Stage-dependent alterations of progenitor cell proliferation and neurogenesis in an animal model of Wernicke-Korsakoff syndrome

Abstract

Alcohol-induced Wernicke-Korsakoff syndrome (WKS) culminates in bilateral diencephalic lesion and severe amnesia. Using the pyrithiamine-induced thiamine deficiency (PTD) animal paradigm of WKS, our laboratory has demonstrated hippocampal dysfunction in the absence of gross anatomical pathology. Extensive literature has revealed reduced hippocampal neurogenesis following a neuropathological insult, which might contribute to hippocampus-based learning and memory impairments. Thus, the current investigation was conducted to determine whether PTD treatment altered hippocampal neurogenesis in a stage-dependent fashion. Male Sprague-Dawley rats were assigned to one of 4 stages of thiamine deficiency based on behavioral symptoms: pre-symptomatic stage, ataxic stage, early post-opisthotonus stage, or the late post-opisthotonus stage. The S-phase mitotic marker 5'-bromo-2'-deoxyuridine (BrdU) was administered at the conclusion of each stage following thiamine restoration and subjects were perfused 24 hours or 28 days after BrdU to assess cellular proliferation or neurogenesis and survival, respectively. Dorsal hippocampal sections were immunostained for BrdU (proliferating cell marker), NeuN (neurons), GFAP (astrocytes), Iba-1 (microglia), and O4 (oligodendrocytes). The PTD treatment increased progenitor cell proliferation and survival during the early post-opisthotonus stage. However, levels of neurogenesis were reduced during this stage as well as the late post-opisthotonus stage where there was also an increase in astrocytogenesis. The diminished numbers of newly generated neurons (BrdU/NeuN co-localization) was paralleled by increased BrdU cells that did not co-localize with any of the phenotypic markers during these later stages. These data demonstrate that long-term alterations in neurogenesis and gliogenesis might contribute to the observed hippocampal dysfunction in the PTD model and human WKS.

Figure 1

Schematic of the experimental design. On Day 1, all subjects were started on either PF or PTD treatment. Subjects that were assigned to the pre-symptomatic stage (PRE; n=32) were administered BrdU on Day 8 and their respective treatments were terminated. Subjects that were assigned to the ataxic stage (ATAX; n=32) were administered BrdU on Day 15 and their respective treatments were terminated. Subjects that were assigned to the early post-opisthotonus stage (E. Post; n=32) were administered BrdU 24 hr after thiamine reversal whereas subjects that were assigned to the late post-opisthotonus stage (L. Post; n=32) were administered BrdU 28 days after thiamine reversal. Subjects in each group were then sacrificed either 24-hours or 28-days after BrdU administration.

Figure 2

Comparison of the mean body weights (in grams) between PF- and PTD-treated subjects at different time points during and after PTD treatment (mean ± S.E.M.).

Figure 3

Stage-dependent estimates of progenitor cell proliferation in the hippocampal dentate gyrus of PF- and PTD-treated rats. Data expressed as mean ± S.E.M. # = p<0.01. Micrographs depict outline of GCL/SGZ of representative PF- and PTD-treated animals during the early post-opisthotonus stage. Images captured with a 4X objective.

Figure 4

Stage-dependent estimates of progenitor cell survival in the hippocampal dentate gyrus of PFand PTD-treated rats. Data expressed as mean ± S.E.M. * = p≤0.05. Micrographs depict outline of GCL/SGZ of representative PF- and PTD-treated animals during the early post-opisthotonus stage. Images captured with a 4X objective.