Screening for axonal retraction and cytotoxicity using dorsal root ganglia explants to treat pain caused by aberrant nerve sprouting

Abstract

Low back pain, knee osteoarthritis and cancer patients suffer from chronic pain. Aberrant nerve growth into intervertebral disc, knee, and tumors, are common pathologies that lead to these chronic pain conditions. Retraction of nerve fibers via capsaicin (Caps) or resiniferatoxin denervation have been used to treat painful neuropathies and knee osteoarthritis but with short-term efficacy and discomfort. Herein, we propose to repurpose pyridoxine (Pyr), vincristine sulfate (Vcr) and ionomycin (Imy) as potential axonal retraction compounds for denervation. Previous literature suggests Pyr, Vcr, and Imy each have undesired axonal degeneration as an off-target effect. Thus, we performed axonal retraction phenotype screening using adult rat dorsal root ganglia explants in vitro and assessed neurotoxicity. Imy did not induce axonal retraction, while Pyr and Vcr produced robust axonal retraction within three days. All DRGs treated with Caps, Pyr, Vcr, Imy or solvent had minimal neurotoxicity. Further, neither Pyr nor Vcr triggered nucleus pulposus cell death or affected cellular metabolic activity after three days of incubation. Overall, our findings suggest Pyr and Vcr are non-cytotoxic to dorsal root ganglia and nucleus pulposus cells, and there is potential for repurposing as axonal retraction compounds for local denervation.