ABSTRACT
In this chapter, we review the morphological studies of ACE2, including its localization in tissues, and related findings. Angiotensin-converting enzyme 2 (ACE2) is a zinc metalloproteinase and transmembrane glycoprotein distributed across the plasma membrane and serves as an important regulator of the renin–angiotensin system (RAS), an important player in balancing homeostasis in the body. It is an important regulator of the RAS and plays an important role in maintaining homeostatic balance in the body. However, the recent global epidemics of SARS-CoV and SARS-CoV-2 coronaviruses and the enormous amount of research on the response to COVID-19 have revealed that the viruses not only "anchor” the host cells during membrane fusion, but also induce ACE2 receptor signaling to maintain homeostasis. The ACE2 protein is expressed in a wide variety of organs in the body, but in this study, we have demonstrated the localization of positive cells stained by ACE2 immunohistochemistry in liver, kidney, alveolar tissue, pancreas, colon, oral mucosa, and salivary gland. In this chapter, the localization of cells stained positive by ACE2 immunohistochemistry in liver, kidney, alveolar tissue, pancreas, colon, oral mucosa, and salivary gland is presented, and a review of the observations and disease associations reported to date is given. © 2023 Elsevier Inc. All rights reserved.
ABSTRACT
Coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China, in December 2019 as an out-break of pneumonia of unknown origin. Previous studies have suggested the utility of chest computed tomography (CT) in the diagnosis of COVID-19 because of its high sensitivity (93%-97%), relatively simple procedure, and rapid test results. This study, performed in Japan early in the epidemic when COV1D-19 prevalence was low, evaluated the diagnostic accuracy of chest CT in a population present-ing with lung diseases having CT findings similar to those of COVID-19. We retrospectively included all consecutive patients (18 years old) presenting to the outpatient department of Keio University Hospital between March 1 and May 31, 2020, with fever and respiratory symptoms. We evaluated the perfor-mance of diagnostic CT for COVID-19 by using polymerase chain reaction (PCR) results as the refer-ence standard. We determined the numbers of false-positive (FP) results and assessed the clinical utility using decision curve analysis. Of the 175 patients, 22 were PCR-positive. CT had a sensitivity of 68% and a specificity of 57%. Patients with FP results on CT diagnosis were mainly diagnosed with diseases mimicking COVID-19, e.g., interstitial lung disease. Decision curve analysis indicated that the clinical utility of CT imaging was limited. The diagnostic performance of CT for COVID-19 was inadequate in an area with low COV ID-19 prevalence and a high prevalence of other lung diseases with chest CT findings similar to those of COVID-19. Considering this insufficient diagnostic performance, CT findings should be evaluated in the context of additional medical information to diagnose COVID-19.
ABSTRACT
We evaluated localization of angiotensin-converting enzyme 2 (ACE2), the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in the salivary and associated tissues using immunohistochemistry. Fifty paraffin-embedded blocks from 48 anonymized patients, biopsied or operated on for diseases of the oral and maxillofacial region before 2010, were analyzed. ACE2-expressing cells were observed in the parotid, sublingual and the buccal glands, the conduits, the acinar regions of the serous glands, and sparsely in the mucous glands. Scattered ACE2-positive endothelial cells were also observed in nearby capillaries nourishing the salivary glands, as well as in the juxta-epithelial capillaries of the oral mucosa. ACE-2-positive adipocytes were scattered within the stroma of the parotid gland. These observations suggest the possibility that SARS-CoV-2 may travel through the bloodstream to the capillaries that nourish the salivary glands and oral mucosa, and inducing vasculitis and damage of oral tissues. SARS-CoV-2 infection of salivary glands through the bloodstream implies the main cause of salivary contamination. Similarly, ascending infection from oral fluid to the salivary gland conduit has been shown to be another possible mute. Moreover, infection of ACE2-positive parotid adipocytes may lead to parotid glands inflammation and contribute to systemic progression of coronavirus disease 2019.