Cell and gene therapy via human neural stem progenitor cells in the lithium-pilocarpine model of rat temporal lobe epilepsy

Abstract

Temporal lobe epilepsy (TLE), the most common and intractable type of adult focal epilepsy, is typically associated with pathological alterations in the hippocampus and parahippocampal regions. TLE is an attractive target for cell therapy due to its focal nature and associated cellular defects. Neural stem/progenitor cells (NSPCs) can continuously self-renew and give rise to intermediate and mature cells of both neuronal and glial lineages. Following transplantation in the diseased brain, NSPCs exhibit the potential to migrate toward the lesion and replace degenerated or ablated cells, as well as deliver therapeutic substances.

In this study, we transplanted human NSPCs (hNSPCs), derived from an aborted fetal telencephalon at 13 weeks of gestation and expanded in culture as neurospheres over a long time period, into the lateral ventricles of lithium-pilocarpine induced epileptic rats. Implanted hNSPCs migrated and integrated into the recipient brain. The majority of hNSPCs remained undifferentiated, although subsets of donor-derived cells differentiated into all three neural cell types of the central nervous system and expressed inhibitory neurotransmitter gamma-aminobutyric acid (GABA). We found that hNSPC transplantation significantly reduced the frequency and duration of spontaneous recurrent motor seizures (SRMS) at 2 and 3 months post-transplants. In addition, hNSPC-transplanted epileptic rats showed neuroprotection, restoration of astrocytic glial cell-derived neurotrophic factor (GDNF) expression, and up-regulation of anti-inflammatory cytokines in the hippocampus. Finally, we demonstrated that conditioned medium from hNSPCs has neuroprotective action in an in vitro model of glutamate excitotoxicity. These results suggest that hNSPC transplantation possesses a therapeutic potential for treating TLE.

Next, we assessed the therapeutic efficacy of combined hNSPC and gene therapy in TLE. hNSPCs were engineered to secrete anticonvulsant neuropeptide galanin (GAL-hNSPCs) via adenoviral transduction. GAL-hNSPCs and green fluorescent protein (GFP)-expressing hNSPCs (GFP-hNSPCs) were transplanted into the hippocampus of lithium-pilocarpine induced epileptic rats. Transplanted both cell types migrated and dispersed throughout the hippocampus, and differentiated into TUJ1-, GFAP-, OLIG2-, and GABA-expressing cells. GFP-hNSPC transplantation significantly reduced the frequency and duration of SRMS at 3 months post-transplants, while GAL-hNSPC transplantation significantly reduced SRMS through all the time periods for 3 months following implantation. Moreover, GAL-hNSPC transplantation reversed the decreased anxiety seen in epileptic rats. GFP-hNSPC or GAL-hNSPC transplantation ameliorated neuronal loss, suppressed mossy fiber sprouting, and restored astrocytic GDNF expression in the hippocampus. GAL-hNSPC transplantation enhanced neuroprotection and reversed the declined neurogenesis. These results suggest that GAL-hNSPC transplantation represents a novel combined stem cell and gene therapy for suppressing seizures and rescuing emotional deficit in severely epileptic rats.