A virus-free poly-promoter vector induces pluripotency in quiescent bovine cells under chemically defined conditions of dual kinase inhibition

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.

Acquisition and maintenance of pluripotency are influenced by fibroblast growth factor, leukemia inhibitory factor, and 2i in bovine-induced pluripotent stem cells

Several opportunities for embryo development, stem cell maintenance, cell fate, and differentiation have emerged using induced pluripotent stem cells (iPSCs). However, the difficulty in comparing bovine iPSCs (biPSCs) with embryonic stem cells (ESCs) was a challenge for many years. Here, we reprogrammed fetal fibroblasts by transient expression of the four transcription factors (Oct4, Sox2, Klf4, and c-Myc, collectively termed “OSKM” factors) and cultured in iPSC medium, supplemented with bFGF, bFGF2i, leukemia inhibitory factor (LIF), or LIF2i, and then compared these biPSC lines with bESC to evaluate the pluripotent state. biPSC lines were generated in all experimental groups. Particularly, reprogrammed cells treated with bFGF were more efficient in promoting the acquisition of pluripotency. However, LIF2i treatment did not promote continuous self-renewal. biPSCs (line 2) labeled with GFP were injected into early embryos (day 4.5) to assess the potential to contribute to chimeric blastocysts. The biPSC lines show a pluripotency state and are differentiated into three embryonic layers. Moreover, biPSCs and bESCs labeled with GFP were able to contribute to chimeric blastocysts. Additionally, biPSCs have shown promising potential for contributing to chimeric blastocysts and for future studies.

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

Pluripotent stem cells (PSCs) have the potential to differentiate to all cell types of an adult individual and are useful for studying mammalian development. Establishing induced pluripotent stem cells (iPSCs) capable of expressing pluripotent genes and differentiating to three germ layers will not only help to explain the mechanisms underlying somatic reprogramming but also lay the foundation for the establishment of sheep embryonic stem cells (ESCs) in vitro. In this study, sheep somatic cells were reprogrammed in vitro into sheep iPSCs with stable morphology, pluripotent marker expression, and differentiation ability, delivered by piggyBac transposon system with eight doxycycline (DOX)-inducible exogenous reprogramming factors: bovine OCT4, SOX2, KLF4, cMYC, porcine NANOG, human LIN28, SV40 large T antigen, and human TERT. Sheep iPSCs exhibited a chimeric contribution to the early blastocysts of sheep and mice and E6.5 mouse embryos in vitro. A transcriptome analysis revealed the pluripotent characteristics of somatic reprogramming and insights into sheep iPSCs. This study provides an ideal experimental material for further study of the construction of totipotent ESCs in sheep.

Large-scale cultured meat production: Trends, challenges and promising biomanufacturing technologies

Food systems of the future will need to face an increasingly clear reality - that a protein-rich diet is essential for good health, but traditional meat products will not suffice to ensure safety, sustainability, and equity of food supply chains at a global scale. This paper provides an in-depth analysis of bioprocess technologies needed for cell-based meat production and challenges in reaching commercial scale. Specifically, it reviews state-of-the-art bioprocess technologies, current limitations, and opportunities for research across four domains: cell line development, cell culture media, scaffolding, and bioreactors. This also includes exploring innovations to make cultured meat a viable protein alternative across numerous key performance indicators and for specific applications where traditional livestock is not an option (e.g., local production, space exploration). The paper explores tradeoffs between production scale, product quality, production cost, and footprint over different time horizons. Finally, a discussion explores various factors that may impact the ability to successfully scale and market cultured meat products: social acceptance, environmental tradeoffs, regulatory guidance, and public health benefits. While the exact nature of the transition from traditional livestock to alternative protein products is uncertain, it has already started and will likely continue to build momentum in the next decade.

RNA-seq of buffalo fibroblasts over-expressed pluripotent-related genes to investigate characteristics of its preliminarily reprogrammed stage

Induced pluripotent stem cells (iPSCs) can enhance the efficiency of buffalo genetic improvements because of their differentiation potential and proliferation ability, which are similar to those of embryonic stem cells. However, very few studies have focussed on buffalo iPSCs, and a stable induction system has not been established for buffalo somatic cell reprogramming. In this study, we constructed a PiggyBac transposon vector co-expressing buffalo OCT4, C-MYC, KLF4 and SOX2 genes (PB_OMKS) separated by the nucleotide sequence of three 2A peptides and established the buffalo foetal skin fibroblast (BFSF) cell line BFSF_OMKS. RNA-seq technology and bioinformatics analysis methods were mainly employed to perform a transcriptome analysis between BFSF and BFSF_OMKS. The results revealed that over-expression of OCT4, C-MYC, KLF4 and SOX2 in BFSFs led to the activation of reprogramming-related LIF, activin, BMP4, SMAD1/5/9 and Wnt signals. These results increased our understanding of buffalo somatic cell reprogramming mechanisms and could provide a possible theory for the selection of small-molecule cocktails to promote reprogramming.

Efficient induction and sustenance of pluripotent stem cells from bovine somatic cells

Although derivation of naïve bovine embryonic stem cells is unachieved, the possibility for generation of bovine induced pluripotent stem cells (biPSCs) has been generally reported. However, attempts to sustain biPSCs by promoting self-renewal have not been successful. Methods established for maintaining murine and human induced pluripotent stem cells (iPSCs) do not support self-renewal of iPSCs for any bovid species. In this study, we examined methods to enhance complete reprogramming and concurrently investigated signaling relevant to pluripotency of the bovine blastocyst inner cell mass (ICM). First, we identified that forced expression of SV40 large T antigen together with the reprogramming genes (OCT4, SOX2, KLF4 and MYC) substantially enhanced the reprogramming efficacy of bovine fibroblasts to biPSCs. Second, we uncovered that TGFβ signaling is actively perturbed in the ICM. Inhibition of ALK4/5/7 to block TGFβ/activin/nodal signaling together with GSK3β and MEK1/2 supported robust in vitro self-renewal of naïve biPSCs with unvarying colony morphology, steady expansion, expected pluripotency gene expression and committed differentiation plasticity. Core similarities between biPSCs and stem cells of the 16-cell-stage bovine embryo indicated a stable ground state of pluripotency; this allowed us to reliably gain predictive understanding of signaling in bovine pluripotency using systems biology approaches. Beyond defining a high-fidelity platform for advancing biPSC-based biotechnologies that have not been previously practicable, these findings also represent a significant step towards understanding corollaries and divergent aspects of bovine pluripotency.

This article has an associated First Person interview with the joint first authors of the paper.

Summary: Pluripotency reprogramming by overcoming the stable epigenome of bovine cells, and uncovering precise early embryo self-renewal mechanisms enables sustenance and expansion of authentic induced pluripotent stem cells in vitro.

Cattle In Vitro Induced Pluripotent Stem Cells Generated and Maintained in 5 or 20% Oxygen and Different Supplementation

The event of cellular reprogramming into pluripotency is influenced by several factors, such as in vitro culture conditions (e.g., culture medium and oxygen concentration). Herein, bovine iPSCs (biPSCs) were generated in different levels of oxygen tension (5% or 20% of oxygen) and supplementation (bFGF or bFGF + LIF + 2i-bFL2i) to evaluate the efficiency of pluripotency induction and maintenance in vitro. Initial reprogramming was observed in all groups and bFL2i supplementation initially resulted in a superior number of colonies. However, bFL2i supplementation in low oxygen led to a loss of self-renewal and pluripotency maintenance. All clonal lines were positive for alkaline phosphatase; they expressed endogenous pluripotency-related genes SOX2, OCT4 and STELLA. However, expression was decreased throughout the passages without the influence of oxygen tension. GLUT1 and GLUT3 were upregulated by low oxygen. The biPSCs were immunofluorescence-positive stained for OCT4 and SOX2 and they formed embryoid bodies which differentiated in ectoderm and mesoderm (all groups), as well as endoderm (one line from bFL2i in high oxygen). Our study is the first to compare high and low oxygen environments during and after induced reprogramming in cattle. In our conditions, a low oxygen environment did not favor the pluripotency maintenance of biPSCs.

Strategy to Establish Embryo-Derived Pluripotent Stem Cells in Cattle

Stem cell research is essential not only for the research and treatment of human diseases, but also for the genetic preservation and improvement of animals. Since embryonic stem cells (ESCs) were established in mice, substantial efforts have been made to establish true ESCs in many species. Although various culture conditions were used to establish ESCs in cattle, the capturing of true bovine ESCs (bESCs) has not been achieved. In this review, the difficulty of establishing bESCs with various culture conditions is described, and the characteristics of proprietary induced pluripotent stem cells and extended pluripotent stem cells are introduced. We conclude with a suggestion of a strategy for establishing true bESCs.

Perspectives of pluripotent stem cells in livestock

The recent progress in derivation of pluripotent stem cells (PSCs) from farm animals opens new approaches not only for reproduction, genetic engineering, treatment and conservation of these species, but also for screening novel drugs for their efficacy and toxicity, and modelling of human diseases. Initial attempts to derive PSCs from the inner cell mass of blastocyst stages in farm animals were largely unsuccessful as either the cells survived for only a few passages, or lost their cellular potency; indicating that the protocols which allowed the derivation of murine or human embryonic stem (ES) cells were not sufficient to support the maintenance of ES cells from farm animals. This scenario changed by the innovation of induced pluripotency and by the development of the 3 inhibitor culture conditions to support naïve pluripotency in ES cells from livestock species. However, the long-term culture of livestock PSCs while maintaining the full pluripotency is still challenging, and requires further refinements. Here, we review the current achievements in the derivation of PSCs from farm animals, and discuss the potential application areas.

Generation of transgene-free induced pluripotent stem cells from cardiac fibroblasts of goat embryos

Induced pluripotent stem cells (iPSCs) hold a great potential for therapeutic regenerative medicine. The aim of this study was to generate induced pluripotent stem cells from goat embryonic cardiac tissue derived fibroblasts. The isolated cardiac fibroblasts from the cardiac tissue of goat embryos were positive for alfa smooth muscle actin, vimentin and discoidin domain receptor2. From these cells, we generated transgene free iPSCs using piggyBac transposons / transposase using five transcription factors (Oct4, Sox2, Klf, Myc and Lin 28). The generated iPSCs were SSEA1, SSEA4 and Oct4 positive. They were cultured on neofeeders using 20% Serum replacement - IMDM with bFGF. They could form cystic and compact embryoid bodies that showed differentiated ectodermal and mesodermal like cells when cultured using 20% FBS-IMDM without bFGF. The iPSCs, generated in the frame of this approach were produced without the use of integrating virus and the reprogramming transgenes were removed at the end of the process. Though there were limitations in the approach used, a substantial sign of reprogramming was obtained.

Anatomical templates for tissue (re)generation and beyond

Induced pluripotent stem cells (iPSCs) represent a valuable alternative to stem cells in regenerative medicine overcoming their ethical limitations, like embryo disruption. Takahashi and Yamanaka in 2006 reprogrammed, for the first time, mouse fibroblasts into iPSCs through the retroviral delivery of four reprogramming factors: Oct3/4, Sox2, c-Myc, and Klf4. Since then, several studies started reporting the derivation of iPSC lines from animals other than rodents for translational and veterinary medicine. Here, we review the potential of using these cells for further intriguing applications, such as "cellular agriculture." iPSCs, indeed, can be a source of in vitro, skeletal muscle tissue, namely "cultured meat," a product that improves animal welfare and encourages the consumption of healthier meat along with environmental preservation. Also, we report the potential of using iPSCs, obtained from endangered species, for therapeutic treatments for captive animals and for assisted reproductive technologies as well. This review offers a unique opportunity to explore the whole spectrum of iPSC applications from regenerative translational and veterinary medicine to the production of artificial meat and the preservation of currently endangered species.

Generation of induced pluripotent stem cells from large domestic animals

BACKGROUND

Induced pluripotent stem cells (iPSCs) have enormous potential in developmental biology studies and in cellular therapies. Although extensively studied and characterized in human and murine models, iPSCs from animals other than mice lack reproducible results.

METHODS

Herein, we describe the generation of robust iPSCs from equine and bovine cells through lentiviral transduction of murine or human transcription factors Oct4, Sox2, Klf4, and c-Myc and from human and murine cells using similar protocols, even when different supplementations were used. The iPSCs were analyzed regarding morphology, gene and protein expression of pluripotency factors, alkaline phosphatase detection, and spontaneous and induced differentiation.

RESULTS

Although embryonic-derived stem cells are yet not well characterized in domestic animals, generation of iPS cells from these species is possible through similar protocols used for mouse or human cells, enabling the use of pluripotent cells from large animals for basic or applied purposes. Herein, we also infer that bovine iPS (biPSCs) exhibit similarity to mouse iPSCs (miPSCs), whereas equine iPSs (eiPSCs) to human (hiPSCs).

CONCLUSIONS

The generation of reproducible protocols in different animal species will provide an informative tool for producing in vitro autologous pluripotent cells from domestic animals. These cells will create new opportunities in animal breeding through transgenic technology and will support a new era of translational medicine with large animal models.

Media switching at different time periods affects the reprogramming efficiency of buffalo fetal fibroblasts

Many contrasting reports are available on generation of bovine induced pluripotent stem cells (iPSCs) employing different timelines and culture conditions which signifies reprogramming process varies between species and cell types. The present study determines an optimum time period required to re-initiate reprogramming events in buffalo fibroblasts after introduction of exogenous genes (OCT4, SOX2, KLF4 and c-MYC) by lentiviral vector. The reprogramming efficiency is cumulative result of many factors including culture conditions and addition of growth factors in culture media. In our study, we observed when stem cell culture conditions were provided Day 5 post-transduction, it results in maximum reprogramming efficiency in comparison when same conditions were provided too early or on later days. The putative iPSCs were expanded on feeder layer for 15 passages and found positive for alkaline phosphatase and pluripotency markers (OCT4, SOX2, KLF4, c-MYC, UTF, TELOMERASE, FOXD3, REX1, STAT3, NUCLEOSTAMIN and TRA1-81). Also, they produced embryoid bodies showing expression for ectodermal (NF68, MOBP), mesodermal (ASA, BMP4) and endodermal (GATA4, AFP) markers to confirm their pluripotent nature. Our results suggest that reprogramming is accompanied by time dependent events and providing stem cell culture conditions at definite time during reprogramming can help in generation of iPSCs with greater efficiency.

Induced pluripotent stem cells throughout the animal kingdom: Availability and applications

Up until the mid 2000s, the capacity to generate every cell of an organism was exclusive to embryonic stem cells. In 2006, researchers Takahashi and Yamanaka developed an alternative method of generating embryonic-like stem cells from adult cells, which they coined induced pluripotent stem cells (iPSCs). Such iPSCs possess most of the advantages of embryonic stem cells without the ethical stigma associated with derivation of the latter. The possibility of generating “custom-made” pluripotent cells, ideal for patient-specific disease models, alongside their possible applications in regenerative medicine and reproduction, has drawn a lot of attention to the field with numbers of iPSC studies published growing exponentially. IPSCs have now been generated for a wide variety of species, including but not limited to, mouse, human, primate, wild felines, bovines, equines, birds and rodents, some of which still lack well-established embryonic stem cell lines. The paucity of robust characterization of some of these iPSC lines as well as the residual expression of transgenes involved in the reprogramming process still hampers the use of such cells in species preservation or medical research, underscoring the requirement for further investigations. Here, we provide an extensive overview of iPSC generated from a broad range of animal species including their potential applications and limitations.

Induced pluripotent stem cell generation from bovine somatic cells indicates unmet needs for pluripotency sustenance

Mechanisms that direct reprogramming of differentiated somatic cells to induced pluripotent stem cells (iPSCs), albeit incomplete in understanding, are highly conserved across all mammalian species studied. Equally, proof of principle that iPSCs can be derived from domestic cattle has been reported in several publications. In our efforts to derive and study bovine iPSCs, we encountered inadequacy of methods to generate, sustain, and characterize these cells. Our results suggest that iPSC protocols optimized for mouse and human somatic cells do not effectively translate to bovine somatic cells, which show some refractoriness to reprogramming that also affects sustenance. Moreover, methods that enhance reprogramming efficiency in mouse and human cells had no effect on improving bovine cell reprogramming. Although use of retroviral vectors coding for bovine OCT4, SOX2, KLF4, cMYC, and NANOG appeared to produce consistent iPSC-like cells from both fibroblasts and cells from the Wharton's jelly, these colonies could not be sustained. Use of bovine genes could successfully reprogram both mouse and human cells. These findings indicated either incomplete reprogramming and/or discordant/inadequate culture conditions for bovine pluripotent stem cells. Therefore, additional studies that advance core knowledge of bovine pluripotency are necessary before any anticipated iPSC-driven bovine technologies can be realized.

The modification of mitochondrial energy metabolism and histone of goat somatic cells under small molecules compounds induction

In recent years, induced pluripotent stem cells (iPSCs) technique is able to allow us to generate pluripotency from somatic cells in vitro through the over expression of several transcription factors. Normally, viral vectors and transcription factors are commonly used on iPSC technique, which could cause many barriers on further application. In this study, we attempt to process a new method to obtain pluripotency from goat somatic cells in vitro under fully chemically defined condition. The results showed that chemically induced pluripotent stem cells-like cells (CiPSC-like cells) colonies were generated from goat ear fibroblasts by fully small-molecule compounds. Those three dimensions colonies were similar with mouse iPSCs in morphology and had strong positive alkaline phosphatase (AP) activity and expressed pluripotency related genes OCT4, SOX2, NANOG, CDH1, TDGF, GDF3, DAX1, REX1, which determined by RT-PCR. Those colonies could also differentiate into different cell types derived from three germ layers proved by RT-PCR and immunofluorescence assays. The expression of glycolysis-related genes about PGAM1, KPYM2 and HXK2 in CiPSC-like colonies formation groups was significantly higher than their parental fibroblasts, but not in the non-CiPSC-like colonies formation group. The expression of histone acetylation and methylation-related genes, HAT1 and SMYD3, was not significantly up-regulated within different groups compared to their parental fibroblasts, respectively. Yet, the expression of histone methylation-related gene, KDM5B, was significantly up-regulated on the cells from non-colonies formation group compared to parental fibroblasts, but the expression of KDM5B of the cells from CiPSC-like cell colonies was not significantly difference compared to that of parental fibroblasts. In conclusion, this is the first report that CiPSC-like cells could be generated in vitro from goat rather than just mouse under fully chemically defined condition. The generation of CiPSC-like colonies may be depended on the correct modification of energy metabolism and histone epigenetic during the reprogramming, rather than just the over-expression of those pluripotency-related genes. This study will strongly support us to further establish the stable goat CiPSC lines without any integration of exogenous genes.

Transposon mediated reprogramming of buffalo fetal fibroblasts to induced pluripotent stem cells in feeder free culture conditions

Commonly, induced pluripotent stem (iPS) cells are generated by viral transduction of four core reprogramming genes, but recent evidences suggest that slightly different combination of transcription factors improve the efficiency and quality of generated iPS cells. However, vectors like retro- and lentiviral may cause insertional mutagenesis due to its integrating ability. Hence, alternate methods with safety concerns are needed to be investigated. Therefore, the present study was undertaken to reprogram buffalo fibroblasts using non-viral piggyBac (PB) transposon mediated transfer of six transcription factors. To generate buffalo iPS cells, fibroblasts were isolated from buffalo fetus at passage 2. The cells were co-electroporated with a PB transposon having CAGGS promoter driven cassette of Oct4, Sox2, Klf4, cMyc, Nanog, and Lin28 transcription factors separated by self-cleaving 2A peptide and a helper plasmid pCMV-PB transposase. After 12-14 days post electroporation, fibroblast cells morphology was observed to change to round structures which formed loose aggregates of cells on day 18. Putative iPS cell colonies were propagated in feeder free system and characterized through expression of pluripotency markers such as alkaline phosphatase, SSEA-1, SSEA-4, SSEA-5, TRA-1-81, Oct4, Nanog and Sox2 and endogenous genes supported the stemness property of the generated cells. These cells differentiated in vitro to form embryoid bodies and were found to express three germ layers markers. In conclusion, generation of buffalo iPS cells using transposon system provides insights into viral-free iPS technology which will facilitate genetic modification of the buffalo genome and help in the production of transgenic animals using genetically modified iPS cells.

Generation of transgene-free porcine intermediate type induced pluripotent stem cells

Physiologically and anatomically, humans and pigs share many similarities, which make porcine induced pluripotent stem cells (piPSCs) very attractive for modeling human cell therapy as well as for testing safety of iPSC based cell replacement therapies. To date, several integrative and non-integrative strategies have been reported to successfully generate piPSCs, but all resulting piPSCs had integration of transgenes. The use of integrative methods has the disadvantage of potential lack of silencing or inappropriate re-activation of these genes during differentiation, as well as uncertainty regarding disruption of important genomic regions caused by integration. In our study, we performed a non-integrative vector based reprogramming approach using porcine fetal fibroblasts. The resulting four piPSC lines were positive for pluripotency marker and when subjected to in vitro and in vivo differentiation assays, all four lines formed embryoid bodies, capable to differentiate into all three germ layers, and three out of the four cell lines formed teratomas. PCR analysis on genomic and plasmid DNA revealed that the episomal vectors were undetectable in six out of eight subclones derived from one of the piPSC lines (piPSC1) above passage 20. These piPSCs could potentially be ideal cell lines for the generation of porcine in vitro and in vivo models. Furthermore, subsequent analyses of our new transgene independent piPSCs could provide novel insights on the genetic and epigenetic necessities to achieve and maintain piPSCs.

Silencing of retrotransposon-derived imprinted gene RTL1 is the main cause for postimplantational failures in mammalian cloning

Substantial rates of fetal loss plague all in vitro procedures involving embryo manipulations, including human-assisted reproduction, and are especially problematic for mammalian cloning where over 90% of reconstructed nuclear transfer embryos are typically lost during pregnancy. However, the epigenetic mechanism of these pregnancy failures has not been well described. Here we performed methylome and transcriptome analyses of pig induced pluripotent stem cells and associated cloned embryos, and revealed that aberrant silencing of imprinted genes, in particular the retrotransposon-derived RTL1 gene, is the principal epigenetic cause of pregnancy failure. Remarkably, restoration of RTL1 expression in pig induced pluripotent stem cells rescued fetal loss. Furthermore, in other mammals, including humans, low RTL1 levels appear to be the main epigenetic cause of pregnancy failure.

Exogenous human OKSM factors maintain pluripotency gene expression of bovine and porcine iPS-like cells obtained with STEMCCA delivery system

OBJECTIVES

The use of induced pluripotent stem (iPS) cells as an alternative to embryonic stem cells to produce transgenic animals requires the development of a biotechnological platform for their generation. In this study, different strategies for the generation of bovine and porcine iPS cells were evaluated. Lentiviral vectors were used to deliver human factors OCT4, SOX2, KLF4 and c-MYC (OKSM) into bovine and porcine embryonic fibroblasts and different culture conditions were evaluated.

RESULTS

Protocols based on the integrative lentiviral vector STEMCCA produced porcine iPS-like cells more efficiently than in bovine cells. The iPS-like cells generated displayed stem cell features; however, expression of exogenous factors was maintained along at least 12 passages. Since inactivation of the exogenous factors is still a major bottleneck for establishing fully reprogrammed iPS cells, defining culture conditions that support endogenous OKSM expression is critical for the efficient generation of farm animals' iPS cells.

Naked Mole Rat Induced Pluripotent Stem Cells and Their Contribution to Interspecific Chimera

Naked mole rats (NMRs) are exceptionally long-lived, cancer-resistant rodents. Identifying the defining characteristics of these traits may shed light on aging and cancer mechanisms. Here, we report the generation of induced pluripotent stem cells (iPSCs) from NMR fibroblasts and their contribution to mouse-NMR chimeric embryos. Efficient reprogramming could be observed under N2B27+2i conditions. The iPSCs displayed a characteristic morphology, expressed pluripotent markers, formed embryoid bodies, and showed typical differentiation patterns. Interestingly, NMR embryonic fibroblasts and the derived iPSCs had propensity for a tetraploid karyotype and were resistant to forming teratomas, but within mouse blastocysts they contributed to both interspecific placenta and fetus. Gene expression patterns of NMR iPSCs were more similar to those of human than mouse iPSCs. Overall, we uncovered unique features of NMR iPSCs and report a mouse-NMR chimeric model. The iPSCs and associated cell culture systems can be used for a variety of biological and biomedical applications.

Characterization of the single-cell derived bovine induced pluripotent stem cells

Single-cell derived bovine induced pluripotent stem cells (iPSCs) were generated by the introduction of piggyBac transposons with CAG promoting transcription factors (Oct3/4, Sox2, Klf4 and cMyc). In the study, the bovine iPSCs colony from single cell could passage more than 50 passages after enzymatic dissociation into single cells. These bovine iPSCs cells kept the normal karyotype and displayed dome shaped clones similar to mouse embryonic stem cells. They showed pluripotency in many ways, including their expression of pluripotency markers, such as OCT3/4, NANOG, SOX2, SSEA1, SSEA4, and AP in immunofluorescence assay, Oct4, Nanog, Sox2, Klf4 and cMyc in RT-PCR. Additionally, single-cell derived bovine iPSCs formed embryoid bodies and teratomas that all subsequently gave rise to differentiated cells from all three embryonic germ layers. The results showed that our reprogramming method could obtain high efficiency single-cell cloning bovine iPSCs, and the efficiency of single cell cloning is 40%.

Big Animal Cloning Using Transgenic Induced Pluripotent Stem Cells: A Case Study of Goat Transgenic Induced Pluripotent Stem Cells

Using of embryonic stem cells (ESCs) could improve production traits and disease resistance by improving the efficiency of somatic cell nuclear transfer (SCNT) technology. However, robust ESCs have not been established from domestic ungulates. In the present study, we generated goat induced pluripotent stem cells (giPSCs) and transgenic cloned dairy goat induced pluripotent stem cells (tgiPSCs) from dairy goat fibroblasts (gFs) and transgenic cloned dairy goat fibroblasts (tgFs), respectively, using lentiviruses that contained hOCT4, hSOX2, hMYC, and hKLF4 without chemical compounds. The giPSCs and tgiPSCs expressed endogenous pluripotent markers, including OCT4, SOX2, MYC, KLF4, and NANOG. Moreover, they were able to maintain a normal karyotype and differentiate into derivatives from all three germ layers in vitro and in vivo. Using SCNT, tgFs and tgiPSCs were used as donor cells to produce embryos, which were named tgF-Embryos and tgiPSC-Embryos. The fusion rates and cleavage rates had no significant differences between tgF-Embryos and tgiPSC-Embryos. However, the expression of IGF-2, which is an important gene associated with embryonic development, was significantly lower in tgiPSC-Embryos than in tgF-Embryos and was not significantly different from vivo-Embryos.

Cellular reprogramming in farm animals: an overview of iPSC generation in the mammalian farm animal species

Establishment of embryonic stem cell (ESC) lines has been successful in mouse and human, but not in farm animals. Development of direct reprogramming technology offers an alternative approach for generation of pluripotent stem cells, applicable also in farm animals. Induced pluripotent stem cells (iPSCs) represent practically limitless, ethically acceptable, individuum-specific source of pluripotent cells that can be generated from different types of somatic cells. iPSCs can differentiate to all cell types of an organism’s body and have a tremendous potential for numerous applications in medicine, agriculture, and biotechnology. However, molecular mechanisms behind the reprogramming process remain largely unknown and hamper generation of bona fide iPSCs and their use in human clinical practice. Large animal models are essential to expand the knowledge obtained on rodents and facilitate development and validation of transplantation therapies in preclinical studies. Additionally, transgenic animals with special traits could be generated from genetically modified pluripotent cells, using advanced reproduction techniques. Despite their applicative potential, it seems that iPSCs in farm animals haven’t received the deserved attention. The aim of this review was to provide a systematic overview on iPSC generation in the most important mammalian farm animal species (cattle, pig, horse, sheep, goat, and rabbit), compare protein sequence similarity of pluripotency-related transcription factors in different species, and discuss potential uses of farm animal iPSCs. Literature mining revealed 32 studies, describing iPSC generation in pig (13 studies), cattle (5), horse (5), sheep (4), goat (3), and rabbit (2) that are summarized in a concise, tabular format.

Pluripotent stem cells and livestock genetic engineering

The unlimited proliferative ability and capacity to contribute to germline chimeras make pluripotent embryonic stem cells (ESCs) perfect candidates for complex genetic engineering. The utility of ESCs is best exemplified by the numerous genetic models that have been developed in mice, for which such cells are readily available. However, the traditional systems for mouse genetic engineering may not be practical for livestock species, as it requires several generations of mating and selection in order to establish homozygous founders. Nevertheless, the self-renewal and pluripotent characteristics of ESCs could provide advantages for livestock genetic engineering such as ease of genetic manipulation and improved efficiency of cloning by nuclear transplantation. These advantages have resulted in many attempts to isolate livestock ESCs, yet it has been generally concluded that the culture conditions tested so far are not supportive of livestock ESCs self-renewal and proliferation. In contrast, there are numerous reports of derivation of livestock induced pluripotent stem cells (iPSCs), with demonstrated capacity for long term proliferation and in vivo pluripotency, as indicated by teratoma formation assay. However, to what extent these iPSCs represent fully reprogrammed PSCs remains controversial, as most livestock iPSCs depend on continuous expression of reprogramming factors. Moreover, germline chimerism has not been robustly demonstrated, with only one successful report with very low efficiency. Therefore, even 34 years after derivation of mouse ESCs and their extensive use in the generation of genetic models, the livestock genetic engineering field can stand to gain enormously from continued investigations into the derivation and application of ESCs and iPSCs.

Inhibition of JAK-STAT ERK/MAPK and Glycogen Synthase Kinase-3 Induces a Change in Gene Expression Profile of Bovine Induced Pluripotent Stem Cells

Pluripotent stem cells (PSCs) fall in two states, one highly undifferentiated, the naïve state, and the primed state, characterized by the inability to contribute to germinal lineage. Several reports have demonstrated that these states can be modified by changes to the cell culture conditions. With the advent of nuclear reprogramming, bovine induced pluripotent stem cells (biPSCs) have been generated. These cells represent examples of a transient-intermediate state of pluripotency with remarkable characteristics and biotechnological potential. Herein, we generated and characterized biPSC. Next, we evaluated different culture conditions for the ability to affect the expression of the set of core pluripotent transcription factors in biPSC. It was found that the use of 6-bromoindirubin-3-oxime and Sc1 inhibitors alone or in combination with 5-AzaC induced significantly higher levels of expression of endogenous REX1, OCT4, NANOG, and SOX2. Furthermore, LIF increased the levels of expression of OCT4 and REX1, compared with those cultured with LIF + bFGF. By contrast, bFGF decreased the levels of expression for both REX1 and OCT4. These results demonstrate that the biPSC gene expression profile is malleable by modification of the cell culture conditions well after nuclear reprogramming, and the culture conditions may determine their differentiation potential.

Epigenetic modification with trichostatin A does not correct specific errors of somatic cell nuclear transfer at the transcriptomic level; highlighting the non-random nature of oocyte-mediated reprogramming errors

Background

The limited duration and compromised efficiency of oocyte-mediated reprogramming, which occurs during the early hours following somatic cell nuclear transfer (SCNT), may significantly interfere with epigenetic reprogramming, contributing to the high incidence of ill/fatal transcriptional phenotypes and physiological anomalies occurring later during pre- and post-implantation events. A potent histone deacetylase inhibitor, trichostatin A (TSA), was used to understand the effects of assisted epigenetic modifications on transcriptional profiles of SCNT blastocysts and to identify specific or categories of genes affected.

Results

TSA improved the yield and quality of in vitro embryo development compared to control (CTR-NT). Significance analysis of microarray results revealed that of 37,238 targeted gene transcripts represented on the microarray slide, a relatively small number of genes were differentially expressed in CTR-NT (1592 = 4.3 %) and TSA-NT (1907 = 5.1 %) compared to IVF embryos. For both SCNT groups, the majority of downregulated and more than half of upregulated genes were common and as much as 15 % of all deregulated transcripts were located on chromosome X. Correspondence analysis clustered CTR-NT and IVF transcriptomes close together regardless of the embryo production method, whereas TSA changed SCNT transcriptome to a very clearly separated cluster. Ontological classification of deregulated genes using IPA uncovered a variety of functional categories similarly affected in both SCNT groups with a preponderance of genes required for biological processes. Examination of genes involved in different canonical pathways revealed that the WNT and FGF pathways were similarly affected in both SCNT groups. Although TSA markedly changed epigenetic reprogramming of donor cells (DNA-methylation, H3K9 acetylation), reconstituted oocytes (5mC, 5hmC), and blastocysts (DNA-methylation, H3K9 acetylation), these changes did not recapitulate parallel marked changes in chromatin remodeling, and nascent mRNA and OCT4-EGFP expression of TSA-NT vs. CRT-NT embryos.

Conclusions

The results obtained suggest that despite the extensive reprogramming of donor cells that occurred by the blastocyst stage, SCNT-specific errors are of a non-random nature in bovine and are not responsive to epigenetic modifications by TSA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2264-z) contains supplementary material, which is available to authorized users.

Characterization of Bovine NANOG5'-flanking Region during Differentiation of Mouse Embryonic Stem Cells

Embryonic stem cells (ESCs) have been used as a powerful tool for research including gene manipulated animal models and the study of developmental gene regulation. Among the critical regulatory factors that maintain the pluripotency and self-renewal of undifferentiated ESCs, NANOG plays a very important role. Nevertheless, because pluripotency maintaining factors and specific markers for livestock ESCs have not yet been probed, few studies of the NANOG gene from domestic animals including bovine have been reported. Therefore, we chose mouse ESCs in order to understand and compare NANOG expression between bovine, human, and mouse during ESCs differentiation. We cloned a 600 bp (−420/+181) bovine NANOG 5′-flanking region, and tagged it with humanized recombinant green fluorescent protein (hrGFP) as a tracing reporter. Very high GFP expression for bovine NANOG promoter was observed in the mouse ESC line. GFP expression was monitored upon ESC differentiation and was gradually reduced along with differentiation toward neurons and adipocyte cells. Activity of bovine NANOG (−420/+181) promoter was compared with already known mouse and human NANOG promoters in mouse ESC and they were likely to show a similar pattern of regulation. In conclusion, bovine NANOG 5-flanking region functions in mouse ES cells and has characteristics similar to those of mouse and human. These results suggest that bovine gene function studied in mouse ES cells should be evaluated and extrapolated for application to characterization of bovine ES cells.

Pluripotent Stem Cells from Domesticated Mammals

This review deals with the latest advances in the study of embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) from domesticated species, with a focus on pigs, cattle, sheep, goats, horses, cats, and dogs. Whereas the derivation of fully pluripotent ESC from these species has proved slow, reprogramming of somatic cells to iPSC has been more straightforward. However, most of these iPSC depend on the continued expression of the introduced transgenes, a major drawback to their utility. The persistent failure in generating ESC and the dependency of iPSC on ectopic genes probably stem from an inability to maintain the stability of the endogenous gene networks necessary to maintain pluripotency. Based on work in humans and rodents, achievement of full pluripotency will likely require fine adjustments in the growth factors and signaling inhibitors provided to the cells. Finally, we discuss the future utility of these cells for biomedical and agricultural purposes.

Signal Inhibition Reveals JAK/STAT3 Pathway as Critical for Bovine Inner Cell Mass Development

The inner cell mass (ICM) of mammalian blastocysts consists of pluripotent epiblast and hypoblast lineages, which develop into embryonic and extraembryonic tissues, respectively. We conducted a chemical screen for regulators of epiblast identity in bovine Day 8 blastocysts. From the morula stage onward, in vitro fertilized embryos were cultured in the presence of cell-permeable small molecules targeting nine principal signaling pathway components, including TGFbeta1, BMP, EGF, VEGF, PDGF, FGF, cAMP, PI3K, and JAK signals. Using 1) blastocyst quality (by morphological grading), 2) cell numbers (by differential stain), and 3) epiblast (FGF4, NANOG) and hypoblast (PDGFRa, SOX17) marker gene expression (by quantitative PCR), we identified positive and negative regulators of ICM development and pluripotency. TGFbeta1, BMP, and cAMP and combined VEGF/PDGF/FGF signals did not affect blastocyst development while PI3K was important for ICM growth but did not alter lineage-specific gene expression. Stimulating cAMP specifically increased NANOG expression, while combined VEGF/PDGF/FGF inhibition up-regulated epiblast and hypoblast markers. The strongest effects were observed by suppressing JAK1/2 signaling with AZD1480. This treatment interfered with ICM formation, but trophectoderm cell numbers and markers (CDX2, KTR8) were not altered. JAK inhibition repressed both epiblast and hypoblast transcripts as well as naive pluripotency-related genes (KLF4, TFCP2L1) and the JAK substrate STAT3. We found that tyrosine (Y) 705-phosphorylated STAT3 (pSTAT3(Y705)) was restricted to ICM nuclei, where it colocalized with SOX2 and NANOG. JAK inhibition abolished this ICM-exclusive pSTAT3(Y705) signal and strongly reduced the number of SOX2-positive nuclei. In conclusion, JAK/STAT3 activation is required for bovine ICM formation and acquisition of naive pluripotency markers.

Derivation and characterization of bovine induced pluripotent stem cells by transposon-mediated reprogramming

Induced pluripotent stem cells (iPSCs) are a seminal breakthrough in stem cell research and are promising tools for advanced regenerative therapies in humans and reproductive biotechnology in farm animals. iPSCs are particularly valuable in species in which authentic embryonic stem cell (ESC) lines are yet not available. Here, we describe a nonviral method for the derivation of bovine iPSCs employing Sleeping Beauty (SB) and piggyBac (PB) transposon systems encoding different combinations of reprogramming factors, each separated by self-cleaving peptide sequences and driven by the chimeric CAGGS promoter. One bovine iPSC line (biPS-1) generated by a PB vector containing six reprogramming genes was analyzed in detail, including morphology, alkaline phosphatase expression, and typical hallmarks of pluripotency, such as expression of pluripotency markers and formation of mature teratomas in immunodeficient mice. Moreover, the biPS-1 line allowed a second round of SB transposon-mediated gene transfer. These results are promising for derivation of germ line-competent bovine iPSCs and will facilitate genetic modification of the bovine genome.

In vitro culture of stem-like cells derived from somatic cell nuclear transfer bovine embryos of the Korean beef cattle species, HanWoo

We established and maintained somatic cell nuclear transfer embryo-derived stem-like cells (SCNT-eSLCs) from the traditional Korean beef cattle species, HanWoo (Bos taurus coreanae). Each SCNT blastocyst was placed individually on a feeder layer with culture medium containing three inhibitors of differentiation (3i). Primary colonies formed after 2-3 days of culture and the intact colonies were passaged every 5-6 days. The cells in each colony showed embryonic stem cell-like morphologies with a distinct boundary and were positive to alkaline phosphatase staining. Immunofluorescence and reverse transcription-polymerase chain reaction analyses also confirmed that these colonies expressed pluripotent markers. The colonies were maintained over 50 passages for more than 270 days. The cells showed normal karyotypes consisting of 60 chromosomes at Passage 50. Embryoid bodies were formed by suspension culture to analyse in vitro differentiation capability. Marker genes representing the differentiation into three germ layers were expressed. Typical embryonal carcinoma was generated after injecting cells under the testis capsule of nude mice, suggesting that the cultured cells may also have the potential of in vivo differentiation. In conclusion, we generated eSLCs from SCNT bovine embryos, using a 3i system that sustained stemness, normal karyotype and pluripotency, which was confirmed by in vitro and in vivo differentiation.

Induced pluripotent stem cells: Mechanisms, achievements and perspectives in farm animals

Pluripotent stem cells are unspecialized cells with unlimited self-renewal, and they can be triggered to differentiate into desired specialized cell types. These features provide the basis for an unlimited cell source for innovative cell therapies. Pluripotent cells also allow to study developmental pathways, and to employ them or their differentiated cell derivatives in pharmaceutical testing and biotechnological applications. Via blastocyst complementation, pluripotent cells are a favoured tool for the generation of genetically modified mice. The recently established technology to generate an induced pluripotency status by ectopic co-expression of the transcription factors Oct4, Sox2, Klf4 and c-Myc allows to extending these applications to farm animal species, for which the derivation of genuine embryonic stem cells was not successful so far. Most induced pluripotent stem (iPS) cells are generated by retroviral or lentiviral transduction of reprogramming factors. Multiple viral integrations into the genome may cause insertional mutagenesis and may increase the risk of tumour formation. Non-integration methods have been reported to overcome the safety concerns associated with retro and lentiviral-derived iPS cells, such as transient expression of the reprogramming factors using episomal plasmids, and direct delivery of reprogramming mRNAs or proteins. In this review, we focus on the mechanisms of cellular reprogramming and current methods used to induce pluripotency. We also highlight problems associated with the generation of iPS cells. An increased understanding of the fundamental mechanisms underlying pluripotency and refining the methodology of iPS cell generation will have a profound impact on future development and application in regenerative medicine and reproductive biotechnology of farm animals.

PRMT5 enhances generation of induced pluripotent stem cells from dairy goat embryonic fibroblasts via down-regulation of p53

OBJECTIVES

Protein arginine methyltransferase 5 (PRMT5), is thought to play a role in epigenetic reprogramming of mouse germ cells. However, up to now there has been little information concerning its expression profile and effects on generation of induced pluripotent stem cells (iPSCs) from somatic cells, in livestock. Here, we have explored PRMT5 expression profiles in dairy goats and its consequences to derivation of iPSCs from dairy goat embryonic fibroblasts (GEFs).

MATERIALS AND METHODS

We investigated effects of PRMT5 on iPS-like cells production in vitro. alkaline phosphatase (AP) staining, QRT-PCR and western blotting analysis of expression of related markers were used to evaluate efficiency of generation of iPSCs derived from GEFs.

RESULTS

These showed PRMT5 to be a conservative gene widely expressed in various tissues and different-aged testes. PRMT5 overexpression in combination with OCT3/4, SOX2, KLF4 and C-MYC (POSKM) significantly increased number of AP positive iPS-like colony-derived GEFs compared to OSKM alone, in our dairy goats. Moreover, our results demonstrated that PRMT5 overexpression stimulated GEF proliferation and down-regulated p53, p21 (a target gene of p53) and the apoptotic marker caspase 3, to enhance somatic cell reprogramming.

CONCLUSION

This study provides an efficient model for future studies on mechanisms underlying goat somatic cell reprogramming and differentiation.

From "ES-like" cells to induced pluripotent stem cells: a historical perspective in domestic animals

Pluripotent stem cells such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) provide great potential as cell sources for gene editing to generate genetically modified animals, as well as in the field of regenerative medicine. Stable, long-term ESCs have been established in laboratory mouse and rat; however, isolation of true pluripotent ESCs in domesticated animals such as pigs and dogs have been less successful. Initially, domesticated animal pluripotent cell lines were referred to as "embryonic stem-like" cells owing to their similar morphologic characteristics to mouse ESCs, but accompanied by a limited ability to proliferate in vitro in an undifferentiated state. That is, they shared some but not all the characteristics of true ESCs. More recently, advances in reprogramming using exogenous transcription factors, combined with the utilization of small chemical inhibitors of key biochemical pathways, have led to the isolation of iPSCs. In this review, we provide a historical perspective of the isolation of various types of pluripotent stem cells in domesticated animals. In addition, we summarize the latest progress and limitations in the derivation and application of iPSCs.

Nonviral minicircle generation of induced pluripotent stem cells compatible with production of chimeric chickens

Chickens are vitally important in numerous countries as a primary food source and a major component of economic development. Efforts have been made to produce transgenic birds through pluripotent stem cell [primordial germ cells and embryonic stem cells (ESCs)] approaches to create animals with improved traits, such as meat and egg production or even disease resistance. However, these cell types have significant limitations because they are hard to culture long term while maintaining developmental plasticity. Induced pluripotent stem cells (iPSCs) are a novel class of stem cells that have proven to be robust, leading to the successful development of transgenic mice, rats, quail, and pigs and may potentially overcome the limitations of previous pluripotent stem cell systems in chickens. In this study we generated chicken (c) iPSCs from fibroblast cells for the first time using a nonviral minicircle reprogramming approach. ciPSCs demonstrated stem cell morphology and expressed key stem cell markers, including alkaline phosphatase, POU5F1, SOX2, NANOG, and SSEA-1. These cells were capable of rapid growth and expressed high levels of telomerase. Late-passage ciPSCs transplanted into stage X embryos were successfully incorporated into tissues of all three germ layers, and the gonads demonstrated significant cellular plasticity. These cells provide an exciting new tool to create transgenic chickens with broad implications for agricultural and transgenic animal fields at large.

Role of stem cells in large animal genetic engineering in the TALENs-CRISPR era

The establishment of embryonic stem cells (ESCs) and gene targeting technologies in mice has revolutionised the field of genetics. The relative ease with which genes can be knocked out, and exogenous sequences introduced, has allowed the mouse to become the prime model for deciphering the genetic code. Not surprisingly, the lack of authentic ESCs has hampered the livestock genetics field and has forced animal scientists into adapting alternative technologies for genetic engineering. The recent discovery of the creation of induced pluripotent stem cells (iPSCs) by upregulation of a handful of reprogramming genes has offered renewed enthusiasm to animal geneticists. However, much like ESCs, establishing authentic iPSCs from the domestic animals is still beset with problems, including (but not limited to) the persistent expression of reprogramming genes and the lack of proven potential for differentiation into target cell types both in vitro and in vivo. Site-specific nucleases comprised of zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and clustered regulated interspaced short palindromic repeats (CRISPRs) emerged as powerful genetic tools for precisely editing the genome, usurping the need for ESC-based genetic modifications even in the mouse. In this article, in the aftermath of these powerful genome editing technologies, the role of pluripotent stem cells in livestock genetics is discussed.

Generation and characterization of bat-induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) were first generated from mouse embryonic fibroblasts in the year 2006. These cells resemble the typical morphology of embryonic stem cells, express pluripotency markers, and are able to transmit through germlines. To date, iPSCs of many species have been generated, whereas generation of bat iPSCs (biPSCs) has not been reported. To facilitate in-depth study of bats at the molecular and cellular levels, we describe the successful derivation of biPSCs with a piggyBac (PB) vector that contains eight reprogramming factors Oct4, Sox2, Klf4, Nanog, cMyc, Lin28, Nr5a2, and miR302/367. These biPSCs were cultured in media containing leukemia inhibitory factor and three small molecule inhibitors (CHIR99021, PD0325901, and A8301). They retained normal karyotype, displayed alkaline phosphatase activity, and expressed pluripotency markers Oct4, Sox2, Nanog, TBX3, and TRA-1-60. They could differentiate in vitro to form embryoid bodies and in vivo to form teratomas that contained tissue cells of all three germ layers. Generation of biPSCs will facilitate future studies on the mechanisms of antiviral immunity and longevity of bats at the cellular level.

Induced pluripotent stem cells from goat fibroblasts

Embryonic stem cells (ESCs) are a powerful model for genetic engineering, studying developmental biology, and modeling disease. To date, ESCs have been established from the mouse (Evans and Kaufman, 1981, Nature 292:154-156), non-human primates (Thomson et al., , Proc Nat Acad Sci USA 92:7844-7848), humans (Thomson et al., 1998, Science 282:1145-1147), and rats (Buehr et al., , Cell 135:1287-1298); however, the derivation of ESCs from domesticated ungulates such as goats, sheep, cattle, and pigs have not been successful. Alternatively, induced pluripotent stem cells (iPSCs) can be generated by reprogramming somatic cells with several combinations of genes encoding transcription factors (OCT3/4, SOX2, KLF4, cMYC, LIN28, and NANOG). To date, iPSCs have been isolated from various species, but only limited information is available regarding goat iPSCs (Ren et al., 2011, Cell Res 21:849-853). The objectives of this study were to generate goat iPSCs from fetal goat primary ear fibroblasts using lentiviral transduction of four human transcription factors: OCT4, SOX2, KLF4, and cMYC. The goat iPSCs were successfully generated by co-culture with mitomycin C-treated mouse embryonic fibroblasts using medium supplemented with knockout serum replacement and human basic fibroblast growth factor. The goat iPSCs colonies are flat, compact, and closely resemble human iPSCs. They have a normal karyotype; stain positive for alkaline phosphatase, OCT4, and NANOG; express endogenous pluripotency genes (OCT4, SOX2, cMYC, and NANOG); and can spontaneously differentiate into three germ layers in vitro and in vivo.

Current status of induced pluripotent stem cells in cardiac tissue regeneration and engineering

Myocardial infarction (MI) is associated with damage to the myocardium which results in a great loss of functional cardiomyocytes. As one of the most terminally differentiated organs, the endogenous regenerative potentials of adult hearts are extremely limited and insufficient to compensate for the myocardial loss occurring after MI. Consequentially, exogenous regenerative strategies, especially cell replacement therapy, have emerged and attracted increasing more attention in the field of cardiac tissue regeneration. A renewable source of seeding cells is therefore one of the most important subject in the field. Induced pluripotent stem cells (iPSCs), embryonic stem cell (ESC)-like cells that are derived from somatic cells by reprogramming, represent a promising candidate due to their high potentials for self-renewal, proliferation, differentiation and more importantly, they provide an invaluable method of deriving patient-specific pluripotent stem cells. Therefore, iPSC-based cardiac tissue regeneration and engineering has been extensively investigated in recent years. This review will discuss the achievements and current status in this field, including development of iPSC derivation, in vitro strategies for cardiac generation from iPSCs, cardiac application of iPSCs, challenges confronted at present as well as perspective in the future.

Veterinary applications of induced pluripotent stem cells: regenerative medicine and models for disease?

Induced pluripotent stem cells (iPSCs) can now be derived from a tissue biopsy and represent a promising new platform for disease modelling, drug and toxicity testing, biomarker development and cell-based therapies for regenerative medicine. In regenerative medicine, large animals may represent the best models for man, and thereby provide invaluable systems in which to test the safety and the potential of iPSCs. Hence, testing iPSCs in veterinary species may serve a double function, namely, developing therapeutic products for regenerative medicine in veterinary patients while providing valuable background information for human clinical trials. The production of iPSCs from livestock or wild species is attractive because it could improve efficiency and reduce costs in various fields, such as transgenic animal generation and drug development, preservation of biological diversity, and because it also offers an alternative to xenotransplantation for in vivo generation of organs. Although the technology of cellular reprogramming using the so-called 'Yamanaka factors' is in its peak expectation phase and many concerns still need to be addressed, the rapid technical progress suggests that iPSCs could contribute significantly to novel therapies in veterinary and biomedical practice in the near future. This review provides an overview of the potential applications of iPSCs in veterinary medicine.

Stem cell research: a novel boulevard towards improved bovine mastitis management

The dairy industry is a multi-billion dollar industry catering the nutritional needs of all age groups globally through the supply of milk. Clinical mastitis has a severe impact on udder tissue and is also an animal welfare issue. Moreover, it significantly reduces animal value and milk production. Mammary tissue damage reduces the number and activity of epithelial cells and consequently contributes to decreased milk production. The high incidence, low cure rate of this highly economic and sometimes deadly disease is an alarming for dairy sector as well as policy makers. Bovine mammary epithelial cells (MECs) and their stem cells are very important in milk production and bioengineering. The adult mammary epithelium consists of two main cell types; an inner layer of luminal epithelial cells, which produce the milk during lactation, and an outer layer of myoepithelial cells resting on a basement membrane, which are responsible for pushing the milk through the ductal network to the teat cistern. Inner layer of columner/luminal cells of bovine MECs, is characterized by cytokeratin18, 19 (CK18, CK19) and outer layer such as myoepithelial cells which are characterized by CK14, α-smooth muscle actin (α-SMA) and p63. Much work has been done in mouse and human, on mammary gland stem cell research, particularly in cancer therapy, but stem cell research in bovine is still in its infancy. Such stem/progenitor cell discoveries in human and mouse mammary gland bring some hope for application in bovines. These progenitors may be therapeutically adopted to correct the structural/cytological defects in the bovine udder due to mastitis. In the present review we focused on various kinds of stem/progenitor cells which can have therapeutic utility and their possibilities to use as a potential stem cell therapy in the management of bovine post-mastitis damage in orders to restore milk production. The possibilities of bovine mammary stem cell therapy offers significant potential for regeneration of tissues that can potentially replace/repair diseased and damaged tissue through differentiation into epithelial, myoepithelial and/or cuboidal/columnar cells in the udder with minimal risk of rejection and side effects.

Early embryonic development, assisted reproductive technologies, and pluripotent stem cell biology in domestic mammals

Over many decades assisted reproductive technologies, including artificial insemination, embryo transfer, in vitro production (IVP) of embryos, cloning by somatic cell nuclear transfer (SCNT), and stem cell culture, have been developed with the aim of refining breeding strategies for improved production and health in animal husbandry. More recently, biomedical applications of these technologies, in particular, SCNT and stem cell culture, have been pursued in domestic mammals in order to create models for human disease and therapy. The following review focuses on presenting important aspects of pre-implantation development in cattle, pigs, horses, and dogs. Biological aspects and impact of assisted reproductive technologies including IVP, SCNT, and culture of pluripotent stem cells are also addressed.

Pluripotent cells in farm animals: state of the art and future perspectives

Pluripotent cells, such as embryonic stem (ES) cells, embryonic germ cells and embryonic carcinoma cells are a unique type of cell because they remain undifferentiated indefinitely in in vitro culture, show self-renewal and possess the ability to differentiate into derivatives of the three germ layers. These capabilities make them a unique in vitro model for studying development, differentiation and for targeted modification of the genome. True pluripotent ESCs have only been described in the laboratory mouse and rat. However, rodent physiology and anatomy differ substantially from that of humans, detracting from the value of the rodent model for studies of human diseases and the development of cellular therapies in regenerative medicine. Recently, progress in the isolation of pluripotent cells in farm animals has been made and new technologies for reprogramming of somatic cells into a pluripotent state have been developed. Prior to clinical application of therapeutic cells differentiated from pluripotent stem cells in human patients, their survival and the absence of tumourigenic potential must be assessed in suitable preclinical large animal models. The establishment of pluripotent cell lines in farm animals may provide new opportunities for the production of transgenic animals, would facilitate development and validation of large animal models for evaluating ESC-based therapies and would thus contribute to the improvement of human and animal health. This review summarises the recent progress in the derivation of pluripotent and reprogrammed cells from farm animals. We refer to our recent review on this area, to which this article is complementary.