Low-dose radiation stimulates Wnt/β-catenin signaling, neural stem cell proliferation and neurogenesis of the mouse hippocampus in vitro and in vivo.

Neurogenesis in the hippocampus is actively involved in neural circuit plasticity and learning function of mammals, but it may decrease dramatically with aging and aging-related neurodegenerative disorder Alzheimer's disease. Accumulating studies have indicated that Wnt/β-catenin signaling is critical in control of proliferation and differentiation fate of neural stem cells or progenitors in the hippocampus. In this study, the biological effects of low-dose radiation in stimulating Wnt/β-catenin signaling, neural stem cell proliferation and neurogenesis of hippocampus were interestingly identified by in vitro cell culture and in vivo animal studies. First, low-dose radiation (0.3Gy) induced significant increasing of Wnt1, Wnt3a, Wnt5a, and β-catenin expression in both neural stem cells and in situ hippocampus by immunohistochemical and PCR detection. Secondly, low-dose radiation enhanced the neurogenesis of hippocampus indicated by increasing proliferation and neuronal differentiation of neural stem cells, going up of nestin-expressing cells and BrdU-incorporation in hippocampus. Thirdly, it promoted cell survival and reduced apoptotic death of neuronal stem cells by flowcytometry analysis. Finally, Morris water-maze test showed behavioral improvement of animal learning in low-dose radiation group. Accordingly, detrimental influence on Wnt/β-catenin signaling or neurogenesis was confirmed in high-dose radiation (3.0Gy) group. Taken together, this study has revealed certain beneficial effects of low-dose radiation to stimulate neural stem cell proliferation, the neurogenesis of hippocampus and animal learning most possibly by triggering Wnt/β-catenin signaling cascades, suggesting its translational application role in devising new therapy for aging-related neurodegenerative disorders particularly Alzheimer's disease.