Dose-dependent short- and long-term effects of ionizing irradiation on neural stem cells in murine hippocampal tissue cultures: neuroprotective potential of resveratrol.

Abstract

IntroductionRadiation therapy plays an essential role in the treatment of brain tumors, but neurocognitive deficits remain a significant risk, especially in pediatric patients. In recent trials, hippocampal sparing techniques are applied to reduce these adverse effects. Here, we investigate dose‐dependent effects of ionizing radiation (IR) on juvenile hippocampal neurogenesis. Additionally, we evaluate the radioprotective potential of resveratrol, a plant polyphenol recognized for its bifunctional tumor‐preventive and anticancer effects.MethodsOrganotypic entorhinal–hippocampal slice cultures from transgenic nestin‐CFPnuc C57BL/J6 mice, postnatal days 3–6, were irradiated on a X‐ray machine (4.5, 8, 12, and 16 Gy, single doses) after about 2 weeks. Nestin‐positive neural stem cells were counted at a confocal live imaging microscope 0, 2, 4, 14, 25, and 42 days after IR. Resveratrol (15 μmol/L) was added 2 hr before and 24 hr after IR. Proliferation and cell death were assessed by BrdU pulse label, 48 hr after and by propidium iodide staining 96 hr after IR. GFAP‐ and NeuN‐positive cells were counted 42 days after IR in cryosectioned immunofluorescence‐stained slices.ResultsThe observed age‐related changes of nestin‐positive stem cells in the organotypic slice culture model resembled the reduction of neural stem cells in vivo. IR (4.5–16 Gy) led to a dose‐dependent damage of the neural stem cell pool in the dentate gyrus. No recovery was seen within 42 days after doses from 4.5 Gy onward. The decline of nestin‐positive cells was paralleled by increased cell death and decreased proliferation. The number of GFAP‐positive cells was significantly enhanced. No significant change was detected in the overall NeuN‐positive cell population, whereas the number of newborn, NeuN/BrdU double‐positive neurons was reduced. Resveratrol treatment reversed the irradiation‐induced decline of neural stem cells.ConclusionThe neuroprotective action of resveratrol on irradiated hippocampal tissue warrants further investigation as a possible supplement to hippocampal sparing procedures.