Pigs have been bred with cystic fibrosis, providing scientists with a powerful animal model that will aid the development of new treatments for the incurable condition.

The creation of the pigs, using genetic engineering and cloning technologies, removes one of the biggest barriers to research into cystic fibrosis.

While mice and other animals have previously been modified with the genetic mutation that causes the inherited disorder, they do not develop the same symptoms as humans and are thus useless for most experiments. As a result, scientists have had few tools for investigation short of testing new treatments on people with the disease.

“Right now, if you want to do experiments to find treatments or therapies for the lung disease that is fatal for people with cystic fibrosis, you would have to experiment on kids that have cystic fibrosis,” said Randy Prather, Professor of Reproductive Biology at the University of Missouri, a leader of the research team that bred the pigs.

“When the genetic mutation is introduced into mice, they do not display the symptoms of cystic fibrosis. That’s why these new swine models are so important. We have been able to get them through the initial stages of the disease, which they display just like humans, and now we are just waiting for them to grow and potentially develop the lung disease so we can start experimenting in ways that have never been possible,” he added.

Pigs were chosen for the research because they are much more similar in physiology, size, lifespan, anatomy and genetics to humans than mice.

Cloned pig embryos were created from genetically engineered cells, which were implanted into sows’ wombs to produce animals that carried one copy of the mutation. These “founder animals” were not affected by cystic fibrosis, but were interbred. One in four of their offspring had two defective copies of the gene, and so developed the disease.

The scientists, whose work is published in the journal Science, established that piglets with two defective CFTR genes showed biological markers of the disease, although the piglets do not have the abnormal lung function that characterises human cystic fibrosis. This may emerge as the animals mature, or the absence of lung problems in pigs could highlight a new approach to treating this aspect of the disease in people.

Christopher Rogers, another author of the paper, said: “The CF pig provides a unique opportunity to study one of the most common genetic diseases, and we hope to translate this new knowledge into better therapies and preventions.”

The inherited killer

Cystic fibrosis is the most common life-threatening, inherited disease in Britain, affecting about 8,000 people. More than 150 lives are lost to it each year

It causes the body to produce thick secretions of mucous that affect the lungs, digestive tract, bowels and other organs

Typical life expectancy for patients with the disease is 31, though improvements in management mean that people born today may expect to live longer. A heart-lung transplant is often needed to prolong life

The disease occurs when people inherit two defective copies of a gene called CFTR, one from each parent. One in 25 people carries one copy of the gene and, although not affected by it, has a one in four chance of having a child with cystic fibrosis if their partner is a carrier

Cystic fibrosis was first described clearly in 1938 by Dorothy Andersen, a pathologist at the New York Babies Hospital. There are earlier reports of infant deaths that conform to the symptoms of cystic fibrosis, some from the 17th century

Source: Cystic Fibrosis Trust

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