A human ex vivo model of radiation-induced skin injury recapitulates p53-driven pro-fibrotic response to radiotherapy

Cutaneous radiation injury is an unintended consequence of radiotherapy for many common cancers and can progress to debilitating radiation-induced skin fibrosis (RISF). Existing radiation injury models do not fully capture the skin toxicities observed in patients, contributing to the lack of efficacious therapies to mitigate RISF. To address this, we developed an ex vivo human skin model that recapitulates the temporal radiation injury and RISF response. Human skin explants (N=12) subjected to ionizing radiation demonstrated DNA double-strand breaks and robust p53-driven transcriptional programming of cell cycle arrest, apoptosis, and senescence compared to non-irradiated controls. Irradiated skin also exhibited induction of pro-inflammatory cytokines, epithelial-mesenchymal transition, pro-fibrotic TGF-beta1 (TGFB1)-mediated signaling, and thickened collagen over time. P53 regulators murine double minute 2 (MDM2) and microRNA (miR)-34a were induced post-irradiation and may be leveraged to modulate injury response. Notably, RNA-sequencing of breast skin from mastectomy patients post-radiotherapy showed similar p53, inflammatory, and TGFB1 signatures as the ex vivo model, supporting its translational relevance. Together, this model provides a platform for identifying biomarkers and testing therapies to prevent or mitigate cutaneous radiation toxicities. Targeting the dynamic p53-driven pro-fibrotic radiation response represents a new therapeutic avenue to improve post-radiotherapy quality of life for cancer survivors.