Download differentiation of human embryonic stem cells * a perfect

DIFFERENTIATION OF HUMAN EMBRYONIC STEM CELLS – A
PERFECT MODEL FOR THE RISK ASSESSMENT OF IONIZING
RADIATION DURING EARLY EMBRYO DEVELOPMENT
I. Schroeder1/2, S. Luft1, D. Oelschlaegel2/3, Ireen Kulish1, P. Hessel1, M. Durante1,4,
S. Ritter1
1
GSI, Darmstadt, Germany, 2Translational Center for Regenerative Medicine (TRM)
Leipzig, 3Martin Luther University (MLU) Halle-Wittenberg, 4Technical University
Darmstadt, Germany
[email protected]
The use of diagnostic and/or therapeutic procedures based on ionizing radiation
steadily increases. However, these procedures as well as the exposure to
environmental radiation pose a threat to the early embryo possibly leading to prenatal
death, growth retardation, organ malformation, mental retardation or childhood cancer
[1]. Thus, a thorough risk assessment of radiation effects is mandatory in situations of
inevitable or unintended exposure of the conceptus in utero. We hypothesize that
human embryonic stem (hES) cells, derived from the inner cell mass of the blastocyst
during embryo development, present a valuable tool to examine the radiation effects
on the early embryo and their underlying mechanisms. As these cells can differentiate
into all cells of the body within the three germ layers endoderm, ectoderm and
mesoderm, we were specifically interested in the ability of hES to form definitive
endoderm (DE), which will subsequently give rise to organs such as liver, lung and
pancreas, after exposure to X-ray irradiation. First, chromosomal aberrations were
analyzed using the multicolor fluorescence in situ hybridization (mFISH) technique to
determine the cytogenetic status of exposed and unexposed hES cells. Subsequently,
these cells were subjected to a differentiation protocol based on previous studies of
D’Amour et al. [2]. DE formation was initiated by treatment with Activin A and
Wnt3a under serum-free conditions leading to Foxa2high/Sox17high/Sdf1low progenitors
as assessed by quantitative PCR and immunocytochemistry. MicroRNA (miRNA)
analyses revealed that miR-375 plays a crucial role in DE formation and is highly
expressed concomitant to Sox17. Inhibition of this miRNA resulted in decreased
Foxa2 expression and DE formation. X-ray irradiation of hES cells 3-5 days prior to
differentiation initiation led to massive cells death. Preliminary data suggest that
surviving hES cells undergoing DE differentiation show a delayed expression of
Sox17. Currently, the effect of carbon ions on the differentiation potential of hES
cells is examined. We conclude, that hES cells surviving the radiation exposure
maintain their differentiation capacity albeit with lower efficiency than unexposed
cells possibly explaining the retardations mentioned above.
Supported by the German Ministry of Education and Research, Germany (grant No.
02NUK025A)
[1] McCollough CH et al., RadioGraphics 27: 909-918 (2007)
[2] D’Amour KA et al., Nature Biotech 24: 1392-1401 (2006)