Rhino embryos
Artificial insemination will help save northern white rhinos
Daria Spasskaya, N+1
Scientists with the help of artificial insemination for the first time managed to obtain "in vitro" embryos carrying the genetic material of northern white rhinos – an almost extinct subspecies of rhinos. To do this, embryologists had to develop a method for obtaining eggs from female southern white rhinos, which were then fertilized using frozen sperm from a male northern rhinoceros. As scientists promise in an article in Nature Communications (Hildebrandt et al., Embryos and embryonic stem cells from the white rhinoceros), the resulting embryos will be planted to surrogate mothers.
The Northern white rhinoceros is a subspecies of rhinoceros, the world population of which disappeared before the eyes of scientists in the second half of the XX century. In the 60s, the number of individuals was several thousand, and in March of this year, the last male of the northern white rhino died in a reserve in Kenya, and currently only two females who are kept in the same reserve remain alive.
Over the past two decades, attempts have been made to begin restoring the population of northern rhinos in captivity in a natural way, which have been unsuccessful. Nevertheless, over the past 30 years, researchers have been preserving the cellular material of these animals, among which was the frozen sperm of three males, of rather poor quality, but still potentially suitable for fertilization of eggs. Since only two females of this subspecies remained alive, already old and infertile, the researchers decided to obtain material for fertilization from females of southern white rhinos living in South Africa, whose population currently maintains a stable number.
To obtain rhino eggs, the staff of the Wildlife Research Institute in Berlin and the Avantea Reproductive Technology Laboratory in Cremona (Italy) developed a protocol for stimulating the ovaries of animals and a special set of instruments for surgery, and then obtained the material transrectally using an ultrasound device that allows you to see the ovary and take cells from there. Female egg donors were kept in several European zoos.
The procedure of taking eggs from a female rhinoceros (left) and ultrasound of the ovary (right). A drawing from an article in Nature Communications.
After receiving the eggs, they were brought to the desired stage and fertilized with sperm injection. The resulting zygotes were divided up to the blastocyst stage, suitable for implantation into the uterus of surrogate mothers. Cell lines of embryonic stem cells were obtained from part of the embryos. Manipulations with these lines, including their transformation into germ cells, in the future can help to obtain material for fertilization if the experiment on planting the obtained chimeric embryos to mothers fails. The researchers are also going to use the developed technology to take eggs from the last two females of the northern rhinoceros to try to fertilize them in vitro.
To revive the northern white rhinos, geneticists are also considering cloning them. For example, researchers from the San Diego Zoo obtained 12 cell lines of northern rhinoceros fibroblasts, DNA sequencing of which showed sufficient genetic diversity to restore the population.
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