We have applied a good manufacturing practices-compliant standard operating procedure previously employed for derivation of pericytes from human saphenous vein.16 (link) CPs were isolated from atrium or ventricle specimens (3 to 5 mm, <100 mg) from infants and children undergoing surgical repair for congenital heart defects. In brief, discarded tissue was thoroughly washed in PBS and then manually minced. The tissue suspension was incubated for 40 minutes with 0.45 WU/mL/g Liberase 2 (Roche Technologies, UK). Passing the cell suspension sequentially through 70, 40, and 30-μm cell strainers ensured single cell suspension. Cells were depleted for ECs with anti-CD31 conjugated beads (Miltenyi Biotech, UK), following the manufacturer’s instructions. The remaining cells were purified by selecting CD34+ cells by anti-CD34 beads (Miltenyi Biotech). Target cells were cultured in the presence of EGM2 medium (Lonza, UK) supplemented with 2% fetal bovine serum (FBS). Adherent colonies were passaged to new culture dishes once they reached 60% to 70% confluence and frozen stocks were generated after Passage 2 for the experiments shown in this study. Trypsin-EDTA (Life Technologies, UK) was utilized to detach cells from the growth substrate.