Contribution of Notch/Wnt signaling modulation in reactive astrocyte reparative response after brain injury

Abstract

After a Traumatic Brain Injury (TBI), the neural network activates a reparative response seeking to restore homeostasis. Astrocyte reactivation is an essential component of this response. The injury creates a temporal microenvironment where neurogenic signaling molecules regulate cell fate decisions of neocortical neural progenitors. Likewise, astrocyte reactivation triggers a transcriptional-proliferative program where neurogenic signaling molecules play crucial roles. However, precise molecular mechanisms are context-specific and are not fully understood. Here we studied cellular and molecular aspects of reactive astrocytes response after Notch-Wnt neurogenic signaling modulation. Our results provide new evidence of cortical Notch-Wnt signaling activation after TBI. Reactive astrocytes in the core of Notch signaling showed a differential aggregated distribution. In vitro, Notch inhibition promoted a neural precursor profile and might increase the number of cells committed in a proliferative response. Finally, we found an indirect co-regulation of Wnt-Shh signaling in BHLH-Notch target genes and a Notch-supportive effect in Wnt-Shh signaling activation.

Mechanobiological Modulation of In Vitro Astrocyte Reactivity Using Variable Gel Stiffness

“…Astrocyte proliferation in response to brain damage correlates with the severity and proximity to the “core″. At the peripheral “pericontusional” region of the lesion (between 150 and 400 μm) or in minor injuries, glial cells display a mild reactivity, with a limited number of GFAP + cells reacquiring a proliferative phenotype. ,,,− In contrast, at the “core” or in situations involving severe injuries such as traumatic wounds, hypoxia, inflammations, infectious diseases, and neurodegenerative conditions, both GFAP level proliferation rate increases .…”

“…At the peripheral “pericontusional” region of the lesion (between 150 and 400 μm) or in minor injuries, glial cells display a mild reactivity, with a limited number of GFAP + cells reacquiring a proliferative phenotype. 2 , 26 , 68 , 83 − 85 In contrast, at the “core” or in situations involving severe injuries such as traumatic wounds, hypoxia, inflammations, infectious diseases, and neurodegenerative conditions, both GFAP level proliferation rate increases. 65 In vitro , the baseline proliferation rate of astrocytes cultured on a traditional culture system (glass) is 5%.…”

“…The primary culture of astrocyte was adapted from Yang’s protocol, previously established in our lab. , Briefly, we euthanized neonatal (P1) C57BL/6j mice by decapitation. Brain cortices were placed in HBSS solution (ThermoFisher, Boston, MA, USA), and meninges were removed.…”