Amid the current whirlwind of depressing research regarding the current state of our planet, let’s take a break for something a little more light-hearted. And fluffy. In a landmark study, published in PLOS ONE, scientists have produced the world’s first test-tube puppies, using in vitro fertilization (IVF) to bring seven bundles of joy into the world.
Although fertilization is very much a natural process, getting it right in a test tube is notoriously difficult; it’s not as simple as putting an egg and sperm cell together. The donor sperm must have reached the correct phase of maturation, known as capacitation, which enables them to penetrate the egg. The egg cells, or oocytes, must also be obtained at a developmentally competent stage. The conditions in the lab must also be optimal to keep the fertilized cells viable.
Coupled with the fact that dogs have a unique reproductive physiology compared to other mammals, scientists have spent decades struggling to develop assisted reproductive technologies for these animals. But a group from Cornell University, headed by Alex Travis, has finally managed it.
The first hurdle the researchers had to overcome was getting an oocyte at the right stage of maturation for fertilization to be possible. Dogs release eggs at an earlier stage of maturation compared with other mammals, which needs to mature in the fallopian tube in order to be fertilizable. This stage is reached around 60 hours post-ovulation.
While most mammalian oocytes are fertilizable four days after the surge of hormones that drive ovulation, the team discovered this wasn’t the case for dogs. “If we took them from the oviduct at day 5 we got some success, but at day 6 it started working really well,” Travis told IFLScience.
The team also found that the medium scientists had been using to drive sperm capacitation was missing a crucial ingredient: Magnesium. According to Travis, adding this not only boosted the motility of the sperm, making the tail hyperactive, but it permitted the onset of a secretion event that is a prerequisite for egg/sperm fusion, called acrosome exocytosis.
“This releases things that help the sperm make its way to the egg,” said Travis, “like proteins that help it stick to the oocyte.”
One of the gorgeous IVF puppies. Image credit: Cornell University College of Veterinary Medicine
Using this modified approach, the team implanted nineteen embryos into a recipient dog, which gave birth to seven puppies. Five of these were from beagle parents, while two were from a beagle mother and cocker spaniel father. In addition, the embryos had previously been frozen, a crucial practical aspect given the limited window of fertility in dogs.
The idea behind this research isn’t to selfishly bring more designer dogs into the world, such as pocket-sized variants of existing breeds, but to contribute towards far more honorable causes. Now this has been achieved with domestic dogs as a model, it may be possible to apply the technique to endangered canid species in order to raise dwindling numbers.
In addition, this research may lead to improvements in the welfare and health of domestic dogs. Intense inbreeding for desirable traits has led to many breeds being predisposed to various diseases, such as blood or metabolic disorders. Golden retrievers, for example, are prone to blood cell cancers, or lymphoma. But with IVF now demonstrably possible in these animals, this raises the possibility that faulty genes could be edited out of embryos to stamp out certain heritable diseases.
Alongside the implications for dogs, this research could also benefit humans: Around 350 human diseases have equivalents in dogs, so learning from them could provide crucial advances in medicine.
2
