Thirty-seven years after the first human baby was born via in vitro fertilization, researchers at Cornell University announced that the first set of puppies conceived using the method have been born. With this success, researchers say they plan to use this technique to try to conserve endangered species and to study and treat many genetic diseases that are common in dogs. Their results were published today in the journal, PLOS ONE.
A host female dog gave birth to seven puppies, two of which were from a beagle mother and a cocker spaniel father, and five of which were from beagle parents.
For the past thirty years, researchers have been trying to use assisted reproductive treatments in dogs. Unlike in humans and other mammals, an oocyte (or unfertilized egg) in a dog requires time to mature before it can be fertilized. Finding the ideal time to remove the egg from the female dog’s oviduct (Fallopian tubes in humans) was crucial for reproductive success, and the researchers found that by leaving the egg in the oviduct for one extra day, it was much more likely to later become fertilized.
“The work reported in this new study makes a great advance by identifying the timing at which ovulated oocytes reach the ability to be fertilized,” says Pablo Ross, an assistant professor at the University of California at Davis, who studies reproductive biology in domestic animals and wasn't involved in the study.
The researchers overcame two additional challenges: They figured out how to better simulate the conditions inside a female’s oviduct that allows for fertilization to occur, and they found that freezing the embryos allowed them to insert the eggs at the right time when a female dog is in her reproductive cycle--which occurs only once or twice a year.
Alex Travis, a professor of reproductive biology at Cornell who led the study, says the success of this method will help not only treat diseases in dogs but humans as well. Humans and dogs share more than 350 similar heritable conditions, which is more than any other animal, including mice who are often used as a model for disease.
The ability to produce high-quality embryos with IVF will allow researchers access to the most simple of all the live stages of any individual, which is the one-cell stage, says Ross. This gives scientists the ability to perform germline editing using techniques like CRISPR more effectively, and therefore a useful way to study diseases common to both humans and dogs.
This could also help in researchers’ attempts to eliminate many heritable diseases in dogs alone. Currently, many researchers and breeders employ genetic testing to screen for these conditions, which can be very successful. However, when a certain disease affects such a high percentage of a breed, this screening process could lead to inbreeding, which can increase the chances of other heritable diseases.
By using gene-line editing techniques like CRISPR, a modification that eliminates a disease causing gene will result in not only that animal being free from disease but also its offspring and all future generations; in this way, certain heritable conditions could theoretically be eliminated.
Travis and his team, in conjunction with the Smithsonian Conservation Biology Institute, also plan to use IVF for wildlife conservation. IVF allows researchers to store semen and eggs from endangered species and then bring those back into the gene pool in captive populations, says Travis. In the future, they hope to employ IVF maturation, in which researchers remove the eggs from the ovaries before they are matured and then they mature in the lab instead, and are then fertilized. This technique could especially help endangered populations where a young female dies before she has a chance to reproduce. IVF maturation could give those genes a “second chance” says Travis, and help ensure that female genes still make it to future generations.
While that technique still requires more research to perfect, researchers are hopeful that the success of IVF as well as the recent advances in gene editing will help researchers to attempt to better treat and prevent heritable diseases in dogs.
