An international team of scientists has successfully created hybrid in vitro embryos, combining the nearly extinct northern white rhinos and its relative species, the southern white rhinos.
The result is the very first generation of pre-implantation embryos of rhinos in a test tube. To date, the embryos are showing all vital signs of the healthy embryonic stem cells. This was made possible by a method called "assisted reproduction techniques" or ART.
The breakthrough experiment was conducted with the primary goal of saving the northern white rhinos from extinction. The frozen sperm cells used for the experiment were acquired from the male northern white rhinos when they were still living.
The Test Tube 'Baby' Rhinos
Sudan, the last male northern white rhino died in March. The only ones left of his species were only two infertile female rhinos. On the other hand, there are still about 21,000 southern white rhinos living in Africa.
The hybrid embryos being grown in the lab contains DNA of Sudan's species. If they thrive, they will be implanted to surrogate rhino mothers that could, later on, give birth to a rhino calf closely related to Sudan.
Then, if this whole process became successful, the next step will be combining the frozen sperm cells of the northern white rhino with the egg cells of the remaining two females. In years to come, there will finally be few true breed northern white rhino calves once again, saving the entire species from the brink of extinction.
Ultimately, proponents of the experiment are looking forward to using ART in saving all nearly endangered species. They also envisioned to bringing already extinct species back from the dead.
The ART
ART was created by a team led by Cesare Galli, a veterinarian, and embryologist working at Avantea, a biotechnology laboratory in Italy. The method involved extracting eggs from female rhinos, in this case, the southern white rhinos and fertilizing them with the sperms of the northern white rhinos.
The team was able to extract 13 eggs from 12 female southern white rhinos. Of these 13 eggs, four developed into hybrid embryos. They are now being frozen and later will be implanted into a surrogate mother that will give birth to a hybrid offspring.
To be sure that the embryos are healthy, the team also observed the stem cell lines of two of the embryos.
"These are the first in vitro produced rhinoceros embryos ever. They have a very high chance to establish a pregnancy once implanted into a surrogate mother," explained Thomas Hildebrandt, head of the department of Reproduction Management at the German Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in Berlin.
Details of their experiment are published in the journal Nature Communications on July 4.
The First Northern White Rhino Calf Through ART
The next step for the team is to harvest eggs from the last two female northern white rhinos, fertilize them with the male sperm cells of their species, and then implant these embryos to a surrogate mother rhino.
Hildebrandt said they are looking to see the first northern white rhino calf born in three years' time.
To achieve this last goal, the scientists will add another step to the whole process: they will use stem cell technology to engineer eggs and sperm from the frozen skin cells of 12 deceased northern white rhinos.
"Our results are solid, reproducible and very promising. Now we are well prepared to go to Kenya and collect [eggs] from the last two [northern white rhino] females in order to produce pure [early embryos] where both eggs and sperm are from [northern white rhino]," Hildebrandt said.
