Expression of Ace2, Tmprss2, and Furin in mouse ear tissue

Uranaka, Tsukasa; Kashio, Akinori; Ueha, Rumi; Sato, Taku; Bing, Han; Ying, Gao; Kinoshita, Makoto; Kondo, Kenji; Yamasoba, Tatsuya

Objectives Intracellular entry of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) depends on the interaction between its spike protein to a cellular receptor named angiotensin-converting enzyme 2 (ACE2) and depends on Furin-mediated spike 23 protein cleavage and spike protein priming by host cell proteases including 24 transmembrane protease serine 2 (TMPRSS2). Tmprss1, Tmprss3, and Tmprss5 are expressed in the spiral ganglion neurons and the organ of Corti in the inner ear; however, Ace2, Tmprss2, and Furin expression profiles in the middle ear remain unclear. Therefore, this study aimed to analyze Ace2, Tmprss2, and Furin expression in the middle and inner ear of mice. Study Design Animal research. Setting Department of Otolaryngology and Head and Neck Surgery, University of Tokyo. Methods We performed immunohistochemical analysis to examine the distribution of Ace2, Tmprss2, and Furin in the eustachian tube, middle ear space, and cochlea of mice. Results Ace2 was expressed in the cytoplasm in the middle ear epithelium, eustachian tube epithelium, stria vascularis, and spiral ganglion. Tmprss2 and Furin were widely expressed in the middle ear spaces and the cochlea. Conclusion Co-expression of Ace2, Tmprss2, and Furin in the middle ear indicates that the middle ear is susceptible to SARS-CoV-2 infections, thus warranting the use of personal protective equipment during mastoidectomy for coronavirus disease (COVID-19) patients.