P-409 Effects of low-dose radiation on ovarian immune cells in a mouse model

Abstract Study question How do immune cells in the mouse ovary react after low dose radiation? Summary answer Already shortly after low dose radiation, immune cells are activated in the mouse ovary, dropping to normal levels within short time. What is known already Gonadotoxic treatment in female cancer patients can lead to reversible or permanent fertility impairment. Maintaining gonadal function and preserving fertility after successful cancer treatment have become critical concerns for young fertile patients. Radiation is a cornerstone in cancer treatment. The risk of damage depends on the dose and the site of radiation. There are a few studies (A small number of studies exists) assessing the radiation-induced damage to primordial oocytes in animal models, and even fewer data on radiation-induced damage to the stroma and reaction of immune cells in the ovary Study design, size, duration In this mouse model, 60 6-weeks old female C57BL/6J mice were radiated locally (abdomen[VS1] ) with either 1 or 4.5 Gy. There control group was not radiated. After radiation, mice were sacrificed and ovaries, pelvic lymph nodes, and the spleen were than analyzed by Fluorescence acitvated cell sorting (FACS) analysis at the Department of Gynecological Endocrinology and Reproductive Medicine, Medical University Innsbruck, Innsbruck, Austria between January and December 2023. Participants/materials, setting, methods After radiation, mice were sacrificed after 6h, 36h, 2 weeks and 5 weeks. Ovaries, pelvic lymph nodes, and the spleen were then analyzed by FACS analysis: NK cells, macrophages, dendritic cells, CD4+ and CD8+ cells, t cells and b cells were counted. The number of each cell type was compared to that of non-radiated mice. Main results and the role of chance The ovaries are composed of 1-2% immune cells. The immune cell population of the ovaries showed the following composition: NK cells including NK and NKT cells (34%; NKT (10%), T-cells (21%), macrophages (14%), B-cells (11%), dendritic cells (8%). In the ovary, within 6h after radiation no differences in the analyzed immune cells compared to the control group were seen, after 36h a significant increase of NK cells, macrophages, dendritic cells occurred in both groups (1 and 4.5Gy). Significant changes of levels of B Cells, dendritic cells, NK cells, den CD4+ and CD8+ cells remained after 2 weeks post radiation (p = 0.002). Five weeks post radiation, macrophages remained significantly elevated both in the low and high dose radiation group whereas other immune cell groups decrease to normal levels comparable to the control group. Analysis of the spleen and lymph nodes showed similar results. Limitations, reasons for caution A possible limitation is the small sample size. Wider implications of the findings This is the first study to analyze analyzing immune cells as part of the ovarian damage following radiation. Already shortly after low dose radiation, immune cells are activated in the mouse ovary, in line with activation in the spleen and lymph nodes dropping to normal levels within short time. Trial registration number No