Abstract
Radiation-induced skin fibrosis (RISF) is a chronic, debilitating consequence of radiotherapy for which no approved treatment reliably prevents or reverses disease progression. Because fibrosis develops from tissue injury responses, identifying the molecular events that initiate this process is an important translational goal. This dissertation defines early transcriptomic and molecular signatures associated with fibrotic remodeling after radiation injury using complementary human and murine models.
Donor-matched human ex vivo skin was exposed to single-dose irradiation and profiled by RNA-seq with tissue validation. This revealed a robust p53-mediated DNA damage response with cell cycle arrest, apoptosis, senescence, pro-inflammatory cytokine induction and TGF-β1-mediated profibrotic signaling. Comparison with transcriptomic data from irradiated breast skin biopsies collected from post-mastectomy patients at reconstruction supported the translational relevance of the model. In parallel, a murine model of fractionated irradiation was analyzed across multiple time points. Bulk RNA-seq revealed hair follicle cycling as a major transcriptional confounder, prompting use of Visium HD spatial transcriptomics. This identified 12 distinct cell populations and enabled cell-type-specific analysis of radiation responses previously obscured at the bulk level.
Human RNA-seq also revealed suppression of cholesterol biosynthesis regulators SREBF1 and SREBF2 with dynamic changes in downstream genes. Biochemical quantification confirmed transient cholesterol depletion immediately post-irradiation with recovery by 24 hours. Pretreatment with simvastatin prevented this depletion and increased cholesterol levels, suggesting early cholesterol dynamics as a potential therapeutic target.
Together, these findings characterize early transcriptomic and cholesterol-mediated responses in complementary human and murine models, identifying candidate mechanisms and therapeutic targets for the mitigation and treatment of RISF.