Intra-articular AAV-PHP.S mediated chemogenetic targeting of knee-innervating dorsal root ganglion neurons alleviates inflammatory pain in mice

Abstract

24Objective: 25 Joint pain is the major clinical symptom of arthritis that affects millions of people. 26Controlling the excitability of knee-innervating dorsal root ganglion (DRG) neurons (knee 27 neurons) could potentially provide pain relief. Therefore, our objective was to evaluate 28 whether the newly engineered adeno-associated virus (AAV) serotype, AAV-PHP.S, can 29 deliver functional artificial receptors to control knee neuron excitability following intra-30 articular knee injection. 31 Methods: 32AAV-PHP.S virus packaged with dTomato fluorescent protein and either excitatory (Gq) or 33 inhibitory (Gi) designer receptors activated by designer drugs (DREADDs) was injected 34 into the knee joint of adult mice. Labelling of DRG neurons by AAV-PHP.S from the knee 35 was evaluated using immunohistochemistry. Functionality of Gq-and Gi-DREADDs was 36 evaluated using whole-cell patch clamp electrophysiology on acutely cultured DRG 37 neurons. Pain behavior in mice was assessed using a digging assay, dynamic weight bearing 38 and rotarod, before and after intra-peritoneal administration of the DREADD activator, 39Compound 21. 40 Results: 41We show that AAV-PHP.S can deliver functional genes into the DRG neurons when 42 injected into the knee joint in a similar manner to the well-established retrograde tracer, fast 43 blue. Short-term activation of AAV-PHP.S delivered Gq-DREADD increases excitability 44 of knee neurons in vitro, without inducing overt pain in mice when activated in vivo. By 45 contrast, in vivo Gi-DREADD activation alleviated complete Freund's adjuvant mediated 46 3 knee inflammation-induced deficits in digging behavior, with a concomitant decrease in 47 knee neuron excitability observed in vitro. 48 Conclusions 49We describe an AAV-mediated chemogenetic approach to specifically control joint pain, 50 which may be utilized in translational arthritic pain research.

Human Labor Pain Is Influenced by the Voltage-Gated Potassium Channel KV6.4 Subunit

“…This result likely explains the reduction in labor pain seen in individuals in our cohort who were heterozygotes for the SNP rs140124801 rare allele. Although the results contained herein demonstrate the effect of K V 6.4-Met419 on neuronal excitability, another way to demonstrate this would be to generate transgenic mice or use adeno-associated viruses to transduce sensory neurons innervating a specific target, as conducted recently with the knee ( Chakrabarti et al., 2020 ). Using mice overexpressing K V 6.4-Met419, we hypothesize that, like humans expressing the SNP rs140124801 rare allele, these K V 6.4-Met419 mice might have a raised threshold to acute noxious stimuli compared with wild-type mice and potentially have a reduced chronic pain phenotype, results that would align with the known roles of K V channels in mouse pain behavior; for example, knockout of K V 9.1 leads to increased basal mechanical pain and exacerbates neuropathic pain ( Tsantoulas et al., 2018 ).…”