Neural stem/progenitor cells damaged by reactive oxygen species evolved in photosensitizing reaction.

We want to know how the growth of neural stem/progenitor cells and their differentiation are affected by reactive oxygen species evolved in photosensitizing reaction, because of the similarity between the stem cells and the tumor cells in central nervous system. We investigated the effects of two photosensitizers (rhodamine 123 and hematoporphyrin) on the mouse neural stem/progenitor cells cultured in vitro under the illumination. ABC transporters were expressed in the cells, and could pump rhodamine 123 and hematoporphyrin out of the cells. Under the illumination of strong actinic light with those photosensitizers, reactive oxygen species was evolved to injure the cells. Number of viable cells decreased under illumination through apoptosis and necrosis. Those cell-killing activities were not clearly dependent on the presence of inhibitors for ABC transporters. Immunocytochemical staining with showed that immature cells with markers of neural stem/progenitor cells (Sox 2, CD133, nestin) were more sensitive to the reactive oxygen species than the differentiated cells.