The invention of a powerful gene-editing technique called CRISPR is a game-changer for genetic engineering. It makes removing or inserting DNA sequences quick, easy and inexpensive. The key paper outlining how it works was published only a couple of years ago, in 2012, but already scientists are exploiting its therapeutic and commercial potential, from modifying yeast cells to human embryos.
The latest announcement is the most exciting yet because it could save thousands of lives. Harvard scientists led by George Church reported in the journal Science that they had removed 62 locations in the DNA of pig embryos which 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 PERVs has made it impossible to consider using pig organs as replacements for human organs. Now this seems within reach.
Furthermore, Church says that his team has also modified more than 20 genes which cause immune rejection or blood clotting in humans in a different set of pig embryos. (These results have not been published yet.)
He 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 cheap as possible.
This could become a very lucrative business.
Pigs are probably the best source of organs. They are about the size of human beings; they have large litters; they mature quickly; their biology is well-known; and they are easy to raise. Baboons are another possible source and they are genetically more like humans, but they are harder to raise and reproduce more slowly.
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.
There is a certain amount of hype in Church’s announcement. While he has a stellar research record, he is not exactly publicity-shy. In the past he has advocated designer babies, and worked on the revival of woolly mammoths. In his book Regenesis: How Synthetic Biology Will Reinvent Nature and Ourselves, he even discussed the possibility of creating Neanderthals from ancient DNA. “If society becomes comfortable with cloning and sees value in true human diversity, then the whole Neanderthal creature itself could be cloned by a surrogate mother chimp—or by an extremely adventurous female human.”
Nonetheless, pig organs do sound tremendously promising.
But are there any ethical problems? There have been several studies of the ethics of xeno-transplantation (ie, tranplants from other species) over the past 20 or so years, 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 that “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 and isolation and sensory deprivation could be harmful. Constant monitoring might lead to stress.
This will create a problem for animal rights activists. Faced with the dire shortage of organs, the public is bound to take a strongly speciesist view of animal welfare: that 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 spiritually-minded people believe that animals should only be used for “natural” purposes — and 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 which 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 MercatorNet.