We seem to have a fair way to go before genetically modified pig hearts can be used in humans on any large scale. Human hearts grown from the patient’s own stem cells would be a better alternative, circumventing the serious twin problems of rejection and immunosuppressive drugs, but a fiendishly complex endeavour. One interim measure is to implant cardiac muscle cells derived from stem cells into failing hearts. A German group has achieved this in a human patient and in monkeys:
https://www.nature.com/articles/d41586-025-00273-2
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