ACE2 and viral infectious disease: Recently, multiple studies showed different tissue organoids (intestinal organoids, human blood vessel, human kidney, prostate, retina, brain, and lung organoids) could be used as in vitro organ systems to mimic the SARS-CoV-2 viral infection, pathogenesis, and ACE2 expression, and were studied for therapeutic effects (drugs, proteins, or nucleic acid therapeutics) [133,134,135].