Synaptic remodeling in mouse motor cortex after spinal cord injury

Regional brain atrophy in patients with chronic ankle instability: A voxel-based morphometry study

The objective of this study was to investigate whether brain volume changes occur in patients with chronic ankle instability (CAI) using voxel-based morphometry and assessing correlations with clinical tests. Structural magnetic resonance imaging data were prospectively acquired in 24 patients with CAI and 34 healthy controls. CAI symptoms and pain intensity were assessed using the Foot and Ankle Ability Measure (FAAM), Cumberland Ankle Instability Tool (CAIT), American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, and visual analog scale (VAS). The gray matter volume (GMV) of each voxel was compared between the two groups while controlling for age, sex, weight, and education level. Correlation analysis was performed to identify associations between abnormal GMV regions and the FAAM score, AOFAS score, VAS score, disease duration, and body mass index. Patients with CAI exhibited reduced GMV in the right precentral and postcentral areas, right parahippocampal area, left thalamus, left parahippocampal area, and left postcentral area compared to that of healthy controls. Furthermore, the right parahippocampal (r = 0.642, p = 0.001), left parahippocampal (r = 0.486, p = 0.016), and left postcentral areas (r = 0.521, p = 0.009) were positively correlated with disease duration. The left thalamus was positively correlated with the CAIT score and FAAM activities of daily living score (r = 0.463, p = 0.023 and r = 0.561, p = 0.004, respectively). A significant positive correlation was found between the local GMV of the right and left parahippocampal areas (r = 0.487, p = 0.016 and r = 0.763, p < 0.001, respectively) and the AOFAS score. Neural plasticity may occur in the precentral and postcentral areas, parahippocampal area, and thalamus in patients with CAI. The patterns of structural reorganization in patients with CAI may provide useful information on the neuropathological mechanisms of CAI.

Nerve root magnetic stimulation improves locomotor function following spinal cord injury with electrophysiological improvements and cortical synaptic reconstruction

Following a spinal cord injury, there are usually a number of neural pathways that remain intact in the spinal cord. These residual nerve fibers are important, as they could be used to reconstruct the neural circuits that enable motor function. Our group previously designed a novel magnetic stimulation protocol, targeting the motor cortex and the spinal nerve roots, that led to significant improvements in locomotor function in patients with a chronic incomplete spinal cord injury. Here, we investigated how nerve root magnetic stimulation contributes to improved locomotor function using a rat model of spinal cord injury. Rats underwent surgery to clamp the spinal cord at T10; three days later, the rats were treated with repetitive magnetic stimulation (5 Hz, 25 pulses/train, 20 pulse trains) targeting the nerve roots at the L5–L6 vertebrae. The treatment was repeated five times a week over a period of three weeks. We found that the nerve root magnetic stimulation improved the locomotor function and enhanced nerve conduction in the injured spinal cord. In addition, the nerve root magnetic stimulation promoted the recovery of synaptic ultrastructure in the sensorimotor cortex. Overall, the results suggest that nerve root magnetic stimulation may be an effective, noninvasive method for mobilizing the residual spinal cord pathways to promote the recovery of locomotor function.

Comparative study of the reorganization in bilateral motor and sensory cortices after spinal cord hemisection in mice

OBJECTIVE

The effects of spinal cord injury (SCI) on sensorimotor cortex plasticity have not been well studied. Therefore, to explore the reorganization after SCI, we dynamically monitored postsynaptic dendritic spines of pyramidal neurons in vivo.

METHODS

Thy1-YFP transgenic mice were randomly divided into two groups: the control and SCI group. We then opened the spinal vertebral plates of all mice and sectioned one-half of the spinal cord in SCI group. The relevant areas were imaged bilaterally at 0, 3, 14 and 28 days post-SCI. The rates of elimination, formation and stable spines were evaluated.

RESULTS

At the early stage, the rate of stable and elimination spines experienced a similar change trend. But the rate of formation spines in the contralateral sensory cortex was significantly increased after SCI compared with those in the control group. At the late stage, spines of three types remodeled very differently between the sensory and motor cortex. Compared with those in the control group, spines in the bilateral sensory cortex demonstrated obvious differences in the rate of stable and elimination spines but not formation spines, while spines in the motor cortex, especially in the contralateral cortex increased significantly in the rate of formation after SCI. As for survival rate, differences mainly appeared in time frame instead of cortex type or region.

CONCLUSIONS

The dendritic spines in hindlimb representation area of the sensorimotor cortex experienced bilaterally remodeling after SCI. And those spines in the sensory and motor cortex experienced great but different change trends after SCI.