As a preclinical study, many researchers have been attempted to convert the porcine PSCs into several differentiated cells with transplantation of the differentiated cells into the pigs. Here, we attempted to derive neuronal progenitor cells from pig embryonic germ cells (EGCs). As a result, neuronal progenitor cells could be derived directly from pig embryonic germ cells through the serum-free floating culture of EB-like aggregates (SFEB) method. Treating retinoic acid was more efficient for inducing neuronal lineages from EGCs rather than inhibiting SMAD signaling. The differentiated cells expressed neuronal markers such as PAX6, NESTIN, and SOX1 as determined by qRT-PCR and immunostaining. These data indicated that pig EGCs could provide valid models for human therapy. Finally, it is suggested that developing transgenic pig for disease models as well as differentiation methods will provide basic preclinical data for human regenerative medicine and lead to the success of stem cell therapy.

Because of the physiological and immunological similarities between pigs and humans, porcine embryonic stem cells (ESCs) have been identified as important candidates in preliminary studies on human disease. A comparative understanding of pig ESCs with the human is required to achieve these goals. To gain insights into pig stem cells, the transcriptome of pig ES-like cells were compared with pig preimplantation embryos and human/mouse pluripotent stem cells by RNA-seq analysis. As a result, pig stem cells were more similar to late epiblasts of pig preimplantation embryos than early ICM as revealed by transcriptome analysis, suggesting that pig stem cells are in a developmentally primed state. Moreover, the physiological and biological functions of pig ESCs were more similar to those of human PSCs than to those of mouse PSCs, as determined by direct differentiation and GO/KEGG term analysis. Overall, our data indicate that pig ESCs are in a primed pluripotent state resembling human PSCs. Our findings will facilitate both the development of large animal models for human stem cell therapy and the generation of pluripotent stem cells from other domestic animals for agricultural use. This work was supported by the Korea Institute of Planning and Evaluation for Technology in food, agriculture, forestry, and fisheries (IPET) through the Development of High Value-Added Food Technology Program funded by the Ministry of Agriculture, Food, and Rural Affairs (MAFRA; 118042-03-1-HD020), and partially supported by the grants from the Agenda Program of Rural Development Administration, Republic of Korea (No. PJ01362402)

The transcription factor POU5F1, also known as OCT4 plays critical roles in maintaining pluripotency during early mammalian embryonic development and in embryonic stem cells. It is important to establish an OCT4 promoter region-based reporter system to study pluripotency. However, there is still a lack of information about the porcine OCT4 upstream region. To improve our understanding of the porcine OCT4 regulatory region, we identified conserved regions in the porcine OCT4 promoter upstream region by sequence-based comparative analysis using various mammalian genome sequences. The similarity of nucleotide sequences in the 5' upstream region was low among mammalian species. However, the OCT4 promoter and four regulatory regions, including distal and proximal enhancer elements, had high similarity. The putative transcription factor binding sites in the Oct4 5' upstream region nucleotide sequences from mice and pigs also differed. Some of these genes are related to pluripotency, and further research will allow us to better understand the differences in species-specific pluripotency. Next, a functional analysis of the porcine OCT4 promoter region was conducted. Luciferase reporter assay results indicated that the porcine OCT4 distal enhancer and proximal enhancer were highly activated in mouse embryonic stem cells and embryonic carcinoma cells, respectively. Similar to OCT4 upstream-based reporter systems derived from other species, the porcine OCT4 upstream region-based reporter constructs showed exclusive expression patterns depending on the state of pluripotency. This work provides basic information about the porcine OCT4 upstream region and various porcine OCT4 fluorescence reporter constructs, which can be applied to study species-specific pluripotency in early embryo development and the establishment of embryonic stem cells in pigs. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (NRF-2017R1D1A1B03032256).

Pig embryonic stem cells (ESC) has been suggested to become important animal model for therapeutic cloning using embryonic stem cells derived by somatic cell nuclear transfer (SCNT). However, the quality of cloned embryo and derivation rate of cloned blastocyst has been presented limits for derivation of cloned embryonic stem cell. In this study, we have tried to overcome these problems by aggregating porcine embryos. Zonafree reconstructed SCNT Embryos were cultured in micro-wells singularly (non-aggregated group) or as aggregates of three (aggregated groups) at the four cell stage. Embryo quality of the cloned embryos and attachment on feeder layer rate significantly increased in the aggregates. The aggregation of pig SCNT embryos at the four-cell stage can be a useful technique for improving the quality of pig cloned blastocyst and improvement in the percentage of attachment on the feeder layer of cloned embryos. * This work was supported by the BioGreen 21 Program (PJ0081382011), Rural Development Administration, Republic of Korea.

The four transcription factors Oct4, Sox2, Klf4 and c-Myc have been used for making induced pluripotent stem cells. Many efforts have focused on reducing the number of transcription factors, especially c-Myc and Klf4 known as oncogene, for making induced pluripotent stem cells. Recently it have been demonstrated that Oct4 and Sox2 are able to reprogram human fibroblasts or cord blood cells to induced pluripotent stem cells and Oct4 has the ability to reprogram mouse and human neural stem cell to induced pluripotent stem cells. These researches imply cell types for reprogramming experiments have great influence on selection of reprogramming factors. Here we report that pig kidney cortex fibroblasts need only c-Myc factor when they are used for making induced pluripotent stem cells. We used two vector system including drug-inducible vector system and constitutive expression vector system. The two systems generate induced pluripotent stem cells from pig kidney fibroblasts successfully. These one-factor induced pluripotent stem cells are not only similar but also different to pig embryonic stem-like cells. These two one-factor induced pluripotent stem cell lines can express pluripotency related genes and be differentiated into all three germ layers in vitro. However, these two cell lines can be sub-cultured as a single cell by trypsin. Our results support that single factor, c-Myc, is sufficient to converting pig kidney cortex fibroblasts into induced pluripotent stem cells.

Aromatase is an enzyme that converts testosterone to estrogen. This enzyme, present in the sperm as well as various tissue and cells, has been considered to be related to the fertility of human and mouse sperm. Therefore, we examined effect of aromatase inhibitor on viability and fertility of sperm, and quantity of aromatase in sperm groups with different density in pig. To analyze the effect of aromatase on sperm viability, we treated aromatase inhibitor to the sperm with different concentrations (0, 10, 20, 50, 100, 200, 500 μM) at different time (0.5, 1, 2, 4, 8 hours). After the treatment, the sperm viability was calculated by hypo-osmotic swelling test. We selected 0, 50, 100 μM concentration during 0.5 hour as inhibitor treatment condition before in vitro fertilization. Next, we examined fertility and quantified aromatase protein in sperms with different density. In the first experiment, viability of sperm was decreased following the increasement of inhibitor concentration. The aromatase inhibited sperm showed lower penetration rate and cleavage rate than those of non-treated sperm. Concentration of 50 μM inhibitor had no significant effect on the sperm viability, but it significantly reduced sperm fertility. Second, sperms with low density showed higher penetration rate, but no significant difference between sperms with high density. In conclusion, aromatase is responsible for viability and fertility of porcine sperm similar to mouse and human, however, density of sperm has no correlation with quantity of aromatase protein.

Pluripotent cells are categorized as either "naive" or "primed" based upon their pluripotent status. According to previous studies, embryonic stem cells and embryonic germ cells are identified as naive pluripotent stem cells and epiblast stem cells are identified as primed pluripotent stem cells. In a permissive species such as the mouse, naive and primed pluripotent stem cells can be derived from embryos without genetic manipulations. In non-permissive species such as humans and pigs, primed pluripotent cells are only established from embryos. However, previous studies have shown that the embryonic germ cells of non-permissive species share similar morphology and features with naive pluripotent cells. For these reasons porcine embryonic germ cells (pEGCs) may provide a useful cell source for comparative studies on naive pluripotent cells in non-permissive species. In this study, we attempted to establish and characterize porcine embryonic germ cells. Consequently, an embryonic germ cell line was derived from the genital ridges of a porcine dpc 30 fetus in media containing LIF and bFGF. After establishment, this cells were cultured and stabilized in LIF or bFGF contained media. This cell lines displayed a dome-shaped colony morphology in both culture condition. The cell lines were maintained in both condition over an extended time period and were able to differentiate into the three germ layers in vitro. Interestingly, cell lines cultured in LIF or bFGF expressed different pluripotency markers. LIF-dependent pEGCs expressed naive-pluripotency markers such as OCT4, SOX2, NANOG and SSEA1, while bFGF-dependent pEGCs expressed primed-pluripotency markers such as OCT4, SOX2, NANOG and SSEA4. However, as a result of analysis of XCI, two cell lines showed hemi-methylated pattern similarly in XIST promoter regions. In conclusion, we were able to successfully derive embryonic germ cells from genital ridges of a porcine fetus. Pluripotent state of pEGCs were regulated by modulation of culture condition. In LIF supplement, pEGCs showed naive-pluripotency expressing SSEA1, while pEGCs show primed-pluripotency expressing SSEA4 in bFGF condition. This cell line could potentially be used as naive pluripotent cell source for comparative study with porcine embryonic stem cells and other pluripotent cell lines. As porcine pluripotent cells, pEGCs could be useful candidates for preliminary studies of human disease as well as a source for generating transgenic animals.