IP 3 R-mediated intra-axonal Ca 2+ release contributes to secondary axonal degeneration following contusive spinal cord injury

• Published in: Neurobiology of disease Vol. 146; p. 105123
• Main Authors: Orem, Ben C, Rajaee, Arezoo, Stirling, David P
• Format: Journal Article
• Language: English
• Published: United States 01-12-2020
• Subjects: Intravital microscopy; Neuroprotection; IP3R; Contusion; Axon degeneration; Spinal cord injury
• ISSN: 1095-953X

Secondary axonal loss contributes to the persistent functional disability following trauma. Consequently, preserving axons following spinal cord injury (SCI) is a major therapeutic goal to improve neurological outcome; however, the complex molecular mechanisms that mediate secondary axonal degeneration remain unclear. We previously showed that IP
R-mediated Ca
release contributes to axonal dieback and axonal loss following an ex vivo laser-induced SCI. Nevertheless, targeting IP
R in a clinically relevant in vivo model of SCI and determining its contribution to secondary axonal degeneration has yet to be explored. Here we used intravital two-photon excitation microscopy to assess the role of IP
R in secondary axonal degeneration in real-time after a contusive-SCI in vivo. To visualize Ca
changes specifically in spinal axons over time, adult 6-8 week-old triple transgenic Avil-Cre:Ai9:Ai95 (sensory neuron-specific expression of tdTomato and the genetic calcium indicator GCaMP6f) mice were subjected to a mild (30 kdyn) T12 contusive-SCI and received delayed treatment with the IP
R blocker 2-APB (100 μM, intrathecal delivery at 3, and 24 h following injury) or vehicle control. To determine the IP
R subtype involved, we knocked-down IP
R3 using capped phosphodiester oligonucleotides. Delayed treatment with 2-APB significantly reduced axonal spheroids, increased axonal survival, and reduced intra-axonal Ca
accumulation within dorsal column axons at 24 h following SCI in vivo. Additionally, knockdown of IP
R3 yielded increased axon survival 24 h post-SCI. These results suggest that IP
R-mediated Ca
release contributes to secondary axonal degeneration in vivo following SCI.