Publications by authors named "Sang-Ki Baek"

5 Publications

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Serial blood sampling effects in rat embryo-fetal development studies for toxicokinetics.

Regul Toxicol Pharmacol 2021 Apr 20;123:104930. Epub 2021 Apr 20.

Developmental and Reproductive Toxicology Research Group, Korea Institute of Toxicology, Daejeon, Republic of Korea. Electronic address:

Serial blood sampling for toxicokinetics is generally conducted in regulatory embryo-fetal development (EFD) studies in rats. EFD studies are designed to detect the potential adverse effects of pharmaceuticals on pregnant females and their fetuses; this information is useful for understanding the relationships between systemic exposure levels and toxicity profiles. However, additional satellite pregnant females are needed for toxicokinetics because comprehensive information regarding the potential impact of serial blood sampling on pregnant females is scarce. Here, in this study, we investigated the potential impact of serial blood sampling in pregnant female rats using a typical EFD study design. Additionally, we investigated the additional endpoints (clinical pathology, organ weights, and histopathology) that were deemed likely to be sensitive to blood sampling. Results indicated that serial blood sampling in pregnant females induced physiological adaptive changes and did not affect the general endpoints in EFD studies. Nevertheless, inclusion of satellite groups in EFD studies may be a more prudent approach considering the physiological changes in pregnant females and potential off-target effects of candidate pharmaceuticals. These results provide background information on the impact of serial blood sampling in pregnant females and will be useful to design the regulatory EFD studies.
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http://dx.doi.org/10.1016/j.yrtph.2021.104930DOI Listing
April 2021

Endothelial Cells Differentiated from Porcine Epiblast Stem Cells.

Cell Reprogram 2021 Apr;23(2):89-98

Division of Life Science, College of Natural Sciences, Gyeongsang National University, Jinju, Republic of Korea.

Pluripotent stem cells (PSCs) have the ability of self-renewal that can retain the characteristics of the mother cell, and of pluripotency that can differentiate into several body types. PSCs typically include embryonic stem cells (ESCs) derived from the inner cell mass of the preimplantation embryo, and epiblast stem cells (EpiSCs) derived from the epiblast of postimplantation embryo. Although PSCs are able to be used by differentiation into endothelial cells as a potential treatment for vascular diseases, human ESCs and induced PSCs (iPSCs) are followed by ethical and safety issues. Pigs are anatomically and physiologically similar to humans. Therefore, the goal of this study was to establish an efficient protocol that differentiates porcine EpiSCs (pEpiSCs) into the endothelial cells for applying the treatment of human vascular diseases. As a result, alkaline phosphatase (AP)-negative (-) pEpiSCs cultured in endothelial cell growth basal medium-2 (EBM-2) differentiation medium in association with 50 ng/mL of vascular endothelial growth factor (VEGF) for 8 days were changed morphologically like the feature of endothelial cells, and expression of pluripotency-associated markers (OCT-3/4, NANOG, SOX2, and C-MYC) in porcine differentiated cells was significantly decreased ( < 0.05). Additionally, when pEpiSCs were cultured in EBM-2 + 50 ng/mL of VEGF, porcine differentiated cells represented a common endothelial cell marker positive (CD31+) but monocytes and lymphocytes marker negative (CD45-). Therefore, these results indicated that pEpiSCs cultured in EBM-2 + 50 ng/mL of VEGF culture condition were efficiently differentiated into endothelial cells for the treatment of blood vessel diseases.
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http://dx.doi.org/10.1089/cell.2020.0088DOI Listing
April 2021

A Rho-Associated Coiled-Coil Containing Kinase Inhibitor, Y-27632, Improves Viability of Dissociated Single Cells, Efficiency of Colony Formation, and Cryopreservation in Porcine Pluripotent Stem Cells.

Cell Reprogram 2019 02 8;21(1):37-50. Epub 2019 Jan 8.

1 Department of Animal Bioscience, College of Agriculture and Life Sciences, Gyeongsang National University, Jinju, Republic of Korea.

The establishment of porcine epiblast stem cells (pEpiSCs) and induced pluripotent stem cells (piPSCs) derived from diametrical derivations is of great importance in developing biomedical models. However, pEpiSCs and piPSCs have been technically much harder to culture than mouse embryonic stem cells, showing problematic properties such as spontaneous differentiation and apoptosis after cryopreservation. Therefore, we demonstrated that Y-27632 as a Rho-associated coiled-coil containing kinase inhibitor could prevent dissociated pEpiSCs and piPSCs from undesirable differentiation and apoptosis in cryopreservation protocols. pEpiSC 2, 8 lines, Sendai virus-induced pluripotent stem cells (Sev-iPSCs), and lentivirus-induced pluripotent stem cells were cultured with 10 μM Y-27632 before collecting dissociated cells retrieved from colonies using various enzymes. Dissociated single cells were transferred into freezing mediums (open pulled straw vitrification, STEM-CELLBANKER (SCB), 10% dimethylsulfoxide in serum) for cryopreservation. The rates of viability and colony formation obtained from dissociated porcine stem cells after freezing/thawing were examined in the presence of Y-27632. The characteristics of pluripotency and in vitro differentiation were also examined in these stem cells treated with Y-27632 after cryopreservation. As a result, the viability and efficiency of colony formation of dissociated pEpiSCs (2, 8 lines) and Sev-iPSCs treated with 10 μM Y-27632 using the SCB cryopreservation protocol were significantly increased when compared with those of nontreated Y-27632 (p < 0.05). Pluripotency genes (OCT-3/4, NANOG, and SOX2) were positively expressed in Y-27632-treated porcine pluripotent stem cells. Also, in vitro differentiation of these stem cells was successfully induced in the presence of 10 μM Y-27632. These results indicated that treatment of Y-27632 for single-cell dissociation and the SCB cryopreservation protocol could facilitate handling porcine pluripotent stem cells and provide the widespread use of these stem cells.
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http://dx.doi.org/10.1089/cell.2018.0020DOI Listing
February 2019

Activation-Induced Cytidine Deaminase Induces DNA Demethylation of Pluripotency Genes in Bovine Differentiated Cells.

Cell Reprogram 2016 10 19;18(5):298-308. Epub 2016 Aug 19.

1 Department of Animal Bioscience, College of Agriculture and Life Sciences, Gyeongsang National University , Jinju, Republic of Korea.

Activation-induced cytidine deaminase (AID) is the only enzyme that has been suggested as a putative DNA demethylase in mammals. However, very little is known about AID function as DNA demethylase of bovine differentiated cells toward pluripotent state. To investigate the effect of AID on DNA demethylation, bovine AID complementary DNAs were transfected into bovine differentiated cells, which were mostly methylated in the promoter regions of pluripotency genes. As a result, AID-transfected bovine cells started to transform into colonies at day 19 of transfection. The colonies derived from the transfected cells showed positive alkaline phosphatase (AP) staining and expression of pluripotency genes (OCT-3/4, NANOG, SOX2) and pluripotency-related antigens (SSEA-4, TRA1-60, TRA1-81), which have been widely used to characterize human embryonic stem cells. In particular, the levels of OCT-3/4 and NANOG expression were significantly increased in the AID-transfected cells when compared with the control and empty vector-transfected cells (p < 0.05). Finally, DNA demethylation in the promoter regions of pluripotency genes (OCT-3/4, NANOG) was significantly increased compared with the control (p < 0.05). These results demonstrate that the induction of the AID gene into bovine differentiated cells improves DNA demethylation and expression of pluripotency genes.
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http://dx.doi.org/10.1089/cell.2015.0076DOI Listing
October 2016

Siberian Sturgeon Oocyte Extract Induces Epigenetic Modifications of Porcine Somatic Cells and Improves Developmental Competence of SCNT Embryos.

Asian-Australas J Anim Sci 2014 Feb;27(2):266-77

Department of Animal Bioscience, College of Agriculture and Life Sciences, Gyeongsang National University, Jinju, 660-701, Korea.

Somatic cell nuclear transfer (SCNT) has generally demonstrated that a differentiated cell can convert into a undifferentiated or pluripotent state. In the SCNT experiment, nuclear reprogramming is induced by exposure of introduced donor nuclei to the recipient cytoplasm of matured oocytes. However, because the efficiency of SCNT still remains low, a combination of SCNT technique with the ex-ovo method may improve the normal development of SCNT embryos. Here we hypothesized that treatment of somatic cells with extracts prepared from the germinal vesicle (GV) stage Siberian sturgeon oocytes prior to their use as nuclear donor for SCNT would improve in vitro development. A reversible permeability protocol with 4 μg/mL of digitonin for 2 min at 4°C in order to deliver Siberian sturgeon oocyte extract (SOE) to porcine fetal fibroblasts (PFFs) was carried out. As results, the intensity of H3K9ac staining in PFFs following treatment of SOE for 7 h at 18°C was significantly increased but the intensity of H3K9me3 staining in PFFs was significantly decreased as compared with the control (p<0.05). Additionally, the level of histone acetylation in SCNT embryos at the zygote stage was significantly increased when reconstructed using SOE-treated cells (p<0.05), similar to that of IVF embryos at the zygote stage. The number of apoptotic cells was significantly decreased and pluripotency markers (Nanog, Oct4 and Sox2) were highly expressed in the blastocyst stage of SCNT embryos reconstructed using SOE-treated cells as nuclear donor (p<0.05). And there was observed a better development to the blastocyst stage in the SOE-treated group (p<0.05). Our results suggested that pre-treatment of cells with SOE could improve epigenetic reprogramming and the quality of porcine SCNT embryos.
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http://dx.doi.org/10.5713/ajas.2013.13699DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4093206PMC
February 2014