the expressing changes of interleukin (IL) and tumor necrosis factor-α (TNF-α) in conjunctiva and the manifestation of ocular surface in ovariectomized rat model.Methods Twenty clear female SD rats were randomized into the ovariectomized group and the sham operative group according to randomized number table.Ovariectomy was performed in the ovariectomized group,and abdominal myotomy without ovariectomy was performed in the sham operative group.Serum estrogen and androgen levels were detected by radiation immunoassay 3 months after operation.Schirmer Ⅰ test (S Ⅰ t) and corneal fluorescence staining were carried out in the rats before operation and 1 month,2 and 3 months after operation.The morphology of conjunctival epithelial cells was examined by hematoxylin & eosin staining at the 3rd month after operation.The expressions of IL-17A,IL-1 β,IL-6 and TNF-α in conjunctiva were semi-quantitative analyzed by immunohistochemistry and Western blot.The use and care of the animals complied with State Science and Technology Commission Regulations for the Administration of Affair Concerning Experimental Animals.Results Serum estrogen levels were (23.53 ± 1.65) pg/L and (47.89 ± 1.05) pg/L 3 months after surgery in the ovariectomized group and the sham operative group,respectively; the serum androgen levels were (1.84±0.09) ng/L and (2.47±0.12)ng/L in the ovariectomized group and the sham operative group,respectively,showing a significant decline of serum estrogen and androgen levels in the ovariectomized group compared with the sham operative group (t=-35.37,-12.13,both at P＜0.01).No significant differences were seen in S Ⅰ t between the two groups among various time points (Fgroup =0.38,P =0.55 ; Ftime =0.13,P =0.72 ; Finteraction =0.39,P =0.76).No obvious fluorescence staining was seen in the cornea of both the ovariectomized group and the sham operative group.The histopathological examination showed that the layers of rat conjunctival epithelial cells increased with the disordered arrangement in the ovariectomized group.Immunochemistry showed that the expressions of IL-17A,IL-1β,IL-6 and TNF-α (A values) were significantly higher in the ovariectomized group than those in the sham operative group (IL-17A:t=8.22,P＜0.01 ;IL-1β:t=16.43,P＜0.01 ;IL-6:t=13.44,P＜0.01 ;TNF-α:t=16.26,P＜0.01).Western blot assay showed the similar results (IL-17A:t=19.41,P＜0.01 ;IL-1β:t=12.63,P＜0.01 ;IL-6:t=17.17,P＜0.01 ;TNF-α:t=15.19,P＜0.01).Conclusions Serum estrogen and androgen levels drop obviously,and there is an up-regulation of IL and TNF-α expression in conjunctiva tissue in the ovariectromized SD rats.However,no obvious dry eye-related sign occurs. Key words: Dry eye; Sex steroid; Conjunctiva; Cytokine; Inflammation; Disease model, animal