meA giant panda is munching on bamboo leaves in a bamboo forest. But how long will it last? These cute bears have few natural enemies, but Vulnerable.1 Fewer than 2,000 giant pandas live in the wild today, with another 600 surviving in zoos and protected habitats around the world. The loss of this umbrella species would have ripple effects across the entire ecosystem, so scientists are working to conserve and increase the population of these gentle bears. Inbreeding within small populations can lead to a loss of genetic diversity, potentially reducing resistance to diseases and parasites, so researchers are looking for new conservation methods.
In 2011, scientists speculated that a revolutionary technology called induced pluripotent stem cells (iPSCs) could be the key to preserving life. endangered Since generating iPSCs from vulnerable species and northern white rhinoceros Tasmanian Deviland Graviala.2-4 However, scientists have had some success in creating stem cells. Cheek mucosa cells In the case of the giant panda, no truly pluripotent cells were found.5
So when Jing RyuA stem cell biologist at the Chinese Academy of Sciences, he was asked by the Chengdu Giant Panda Breeding Research Base in 2019 to create giant panda iPSCs from fibroblasts, and he took up the challenge. Now, Advancement of Science, Liu and his team reported that they could generate iPSCs from giant panda skin cells.6 These findings open new avenues for researchers to further study panda biology and devise new strategies to conserve the species.
The journey from panda fibroblasts to iPSCs was not easy. When Liu and his team first tried to reprogram conditions that had worked in other species, they ran into their first hurdle. “Surprisingly, when we used conditions from mice and humans, they didn’t work in pandas. [cells]” Mr. Ryu said.
“A rat recipe is not directly applicable to other species, even within mammalian species,” he said. Pierre Comizoli“So we have to go back to the basics every time to really understand what factors might influence the reprogramming of cells,” says a germline biologist at the Smithsonian’s National Zoo and Conservation Biology Institute who was not involved in the study.
After some trial and error, Liu and his team finally figured out that introducing a cluster of specific microRNAs was key to converting fibroblasts into iPSCs. After they modified their growth conditions to include additional molecules, such as panda-specific transcription factors, the team successfully obtained iPSC clones. “The clones were beautiful,” Liu recalled. “We were so excited.”
The research team confirmed that the iPSCs they found based on their physical characteristics showed genetic characteristics related to stem cells that the researchers were looking for, such as reduced expression of genes related to somatic cells and an abundance of genes related to pluripotency.
After fine-tuning the reprogramming steps, Liu and his team set out to shorten the process and make it more efficient. After slightly adjusting the cell culture medium to include specific signaling pathway modulators, epigenetic inhibitors, and kinase blockers, they reduced the total experimental period from more than three months to less than a month, and increased efficiency by fivefold compared to unaltered medium.
The true hallmark of pluripotent stem cells is their ability to divide and form the three germ layers (endoderm, mesoderm, and ectoderm) that are essential for the development of body tissues and organs. To test the giant panda iPSCs, the team observed the formation of embryoid bodies, a collection of pluripotent stem cells that recapitulate some aspects of early embryonic development. At this stage of development, they observed an increase in ectoderm markers, while at later stages, they observed an increase in mesoderm and endoderm markers. When they injected the giant panda iPSCs into mice, the cells formed clumps that showed all three germ layers, with elements of neural, muscular, and epithelial tissue.
“You can create iPSCs, but then when you culture them, you want to turn them into something much more specialized, and that’s the challenge,” Comizoli says. “But this paper describes some really interesting culture conditions to keep them in the same state for much longer periods of time, and that’s really inspiring for the field.” But Comizoli emphasizes that just because these conditions work for giant pandas, that doesn’t mean they’ll automatically work for other species.
Liu hopes that one day, giant panda stem cells could be used to create sperm and eggs, which could then be used to create giant panda embryos. “We want to use these stem cells to create animals,” Liu said. “This is a challenging task in this field.”
According to Comizoli, scientists still have a long way to go before they can generate functional gametes from iPSCs. “The most immediate applications, he said, are regenerative medicine, treating sick pandas and better understanding the embryology, or fetal development, of these animals.”
