Functional electrical stimulation increases neural stem/progenitor cell proliferation and neurogenesis in the subventricular zone of rats with stroke

Abstract

Background Functional electrical stimulation (FES) is known to promote the recovery of motor function in rats with ischemia and to upregulate the expression of growth factors which support brain neurogenesis. In this study, we investigated whether postischemic FES could improve functional outcomes and modulate neurogenesis in the subventricular zone (SVZ) after focal cerebral ischemia. Methods Adult male Sprague-Dawley rats with permanent middle cerebral artery occlusion (MCAO) were randomly assigned to the control group, the placebo stimulation group, and the FES group. The rats in each group were further assigned to one of four therapeutic periods (1, 3, 7, or 14 days). FES was delivered 48 hours after the MCAO procedure and divided into two 10-minute sessions on each day of treatment with a 10-minute rest between them. Two intraperitoneal injections of bromodeoxyuridine (BrdU) were given 4 hours apart every day beginning 48 hours after the MCAO. Neurogenesis was evaluated by immunofluorescence staining. Wnt-3 which is strongly implicated in the proliferation and differentiation of neural stem cells (NSCs) was investigated by Western blotting analysis. The data were subjected to one-way analysis of variance (ANOVA), followed by a Tukey/Kramer or Dunnett post hoc test. Results FES significantly increased the number of BrdU-positive cells and BrdU/glial fibrillary acidic protein double-positive neural progenitor cells in the SVZ on days 7 and 14 of the treatment (P <0.05). The number of BrdU/doublecortin (DCX) double-positive migrating neuroblast cells in the ipsilateral SVZ on day 14 of the FES treatment group ((522.77±33.32) cells/mm2) was significantly increased compared with the control group ((262.58±35.11) cells/mm2, P <0.05) and the placebo group ((266.17±47.98) cells/mm2, P <0.05). However, only a few BrdU/neuron-specific nuclear protein-positive cells were observed by day 14 of the treatment. At day 7, Wnt-3 was upregulated in the ipsilateral SVZs of the rats receiving FES ((0.44±0.05)%) compared with those of the control group rats ((0.31±0.02)%, P <0.05) or the placebo group rats ((0.31±0.04)%, P <0.05). At day 14, the corresponding values were (0.56±0.05)% in the FES group compared with those of the control group rats ((0.50±0.06)%, P <0.05) or the placebo group rats ((0.48±0.06)%, P <0.05). Conclusion FES augments the proliferation, differentiation, and migration of NSCs and thus promotes neurogenesis, which may be related to the improvement of neurological outcomes.