Pigs can be farmed easily and grow fast, allowing for transplant of their hearts into humans. REUTERS

Pig hearts transplanted in baboons has survived for 945 days, the longest so far, raising hopes of cross-species transplants soon. Immune-suppressing drugs played a major role in the research which is expected to be used in humans soon, given the severe organ shortage.

"In our opinion, this regimen appears potentially safe for human application in patients suffering from end-stage organ failure who might be candidates for initial trials of xenotransplantation," wrote the study authors in the journal Nature Communications.

Cross-species transplantation or xenotransplantation faces a big challenge inhumans as the immune system reaction can result in rejection of the organ. To overcome this, the scientists developed a novel immune-suppressing drug regimen including an antibody, called anti-CD40 antibody that helps resist immune system response. The abboons were given this.

In addition, the pigs were genetically modified for high immune tolerance. 

The transplanted hearts from these pigs were placed in a group of five baboons to supplement the baboon heart. Both the hearts worked to pump blood.

The research conducted at the National Heart, Lung, and Blood Institute (NHLBI), saw researchers at the University of Maryland School of Medicine (UM SOM) take part.

"This has the potential to really move the field forward," said Richard Pierson, a professor of surgery at UM SOM, one of the co-authors. "This new approach clearly made a difference. We obviously have a lot more work to do, but I'm confident that eventually this will be useful to human patients."

Xenotransplants haven't lasted for longer than a few months. in 1963 a patient lived 9 months with a chimpanzee kidney and in 1984, Baby Fay survived 20 days with a baboon heart.  However, the present drug therapy could make cross species transplants a foolproof option to overcome organ shortage.

"Xenotransplants—organ transplants between different species—could potentially save thousands of lives each year that are lost due to a shortage of human organs for transplantation," study's lead author was Muhammad Mohiuddin, MD, chief of the transplantation section in the Cardiothoracic Surgery Research Program at the NHLBI told AFP. The next big test will be full pig-to-baboon heart transplants, he said.

Organ shortage
Routine removal of tissues during autopsy without informing families as well as paying for organs are some of the evolving practices to address organ shortage. In Singapore donors were being paid as much as 50,000 Singapore dollars for their organs in 2010, reported WSJ. Iran too has eliminated waiting lists for kidneys by paying its citizens to donate.

While millions suffer from kidney disease, there are only a few thousands of kidneys donated. In the U.S., over 80,000 people are on the official kidney-transplant list, a quarter of who manage to get a kidney.

While primates are closest to humans in genetic terms, the ethics of using the sensitive and intelligent animals and their endangered state prevent the use of primate organ transplants. However, the pig's organs and cells are said to be the most compatible with that of the human and pig heart valves are being increasingly used in humans.

Harvesting Islet cells from pigs for transplantation into type 1 diabetics comes with an advantage considering that if using human donors, one islet cell transplant requires more than one human pancreas to obtain the required islet cells. Chances of disease transmission too are lesser and the animals grow up fast.