Release testing for cCDCs before injection into the dog patients

Gram stain testing (77730‐1KT‐F; Sigma‐Aldrich) was used for sterility testing for the final cell therapy product. Endotoxin testing was employed (N283‐06; Lonza, Basel, Switzerland) to ensure the cCDC product was endotoxin‐free. Cell viability and morphology were verified by trypan blue before infusion. Catheter cell retention testing was performed to ensure there was minimal cell loss between cell preparation and infusion into the heart chamber.