Effect of Ionizing Radiation from Computed Tomography on Differentiation of Human Embryonic Stem Cells into Neural Precursors

We studied the effect of radiation from computed tomography (CT) scans on differentiation of human embryonic stem cells (hESCs) into neuronal lineage. hESCs were divided into three radiation exposure groups: 0-dose, low-dose, or high-dose exposure. Low dose was accomplished with a single 15 mGy CT dose index (CTDI) CT scan that approximated the dose for abdominal/pelvic CT examinations in adults while the high dose was achieved with several consecutive CT scans yielding a cumulative dose of 500 mGy CTDI. The neural induction was characterized by immunocytochemistry. Quantitative polymerase chain reaction (qPCR) and Western blots were used to measure expression of the neuronal markers PAX6 and NES and pluripotency marker OCT4. We did not find any visible morphological differences between neural precursors from irradiated and non-irradiated cells. However, quantitative analyses of neuronal markers showed that PAX6 expression was reduced following exposure to the high dose compared to 0-dose controls, while no such decrease in PAX6 expression was observed following exposure to the low dose. Similarly, a statistically significant reduction in expression of NES was observed following high-dose exposure, while after low-dose exposure, a modest but statistically significant reduction in NES expression was only observed on Day 8 of differentiation. Further studies are warranted to elucidate how lower or delayed expression of PAX6 and NES can impact human fetal brain development.