Kidneys from pigs which had been genetically modified have been transplanted into two people without the recipients’ immune systems immediately rejecting them for the first time.
Researchers from New York University (NYU) were given permission to transplant kidneys from pigs, which had been modified to have human-like immune systems, into two patients who had suffered the irreversible loss of all brain function.
Alongside the kidneys, the researchers also transplanted a pig thymus which produces immune cells and helps the body to accept the foreign organs.
The patients’ own kidneys remained in place and the pig kidneys were grafted onto the veins and arteries carrying blood to and from the recipients’ legs.
The researchers monitored the kidneys’ function and the patients’ immune responses for 54 hours – in line with the limit imposed by NYU’s ethics board.
The procedures were carried out towards the end of last year and the researchers published their findings in The New England Journal of Medicine this May.
In the report of their findings, the researchers said: “Xenografts from genetically modified pigs have become one of the most promising solutions to the dearth of human organs available for transplantation.
“The challenge in this model has been hyperacute rejection. To avoid this, pigs have been bred with a knockout of the alpha-1,3-galactosyltransferase gene and with subcapsular autologous thymic tissue.
“The xenograft in both recipients began to make urine within moments after reperfusion. Over the 54-hour study, the kinetic eGFR increased from 23 ml per minute per 1.73 m2 of body-surface area before transplantation to 62 ml per minute per 1.73 m2 after transplantation in Recipient 1 and from 55 to 109 ml per minute per 1.73 m2 in Recipient 2.
“In both recipients, the creatinine level, which had been at a steady state, decreased after implantation of the xenograft, from 1.97 to 0.82 mg per deciliter in Recipient 1 and from 1.10 to 0.57 mg per deciliter in Recipient 2.
“The transplanted kidneys remained pink and well-perfused, continuing to make urine throughout the study. Biopsies that were performed at six, 24, 48, and 54 hours revealed no signs of hyperacute or antibody-mediated rejection. Hourly urine output with the xenograft was more than double the output with the native kidneys.”
They concluded: “Genetically modified kidney xenografts from pigs remained viable and functioning in brain-dead human recipients for 54 hours, without signs of hyperacute rejection.”
