Track: 1. Basic Mechanisms / 1A. Epileptogenesis of acquired epilepsies
Laura A. Bell
University of Utah
Salt Lake City, Utah
Male and female C57BL6/J mice were injected intracortically with 2x105 plaque forming units of TMEV or PBS (n=8 per group). Mice were graded twice daily for seizures on a modified Racine scale between 3 – 7 days post-injection (dpi). At 4 and 14 dpi, brains were fixed (n=4 per group at each timepoint) and stained for NG2 and Iba1, or NG2 and Ki67. Confocal z-stacks were acquired in both the ipsilateral CA1 region of the hippocampus and the overlying cortex. Total field areas stained by each cell marker and total field area of colocalized pixels between NG2 and Ki67 were measured through each section then averaged across triplicate sections.
Both NG2 cells and microglia displayed reactive morphologies in the CA1 region of TMEV-injected mice at 4 and 14 dpi as measured by significantly greater immunoreactivity of NG2 and Iba1. While increased immunoreactivity for Iba1 was also present in the cortex, there was no significant change in NG2 immunoreactivity in the cortex. Glial activation in response to viral infection may also be manifested by increased proliferation. Colocalization analysis for NG2 and Ki67 revealed a significant increase in overlap between NG2 and Ki67 in CA1 of TMEV-injected mice at both 4 and 14 dpi, but no significant difference in cortex.
NG2 cells acquire a reactive phenotype and increased proliferation in response to TMEV-infection. The reactive NG2 response is tightly localized to CA1, the site of active viral infection and seizure focus. These results suggest that NG2 cells alter their function in response to viral encephalopathy. Future studies are aimed at understanding whether these changes are promoting or preventative of neuronal hyperexcitability, seizures, and inflammation in the development of epilepsy.
Funding: Please list any funding that was received in support of this abstract.: NSF Graduate Research Fellowship and NIH/NINDS R37NS065434