Despite low expression in CMs, ACE2 was highly and specifically expressed in pericytes (Figure 1E). In addition, the expression of ABCC9 and PDGFRB and the absence of MYH11 help us to reaffirm the identity of the cells as pericytes instead of SMCs (Figure 1F). Different from SMCs that are located in the coronary arteries or arterioles, pericytes spread outside the endothelial cell of capillary and part of venules, which may play an essential role in myocardial micro-circulation. This result suggested that pericyte was a potential SARS-CoV-2 virus targeted host cell type in the human heart. We further screened another two related receptors of SARS-CoV, CD209, and CLEC4M. CD209 was specifically expressed in macrophage, and co-expressed with macrophage marker gene CD163, which may enhance the virus entry in the human heart (Figure 1G). CLEC4M was not enriched in human heart cells.

Northern blot analysis revealed a ≈3.4-kb ACE2 transcript expressed only in heart, kidney, and testis of 23 human tissues examined; a minor ≈8-kb band was also detected in kidney