Characterization of a novel, chronic inflammatory response following spinal cord injury with flow cytometry (B67)

Abstract

Abstract Traumatic spinal cord injury results in a breakdown of the blood brain barrier allowing inflammatory cells to enter the cord, potentially mediating both damage and repair. Several studies have described the acute cellular inflammatory response, however our study quantifies inflammatory cells up to 90 days post injury, revealing a previously uncharacterized chronic inflammatory phase. We developed a rapid, debris-minimizing flow cytometry method, allowing for accurate quantification of cellular inflammation in a defined area of the injured spinal cord. We validated the technique by confirming its ability to distinguish differences in cellular inflammation between mild, moderate, and severe injuries. Using this method, we quantified inflammatory cells in segments T8-T10 following a 200 kd contusion injury to T9 in female Sprague-Dawley rats. We confirm and expand upon the published timecourse for both neutrophil and macrophage/microglial infiltration of the injured spinal cord by assaying daily for the first 10 days post injury and over wider intervals up to 90 days post injury. Interestingly, we were able to detect novel chronic inflammation months after injury, with the number of macrophages at 60 days exceeding that at 7 days, the previously published peak of activity. Further experimentation is needed to test whether the chronic inflammatory response aids remyelination or regeneration of damaged axons.