Coronavirus disease 2019 (COVID-19) has become a significant global public health problem. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which causes the disease, utilizes angiotensin-converting enzyme II (ACE2) as a major functional receptor to enter host cells. No study has systematically assessed ACE2 expression in multiple tissues in children. This study investigated ACE2 expression and ACE2 protein's histological distribution in various organs in paediatric patients (the small intestine, thymus, heart and lungs). Our study revealed that ACE2 was highly expressed in enterocytes of the small intestine and widely expressed in the myocardium of heart tissues. The most notable finding was the positive staining of ACE2 in the Hassall's corpuscles epithelial cells. Negligible ACE2 expression in the lung tissues may contribute to a lower risk of infection and fewer symptoms of pneumonia in children than in adults with COVID-19 infection. These findings provide initial evidence for understanding SARS-CoV-2 pathogenesis and prevention strategies in paediatric clinical practice, which should be applicable for all children worldwide.

中文翻译：

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儿童中 SARS-CoV-2 细胞受体基因 ACE2 的组织表达。

2019 年冠状病毒病（COVID-19）已成为一个重大的全球公共卫生问题。导致该疾病的严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 利用血管紧张素转换酶 II (ACE2) 作为主要功能受体进入宿主细胞。尚无研究系统评估儿童多个组织中 ACE2 的表达。本研究调查了儿科患者各个器官（小肠、胸腺、心脏和肺）中 ACE2 的表达和 ACE2 蛋白的组织学分布。我们的研究表明，ACE2在小肠的肠上皮细胞中高表达，并在心脏组织的心肌中广泛表达。最值得注意的发现是哈萨尔小体上皮细胞中 ACE2 的阳性染色。与感染 COVID-19 的成人相比，肺组织中 ACE2 的表达可忽略不计，可能导致儿童感染风险降低，肺炎症状减少。这些发现为了解 SARS-CoV-2 发病机制和儿科临床实践中的预防策略提供了初步证据，应适用于全世界所有儿童。