Scientists have taken a step toward making pig organs suitable for human transplant, using the much heralded CRISPR-Cas9 gene editing technique.
Using live cells or tissues from other animals in humans is called xenotransplantation. Pig organs are just about the same size as human organs, leading some doctors to think they could be an option for solving a shortage of human donors. On its page about xenotransplantation, the U.S. Food and Drug Administration points out, “Currently ten patients die each day in the United States while on the waiting list to receive lifesaving vital organ transplants. Moreover, recent evidence has suggested that transplantation of cells and tissues may be therapeutic for certain diseases such as neurodegenerative disorders and diabetes, where, again human materials are not usually available.”
However, one concern regarding pig organs in particular is that genetic remnants of long-gone pig infections could reactivate from the pig DNA and affect human recipients.
The FDA details this threat too:
Although the potential benefits are considerable, the use of xenotransplantation raises concerns regarding the potential infection of recipients with both recognized and unrecognized infectious agents and the possible subsequent transmission to their close contacts and into the general human population. Of public health concern is the potential for cross-species infection by retroviruses, which may be latent and lead to disease years after infection. Moreover, new infectious agents may not be readily identifiable with current techniques.
The potentially problematic parts of the pig genome are known as porcine endogenous retroviruses (PERVs).
That’s where CRISPR-Cas9 comes into the picture.
Scientists used the gene editing tool to identify and disable the viral pieces of DNA in the pig genome. The edited DNA was inserted into pig eggs, replacing the existing genetic material. The resulting embryos successfully developed into healthy pigs that lacked the 25 identified PERVs.
To be clear, patients with diabetes have already received pig pancreatic cells as part of their treatment, and burn victims have taken pig skin grafts without the PERVs causing any issues. Porcine heart valves have been used in surgeries for over 40 years. However, shutting off the potential threat for good could accelerate the use of pig organs in people.
Researchers working on the PERV removal project hope that aggressively seeking out and addressing potential problems will move the field closer to transferring organs between species. They plan to next use gene editing to make pigs that are even more immunologically similar to humans, further reducing the likelihood the organs will be rejected after transplantation.
To schedule a media interview with Dr. Neil Lamb or to invite him to speak at an event or conference, please contact Margetta Thomas by email at mthomas@hudsonalpha.org or by phone: Office (256) 327-0425 | Cell (256) 937-8210
Reference: Niu D. et al. Inactivation of porcine endogenous retrovirus in pigs using CRISPR-Cas9. Science (2017) eaan4187. doi:10.1126/science.aan4187
