(A) Fetal human cardiac fibroblasts (fHCFs) (top) and adult human cardiac fibroblasts (aHCFs) (bottom) stained for vimentin (red), Ki67 (green), and 4′,6-diamidino-2-phenylindole (DAPI) (blue). (B) Quantification to show that fHCFs are smaller in size and proliferate more than aHCFs. Values are mean ± SD; *p < 0.05, Student t test. (C) Flow cytometry analysis show that aHCFs and fHCFs express THY-1 and PDGFRA but are negative for PECAM1 and CD45. Adult human coronary artery endothelial cell (aHCAEC) or THP-1 (a human monocytic cell line) were used as control cell types.