IIn the bamboo forest, a giant panda is munching on bamboo leaves, but for how long will it continue? This adorable bear has few natural predators, Vulnerable.1 Today, fewer than 2,000 giant pandas remain in the wild, with another 600 surviving in zoos and protected habitats around the world. This comprehensive species decline has ripple effects throughout the ecosystem, so scientists are working to protect and increase the numbers of these gentle bears. Because inbreeding within small populations can lead to a loss of genetic diversity, reducing resistance to diseases and parasites, researchers are exploring new conservation approaches.
In 2011, scientists discovered that a revolutionary technology, induced pluripotent stem cells (iPSCs), could: Endangered iPS cells were generated from endangered species, then the northern white rhino, Tasmanian deviland Grevy’s Zebra.2–4 But while scientists have had some success generating stem cells, Buccal mucosa cells No truly pluripotent cells have been found in giant pandas.5
that’s why Jing LiuA stem cell biologist at the Chinese Academy of Sciences, he was asked by the Chengdu Research Base of Giant Panda Breeding in 2019 to create panda iPSCs from fibroblasts, and he took up the challenge. Scientific advances, Liu and his team reported that iPSCs could be generated from giant panda skin cells.6 Their findings open new avenues for researchers to study pandas’ ecology in more detail and devise new measures to protect them.
The journey from panda fibroblasts to iPSCs wasn’t easy. When Liu and his team tried to reprogram the conditions that worked for other species, they hit their first hurdle: “To our surprise, when we used mouse and human conditions, it didn’t work for pandas.” [cells]” Liu said.
“The mouse recipe is not necessarily directly applicable to other species, even within mammalian species,” he said. Pierre Comissoli“So to really understand what factors influence cellular reprogramming, we have to go back to basics every time,” said gamete biologist at the Smithsonian’s National Zoo and Conservation Biology Institute, who was not involved in the study.
After much trial and error, Liu and his team finally discovered that introducing specific microRNA clusters was the key to converting fibroblasts into iPSCs. By modifying growth conditions by adding molecules such as panda-specific transcription factors, the team was able to obtain iPSC clones. “The clones were so beautiful. We were so excited,” Liu recalls.
The team then confirmed that the iPSCs they had identified based on their physical characteristics displayed the genetic characteristics associated with stem cells they were looking for, including reduced expression of genes associated with somatic cells and an abundance of pluripotency-related genes.
After tweaking the reprogramming steps, Liu and his team aimed to shorten and streamline the process. By making some adjustments to the cell culture medium to include specific signaling pathway modulators, epigenetic inhibitors, and kinase blockers, they reduced the overall experimental period from more than three months to less than one month, and increased efficiency fivefold compared to not changing the medium.
The hallmark of true pluripotent stem cells is their ability to divide and form the three germ layers (endoderm, mesoderm, and ectoderm), which are crucial for the development of body tissues and organs. To test the giant panda iPSCs, the team observed the formation of embryoid bodies, which are collections of pluripotent stem cells that recapitulate some aspects of early embryonic development. This developmental stage showed an increase in ectodermal markers, while later stages showed an increase in mesodermal and endodermal markers. When the giant panda iPSCs were injected into mice, the cells formed clumps displaying the three germ layers, including elements of neural, muscle, and epithelial tissue.
“You can generate iPSCs, but then when you put them in culture, they want to go back to a more specialized state, which is really difficult,” says Comizzoli. “But this paper describes some really interesting culture conditions to keep iPSCs in the same state for a long time, which is really exciting for the field.” But Comizzoli emphasizes that just because these conditions worked for giant pandas doesn’t automatically mean they’ll work for other species.
Liu hopes that one day giant panda stem cells can be used to produce sperm and oocytes that can be used to create giant panda embryos. “We want to use these stem cells to create animals,” Liu says. “This is a challenge in this field.”
According to Comizzoli, there is still a long way to go before scientists can generate functional gametes from iPSCs. “The most immediate application is in regenerative medicine to treat sick pandas and to better understand the embryology and fetal development of these animals,” he said.
