Purpose and context. Angiotensin-converting enzyme 2 is the entry receptor for SARS-CoV and SARS-CoV-2. Variations in ACE2 expression might explain age-related symptomatology of COVID-19, that is, more gastro-intestinal symptoms and less pulmonary complaints. This study qualitatively investigated ACE2 protein expression in various organs from the fetal to the young adolescent stage. Method. Autopsy samples from lung, heart, liver, stomach, small intestine, pancreas, kidney, adrenals, and brain (when available) were obtained from twenty subjects aged 24 weeks gestational age through 28 years. Formalin-fixed paraffin-embedded 4-um-thick tissue sections were stained against ACE2. Key results. We showed that the extent of ACE2 expression is age-related. With age, expression increases in lungs and decreases in intestines. In the other examined organs, ACE2 protein expression did not change with age. In brain tissue, ACE2 was expressed in astrocytes and endothelial cells. Conclusions. Age-related ACE2 expression differences could be one substrate of the selective clinical vulnerability of the respiratory and gastro-intestinal system to SARS-CoV-2 infection during infancy.

中文翻译：

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儿童、青春期和成年早期的 ACE2 蛋白表达。

目的和背景。血管紧张素转换酶 2 是 SARS-CoV 和 SARS-CoV-2 的进入受体。ACE2 表达的变化可能解释了 COVID-19 与年龄相关的症状，即更多的胃肠道症状和更少的肺部症状。本研究定性研究了从胎儿到青春期各个器官中 ACE2 蛋白的表达。方法。来自 24 周胎龄至 28 岁的 20 名受试者的肺、心脏、肝脏、胃、小肠、胰腺、肾脏、肾上腺和脑（如果有）的尸检样本。福尔马林固定石蜡包埋的 4 um 厚组织切片针对 ACE2 进行染色。关键结果。我们发现 ACE2 表达的程度与年龄有关。随着年龄的增长，肺中的表达增加而肠中的表达减少。在其他检查的器官中，ACE2蛋白表达不随年龄变化。在脑组织中，ACE2 在星形胶质细胞和内皮细胞中表达。结论。与年龄相关的 ACE2 表达差异可能是婴儿期呼吸道和胃肠道系统对 SARS-CoV-2 感染的选择性临床易感性的原因之一。