Deloch, L.

Durante, M.

Frey, B.

Gaipl, U. S.

Nasonova, E.

Paz, N.

Ritter, S.

GSI Repository

Time course of radiation induced chromosome aberrations in mouse bonemarrow cells∗N. Paz1, E. Nasonova1,3, L. Deloch4, B. Frey4, US. Gaipl4, M. Durante1,2, and S. Ritter11GSI, Darmstadt, Germany; 2TU, Darmstadt, Germany; 3JINR, Dubna, Russia; 4Universita¨tsklinikum Erlangen,GermanyThe analysis of chromosome aberrations (CA) in cellsat the first post-irradiation mitosis is an established tech-nique to estimate the absorbed dose and to assess the ra-diation risk. Within the GREWIS consortium we will usethis method to examine the effects of either α-particles, Fe-ions or X-rays on murine bone marrow cells (BMC). SinceBMC are an asynchronously growing cell population andthe number and the types of primary aberrations depend onthe cell cycle stage at exposure, CA have to be scored atmultiple fixation times to obtain a reliable estimate of thedamage produced within the initial cell population.In preparatory experiments BMC were isolated fromC57BL/6 wild type mice as described elsewhere [1] andcultured for 2 hours in medium containing EdU (0,1 μM)and colcemid (0,025 μg/ml). After 2 hours chromosomespreads were prepared. Analysis of the sample showed that26% of the interphase cells incorporated EdU, i.e. are inS-phase; the mitotic index was 3%. Interestingly, one thirdof the metaphases was EdU-positive pointing to a subpop-ulation of BMC with a short G2-phase (< 2h) (Fig. 1).Figure 1: Chromosome spreads of BMC labelled for 2hwith EdU. The labelling pattern shows that cells in late(left) or middle S-phase (right) reach mitosis within thistime interval.Subsequently, BMC were exposed ex vivo to 1 Gy X-rays (135kV, and 33,7mA). For chromosome analysis cellswere harvested between 4h and 24h post-irradiation tocover the first post-irradiation cell cycle and stained withGiemsa. At 4h after exposure the mitotic index of BMCwas too low for aberration scoring (<0.5%) indicating thatradiation delays the progression of cells to mitosis. At thelater times the mitotic index recovered and 100 metaphaseswere analysed per time-point. As shown in Fig. 2A alow yield of CA was found at 8h after exposure. Thenumber of CA increased with time and reached a maxi-∗Work supported by BMBF, grant 02NUK017A and 02NUK017G.mum between 16 and 20h. The aberration yield declinedat 24h due to the dilution with undamaged or less damagedcells in second cycle metaphases (Fig. 2A). Chromatid-type aberrations dominated the aberration spectrum up to20h post-exposure, while at 24h mainly chromosome-typeaberrations were found (Fig. 2B). Altogether, the specificchanges in the time-course of CA and the aberration spec-trum demonstrate that most BMC reach the first mitosisafter an exposure to 1 Gy X-rays within 24h. In subsequentstudies we will examine, whether a later time-point is nec-essary for studies applying higher doses.60801001201401604 8 12 16 20 24Time1Gy X rays02550751001258 12 16 20 24TimeChromatid ChromosomeA BAberrations /100 cellsAberration types (%)Figure 2: Aberration yield (A) and percentage ofchromatid- and chromosome-type aberrations (B) mea-sured in murine BMC at multiple harvesting times afterexposure to 1Gy X-rays.Recently we extended these studies to a human TNF-alpha transgenic mouse model [2]. The animals developspontaneously arthritis and will be used within the consor-tium to study the health effects of radon in comparison toX-rays. As described above, BMC were isolated, exposedex vivo to X-rays and CA were measured at several sam-pling times. The time course of CA in BMC of TNF-alphamice was similar to that of wild type mice, with a maxi-mum between 16 and 20h. Yet, the aberration yields wereslightly higher in BMC from TNF-alpha mice. Currently,the experiments are repeated and mFISH analysis is per-formed to consolidate these results.References[1] N. Paz et al, GSI Scientific Report 2012 (2013)[2] B. Frey et al, Autoimmunity, 42(4), May 2009, p. 346-8.BIOPHYSICS-22 GSI SCIENTIFIC REPORT 2013224 doi:10.15120/GR-2014-1-BIOPHYSICS-22

Time course of radiation induced chromosome aberrations in mouse bone marrow cells

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Time course of radiation induced chromosome aberrations in mouse bone marrow cells

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