PLX5622 Efficacy on Microglia Depletion and Its Impact on Functional Recovery Following Unilateral Dorsal Quadrant C4 Cervical Spinal Cord Injury in Female Lewis Rats

STUDY PURPOSE: After spinal cord injury (SCI), microglia play a key role in the inflammatory response. Beyond its impact on tissue damage, inflammation has also been linked to adaptive and maladaptive plasticity. In this study, we aimed to evaluate the impact of depleting microglia following SCI in rats with unilateral incomplete cervical SCI using PLX5622. Initially, we aimed to evaluate the efficacy of PLX5622 in depleting microglia within the central nervous system of rats with SCI, followed by assessing the impact of microglial reduction on functionality in this model. DATA COLLECTED: This experiment involved 14 age-matched adult female Lewis rats, 10–12 weeks old, divided equally into two groups (n=7 per group). Sensorimotor and behavioral assessments were performed before SCI induction, including the Open Field, Elevated Plus Maze, and Light-Dark Box tests. All rats received a C4 dorsolateral quadrant transection. Following a recovery period of 7 days, one group of rats was fed a diet containing PLX5622, a colony-stimulating factor 1 receptor inhibitor for microglia/macrophages, at 1200 ppm for 30 days. All behavioral tests were repeated during the PLX5622 treatment. At the end of the PLX administration, the rats were euthanized and perfused, and their brains, spinal cord, and liver tissues were harvested for further evaluation. Video analysis of the rats' behaviors was performed using customized programs developed in Python. To test the efficacy of PLX5622 on microglia depletion and morphology, tissue samples from the cingulate cortex, hypothalamus, and striatum, as well as the grey and white matter from the C1 segment and the lesion site C4, were processed. Additionally, the left liver lobe was collected to examine liver-resident macrophages (Kupffer cells) and evaluate the specificity of PLX5622-induced microglial depletion. Microglial and Kupffer cell quantification was performed using QuPath and ImageJ-Fiji. Morphological analysis of microglia was conducted with ImageJ-Fiji, and 3D microglial reconstructions in the regions of interest were performed using Imaris software. To assess the extent of SCI damage, the injured and spared areas within the spinal cord were measured using ImageJ-Fiji, along with the thickness of the scar tissue in the lesion core. DATA USAGE NOTES: