Isolation and characterization of embryonic stem-like cells from canine blastocysts

Generation of canine induced pluripotent stem cells under feeder-free conditions using Sendai virus vector encoding six canine reprogramming factors

Although it is in its early stages, canine induced pluripotent stem cells (ciPSCs) hold great potential for innovative translational research in regenerative medicine, developmental biology, drug screening, and disease modeling. However, almost all ciPSCs were generated from fibroblasts, and available canine cell sources for reprogramming are still limited. Furthermore, no report is available to generate ciPSCs under feeder-free conditions because of their low reprogramming efficiency. Here, we reanalyzed canine pluripotency-associated genes and designed canine LIN28A, NANOG, OCT3/4, SOX2, KLF4, and C-MYC encoding Sendai virus vector, called 159cf. and 162cf. We demonstrated that not only canine fibroblasts but also canine urine-derived cells, which can be isolated using a noninvasive and straightforward method, were successfully reprogrammed with or without feeder cells. ciPSCs existed in undifferentiated states, differentiating into the three germ layers in vitro and in vivo. We successfully generated ciPSCs under feeder-free conditions, which can promote studies in veterinary and consequently human regenerative medicines.

Generation, characterization, and differentiation of induced pluripotent stem-like cells in the domestic cat

Induced pluripotent stem (iPS) cells are generated from somatic cells and can differentiate into various cell types. Therefore, these cells are expected to be a powerful tool for modeling diseases and transplantation therapy. Generation of domestic cat iPS cells depending on leukemia inhibitory factor has been reported; however, this strategy may not be optimized. Considering that domestic cats are excellent models for studying spontaneous diseases, iPS cell generation is crucial. In this study, we aimed to derive iPS cells from cat embryonic fibroblasts retrovirally transfected with mouse Oct3/4, Klf4, Sox2, and c-Myc. After transfection, embryonic fibroblasts were reseeded onto inactivated SNL 76/7 and cultured in a medium supplemented with basic fibroblast growth factor. Flat, compact, primary colonies resembling human iPS colonies were observed. Additionally, primary colonies were more frequently observed in the KnockOut Serum Replacement medium than in the fetal bovine serum (FBS) medium. However, enhanced maintenance and proliferation of iPS-like cells occurred in the FBS medium. These iPS-like cells expressed embryonic stem cell markers, had normal karyotypes, proliferated beyond 45 passages, and differentiated into all three germ layers in vitro. Notably, expression of exogenous Oct3/4, Klf4, and Sox2 was silenced in these cells. However, the iPS-like cells failed to form teratomas. In conclusion, this is the first study to establish and characterize cat iPS-like cells, which can differentiate into different cell types depending on the basic fibroblast growth factor.

Pluripotent Stem Cells of Order Carnivora: Technical Perspective

Human and mouse induced pluripotent stem cells (PSCs) are widely used for studying early embryonic development and for modeling of human diseases. Derivation and studying of PSCs from model organisms beyond commonly used mice and rats may provide new insights into the modeling and treating human diseases. The order Carnivora representatives possess unique features and are already used for modeling human-related traits. This review focuses on the technical aspects of derivation of the Carnivora species PSCs as well as their characterization. Current data on dog, feline, ferret, and American mink PSCs are summarized.

The role of embryonic stem cells, transcription and growth factors in mammals: A review

Mammals represent a relevant species in worldwide cultures with significant commercial value. These animals are considered an attractive large animal model for biomedical and biotechnology research. The development of large animal experimental models may open alternative strategies for investigating stem cells (SCs) physiology and potential application in the veterinary field. The embryonic stem cells (ESCs) are known to possess natural pluripotency that confers the ability to differentiate into various tissues in vivo and in vitro. These notable characteristics can be useful for research and innovative applications, including biomedicine, agriculture and industry. Transcription factors play a crucial role in preserving stem cell self-renewal, whereas growth factors are involved in both growth and differentiation. However, to date, many questions concerning pluripotency, cellular differentiation regulator genes, and other molecules such as growth factors and their interactions in many mammalian species remain unresolved. The purpose of this review is to provide an overall review regarding the study of ESCs in mammals and briefly discuss the role of transcription and growth factors.

Efficient Reprogramming of Canine Peripheral Blood Mononuclear Cells into Induced Pluripotent Stem Cells

Forced coexpression of the transcription factors Oct3/4, Klf4, Sox2, and c-Myc reprograms somatic cells into pluripotent stem cells (PSCs). Such induced PSCs (iPSCs) can generate any cell type of the adult body or indefinitely proliferate without losing their potential. Accordingly, iPSCs can serve as an unlimited cell source for the development of various disease models and regenerative therapies for animals and humans. Although canine peripheral blood mononuclear cells (PBMCs) can be easily obtained, they have a very low iPSC reprogramming efficiency. In this study, we determined the reprogramming efficiency of canine PBMCs under several conditions involving three types of media supplemented with small-molecule compounds. We found that canine iPSCs (ciPSCs) could be efficiently generated from PBMCs using N2B27 medium supplemented with leukemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF), and a small-molecule cocktail (Y-27632, PD0325901, CHIR99021, A-83-01, Forskolin, and l-ascorbic acid). We generated five ciPSC lines that could be maintained in StemFit® medium supplemented with LIF. The SeVdp(KOSM)302L vectors were appropriately silenced in four ciPSC lines. Of the two lines characterized, both were positive for alkaline phosphatase activity and expressed pluripotency markers, including the Oct3/4, Sox2, and Nanog transcripts, as well as the octamer-binding transcription factor (OCT) 3/4 and NANOG proteins, and the SSEA-1 carbohydrate antigen. The ciPSCs could form embryoid bodies and differentiate into the three germ layers, as indicated by marker gene and protein expression. Furthermore, one ciPSC line formed teratomas comprising several tissues from every germ layer. Our ciPSC lines maintained a normal karyotype even after multiple passages. Moreover, our new reprogramming method was able to generate ciPSCs from multiple donor PBMCs. In conclusion, we developed an easy and efficient strategy for the generation of footprint-free ciPSCs from PBMCs. We believe that this strategy can be useful for disease modeling and regenerative medicine in the veterinary field.

Chromatin accessibility in canine stromal cells and its implications for canine somatic cell reprogramming

Naturally occurring disease in pet dogs is an untapped and unique resource for stem cell-based regenerative medicine translational research, given the many similarities and complexity such disease shares with their human counterparts. Canine-specific regulators of somatic cell reprogramming and pluripotency maintenance are poorly understood. While retroviral delivery of the four Yamanaka factors successfully reprogrammed canine embryonic fibroblasts, adult stromal cells remained resistant to reprogramming in spite of effective viral transduction and transgene expression. We hypothesized that adult stromal cells fail to reprogram due to an epigenetic barrier. Here, we performed assay for transposase-accessible chromatin using sequencing (ATAC-seq) on canine stromal and pluripotent stem cells, analyzing 51 samples in total, and establishing the global landscape of chromatin accessibility before and after reprogramming to induced pluripotent stem cells (iPSC). We also studied adult stromal cells that do not yield iPSC colonies to identify potential reprogramming barriers. ATAC-seq analysis identified distinct cell type clustering patterns and chromatin remodeling during embryonic fibroblast reprogramming. Compared with embryonic fibroblasts, adult stromal cells had a chromatin accessibility landscape that reflects phenotypic differentiation and somatic cell-fate stability. We ultimately identified 76 candidate genes and several transcription factor binding motifs that may be impeding somatic cell reprogramming to iPSC, and could be targeted for inhibition or activation, in order to improve the process in canines. These results provide a vast resource for better understanding of pluripotency regulators in dogs and provide an unbiased rationale for novel canine-specific reprogramming approaches.

A mechanical non-enzymatic method for isolation of mouse embryonic fibroblasts

Mouse embryonic fibroblasts (MEFs) accessibility coupled with their simple generation make them as a typical embryonic cell model and feeder layer for in vitro expansion of pluripotent stem cells (PSCs). In this study, a mechanical isolation technique was adopted to isolate MEFs and the efficiency of this technique was compared with enzymatic digestion method. The suspended MEFs were prepared either by mechanical method or 0.25% trypsin enzymatic digestion. The effect of tissue processing on cell apoptosis/necrosis, morphology, viable cell yield, population doubling time, surface marker expression, and the capacity to support PSCs were determined. The mechanical method yielded a significantly higher number of viable cells. However, it showed similar morphology and proliferation characteristics as compared to enzymatic digestion. The mechanical method induced slight apoptosis in MEFs; however, it did not exert the necrotic effect of trypsinization. Treatment of tissue slurry with trypsin solution caused cell lysis and subsequently cell clump formation. Mechanically isolated cells exhibited a higher expression of the MEF surface antigens Sca1, CD106, and CD105. The PSCs on mechanically isolated MEFs displayed a higher expression of pluripotency genes, and formed more compact colonies with a stronger tendency to crowding compared with those cultured on cells isolated by enzymatic digestion. The mechanical method based on tissue inter-syringe processing is relatively a rapid and simple method for MEF isolation. Compared to the enzymatic digestion, the cells obtained from this method show higher expression of embryonic fibroblasts markers and a more functional capacity in supporting PSCs culture.

Positioning canine induced pluripotent stem cells (iPSCs) in the reprogramming landscape of naïve or primed state in comparison to mouse and human iPSCs

AIMS

Deriving canine-induced pluripotent stem cells (ciPSCs) have paved the way for developing novel cell-based disease models and transplantation therapies in the dog. Though ciPSCs have been derived in the presence of Leukemia inhibitory factor (LIF) as well in the presence of basic fibroblast growth factor (bFGF), the positioning of ciPSCs in the naïve or the primed state of pluripotency remains elusive. This study aims to understand whether canine iPSCs belong to naïve or prime state in comparison to mouse (m) iPSCs and human (h) iPSCs.

MAIN METHODS

In the present study, we derived ciPSCs in presence of LIF and compared their state of pluripotency with that of miPSCs and hiPSCs by culturing them in the presence of LIF, bFGF, and LIF + bFGF. Gene expression level at transcript level was performed by RT-PCR and qRT-PCR and at the protein level was analysed by immunofluorescence. We also attempted to understand the pluripotency state using lipid body analysis by bodipy staining and blue fluorescence emission.

KEY FINDINGS

In contrast to miPSCs, the naïve pluripotent stem cells, ciPSCs showed the expression of FGF5 similar to that of primed pluripotent stem cell, hiPSCs. Compared to miPSCs, ciPSCs cultured in presence of LIF showed enhanced expression of primed pluripotent marker FGF5, similar to hiPSCs cultured in presence of bFGF. Upon culturing in hiPSC culture condition, ciPSCs showed enhanced expression of core pluripotency genes compared to miPSCs cultured in similar condition. However, ciPSCs expressed naïve pluripotent marker SSEA1 similar to miPSCs and lacked the expression of primed state marker SSEA4 unlike hiPSCs. Interestingly, for the first time, we demonstrate the ciPSC pluripotency using lipid body analysis wherein ciPSCs showed enhanced bodipy staining and blue fluorescence emission, reflecting the primed state of pluripotency. ciPSCs expressed higher levels of fatty acid synthase (FASN), the enzyme involved in the synthesis of palmitate, similar to that of hiPSCs and higher than that of miPSCs. As ciPSCs exhibit characteristic properties of both naïve and primed pluripotent state, it probably represents a unique intermediary state of pluripotency that is distinct from that of mice and human pluripotent stem cells.

SIGNIFICANCE

Elucidating the pluripotent state of ciPSCs assists in better understanding of the reprogramming events and development in different species. The study would provide a footprint of species-specific differences involved in reprogramming and the potential implication of iPSCs as a tool to analyse evolution.

Generation of Footprint-Free Canine Induced Pluripotent Stem Cells Using Auto-Erasable Sendai Virus Vector

Canine induced pluripotent stem cells (ciPSCs) can be used in regenerative medicine. However, there are no reports on the generation of genome integration-free and completely exogenous gene-silenced (footprint free) ciPSCs that are tolerant to enzymatic single-cell passage. In this study, we reprogrammed canine embryonic fibroblasts using the auto-erasable replication-defective and persistent Sendai virus vector, SeVdp(KOSM)302L, and generated two ciPSC lines. The ciPSCs were positive for pluripotent markers, including alkaline phosphatase activity as well as OCT3/4, SOX2, and NANOG transcripts, and NANOG, stage-specific embryonic antigen-1, and partial TRA-1-60 protein expression, even after SeVdp(KOSM)302L removal. The ciPSCs were induced to differentiate into all the three germ layers as embryoid bodies in vitro and as teratomas in vivo. Furthermore, SeVdp(KOSM)302L-free ciPSCs maintained a normal karyotype even after repeated enzymatic single-cell passaging. Therefore, to our knowledge, for the first time, we demonstrated the generation of footprint-free and high-quality ciPSCs that can be passaged at the single-cell stage using enzymatic methods. Our method for generation of ciPSCs is a good step toward the development of clinical application of ciPSCs.

Dynamics of male canine germ cell development

Primordial germ cells (PGCs) are precursors of gametes that can generate new individuals throughout life in both males and females. Additionally, PGCs have been shown to differentiate into embryonic germ cells (EGCs) after in vitro culture. Most studies investigating germinative cells have been performed in rodents and humans but not dogs (Canis lupus familiaris). Here, we elucidated the dynamics of the expression of pluripotent (POU5F1 and NANOG), germline (DDX4, DAZL and DPPA3), and epigenetic (5mC, 5hmC, H3K27me3 and H3K9me2) markers that are important for the development of male canine germ cells during the early (22-30 days post-fertilization (dpf)), middle (35-40 dpf) and late (45-50 dpf) gestational periods. We performed sex genotype characterization, immunofluorescence, immunohistochemistry, and quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) analyses. Furthermore, in a preliminary study, we evaluated the capacity of canine embryo PGCs (30 dpf) to differentiate into EGCs. To confirm the canine EGCs phenotype, we performed alkaline phosphatase detection, immunohistochemistry, electron and transmission scanning microscopy and RT-qPCR analyses. The PGCs were positive for POU5F1 and H3K27me3 during all assessed developmental periods, including all periods between the gonadal tissue stage and foetal testes development. The number of NANOG, DDX4, DAZL, DPPA3 and 5mC-positive cells increased along with the developing cords from 35-50 dpf. Moreover, our results demonstrate the feasibility of inducing canine PGCs into putative EGCs that present pluripotent markers, such as POU5F1 and the NANOG gene, and exhibit reduced expression of germinative genes and increased expression of H3K27me3. This study provides new insight into male germ cell development mechanisms in dogs.

Characterization of companion animal pluripotent stem cells

Pluripotent stem cells have the capacity to grow indefinitely in culture and differentiate into derivatives of the three germ layers. These properties underpin their potential to be used in regenerative medicine. Originally derived from early embryos, pluripotent stem cells can now be derived by reprogramming an adult cell back to a pluripotent state. Companion animals such as horses, dogs, and cats suffer from many injuries and diseases for which regenerative medicine may offer new treatments. As many of the injuries and diseases are similar to conditions in humans the use of companion animals for the experimental and clinical testing of stem cell and regenerative medicine products would provide relevant animal models for the translation of therapies to the human field. In order to fully utilize companion animal pluripotent stem cells robust, standardized methods of characterization must be developed to ensure that safe and effective treatments can be delivered. In this review we discuss the methods that are available for characterizing pluripotent stem cells and the techniques that have been applied in cells from companion animals. We describe characteristics which have been described consistently across reports as well as highlighting discrepant results. Significant steps have been made to define the in vitro culture requirements and drive lineage specific differentiation of pluripotent stem cells in companion animal species. However, additional basic research to compare pluripotent stem cell types and define characteristics of pluripotency in companion animal species is still required. © 2017 International Society for Advancement of Cytometry.

Generation of Canine Induced Extraembryonic Endoderm-Like Cell Line That Forms Both Extraembryonic and Embryonic Endoderm Derivatives

Extraembryonic endoderm (XEN) cells are stem cell lines derived from primitive endoderm cells of inner cell mass in blastocysts. These cells have self-renewal properties and differentiate into visceral endoderm (VE) and parietal endoderm (PE) of the yolk sac. Recently, it has been reported that XEN cells can contribute to fetal embryonic endoderm, and their unique potency has been evaluated. In this study, we have described the induction and characterization of new canine stem cell lines that closely resemble to XEN cells. These cells, which we designated canine induced XEN (ciXEN)-like cells, were induced from canine embryonic fibroblasts by introducing four transgenes. ciXEN-like cells expressed XEN markers, which could be maintained over 50 passages in N2B27 medium supplemented with inhibitors of mitogen-activated protein kinase p38 and transforming growth factor-beta 1. Our ciXEN-like cells were maintained without transgene expression and exhibited upregulated expression of VE and PE markers in feeder-free conditions. The cells differentiated from ciXEN-like cells using a coculture system showed multiple nuclei and expressed albumin protein, similar to characteristics of hepatocytes. Furthermore, these cells expressed the adult hepatocyte marker, CYP3A4. Interestingly, these cells also formed a net structure expressing the bile epithelium capillary marker, multidrug resistance-associated protein 2. Thus, we have demonstrated the induction of a new canine stem cell line, ciXEN-like cells, which could form an embryonic endodermal cell layer. Our ciXEN-like cells may be a helpful tool to study the canine embryo development and represent a promising cell source for proceeding human and canine regenerative medicine.

Feeder-independent canine induced pluripotent stem cells maintained under serum-free conditions

Canine induced pluripotent stem cells (ciPSCs) are an attractive source for regenerative veterinary medicine, and may also serve as a disease model for human regenerative medicine. Extending the application of ciPSCs from bench to bedside, however, requires resolving many issues. We generated ciPSCs expressing doxycycline-inducible murine Oct3/4 (Pou5f1), Sox2, Klf4, and c-Myc, which were introduced using lentiviral vectors. The resultant ciPSCs required doxycycline to proliferate in the undifferentiated state. Those ciPSC colonies exhibiting basic fibroblast growth factor (bFGF)-dependent proliferation were dissociated into single cells for passaging, and were maintained on a Matrigel-coated dish without feeder cells in a serum-free medium. The established ciPSCs had the ability to differentiate into three germ layers, via formation of embryoid bodies, as well as into cells expressing the same markers as mesenchymal stem cells. These ciPSCs may thus serve as a suitable source of pluripotent stem cell lines for regenerative veterinary medicine, with fewer concerns of contamination from unknown animal components.

Generation of LIF-independent induced pluripotent stem cells from canine fetal fibroblasts

Takahashi and Yamanaka established the first technique in which transcription factors related to pluripotency are incorporated into the genome of somatic cells to enable reprogramming of these cells. The expression of these transcription factors enables a differentiated somatic cell to reverse its phenotype to an embryonic state, generating induced pluripotent stem cells (iPSCs). iPSCs from canine fetal fibroblasts were produced through lentiviral polycistronic human and mouse vectors (hOSKM/mOSKM), aiming to obtain pluripotent stem cells with similar features to embryonic stem cells (ESC) in this animal model. The cell lines obtained in this study were independent of LIF or any other supplemental inhibitors, resistant to enzymatic procedure (TrypLE Express Enzyme), and dependent on bFGF. Clonal lines were obtained from slightly different protocols with maximum reprogramming efficiency of 0.001%. All colonies were positive for alkaline phosphatase, embryoid body formation, and spontaneous differentiation and expressed high levels of endogenous OCT4 and SOX2. Canine iPSCs developed tumors at 120 days post-injection in vivo. Preliminary chromosomal evaluations were performed by FISH hybridization, revealing no chromosomal abnormality. To the best of our knowledge, this report is the first to describe the ability to reprogram canine somatic cells via lentiviral vectors without supplementation and with resistance to enzymatic action, thereby demonstrating the pluripotency of these cell lines.

Comparison of American mink embryonic stem and induced pluripotent stem cell transcriptomes

Background

Recently fibroblasts of many mammalian species have been reprogrammed to pluripotent state using overexpression of several transcription factors. This technology allows production of induced pluripotent stem (iPS) cells with properties similar to embryonic stem (ES) cells. The completeness of reprogramming process is well studied in such species as mouse and human but there is not enough data on other species. We produced American mink (Neovison vison) ES and iPS cells and compared these cells using transcriptome analysis.

Results

We report the generation of 10 mink ES and 22 iPS cell lines. The majority of the analyzed cell lines had normal diploid chromosome number. The only ES cell line with XX chromosome set had both X-chromosomes in active state that is characteristic of pluripotent cells. The pluripotency of ES and iPS cell lines was confirmed by formation of teratomas with cell types representing all three germ layers. Transcriptome analysis of mink embryonic fibroblasts (EF), two ES and two iPS cell lines allowed us to identify 11831 assembled contigs which were annotated. These led to a number of 6891 unique genes. Of these 3201 were differentially expressed between mink EF and ES cells. We analyzed expression levels of these genes in iPS cell lines. This allowed us to show that 80% of genes were correctly reprogrammed in iPS cells, whereas approximately 6% had an intermediate expression pattern, about 7% were not reprogrammed and about 5% had a "novel" expression pattern. We observed expression of pluripotency marker genes such as Oct4, Sox2 and Rex1 in ES and iPS cell lines with notable exception of Nanog.

Conclusions

We had produced and characterized American mink ES and iPS cells. These cells were pluripotent by a number of criteria and iPS cells exhibited effective reprogramming. Interestingly, we had showed lack of Nanog expression and consider it as a species-specific feature.

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.

Canine Pluripotent Stem Cells: Are They Ready for Clinical Applications?

The derivation of canine embryonic stem cells and generation of canine-induced pluripotent stem cells are significant achievements that have unlocked the potential for developing novel cell-based disease models, drug discovery platforms, and transplantation therapies in the dog. A progression from concept to cure in this clinically relevant companion animal will not only help our canine patients but also help advance human regenerative medicine. Nevertheless, many issues remain to be resolved before pluripotent cells can be used clinically in a safe and reproducible manner.

Development, Characterization, and Pluripotency Analysis of Buffalo (Bubalus bubalis) Embryonic Stem Cell Lines Derived from In Vitro-Fertilized, Hand-Guided Cloned, and Parthenogenetic Embryos

We present the derivation, characterization, and pluripotency analysis of three buffalo embryonic stem cell (buESC) lines, from in vitro-fertilized, somatic cell nuclear-transferred, and parthenogenetic blastocysts. These cell lines were developed for later differentiation into germ lineage cells and elucidation of the signaling pathways involved. The cell lines were established from inner cell masses (ICMs) that were isolated manually from the in vitro-produced blastocysts. Most of the ICMs (45-55%) resulted in formation of primary colonies that were subcultured after 8-10 days, leading subsequently to the formation of three buESC lines, one from each blastocyst type. All the cell lines expressed stem cell markers, such as Alkaline Phosphatase, OCT4, NANOG, SSEA1, SSEA4, TRA-1-60, TRA-1-81, SOX2, REX1, CD-90, STAT3, and TELOMERASE. They differentiated into all three germ layers as determined by ectodermal, mesodermal, and endodermal RNA and protein markers. All of the cell lines showed equal expression of pluripotency markers as well as equivalent differentiation potential into all the three germ layers. The static suspension culture-derived embryoid bodies (EBs) showed greater expression of all the three germ layer markers as compared to hanging drop culture-derived EBs. When analyzed for germ layer marker expression, EBs derived from 15% fetal bovine serum (FBS)-based spontaneous differentiation medium showed greater differentiation across all the three germ layers as compared to those derived from Knock-Out Serum Replacement (KoSR)-based differentiation medium.

Generation of induced pluripotent stem cells from domestic goats

The creation of genetically modified goats provides a powerful approach for improving animal health, enhancing production traits, animal pharming, and for ensuring food safety all of which are high-priority goals for animal agriculture. The availability of goat embryonic stem cells (ESCs) that are characteristically immortal in culture would be of enormous benefit for developing genetically modified animals. As an alternative to long-sought goat ESCs, we generated induced pluripotent stem cells (iPSC) by forced expression of bovine POU5F1, SOX2, MYC, KLF4, LIN-28, and NANOG reprogramming factors in combination with a MIR302/367 cluster, delivered by lentiviral vectors. In order to minimize integrations, the reprogramming factor coding sequences were assembled with porcine teschovirus-1 2A (P2A) self-cleaving peptides that allowed for tri-cistronic expression from each vector. The lentiviral-transduced cells were cultured on irradiated mouse feeder cells in a semi-defined, serum-free medium containing fibroblast growth factor (FGF) and/or leukemia inhibitory factor (LIF). The resulting goat iPSC exhibit cell and colony morphology typical of human and mouse ESCs-that is, well-defined borders, a high nuclear-to-cytoplasmic ratio, a short cell-cycle interval, alkaline phosphatase expression, and the ability to generate teratomas in vivo. Additionally, these goat iPSC demonstrated the ability to differentiate into directed lineages in vitro. These results constitute the first steps in establishing integration and footprint-free iPSC from ruminants. Mol. Reprod. Dev. 82: 709-721, 2015. © 2015 Wiley Periodicals, Inc.

The Dog: Nonconformist, Not Only in Maternal Recognition Signaling

Although similar at the molecular and cellular levels, endocrine mechanisms governing reproductive function in the domestic dog (Canis familiaris) differ markedly at the regulatory level from those known in other domestic animal species. Some of the events, e.g., the lack of luteolysis in the absence of pregnancy, resulting in similar luteal function and, therefore, hormonal profiles in early pregnant and nonpregnant animals, are species-specific. Consequently, no early gestation marker has so far been identified for the dog. Following implantation, relaxin of fetal placental origin can be detected and used for pregnancy diagnosis. Characterized by the lack of an active luteolytic principle from intra- or extra-luteal sources, the canine reproductive cycle appears to represent a "basic" form of mammalian reproductive function with apparently reduced opportunities for facilitating fecundity and hastening reproduction. Nevertheless, in the dog some kind of mechanism for synchronization between blastocyst development and uterine preparation for pregnancy must have evolved in order to support gestation. Driven by this assumption, studies including our recent investigations have been initiated aimed at characterizing some of the embryo-mediated effects of the preimplantation embryo on the canine uterus. Moreover, the lack of a uterine luteolysin and consequently the absence of a need to develop an antiluteolytic strategy make the dog an interesting model for investigating early evolutionary mechanisms involved in the preparation for implantation and ensuring embryo survival. These mechanisms result in an inverse relationship between the duration of pregnancy and of the nonpregnant cycle in the dog, compared with all other domestic animal species.

Transcriptome analysis of chicken ES, blastodermal and germ cells reveals that chick ES cells are equivalent to mouse ES cells rather than EpiSC

Pluripotent Embryonic Stem cell (ESC) lines can be derived from a variety of sources. Mouse lines derived from the early blastocyst and from primordial germ cells (PGCs) can contribute to all somatic lineages and to the germ line, whereas cells from slightly later embryos (EpiSC) no longer contribute to the germ line. In chick, pluripotent ESCs can be obtained from PGCs and from early blastoderms. Established PGC lines and freshly isolated blastodermal cells (cBC) can contribute to both germinal and somatic lineages but established lines from the former (cESC) can only produce somatic cell types. For this reason, cESCs are often considered to be equivalent to mouse EpiSC. To define these cell types more rigorously, we have performed comparative microarray analysis to describe a transcriptomic profile specific for each cell type. This is validated by real time RT-PCR and in situ hybridisation. We find that both cES and cBC cells express classic pluripotency-related genes (including cPOUV/OCT4, NANOG, SOX2/3, KLF2 and SALL4), whereas expression of DAZL, DND1, DDX4 and PIWIL1 defines a molecular signature for germ cells. Surprisingly, contrary to the prevailing view, our results also suggest that cES cells resemble mouse ES cells more closely than mouse EpiSC.

Stem cell therapies for treating osteoarthritis: prescient or premature?

There has been unprecedented interest in recent years in the use of stem cells as therapy for an array of diseases in companion animals. Stem cells have already been deployed therapeutically in a number of clinical settings, in particular the use of mesenchymal stem cells to treat osteoarthritis in horses and dogs. However, an assessment of the scientific literature highlights a marked disparity between the purported benefits of stem cell therapies and their proven abilities as defined by rigorously controlled scientific studies. Although preliminary data generated from clinical trials in human patients are encouraging, therapies currently available to treat animals are supported by very limited clinical evidence, and the commercialisation of these treatments may be premature. This review introduces the three main types of stem cells relevant to veterinary applications, namely, embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells, and draws together research findings from in vitro and in vivo studies to give an overview of current stem cell therapies for the treatment of osteoarthritis in animals. Recent advances in tissue engineering, which is proposed as the future direction of stem cell-based therapy for osteoarthritis, are also discussed.

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.

Germ cell specification and pluripotency in mammals: a perspective from early embryogenesis

Germ cells are unique cell types that generate a totipotent zygote upon fertilization, giving rise to the next generation in mammals and many other multicellular organisms. How germ cells acquire this ability has been of considerable interest. In mammals, primordial germ cells (PGCs), the precursors of sperm and oocytes, are specified around the time of gastrulation. PGCs are induced by signals from the surrounding extra-embryonic tissues to the equipotent epiblast cells that give rise to all cell types. Currently, the mechanism of PGC specification in mammals is best understood from studies in mice. Following implantation, the epiblast cells develop as an egg cylinder while the extra-embryonic ectoderm cells which are the source of important signals for PGC specification are located over the egg cylinder. However, in most cases, including humans, the epiblast cells develop as a planar disc, which alters the organization and the source of the signaling for cell fates. This, in turn, might have an effect on the precise mechanism of PGC specification in vivo as well as in vitro using pluripotent embryonic stem cells. Here, we discuss how the key early embryonic differences between rodents and other mammals may affect the establishment of the pluripotency network in vivo and in vitro, and consequently the basis for PGC specification, particularly from pluripotent embryonic stem cells in vitro.

Developmental Competence of Buffalo (Bubalus bubalis) Pluripotent Embryonic Stem Cells Over Different Homologous Feeder Layers and the Comparative Evaluation with Various Extracellular Matrices

BACKGROUND AND OBJECTIVES

Use of somatic cells as a feeder layer to maintain the embryonic stem cells (ESCs) in undifferentiated state limits the stem cell research design, since experimental data may result from a combined ESCs and feeder cell response to various stimuli. Therefore, present study was designed to evaluate the developmental competence of the buffalo ESCs over different homogenous feeders and compare with various extracellular matrices using different concentrations of LIF.

METHODS AND RESULTS

Inner cell masses (ICMs) of in vitro hatched blastocysts were cultured onto homologous feeders viz. fetal fibroblast, granulosa and oviductal cell feeder layers and synthetic matrices viz. fibronectin, collagen type I and matrigel in culture medium. Developmental efficiency was found higher for ESCs cultured on fetal fibroblast and granulosa layers (83.33%) followed by fibronectin (77.78%) at 30 ng LIF. Oviductal feeder was found to be the least efficient feeder showing only 11.11% undifferentiated primary ESC colonies at 30 ng LIF. However, neither feeder layer nor synthetic matrix could support the development of primary colonies at 10 ng LIF. Expression of SSEA- 4, TRA-1-60 and Oct-4 were found positive in ESC colonies from all the feeders and synthetic matrices with 20 ng and 30 ng LIF.

CONCLUSIONS

Fetal fibroblast and granulosa cell while, amongst synthetic matrices, fibronectin were found to be equally efficient to support the growth and maintenance of ESCs pluripotency with 30 ng LIF. This well-defined culture conditions may provide an animal model for culturing human embryonic stem cells in the xeno-free or feeder-free conditions for future clinical applications.

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.

Selection of appropriate isolation method based on morphology of blastocyst for efficient derivation of buffalo embryonic stem cells

The efficiency of embryonic stem cell (ESC) derivation from all species except for rodents and primates is very low. There are however, multiple interests in obtaining pluripotent cells from these animals with main expectations in the fields of transgenesis, cloning, regenerative medicine and tissue engineering. Researches are being carried out in laboratories throughout the world to increase the efficiency of ESC isolation for their downstream applications. Thus, the present study was undertaken to study the effect of different isolation methods based on the morphology of blastocyst for efficient derivation of buffalo ESCs. Embryos were produced in vitro through the procedures of maturation, fertilization and culture. Hatched blastocysts or isolated inner cell masses (ICMs) were seeded on mitomycin-C inactivated buffalo fetal fibroblast monolayer for the development of ESC colonies. The ESCs were analyzed for alkaline phosphatase activity, expression of pluripotency markers and karyotypic stability. Primary ESC colonies were obtained after 2-5 days of seeding hatched blastocysts or isolated ICMs on mitomycin-C inactivated feeder layer. Mechanically isolated ICMs attached and formed primary cell colonies more efficiently than ICMs isolated enzymatically. For derivation of ESCs from poorly defined ICMs intact hatched blastocyst culture was the most successful method. Results of this study implied that although ESCs can be obtained using all three methods used in this study, efficiency varies depending upon the morphology of blastocyst and isolation method used. So, appropriate isolation method must be selected depending on the quality of blastocyst for efficient derivation of ESCs.

Generation of functional platelets from canine induced pluripotent stem cells

Thrombocytopenia (TTP) is a blood disease common to canines and human beings. Currently, there is no valid therapy for this disease except blood transfusion. In this study, we report the generation of canine induced pluripotent stem cells (ciPSCs) from canine embryonic fibroblasts, and a novel protocol for creating mature megakaryocytes (MKs) and functional platelets from ciPSCs. The ciPSCs were generated using lentiviral vectors, and differentiated into MKs and platelets on OP9 stromal cells supplemented with growth factors. Our ciPSCs presented in a tightly domed shape and showed expression of a critical pluripotency marker, REX1, and normal karyotype. Additionally, ciPSCs differentiated into cells derived from three germ layers via the formation of an embryoid body. The MKs derived from ciPSCs had hyperploidy and transformed into proplatelets. The proplatelets released platelets early on that expressed specific MK and platelet marker CD41/61. Interestingly, these platelets, when activated with adenosine diphosphate or thrombin, bind to fibrinogen. Moreover, electron microscopy showed that the platelets had the same ultrastructure as peripheral platelets. Thus, we have demonstrated for the first time the generation of ciPSCs that are capable of differentiating into MKs and release functional platelets in vitro. Our system for differentiating ciPSCs into MKs and platelets promises a critical therapy for canine TTP and appears to be extensible in principle to resolve human TTP.

Monitoring bovine fetal fibroblast reprogramming utilizing a bovine NANOG promoter-driven EGFP reporter system

NANOG is an essential transcription factor involved in the proliferation and maintenance of embryonic stem cells (ESC) and reprogramming of somatic cells to a pluripotent state. Oct4 and Nanog promoter-driven enhanced green fluorescent protein (EGFP) reporters have been employed for establishing lines of induced pluripotent stem cells (iPSC) from mouse, human, and pig. In ruminants, including cattle, in which no fully validated ESC lines have been established, iPSC generated by reprogramming somatic cells to an ESC-like state may prove useful in the production of genetically modified livestock. In this study, utility of the bovine NANOG reporter was tested for use with cattle. Seven proximal bovine NANOG promoter fragments of different size were fused to the LUC gene, and were tested in mouse ESC lines using a dual-luciferase assay. Three of the bovine NANOG promoters, 315 bp (-134/+181), 446 bp (-265/+181), and 1,100 bp (-919/+181), were fused to a nuclear localized signal EGFP reporter gene. The fidelity of these constructs was analyzed by transfection into mouse ESC and bovine fetal fibroblasts (bFFs), and subsequent reprogramming of the bFF. Fusion of the transgenic bFF with human teratocarcinoma (NTERA2) cells induced nuclear expression of the EGFP reporter. Similarly, bFF-derived somatic cell nuclear transfer (SCNT) embryos expressed EGFP in a stage- and location-appropriate manner. Following reprogramming of transgenic bFFs for 10 days with an Oct4-Sox2-Klf4-cMyc vector, iPSC expressed EGFP and alkaline phosphatase. These results indicate that NANOG reporters can be used to monitor nuclear reprogramming of bFFs and to distinguish cell allocation in SCNT-derived embryos.

Livestock induced pluripotent stem cells

Chimeric animals generated from livestock-induced pluripotent stem cells (iPSCs) have opened the door of opportunity to genetically manipulate species for the production of biomedical models, improving traits of agricultural importance and potentially providing a system to test novel iPSC therapies. The potential of pluripotent stem cells in livestock has long been recognized, with many attempts being chronicled to isolate, culture and characterize pluripotent cells from embryos. However, in most cases, livestock stem cells derived from embryonic sources have failed to reach a pluripotent state marked by the inability to form chimeric animals. The in-depth understanding of core pluripotency factors and the realization of how these factors can be harnessed to reprogram adult cells into an induced pluripotent state has changed the paradigm of livestock stem cells. In this review, we will examine the advancements in iPSC technology in mammalian and avian livestock species.

Derivation and culture of canine embryonic stem cells

The derivation of canine embryonic stem cells (cESCs) represents a significant achievement and opens the door to further stem cell research and therapies in the dog. Canines share a common environment with humans and exhibit a host of genetic diseases, many of which have human parallels. Thus, the canine model presents unique advantages over other currently used organisms to help develop stem cell therapies in humans. To reveal the therapeutic potential of cESCs further basic research on the molecular mechanisms controlling their pluripotency and self-renewal characteristics is needed. Herein, we present the methods for derivation and culture of cESCs. Following collection of the canine blastocyst, two derivation methods are presented; immunodissection and whole blastocyst explant. These two methods lead to cESCs differing in morphology and subculture techniques. Additional protocols for subculture of established lines, feeder-free culture, and cryopreservation protocols are also described.

Growth requirements and chromosomal instability of induced pluripotent stem cells generated from adult canine fibroblasts

In mice and humans, it has been shown that embryonic and adult fibroblasts can be reprogrammed into pluripotency by introducing 4 transcription factors, Oct3/4, Klf4, Sox2, and c-Myc (OKSM). Here, we report the derivation of induced pluripotent stem cells (iPSCs) from adult canine fibroblasts by retroviral OKSM transduction. The isolated canine iPSCs (ciPSCs) were expanded in 3 different culture media [fibroblast growth factor 2 (FGF2), leukemia inhibitory factor (LIF), or FGF2 plus LIF]. Cells cultured in both FGF2 and LIF expressed pluripotency markers [POU5F1 (OCT4), SOX2, NANOG, and LIN28] and embryonic stem cell (ESC)-specific genes (PODXL, DPPA5, FGF5, REX1, and LAMP1) and showed strong levels of alkaline phosphatase expression. In vitro differentiation by formation of embryoid bodies and by directed differentiation generated cell derivatives of all 3 germ layers as confirmed by mRNA and protein expression. In vivo, the ciPSCs created solid tumors, which failed to reach epithelial structure formation, but expressed markers for all 3 germ layers. Array comparative genomic hybridization and chromosomal fluorescence in situ hybridization analyses revealed that while retroviral transduction per se did not result in significant DNA copy number imbalance, there was evidence for the emergence of low-level aneuploidy during prolonged culture or tumor formation. In summary, we were able to derive ciPSCs from adult fibroblasts by using 4 transcription factors. The isolated iPSCs have similar characteristics to ESCs from other species, but the exact cellular mechanisms behind their unique co-dependency on both FGF2 and LIF are still unknown.

Large animal induced pluripotent stem cells as pre-clinical models for studying human disease

The derivation of human embryonic stem cells and subsequently human induced pluripotent stem cells (iPSCs) has energized regenerative medicine research and enabled seemingly limitless applications. Although small animal models, such as mouse models, have played an important role in the progression of the field, typically, they are poor representations of the human disease phenotype. As an alternative, large animal models should be explored as a potentially better approach for clinical translation of cellular therapies. However, only fragmented information regarding the derivation, characterization and clinical usefulness of pluripotent large animal cells is currently available. Here, we briefly review the latest advances regarding the derivation and use of large animal iPSCs.

In vivo differentiation potential of buffalo (Bubalus bubalis) embryonic stem cell

Embryonic stem cells (ESCs) derived from inner cell mass (ICM) of mammalian blastocyst are having indefinite proliferation and differentiation capability for any type of cell lineages. In the present study, ICMs of in vitro-derived buffalo blastocysts were cultured into two different culture systems using buffalo fetal fibroblast as somatic cell support and Matrigel as synthetic support to obtain pluripotent buffalo embryonic stem cell (buESC) colonies. Pluripotency of the ESCs were characterised through pluripotency markers whereas, their differentiation capability was assessed by teratoma assay using immuno-compromised mice. Cumulus ooccyte complexes from slaughter house-derived ovaries were subjected to in vitro maturation, in vitro fertilization and in vitro culture to generate blastocysts. Total 262 blastocysts were derived through IVEP with 11.83 % (31/262) hatching rate. To generate buESCs, 15 ICMs from hatched blastocysts were cultured on mitomycin-C-treated homologous fetal fibroblast feeder layer, whereas the leftover 16 ICMs were cultured on extra-cellular matrix (Matrigel). No significant differences were observed for primary ESCs colony formation between two culture systems. Primary colonies as well as passaged ESCs were characterised by alkaline phosphatase staining, karyotyping and expression of transcription-based stem cell markers, OCT-4 and cell surface antigens SSEA-4 and TRA-1-60. Batch of ESCs found positive for pluripotency markers and showing normal karyotype after fifteenth passage were inoculated into eight immuno-compromised mice through subcutaneous and intramuscular route. Subcutaneous route of inoculation was found to be better than intramuscular route. Developed teratomas were excised surgically and subjected to histological analysis. Histological findings revealed presence of all the three germinal layer derivatives in teratoma sections. Presence of germinal layer derivatives were further confirmed by reverse transcriptase-polymerase chain reaction for the presence of differentiation markers like nerve cell adhesion molecule, fetal liver kinase-1 and alpha-feto protein for ectoderm, mesoderm and endoderm, respectively.

Equivalency of buffalo (Bubalus bubalis) embryonic stem cells derived from fertilized, parthenogenetic, and hand-made cloned embryos

This study was aimed at establishing buffalo embryonic stem cells (ESCs) from in vitro fertilized (IVF), parthenogenetic, and hand-made cloned (HMC) embryos and to check their equivalency in terms of stem cell marker expression, longevity, proliferation, and differentiation pattern. ESCs derived from all three sources were found by immunofluorescence to express the pluripotency markers SSEA-4, TRA-1-60, TRA-1-81, OCT4, and SOX2 and were able to form embryoid bodies containing cells expressing genes specific to endoderm (AFP, HNF4, and GATA4), mesoderm (MSX1, BMP4, and ASA), and ectoderm (cytokeratin 8 and NF68). Reverse transcriptase PCR (RT-PCR) showed cells from all sources to be positive for pluripotency markers OCT4, SOX2, NANOG, STAT3, REX1, FOXD3, NUCLEOSTEMIN, and TELOMERASE. Pluripotency markers OCT4, SOX2, NANOG, and c-MYC were also analyzed by real-time PCR. No significant differences were observed among ESCs from all three sources for all these genes except NANOG, whose expression was higher (p<0.05) in HMC-derived ESCs (6.897±2.3) compared to that in parthenogenesis- and IVF-derived cells (1.603±0.315 and 1±0, respectively). Pluripotent, stable buffalo ESC lines derived from IVF, parthenogenesis, and HMC embryos may be genetically manipulated to provide a powerful tool for studies involving embryonic development, genomic imprinting, gene targeting, cloning, chimera formation, and transgenic animal production.

Generation and characterization of LIF-dependent canine induced pluripotent stem cells from adult dermal fibroblasts

Dogs provide a more clinically relevant model of human disease than rodents, particularly with respect to hereditary diseases. Thus, the availability of canine stem cells will greatly facilitate the use of the dog in the development of stem cell-based gene therapies and regenerative medicine. In this study we describe the production of canine induced pluripotent stem cells (ciPSCs) from adult dermal fibroblasts. These cells have a morphology resembling previously described canine embryonic stem cells, a normal karyotype, and express pluripotency markers including alkaline phosphatase, Nanog, Oct4, Telomerase, SSEA1, SSEA4, TRA1-60, TRA1-81, and Rex1. Furthermore, the inactive X chromosome is reactivated indicating a ground-state pluripotency. In culture they readily form embryoid bodies, which in turn give rise to cell types from all 3 embryonic germ layers, as indicated by expression of the definitive endoderm markers Cxcr4 and α-fetoprotein, mesoderm markers Collagen IIA and Gata2, and ectoderm markers βIII-tubulin, Enolase, and Nestin. Of particular significance is the observation that these ciPSCs are dependent only on leukemia inhibitory factor (LIF), making them similar to mouse and canine embryonic stem cells, but strikingly unlike the ciPSCs recently described in two other studies, which were dependent on both basic fibroblast growth factor and LIF in order to maintain their pluripotency. Thus, our ciPSCs closely resemble mouse ESCs derived from the inner cell mass of preimplantation embryos, while the previously described ciPSCs appear to be more representative of cells from the epiblast of mouse postimplantation embryos.

Generation of SV40-transformed rabbit tracheal-epithelial-cell-derived blastocyst by somatic cell nuclear transfer

The prospect of developing large animal models for the study of inherited diseases, such as cystic fibrosis (CF), through somatic cell nuclear transfer (SCNT) has opened up new opportunities for enhancing our understanding of disease pathology and for identifying new therapies. Thus, the development of species-specific in vitro cell systems that will provide broader insight into organ- and cell-type-specific functions relevant to the pathology of the disease is crucial. Studies have been undertaken to establish transformed rabbit airway epithelial cell lines that display differentiated features characteristic of the primary airway epithelium. This study describes the successful establishment and characterization of two SV40-transformed rabbit tracheal epithelial cell lines. These cell lines, 5RTEo- and 9RTEo-, express the CF transmembrane conductance regulator (CFTR) gene, retain epithelial-specific differentiated morphology and show CFTR-based cAMP-dependent Cl(-) ion transport across the apical membrane of a confluent monolayer. Immunocytochemical analysis indicates the presence of airway cytokeratins and tight-junction proteins in the 9RTEo- cell line after multiple generations. However, the tight junctions appear to diminish in their efficacy in both cell lines after at  least 100 generations. Initial SCNT studies with the 9RTEo- cells have revealed that SV40-transformed rabbit airway epithelial donor cells can be used to generate blastocysts. These cell systems provide valuable models for studying the developmental and metabolic modulation of CFTR gene expression and rabbit airway epithelial cell biology.

Generation of leukemia inhibitory factor and basic fibroblast growth factor-dependent induced pluripotent stem cells from canine adult somatic cells

For more than thirty years, the dog has been used as a model for human diseases. Despite efforts made to develop canine embryonic stem cells, success has been elusive. Here, we report the generation of canine induced pluripotent stem cells (ciPSCs) from canine adult fibroblasts, which we accomplished by introducing human OCT4, SOX2, c-MYC, and KLF4. The ciPSCs expressed critical pluripotency markers and showed evidence of silencing the viral vectors and normal karyotypes. Microsatellite analysis indicated that the ciPSCs showed the same profile as the donor fibroblasts but differed from cells taken from other dogs. Under culture conditions favoring differentiation, the ciPSCs could form cell derivatives from the ectoderm, mesoderm, and endoderm. Further, the ciPSCs required leukemia inhibitory factor and basic fibroblast growth factor to survive, proliferate, and maintain pluripotency. Our results demonstrate an efficient method for deriving canine pluripotent stem cells, providing a powerful platform for the development of new models for regenerative medicine, as well as for the study of the onset, progression, and treatment of human and canine genetic diseases.

Isolation and culture of embryonic stem-like cells from pig nuclear transfer blastocysts of different days

This study was conducted to establish pig embryonic stem (ES)-like cell lines from nuclear transfer blastocysts. A green fluorescent protein (GFP)-expressing cell line was used as the source of donor cells injected into the enucleated oocytes. Blastocysts were collected at D5 (the fifth day), D7 (the seventh day) and D9 (the ninth day). Differential staining was used to assay the viability and development of blastocysts from the 3 days. The number of inner cell mass (ICM) cells increased from 1.83 ± 0.8 (D5) to 5.37 ± 1.2 (D7) to 7.56 ± 1.5 (D9). The expression profiles of embryonic stem (ES) cell factors (OCT4, SOX2, KLF4 and c-MYC) correlated best with the undifferentiated ES state and were identified by qPCR. The expression of the four factors was increased from D5 to D7, whereas the expression decreased from D7 to D9. We tried to isolate ES-like cells from these embryos. However, ES-like cells from the D7 blastocysts grew slowly and expressed alkaline phosphatase. The cells from the D9 blastocysts grew rapidly but did not express alkaline phosphatase. ES-like cells were not isolated from the D5 blastocysts. These results show that the cells from the D7 embryos are pluripotent but grow slowly. The cells from the D9 embryos grow rapidly but start to lose pluripotency.

Derivation of buffalo embryonic stem-like cells from in vitro-produced blastocysts on homologous and heterologous feeder cells

PURPOSE

The aim of the present study is to compare the ability of homologous and heterologous embryonic fibroblast feeder layers to support isolation and proliferation of buffalo ES-like cells generated from hatched and expanded blastocysts produced by in vitro fertilization and characterization of derived cells through expression of pluripotent markers.

METHODS

Embryonic stem cells were derived from hatched and expanded blastocysts through intact blastocyst culture and enzymatic method respectively and compared for proliferation rate on homologous (buffalo) and heterologous feeder layers (goat and sheep).

RESULTS

A total of 69 hatched and 83 expanded blastocysts were used for isolation of inner cell masses which were seeded on buffalo, goat and sheep embryonic feeder layers. Following seeding, attachment rate, primary colony formation rate and survival to maximum number of passages were observed to be higher on homologous feeder layers.

CONCLUSIONS

Upon comparison of different feeder layer cells for derivation and maintenance of buffalo ES-like cells from hatched and expanded blastocysts, buffalo embryonic fibroblast cells were able to provide a better environment for maintaining pluripotency in culture conditions.

Early development and putative primordial germ cells characterization in dogs

Previously, three distinct populations of putative primordial germ cells (PGCs), namely gonocytes, intermediate cells and pre-spermatogonia, have been described in the human foetal testis. According to our knowledge, these PGCs have not been studied in any other species. The aim of our study was to identify similar PGC populations in canine embryos. First, we develop a protocol for canine embryo isolation. Following our protocol, 15 canine embryos at 21-25 days of pregnancy were isolated by ovaryhysterectomy surgery. Our data indicate that dramatic changes occur in canine embryo development and PGCs specification between 21 to 25 days of gestation. At that moment, only two PGC populations with distinct morphology can be identified by histological analyses. Cell population 1 presented round nuclei with prominent nucleolus and a high nuclear to cytoplasm ratio, showing gonocyte morphology. Cell population 2 was often localized at the periphery of the testicular cords and presented typical features of PGC. Both germ cell populations were positively immunostained with anti-human OCT-4 antibody. However, at day 25, all cells of population 1 reacted positively with OCT-4, whereas in population 2, fewer cells were positive for this marker. These two PGCs populations present morphological features similar to gonocytes and intermediate cells from human foetal testis. It is expected that a population of pre-spermatogonia would be observed at later stages of canine foetus development. We also showed that anti-human OCT-4 antibody can be useful to identify canine PGC in vivo.