Temporal Mapping of Radiation-Induced Changes in Human Brain Organoids using single-cell RNA sequencing

Radiation therapy (RT) is a standard-of-care oncological treatment for the central nervous system (CNS). However, during cranial RT, normal brain tissue adjacent to the tumors is inevitably irradiated, causing transient reversible abnormalities as well as progressive irreversible late toxicities. Approximately 100,000 patients with primary and metastatic brain tumors per year in the United States survive long enough (>6 months) to develop radiation-induced brain injury, including cognitive impairment and/or neurological sequelae, significantly impeding the quality of life. These symptoms occur in 50-90% of adult patients after treatment and can be seen without clinical and radiographic evidence of histological changes. Here we established a novel, robust, cell-based 3D brain organoid model that closely mimics the complexity of the human brain microenvironment, and explored the pathophysiologiacl processes and neuroinflammation induced by radiation in the normal brain tissue. Mature iPSC-derived brain organoids were exposed to fractionated irradiation, receiving 2 Gy per day for five consecutive days (total of 5 fractions). Control organoids underwent sham irradiation under identical conditions. Culture medium was refreshed every other day. Organoids were harvested and dissociated for single-cell RNA sequencing at two time points: 72 hours and 2 weeks following the final radiation dose.