Doctors say they can boost the odds donated organs will be usable by restarting blood circulation with a pump after donors are declared dead. Critics say the procedure blurs the definition of death.

Surgeons transplanted a kidney and thymus gland from a gene-edited pig into a 54-year-old woman in an attempt to extend her life. It's the latest experimental use of animal organs in humans.

Scientists are optimistic that gene-edited animals could provide a new source of organs for transplantation. Pig organs modified to minimize rejection are now being tested in humans.

After six weeks on a ventilator, she was dying of COVID-19. But doctors took a gamble and gave Mayra Ramirez a double lung transplant. Now she shares what it's like to come back from the brink.