Impaired DNA Double-Strand Break Repair in Irradiated Sheep Lung Fibroblasts: Late Effects of Previous Irradiation of the Spinal Thecal Sac

Childhood cancer survivors treated with radiotherapy face the likelihood of long-term complications, including mutations. In order to assess the long-term effect of radiotherapy on the capacity of cells to repair their DNA double-strand breaks (DSBs), five lambs received medulloblastoma radiotherapy to the thecal sac, with three lambs serving as controls. Four years later, lung biopsies were taken and fibroblast cells were amplified and re-irradiated. The cells from the previously treated sheep showed a significant impairment of their DNA DSB repair mechanism, highlighting a potential increase in radiosensitivity. Our results show that previous irradiation can impair the DNA DSB repair mechanism of ovine lung fibroblasts. Children with cancer previously treated with radiotherapy face the likelihood of side effects that can be debilitating or fatal. This study aimed to assess the long-term effect of medulloblastoma radiotherapy on the DNA double-strand break (DSB) repair capability of primary fibroblasts derived from lung biopsies of previously irradiated young sheep. This study included biopsies from three control and five irradiated sheep. The treated sheep had previously received spinal radiotherapy at a total dose of 28 Gy, which is equivalent to pediatric medulloblastoma treatment. Lung biopsies were taken 4 years post-irradiation from high-dose (HD, >18 Gy) and low-dose (LD, <2 Gy) regions. Fifteen cell lines were extracted (six control, four LD and five HD). The cells were irradiated, and DNA DSB repair was analyzed by immunofluorescence. Clonogenic, trypan blue and micronuclei assays were performed. Both the HD and LD cell lines had a significantly higher number of residual gamma H2AX foci 24 h and a significant decrease in pATM activity post-irradiation compared to the control. There was no statistically significant difference in the clonogenic assay, trypan blue and micronuclei results. Our study showed that a previous irradiation can impair the DNA DSB repair mechanism of ovine lung fibroblasts.