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This Little Piggy Went to Market

By Michael Cook

Gene editing promises to enable the safe use of pig organs to transplant into humans. Who could object to that?

The invention of the powerful gene-editing technique CRISPR is a game-changer for genetic engineering, making the removal or insertion of DNA sequences relatively easy and inexpensive. The key paper outlining how it works was published in 2012, but already scientists are eagerly exploiting its therapeutic and commercial potential, from modifying yeast cells to human embryos.

The latest announcement is the most exciting yet. Harvard scientists led by George Church reported in Science that they had removed 62 locations in the DNA of pig embryos that contained the porcine endogenous retrovirus (PERV). Technically this was a tour de force, the largest number of sites modified at the same time using CRISPR.

The danger of infection with PERV has made it impossible to consider using pig organs to replace human organs. Now it seems within reach.

Furthermore, Church says that his team has also modified more than 20 genes that cause immune rejection or blood clotting in humans in a different set of pig embryos.

Church is nearly ready to implant the modified pig embryos into surrogate sows. “This is something I’ve been wanting to do for almost a decade,” he told Nature. A Boston biotech company that he has co-founded, eGenesis, is gearing up to produce the genetically engineered pigs as cheaply as possible.

This could become a very lucrative business. Of the 120,000 people who require organ transplants every year in the US, only 30,000 receive them. Church’s genetically engineered pigs, however, could supply kidneys and other organs. “This work brings us closer to a realization of a limitless supply of safe, dependable pig organs for transplant,” a transplantation expert told the New York Times.

All of this sounds tremendously promising, but are there any ethical problems? There have been several studies of the ethics of xenotransplantation (i.e. transplants from other species) over the past 20 years or so, precisely because pigs have always seemed to be ideal sources of organs. There can be little objection as long as the risks of immune rejection and infection by pig viruses can be eliminated.

But we should expect a backlash from animal rights groups. In the past they have raised a number of objections to xenotransplants. The British Union for the Abolition of Vivisection told the Nuffield Council on Bioethics in the UK back in 1996: “The use of healthy animals as a source of ‘spare parts’

for humans represents a fundamental denial of the inherent value of those animals’ lives.” And a group called the Genetics Forum wrote: “The use of animals as sources of cells, tissues and organs for humans causes us much concern. It encourages the concept of animals as ‘pharm’ factories and reinforces the ethos that they merely exist in order to satisfy human needs.”

If animal welfare groups have expressed their bitter opposition to intensive farming of pigs for bacon, they will surely object to mass production for their kidneys.

The conditions under which the pigs are kept could pose problems. They might have to be kept in isolation to keep them sterile and healthy. Pigs are social animals, so isolation and sensory deprivation could be harmful. Constant monitoring might lead to stress.

This raises an interesting problem for politicians. Faced with the dire shortage of organs, the public is bound to take a species-centric view of animal welfare: the interests of sick humans far outweigh the interests of pigs.

In recent years the notion that there is no convincing reason why a bright moral line should be drawn between humans and other animals has been steadily gaining ground. If Church’s techniques are successful, the animal rights movement could be set back by decades.

Scientists should also anticipate religious objections. Some Christians believe that animals should only be used for “natural” purposes. While it may be natural to eat pigs, it may not be natural to use their organs. Jains believe that all exploitation of animal life is wrong. A Muslim group told the Nuffield Council that pigs and other prohibited animals were not acceptable as transplant sources.

In the optimistic news stories that followed the unveiling of Church’s results, almost nothing was said about animal welfare and animal rights. Entrepreneurial scientists ignore this aspect at their peril.

Michael Cook is editor of BioEdge, an online bioethics newsletter.