Abstract
To identify cellular and molecular gradients following spinal cord injury (SCI), a rat contusion model of severe SCI was used to investigate the expression of NG2 and molecules that identify astrocytes and axons of the ventral horns (VH) at different distances on 7 and 30 days post-injury (dpi). A gradient of expression of NG2+/Olig2+ cells was determined, with the highest concentrations focused close to the injury site. A decrease in NG2 mean intensity correlates with a decrease in the number of NG2+ cells more distally. Immunoelectron microscopy subsequently revealed the presence of NG2 in connection with the membrane and within the cytoplasm of NG2+ glial cells and in large amounts within myelin membranes. Analysis of the astrocyte marker GFAP showed increased expression local to injury site from 7 dpi, this increase in expression spread more distally from the injury site by 30 dpi. Paradoxically, astrocyte perisynaptic processes marker GLT-1 was only increased in expression in areas remote from the epicenter, which was traced both at 7 and 30 dpi. Confocal microscopy showed a significant decrease in the number of 5-HT+ axons at a distance from the epicenter in the caudal direction, which is consistent with a decrease in β3-tubulin in these areas. The results indicate significant cellular and molecular reactions not only in the area of the gray matter damage but also in adjacent and remote areas, which is important for assessing the possibility of long-distance axonal growth.
Highlights
Research that studies the cellular and molecular mechanisms in spinal cord injury has mainly focused on analyzing the injury area
In the ventral horns (VH), the number of neuron-glial antigen 2 (NG2)−/Olig2+ cells not expressing NG2 proteoglycan was more than 15 times higher than the number of NG2+/Olig2+ cells in all studied groups in the corresponding zones (Figures 1E,F)
We focused on the analysis of the ventral horns in the perilesional area along the rostrocaudal axis because of the importance of cellular and molecular shifts in this region for the restoration of locomotor function
Summary
Research that studies the cellular and molecular mechanisms in spinal cord injury has mainly focused on analyzing the injury area. Spatiotemporal experimental analysis of the gray and white matter of the spinal cord at a distance from the epicenter of injury shows the differential pattern and severity of pathological reactions, gene expression, and molecular regulation in the remote rostral and caudal regions (Ek et al, 2010; Yu et al, 2019). The main cause and mechanism of distant reactions, in contrast to shifts in the epicenter of damage, remain poorly understood. This effect in distant regions seems to be important to take into account to assess the prospects for outcomes in pathology
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