Two-photon Excited Fluorescence Microscopy As A Tool To Investigate The Efficacy Of Methylprednisolone In A Mouse Spinal Cord Injury Model

Objective: To explore the method of using two photon microscopy to evaluate thetherapeutic effect of methylprednisolone in spinal cord injuried mouse. Methods:adult male YFP-H line (n=18) and CX3CR1-GFP (n=18) transgenic fluorescent mice,ranging from23to25g in weight, were randomly divided into three groups, shamgroup (Group A), spinal cord injury group (Group B), MP treatment group (Group C).Group A received laminectomy only. Compression SCI model was produced in groupB and C by placing a20g weight platform for5min. Group B received saline at0.5h,8h,24h post-injury. Group C received MP (30mg/kg) intravenously at0.5h,8h,24hpost-injury. BMS score was used to evaluate spinal cord function during7dpost-injury. Two-photon microscopy was used in vivo imaging of axons at the timepoint of0.5h,24h,48h,72h post-injury. Results: At4days after injury, there were noankle movement in group B and C, and no significant difference in the BMS scorewas found among group B and C(P>0.05).After4days post-injury, slight anklemovement was observed in both group B and C. At7days after injury, frequent dorsal stepping and occasional plantar stepping was observe in group C, and there was slightankle movement in group B, the BMS score of group C was significantly higher thangroup B (P<0.05).The axon count in group A remained1in all time point. The axoncount in group B and C reduced in48h post-injury, the axon count in group C washigher than group B in72h post-injury(P<0.05). Histology showed that group C hadmilder damage than group B after injury. Group C was lower inmicroglia/macrophage proliferation than group B. Conclusion: MP therapy in acuteSCI has neuroprotective effect in alleviating axonal progressive damage and reducingthe microglia/macrophage proliferation in SCI.