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Chemogenetic enhancement of functional recovery after a sciatic nerve injury.

ABSTRACT: Designer receptors exclusively activated by designer drugs (DREADDs) are chemogenetic tools used to modulate neuronal excitability. We hypothesized that activation of excitatory (Gq) DREADD by its designer ligand, clozapine-N-oxide (CNO), would increase the excitability of neurons whose axons have been transected following peripheral nerve injury, and that this increase will lead to an enhanced functional recovery. The lateral gastrocnemius (LG) muscle of adult female Lewis rats was injected unilaterally with AAV9- hsyn- hM3Dq-mCherry (7.6 × 109 viral genomes/?L) to transduce Gq-DREADD expression in LG neurons. The contralateral LG muscle served as an uninjected control. No significant changes in either spontaneous EMG activity or electrically evoked direct muscle (M) responses were found in either muscle after injection of CNO (1 mg/kg, i.p.). The amplitude of monosynaptic H-reflexes in LG was increased after CNO treatment exclusively in muscles previously injected with virus, suggesting that Gq-DREADD activation increased neuronal excitability. After bilateral sciatic nerve transection and repair, additional rats were treated similarly with CNO for up to three days after injury. Electrophysiological data were collected at 2, 4 and 6 weeks after injury. Evoked EMG responses were observed as early as 2 weeks after injury only in Gq-DREADD expressing virus injected LG muscle. By 4 weeks after injury, both M-response and H-reflex amplitudes were significantly greater in muscles previously injected with viral vector than contralateral, uninjected muscles. Increases in the excitability of injured neurons produced by this novel use of Gq-DREADD were sufficient to promote an enhancement in functional recovery after a sciatic nerve injury.

SUBMITTER: Jaiswal PB

PROVIDER: S-EPMC5438293 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Chemogenetic enhancement of functional recovery after a sciatic nerve injury.

Jaiswal Poonam B PB English Arthur W AW

The European journal of neuroscience 20170328 10

Designer receptors exclusively activated by designer drugs (DREADDs) are chemogenetic tools used to modulate neuronal excitability. We hypothesized that activation of excitatory (Gq) DREADD by its designer ligand, clozapine-N-oxide (CNO), would increase the excitability of neurons whose axons have been transected following peripheral nerve injury, and that this increase will lead to an enhanced functional recovery. The lateral gastrocnemius (LG) muscle of adult female Lewis rats was injected uni ...[more]

PMID: 28244163

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Project description:PurposeOur study is aimed at investigating the mechanism by which electroacupuncture (EA) promoted nerve regeneration by regulating the release of exosomes and exosome-mediated miRNA-21 (miR-21) transmission. Furthermore, the effects of Schwann cells- (SC-) derived exosomes on the overexpression of miR-21 for the treatment of PNI were investigated.MethodsA sciatic nerve injury model of rat was constructed, and the expression of miR-21 in serum exosomes and damaged local nerves was detected using RT-qPCR after EA treatment. The exosomes were identified under a transmission electron microscope and using western blotting analysis. Then, the exosome release inhibitor, GW4869, and the miR-21-5p-sponge used for the knockdown of miR-21 were used to clarify the effects of exosomal miR-21 on nerve regeneration promoted by EA. The nerve conduction velocity recovery rate, sciatic nerve function index, and wet weight ratio of gastrocnemius muscle were determined to evaluate sciatic nerve function recovery. SC proliferation and the level of neurotrophic factors were assessed using immunofluorescence staining, and the expression levels of SPRY2 and miR-21 were detected using RT-qPCR analysis. Subsequently, the transmission of exosomal miR-21 from SC to the axon was verified in vitro. Finally, the exosomes derived from the SC infected with the miR-21 overexpression lentivirus were collected and used to treat the rat SNI model to explore the therapeutic role of SC-derived exosomes overexpressing miR-21.ResultsWe found that EA inhibited the release of serum exosomal miR-21 in a PNI model of rats during the early stage of PNI, while it promoted its release during later stages. EA enhanced the accumulation of miR-21 in the injured nerve and effectively promoted the recovery of nerve function after PNI. The treatment effect of EA was attenuated when the release of circulating exosomes was inhibited or when miR-21 was downregulated in local injury tissue via the miR-21-5p-sponge. Normal exosomes secreted by SC exhibited the ability to promote the recovery of nerve function, while the overexpression of miR-21 enhanced the effects of the exosomes. In addition, exosomal miR-21 secreted by SC could promote neurite outgrowth in vitro.ConclusionOur results demonstrated the mechanism of EA on PNI from the perspective of exosome-mediated miR-21 transport and provided a theoretical basis for the use of exosomal miR-21 as a novel strategy for the treatment of PNI.

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Chemogenetic enhancement of functional recovery after a sciatic nerve injury.

Publications

Chemogenetic enhancement of functional recovery after a sciatic nerve injury.

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