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Mol. Cells 2011; 31(2): 123-132

Published online January 18, 2011

https://doi.org/10.1007/s10059-011-0016-8

© The Korean Society for Molecular and Cellular Biology

Biochemical and Morphological Effects of Hypoxic Environment on Human Embryonic Stem Cells in Long-Term Culture and Differentiating Embryoid Bodies

Hee-Joung Lim1,2, Jiyou Han1, Dong-Hun Woo1, Sung-Eun Kim1, Suel-Kee Kim1, Hee-Gyoo Kang2,*, and Jong-Hoon Kim1,*

1Laboratory of Stem Cell Biology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Korea, 2Biomedical Laboratory, Department of Biomedical Laboratory Science, College of Health Science, Eulji University, Sungnam 461-713, Korea

Correspondence to : *Correspondence: jhkim@korea.ac.kr (JHK); kanghg@eulji.ac.kr (HGK)

Received: July 2, 2010; Revised: November 6, 2010; Accepted: November 17, 2010

Abstract

The mammalian reproductive tract is known to contain 1.5-5.3% oxygen (O2), but human embryonic stem cells (hESCs) derived from preimplantation embryos are typically cultured under 21% O2 tension. The aim of this study was to investigate the effects of O2 tension on the long-term culture of hESCs and on cell-fate determination during early differentiation. hESCs and embryoid bodies (EBs) were grown under different O2 tensions (3, 12, and 21% O2). The expression of markers associated with pluripotency, embryonic germ layers, and hypoxia was analyzed using RT-PCR, immunostaining, and Western blotting. Proliferation, apoptosis, and chromosomal aberrations were examined using BrdU incorporation, caspase-3 immunostaining, and karyotype analysis, respectively. Structural and morphological changes of EBs under different O2 tensions were comparatively examined using azan- and hematoxylin-eosin staining, and scanning and transmission electron microscopy. Mild hypoxia (12% O2) increased the number of cells expressing Oct4/Nanog and reduced BrdU incorporation and aneuploidy. The percentage of cells positive for active caspase-3, which was high during normoxia (21% O2), gradually decreased when hESCs were continuously cultured under mild hypoxia. EBs subjected to hypoxia (3% O2) exhibited well-differentiated microvilli on their surface, secreted high levels of collagen, and showed enhanced differentiation into primitive endoderm. These changes were associated with increased expression of Foxa2, Sox17, AFP, and GATA4 on the EB periphery. Our data suggest that mild hypoxia facilitates the slow mitotic division of hESCs in long-term culture and reduces the frequency of chromosomal abnormalities and apoptosis. In addition, hypoxia promotes the differentiation of EBs into extraembryonic endoderm.

Keywords differentiation, embryoid body, germ-layer, human embryo stem cell, hypoxia

Article

Research Article

Mol. Cells 2011; 31(2): 123-132

Published online February 28, 2011 https://doi.org/10.1007/s10059-011-0016-8

Copyright © The Korean Society for Molecular and Cellular Biology.

Biochemical and Morphological Effects of Hypoxic Environment on Human Embryonic Stem Cells in Long-Term Culture and Differentiating Embryoid Bodies

Hee-Joung Lim1,2, Jiyou Han1, Dong-Hun Woo1, Sung-Eun Kim1, Suel-Kee Kim1, Hee-Gyoo Kang2,*, and Jong-Hoon Kim1,*

1Laboratory of Stem Cell Biology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Korea, 2Biomedical Laboratory, Department of Biomedical Laboratory Science, College of Health Science, Eulji University, Sungnam 461-713, Korea

Correspondence to:*Correspondence: jhkim@korea.ac.kr (JHK); kanghg@eulji.ac.kr (HGK)

Received: July 2, 2010; Revised: November 6, 2010; Accepted: November 17, 2010

Abstract

The mammalian reproductive tract is known to contain 1.5-5.3% oxygen (O2), but human embryonic stem cells (hESCs) derived from preimplantation embryos are typically cultured under 21% O2 tension. The aim of this study was to investigate the effects of O2 tension on the long-term culture of hESCs and on cell-fate determination during early differentiation. hESCs and embryoid bodies (EBs) were grown under different O2 tensions (3, 12, and 21% O2). The expression of markers associated with pluripotency, embryonic germ layers, and hypoxia was analyzed using RT-PCR, immunostaining, and Western blotting. Proliferation, apoptosis, and chromosomal aberrations were examined using BrdU incorporation, caspase-3 immunostaining, and karyotype analysis, respectively. Structural and morphological changes of EBs under different O2 tensions were comparatively examined using azan- and hematoxylin-eosin staining, and scanning and transmission electron microscopy. Mild hypoxia (12% O2) increased the number of cells expressing Oct4/Nanog and reduced BrdU incorporation and aneuploidy. The percentage of cells positive for active caspase-3, which was high during normoxia (21% O2), gradually decreased when hESCs were continuously cultured under mild hypoxia. EBs subjected to hypoxia (3% O2) exhibited well-differentiated microvilli on their surface, secreted high levels of collagen, and showed enhanced differentiation into primitive endoderm. These changes were associated with increased expression of Foxa2, Sox17, AFP, and GATA4 on the EB periphery. Our data suggest that mild hypoxia facilitates the slow mitotic division of hESCs in long-term culture and reduces the frequency of chromosomal abnormalities and apoptosis. In addition, hypoxia promotes the differentiation of EBs into extraembryonic endoderm.

Keywords: differentiation, embryoid body, germ-layer, human embryo stem cell, hypoxia

Mol. Cells
Mar 31, 2023 Vol.46 No.3, pp. 131~189
COVER PICTURE
The physiologically important cytoprotective signaling in normal cells (background area in turquoise) mediated by NRF2 (blue chain) is often hijacked by cancer cells (red ball) in the tumor microenvironment (yellow area). However, the differential roles of NRF2 throughout the multistage carcinogenesis remains largely unresolved (white-colored overlapping misty areas).

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