Progression of reactive gliosis and astroglial phenotypic changes following stab wound‐induced traumatic brain injury in mice

Abstract

Astrocytes are the main homeostatic cells in the central nervous system (CNS) and they have an essential role in preserving neuronal physiology. After brain injury, astrocytes become reactive, and that involves a profound change in the astroglial gene expression program as well as intense cytoskeleton remodeling that has been classically shown by the up‐regulation of glial fibrillary acidic protein (GFAP), a pan‐reactive gene over‐expressed in reactive astrocytes, independently of the type of injury. Using the stab wound rodent model of penetrating traumatic injury in the cortex, we here studied the reactive astroglial morphology and reactive microgliosis in detail at 1, 3, 7, 14, and 28 days post‐injury (dpi). By combining immunohistochemistry, morphometrical parameters, and Sholl analysis, we segmented the astroglial cell population into clusters of reactive astrocytes that were localized in the core, penumbra, and distal regions of the stab wound. Specifically, highly reactive clusters with more complex morphology, increased C3, decreased aquaporin‐4 (AQP4), and glutamine synthetase (GS) expression, were enriched at 7 dpi when behavioral alterations, microgliosis, and neuronal alterations in injured mice were most significant. While pro‐inflammatory gain of function with peripheral lipopolysaccharide (LPS) administration immediately after a stab wound expanded these highly reactive astroglial clusters, the treatment with the NF‐κB inhibitor sulfasalazine reduced the abundance of this highly reactive cluster. Increased neuronal loss and exacerbated reactive microgliosis at 7 dpi were associated with the expansion of the highly reactive astroglial cluster. We conclude that highly reactive astrocytes found in stab wound injury, but expanded in pro‐inflammatory conditions, are a population of astrocytes that become engaged in pathological remodeling with a pro‐inflammatory gain of function and loss of homeostatic capacity. Controlling this astroglial population may be a tempting strategy to reduce neuronal loss and neuroinflammation in the injured brain.image

Amyloid precursor protein induces reactive astrogliosis

“…To examine whether our findings apply to realistic pathological contexts, we preliminarily build upon previous work in animal models of brain trauma. 22,[64][65][66][67] These previous studies, however, did not show the interaction between APP and IFN in reactive astrocytes revealed by the present study. In the attempt to translate our cell culture findings into pathophysiologically relevant animal models, we explored and observed an association between APP and IFN levels in reactive astrocytes affected by TBI.…”

“…Conversely, depletion of APP abrogates LPS‐induced reactive astrogliosis and reduces expression of ISG products. To examine whether our findings apply to realistic pathological contexts, we preliminarily build upon previous work in animal models of brain trauma 22,64–67 . These previous studies, however, did not show the interaction between APP and IFN in reactive astrocytes revealed by the present study.…”

Amyloid precursor protein induces reactive astrogliosis

“…To examine whether our findings apply to realistic pathological contexts, we build upon previous work in animal models of brain trauma 22,[64][65][66][67] . These previous studies, however, did not show the interaction between APP and IFN in reactive astrocytes revealed by the present study.…”