A study recently published in the American Journal of Transplantation evaluated whether or not transplanting the kidney of a pig could be a viable and safe options for human patients. This study was lead by Dr. Jayme Locke from the University of Alabama Birmingham.
As things stand, those who need kidney transplants often have to wait years to receive the life-changing surgery which can transform their health. They are forced to stay on dialysis, which is not a cure. The only long-lasting treatment for kidney failure is a kidney transplant. But with an organ shortage, this is not an easy feat.
Xenotransplantation, or the use of nonhuman organs for human patients, could be the key to getting all kidney patients the transplants they need.
The Study
This study involved transplanting kidneys from a pig into a 57 year old man who was brain dead. Although brain death makes a hostile environment for a new transplant, it was an opportunity to conduct the study on a person who it could not harm. Since the patient was brain dead, not all kidney function tests could be performed. Nonetheless, the researchers found overall promising results from the surgery in regards to both safety and efficacy.
The kidneys that were transplanted turned pink just as they were supposed to, indicating they had a healthy blood flow. In 23 minutes, the kidneys were producing urine. The kidneys remained functional all the way until 77 hours after the surgery had been completed and the experiment had been stopped.
The team assessed the patient for hyper acute rejection by analyzing crossmatching assays, viral transmission from donor to the patient, and surgical complications.
In the past, studies have found that the presence of carbohydrate antigens in pig blood vessels which aren’t present in humans can lead to rejection of the organ. To combat this, these vascular antigens were removed in later studies. Over time, more and more changes were made to the pigs to try to prevent rejection and cytotoxicity.
In this investigation, the donor pig had 10 genetic modifications, including 2 human anticoagulant genes, 2 human complement inhibitor genes, and 2 immunomodulatory genes. They also had deletions of a growth hormone receptor gene and 3 pig carbohydrate antigens. Serologic compatibility was assessed between the donor and the recipient prior to the surgery. Tissue compatibility was found with crossmatch testing.
The researchers were also concerned about blood pressure. Pigs have lower blood pressures than people do, and it was unclear whether or not the kidney from the pig could withstand the higher pressure in a human. The organ remained to have vascular integrity and hemodynamic stability. Cardiovascular collapse did not occur.
Further, no disease transmission from the pig occurred. Likewise, no pig cells entered human blood.
Ultimately, this study demonstrated that hyper acute rejection does not occur when the proper genetic modifications are implemented in the donor pig.
The Future
There are still many things that this research team wants to evaluate. Fist, although urine was produced, creatinine clearance, one measure of kidney function, did not improve in this study. The research team is not sure whether or not this was a result of the transplant itself or simply due to the fact that the recipient was brain dead. Additionally, microscopic blood clots occurred, and the reason for this has not yet been uncovered.
Not only is more research needed in humans, it is important to evaluate the long-term efficacy of this transplant. Over time, will the human immune response kick in against the foreign organ? Longevity is unknown. It could serve as a treatment option while patients are waiting for a human donor, or it could serve as a long-term solution in and of itself.
The next step is to obtain FDA approval and then continue this investigation in humans. The research team is hopeful that this treatment option could become a real opportunity for patients within the next 5 to 10 years.
You can read more about this novel study here.
