Abstracts

The long-held doctrine that no new neurons generate in the brains of adult mammals has been overturned by recent evidence of neurogenesis in the olfactory bulb and dentate gyrus of rodents and primates. The most recent evidence has been obtained through immunocytochemical (ICC) visualization of bromodeoxyuridine (BrdU) uptake into the DNA of neurons in S-phase of the cell cycle. Our objective was to test the hypothesis that neurogenesis occurs in human hippocampal sclerosis (HS).
Tissue resected from 8 adult patients with drug resistant mesial temporal lobe epilepsy was received fresh and used for the experiments (Mean age=33.6y, SD=9y, M/F=2/6) . Neocortical temporal and hippocampal slices of 300-400[mu]m were incubated at 37[deg]C in 5% CO[sub]2[/sub] in Neurobasal (Gibco) medium supplemented with N2, B27, and L-glutamate (Gibco) with 0.25%BrdU solution for 24 hours. Slices were then fixed and sectioned (50[mu]m thick). Cresylecht violet (CV)/hematoxylin eosin (HE) and immunocytochemical (ICC) staining using BrdU antibodies (Becton-Dickenson) were performed on adjacent sections.
CV and HE staining confirmed the diagnosis of HS and the absence of neocortical pathology in 7 patients. In 3 patients with HS, there was evidence of BrDU uptake in the hilus. One patient who had no HS showed histological findings consistent with cortical dysplasia and displayed no hippocampal BrDU uptake. There was no evidence of neocortical BrDU uptake in any of the 8 patients included in the study.
These preliminary results suggest the presence of neurogenesis in some patients with drug resistant temporal lobe epilepsy due to hippocampal sclerosis. The mechanism(s) and significance of neurogenesis in these patients remain unknown. Further studies are underway to correlate the hippocampal neurogenesis with various histological and clinical characteristics.
[Supported by: Grants from the National Institute of Neurological Disorders and Stroke (NINDS) to IN]