Batlle et al. have also suggested whether the expression of other cellular TMPRSSs other than TMPRSS2 (such as TMPRSS 4, 5 or 9) may also play a role in the priming step [64]. Studies showed that the co-expression of the ACE-2 receptor and TMPRSS genes in kidney epithelial cells was as significant as in the lung, esophagus, small intestine and colon, suggesting that the kidney might also be an important target organ for SARS-CoV-2 [63]. In particular, a high co-expression of ACE-2 and TMPRSS genes was found in podocytes and proximal rectangular tubular cells [63].