Chromosome length ratio as a biomarker of DNA damage in cells exposed to high dose ionizing radiation

Abstract

The premature chromosome condensation (PCC) assay is considered as complementary bio-dosimetry tool for chromosome aberration assay and the PCC assay can be used to estimate high dose exposure. Though the PCC ring is considered as prospective biomarker, chromosome length ratio (ratio of longest and shortest chromosome length in PCC spreads) of chemically induced PCC is shown to be very good indicator of ionizing radiation. In view of this, an in-vitro study has been performed using PCC assay to suggest chromosome length ratio (LR) as potential bio-dosimeter induced by high dose ionizing radiation. Blood samples were collected from healthy subjects (n=3) after prior consent and irradiated to ten different doses ranging between 0 and 20Gy using 6MV LINAC X-rays with dose rate of 5.6Gy/min. Irradiated lymphocytes were cultured and calyculin induced PCC spreads were prepared. PCC spreads were captured using image analysis system and chromosome lengths were measured using open-source ImageJ software. For each dose, LR for 50 chromosome spreads were computed and mean LR value was calculated. LR varies between 6.0±0.08 and23.6±0.55 for the dose range between 2 and 20Gy. The dose response curve for LR was observed to be linear with y=1.02x+3.36, R2 =0.97. Linear dose response relationship obtained in the present study confirms the prospective use of LR measurement. This study is first of its kind to examine chromosome length ratio as a biomarker of DNA damage in cells exposed to high dose X-ray exposure.