Cloning has long been a topic fraught with controversy and vocalized concern about where the technology would lead. While we still grapple with these ideas to this very day, the science itself continues to move forward toward a better understanding of how cloning works and what repercussions biologically it might have. Or might not have, as will be shown in today’s discussion.
The History of Mammal Cloning
The process of cloning itself has been a part of the public consciousness since 1997 when the first successful clone of a mammal from adult cells was achieved. You may know her as Dolly the sheep and we’ll get back to her later in this article.
Later that same year, the first dog cloning attempt was made. Researchers at Texas A&M University tried to clone a dog named Missy, but the attempt ultimately failed. This was somewhat surprising at the time, since other species in the same year and over the next few years saw little trouble in cloning mammalian species. But it all came down to the uniqueness of canids in general.
Since the reproduction of canid mammals is on a monoestrus cycle (once per year), it presented some difficulty in proper timing of having a cloned embryo grow inside of a surrogate canine mother. But, by 2005, scientists in South Korea had found a way around this and produced the first dog clone named Snuppy, cloned from an Afghan hound named Tai.
A Healthy Clone Puppy
As with Dolly before him, there were concerns about whether clones would exhibit enhanced disease formation and early onset of age-related disorders. However, Snuppy presented a normal growth pattern and did not appear to develop any special diseases as he aged. His weight was within normal parameters and he showed normal reproductive function. This achievement led to a broader industry for dog cloning, not just for research, but also for the creation of specialized service dogs and the ability to clone those with more advanced traits and abilities.
Both Tai and his clone Snuppy lived to the normal age of between 10 and 12 years for their breed before developing age-related cancers, as is normally expected. With their deaths in the past two years, the researchers involved in the cloning decided to take the next step and make another group of dog clones. But not ones based on Tai once more, but instead clones taken from Snuppy’s cells.
Clones of an already cloned dog.
Improving Production of Clones
Using stem cells from fat (adipose) tissue of the mesenchyme (the tissues that form into bone and muscle), the South Korean scientists took 120 female egg cells, oocytes, and injected Snuppy’s stem cells into them. After culturing and an improved successful fusion rate of 86.6%, the previous rate had been 67.2%, they were able to transfer 94 of the embryos into female dog surrogates.
Of these, 4 of the embryonic cells properly gestated and grew to term, producing 4 Snuppy puppy clones 59 days later. The puppies were found to be healthy and all within normal weights for their breed. One of the puppies did end up dying 4 days later due to a severe diarrhea condition, but since this is known to happen to 10-25% of the puppies of this breed, it was considered a normal outcome.
As of the published paper, these three cloned clones are 9 months old and appear to all be healthy. Genetic testing confirmed them as being clones from Snuppy’s cells and, as of now, there seems to be no negative health outcomes from cloning clones.
Re-investigating Dolly the Sheep
Now, let’s jump back to the topic of Dolly the sheep really quick to discuss the results from another recent, but unrelated study. Many of the health concerns over animal cloning stem from the fact that Dolly the sheep died at 5 and a half years of age due to osteoarthritis (OA).Since this was the first mammal clone, this happening sent the scientific community into, if you’d allow me an exaggerative term, a tizzy.
Does cloning result in the cells of the new organism keeping knowledge of their prior age? If an elderly animal is cloned, will the newborn exhibit the disorders expected of an older animal? The results that Dolly showed raised all of these questions and more, almost stopping the cloning field in its tracks at the same time. But perhaps all of that concern was baseless from the beginning.
A collaboration between the University of Nottingham and the University of Glasgow led to a radiography test being done on not just the skeleton of Dolly the sheep, but also on her naturally conceived daughter, Bonnie, and on two other cloned sheep that were the first to be made from differentiated cells rather than stem cells.
What they found was…nothing. The two older sheep, Bonnie and Megan, were seen to have mild forms of OA, but it was natural for them to have as such at their age. Meanwhile, what about Dolly? There were no signs of OA in the areas that were claimed at the time of her death and only minor beginnings of it in some of her joints.
Science Needs Duplication
Overall, the scientists concluded that the distribution of OA among all the sheep clones they tested were no different than what one would expect to find in a non-cloned group of sheep. Any and all concerns of OA in Dolly appeared to be unfounded. Since it then emerged that the claim of OA development in Dolly’s left knee was only ever stated in a conference abstract, it can only be presumed that a mistake of some sort was made.
A mistake that the media capitalized on and which led to further dramatization within the scientific community for those that were unaware that the facts about the claim were inaccurate. If anything, this only further emphasizes that science requires proper re-testing and duplication of results in order to be absolutely sure of the accuracy of claims being made, even mundane claims like osteoarthritis in a sheep’s knee.
So, based on this, I think it is safe to say and conclude, at least for now, that clones develop normally and do not suffer from adverse early-onset age-related disorders. They may develop those conditions later in life, but at no different a rate than non-cloned animals do. Therefore, at least on the health front of the debate, there shouldn’t be any untoward concerns about the impact of cloning on the cloned organisms themselves.
Photo CCs: Afghan Hound blond portrait from Wikimedia Commons