Hippocampal GAD67 Transduction Using rAAV8 Regulates Epileptogenesis in EL Mice

Kuniko Shimazaki,Takashi Kobari,Keiji Oguro,Hidenori Yokota,Yuko Kasahara,Yoshiya Murashima,Eiju Watanabe,Kensuke Kawai,Takashi Okada

doi:10.1016/j.omtm.2018.12.012

Abstract

Gene therapy has been employed as a therapeutic approach for intractable focal epilepsies. Considering the potential of focal GABAergic neuromodulation in regulating epileptogenesis, the GABA-producing enzyme, γ-aminobutyric acid decarboxylase 67 (GAD67), is highly suitable for epilepsy therapy. The EL/Suz (EL) mouse is a model of multifactorial temporal lobe epilepsy. In the present study, we examined focal gene transduction in epileptic EL mice using recombinant adeno-associated virus serotype 8 (rAAV8) expressing human GAD67 to enhance GABA-mediated neural inhibition. Eight-week-old mice were bilaterally injected with rAAV8-GFP or rAAV8-GAD67 in the hippocampal CA3 region. After four weeks, the GAD67-transduced EL mice, but not the rAAV-GFP-treated EL mice, exhibited a significant reduction in seizure generation. The GAD67-mediated depression became stable after 14 weeks. The excitability of the CA3 region was markedly reduced in the GAD67-transduced EL mice, consistent with the results of the Ca2+ imaging using hippocampal slices. In addition, downregulation of c-Fos expression was observed in GAD67-transduced hippocampi. Our findings showed that rAAV8-GAD67 induced significant changes in the GABAergic system in the EL hippocampus. Thus, rAAV8-mediated GAD67 gene transfer is a promising therapeutic strategy for the treatment of epilepsies.

Highlights

Epilepsy is a common seizure disorder and represents one of the most prevalent neurological disorders worldwide.[1]
We evaluated the transduction pattern using recombinant adeno-associated virus serotype 8 (rAAV8)-GFP, which has the same backbone as rAAV8-g-aminobutyric acid decarboxylase 67 (GAD67)
The results suggested rAAV8 can undergo both retrograde (CA3 to dentate gyrus (DG)) and anterograde (CA3 to subiculum) transport

Summary

Introduction

Epilepsy is a common seizure disorder and represents one of the most prevalent neurological disorders worldwide.[1] Pharmacotherapy for epilepsy is merely symptomatic and does not provide curative therapeutic benefits. Despite advances in the development of antiepileptic drugs, refractory epilepsy remains a major clinical problem that affects up to 35% of patients with partial epilepsy.[2] For intractable cases in which patients develop tolerance and show pronounced side effects, surgical resection is the final option when a discrete seizure focus can be identified. The use of the adeno-associated virus (AAV) vector to regulate epileptogenesis constitutes a major therapeutic advancement for the treatment of refractory epilepsy. In this context, intractable pharmacoresistant focal seizures are suited for gene therapy

Methods

Results

Conclusion