"An global team of scientists has now successfully created hybrid embryos from Southern White Rhino (SWR) eggs and Northern White Rhino sperm using assisted reproduction techniques (ART)", the researchers from Avantea, a laboratory of advanced technologies for biotechnology research and animal reproduction, noted in a statement.
"Our goal is to have a northern white rhino calf on the ground in three years", lead author Thomas Hildebrant, a wildlife reproductive biologist at Germany's Leibniz Institute for Zoo and Wildlife Research, told reporters during a Tuesday press briefing.
This would result in hybrid embryos which can then be implanted in surrogate mothers, paving the way towards the resurrection of the northern white rhino species. The two remaining female northern white rhinos, who are infertile, were doomed to live out their lives as the last of their kind.
A team of scientists designed a hybrid embryo with the DNA of the almost extinct northern white rhino.
Alternatively, if scientists are allowed to take eggs from the two living northern white rhinos, a pure-bred calf could be born.
The team now hopes to use the technique to collect eggs from the last two northern white rhinos - Najin and Fatu, the daughter and granddaughter of Sudan.
The NWR can only reproduce in the zoos very slowly.
"The northern white rhino sperm, when they were thawed out, were not very good and had to be activated by an electrical stimulus", says Professor Renfree.
But the procedure is not without risk: "we have to do a full anaesthesia, the animal is down for two hours, and it is quite a risky situation" for the last two of their kind, conceded Hildebrandt.
Embryonic stem cell lines, which have been produced with the southern white rhino, provide another option.
The northern white rhinoceros is the most endangered mammal in the world. These are mature sexual reproduction cells, like a sperm or egg, that join to create a zygote, or fertilized egg cell.
Zoologist say that due to the fact that the number of genuine reproduction material of northern white rhinos is limited to four individual donors, this dramatically narrows down the base required to create a viable population for maintaining sufficient genetic diversity. To retrieve eggs, the researchers put the animal under anesthesia, and then used an ultrasound machine to guide a long needle into her uterus, puncture her follicles and dislodge the eggs. The objective of simply preserving the subspecies' genes in a new hybrid rhino (in captivity), and whether it would be worth all the effort, is unclear. If we could not save it when it was here (the last wild northern white rhino is thought to have disappeared around 2006) it seems unlikely we could conserve a resurrected wild population now or in the foreseeable future.
They ended up with a handful of embryos, some of which could potentially be implanted into surrogate rhino mothers.
Researchers have increased efforts to develop new scientific advances to bring the species back to life again.
"The beauty of it is that we have a southern white rhino that is very closely related to the northern white rhino, and it's very likely that a southern white rhino could carry a northern white embryo to term", Roth said. "We should come at it with everything we've got", Roth said.
"They have formally said they will give us the necessary support", he said.