Optogenetic control of perforant pathway kindled seizures by photoinhibition of CA3 after insertion of Jaws into CA3 neuronal cells.

Medial temporal lobe epilepsy (MTLE) is among the most common and most drug-resistant types of epilepsies associated with remodeling of the trisynaptic circuit of the hippocampus. The cornu ammonis (CA)3 region, as the "pacemaker" of the circuit, and CA3 â†’ CA1 synapse (Schaffer collaterals) are potential targets for suppression of MTLE. We examined optogenetic manipulation of CA3 neurons in controlling the perforant pathway kindled seizures. One week after implantation of stimulating electrodes in perforant pathway, a recording electrode in CA1, and an optic fiber in CA3, rats underwent rapid kindling procedure. A lentivector with capability to move in retrograde monosynaptic direction and to insert the gene of red light sensitive opsin Jaws in neurons was injected into CA1 of the kindled rats. One week later, the kindled rats were stimulated at afterdischarge (AD) threshold under red light illumination to CA3; and duration of AD (ADD), generalized seizures (S5D), and total seizure behavior (SD) were recorded. Encoding Jaws in CA1, CA3, and entorhinal neuronal cells of the vector injected rats was verified by immunohistochemistry. More than 90% of CA1, CA3, and entorhinal neurons of the counted sections expressed Jaws. Red light (625 nm) illumination to CA3 of the kindled rats expressing Jaws entirely suppressed generalized seizures and significantly diminished ADD and SD. Encoding the light-sensitive chloride pump Jaws in the CA3, is an efficient optogenetic strategy to stop perforant pathway kindled seizures.

The Lentiviral Vector Pseudotyped by Modified Rabies Glycoprotein Does Not Cause Reactive Gliosis and Neurodegeneration in Rat Hippocampus

Background: A human immunodeficiency virus type 1 (HIV-1)-based lentiviral vector (LV) pseudotyped by a variant of rabies envelope glycoprotein, FUG-B2, has previously been prepared and used in transfection of hippocampal CA1 ("Cornu Ammonis" area 1) neurons. This study aimed to verify reactive gliosis and neuronal damage after injection of the vector into the rat hippocampus. Methods: HEK 293T cells were transfected with transfer (fck-Jaws-GFP-ER2), envelope (FUG-B2), and packaging (pMDLg/pRRE, pRSV-Rev) plasmids, and the vector was injected into CA1 of the rat hippocampus. After one week, transduction efficiency, and the number of neuronal and astroglial cells were determined in CA1 and CA3 by double staining of the brain slices. Results: Hippocampal cells were successfully transfected as 92.7% of CA1 and 95.8% of CA3 neuronal cells expressed GFP. The frequency of neuronal and astroglial cells in CA1 and CA3 of the vector-injected rats remained unchanged compared to those in the control and the saline-injected rats. Furthermore, no morphological change was found in hippocampal astrocytes and neuronal cells. Conclusion: The HIV-1-based LV pseudotyped by FUG-B2 is safe and does not cause neuroinflammation and neuronal loss once directly delivered into the rat hippocampus.

Transduction efficacy and retrograde movement of a lentiviral vector pseudotyped by modified rabies glycoprotein throughout the trisynaptic circuit of the rat hippocampus.

BACKGROUND: The trisynaptic circuit (entorhinal cortex-dentate gyrus-CA3-CA1) is a key unidirectional network in the hippocampus. Damage to the hippocampus interrupts this circuit and causes neurological disorders. Efficient delivery of therapeutic genes into this network is of great interest with respect to treating trisynaptic circuit pathologies. METHODS: We generated a lentivector system pseudotyped by a variant of rabies glycoprotein, FUG-B2. The efficiency of the vector in the retrograde transduction of the rat hippocampal neurons (i.e. the entorhinal cortex from the dentate gyrus, the dentate gyrus from CA3, and CA3 from CA1) was examined by direct injection of the vector into the dentate gyrus, CA3 and CA1. To distinguish transduction of the neuronal and glial cells, as well as selective retrograde gene transfer, double-staining of the green fluorescent protein (GFP) expressing cells with the specific neuron biomarker NeuN (neuronal nuclear protein) and the specific glia biomarker GFAP (glial fibrillary acidic protein) was performed across the network. RESULTS: The transgene was successfully introduced into the circuit. More than 80% of the neuronal and glial cells at the injection sites preserved GFP expression during the 2-month period after vector injection. Importantly, GFP was expressed selectively in almost 80.0% of the presynaptic neuronal cells by retrograde axonal transport of the vector. CONCLUSIONS: The FUG-B2-based vector system can efficiently introduce the transgene into the rat hippocampal neurons both directly and indirectly through retrograde monosynaptic movement. This efficient and long-lasting gene delivery might provide a tool for treating neurological disorders originating in hippocampal circuits.