A healthy litter of puppies was just born by in vitro fertilization, representing the first time this reproductive technology has been successfully applied to dogs.
The scientists who announced the achievement, outlined in the latest issue of PLOS ONE, say that the breakthrough holds promise for gene-editing of dogs to eradicate certain diseases and disorders, and in saving endangered wild canines from extinction.
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"Genetically modified" is a red flag for many, with a global summit held just last week in Washington, D.C., addressing some of the concerns and controversies. Supporters, however, believe that the pros far outweigh the cons.
For the in vitro pups, the process involved transferring 19 embryos to a host female dog. She gave birth to seven healthy puppies, two from a beagle mother and a cocker spaniel father, and five from two pairings of beagle fathers and mothers.
"Since the mid-1970s, people have been trying to do this in a dog and have been unsuccessful," co-author Alex Travis, associate professor of reproductive biology in the Baker Institute for Animal Health in Cornell's College of Veterinary Medicine, said in a press release.
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Lead author Jennifer Nagashima (a graduate student in Travis' lab), Travis and their team overcome many challenges during the project. The first was to collect mature eggs from a female dog oviduct. Timing was key, and required a lot of trial and error to get the eggs at just the right stage.
The second challenge was figuring out how to simulate the way that the female dog reproductive tract prepares sperm for fertilization. This again required some trial and error, with the researchers determining that the addition of magnesium to the cell culture in the lab properly prepared the sperm.
With the egg collection and sperm prep problems solved, "now we achieve success in fertilization rates at 80 to 90 percent," Travis said.
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Finally, the researchers had to freeze the embryos. This allowed precise control of the timing for when the embryos were inserted into the recipient dog's oviducts, which are essentially the canine version of Fallopian tubes in humans. One of the resulting pups, appropriately named "Klondike," was born from an embryo that had been in the freezer since 2013.
The trouble to do all of this was well worth it, the researchers believe, given how the technique could benefit wildlife conservation.
"We can freeze and bank sperm, and use it for artificial insemination," Travis explained. "We can also freeze oocytes, but in the absence of in vitro fertilization, we couldn't use them. Now we can use this technique to conserve the genetics of endangered species."
This means that he and other conservationists can now store semen and eggs and bring their genes back into the gene pool in captive populations. In addition to endangered species, this process could also be used to preserve rare breeds of show and working dogs, he said.
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Travis added that technology also offers "a powerful tool for understanding the genetic basis of disease."
It is hoped, for example, that genome editing could remove genetic diseases and traits in dog embryos. Some of these problems, such as lymphoma in golden retrievers and urinary stones in Dalmations, have resulted from inbreeding due to humans previously selecting for desired traits.
Canines share more than 350 similar heritable disorders and traits with humans, almost twice the number as any other species, so such research could, in future, lead to medical breakthroughs benefitting humans, too.