Research ArticlesAngiotensin-converting Enzyme-2 (ACE2) Expression in Pediatric Liver DiseaseStevens, James P. MD*,†; Kolachala, Vasantha L. PhD*; Joshi, Gaurav N. PhD‡; Nagpal, Sini PhD§; Gibson, Greg PhD§; Gupta, Nitika A. MD, DCH, DNB, MRCPCH*,† Author Information *Department of Pediatrics, Emory University School of Medicine †Transplant Services, Children’s Healthcare of Atlanta ‡Integrated Cellular Imaging (ICI) Core, Emory University §School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA Supported by Emory Center for Transplantation and Immune-Mediated Disorders (CTID) and by the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) foundation (for N.A.G.). The authors declare no conflict of interest. Reprints: Nitika A. Gupta, MD, DCH, DNB, MRCPCH, 1760 Haygood Drive, Atlanta, GA 30322 (e-mail: [email protected]). Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website, www.appliedimmunohist.com. Applied Immunohistochemistry & Molecular Morphology: November/December 2022 - Volume 30 - Issue 10 - p 647-653 doi: 10.1097/PAI.0000000000001068 Buy SDC Metrics Abstract The membrane protein angiotensin-converting enzyme-2 (ACE2) has gained notoriety as the receptor for severe acute respiratory syndrome coronavirus 2. Prior evidence has shown ACE2 is expressed within the liver but its function has not been fully discerned. Here, we utilized novel methodology to assess ACE2 expression in pediatric immune-mediated liver disease to better understand its presence in liver diseases and its role during infections such as COVID-19. We stained liver tissue with ACE2-specific immunofluorescent antibodies, analyzed via confocal microscopy. Computational deep learning-based segmentation models identified nuclei and cells, allowing the quantification of mean cellular and cytosolic immunofluorescent. Spatial transcriptomics provided high-throughput gene expression analysis in tissue to determine cellular composition for ACE2 expression. ACE2 plasma expression was quantified via enzyme-linked immunosorbent assay. High ACE2 expression was seen at the apical surface of cholangiocytes, with lower expression within hepatocyte cytosol and nonparenchymal cells (P<0.001). Children with liver disease had higher ACE2 hepatic expression than pediatric control tissue (P<0.001). Adult control tissue had higher expression than pediatric control (P<0.001). Plasma ACE2 was not found to be statistically different between samples. Spatial transcriptomics identified cell composition of ACE2-expressing spots containing antibody-secreting cells. Our results show ACE2 expression throughout the liver, with strongest localization to cholangiocyte membranes. Machine learning can be used to rapidly identify hepatic cellular components for histologic analysis. ACE2 expression in the liver may be increased in pediatric liver disease. Future work is needed to better understand the role of ACE2 in chronic disease and acute infections. Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.