The influence of fractionated radiation on proliferation, cell cycle and apoptosis of normal human dermal fibroblasts

The aim of the study was to investigate the changes in proliferation rate, cell cycle and apoptosis of normal skin fibroblasts during fractionated irradiation with a fraction dose of 2 Gy. Fibroblasts were irradiated 5 days per week for 12 days using gamma irradiation. Twenty four hours after each fraction, and for three days after finishing experiment the cells were harvested, fixed, and BrdUrd labelling index (BrdUrdLI), cell cycle and level of apoptosis and debris were assessed. It was found that fractionated irradiation caused disturbances in the proliferation rate and the cell cycle. Irradiation caused also constant, statistically significant increase in the number of G2M cells and level of apoptosis and debris, which was observed even during 3 days after irradiation. Data indicate non equal biological effect of each fraction dose. Block at G2/M phase suggests accumulation of sublethal damage and increased radiosensitivity, which was manifested by elevated level of cell death (apoptosis and debris).