Inhibiting Calcium Release from Ryanodine Receptors Protects Axons after Spinal Cord Injury

• Published in: Journal of neurotrauma Vol. 39; no. 3-4; p. 311
• Main Authors: Orem, Ben C, Rajaee, Arezoo, Stirling, David P
• Format: Journal Article
• Language: English
• Published: United States 01-02-2022
• Subjects: Animals; Axons - pathology; Calcium - metabolism; Disease Models, Animal; Intravital Microscopy; Mice; Mice, Transgenic; Ryanodine - antagonists & inhibitors; Ryanodine Receptor Calcium Release Channel; Spinal Cord - drug effects; Spinal Cord Injuries - complications; Spinal Cord Injuries - physiopathology; spinal cord injury; intravital microscopy; ryanodine receptor; secondary degeneration; axonal spheroids
• ISSN: 1557-9042
• DOI: 10.1089/neu.2021.0350

Ryanodine receptors (RyRs) mediate calcium release from calcium stores and have been implicated in axonal degeneration. Here, we use an intravital imaging approach to determine axonal fate after spinal cord injury (SCI) in real-time and assess the efficacy of ryanodine receptor inhibition as a potential therapeutic approach to prevent intra-axonal calcium-mediated axonal degeneration. Adult 6-8 week old
YFP transgenic mice that express YFP in axons, as well as triple transgenic
-Cre:Ai9:Ai95 mice that express the genetically-encoded calcium indicator GCaMP6f in tdTomato positive axons, were used to visualize axons and calcium changes in axons, respectively. Mice received a mild SCI at the T12 level of the spinal cord. Ryanodine, a RyR antagonist, was given at a concentration of 50 μM intrathecally within 15 min of SCI or delayed 3 h after injury and compared with vehicle-treated mice. RyR inhibition within 15 min of SCI significantly reduced axonal spheroid formation from 1 h to 24 h after SCI and increased axonal survival compared with vehicle controls. Delayed ryanodine treatment increased axonal survival and reduced intra-axonal calcium levels at 24 h after SCI but had no effect on axonal spheroid formation. Together, our results support a role for RyR in secondary axonal degeneration.