ESTRO 2024 - Abstract Book

S34 ESTRO 2024 serving as the isocenter, facilitated by the Small Animal Radiation Research Platform (SARRP). We have shown that IR induced intestinal damage is confined to the area around the marker, while the surrounding normal intestinal tissue remains preserved. Through comprehensive analysis, we observed that various types of immune cells infiltrated the irradiated mucosa, demonstrating significant localization compared to the adjacent non-IR tissue. This infiltration coincided with increased expression of several inflammatory cytokines, with IL-6 showing the most pronounced upregulation. Interestingly, we also noted increased proliferation at the wound-edge boundary, at the junction of the irradiated and non-irradiated areas. This hyperproliferation suggests that normal tissue is compensating for the regeneration of damaged intestinal epithelium induced by focal RT. In our preliminary data from a dose escalation study, where focal doses were escalated from 18 to 32 Gy, we observed 100% survival in mice receiving focal IR doses using a 5x5mm collimator. This contrasts with mice receiving whole abdomen IR (at all given doses), which succumbed to acute radiation syndrome. Moreover, when the irradiated area was expanded to 1 cm, mice subjected to 18 Gy focal IR succumbed within a week, indicating a volumetric limitation on the regenerative capacity of normal tissue for repairing damaged intestinal epithelium. Therefore, we propose that the adjacent normal intestinal epithelium plays a role in re-epithelializing the damaged tissue but within a constrained volume capacity. Our preliminary immunofluorescent staining data for several stem cell and other cell type markers in the IR area revealed a significant decrease in the percentage of radiosensitive crypt base columnar (CBC) stem cells, as indicated by OLFM4 and LGR5 markers, at day 1 post-IR. This percentage was undetectable at day 3 and nearly returned to baseline levels by day 7 post-IR. To further investigate the potential mechanism, we conducted single-cell RNA sequencing (scRNA-seq) of both the stromal and epithelial compartments from both IR and non-IR tissues at various time points (D0, D1, D3, and D7 post-IR). Initial findings from pathway analysis of the differentially expressed genes in fibroblasts and macrophages revealed that the most upregulated pathways were associated with epithelial cell migration and response to wounding. This suggests a potential migratory phenotype of epithelial cells, possibly stem cells, from the surrounding undamaged intestines into the irradiated region that has sustained damage. Moreover, to delve deeper into the potential migratory phenotype in a spatial context, we have scheduled high-definition spatial transcriptomic analysis of the focally irradiated intestinal tissues at the same time points as the scRNA-seq. This assay will provide insight into the relative positions of the "migratory" stem cells, aiding in a more precise characterization of the regeneration process. Additionally, we have applied our mouse model of focal IR on Lgr5-cre-ERT2::Rosa26-LSL tdTomato and Clu-cre-ERT2::Rosa26-LSL-tdTomato transgenic mice to further delineate the dynamics of CBC stem cells and revival stem cells following 18 Gy of focal IR. We anticipate that these studies will advance our understanding of intestinal epithelial regeneration using a clinically relevant mouse model, ultimately improving the therapeutic efficacy of abdominal radiotherapy. Invited Speaker

3330

ePROMs improves data collection

Ingrid Kristensen

Skåne University Hospital, Radiation Physics, Lund, Sweden

Abstract:

The overall aim of our study is to collect patient reported outcome measures (PROMs) for patients receiving radiotherapy (RT) at our hospital. Our RT department has a large catchment area with approximately 2 million people. The department treats about 4000 patients a year.