Changes in cell density as an early marker for low dose ionising radiation‐ induced cataractogenesis

Epidemiological data correlates exposure to low dose ionising radiation (IR) and cataractogenesis later in life. Our understanding of the underlying biological mechanisms is still in its early stages as we seek to explore the applicability of the linear no‐threshold model in these low dose and low dose rate exposures. A single layer of epithelial cells (LECs) covers the anterior hemisphere of the lens. Central and peripheral regions (PR) are designated on the basis of position and cell density. The PR is considered the most radiosensitive region of the epithelium. To understand how LECs manage IR‐exposure at low dose levels and rates, mice of various genetic backgrounds were exposed to 0.5, 1 and 2 Gy using Co 60 gamma‐rays at dose rates of 0.3 or 0.063 Gy/min. The cell density and cell proliferation of LECs were analysed at specific time points post‐IR. A differential LECs organisational structure and response to IR in the various mice strains was observed in a dose rate and gender dependent manner. Our data indicate that low dose IR‐effects require a relatively long latency period, in line with epidemiological data from longitudinal studies and evidencing the importance of such studies particularly with respect to human health, occupation, environment and unintended exposures. Longitudinal studies are essential to understand IR‐induced cataract. The mechanisms and processes of IR‐induced cataract formation are incomplete at present, but our data call into question the applicability of the linear no‐threshold model at these low dose/dose rate levels.