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Updated: May 2, 2026
Photothrombosis-induced Focal Ischemia as a Model of Spinal Cord Injury in Mice
Published on: July 16, 2015
Toll-like receptor 4-dependent microglial activation mediates spinal cord ischemia-reperfusion injury
Marshall T Bell1, Ferenc Puskas, Viktor A Agoston
1Departments of Cardiothoracic Surgery (M.T.B., V.A.A., J.C.C., K.A.F., F.G., X.M., P.D.S., M.J.W., D.A.F., T.B.R.) and Anesthesiology (F.P., P.S.H.), University of Colorado, Denver, CO.
Background:
Paraplegia continues to complicate thoracoabdominal aortic interventions. The elusive mechanism of spinal cord ischemia-reperfusion injury has delayed the development of pharmacological adjuncts. Microglia, the resident macrophages of the central nervous system, can have pathological responses after a variety of insults. This can occur through toll-like receptor 4 (TLR-4) in stroke models. We hypothesize that spinal cord ischemia-reperfusion injury after aortic occlusion results from TLR-4-mediated microglial activation in mice.
Methods And Results:
TLR-4 mutant and wild-type mice underwent aortic occlusion for 5 minutes, followed by 60 hours of reperfusion when spinal cords were removed for analysis. Spinal cord cytokine production and microglial activation were assessed at 6 and 36 hours after surgery. Isolated microglia from mutant and wild-type mice were subjected to oxygen and glucose deprivation for 24 hours, after which the expression of TLR-4 and proinflammatory cytokines was analyzed. Mice without functional TLR-4 demonstrated decreased microglial activation and cytokine production and had preserved functional outcomes and neuronal viability after thoracic aortic occlusion. After oxygen and glucose deprivation, wild-type microglia had increased TLR-4 expression and production of proinflammatory cytokines.
Conclusions:
The absence of functional TLR-4 attenuated neuronal injury and microglial activation after thoracic aortic occlusion in mice. Furthermore, microglial upregulation of TLR-4 occurred after oxygen and glucose deprivation, and the absence of functional TLR-4 significantly attenuated the production of proinflammatory cytokines. In conclusion, TLR-4-mediated microglia activation in the spinal cord after aortic occlusion is critical in the mechanism of paraplegia after aortic cross-clamping and may provide targets for pharmacological intervention.
Insights
Spinal cord injury after aortic surgery involves toll-like receptor 4 (TLR-4) activation in microglia. Blocking TLR-4 reduces inflammation and protects neurons, offering a potential therapeutic target for preventing paraplegia.
Area of Science:
- Neuroscience
- Immunology
- Cardiovascular Surgery
Background:
- Paraplegia is a complication of thoracoabdominal aortic interventions.
- Spinal cord ischemia-reperfusion injury mechanisms are not fully understood, hindering pharmacological treatments.
- Microglial activation via toll-like receptor 4 (TLR-4) is implicated in central nervous system injury.
Purpose of the Study:
- To investigate the role of TLR-4-mediated microglial activation in spinal cord ischemia-reperfusion injury following aortic occlusion in a mouse model.
- To determine if blocking TLR-4 can mitigate neuronal damage and functional deficits.
Main Methods:
- Mice lacking functional TLR-4 and wild-type controls underwent aortic occlusion and reperfusion.
- Spinal cord cytokine production and microglial activation were assessed.
- Isolated microglia were subjected to oxygen-glucose deprivation to analyze TLR-4 expression and cytokine release.
Main Results:
- Mice without functional TLR-4 showed reduced microglial activation, lower cytokine production, and preserved neuronal viability and function after aortic occlusion.
- Wild-type microglia exhibited increased TLR-4 expression and pro-inflammatory cytokine production following oxygen-glucose deprivation.
- The absence of TLR-4 significantly attenuated the inflammatory response and neuronal injury.
Conclusions:
- TLR-4-mediated microglial activation is critical in causing paraplegia after aortic cross-clamping.
- Targeting TLR-4 in microglia presents a promising strategy for pharmacological intervention to prevent spinal cord injury.
- The findings highlight TLR-4 as a key mediator in the pathogenesis of paraplegia post-aortic surgery.
