key: cord-1010047-8a3bpa4k authors: Zhang, Hui; Li, Hong-Bao; Lyu, Jian-Rui; Lei, Xiao-Ming; Li, Wei; Wu, Gang; Lyu, Jun; Dai, Zhi-Ming title: Specific ACE2 Expression in Small Intestinal Enterocytes may Cause Gastrointestinal Symptoms and Injury after 2019-nCoV Infection date: 2020-04-18 journal: International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases DOI: 10.1016/j.ijid.2020.04.027 sha: ecfc7e03c5ae929185123b1e77b8a9316e3ad728 doc_id: 1010047 cord_uid: 8a3bpa4k Abstract The coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China and rapidly spread in other countries in December 2019. The infected patients presented with fever, respiratory symptoms, sometimes with digestive and other systemic manifestations, and some progressed with a severe acute respiratory syndrome or even death. Associated digestive symptoms were frequently observed in the patients, with an unknown significance and mechanism. ACE2, as the major known functional receptor of the 2019 novel coronavirus (2019-nCoV) attracted our attention. We collected the clinical data of the 2019-nCoV-infected patients from published studies and extracted the data about the incidence of gastrointestinal symptoms. Furthermore, we used online datasets to analyze ACE2 expression in different human organs, especially in the small intestine, to explore the relationship between ACE2 expression patterns and clinical symptoms. We found that diarrhea accounted for a notable proportion of COVID-19 patients, ranging from 8.0% to 12.9%. The results reveal that ACE2 mRNA and protein are highly expressed in the small intestinal enterocytes but not in the goblet cells or intestinal immune cells. High expression of ACE2 on the surface cells in the digestive tract may lead to gastrointestinal symptoms and inflammation susceptibility. Overall, digestive symptoms were common in the COVID-19 patients. ACE2 expression on surface cells of the small intestine may mediate the invasion and amplification of the virus and activation of gastrointestinal inflammation. It is a possible mechanism of digestive symptoms in the COVID-19 patients and explains the presence of the virus in patients’ stool samples. The study also highlights the necessity of taking stool samples for suspected patients to help in early diagnosis and assessment of disease status. Coronavirus Disease 2019 (COVID- 19) , which was first reported in Wuhan, China during December 2019, is a newly emerged viral infection caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), also known as the 2019 novel coronavirus (2019-nCoV) (1) . This disease is characterized by fever, dry cough, fatigue and lymphopenia, which can also lead to gastrointestinal symptoms, organ dysfunction, rapid progression to a severe acute respiratory syndrome and even death (2, 3) . The 2019-nCoV has the same cell entry receptor as the SARS-CoV, the angiotensin converting enzyme 2 (ACE2), which regulates the cross-species and human-to-human transmissions of the SARS-CoV (5) (6) (7) (8) . ACE2 belongs to the ACE family of dipeptidyl carboxy-dipeptidases and plays a critical role in the RAS systems and in some organs (9) . It is distributed broadly in the arterial and the venous endothelial cells, the arterial smooth muscle cells and the cholangiocytes, and especially highly expressed in the renal, the cardiovascular, and the gastrointestinal tissues. This indicates that COVID-19 may involve multiple organs, which may also explain the various extrapulmonary symptoms (10) . Although COVID-19 is characterized by fever and respiratory tract manifestations, data from recent studies suggest that concurrent gastrointestinal symptoms are not J o u r n a l P r e -p r o o f uncommon (11) . Moreover, it has been reported that the SARS-CoV exhibits an intestinal tropism (12) . It is possible that the 2019-nCoV had the same tissue tropism as that of the SARS-CoV, as they had the same functional cell receptor (5) . Several studies have found the surface expression pattern of the ACE2 protein in enterocytes of the small intestine, mainly on cells in contact with the external environment. ACE2 is mainly expressed in the endothelium and the vascular smooth muscle cells in the colon (8, 13, 14) . ACE2 expressed on surface cells of the small intestine is a potential primary entrance for the 2019-nCoV to infect the host and cause gastrointestinal symptoms. This study aimed to determine the expression pattern of ACE2 gene in the small intestine and attempted to determine the potential mechanism of diarrhea and other gastrointestinal manifestations in patients with COVID-19. Meanwhile, the distribution pattern of ACE2 may insinuate a fecal-oral transmission for the COVID-19. A high virus titer in the digestive tract may indicate a high risk of transmission via feces of the patients, which raises new problems in the disposal of feces. We summarized the clinical data of four recent studies involving clinical characteristics of the COVID-19 to extract the incidence of gastrointestinal symptoms in patients infected with the 2019-nCoV (3, (15) (16) (17) . Recorded information included the demographic data and the gastrointestinal symptoms during the whole disease process including anorexia, nausea or vomiting, diarrhea, and abdominal pain. All clinical information was directly obtained from the articles cited above. We used RNA and protein expression data of the ACE2 gene in different human tissues through the Human Protein Atlas portal (http://www.proteinatlas.org/) (18) . All data are available online. Gene expression matrix and cell type annotation of single cell RNA-seq (scRNA-seq) data from biopsies of the human terminal ileum across 13 children diagnosed with functional gastrointestinal disease (without inflammation) and J o u r n a l P r e -p r o o f ranging in age 6-18 years old. Different cell types were identified by mapping the canonical marker genes in the two-dimensional t-distributed stochastic neighbor embedding (tSNE) map. The TOP principle components were used to project the data using tSNE. Cell labels were used for cell-type annotations. The visualisation results were obtained from the scRNA-seq Single Cell Portal (https://singlecell.broadinstitute.org/single_cell) and the data was uploaded by Ziegler et al. (19) . We analyzed data from the 4 most recent studies focused on the clinical features of COVID-19 patients (Table 1 ). In these 4 cohort studies, the number of confirmed Information about some individual samples has been listed in Table 2 from The Human Protein Atlas, including sex, age and estimated fractions of cell types. were believed to get infected as a result of the unscientific drainage system, which indicated that there were possibilities that virus transmit by a fecal-oral way. We should be wary of the coming warmer seasons, which is also the season when digestive infectious diseases happened with higher incidence, the 2019-nCoV could spread again. ACE2 is identified as an enzyme that negatively regulates the RAS by converting Ang II and the main bioactive molecule of the RAS. In addition, ACE2 is essential for neutral amino acid transporters in the gut (9, 22) . A study showed that amino acid malnutrition is related to an intestinal inflammation via ACE2, which plays a significant role in amino acid homeostasis, innate immunity, and maintaining intestinal microbiota The authors declare no conflict of interest. This research received no external funding. No ethical approval was obtained because this study did not involve a clinical evaluation, did not involve laboratory animals and invasive procedures. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. 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