The giant panda ( Ailuropoda melanoleuca ) stands as a flagship and umbrella species, symbolizing global biodiversity. While traditional assisted reproductive technology faces constraints in safeguarding the genetic diversity of giant pandas, induced pluripotent stem cells (iPSCs) known for their capacity to differentiate into diverse cells types, including germ cells, present a transformative potential for conservation of endangered animals. In this study, primary fibroblast cells were isolated from the giant panda, and giant panda iPSCs (GPiPSCs) were generated using a non-integrating episomal vector reprogramming method. Characterization of these GPiPSCs revealed their state of primed pluripotency and demonstrated their potential for differentiation. Furthermore, we innovatively formulated a species-specific chemically defined FACL medium and unraveled the intricate signaling pathway networks responsible for maintaining the pluripotency and fostering cell proliferation of GPiPSCs. This study provides key insights into rare species iPSCs, offering materials for panda characteristics research and laying the groundwork for in vitro giant panda gamete generation, potentially aiding endangered species conservation.

Somatic cells can be reprogrammed into pluripotent stem cells (iPSCs) by overexpressing defined transcription factors. Specifically, overexpression of OCT4 alone has been demonstrated to reprogram mouse fibroblasts into iPSCs. However, it remains unclear whether any other single factor can induce iPSCs formation. Here, we report that SALL4 alone, under an optimized reprogramming medium iCD4, is capable of reprogramming mouse fibroblasts into iPSCs. Mechanistically, SALL4 facilitates reprogramming by inhibiting somatic genes and activating pluripotent genes, such as Esrrb and Tfap2c. Furthermore, we demonstrate that co-overexpressing SALL4 and OCT4 synergistically enhances reprogramming efficiency. Specifically, the activation of Rsk1/Esrrb/Tfap2c by SALL4, alongside OCT4’s activation of Sox2 and the suppression of Mndal by SALL4 and Sbsn by OCT4, cooperate to facilitate SALL4+OCT4-mediated reprogramming. Overall, our study not only establishes an efficient method for iPSCs induction using the SALL4 single factor but also provides insights into the synergistic effects of SALL4 and OCT4 in reprogramming.

Guinea pigs are valuable models for human disease research, yet the lack of established pluripotent stem cell lines has limited their utility. In this study, we isolate and characterize guinea pig epiblast stem cells (gpEpiSCs) from post-implantation embryos. These cells differentiate into the three germ layers, maintain normal karyotypes, and rely on FGF2 and ACTIVIN A signaling for self-renewal and pluripotency. Wingless/Integrated (WNT) signaling inhibition is also essential for their maintenance. GpEpiSCs express key pluripotency markers (OCT4, SOX2, NANOG) and share transcriptional similarities with human and mouse primed stem cells. While many genes are conserved between guinea pig and human primed stem cells, transcriptional analysis also reveals species-specific differences in pluripotency-related pathways. Epigenetic analysis highlights bivalent gene regulation, underscoring their developmental potential. This work demonstrates both the evolutionary conservation and divergence of primed pluripotent stem cells, providing a new tool for biomedical research and enhancing guinea pigs' utility in studying human diseases.

Nuclear receptors (NRs) are ligand-regulated transcription factors whose domains and dosage modulate gene networks. We systematically profiled 49 murine NRs in OKS (OCT4/KLF4/SOX2) reprogramming of mouse fibroblasts and identified the ROR subfamily as enhancers. Focusing on Rora, we uncovered a dose-dependent, biphasic effect on reprogramming: moderate Rora increases OCT4-GFP⁺ colony formation, whereas higher expression reduces colonies. Domain dissection separated these arms-DNA-binding domain (DBD)/ligand-binding domain (LBD) was required for the pro-reprogramming effect, while the N-terminal domain (NTD) was required for high-dose inhibition (ΔNTD eliminated the inhibitory limb). Functionally, the reprogramming barrier interferon (IFN)-γ was attenuated at transcript and protein levels; IFN-γ add-back dampened the enhancement, supporting immune-axis modulation. Conversely, WNT pathway output was reduced in the inhibitory arm, and CHIR99021 partially rescued the high-dose colony defect. Thus, RORA acts as a dose-programmed, domain-modular regulator that coordinates chromatin and signaling to gate cell-fate conversion, establishing nuclear-receptor dosage control as a lever to improve reprogramming efficiency.

Current clinical breakthroughs in gene therapy have brought adeno-associated virus (AAV) vectors to the forefront of gene delivery systems. Vitamin C deficiency due to GULO mutations is a genetic disorder affecting guinea pigs and humans. In our study, we used AAV9-mGULO-GT to deliver the mouse GULO gene to guinea pigs and restore Vc synthesis in affected tissues, including the liver and brain. AAV9-mGULO-GT treatment significantly improved survival rates and bone health compared to non-treated and Vc-treated groups. Dot blot analysis confirmed restored Vc content in various parts of the brain. Additionally, micro-CT imaging showcased significant enhancements in bone mineral density, content, width, and cortical thickness. Further, RNA sequencing and immunological studies of organs validated the successful restoration of Vc synthesis. These findings highlight the potential of AAV9-mGULO-GT as a therapeutic option for GULO-related scurvy and other genetic disorders. The success of our study underscores the importance of advanced targeting and gene rescue systems in developing effective therapies for genetic disorders in clinical applications.