In vitro culture period but not the passage number influences the capacity of chimera production of inner cell mass and its deriving cells from porcine embryos

Research progress and application prospects of stable porcine pluripotent stem cells

Pluripotent stem cells (PSCs) harbor the capacity of unlimited self-renewal and multi-lineage differentiation potential which are crucial for basic research and biomedical science. Establishment of PSCs with defined features were previously reported from mice and humans, while generation of stable large animal PSCs has experienced a relatively long trial stage and only recently has made breakthroughs. Pigs are regarded as ideal animal models for their similarities in physiology and anatomy to humans. Generation of porcine PSCs would provide cell resources for basic research, genetic engineering, animal breeding and cultured meat. In this review, we summarize the progress on the derivation of porcine PSCs and reprogrammed cells and elucidate the mechanisms of pluripotency changes during pig embryo development. This will be beneficial for understanding the divergence and conservation between different species involved in embryo development and the pluripotent regulated signaling pathways. Finally, we also discuss the promising future applications of stable porcine PSCs.

Livestock pluripotency is finally captured in vitro

Pluripotent stem cells (PSCs) have demonstrated great utility in improving our understanding of mammalian development and continue to revolutionise regenerative medicine. Thanks to the improved understanding of pluripotency in mice and humans, it has recently become feasible to generate stable livestock PSCs. Although it is unlikely that livestock PSCs will be used for similar applications as their murine and human counterparts, new exciting applications that could greatly advance animal agriculture are being developed, including the use of PSCs for complex genome editing, cellular agriculture, gamete generation and invitro breeding schemes.

Derivation of Porcine Embryonic Stem-Like Cells from In Vitro-Produced Blastocyst-Stage Embryos

Efficient isolation of embryonic stem (ES) cells from pre-implantation porcine embryos has remained a challenge. Here, we describe the derivation of porcine embryonic stem-like cells (pESLCs) by seeding the isolated inner cell mass (ICM) from in vitro-produced porcine blastocyst into α-MEM with basic fibroblast growth factor (bFGF). The pESL cells kept the normal karyotype and displayed flatten clones, similar in phenotype to human embryonic stem cells (hES cells) and rodent epiblast stem cells. These cells exhibited alkaline phosphatase (AP) activity and expressed pluripotency markers such as OCT4, NANOG, SOX2, SSEA-4, TRA-1-60, and TRA-1-81 as determined by both immunofluorescence and RT-PCR. Additionally, these cells formed embryoid body (EB), teratomas and also differentiated into 3 germ layers in vitro and in vivo. Microarray analysis showed the expression of the pluripotency markers, PODXL, REX1, SOX2, KLF5 and NR6A1, was significantly higher compared with porcine embryonic fibroblasts (PEF), but expression of OCT4, TBX3, REX1, LIN28A and DPPA5, was lower compared to the whole blastocysts or ICM of blastocyst. Our results showed that porcine embryonic stem-like cells can be established from in vitro-produced blastocyst-stage embryos, which promote porcine naive ES cells to be established.

Enhancing effects of serum-rich and cytokine-supplemented culture conditions on developing blastocysts and deriving porcine parthenogenetic embryonic stem cells

The present study was conducted to develop an effective method for establishment of porcine parthenogenetic embryonic stem cells (ppESCs) from parthenogenetically activated oocyte-derived blastocysts. The addition of 10% fetal bovine serum (FBS) to the medium on the 3rd day of oocyte culturing improved the development of blastocysts, attachment of inner cell masses (ICMs) onto feeder cells, and formation of primitive ppESC colonies. ICM attachment was further enhanced by basic fibroblast growth factor, stem cell factor, and leukemia inhibitory factor. From these attached ICMs, seven ppESC lines were established. ppESC pluripotency was verified by strong enzymatic alkaline phosphatase activity and the expression of pluripotent markers OCT3/4, Nanog, and SSEA4. Moreover, the ppESCs were induced to form an embryoid body and teratoma. Differentiation into three germ layers (ectoderm, mesoderm, and endoderm) was confirmed by the expression of specific markers for the layers and histological analysis. In conclusion, data from the present study suggested that our modified culture conditions using FBS and cytokines are highly useful for improving the generation of pluripotent ppESCs.

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

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

Pluripotent stem cells and reprogrammed cells in farm animals

Pluripotent cells are unique because of their ability to differentiate into the cell lineages forming the entire organism. True pluripotent stem cells with germ line contribution have been reported for mice and rats. Human pluripotent cells share numerous features of pluripotentiality, but confirmation of their in vivo capacity for germ line contribution is impossible due to ethical and legal restrictions. Progress toward derivation of embryonic stem cells from domestic species has been made, but the derived cells were not able to produce germ line chimeras and thus are termed embryonic stem-like cells. However, domestic animals, in particular the domestic pig (Sus scrofa), are excellent large animals models, in which the clinical potential of stem cell therapies can be studied. Reprogramming technologies for somatic cells, including somatic cell nuclear transfer, cell fusion, in vitro culture in the presence of cell extracts, in vitro conversion of adult unipotent spermatogonial stem cells into germ line derived pluripotent stem cells, and transduction with reprogramming factors have been developed with the goal of obtaining pluripotent, germ line competent stem cells from domestic animals. This review summarizes the present state of the art in the derivation and maintenance of pluripotent stem cells in domestic animals.

Establishment and characterization of novel porcine embryonic stem cell lines expressing hrGFP

The purpose of this study was to establish transgenic porcine embryonic stem (pES) cell lines that can stably express report gene. Established pES cell line at passage 44 was transfected with pAAV-hrGFP Control Plasmid by electroporation-mediated, viral vector-mediated, and liposome-mediated strategies. Although there were several pES colonies expressing green fluorescent protein (GFP) obtained from the retrovirus-mediated and liposome-mediated transfection methods, no stable GFP-expressing pES cell line was then derived. A total of 28 GFP-expressing pES cell colonies were obtained following electroporation with two DC pulses of 150 V/cm for 10 msec and three GFP-expressing pES (pES/GFP(+)) cell lines were established. These pES/GFP(+) cell lines stably expressed exogenous GFP and continuously proliferated in vitro for more than 90 passages in 20 months. They maintained normal karyotype of 36 + XX and typical characteristics of pluripotent stem cells, including expression of pluripotent markers Oct-4, AP, SSEA-4, TRA-1-60, and TRA-1-81, formation of embryoid bodies under suspension culture. They were able to differentiate in vitro into neural and cardiomyocytic lineage, respectively, under suitable induction. To our knowledge, there has been no report of establishing GFP-expressing pES cell lines. These novel pES/GFP(+) cell lines established in this study might serve as a nonrodent model and would benefit to the studies involving ES cell transplantation, cell replacement therapy, and tissue regeneration due to their traceable capacity.

Transcriptional heterogeneity in mouse embryonic stem cells

The embryonic stem (ES) cell is a stem cell derived from early embryos that can indefinitely repeat self-renewing cell division cycles as an undifferentiated cell in vitro and give rise to all specialised cell types in the body. However, manipulating ES cell differentiation in vitro is a challenge due to, at least in part, heterogeneous gene induction. Recent experimental evidence has demonstrated that undifferentiated mouse ES cells maintained in culture exhibit heterogeneous expression of Dppa3, Nanog, Rex1, Pecam1 and Zscan4 as well as genes (Brachyury/T, Rhox6/9 and Twist2) normally expressed in specialised cell types. The Nanog-negative, Rex1-negative or T-positive ES cell subpopulation has a unique differentiation potential. Thus, studying the mechanism that generates ES cell subpopulations will improve manipulation of ES cell fate and help our understanding of the nature of embryonic development.

Passage number affects the pluripotency of mouse embryonic stem cells as judged by tetraploid embryo aggregation

The aim of this study was to determine whether the number of passages affected the developmental pluripotency of embryonic stem (ES) cells as measured by the attainment of adult fertile mice derived from embryonic stem (ES) cell/tetraploid embryo complementation. Thirty-six newborns were produced by the aggregation of tetraploid embryos and hybrid ES cells after various numbers of passages. These newborns were entirely derived from ES cells as judged by microsatellite DNA, coat-color phenotype, and germline transmission. Although 15 survived to adulthood, 17 died of respiratory failure, and four were eaten by their foster mother. From the 15 mice that reached adulthood and that could reproduce, none arose from ES cells at passage level 15 or more. All 15 arose from cells at passages 3-11. Our results demonstrate that the number of passages affects the developmental pluripotency of ES cells.