Author: Barry Andricks, Stratton Black, Scott R. Floyd, Ashutosh Kotwal, Eric L. Martin, Stepan Mikhailov, Mark Oldham, Niccolo Terrando, Andrew Thompson, Ying Wu 👨🔬
Affiliation: Department of Physics, Duke University, Medical Physics Graduate Program, Duke University, Duke University, Department of Radiation Oncology, Duke University Medical Center, Triangle Universities Nuclear Laboratory 🌍
Purpose: To evaluate and quantify the effects of high energy electron radiation delivered at FLASH and conventional dose rates on the reproductive capability of adult C. elegans nematodes.
Methods: Adult C. elegans were treated in 4 arms with total doses of 60 and 180 Gy for FLASH and conventional dose rates (75 Gy/s and 0.1 Gy/s respectively). Unirradiated groups provided controls. Each FLASH arm contained 30-40 elegans, and each conventional arm contained 19-24 elegans on nutrient infused agarose. FLASH irradiations were performed with a 35 MeV electron beam from the electron injector component of the High Intensity Gamma Source (HIGS) LINAC at Triangle Universities Nuclear Laboratory. The conventional irradiations were performed with a Varian 2100 LINAC with a 20 MeV electron beam. Each well was evaluated 48-hours post-irradiation (adequate for reproductive cycle) and the number of progeny elegans was determined. Reproductive capability was defined as the number of progenies per adult.
Results: Reproductive capability decreased in all irradiated elegans, but markedly less so in FLASH TX arms. Compared to unirradiated controls, the number of progeny per adult in the conventional dose rate arms was 57±13% (95% CI) and 5.4±2.5% (95% CI) for the 60Gy and 180Gy arms respectively. In the FLASH arms the number of progeny per adult was 99±30% (95% CI) and 27±12% (95% CI) for the 60 and 180Gy arms respectively. Flash sparing at 60Gy and 180Gy was therefore estimated as 42±31% (p=0.072) and 22±12% (p=0.031) respectively.
Conclusion: Adult C. elegans reproductive capacity proved a promising model and assay for radio-biological FLASH mechanistic research. Significant sparing of reproductive capability was observed for FLASH dose-rates above 60Gy.