PECAM1 and infection: In addition to those electron microscopic analyses, Monteil et al. provided in situ evidence for the infection and replication of SARS-CoV-2 in endothelial cells by using engineered human capillary organoids with CD31+ endothelial lining established from induced pluripotent stem cells; quantitative real-time PCR analysis showed that SARS-CoV-2 RNA increased from day 3 to day 6 after primary SARS-CoV-2 exposure to the capillary organoids, indicating the infection and replication of SARS-CoV-2 in endothelial cells [36].