Generation of Sheep Induced Pluripotent Stem Cells With Defined DOX-Inducible Transcription Factors via piggyBac Transposition

Induction of feline fetal fibroblasts into pluripotent stem cells using cat-derived reprogramming factors

There are few studies on the establishment of induced pluripotent stem cells (iPSCs) in cats. Although induction using heterologous reprogramming factors delivered via viral vectors has been reported, its safety and reprogramming efficiency still require improvement. In addition, the reprogramming mechanism needs further elucidation. In this study, we constructed a series of expression vectors for cat-derived reprogramming transcription factors based on the piggyBac transposon system and transfected various factor combinations into cat fetal fibroblasts (CFFs) under different electroporation conditions to generate cat iPSCs (ciPSCs). Additionally, the specific roles of these factors in reprogramming were investigated. The results showed that under the optimized electroporation conditions (DMEM/F12 buffer, 300 V, 10 ms pulse duration, 2 pulses, 25 μg plasmid DNA, and 4 mm cuvette), the survival rate and transfection efficiency of CFFs reached 64 % and 67.8 %, respectively. Based on this condition, a seven-factor combination (cOSKM + pNL + SV40 Large T) was confirmed as a better inducer for establishing ciPSCs. The obtained ciPSCs exhibit good pluripotency and passaging stability. They express stemness-related genes and proteins, and can form embryoid bodies (EBs) capable of differentiating into all three germ layers. OCT4 (O), SOX2 (S), KLF4 (K), and c-MYC (M) play important cooperative and synergistic roles in the mesenchymal-to-epithelial transition (MET) during the initial stages of reprogramming, while the supplement of NANOG (N) and LIN28 (L) can further promote MET and is important for successful reprogramming. It lays a foundation for the further breeding of cloned and genetically modified cats, and provides a tool for studying embryonic developmental diseases, screening drugs, and applying to tissue regeneration.

Construction and Influence of Induced Pluripotent Stem Cells on Early Embryo Development in Black Bone Sheep

The piggyBac+TET-on transposon induction system has a high efficiency in integrating exogenous genes in multiple cell types, can precisely integrate to reduce genomic damage, has a flexible gene expression regulation, and a strong genetic stability. When used in conjunction with somatic cell nuclear transfer experiments, it can precisely and effectively reveal the intrinsic mechanisms of early biological development. This study successfully reprogrammed black-boned sheep fibroblasts (SFs) into induced pluripotent stem cells (iPSCs) using the piggyBac+TET-on transposon system and investigated their impact on early embryonic development. Seven exogenous reprogramming factors (bovine OCT4, SOX2, KLF4, cMyc, porcine NANOG, Lin-28, and SV40 Large T) were delivered into SFs, successfully inducing iPSCs. A growth performance analysis revealed that iPSC clones exhibited a raised or flat morphology with clear edges, positive alkaline phosphatase staining, and normal karyotypes. The transcriptome analysis indicated a significant enrichment of iPSCs in oxidative phosphorylation and cell proliferation pathways, with an up-regulated expression of the ATP5B, SDHB, Bcl-2, CDK1, and Cyclin D1 genes and a down-regulated expression of BAX (p < 0.05). Somatic cell nuclear transfer experiments demonstrated that the cleavage rate (85% ± 2.12) and blastocyst rate (52% ± 2.11) of the iPSCs were significantly higher than those of the SFs (p < 0.05). The detection of trilineage marker genes confirmed that the expression levels of endoderm (DCN, NANOS3, FOXA2, FOXD3, SOX17), mesoderm (KDR, CD34, NFH), and ectoderm (NEUROD) markers in iPSCs were significantly higher than in SFs (p < 0.01). The findings demonstrate that black-boned sheep iPSCs possess pluripotency and the potential to differentiate into all three germ layers, revealing the mechanisms by which reprogrammed iPSCs influence early embryonic development and providing a critical foundation for research on sheep pluripotent stem cells.

Construction of Lentiviral Vectors Carrying Six Pluripotency Genes in Yak to Obtain Yak iPSC Cells

Yak is an excellent germplasm resource on the Tibetan Plateau and is able to live in high-altitude areas with hypoxic, cold, and harsh environments. Studies on induced pluripotent stem cells (iPSCs) in large ruminants commonly involve a combination strategy involving six transcription factors, Oct4, Sox2, Klf4, c-Myc, Nanog, and Lin28 (OSKMNL). This strategy tends to utilize genes from the same species to optimize pluripotency maintenance. In this study, we cloned the six pluripotency genes (OSKMNL) from yak and constructed a multi-cistronic lentiviral vector carrying these genes. This vector efficiently delivered the genes into yak fibroblasts, aiming to promote the reprogramming process. We verified that the treated cells had several pluripotency characteristics, marking the first successful construction of a lentiviral system carrying yak pluripotency genes. This achievement lays the foundation for subsequent establishment of yak iPSCs and holds significant implications for yak-breed improvement and germplasm-resource conservation.

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.

Establishment of African pygmy mouse induced pluripotent stem cells using defined doxycycline inducible transcription factors

Mus minutoides is one of the smallest mammals worldwide; however, the regulatory mechanisms underlying its dwarfism have not been examined. Therefore, we aimed to establish M. minutoides induced pluripotent stem cells (iPSCs) using the PiggyBac transposon system for applications in developmental engineering. The established M. minutoides iPSCs were found to express pluripotency markers and could differentiate into neurons. Based on in vitro differentiation analysis, M. minutoides iPSCs formed embryoid bodies expressing marker genes in all three germ layers. Moreover, according to the in vivo analysis, these cells contributed to the formation of teratoma and development of chimeric mice with Mus musculus. Overall, the M. minutoides iPSCs generated in this study possess properties that are comparable to or closely resemble those of naïve pluripotent stem cells (PSCs). These findings suggest these iPSCs have potential utility in various analytical applications, including methods for blastocyst completion.

Lab partners: oocytes, embryos and company. A personal view on aspects of oocyte maturation and the development of monozygotic twins

The present review addresses the oocyte and the preimplantation embryo, and is intended to highlight the underlying principle of the "nature versus/and nurture" question. Given the diversity in mammalian oocyte maturation, this review will not be comprehensive but instead will focus on the porcine oocyte. Historically, oogenesis was seen as the development of a passive cell nursed and determined by its somatic compartment. Currently, the advanced analysis of the cross-talk between the maternal environment and the oocyte shows a more balanced relationship: Granulosa cells nurse the oocyte, whereas the latter secretes diffusible factors that regulate proliferation and differentiation of the granulosa cells. Signal molecules of the granulosa cells either prevent the precocious initiation of meiotic maturation or enable oocyte maturation following hormonal stimulation. A similar question emerges in research on monozygotic twins or multiples: In Greek and medieval times, twins were not seen as the result of the common course of nature but were classified as faults. This seems still valid today for the rare and until now mainly unknown genesis of facultative monozygotic twins in mammals. Monozygotic twins are unique subjects for studies of the conceptus-maternal dialogue, the intra-pair similarity and dissimilarity, and the elucidation of the interplay between nature and nurture. In the course of in vivo collections of preimplantation sheep embryos and experiments on embryo splitting and other microsurgical interventions we recorded observations on double blastocysts within a single zona pellucida, double inner cell masses in zona-enclosed blastocysts and double germinal discs in elongating embryos. On the basis of these observations we add some pieces to the puzzle of the post-zygotic genesis of monozygotic twins and on maternal influences on the developing conceptus.

Induced pluripotent stem cells from domesticated ruminants and their potential for enhancing livestock production

Ruminant livestock, including cattle, sheep, goat, and buffalo, are essential for global food security and serve valuable roles in sustainable agricultural systems. With the limited availability of embryonic stem cells (ESCs) from these species, ruminant induced pluripotent stem cells (iPSCs) and iPSC-like cells provide a valuable research tool for agricultural, veterinary, biomedical, and pharmaceutical applications, as well as for the prospect of translation to human medicine. iPSCs are generated by reprogramming of adult or fetal cells to an ESC-like state by ectopic expression of defined transcription factors. Despite the slow pace the field has evolved in livestock species compared to mice and humans, significant progress has been made over the past 15 years in using different cell sources and reprogramming protocols to generate iPSCs/iPSC-like cells from ruminants. This mini review summarizes the current literature related to the derivation of iPSCs/iPSC-like cells from domesticated ruminants with a focus on reprogramming protocols, characterization, associated limitations, and potential applications in ruminant basic science research and production.