An Investigation of C.Elegans as a Model Organism for FLASH Research Utilizing TUNL FEL

Abstract

FLASH radiotherapy has demonstrated the potential to spare normal tissue while maintaining tumor control, yet the underlying biological mechanisms remain poorly understood. This thesis investigates Caenorhabditis elegans as a high throughput, genetically tractable model organism for studying FLASH effects using the High Intensity Gamma Source (HIGS) at Triangle University Nuclear Laboratory (TUNL). C. elegans offers several advantages for radiobiological research, including a rapid life cycle, optical transparency, and extensive genetic conservation with humans.A series of experiments (HIGS13–HIGS23) were conducted to identify and refine a reliable biological endpoint. Early evaluations of motility revealed limitations due to beam geometry and plate activation, prompting a shift toward reproductive assays. While HIGS17 initially suggested FLASH associated sparing, subsequent experiments (HIGS18 & 19) failed to reproduce these results, identifying the initial findings as a statistical artifact of low control progeny. HIGS20 & 21 explored the influence of pulse structure, revealing dose dependent variations but no consistent sparing effect in reproduction. To investigate alternative physiological markers, the latest experiments utilized pharyngeal pumping rates as a functional endpoint. Unlike reproductive assays, pharyngeal pumping provided a near real-time assessment of neuromuscular degradation post-irradiation. Results indicated that at 200Gy and 400 Gy prescriptive dose steps FLASH sparing was observed with significantly higher pumping of 94.5% and 86.5%(P<.001) of the unirradiated control as compared to 82.1% and 66.4%(P<.01) for conventionally irradiated c.elegan respectively, offering a different perspective on radiation-induced physiological stress and a differential that with further investigation could be used as a FLASH sparing benchmark. Currently, these results suggest that while reproduction may not be a robust endpoint for FLASH sparing in this model, functional assays like pharyngeal pumping provide a more nuanced understanding of the biological response. This work lays the foundation for future mechanistic studies involving targeted genetic investigations into DNA repair pathways.