A litter of seven healthy puppies were born to a female surrogate dog by IVF.

Breakthrough 'may help eradicate hereditary disease'

The world's first litter of 'test tube' puppies has been born in the US. Scientists behind the breakthrough say the research has implications for endangered species and could even help to eradicate hereditary diseases in dogs.

A female surrogate dog gave birth to seven healthy puppies by in vitro fertilisation (IVF). Two were from a beagle mother and cocker spaniel father, while the other five puppies were from two beagle pairings.

"Since the mid-1970s, people have been trying to do this in a dog and have been unsuccessful," said Alex Travis, associate professor of reproductive biology at Cornell University.

For IVF to be successful, a mature egg must be fertilised with sperm in a laboratory to produce the embryo. The embryo must then be inserted into a surrogate female at the right time in her reproductive cycle.

When Cornell researchers first tried to collect eggs from the female oviduct, the eggs failed to fertilise. Initially, they had tried to use eggs that were at the same stage of maturation as in other species.

By experimentation they found that if they left the egg in the oviduct for an extra day, fertilisation was greatly improved.

As the female tract prepares sperm for fertilisation, the team had to find a way to simulate this in the lab. They found they could achieve this by adding magnesium to the cell culture.

Dr Travis said: "We made those two changes, and now we achieve success in fertilisation rates at 80 to 90 per cent."

Finally, freezing the embryos allowed researchers to insert them into the surrogate's oviducts at the right time in her reproductive cycle, which occurs only once or twice a year.

Scientists say their findings, used alongside gene editing techniques, may one day help to remove hereditary canine diseases.

"It opens up the possibility that we could identify certain genes that cause disease and then fix those, replace them with a good copy of the gene before those dogs are even born," Dr Travis explained.

"So instead of trying to cure the disease we can help prevent it from happening in the first place."

The findings also have wide implications for the conservation of endangered animals, allowing scientists to store semen and eggs and bring the genes back into the gene pool.

Watch a video clip of the puppies here: http://www.cornell.edu/video/worlds-first-puppies-born-by-in-vitro-fertilization

Image courtesy of Cornell University