ACE2 and COVID-19: Because ACE2 is widely expressed in human tissues (Hamming et al., 2004; Ni et al., 2020; Beyerstedt et al., 2021), the potential effects of lower or higher ACE2 expression may occur within other tissues, possibly influencing COVID-19 symptoms, considering that it infects such important tissues to maintain homeostasis (Wu et al., 2020; Gasmi et al., 2021).