ACE2 immunohistochemistry in salivary and tracheal glands related to age

OBJECTIVE: SARS-CoV-2 is the cause of COVID-19, the rapidly spreading pandemic. When SARS-CoV-2 enters the target cells in the respiratory system, the spike glycoprotein binds to a cellular receptor angiotensin converting enzyme 2 (ACE2). The susceptibility to infection in individuals under 20 years of age is approximately half that of adults aged over 20 years. In this study, we investigated the immunohistochemical protein expressions of ACE2 in mandibular salivary glands and tracheal glands from forensic autopsy specimens covering adults and children. RESULTS: The ACE2 immunohistochemistry of autopsy specimens was performed, and the percentages of the immuno-positive areas in the cell layers of the glands were calculated. Our results demonstrate that the ACE2 positivity in mandibular salivary gland and tracheal glands showed the statistically significant decrease with the increase of age, which indicates that the susceptibility of aged individuals to SARS-CoV-2 may be due to various factors including but not limited to ACE2 protein expressions.