Gamma-H2AX AS A BIOMARKER OF DNA DAMAGE INDUCED BY IONIZING RADIATION IN HUMAN PERIPHERAL BLOOD LYMPHOCYTES AND ARTIFICIAL SKIN.

This study by researchers at the National Cancer Institute (USA) demonstrated that MatTek’s EpiDermFT full-thickness in vitro 3-D human skin tissue equivalent is an excellent tissue model for performing experiments that measure the DNA damage caused by exposure to ionizing radiation because the tissue is derived from normal (non-transformed) human keratinocyes and fibroblasts. Ionizing radiation (IR) exposure is inevitable in our modern society and can lead to a variety of deleterious effects including cancer and birth defects. A reliable, reproducible and sensitive assessment of exposure to ionizing radiation and the individual response to that exposure would provide much needed information for the optimal treatment of each donor examined. We have developed a diagnostic test for ionizing radiation exposure based on detection of the phosphorylated form of variant histone H2AX (gamma-H2AX), which occurs specifically at sites of DNA double-strand breaks (DSBs). The cell responds to a nascent double-strand break through the phosphorylation of thousands of H2AX molecules flanking the damaged site. This highly amplified response can be visualized as a gamma-H2AX focus in the chromatin that can be detected in situ with the appropriate antibody. Here we assess the usability of gamma-H2AX focus formation as a possible biodosimeter for human exposure to IR using pe-ripheral blood lymphocytes irradiated ex vivo and three-dimensional artificial models of human skin biopsies. In both systems, the tissues were exposed to 0.2–5 Gy, doses of ionizing radiation that might be realistically encountered in various scenarios such as cancer radiotherapies or accidental exposure to radiation. Since the gamma-H2AX response is maximal 30 min after exposure and declines over a period of hours as the cells repair the damage, we examined the time limitations of the useful detectability of gamma-H2AX foci. We report that a linear response proportional to the initial radiation dose was obtained 48 and 24 h after exposure in blood samples and skin cells respectively. Thus, detection of gamma-H2AX formation to monitor DNA damage in minimally invasive blood and skin tests could be useful tools to determine radiation dose exposure and analyze its effects on humans.

DNA damage, DNA double strand breaks, EpiDerm-FT, EpiDermFT, Gamma radiation, Gamma-H2AX, Histone, Ionizing radiation

Gamma irradiation (0.2-5 Gy), Ionizing radiation