The effect of irradiation and methylprednisolone in spinal cord injured rats

Granulocyte Colony-Stimulating Factor Combined with Methylprednisolone Improves Functional Outcomes in Rats with Experimental Acute Spinal Cord Injury

OBJECTIVES

To evaluate the effects of combined treatment with granulocyte colony-stimulating factor (G-CSF) and methylprednisolone in rats subjected to experimental spinal cord injury.

METHODS

Forty Wistar rats received a moderate spinal cord injury and were divided into four groups: control (no treatment); G-CSF (G-CSF at the time of injury and daily over the next five days); methylprednisolone (methylprednisolone for 24 h); and G-CSF/Methylprednisolone (methylprednisolone for 24 h and G-CSF at the time of injury and daily over the next five days). Functional evaluation was performed using the Basso, Beattie and Bresnahan score on days 2, 7, 14, 21, 28, 35 and 42 following injury. Motor-evoked potentials were evaluated. Histological examination of the spinal cord lesion was performed immediately after euthanasia on day 42.

RESULTS

Eight animals were excluded (2 from each group) due to infection, a normal Basso, Beattie and Bresnahan score at their first evaluation, or autophagy, and 32 were evaluated. The combination of methylprednisolone and G-CSF promoted greater functional improvement than methylprednisolone or G-CSF alone (p<0.001). This combination also exhibited a synergistic effect, with improvements in hyperemia and cellular infiltration at the injury site (p<0.001). The groups displayed no neurophysiological differences (latency p=0.85; amplitude p=0.75).

CONCLUSION

Methylprednisolone plus G-CSF promotes functional and histological improvements superior to those achieved by either of these drugs alone when treating spinal cord contusion injuries in rats. Combining the two drugs did have a synergistic effect.

X-ray therapy promotes structural regeneration after spinal cord injury in a rat model

Objective

This study aims to investigate the therapeutic effects and mechanisms of x-ray treatment on rats following spinal cord injury (SCI).

Methods

Forty-six female Sprague–Dawley rats were subjected to spinal cord injury using the modified Allen weight-drop method. The animals were randomly divided into six groups. Two of the animal groups were irradiated with 10 Gy at the lesion site; another two groups were irradiated with 20 Gy; and the last two groups without irradiation were regarded as the sham group. One of the each of two animal groups was euthanized at different time points at 4 and 12 weeks, respectively, after irradiation. Spinal cord calluses were assessed using kinology and electrophysiology and histology methods.

Results

In all of the groups, the neurofilament (NF) counts at 14 weeks were found to be higher than that at 6 weeks after SCI. Both 10-Gy irradiated and 20-Gy irradiated groups were higher than those of the sham group at each time point (P < 0.05). The myelin basic protein (MBP) count decreased at 14 weeks after SCI in the irradiated groups (P < 0.05) but increased at 14 weeks in the sham group (P < 0.05). Furthermore, the MBP count of the irradiated groups was lower than that of the sham group at 14 weeks (P < 0.05). The glial fibrillary acidic protein (GFAP) and Nogo-A counts at 14 weeks were higher than those at 6 weeks in all the groups (P < 0.05), and there was no statistical significance with kinology and electrophysiology tests in all groups.

Conclusions

A self-repair mechanism exists after spinal cord injury, which lasts at least 14 weeks. X-ray therapy promotes the regeneration of the spinal cord system after injury.

Two-photon microscopy as a tool to investigate the therapeutic time window of methylprednisolone in a mouse spinal cord injury model

PURPOSE

The aim of the present study was to explore the use of two-photon microscopy for investigating the therapeutic time window of methylprednisolone (MP) treatment after spinal cord injury (SCI).

METHODS

Twenty-four YFP H-line mice were subjected to hemisection SCI and then divided into four groups. Group 1 received MP at 30 min post-injury; group 2 received MP at 8 h post-injury; group 3 received MP at 24 h post-injury; and group 4 received saline at 30 min post-injury. Post-injury axonal dieback was imaged in vivo using two-photon microscopy. After all imaging sessions, histological examination of the surviving neurons and microglial/macrophage accumulation was performed.

RESULTS

Two-photon imaging revealed the degree of progressive axon damage after SCI. Group 1 exhibited a shorter axonal dieback distance and slower axonal dieback speed than groups 2, 3, and 4 (p < 0.01). MAP-2 staining revealed greater neuronal survival in group 1 than in groups 2, 3, and 4 (p < 0.05). F4/80 staining revealed greater microglial/macrophage density in groups 2, 3, and 4 than in group 1 (p< 0.05).

CONCLUSIONS

MP therapy may help attenuate progressive axon damage, reduce neuronal death, and inhibit microglial/macrophage accumulation, especially when initiated shortly after SCI.

Two-photon-excited fluorescence microscopy as a tool to investigate the efficacy of methylprednisolone in a mouse spinal cord injury model

STUDY DESIGN

Basic imaging experiment.

OBJECTIVE

To explore the use of 2-photon-excited fluorescence (2PEF) microscopy to investigate the therapeutic effect of methylprednisolone (MP) in mice with spinal cord injury (SCI).

SUMMARY OF BACKGROUND DATA

MP can alleviate secondary SCI through its anti-inflammatory effect; however, how MP regulates axonal dynamics in a compression SCI model is not well characterized. We used 2PEF microscopy to trace axonal dynamics in vivo during MP therapy.

METHODS

Two types of transgenic mice (weighing 23-25 g) including YFP-H line (n = 18) and CX3CR1-GFP (n = 18) were used for experimental procedure. Each type of mouse was randomly divided into 3 groups, and the sample size of every subgroup was 6. The sham groups including YFP-H line group (n = 6) and CX3CR1-GFP group (n = 6) received laminectomy only (group 1). SCI groups received saline treatment (group 2) and SCI groups received MP treatment (group 3). Hind limb motor function was evaluated using the Basso Mouse Scale. 2PEF microscopy was used to image in vivo axonal dynamics at baseline and at 0.5 hours, 24 hours, 48 hours, and 72 hours postinjury. Histology was employed to examine pathological changes and microglial/macrophage proliferation after all imaging sessions.

RESULTS

Group 1 exhibited no significant differences in hind limb motor function before versus after surgery. The Basso Mouse Scale scores were significantly lower in groups 2 and 3 than in group 1 (P < 0.05). Degree of recovery was higher in group 3 than in group 2 at 7 days postinjury (P < 0.05). The axons in group 1 remained intact at all time points. The survival rate of axons in groups 2 and 3 progressively decreased at 48 hours postinjury; at 72 hours postinjury, the axon survival rate was higher in group 3 than group 2 (P < 0.05). Histology revealed that group 3 presented milder damage in injured spinal cord than group 2. Microglial/macrophage proliferation was lower in group 3 than in group 2 (P < 0.05).

CONCLUSION

2PEF microscopy is useful for detecting early changes, indicating axonal disruption in compression SCI. MP therapy may help alleviate axonal progressive damage and reduce the proliferation of microglia/macrophages in acute SCI.

LEVEL OF EVIDENCE

N/A.