The Sumatran rhino - one of the most threatened animals on Earth - could be saved from extinction by creating the sperm of a dead male from his skin, new research has claimed. Scientists have created stem cells and miniature brains from the skin of Malaysia’s last male rhino Kertam - more than three years after his death.
It is hoped the frozen chunk of flesh taken from the shoulder will lead to the production of semen - which could then be used to impregnate females. Senior author Dr Sebastian Diecke, from the Max-Delbruck-Centre in Berlin, said: “We were excited to observe the formation of mini brains from Sumatran rhino stem cells in a seemingly comparable fashion as described for human organoids.”
The ultimate goal is to turn skin cells taken from deceased Sumatran rhinos into stem cells, from which they can then derive egg and sperm cells. They will be fertilised in the laboratory and the embryos will be carried to term by surrogate rhino mothers.
The new babies would be the offspring of Kertam and other individuals. Co author Dr Silke Frahm-Barske, also from Max-Delbruck, said: “To the best of our knowledge, mini-brains like these have only been obtained from mouse, human, and non-human primates so far. So we were very pleased to see that the stem cells we generated from the Sumatran rhino formed organoids quite similar to those of humans.”
The German team will next use Kertam’s iPS (induced pluripotent stem) cells to grow sperm suitable for artificial insemination. They are able to divide infinitely and therefore never die, and are able to transform into any cell type in the body.
Lead author Dr Vera Zywitza, based in the same lab, said: “This step is more difficult. To obtain sperm cells, we first need to use the iPS cells to cultivate primordial germ cells - the precursors of eggs and sperm.”
This is the tricky task the scientists are now going to tackle. They also plan to obtain iPS cells from other Sumatran rhinos. Reproduction expert Professor Thomas Hildebrandt, of Leibniz Institute for Zoo and Wildlife Research, said: “Measures are indeed being taken in Indonesia to preserve the Sumatran rhino population by bringing together the remaining individuals in wildlife reserves.
“But females that have not been pregnant for a long time often become infertile, for example due to cysts that develop on their reproductive organs, or they may just be too old to bear young.”
Sumatran rhinos have been hard hit by poaching and habitat loss. But the biggest threat is the fragmented nature of their populations. Breeding efforts have so far failed.
Dr Zywitza said: “Even though our work is attempting to make the seemingly impossible possible - that is, to ensure the survival of animals that would otherwise probably disappear from our planet - it must remain an exception and not become the rule.
“Despite all the buzz around what we are doing in the lab, this can at best make a small contribution to saving these rhinos from extinction. The protection and conservation of the animals’ few remaining habitats is at least equally important.”
Only a few dozen of the smallest and most ancient rhino species remain in the rainforests of Sumatra and Borneo. As a result, mating encounters are rare.
The Sumatran rhino has been considered extinct in Malaysia for the last three years following the deaths of Kertam in May 2019, and the last female, Iman, six months later. The species has been battling extinction for nearly a million years, with problems beginning in the last Ice Age.
Its complete DNA mapped from a male at Cincinnati Zoo revealed numbers peaked 950,000 years ago and have been in decline ever since. Climate change in the distant past reduced their genetic diversity, leaving them vulnerable.
In addition to preserving the species, the stem cells obtained from Kertam’s skin could serve another purpose. Dr Zywitza added: “iPS cells from exotic animals provide a unique tool to gain insights into the evolution of organ development.”
It is hoped the study published in iScience will open the door to saving a range of big beasts from extinction as the planet warms.