An abnormality was detected in a pig heart transplanted into a human patient, the press service of the American Heart Association reported.
In January, a heart from a genetically modified pig was first successfully transplanted into a 57-year-old man with a life-threatening disease. However, a few months later, the American died, and it was reported that there was a virus in the new heart.
Xenotransplantation had long been hindered by the fact that the immune system rejected foreign tissue. Biologists solved the problem when they adapted the CRISPR/Cas9 genomic editor to remove the genes responsible for the "our-foreign" system.
By doing so, the researchers were able to transplant a pig's heart first into a baboon's body and then into the chest of 57-year-old David Bennett. Initially, the team found no problems with the implanted heart, but two months after the surgery, the man died unexpectedly. This sparked controversy around the safety of xenotransplantation.
Scientists had been trying to figure out the causes of the patient's death for a long time, and repeatedly analyzed his lifetime cardiograms. The comparison uncovered abnormalities in the implanted heart's cardiorhythms that had escaped the scientists' attention at the time of the surgery.
The team found that three key parameters were significantly higher in the transplanted heart than similar values found not only in healthy pig organs but also in humans. They remained abnormally high for two months after surgery, suggesting serious malfunctions in the cellular systems responsible for transmitting electrical signals within the heart.