Pigs and machines

  • The number of donors is unlikely to increase; the future lies in the transplant of transgenic and artificial hearts

“The first transgenic transplants of pig hearts in humans will take place in 1996,” the newspapers of the 90s used to say, but the 'mad cow' crisis and the spread of Aids put a stop to the idea of xenotransplants for fear that humans could be contaminated by retrovirus present in the animals. Nowadays, programmes like CRISPR-Cas9 have succeeded in eliminating the genome in pigs which are bred specificially for this.

Scientists now predict that in six or seven years a human will be able to receive a pig's heart. Juan Carlos Izpisúa is one of the Spanish scientists working on this: in Murcia they have a farm which breeds pigs in order to develop human organs. The process consists of removing the cells of the organs, leaving only their 'scaffolding', and then repopulating them with human stem cells, but new options are needed.

“In Spain about 250 hearts are grafted every year,” says Dr Lorenzo Silva, “but the demand is higher. We need three times as many donations. And those aren't going to increase much, despite the excellent work of the National Transplant Organisation (ONT), which exports its model all over the world. We are the leaders in this field.”

Fortunately, there are far fewer deaths on the roads these days, and most are from cerebrovascular accidents. The average age of a donor between 1984 and 1993 was 26 and a half, and it is now 43. Nowadays over-45s account for 57 per cent of the total, compared to the previous 7.5 per cent.

A year ago, the Navarra Clínica Universitaria hospital fitted the first complete permanent artificial heart. The patient carries an external pump in a backpack which makes two capsules work instead of the two ventricles, which propel the blood. The Spanish Cardiology Society (SEC) says this technique will equal or even surpass transplants in forthcoming years, as is happening now in the USA. Also, 3-D technology will eventually be able to construct organs in vitro with cells, biomaterials and biological molecules.

Would Juan Francisco Delgado, who had a transplant 32 years ago, accept a pig's heart? “Goodness... we'll have to see how things go, but I guess if it means you can lead a normal life... when you are in a terminal situation, like us, you're prepared to consider anything,” he says.