Organ Transplants from Pigs Closer Due to Virus Removing Gene Editing

Wednesday 23rd August 2017

In a massive step forward for gene research and helping alleviate the increasing demand for organ transplants, gene editing to cut out harmful infectious genes has successfully been used to remove retroviruses from pig cells, leading to the potential of using pig organs in the future for organ transplants.

Pigs are interesting among animals in that many of their internal organs are surprisingly similar to human organs, despite being different sizes or shapes. This is true to the point that they can be potentially used as organ donations. The main practical barrier to this is that many pigs carry porcine endogenous retroviruses (PERVs).

Retroviruses are particularly problematic because they have the ability to cause some cancers and immunodeficiency illnesses, including HIV (human immunodeficiency virus). This basically has rendered using pig organs unsafe by themselves.

Researchers from eGenesis Inc in the US, Zhejiang University in China, and a number of other institutions on Denmark, the US and China created a study looking into the possibility of removing retroviruses from pig cells and whether healthy retrovirus-free piglets could be born as a result.

The results first showed that PERVs could be transferred to human cells, integrate into human DNA and spread like human viruses. The next step was using a technique called CRISPR gene editing to remove every copy of the porcine retroviruses from the pig cells, and thus eliminated transmission of the virus to the human embryo cells. Finally, they used the same technique to remove all retroviruses from the pig cells and created pig embryos that were also born from surrogate sows and are confirmed to have a normal DNA structure free of the retrovirus.

For the purpose of xenotransplantation (transplanting non-human organs into human bodies), this is a very interesting first step, but given that the study hasn’t even confirmed that the piglets can survive a full natural life yet this is obviously far too early to consider human organs a realistic prospect.

A minor point is that the uncertainty into how PERVs work in reality. We do not know if pig retroviruses can transfer to humans in how they will affect us outside of tests in the lab.

While it should be noted that pig tissues have been used in medicine for decades for uses such as insulin and the use of pig heart valves as part of complicated heart surgery, transplanting whole organs and the process into which pigs are born, reared and ultimately harvested for organs would create a whole new swathe of ethical, practical and safety issues.

There is the complications surrounding genetic modification to begin with, then there is the contentious issue of animal testing and using animals as organ donors, contrasted with the shortage of human organs for transplantation.

Right now, the practicalities of using xenotransplantation is many years away, but this is an interesting experiment and has the potential in the future to save lives, either directly or through the gene-editing techniques used.