On March 21, 2024, the Massachusetts General Hospital (MGH) in the United States announced the world's first successful transplant of a genetically-edited pig kidney into a living human patient.
The four-hour surgery on March 16 has been hailed as a historic milestone for xenotransplantation which involves the transplantation of organs or tissues from one species to another.
What do we know about the procedure of pig kidney transplantation into a human?
How did the first transplant of a genetically-modified pig kidney into a living human being come together?
The patient
According to a statement by MGH, the recipient of the pig kidney is Richard Slayman, a 62-year-old African-American man living with end-stage kidney disease (ESKD). After seven years of dialysis, he had first received a kidney transplant from a human donor in December 2018. When the kidney started failing five years later, he resumed dialysis in May 2023 and was subjected to frequent hospital visits.
What about the pig?
The donor pig hasn't been accorded any special mention, like a name or something, but pigs intended as organ donors aren't just snatched off the streets or farms. Organ donor pigs are typically grown in isolation under special conditions so they're not exposed to infections capable of causing harm to the human recipient.
For the kidney Slayman received, gene-editing technology, CRISPR-Cas9, was used to remove harmful pig genes and add certain human genes so as to improve compatibility. MGH also removed virus remnants in the donor pig so it doesn't affect its human recipient.
Generally, genetically-engineered pig kidney is capable of performing all the essential functions of a normal human kidney. In total, 69 genomic edits were made on Slayman's pig kidney before it was deemed safe enough to transplant.
How was the transplant procedure performed?
According to MGH's brief of the surgery, the left kidney was transplanted into the left lower abdomen, following the standard procedure for human kidney transplantation. It wasn't smooth sailing for the team of five surgeons as Slayman's severe vascular disease was the source of some additional challenges.
"Despite this, the kidney's artery and vein were successfully connected to the recipient's artery and vein in the left lower abdomen. Subsequently, the ureter was joined to the patient's bladder," MGH announced.
How is Slayman doing?
The patient is reportedly recovering well, and will be discharged after a week of post-op observation. The success of the surgery will be defined by the absence of dialysis requirement for Slayman.
MGH will monitor his kidney function through blood and urine tests in addition to regular physical exams. The hospital will conduct twice weekly labs and clinic visits for the first month post-transplant, and weekly visits in the following month.
Can everyone take pig kidneys now?
Well, no.
The sustainability of the xenotransplantation procedure is still under observation. For example, MGH is still uncertain how many years the kidney will survive inside Slayman, but is expecting "more than two years," based on preclinical research.