Diverged morphology changes of astrocytic and neuronal primary cilia under reactive insults

Abstract

Primary cilia are centriole-derived sensory organelles that are present in most mammalian cells, including astrocytes and neurons. Evidence is emerging that astrocyte and neuronal primary cilia demonstrate a dichotomy in the mature mouse brain. However, it is unknown how astrocytic and neuronal primary cilia change their morphology and ciliary proteins when exposed to reactive insults including epilepsy and traumatic brain injury. We used a double transgenic mouse strain (Arl13b-mCherry; Centrin2-GFP), in which we found spontaneous seizures, and a cortical injury model to examine the morphological changes of astrocytic and neuronal primary cilia under reactive conditions. Transgenic overexpression of Arl13b drastically increases the length of astrocytic and neuronal primary cilia in the hippocampus, as well as the cilia lengths of cultured astrocytes and neurons. Spontaneous seizures shorten Arl13b-positive astrocytic cilia and AC3-positive neuronal cilia in the hippocampus. In a cortical injury model, Arl13b is not detectable in primary cilia, but Arl13b protein relocates to the cell body and has robust expression in the proximity of injured tissues. In contrast, the number of AC3-positive cilia near injured tissues remains unchanged, but their lengths become shorter. These results on astrocytic cilia implicate Arl13b in regulating astrocyte proliferation and tissue regeneration, while the shortening of AC3-positive cilia suggests adaptive changes of neuronal primary cilia under excitotoxicity.

Response of Astrocytes to Blood Exposure due to Shunt Insertion in vitro

“…These data suggest that there is a potential effect from blood proteins, when added into the media, enhances cell spread and/or cell reactivity. Astrocyte activation occurs in response to stimuli in an effort to repair the brain via proliferation and extension of astrocyte processes [37,38]. Perhaps increased concentration and type of protein adsorbed to the polydimethylsiloxane shunt surface enhances the receptor-integrin interplay and increases cell attachment, not just in cell number, but in cell affinity to the surface (Figure 5).…”

Augmented seizure susceptibility and hippocampal epileptogenesis in a translational mouse model of febrile status epilepticus

“…In the current studies, 4 of 24 mice (16.5%) developed spontaneous seizures, and the duration of these seizures as well as their frequency progressed with time. Whereas only a minority of mice developed epilepsy, this was significantly different than chance, as a robust body of work has demonstrated that spontaneous epileptic activity is not found in control C57BL/6 mice 43–47 . Furthermore, the augmented susceptibility to KA in 56% of mice suggests that pro‐epileptogenic changes were initiated by eFSE in a larger proportion of mice.…”

“…Whereas only a minority of mice developed epilepsy, this was significantly different than chance, as a robust body of work has demonstrated that spontaneous epileptic activity is not found in control C57BL/6 mice. [43][44][45][46][47] Furthermore, the augmented susceptibility to KA in 56% of mice suggests that pro-epileptogenic changes were initiated by eFSE in a larger proportion of mice. Because we employed the C57BL/6 strain, these results are not surprising: It has long been recognized that C57BL/6 mice are resistant to the development of spontaneous seizures after an initial insult such as chemoconvulsant-induced status epilepticus.…”

Response of astrocytes to blood exposure due to shunt insertion in vitro

“…This indicates that the cells expressed on the sides are migrating from the cell layer along the bottom of the well up along the catheter. Astrocyte activation occurs in response to stimuli in an effort to repair the brain via proliferation and extension of astrocyte processes 37,38 . Perhaps increased concentration and type of protein adsorbed to the polydimethylsiloxane shunt surface enhances the receptor‐integrin interplay and increases cell attachment, not just in cell number, but in cell affinity to the surface (Figure 5).…”