UC San Diego

Chronic pain is a considerable issue facing society today. Current treatments for chronic pain consist mainly of opioids, highly imperfect solutions due to their side effects and high risk of addiction. This thesis aims to investigate a new avenue for treating chronic pain by taking a cue from nature. Individuals have been identified with congenital mutations to a gene encoding for a sodium channel subtype, Nav1.7, leading to total insensitivity to pain. Here we attempted to treat chronic pain via genetic targeting of SCN9A, the gene encoding for Nav1.7. Due to the desire to non-permanently ablate pain, we have utilized a variant of the CRISPR-Cas9 system without nuclease activity, dCas9 (dead-Cas9). The fusion of dCas9 to transcription regulators, such as the KRAB repressor, enables stable and efficient transcriptional repression. We delivered a dCas9-KRAB and a gRNA targeting the Nav1.7 gene via adeno-associated viruses (AAVs) to enable repression of pain, similar to a small-molecule drug, but, unlike small-molecules, lasting up to a few weeks. We injected mice with carrageenan to induce an inflammatory hyperalgesia pain model, performed nociceptive assays in order to verify a phenotypic change in pain sensation, and carried out qPCR to show repression of SCN9A. Results show ~50% repression of SCN9A was achieved, as well as a <100% improvement in thermal pain tolerance in the inflammatory state. Moving forward, this therapy could potentially be a future chronic pain treatment in humans without the negative side effects of current approaches.