Altered functional connectivity between primary motor cortex subregions and the whole brain in patients with incomplete cervical spinal cord injury

Transcranial direct current stimulation combined with swimming exercise improves the learning and memory abilities of vascular dementia rats by regulating microglia through miR-223-3p/PRMT8

BACKGROUND

Vascular dementia (VD) is the second most common type of dementia worldwide. Previous studies have proven that transcranial direct current stimulation (tDCS) has potential applications in relieving cognitive impairment in VD animal models. The purpose of this study was to probe the mechanism by which tDCS combined with swimming exercise improves the learning and memory abilities of VD model rats.

METHOD

The VD rat model was induced using the permanent bilateral common carotid artery occlusion (2-VO) method; tDCS was applied to the rats and then they took part in swimming exercises. Rat memory, platform crossing time, and platform crossing frequency were analyzed via a water maze experiment. Nerve damage in the cortex and hippocampal CA1 area of the rats was observed using Nissl staining. Western blotting, immunohistochemistry, immunofluorescence staining and reverse transcription quantitative polymerase chain reaction (RT - qPCR) were used to determine the expression of related proteins and genes. The levels of oxidative stress were detected by kits.

RESULTS

We demonstrated that VD model rats treated with tDCS combined with swimming exercise exhibited significant improvement in memory, and VD model rats exhibited significantly reduced neuronal loss in the hippocampus, and reduced microglial activation and M1 polarization. tDCS combined with swimming exercise protects VD model rats from oxidative stress through the miR-223-3p/protein arginine methyltransferase 8 (PRMT8) axis and inhibits the activation of the TLR4/NF-κB signaling pathway.

CONCLUSION

Our results suggest that tDCS combined with swimming exercise improved the learning and memory ability of VD model rats by regulating the expression of PRMT8 through miR-223-3p to affect microglial activation and M1 polarization.

Brain region changes following a spinal cord injury

Brain-related complications are common in clinical practice after spinal cord injury (SCI); however, the molecular mechanisms of these complications are still unclear. Here, we reviewed the changes in the brain regions caused by SCI from three perspectives: imaging, molecular analysis, and electrophysiology. Imaging studies revealed abnormal functional connectivity, gray matter volume atrophy, and metabolic abnormalities in brain regions after SCI, leading to changes in the structure and function of brain regions. At the molecular level, chemokines, inflammatory factors, and damage-associated molecular patterns produced in the injured area were retrogradely transmitted through the corticospinal tract, cerebrospinal fluid, or blood circulation to the specific brain area to cause pathologic changes. Electrophysiologic recordings also suggested abnormal changes in brain electrical activity after SCI. Transcranial magnetic stimulation, transcranial direct current stimulation, and deep brain stimulation alleviated pain and improved motor function in patients with SCI; therefore, transcranial therapy may be a new strategy for the treatment of patients with SCI.

A shift of brain network hub after spinal cord injury

Background

Spinal cord injury (SCI) causes severe sequelae and significant social loss, depending on the extent of the damage. Most previous studies have focused on the pathology of the spinal cord to develop treatments for SCI. However, it is now known that the brain, which is not directly damaged, also undergoes morphological changes after spinal cord injury, which could affect natural recovery and treatment. In recent years, magnetic resonance imaging (MRI) has been developed to analyze functional changes in the brain. Resting-state functional MRI (rsfMRI), which captures brain activity at rest, can calculate functional connections between brain areas and identify central hubs by network analysis.

Purpose

We aim to investigate functional connectivity in the brain using rsfMRI after SCI and to determine how brain-network main hubs change over time.

Methods

We evaluated rsfMRI in 10 mice of the contusional SCI model and calculated connectivity using graph theory. We evaluated "centrality," a representative parameter of network analysis. The subtype of centrality was degree centrality, which indicates the hub function of a single area. The five times of rsfMRI were performed in each individual mouse: before injury and at 1, 3, 7, and 14 weeks post-injury.

Results

Before the injury, the degree centralities of the primary and secondary motor cortex were high, suggesting that these motor cortices served as main hubs for motor function. After SCI, the hub function of the motor cortices decreased by 14 weeks. In contrast, hub function in the external capsule and the putamen comparatively increased with time after injury, suggesting that the extrapyramidal/subcortical system, which runs the ventral side of the spinal cord and remains after injury in this model, becomes dominant.

Conclusion

We demonstrated the shift of the brain network hub after SCI. The results of this study provide basic information for understanding brain network changes after SCI and would be useful for treatment selection and evaluation of its efficacy in SCI patients.