An immunohistochemical study of radial glial cells in the mouse brain prenatally exposed to gamma-irradiation.

The features of a glial cell population in the developing brain of mice prenatally exposed to 60Co gamma-irradiation at the most radiosensitive stage were studied with immunohistochemistry for anti-midkine (MK), anti-vimentin (Vim), and anti-GFAP antibodies. Anti-MK- and anti-Vim-positive radial glial fibers distributed in a similar radial fashion; these fibers were observed primarily in the embryonic period and disappeared after birth. Anti-MK- and anti-Vim-stained radial fibers ran perpendicular to the pial surface in controls, whereas such fibers were disorganized 6 hours (h) after irradiation. This finding provided new evidence that the migratory pathways of young neurons were interrupted beginning a few hours after irradiation. By E17 the ectopic cell masses formed so as to replace the parts of the ventricular zone where no anti-MK immunoreactive radial fibers were present, but where anti-GFAP-stained fibrillary astrocytes emerged in the ectopic cell masses from the early postnatal period. The results suggested a twofold source of the generated astrocytes: either directly from a separate precursor of the astrocytes, or due to the transformation of the classic radial glial cells. In the newborn, numerous protoplasmic transitional forms displaced by astrocytes in irradiated brains indicated that reactive gliosis was a powerful response of a brain exposed to irradiation.