Induced pluripotent stem cells and cerebral organoids from the critically endangered Sumatran rhinoceros

Application of induced pluripotent stem cells in the conservation of endangered animals

The accelerating biodiversity crisis urgently demands innovative approaches that transcend traditional conservation strategies, which are often constrained by genetic bottlenecks and disease risks. Induced pluripotent stem cells (iPSCs) technology emerges as a transformative solution, enabling non-invasive genetic preservation and multi-pathway species recovery. This review synthesizes advances in reprogramming somatic cells from endangered species into iPSCs through integration-free strategies, such as mRNA, Sendai virus, episomal systems, adenoviruses and chemical induction, thereby reducing genomic instability. We highlight breakthroughs in differentiating iPSCs into functional gametes for assisted reproduction and blastoids formation for embryonic reconstruction, circumventing donor oocyte dependency and genetic homogeneity risks. Despite challenges in lineage specification and epigenetic fidelity, combining iPSC biobanking with ecosystem management enables large-scale genetic rescue. By combining these technologies with ethical frameworks and habitat restoration, the plasticity of cells may be transformed into population resilience, potentially redefining biodiversity conservation.

Progress Toward Genetic Rescue of the Northern White Rhinoceros (Ceratotherium simum cottoni)

The northern white rhinoceros (NWR) is functionally extinct, with only two nonreproductive females remaining. However, because of the foresight of scientists, cryopreserved cells and reproductive tissues may aid in the recovery of this species. An ambitious program of natural and artificial gametes and in vitro embryo generation was first outlined in 2015, and many of the proposed steps have been achieved. Multiple induced pluripotent stem cell lines have been established, primordial germ cell-like cells have been generated, oocytes have been collected from the remaining females, blastocysts have been cryopreserved, and the closely related southern white rhinoceros (SWR) is being established as a surrogate. Recently, the first successful embryo transfer in SWR demonstrated that embryos can be generated by in vitro fertilization and cryopreserved. We explore progress to date in using advanced cellular technologies to save the NWR and highlight the necessary next steps to ensure a viable population for reintroduction. We roll out a holistic rescue approach for a charismatic megavertebrate that includes the most advanced cellular technologies, which can provide a blueprint for other critically endangered mammals. We also provide a detailed discussion of the remaining questions in such an upgraded conservation program.

Unraveling mechanisms of human brain evolution

Evolutionary changes in human brain structure and function have enabled our specialized cognitive abilities. How these changes have come about genetically and functionally has remained an open question. However, new methods are providing a wealth of information about the genetic, epigenetic, and transcriptomic differences that set the human brain apart. Combined with in vitro models that allow access to developing brain tissue and the cells of our closest living relatives, the puzzle pieces are now coming together to yield a much more complete picture of what is actually unique about the human brain. The challenge now will be linking these observations and making the jump from correlation to causation. However, elegant genetic manipulations are now possible and, when combined with model systems such as organoids, will uncover a mechanistic understanding of how evolutionary changes at the genetic level have led to key differences in development and function that enable human cognition.

Advancing stem cell technologies for conservation of wildlife biodiversity

Wildlife biodiversity is essential for healthy, resilient and sustainable ecosystems. For biologists, this diversity also represents a treasure trove of genetic, molecular and developmental mechanisms that deepen our understanding of the origins and rules of life. However, the rapid decline in biodiversity reported recently foreshadows a potentially catastrophic collapse of many important ecosystems and the associated irreversible loss of many forms of life on our planet. Immediate action by conservationists of all stripes is required to avert this disaster. In this Spotlight, we draw together insights and proposals discussed at a recent workshop hosted by Revive & Restore, which gathered experts to discuss how stem cell technologies can support traditional conservation techniques and help protect animal biodiversity. We discuss reprogramming, in vitro gametogenesis, disease modelling and embryo modelling, and we highlight the prospects for leveraging stem cell technologies beyond mammalian species.

Advanced assisted reproduction technologies in endangered mammalian species

A new synergistic approach of classical conservation strategies combined with advanced assisted reproduction technologies (aART) allows for protection and rescue of endangered keystone species at the brink of extinction, which can help to safeguard complex ecosystems. Reproduction biology and management in mammal species is not only challenging in regards to their diverging sizes, anatomy, and often unknown physiology; it also requires customized training or chemical restraint protocols for safe handling. Besides these general challenges, there are several new assisted reproduction techniques (ART) specifically tailored to critically endangered mammals. The current portfolio of ART in these mammalian taxa is ranging from sexual cycle characterization and manipulation, semen collection and cryopreservation, artificial insemination, biobanking of living cells, oocyte collection, in vitro fertilization (IVF), and embryo production, embryo transfer as well as stem cell-derived in vitro gametogenesis for generating gametes in culture. The article covers advanced assisted reproduction technologies (aART), success and challenges, as well as ethical implications.

Generation and characterization of giant panda induced pluripotent stem cells

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.

A Standardized Nomenclature Design for Systematic Referencing and Identification of Animal Cellular Material

The documentation, preservation and rescue of biological diversity increasingly uses living biological samples. Persistent associations between species, biosamples, such as tissues and cell lines, and the accompanying data are indispensable for using, exchanging and benefiting from these valuable materials. Explicit authentication of such biosamples by assigning unique and robust identifiers is therefore required to allow for unambiguous referencing, avoid identification conflicts and maintain reproducibility in research. A predefined nomenclature based on uniform rules would facilitate this process. However, such a nomenclature is currently lacking for animal biological material. We here present a first, standardized, human-readable nomenclature design, which is sufficient to generate unique and stable identifying names for animal cellular material with a focus on wildlife species. A species-specific human- and machine-readable syntax is included in the proposed standard naming scheme, allowing for the traceability of donated material and cultured cells, as well as data FAIRification. Only when it is consistently applied in the public domain, as publications and inter-institutional samples and data are exchanged, distributed and stored centrally, can the risks of misidentification and loss of traceability be mitigated. This innovative globally applicable identification system provides a standard for a sustainable structure for the long-term storage of animal bio-samples in cryobanks and hence facilitates current as well as future species conservation and biomedical research.

The impact of induced pluripotent stem cells in animal conservation

It is widely acknowledged that we are currently facing a critical tipping point with regards to global extinction, with human activities driving us perilously close to the brink of a devastating sixth mass extinction. As a promising option for safeguarding endangered species, induced pluripotent stem cells (iPSCs) hold great potential to aid in the preservation of threatened animal populations. For endangered species, such as the northern white rhinoceros (Ceratotherium simum cottoni), supply of embryos is often limited. After the death of the last male in 2019, only two females remained in the world. IPSC technology offers novel approaches and techniques for obtaining pluripotent stem cells (PSCs) from rare and endangered animal species. Successful generation of iPSCs circumvents several bottlenecks that impede the development of PSCs, including the challenges associated with establishing embryonic stem cells, limited embryo sources and immune rejection following embryo transfer. To provide more opportunities and room for growth in our work on animal welfare, in this paper we will focus on the progress made with iPSC lines derived from endangered and extinct species, exploring their potential applications and limitations in animal welfare research.

Efficient derivation of transgene-free porcine induced pluripotent stem cells enables in vitro modeling of species-specific developmental timing

Sus scrofa domesticus (pig) has served as a superb large mammalian model for biomedical studies because of its comparable physiology and organ size to humans. The derivation of transgene-free porcine induced pluripotent stem cells (PiPSCs) will, therefore, benefit the development of porcine-specific models for regenerative biology and its medical applications. In the past, this effort has been hampered by a lack of understanding of the signaling milieu that stabilizes the porcine pluripotent state in vitro. Here, we report that transgene-free PiPSCs can be efficiently derived from porcine fibroblasts by episomal vectors along with microRNA-302/367 using optimized protocols tailored for this species. PiPSCs can be differentiated into derivatives representing the primary germ layers in vitro and can form teratomas in immunocompromised mice. Furthermore, the transgene-free PiPSCs preserve intrinsic species-specific developmental timing in culture, known as developmental allochrony. This is demonstrated by establishing a porcine in vitro segmentation clock model that, for the first time, displays a specific periodicity at ∼3.7 h, a timescale recapitulating in vivo porcine somitogenesis. We conclude that the transgene-free PiPSCs can serve as a powerful tool for modeling development and disease and developing transplantation strategies. We also anticipate that they will provide insights into conserved and unique features on the regulations of mammalian pluripotency and developmental timing mechanisms.

Generation of a human induced pluripotent stem cell line (UMGACBi001-A) from urine cells of a chronic kidney disease patient with hypertension, diabetic nephropathy and acute sepsis

Chronic kidney disease is a major public health burden associated with a drastically reduced quality of living and life span that lacks suitable, individualized therapeutic strategies. Here we present a human induced pluripotent stem cell line (iPSC, UMGACBi001-A) reprogrammed from urine cells of an acute septic dialysis patient suffering from chronic kidney disease using non-integrating administration of RNAs. The generated iPSCs were positively characterized for typical morphology, pluripotency marker expression, directed differentiation potential, non-contamination, chromosomal consistency and donor identity. This iPSC-line can be a useful source for in vitro disease modelling and individualized therapeutic approaches.

Induced pluripotent stem cells in companion animals: how can we move the field forward?

Following a one medicine approach, the development of regenerative therapies for human patients leads to innovative treatments for animals, while pre-clinical studies on animals provide knowledge to advance human medicine. Among many different biological products under investigation, stem cells are among the most prominent. Mesenchymal stromal cells (MSCs) are extensively investigated, but they present challenges such as senescence and limited differentiation ability. Embryonic stem cells (ESCs) are pluripotent cells with a virtually unlimited capacity for self-renewal and differentiation, but the use of embryos carries ethical concerns. Induced pluripotent stem cells (iPSCs) can overcome all of these limitations, as they closely resemble ESCs but are derived from adult cells by reprogramming in the laboratory using pluripotency-associated transcription factors. iPSCs hold great potential for applications in therapy, disease modeling, drug screening, and even species preservation strategies. However, iPSC technology is less developed in veterinary species compared to human. This review attempts to address the specific challenges associated with generating and applying iPSCs from companion animals. Firstly, we discuss strategies for the preparation of iPSCs in veterinary species and secondly, we address the potential for different applications of iPSCs in companion animals. Our aim is to provide an overview on the state of the art of iPSCs in companion animals, focusing on equine, canine, and feline species, as well as to identify which aspects need further optimization and, where possible, to provide guidance on future advancements. Following a "step-by-step" approach, we cover the generation of iPSCs in companion animals from the selection of somatic cells and the reprogramming strategies, to the expansion and characterization of iPSCs. Subsequently, we revise the current applications of iPSCs in companion animals, identify the main hurdles, and propose future paths to move the field forward. Transferring the knowledge gained from human iPSCs can increase our understanding in the biology of pluripotent cells in animals, but it is critical to further investigate the differences among species to develop specific approaches for animal iPSCs. This is key for significantly advancing iPSC application in veterinary medicine, which at the same time will also allow gaining pre-clinical knowledge transferable to human medicine.