The northern white rhinos: A trip to extinction and back
Is it possible to bring someone back from the dead? San Diego scientists say yes!
In 2018, the last male northern white rhino, Sudan, bid adieu to the world leaving behind just two females too old to take forward the species. Sudan was 45 years old and lived under armed protection (against poachers who are the cause of the species’ extinction) in Ol Pejeta Conservancy, Kenya. He was suffering from an age-related complication1 and his caretakers decided to euthanize him when the suffering became unbearable for him. Since then, scientists worldwide have been looking at modern technologies to bring the species back into this world, specifically the scientists at the San Diego Zoo Safari Park2. Barbara Durrant, the Director of Reproductive Sciences at San Diego Zoo Institute of Conservative research, calls it their “most ambitious project”.2
The frozen zoo at San Diego, which has living cell samples from over 1,000 species, has skin cells from twelve northern white rhinos which will be used for the regeneration process. The process comprises four major and complicated steps. Let’s take a look at them in detail.
Step 1: From skin cells to stem cells
Once skin cells are formed, it’s impossible for them to further transform into any other type of cell, in this case to stem cells. However, the gene of every skin cell contains the information to do so. Owing to the Nobel Prize winner Shinya Yamanaka’s discovery in 20063 of how to access the genes, scientists reset the northern white rhino’s skin cells and succeeded in converting them into stem cells. After years of tweaking Yamanaka’s technique, we have seven clones of stem cells per 100,000 skin cells. It might take several more years for scientists to get the ideal stem cells.4
Step 2: Structure the stem cells to transform into eggs and sperm
Arranging the stem cells to convert them into sperms and eggs is called “gametes.” However, it’s not easy as it needs intracellular signals with the perfect timing, duration, and concentration. The team at San Diego Zoo hasn’t been able to strike the chord yet. However, during skin cells to stem cells transformation, a few gametes were accidentally created.
Step 3: Egg-sperm fertilization
The scientists would need to create the optimum ovary conditions for cultivating and fertilizing the northern white rhino eggs in an artificial environment. To understand those conditions, they decided to observe the southern white rhino’s eggs. In March 2020, they succeeded in obtaining healthy eggs. Dr Durrant said, “Right before COVID hit and shut everything down, we collected 22 [eggs] from our females at the rhino rescue center. And we got a 50% maturation rate which was fantastic for our first attempt, and we actually produced an embryo”.4
Step 4: From the laboratory into a womb
The embryo would need to be carefully placed into the womb of a southern white rhino who will help the scientists resurrect the northern white rhinos. For an embryo to develop, the womb should have an ideal yet agile environment that can quickly cater to the embryo’s needs.
The scientists conducted thousands of ultrasounds to study the rhinos’ reproductive system and each rhino’s reproductive cycle. The aim was to determine the best time to place the embryo and optimize the chances of its acceptance by the rhino’s body.
“[W]e can predictably get them to ovulate within 48 hours, and that took a couple of years for us to figure out. So every step of the way is kind of a long process, but each step takes us closer to success,”4 said Dr Durrant.
In 2019, for the first time in the world’s history, two southern rhino calves were born out of artificial insemination indicating the southern white rhino’s ability to reproduce with a technology’s intervention. With this, the journey toward the end of many more extinctions began.
References:
1. Northern white rhino: Last male Sudan dies in Kenya. BBC. https://www.bbc.com/news/world-africa-43468066 (20 March, 2018).
2. Can this “frozen zoo” resurrect the Northern White Rhino? Bigthink. https://bigthink.com/videos/white-rhino-extinction/
3. Scudellari, M. How iPS cells changed the world. Nature 534, 310–312 (2016). https://doi.org/10.1038/534310a
4. Northern white rhino: resurrecting an extinct species in four steps. Bigthink. https://bigthink.com/life/resurrection-deextinction-northern-white-rhino/ (22 March, 2022).
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