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

Establishment of feline embryonic stem cells from the inner cell mass of blastocysts produced in vitro

Introduction

The rising number of cats as pets and the growing interest in animal welfare have led to an increased need for the latest treatments in feline veterinary medicine. Among these, veterinary regenerative medicine using pluripotent stem cells is gaining significant attention. However, there have been no reports on establishing feline embryonic stem cell (ESC) lines that possess the pluripotent potential and the ability to differentiate into three germ layers.

Methods

In this study, we isolated three inner cell masses from feline in vitro-derived blastocysts and subcultured them in a chemically defined medium (StemFit AK02N). We assessed the expression of undifferentiated markers, the ability to differentiate into the three germ layers, and the karyotype structure.

Results

We established three feline ESC lines. Feline ESCs exhibited positive staining for alkaline phosphatase. RT-qPCR analysis revealed that these cells express undifferentiated marker genes in vitro. Immunostaining and flow cytometry analysis demonstrated that feline ESCs express undifferentiated marker proteins in vitro. In the KSR/FBS medium with or without Activin A, feline ESCs differentiated into all three germ layers (ectoderm, endoderm, and mesoderm), expressing specific marker genes and proteins for each germ layer, as evidenced by RT-qPCR, immunostaining, and flow cytometry. Furthermore, we confirmed that feline ESCs formed teratomas comprising all three germ layers in mouse testes, demonstrating de novo pluripotency in vivo. We also verified that the feline ESCs maintained a normal karyotype.

Conclusions

We successfully established three feline ESC lines, each possessing pluripotent potential and capable of differentiating into all three germ layers, derived from the inner cell masses of blastocysts produced in vitro.

Generation of footprint-free, high-quality feline induced pluripotent stem cells using Sendai virus vector

Companion animals, such as felines and canines, could provide an excellent platform for translational research from veterinary to human medicine. However, the use of feline induced pluripotent stems (fiPSCs) of quality in basic or clinical research has not been reported. Here, we generated footprint-free fiPSCs derived from embryonic cells, as well as juvenile feline uterus-derived cells using Sendai virus vector harboring six feline-specific pluripotency-associated genes. The fiPSCs were confirmed to be of high quality with the potential to form teratomas including all three germ layers. Furthermore, our fiPSCs were maintained under feeder-free and chemically-defined conditions using StemFit® AK02N and recombinant laminin 511, iMatrix-511. Further research on fiPSCs could result in their widespread application in veterinary regenerative medicine, which could pave the way for their use in advanced regenerative medicine research for humans.

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.

Exogenous pyruvate and recombinant human basic fibroblast growth factor maintain pluripotency and enhance global metabolic activity of bovine embryonic stem cells grown on low-density feeder layers

A suitable microenvironment or niche is essential for self-renewal and pluripotency of stem cells cultured in vitro, including bovine embryonic stem cells (bESCs). Feeder cells participate in the construction of stem cell niche by secreting growth factors and extracellular matrix proteins. In this study, metabolomics and transcriptomics analyses were used to investigate the effects of low-density feeder cells on bESCs. The results showed that bESCs co-cultured with low-density feeder cells experienced a decrease in pluripotent gene expression, cell differentiation, and a reduction of central carbon metabolic activity. When cell-permeable pyruvate (Pyr) and recombinant human basic fibroblast growth factor (rhbFGF) were added to the culture system, the pluripotency of bESCs on low-density feeder layers was rescued, and acetyl-coenzyme A (AcCoA) synthesis and fatty acid de novo synthesis increased. In addition, rhbFGF enhances the effects of Pyr and activates the overall metabolic level of bESCs grown on low-density feeder layers. This study explored the rescue effects of exogenous Pyr and rhbFGF on bESCs cultured on low-density feeder layers, which will provide a reference for improvement of the PSC culture system through the supplementation of energy metabolites and growth factors.

Establishment of fishing cat cell biobanking for sustainable conservation

The fishing cat (Prionailurus viverrinus) is a vulnerable wild felid that is currently under threat from habitat destruction and other human activities. The zoo provides insurance to ensure the survival of the fishing cat population. Creating a biobank of fishing cats is a critical component of recent zoo strategies for securely stocking cell samples for long-term survival. Here, our goal was to compare cell biobanking techniques (tissue collection, primary culture, and reprogramming) and tissue sources (ear skin, abdominal skin, testis) from captive (n = 6)/natural (n = 6) vs. living (n = 8)/postmortem (n = 4) fishing cats. First, we show that dermal fibroblasts from the medial border of the helix of the ear pinna and abdominal tissues of living fishing cats can be obtained, whereas postmortem animals provided far fewer fibroblasts from the ears than from the testes. Furthermore, we can extract putative adult spermatogonial stem cells from the postmortem fishing cat's testes. The main barrier to expanding adult fibroblasts was early senescence, which can be overcome by overexpressing reprogramming factors through felid-specific transfection programs, though we demonstrated that reaching iPSC state from adult fibroblasts of fishing cats was ineffective with current virus-free mammal-based induction approaches. Taken together, the success of isolating and expanding primary cells is dependent on a number of factors, including tissue sources, tissue handling, and nature of limited replicative lifespan of the adult fibroblasts. This study provides recommendations for tissue collection and culture procedures for zoological research to facilitate the preservation of cells from both postmortem and living felids.

Feeding role of mouse embryonic fibroblast cells is influenced by genetic background, cell passage and day of isolation

Mouse embryonic fibroblast (MEF) cells are commonly used as feeder cells to maintain the pluripotent state of stem cells. MEFs produce growth factors and provide adhesion molecules and extracellular matrix (ECM) compounds for cellular binding. In the present study, we compared the expression levels of Fgf2, Bmp4, ActivinA, Lif and Tgfb1 genes at the mRNA level and the level of Fgf2 protein secretion and Lif cytokine secretion at passages one, three and five of MEFs isolated from 13.5-day-old and 15.5-day-old embryos of NMRI and C57BL/6 mice using real-time PCR and enzyme-linked immunosorbent assay. We observed differences in the expression levels of the studied genes and secretion of the two growth factors in the three passages of MEFs isolated from 13.5-day-old and 15.5-day-old embryos, respectively. These differences were also observed between the NMRI and C57BL/6 strains. The results of this study suggested that researchers should use mice embryos that have different genetic backgrounds and ages, in addition to different MEF passages, when producing MEFs based on the application and type of their study.

Derivation of Ringed Seal (Phoca hispida) Induced Multipotent Stem Cells

Induced pluripotent stem (iPS) cells have been produced just for a few species among order Carnivora: snow leopard, Bengal tiger, serval, jaguar, cat, dog, ferret, and American mink. We applied the iPS cell derivation protocol to the ringed seal (Phoca hispida) fibroblasts. The resulting cell line had the expression of pluripotency marker gene Rex1. Differentiation in embryoid body-like structures allowed us to register expression of AFP, endoderm marker, and Cdx2, trophectoderm marker, but not neuronal (ectoderm) markers. The cells readily differentiated into adipocytes and osteocytes, mesoderm cell types of origin. Transcriptome analysis allowed us to conclude that the cell line does not resemble human pluripotent cells, and, therefore, most probably is not pluripotent. Thus, we produced ringed seal multipotent stem cell line capable of differentiation into adipocytes and osteocytes.

WNT signalling supported by MEK/ERK inhibition is essential to maintain pluripotency in bovine preimplantation embryo

Capturing stable embryonic stem cell (ESC) lines from domesticated animals still remains one of the challenges of non-rodent embryology. The stake is high, as stable ESCs derived from species such as cattle present high economic and scientific value. Understanding of the processes leading to the embryonic lineage segregation is crucial to provide species-orientated molecular environment capable of supporting self-renewal and pluripotency. Therefore, the aim of this study was to validate the action of the two core regulatory pathways (WNT and MEK/ERK) during bovine embryo development. In vitro produced bovine embryos were obtained in the presence of inhibitors (i), which enable activation of the WNT pathway (via GSK3i, CHIR99021) and suppression of MEK signalling by PD0325901 in the 2i system and PD184325 and SU5402 in the 3i system. We have followed the changes in the distribution of the key lineage specific markers both at the transcript and protein level. Our results showed that WNT signalling promotes the expression of key inner cell mass (ICM) specific markers in bovine embryos, regardless of the MEK/ERK inhibitor cocktail used. MEK/ERK downregulation is crucial to maintain OCT4 and NANOG expression within the ICM and to prevent their exclusion from the trophectoderm (TE). At the same time, the classical TE marker (CDX2) was downregulated at the mRNA and protein level. As a follow up for the observed pluripotency stimulating effect of the inhibitors, we have tested the potential of the 2i and the 3i culture conditions (supported by LIF) to derive primary bovine ESC lines. As a result, we propose a model in which all of the primary signalling pathways determining embryonic cell fate are active in bovine embryos, yet the requirement for pluripotency maintenance in cattle may differ from the described standards. WNT activation leads to the formation (and stabilisation of the ICM) and MEK/ERK signalling is maintained at low levels. Unlike in the mouse, GATA6 is expressed in both ICM and TE. MEK/ERK signalling affects HP formation in cattle, but this process is activated at the post-blastocyst stage. With regard to self-renewal, 2i is preferable, as 3i also blocks the FGF receptor, what may prevent PI3K signalling, important for pluripotency and self-renewal.

Reproductive biology and biotechnologies in wild felids

Conservation strategies in natural habitats as well as in breeding centers are necessary for maintaining and reinforcing viable populations of wild felids. Among the fundamental knowledge that is required for conservation breeding, a solid understanding of reproductive biology is critical for improving natural breeding and enhance genetic diversity. Additionally, it offers the opportunity to develop assisted reproductive technologies (ARTs) in threatened and endangered species. Conservation breeding and reproductive biotechnologies of wild felids have advanced in the past decade. It has been clearly shown that female felids have species and individual patterns of reproductive cycles and respond differently to exogenous hormones. In males, several species still have poor semen quality often due to the loss of genetic diversity in small populations. To overcome the challenges of natural breeding (incompatibility between individuals or suboptimal environment) and mitigate inbreeding, artificial insemination, embryo production and embryo transfer have been further developed in 24 wild cat species. Major factors limiting ART success are inconsistent responses to ovarian stimulation, variable quality of gametes and embryos, and preparation of recipient females. Additional approaches including stem cell technologies have been explored for future medical applications. However, there still is a critical need for better knowledge of feline reproductive biology and improvement of ARTs efficiency to increase the genetic diversity and create sustainable populations of wild felids.

In vitro and in vivo development of domestic cat embryos generated by in vitro fertilization after eCG priming and oocyte in vitro maturation

The objective of this study was to evaluate, in the domestic cat, the effect of ovarian stimulation with eCG prior to oocyte in vitro maturation (priming) on in vitro and in vivo development after in vitro fertilization (IVF). For this purpose, oocyte donors were either 1) treated with a single dose of 200 IU eCG four days before oocyte recovery (eCG group), or, 2) given no treatment before oocyte recovery (control group). Ovaries of both groups were collected by ovariohysterectomy (OVH) and cumulus-oocyte complexes (COCs) were recovered by slicing. Immature COCs from both groups were matured in vitro (IVM) for 26-28 h. IVF was done with refrigerated epididymal sperm. After 24 h co-incubation, presumptive zygotes were cultured in vitro for eight days. The rates of cleavage, morulae, blastocyst development and hatching were estimated. Some blastocysts were stained for total cell counting and others were used for gene expression analysis of pluripotency (OCT4, SOX2 and NANOG) and differentiation markers (CDX2 and GATA6). Additionally, to evaluate in vivo development, embryos from the eCG group were transferred at Day 5 and Days 7 or 8 of IVC to synchronized cat recipients. The results showed that, eCG priming increased significantly the rate of blastocyst development as compared to the control group (37.9 and 25.6%, respectively) (P < 0.05). No differences were observed in total cell number of blastocysts and hatching blastocysts (mean ± SD) between the eCG and control groups (420.6 ± 193.6 and 347.0 ± 237.1, respectively) (P > 0.05). In the gene expression analysis, blastocysts generated in the eCG group had higher expression of OCT4 than blastocysts from the control group (P < 0.05). However, no significant differences were observed in the relative expression of SOX2, NANOG, CDX2 and GATA6 (P > 0.05). Additionally, six embryo transfer (ET) procedures were done, three with Day 5 embryos and three with Day 7 or 8 embryos. Recipients from both ET groups delivered live kittens. The total pregnancy rate was 4/6 (67%), meanwhile the live birth rate was 2/6 (33%). In conclusion, eCG priming improved the rate of blastocyst development in vitro and increased relative expression of OCT4. These results demonstrate that eCG priming of oocytes donors before IVM improves oocyte competence, enhance in vitro embryo development and allows live births of healthy offspring after ET.

Inducing Pluripotency in the Domestic Cat (Felis catus)

Domestic cats suffer from a range of inherited genetic diseases, many of which display similarities with equivalent human conditions. Developing cellular models for these inherited diseases would enable drug discovery, benefiting feline health and welfare as well as enhancing the potential of cats as relevant animal models for translation to human medicine. Advances in our understanding of these diseases at the cellular level have come from the use of induced pluripotent stem cells (iPSCs). iPSCs can differentiate into virtually any cell type and can be derived from adult somatic cells, therefore overcoming the ethical implications of destroying embryos to obtain embryonic stem cells. No studies, however, report the generation of iPSCs from domestic cats [feline iPSCs (fiPSCs)]. Feline adipose-derived fibroblasts were infected with amphotropic retrovirus containing the coding sequences for human Oct4, Sox2, Klf4, cMyc, and Nanog. Isolated iPSC clones were expanded on inactivated mouse embryonic fibroblasts in the presence of feline leukemia inhibitory factor (fLIF). Retroviral delivery of human pluripotent genes gave rise to putative fiPSC colonies within 5-7 days. These iPS-like cells required fetal bovine serum and fLIF for maintenance. Colonies were domed with refractile edges, similar to mouse iPSCs. Immunocytochemistry demonstrated positive staining for stem cell markers: alkaline phosphatase, Oct4, Sox2, Nanog, and SSEA1. Cells were negative for SSEA4. Expression of endogenous feline Nanog was confirmed by quantitative polymerase chain reaction. The cells were able to differentiate in vitro into cells representative of the three germ layers. These results confirm the first generation of induced pluripotent stem cells from domestic cats. These cells will provide valuable models to study genetic diseases and explore novel therapeutic strategies.

Endogenous pluripotent factor expression after reprogramming cat fetal fibroblasts using inducible transcription factors

Incomplete transgene-silencing remains a challenge in the generation of induced pluripotent stem cells (iPSC) in felids-a critical family in biomedical and biodiversity conservation science. In this study doxycycline-inducible transgenes (NANOG, POU5F1, SOX2, KLF4, and cMYC) were used to reprogram cat fetal fibroblasts with the objective of obtaining iPSC with fully silenced transgenes. Colony formation was slower (14 vs. 8 days) and at lower efficiency than mouse embryonic fibroblasts (0.002% vs. 0.02% of seeded cells). Alkaline-phosphatase positive colonies were grown on feeder cells plus LIF and GSK3, MEK, and ROCK inhibitors. Cells could be passaged singly and transgene expression was silenced at passage 3 (P3) after doxycycline removal at P2. NANOG, POU5F1, and SOX2 were expressed at P3, P6, and P10, although at lower immunostaining intensities than in cat inner cell masses (ICM). Transcripts related to pluripotency (NANOG, POU5F1, SOX2, KLF4, cMYC, and REX1) and differentiation (FGF5, TBXT, GATA6, SOX17, FOXF1, PAX6, and SOX1) were assessed by a reverse transcription-quantitative polymerase chain reaction in iPSC and embryoid bodies. The immunostaining patterns, relatively low levels of NANOG and REX1 in comparison to ICM along with the expression of TBXT (mesoderm) suggested that cells were a mix of reprogrammed pluripotent and differentiating cells.

States and Origins of Mammalian Embryonic Pluripotency In Vivo and in a Dish

Mouse embryonic stem cells (ESC), derived from preimplantation embryos in 1981, defined mammalian pluripotency for many decades. However, after the derivation of human ESC in 1998, comparative studies showed that different types of pluripotency exist in early embryos and that these can be captured in vitro under various culture conditions. Over the past decade much has been learned about the key signaling pathways, growth factor requirements, and transcription factor profiles of pluripotent cells in embryos, allowing improvement of derivation and culture conditions for novel pluripotent stem cell types. More recently, studies using single-cell transcriptomics of embryos from different species provided an unprecedented level of resolution of cellular interactions and cell fate decisions that are informing new ways to understand the emergence of pluripotency in different organisms. These new approaches enhance knowledge of species differences during early embryogenesis and will be instrumental for improving methodologies for generating intra- and interspecies chimeric animals using pluripotent stem cells. Here, we discuss the recent developments in our understanding of early embryogenesis in different mammalian species.

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.

Progress of stem/progenitor cell-based therapy for retinal degeneration

Retinal degeneration (RD), such as age-related macular degeneration (AMD) and retinitis pigmentosa, is one of the leading causes of blindness. Presently, no satisfactory therapeutic options are available for these diseases principally because the retina and retinal pigmented epithelium (RPE) do not regenerate, although wet AMD can be prevented from further progression by anti-vascular endothelial growth factor therapy. Nevertheless, stem/progenitor cell approaches exhibit enormous potential for RD treatment using strategies mainly aimed at the rescue and replacement of photoreceptors and RPE. The sources of stem/progenitor cells are classified into two broad categories in this review, which are (1) ocular-derived progenitor cells, such as retinal progenitor cells, and (2) non-ocular-derived stem cells, including embryonic stem cells, induced pluripotent stem cells, and mesenchymal stromal cells. Here, we discuss in detail the progress in the study of four predominant stem/progenitor cell types used in animal models of RD. A short overview of clinical trials involving the stem/progenitor cells is also presented. Currently, stem/progenitor cell therapies for RD still have some drawbacks such as inhibited proliferation and/or differentiation in vitro (with the exception of the RPE) and limited long-term survival and function of grafts in vivo. Despite these challenges, stem/progenitor cells represent the most promising strategy for RD treatment in the near future.

FSH stimulation of anestrous cats improves oocyte quality and development of parthenogenetic embryos

In the domestic cat, the efficiency of in vitro embryo production systems is negatively affected during the nonbreeding season. The objective of this research was to evaluate the effect of FSH stimulation in anestrous cats, on quality of cumulus-oocyte complexes (COCs) and in vitro developmental competence after parthenogenetic activation. To accomplish this purpose, anestrous cats were grouped into: (1) FSH treated (serial doses of 5 mg of porcine FSH each, every 24 hours, for 4 days) and (2) untreated control. The COCs were classified morphologically and a proportion of grade I and II COCs was used for expression analysis of FSHR, LHCGR, EGFR, PTGS2, EGR1, GDF9, and GATM by RT-qPCR. In addition, another proportion of grade I and II COCs was matured in vitro and used for parthenogenetic activation. After 8 days in culture, blastocyst and hatching blastocyst rates were assessed, and the expression of OCT4, SOX2, NANOG, CDX2, and GATA6 was evaluated. The COCs in the FSH group had an enhanced quality, a higher expression of LHCGR and a lower expression of GATM than did COCs from the control group (P < 0.05). Furthermore, embryos in the FSH group had increased blastocyst and hatching blastocyst rates, and those embryos had a higher expression of OCT4 and GATA than their counterparts from the control group (P < 0.05). In conclusion, ovarian stimulation of anestrous cats with FSH improved quality and increased the expression of LHCGR in COCs. The enhanced in vitro developmental competence, after parthenogenetic activation of oocytes from FSH-treated cats, coincided with an increased expression of OCT4 and GATA6 in blastocysts and hatching blastocysts.

Effects of Feeder Cell Types on Culture of Mouse Embryonic Stem Cell In Vitro

The suitable feeder cell layer is important for culture of embryonic stem (ES) cells. In this study, we investigated the effect of two kinds of the feeder cell, MEF cells and STO cells, layer to mouse ES (mES) cell culture for maintenance of stemness. We compare the colony formations, alkaline phosphatase (AP) activities, expression of pluripotency marker genes and proteins of D3 cell colonies cultured on MEF feeder cell layer (D3/MEF) or STO cell layers (D3/STO) compared to feeder free condition (D3/-) as a control group. Although there were no differences to colony formations and AP activities, interestingly, the transcripts level of pluripotency marker genes, Pou5f1 and Nanog were highly expressed in D3/MEF (79 and 93) than D3/STO (61and 77) or D3/- (65 and 81). Also, pluripotency marker proteins, NANOG and SOX-2, were more synthesized in D3/MEF (72.8±7.69 and 81.2±3.56) than D3/STO (32.0±4.30 and 56.0±4.90) or D3/- (55.0±4.64 and 62.0±6.20). These results suggest that MEF feeder cell layer is more suitable to mES cell culture.

Total Cell Number and its Allocation to Trophectoderm and Inner Cell Mass in In Vitro Obtained Cats' Blastocysts

The aim of this study was to evaluate the developmental kinetics of cats' blastocysts in connection with their morphology and blastomeres allocation to trophoblast or embryoblast cells. We examined gross blastocyst morphology and the total number of blastomeres together with its allocation to inner cell mass (ICM) or trophectoderm (TE) cells in pre-implantation feline embryos obtained from 6th to 9th day of in vitro culture. From all the investigated embryos, 61.8% developed to early blastocyst, 37.4% to full and 7.6% to hatching blastocyst stage. The total cell number (TCN) varied form 58 cells in early day 6 to 245 in hatching day 8 blastocyst, with the mean 84.9 cells in early, 156.7 in full, and 204.4 in hatching ones. Day 8 blastocyst had the highest number of total cells, together with the highest mean number of ICM regardless of its morphological assessment. Early blastocyst (apart from day 6) had the highest number of arrested cells, while dead cells were the highest in full day 9 blastocyst. More data about the relationship between blastocyst development and morphology would facilitate the selection of optimal blastocysts for further procedures.

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.

Cheetah interspecific SCNT followed by embryo aggregation improves in vitro development but not pluripotent gene expression

The aim of this study was to evaluate the capacity of domestic cat (Dc,Felis silvestris) oocytes to reprogram the nucleus of cheetah (Ch,Acinonyx jubatus) cells by interspecies SCNT (iSCNT), by using embryo aggregation. Dc oocytes werein vitromatured and subjected to zona pellucida free (ZP-free) SCNT or iSCNT, depending on whether the nucleus donor cell was of Dc or Ch respectively. ZP-free reconstructed embryos were then cultured in microwells individually (Dc1X and Ch1X groups) or in couples (Dc2X and Ch2X groups). Embryo aggregation improvedin vitrodevelopment obtaining 27.4, 47.7, 16.7 and 28.3% of blastocyst rates in the Dc1X, Dc2X, Ch1X and Ch2X groups, respectively (P<0.05). Moreover, aggregation improved the morphological quality of blastocysts from the Dc2X over the Dc1X group. Gene expression analysis revealed that Ch1X and Ch2X blastocysts had significantly lower relative expression of OCT4, CDX2 and NANOG than the Dc1X, Dc2X and IVF control groups. The OCT4, NANOG, SOX2 and CDX2 genes were overexpressed in Dc1X blastocysts, but the relative expression of these four genes decreased in the Dc2X, reaching similar relative levels to those of Dc IVF blastocysts. In conclusion, Ch blastocysts were produced using Dc oocytes, but with lower relative expression of pluripotent and trophoblastic genes, indicating that nuclear reprogramming could be still incomplete. Despite this, embryo aggregation improved the development of Ch and Dc embryos, and normalized Dc gene expression, which suggests that this strategy could improve full-term developmental efficiency of cat and feline iSCNT embryos.

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.

Molecular characterization and in vitro differentiation of feline progenitor-like amniotic epithelial cells

Introduction

While amniotic mesenchymal cells have been isolated and characterized in different species, amniotic epithelial cells (AECs) have been found only in humans and horses and are recently considered valid candidates in regenerative medicine. The aim of this work is to obtain and characterize, for the first time in the feline species, presumptive stem cells from the epithelial portion of the amnion (AECs) to be used for clinical applications.

Methods

In our study, we molecularly characterized and induced in vitro differentiation of feline AECs, obtained after enzymatic digestion of amnion.

Results

AECs displayed a polygonal morphology and the mean doubling time value was 1.94 ± 0.04 days demonstrating the high proliferating capacity of these cells. By RT-PCR, AECs expressed pluripotent (Oct4, Nanog) and some mesenchymal markers (CD166, CD44) suggesting that an epithelial-mesenchymal transition may occur in these cells that lack the hematopoietic marker CD34. Cells also showed the expression of embryonic marker SSEA-4, but not SSEA-3, as demonstrated by immunocytochemistry and flow cytometry. Moreover, the possibility to use feline AECs in cell therapies resides in their low immunogenicity, due to the absence of MHC-II antigen expression. After induction, AECs differentiated into the mesodermic and ectodermic lineages, demonstrating high plasticity.

Conclusions

In conclusion, feline AECs appear to be a readily obtainable, highly proliferative, multipotent and non-immunogenic cell line from a source that may represent a good model system for stem cell biology and be useful in allogenic cell-based therapies in order to treat tissue lesions, especially with loss of substance.

Scriptaid and 5-aza-2'deoxycytidine enhanced expression of pluripotent genes and in vitro developmental competence in interspecies black-footed cat cloned embryos

Somatic cell nuclear transfer offers the possibility of preserving endangered species including the black-footed cat, which is threatened with extinction. The effectiveness and efficiency of somatic cell nuclear transfer (SCNT) depends on a variety of factors, but 'inappropriate epigenetic reprogramming of the transplanted nucleus is the primary cause of the developmental failure of cloned embryos. Abnormal epigenetic events such as DNA methylation and histone modifications during SCNT perturb the expression of imprinted and pluripotent-related genes that, consequently, may result in foetal and neonatal abnormalities. We have demonstrated that pregnancies can be established after transfer of black-footed cat cloned embryos into domestic cat recipients, but none of the implanted embryos developed to term and the foetal failure has been associated to aberrant reprogramming in cloned embryos. There is growing evidence that modifying the epigenetic pattern of the chromatin template of both donor cells and reconstructed embryos with a combination of inhibitors of histone deacetylases and DNA methyltransferases results in enhanced gene reactivation and improved in vitro and in vivo developmental competence. Epigenetic modifications of the chromatin template of black-footed cat donor cells and reconstructed embryos with epigenetic-modifying compounds enhanced in vitro development, and regulated the expression of pluripotent genes, but these epigenetic modifications did not improve in vivo developmental competence.

Transgenic chicken, mice, cattle, and pig embryos by somatic cell nuclear transfer into pig oocytes

This study explored the possibility of producing transgenic cloned embryos by interspecies somatic cell nuclear transfer (iSCNT) of cattle, mice, and chicken donor cells into enucleated pig oocytes. Enhanced green florescent protein (EGFP)-expressing donor cells were used for the nuclear transfer. Results showed that the occurrence of first cleavage did not differ significantly when pig, cattle, mice, or chicken cells were used as donor nuclei (p>0.05). However, the rate of blastocyst formation was significantly higher in pig (14.9±2.1%; p<0.05) SCNT embryos than in cattle (6.3±2.5%), mice (4.2±1.4%), or chicken (5.1±2.4%) iSCNT embryos. The iSCNT embryos also contained a significantly less number of cells per blastocyst than those of SCNT pig embryos (p<0.05). All (100%) iSCNT embryos expressed the EGFP gene, as evidenced by the green florescence under ultraviolet (UV) illumination. Microinjection of purified mitochondria from cattle somatic cells into pig oocytes did not have any adverse effect on their postfertilization in vitro development and embryo quality (p>0.05). Moreover, NCSU23 medium, which was designed for in vitro culture of pig embryos, was able to support the in vitro development of cattle, mice, and chicken iSCNT embryos up to the blastocyst stage. Taken together, these data suggest that enucleated pig oocytes may be used as a universal cytoplast for production of transgenic cattle, mice, and chicken embryos by iSCNT. Furthermore, xenogenic transfer of mitochondria to the recipient cytoplast may not be the cause for poor embryonic development of cattle-pig iSCNT embryos.

Translating stem cell therapies: the role of companion animals in regenerative medicine

Veterinarians and veterinary medicine have been integral to the development of stem cell therapies. The contributions of large animal experimental models to the development and refinement of modern hematopoietic stem cell transplantation were noted nearly five decades ago. More recent advances in adult stem cell/regenerative cell therapies continue to expand knowledge of the basic biology and clinical applications of stem cells. A relatively liberal legal and ethical regulation of stem cell research in veterinary medicine has facilitated the development and in some instances clinical translation of a variety of cell-based therapies involving hematopoietic stem cells and mesenchymal stem cells, as well as other adult regenerative cells and recently embryonic stem cells and induced pluripotent stem cells. In fact, many of the pioneering developments in these fields of stem cell research have been achieved through collaborations of veterinary and human scientists. This review aims to provide an overview of the contribution of large animal veterinary models in advancing stem cell therapies for both human and clinical veterinary applications. Moreover, in the context of the "One Health Initiative," the role veterinary patients may play in the future evolution of stem cell therapies for both human and animal patients will be explored.

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.

Recombinant rabbit leukemia inhibitory factor and rabbit embryonic fibroblasts support the derivation and maintenance of rabbit embryonic stem cells

The rabbit is a classical experimental animal species. A major limitation in using rabbits for biomedical research is the lack of germ-line-competent rabbit embryonic stem cells (rbESCs). We hypothesized that the use of homologous feeder cells and recombinant rabbit leukemia inhibitory factor (rbLIF) might improve the chance in deriving germ-line-competent rbES cells. In the present study, we established rabbit embryonic fibroblast (REF) feeder layers and synthesized recombinant rbLIF. We derived a total of seven putative rbESC lines, of which two lines (M5 and M23) were from culture Condition I using mouse embryonic fibroblasts (MEFs) as feeders supplemented with human LIF (hLIF) (MEF+hLIF). Another five lines (R4, R9, R15, R21, and R31) were derived from Condition II using REFs as feeder cells supplemented with rbLIF (REF+rbLIF). Similar derivation efficiency was observed between these two conditions (8.7% vs. 10.2%). In a separate experiment with 2×3 factorial design, we examined the effects of feeder cells (MEF vs. REF) and LIFs (mLIF, hLIF vs. rbLIF) on rbESC culture. Both Conditions I and II supported satisfactory rbESC culture, with similar or better population doubling time and colony-forming efficiency than other combinations of feeder cells with LIFs. Rabbit ESCs derived and maintained on both conditions displayed typical ESC characteristics, including ESC pluripotency marker expression (AP, Oct4, Sox2, Nanog, and SSEA4) and gene expression (Oct4, Sox2, Nanog, c-Myc, Klf4, and Dppa5), and the capacity to differentiate into three primary germ layers in vitro. The present work is the first attempt to establish rbESC lines using homologous feeder cells and recombinant rbLIF, by which the rbESCs were derived and maintained normally. These cell lines are unique resources and may facilitate the derivation of germ-line-competent rbESCs.

Gene expression profiling of pluripotency and differentiation-related markers in cat oocytes and preimplantation embryos

During mammalian preimplantation development, two successive differentiation events lead to the establishment of three committed lineages with separate fates: the trophectoderm, the primitive endoderm and the pluripotent epiblast. In the mouse embryo, the molecular mechanisms underlying these two cell fate decisions have been studied extensively, leading to the identification of lineage-specific transcription factors. Species-specific differences in expression patterns of key regulatory genes have been reported, raising questions regarding their role in different species. The aim of the present study was to characterise the gene expression patterns of pluripotency (OCT4, SOX2, NANOG) and differentiation (CDX2, GATA6)-related markers during feline early development using reverse transcription–quantitative polymerase chain reaction. In addition, we assessed the impact of in vitro development on gene expression by comparing transcript levels of the genes investigated between in vitro and in vivo blastocysts. To normalise quantitative data within different preimplantation embryo stages, we first validated a set of stable reference genes. Transcript levels of all genes investigated were present and changed over the course of preimplantation development; a highly significant embryo-stage effect on gene expression was observed. Transcript levels of OCT4 were significantly reduced in in vitro blastocysts compared with their in vivo counterparts. None of the other genes investigated showed altered expression under in vitro conditions. The different gene expression patterns of OCT4, SOX2, CDX2 and GATA6 in cat embryos resembled those described in mouse embryos, indicative of a preserved role for these genes during early segregation. However, because of the absence of any upregulation of NANOG transcription levels after embryonic genome activation, it is unlikely that NANOG is a key regular of lineage segregation. Such results support the hypothesis that the behaviour of early lineage markers can be species specific. The present study also revealed a pool of maternal NANOG mRNA transcripts, the role of which remains to be elucidated. Comparing transcription levels of these genes between in vivo and in vitro blastocysts revealed low levels of OCT4 mRNA in the latter, which may contribute to the reduced developmental competence of embryos under suboptimal conditions.

Inducing pluripotency in somatic cells from the snow leopard (Panthera uncia), an endangered felid

Induced pluripotency is a new approach to produce embryonic stem-like cells from somatic cells that provides a unique means to understand both pluripotency and lineage assignment. To investigate whether this technology could be applied to endangered species, where the limited availability of gametes makes production and research on embryonic stem cells difficult, we attempted generation of induced pluripotent stem (iPS) cells from snow leopard (Panthera uncia) fibroblasts by retroviral transfection with Moloney-based retroviral vectors (pMXs) encoding four factors (OCT4, SOX2, KLF4 and cMYC). This resulted in the formation of small colonies of cells, which could not be maintained beyond four passages (P4). However, addition of NANOG, to the transfection cocktail produced stable iPS cell colonies, which formed as early as D3. Colonies of cells were selected at D5 and expanded in vitro. The resulting cell line was positive for alkaline phosphatase (AP), OCT4, NANOG, and Stage-Specific embryonic Antigen-4 (SSEA-4) at P14. RT-PCR also confirmed that endogenous OCT4 and NANOG were expressed by snow leopard iPS cells from P4. All five human transgenes were transcribed at P4, but OCT4, SOX2 and NANOG transgenes were silenced as early as P14; therefore, reprogramming of the endogenous pluripotent genes had occurred. When injected into immune-deficient mice, snow leopard iPS cells formed teratomas containing tissues representative of the three germ layers. In conclusion, this was apparently the first derivation of iPS cells from the endangered snow leopard and the first report on induced pluripotency in felid species. Addition of NANOG to the reprogramming cocktail was essential for derivation of iPS lines in this felid. The iPS cells provided a unique source of pluripotent cells with utility in conservation through cryopreservation of genetics, as a source of reprogrammed donor cells for nuclear transfer or for directed differentiation to gametes in the future.

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.