Frozen Skin Cells Could Create A New Future For Endangered Northern White Rhinos
Friday, December 13, 2019
Photo by Erik Anderson
Future is a month-old baby rhino that tipped the scales at 132 pounds when she was born.
The energetic and curious rhino is learning about the world in the presence of her mom, Amani.
The young animal does not stray far and during a recent visit, she seemed much more interested in playing with a plastic tub, than the fact that she is playing a role in a critical rhino recovery effort.
Future’s mom, Amani, and five other females were brought to San Diego in 2015 to be surrogate moms for the critically endangered northern white rhinos.
“This is an animal that will be extinct in our lifetime,” said Jeanne Loring, a stem cell biologist who works in San Diego. “It’s already extinct. It just happens to be still walking around in a couple of instances.”
She is referring to two northern white rhinos who are still alive and living in a protected reserve in Kenya. Both are females, but neither is able to breed.
Loring is pioneering research that could play a crucial role in the effort to revive the struggling rhino species.
She is helping turn a dozen northern white rhino skin cell samples stored in nitrogen freezers into pluripotent, or adult, stem cells.
“So, we have a total of nine, now, in the freezer,” Loring said.
Those stem cell lines can become any adult cell in a rhino’s body.
That is something that has never been done with rhinoceros cells before, although researches have been able to do it with mice.
Stems cells are not the final goal.
Loring hopes to eventually create rhino sex cells, opening the door to creating a northern white embryo.
“Now we’re at the stage where we’re seeing the first signs of development into sperm and eggs,” Loring said. “Those are called primordial sperm cells because sperm and eggs are germ cells, primordial in the early stages.”
The work used to be concentrated in Loring’s lab, but there is also a small lab on the grounds of the San Diego Zoo Safari Park.
That is where Marisa Korody is helping draw up the scientific guidebook, which will eventually show researchers the path from skin cells to rhino embryos.
“We give them the signals that tell them to turn into whatever cell type we want,” said Korody. “So it can be giving them growth factors or it can be using specific chemicals that will turn on or turn off different pathways in the cell cycle that you can basically direct it to turn on specific genes when you need them.”
Korody was introduced to the project in Loring’s lab and she welcomed the chance to help a species that is so close to extinction.
In the lab, Korody has to constantly manage the stem cell cultures under her care.
“We feed it every 24 hours so somebody is here every day. I was here feeding them yesterday,” Korody said. “If we don’t feed them that frequently, that growth factor, that makes them maintain their stem cell state, will break down. It’s heat sensitive.”
Those daily chores occasionally yield spectacular results.
Korody showed a video of stem cells that are on their way to becoming basic rhino heart cells. This culture of cells was actually expanding and contracting in a Petri dish.
“So these are just responding,” Korody said. “There’s no pacemaker so there not as in sync as they would be if they were an actual heart. But yes, these are cardiomyocytes from Angelifu.”
Angelifu was the last male northern white to live in San Diego. He died in 2014 and his female partner, a northern white named Nola, died the following year.
The last living male died in Sudan in 2018, leaving just two barren females.
Developing those fledgling heart cells gives hope that northern white sperm and eggs are not far off. That would be a major step toward a northern white embryo that could be implanted in one of the San Diego Zoo’s six surrogates.
The cloning of Dolly the sheep and subsequent stem cell advances have opened a door.
“If we can make rhino’s cells have babies, and we can reconstitute a functional breeding population of northern white rhinos,” said Oliver Ryder, the Zoo’s geneticist. “We can take a species that is functionally extinct and return it to its habitat once that’s secure.”
Ryder was standing in the San Diego Zoo’s Frozen Zoo.
This secure area is filled with nitrogen-cooled freezers that hold genetic material from thousands of animals. Some endangered. Some not.
Some have dozens of samples. Others just one or two from a particular species.
“There’s a great need to expand this effort on a global basis through regional centers in different countries,” Ryder said.
This seed bank of cells idea is catching on, according to Ryder and he thinks it is vital for the future of northern white rhinos and possibly other species.
That is because the technology being developed in San Diego for the rhinos could be applied to other animals. And Ryder carries a sense of urgency.
“I have a constant sense of the march of time and the grim reaper of species extinction. Being out there," Ryder said.
But science, Ryder said, could be the key to undoing some of the man-made harm driving plants and animals to the edge.
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