Understanding the Role of the Glial Scar through the Depletion of Glial Cells after Spinal Cord Injury

Spinal cord injury (SCI) is a condition that affects between 8.8 and 246 people in a million and, unlike many other neurological disorders, it affects mostly young people, causing deficits in sensory, motor, and autonomic functions. Promoting regrowth of axons is one of the most important goals for the neurological recovery of patients after SCI, but it is also one of the most challenging goals. A key event after SCI is the formation of a glial scar around the lesion core, which is mainly comprised of astrocytes, NG2+-glia, and microglia. Traditionally, the glial scar has been regarded as detrimental for recovery because it may act as a physical barrier for axon regrowth and release various inhibitory factors. However, more and more evidence now suggest that the glial scar is beneficial for the surrounding spared tissue after SCI. Here, we review experimental studies that used genetic and pharmacological approaches to ablate specific populations of glial cells in rodent models of SCI, in order to understand their functional role. The studies showed that ablation of either astrocytes, NG2+-glia or microglia may result in disorganization of glial scar, increased inflammation, extended tissue degeneration and impaired recovery after SCI. Hence, glial cells and glial scar appear as important beneficial players after SCI.