In Vivo Two-Photon Imaging of Axonal Dieback, Blood Flow and Calcium Influx withMethylprednisolone Therapy after Spinal Cord Injury

Severe spinal cord injury (SCI) can cause neurological dysfunction and paralysis.However, the early dynamic changes of neurons and their surrounding environmentafter SCI are poorly understood. Although methylprednisolone (MP) is currently thestandard therapeutic agent for treating SCI, its efficacy remains controversial. Thepurpose of this project was to investigate the early dynamic changes andMP's efficacy on axonal damage, blood flow and calcium influx into axonsin a mouse SCI model. YFP H-line and Thy1-GCaMP transgenic mice were used in thisstudy. Two-photon microscopy was used for imaging of axonal dieback, blood flow, andcalcium influx post-injury. We found that MP treatment attenuated progressive damageof axons, increased blood flow and reduced calcium influx post-injury. Furthermore,microglia/macrophages accumulated in the lesion site after SCI and expressed theproinflammatory mediators iNOS, MCP-1 and IL-1β. MP treatment markedlyinhibited the accumulation of microglia/macrophages and reduced the expression ofthe proinflammatory mediators. MP treatment also improved the recovery of behavioralfunction post-injury. These findings suggest that MP exerts a neuroprotective effecton SCI treatment by attenuating progressive damage of axons, increasing blood flow,reducing calcium influx and inhibiting the accumulation of microglia/macrophagesafter SCI.