Abstract
Treatment-related sequelae following cranial irradiation have life changing impacts for patients and their caregivers. Characterization of the basic response of human brain tissue to irradiation has been difficult due to a lack of preclinical models. The direct study of human brain tissue in vitro is becoming possible due to advances in stem cell biology, neuroscience, and tissue engineering with the development of organoids as novel model systems which enable experimentation with human tissue models. We sought to establish a cerebral organoid (CO) model to study the radioresponse of normal human brain tissue. COs were grown using human induced pluripotent stem cells and a modified Lancaster protocol. Compositional analysis during development of the COs showed expected populations of neurons and glia. We confirmed a population of microglia-like cells within the model positive for the makers Iba1 and CD68. After 2-months of maturation, COs were irradiated to 0, 10, and 20 Gy using a Shepard Mark-II Cs-137 irradiator and returned to culture. Subsets of COs were prepared for immunostaining at 30- and 70-days post-irradiation. To examine the effect of irradiation on the neural stem cell (NSC) population, sections were stained for SOX2 and Ki-67 expression denoting NSCs and proliferation respectively. Slides were imaged and scored using the CellProfiler software package. The percentage of proliferating NSCs 30-days post-irradiation was found to be significantly reduced for irradiated COs (5.7% (P=0.007) and 3.4% (P=0.001) for 10 and 20 Gy respectively) compared to control (12.7%). The reduction in the proliferating NSC population subsequently translated to a reduced population of NeuN-labeled mature neurons 70 days post-irradiation. The loss of proliferating NSCs and subsequent reduction in mature neurons demonstrates the long-term effects of radiation. Our initial results indicate COs will be a valuable model to study the effects of radiation therapy on normal and diseased human tissue.
Neuronal localization of GAS7 within human brain tissue: Implications for schizophrenia research
