P-473 Low radiation affects follicle count in sheep ovaries

Abstract

Abstract Study question What is the effect of low dose radiation on follicle count in sheep ovaries? Summary answer Even low dose radiation has a negative impact on the follicle count in sheep ovaries. What is known already Radiotherapy is a corner stone of state-of-the-art cancer treatment, especially in young cancer patients. Survival rates are constantly rising, resulting in long-term survivors with potential child wish. High doses of radiation lead to a permanent damage to the ovaries. Little is known about the damage after low dose radiation to the ovaries including both follicles and stroma. Study design, size, duration Prospective ongoing study, including n = 41 sheeps and 942 ovarian punches (Ø 3mm). So far, n = 12 sheep and n = 120 punches were analysed between April 2020 and January 2022. After finishing the experiments with sheep ovarian tissue, we will continue with a mouse model and human ovarian tissue. Participants/materials, setting, methods 942 cortex punches out of a total of n = 41 sheep were obtained and cryopreserved. After thawing the punches were radiated with a dose of 0.0, 0.5, or 9.0 Gy using a cesium 137 radionuklide source (GSR C1, GammaService Medical GmbH). The punches were fixed in formalin, embedded in paraffin, cut into serial sections of 3-5 µm and stained with Hematoxylin and Eosin for follicle counting as well as Caspase 3 and Ki67. Main results and the role of chance Follicle loss was already observed after low dose radiation (0.5 Gy). Mean follicle count after 0 Gy, 0.5 Gy, and 9 Gy were 7.5, 2.3 and 1.8, respectively. While after 0 Gy, no signs of degeneration were visible, after radiation with 9 Gy follicles showed strong signs of degeneration including disorganization of granulosa cells, pyknosis and stromal irregularities. Limitations, reasons for caution Limitations of our study include the pilot character and therefore small sample size. The presented data only display part of the overall project including also an in-vivo mouse model. Wider implications of the findings As even low dose radiation seems to damage ovarian follicles, further in-vivo studies are needed to confirm these results. Moreover, fertility preservation methods need to be offered consequently to young cancer patients receiving radiotherapy. Trial registration number 25