This article was published ahead of print on the official website of Chinese Journal of Ophthalmolog on Apirl 22,2020. Objective: Angiotensin converting enzyme 2 (ACE2) and Transmembrane serine protease 2 (TMPRSS2) are the key proteins for 2019-nCoV entry into host cells. To evaluate the potential infection risk of 2019-nCoV on ocular surface, we compared ACE2 and TMPRSS2 expression among different eye tissues. Methods: Experimental study. Thirty mice were assigned to male, female, aged, diabetic and non-diabetic groups, with 6 mice in each group. Real-time PCR was performed to quantify ACE2 and TMPRSS2 gene expression in conjunctiva, cornea, lacrimal gland, iris, lens, retina, lung, heart, kidney, and liver from male mice. Immunohistochemistry staining was applied to visualize the distribution of the two proteins in different mice tissues, and in human corneal and conjunctival sections. Published transcriptome datasets were extracted to generate the expression comparasion of ACE2 and TMPRSS2 between human conjunctival and corneal tissues, and results were analyzed using Mann-Whitney U test. Female mice, aged mice, STZ-induced diabetic mice, diabetic group control mice were also subjected to ACE2 expression analysis. Results were analyzed using Student's t-test. Results: The expression of ACE2 and TMPRSS2 genes were the highest in conjunctiva among all the six mice eye tissues explored. The expression of these two genes in conjunctiva were lower than that in kidney and lung. ACE2 and TMPRSS2 shared similar expression pattern with the staining concentrated in corneal epithelium, conjunctival epithelium and lacrimal gland serous cells. The expression levels of ACE2 showed gender difference. Female mice had lower ACE2 in conjunctiva and cornea than male mice, with the expression levels being only 43% (t=3.269, P=0.031) and 63% (t=4.080, P=0.015) of that in the male conjunctiva and cornea, respectively. Diabetic mice expressed more ACE2 in conjunctiva (1.21-fold, P>0.05) and lacrimal gland (1.10-fold, P>0.05) compared with the control group. No significant difference on ACE2 expression was found between the aged and young adult mice. The expression level of human conjunctiva ACE2 and TMPRSS2 were significantly higher than that in the cornea (P=0.007), with 5.74-fold and 12.84-fold higher in the conjunctiva than in the corneal epithelium cells, which resembled the situation in mice. Conclusion: The observation of high-level ACE2 and TMPRSS2 expression in conjunctiva among the 6 eye tissues examined suggests that conjunctiva serves as an infection target tissue of 2019-nCoV. (Chin J Ophthalmol, 2020, 56:438-446).
本文于2020年4月22日优先发布于中华眼科杂志官网 目的： 探讨眼部组织新型冠状病毒侵染和激活关键蛋白人血管紧张素转换酶2（ACE2）和跨膜丝氨酸蛋白酶2（TMPRSS2）的情况，明确新型冠状病毒在眼部的侵染基础。 方法： 实验研究。选取30只小鼠，按性别、年龄、是否诱导糖尿病模型分为雄性组、雌性组、老年组、糖尿病组及糖尿病对照组，每组6只。使用荧光定量PCR分析小鼠结膜、角膜、泪腺、虹膜、晶状体、视网膜ACE2基因和TMPRSS2基因表达情况，并与肺脏、心脏、肾脏、肝脏中两个基因的表达量进行比较。使用免疫组化染色分析了小鼠各组织中ACE2和TMPRSS2蛋白的分布和表达情况。另取山东省眼科研究所红十字眼库接收的符合捐献条件的志愿者角膜及结膜组织切片，与小鼠眼部ACE2蛋白和TMPRSS2蛋白表达进行验证比较。同时通过分析已发表的人眼部组织转录组数据库，比较人角膜和结膜中ACE2和TMPRSS2基因的表达情况。对不同性别、年龄、及糖尿病条件下小鼠眼表组织的ACE2基因表达变化进行分析，采用独立样本t检验对数据进行统计学分析。对数据库中人角膜和结膜组织两种基因表达分析，采用Mann-Whitney U检验进行统计学分析。 结果： 在小鼠6种眼部组织中，结膜ACE2基因和TMPRSS2基因表达量最高，但均低于肾脏和肺脏；ACE2和TMPRSS2蛋白阳性染色集中于结膜上皮、角膜上皮和泪腺腺泡。ACE2基因的表达具有性别差异，在雌性小鼠结膜和角膜的表达显著低于雄性小鼠，分别为雄性相应组织的43% （t=3.269，P=0.031）和63% （t=4.080，P=0.015）；糖尿病小鼠结膜和泪腺中的ACE2基因表达略高于非糖尿病小鼠，分别为1.21倍和1.10倍 （P>0.05）；不同年龄小鼠ACE2基因表达差异无统计学意义。与小鼠相似，人结膜ACE2和TMPRSS2基因表达量显著高于角膜（P=0.007），分别约为角膜上皮基因表达量的5.74倍和12.84倍。 结论： 结膜中ACE2和TMPRSS2的表达在6种检测的眼部组织中最高，提示结膜是新型冠状病毒眼部感染的主要靶组织。（中华眼科杂志，2020，56：438-446）.
Keywords: 2019-nCoV; Conjunctiva; Diabetes complications; Epithelium, corneal; Peptidyl-dipeptidase A; Serine endopeptidases.