(A) Contrast-phase and immunofluorescence images showing the characteristic shape and antigenic phenotype of cultured cardiac PCs. In green fluorescence, the antigens as indicated. In blue nuclei (DAPI), NG2: Neural/glial antigen 2. PDGFRα: platelet derived growth factor receptor α. (B) Immunofluorescence images of human cardiac fibroblasts and CAECs employed as negative or positive controls for markers in (A). (C) Expression of ACE2 (green) and TMPRSS2 (red) in cardiac PCs and control cells assessed by immunostaining. In blue nuclei (DAPI). Calu-3: human lung epithelial cell line. VeroE6/ACE2/TMPRSS2: African green monkey kidney cell line engineered to overexpress the human ACE2 and TMPRSS2. (D) Expression of ACE2 and TMPRSS2 assessed using Western blotting. n=5 patients’ PCs, n=1 for cell lines. (E) Expression of CD147 (green) in cardiac PCs and control human CAECs assessed by immunostaining. In blue nuclei (DAPI). (F) Expression of CD147 and ACE2 determined using Western blotting. n=5 patients’ PCs. n=2 CAEC. siBSG = PC in which BSG (CD147) was silenced, used as a negative control for CD147.