The last male rhino bull in Malaysia died in 2019 - since then the Sumatran rhino has been considered extinct there. A research team has now succeeded in extracting valuable stem cells from his skin cells and using them to grow “mini brains”. The next goal is then to produce egg cells and sperm from the stem cells in order to save the endangered species from extinction.
The Sumatran rhino (Dicerorhinus sumatrensis) was once widespread in parts of East and Southeast Asia, but today fewer than 80 individuals of this smallest and most pristine rhino species remain in the world. Increasing poaching and the destruction of their habitat in the rainforests of Sumatra and Borneo has resulted in the rhino population shrinking to small numbers. In Malaysia, the Sumatran rhino has even been considered extinct since the death of the bull Kertam and the cow Iman in 2019.
Back to life with stem cells
But there is still hope for the offspring of Kertam and Iman, because a research team led by the scientist Vera Zywitza from the Max Delbrück Center for Molecular Medicine in Berlin is already working diligently on a future for the Sumatran rhinos: They have set themselves the goal Transforming skin cells from deceased rhinos into stem cells and using these to grow egg and sperm cells suitable for fertilization in the laboratory. Animal surrogate mothers are then supposed to carry the rhinoceros embryos created in the Petri dish – as descendants of Kertam and other animals that have already died. Generating viable and fertile offspring from such induced stem cells has already been achieved in mice, making Zywitza and her colleagues optimistic about the method's success in rhinos and other endangered species.
To obtain stem cells, they use methods that were developed as part of the "BioRescue" research project for the even more threatened northern white rhino. "Our current study has benefited a lot from the knowledge gained through this large-scale project funded by the Federal Ministry of Research," says Zywitza. And the first results are already promising: The scientists have succeeded in generating induced pluripotent stem cells from the skin samples of the deceased rhinoceros Kertam. Like cancer cells, these so-called iPS cells can divide indefinitely, making them valuable repositories of these rhinos' endangered genetic information. What is even more important, however, is that these stem cells can develop into any type of cell in the body, such as neurons, liver cells, muscle cells or egg cells and sperm.
From "mini-brains" to germ cells
After successfully harvesting stem cells, Zywitza and her colleagues went one step further by growing so-called mini-brains from the iPS cells. In order to stimulate the development of stem cells into neurons and brain structures, they use messenger substances that also occur in the human brain. According to the researchers, the resulting brain organoids continued to develop in a self-organized form. “Little is known about the rhino brain and its development during embryogenesis. Therefore, this development of brain organoids opens up unprecedented opportunities for exploring and understanding the development of the rhino brain,” explain Zywitza and her team.
The next goal is now to grow sperm cells from Kertam's induced stem cells that are suitable for artificial insemination. “However, this step is more difficult,” says Zywitza. "In order to obtain sperm, it is first necessary to generate primordial germ cells, the precursors of egg and sperm cells, from the iPS cells." This tricky task is now to be tackled next.
However, the scientists also warn against considering stem cell technology as a simple remedy against species extinction: "Even if our work tries to make the seemingly impossible possible, namely to conserve species that would otherwise probably disappear from our planet, it has to The exception and must not become the rule,” says Zywitza. "Despite all the enthusiasm, what we are doing in the laboratory can at best make a small contribution to saving the rhino from extinction." It is even more important to protect and preserve the existing habitats of these animals.
Source: Max Delbrück Center for Molecular Medicine Berlin, Article: Iscience, doi: 10.1016/j.isci.2022.105414