Cell transplantation strategies capable of diminishing spontaneous recurrent seizures (SRS), learning and memory dysfunction and depression in chronic temporal lobe epilepsy (TLE) have great significance because ~35% of patients with TLE have SRS that are resistant to antiepileptic drugs (AEDs) and AED therapy does not reduce cognitive and mood dysfunction. As TLE is associated with a paucity of inhibitory GABA-ergic neurons and astrocytes secreting the anticonvulsant protein glial cell line-derived neurotrophic factor (GDNF), cell grafts that have the ability to give rise to both GABA-ergic neurons and GDNF+ astrocytes appear attractive for restraining SRS. Indeed, our recent study has shown that grafting of the medial ganglionic eminence (MGE) derived neural stem cells (NSCs) into the hippocampus of rats exhibiting chronic TLE substantially reduces the frequency and intensity of SRS with additions of new GABA-ergic neurons and GDNF+ astrocytes. However, no improvements were seen in the hippocampal neurogenesis or cognitive function. Analyses of grafts revealed that the overall yield of graft-derived cells was only 28% of injected cells and engrafting of cells into th neurogenic subgranular zone (SGZ) was minimal. This finding suggested that lack of improvements in neurogenesis and cognition after MGE-NSC grafting is a consequence of both lower yield and reduced migration of graft- derived cells. We hypothesize that combined grafting of MGE-NSCs into the hippocampus and peripheral administration of neurogenic compounds will greatly diminish SRS as well as reverse memory dysfunction and depression seen in chronic TLE. We propose that such improved functional recovery will be associated with engrafting of significant numbers of graft-derived cells into the SGZ, generation of greater numbers of new GABA-ergic neurons and GDNF+ astrocytes from grafts, restoration of the host hippocampal GDNF concentration, increased hippocampal neurogenesis, and normalization in the concentration/expression of proteins/genes important for cognitive and mood function and neurogenesis. In this project, we will investigate whether combined intrahippocampal grafting of MGE-NSCs and neurogenic drug treatment strategies would greatly diminish SRS, cognitive dysfunction and depression in a rat model of chronic TLE.
In Specific Aim 1, we will ascertain the effects of combined intrahippocampal grafting of MGE-NSCs and subcutaneous (S.C.) FGF-2 treatment for 14 days.
In Specific Aim 2, we will examine the effects of combined intrahippocampal grafting of MGE-NSCs with S.C. administration of neurosteroid analog ganaxolone. We will test whether seizure-suppression and improved cognitive and mood function mediated by these combination therapies are linked to an increased yield of graft-derived GABA-ergic neurons and GDNF-positive astrocytes, engrafting of greater numbers of graft-derived NSCs into the neurogenic SGZ, increased activity of endogenous NSCs and hippocampal neurogenesis, and enhanced expression of proteins/genes vital for cognitive and mood functions. We will also compare these results with data obtained from grafts of MGE-derived GABA-ergic cells and MGE-NSC derived astrocyte grafts in the presence or absence of FGF-2/Ganaxolone treatment. The proposed studies have promise for providing the critical benchmarks essential for considering clinical application of NSC grafting strategies for treating chronic TLE. The studies are also relevant to the health care needs of Veterans, as combat related moderate to severe head injuries among soldiers who served in Iraq and Afghanistan wars might lead to chronic TLE in the coming years.
Antiepileptic drug therapy is inefficient for controlling seizures in ~35% patients with chronic temporal lobe epilepsy and drug therapy is not efficacious for alleviating the co-morbidities of temporal lobe epilepsy such as cognitive and mood dysfunction. Hence, efficient alternative therapies are needed. This project will ascertain the efficacy of combined intrahippocampal grafting of neural stem cells and neurogenic drug treatment strategies for greatly diminishing spontaneous seizures, cognitive dysfunction and depression in a rat model of chronic temporal lobe epilepsy. The overall goal is to develop an efficient cell based therapy for chronic temporal lobe epilepsy.
