SARS‐CoV‐2 is assumed to use angiotensin‐converting enzyme 2 (ACE2) and other auxiliary proteins for cell entry. Recent studies have described conjunctival congestion in 0.8% of patients with laboratory‐confirmed severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2), and there has been speculation that SARS‐CoV‐2 can be transmitted through the conjunctiva. However, it is currently unclear whether conjunctival epithelial cells express ACE2 and its cofactors. In this study, a total of 38 conjunctival samples from 38 patients, including 12 healthy conjunctivas, 12 melanomas, seven squamous cell carcinomas, and seven papilloma samples, were analyzed using high‐throughput RNA sequencing to assess messenger RNA (mRNA) expression of the SARS‐CoV‐2 receptor ACE2 and its cofactors including TMPRSS2, ANPEP, DPP4, and ENPEP. ACE2 protein expression was assessed in eight healthy conjunctival samples using immunohistochemistry. Our results show that the SARS‐CoV‐2 receptor ACE2 is not substantially expressed in conjunctival samples on the mRNA (median: 0.0 transcripts per million [TPM], min: 0.0 TPM, max: 1.7 TPM) and protein levels. Similar results were obtained for the transcription of other auxiliary molecules. In conclusion, this study finds no evidence for a significant expression of ACE2 and its auxiliary mediators for cell entry in conjunctival samples, making conjunctival infection with SARS‐CoV‐2 via these mediators unlikely.

中文翻译：

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COVID-19 受体 ACE2 在人类结膜中的表达。

假设 SARS-CoV-2 使用血管紧张素转换酶 2 ( ACE2 ) 和其他辅助蛋白进入细胞。最近的研究描述了 0.8% 的实验室确诊严重急性呼吸综合征冠状病毒-2 (SARS-CoV-2) 患者的结膜充血，并且有人推测 SARS-CoV-2 可以通过结膜传播。然而，目前尚不清楚结膜上皮细胞是否表达 ACE2 及其辅助因子。在这项研究中，使用高通量 RNA 测序分析了来自 38 名患者的 38 份结膜样本，包括 12 名健康结膜、12 名黑色素瘤、7 名鳞状细胞癌和 7 名乳头状瘤样本，以评估信使 RNA (mRNA) 的表达。 SARS-CoV-2 受体ACE2及其辅助因子包括TMPRSS2、ANPEP、DPP4和ENPEP。使用免疫组织化学在八个健康结膜样本中评估了 ACE2 蛋白的表达。我们的结果表明，SARS-CoV-2 受体ACE2在结膜样本中的 mRNA（中位数：每百万个转录本 [TPM]，最小值：0.0 TPM，最大值：1.7 TPM）和蛋白质水平上基本上没有表达。其他辅助分子的转录也获得了类似的结果。总之，本研究没有发现ACE2及其辅助介质在结膜样本中显着表达细胞进入的证据，因此不太可能通过这些介质感染 SARS-CoV-2 的结膜。