ACE2 and TMPRSS2 were both expressed in normal conjunctival epithelium, epithelial cells in conjunctivapapilloma and conjunctival nevus, and cells in conjunctivacyst wall.ACE2 was mainly distributed in the superficial and intermediate cells of conjunctival epithelium, but not in the basal cells and goblet cells.TMPRSS2 was found in different layers of cells.The positive expression rates of ACE2 and TMPRSS2 in conjunctiva were both 100%.There was no significant difference in the expression intensity of ACE2 and TMPRSS2 among normal conjunctival tissue, conjunctival papilloma, conjunctival nevus and conjunctival cyst (all at P>0.05). Weakly expressed in corneal tissues, ACE2 and TMPRSS2 were more moderately and strongly expressed in conjunctival tissues.There were significant differences in the number of differently graded ACE2 and TMPRSS2 expression between normal conjunctival tissues, conjunctival papilloma, conjunctival nevus, conjunctival cyst and corneal tissues (ACE2 Z=-3.473, -4.183, -3.970, -3.873, all at P<0.01; TMPRSS2 Z=-4.119, -4.472, -4.443, -4.147, all at P<0.001).
Conclusions:
COVID-19 transmission-related receptors ACE2 and TMPRSS2 are expressed in human conjunctival tissue, which provides organological evidence for ocular surface transmission of COVID-19.