Conditional Deletion of ß1-Integrin in Astroglia Causes Partial Reactive Gliosis
Stefanie Robel, Tetsuji Mori, Saida Zoubaa, Jürgen Schlegel, Svetlana Sirko, Andreas Faissner, Sandra Goebbels, Leda Dimou, Magdalena Götz
Astrocytes play many pivotal roles in the adult brain, including their reaction to injury. A hallmark of astrocytes is the contact of their endfeet with the basement membrane surrounding blood vessels, but still relatively little is known about the signaling mediated at the contact site. Here, we examine the role of ß1-integrin at this interface by its conditional deletion using different Cre lines. Thereby, the protein was reduced only at postnatal stages either in both glia and neurons or specifically only in neurons. Strikingly, only the former resulted in reactive gliosis, with the hallmarks of reactive astrocytes comprising astrocyte hypertrophy and up-regulation of the intermediate filaments GFAP and vimentin as well as pericellular components, such as Tenascin-C and the DSD-1 proteoglycan. In addition, we also observed to a certain degree a non-cell autonomous activation of microglial cells after conditional ß1-integrin deletion. However, these reactive astrocytes did not divide, suggesting that the loss of ß1-integrin-mediated signaling is not sufficient to elicit proliferation of these cells as observed after brain injury. Interestingly, this partial reactive gliosis appeared in the absence of cell death and blood brain barrier disturbances. As these effects did not appear after neuron-specific deletion of b1-integrin, we conclude that b1-integrin-mediated signaling in astrocytes is required to promote their acquisition of a mature, nonreactive state. Alterations in ß1-integrin-mediated signaling may hence be implicated in eliciting specific aspects of reactive gliosis after injury.