The ependymal cell cytoskeleton in the normal and injured spinal cord of mice.

The cytoskeleton of ependymal cells is fundamental to organize and maintain the normal architecture of the central canal (CC). However, little is known about the plasticity of cytoskeletal components after spinal cord injury. Here, we focus on the structural organization of the cytoskeleton of ependymal cells in the normal and injured spinal cord of mice (both females and males) using immunohistochemical and electron microscopy techniques. We found that in uninjured animals, the actin cytoskeleton (as revealed by phalloidin staining) was arranged following the typical pattern of polarized epithelial cells with conspicuous actin pools located in the apical domain of ependymal cells. Transmission electron microscopy images showed microvilli tufts, long cilia, and characteristic intercellular membrane specializations. After spinal cord injury, F-actin rearrangements paralleled by fine structural modifications of the apical domain of ependymal cells were observed. These changes involved disruptions of the apical actin pools as well as fine structural modifications of the microvilli tufts. When comparing the control and injured spinal cords, we also found modifications in the expression of vimentin and glial fibrillary acidic protein (GFAP). After injury, vimentin expression disappeared from the most apical domains of ependymal cells but the number of GFAP-expressing cells within the CC increased. As in other polarized epithelia, the plastic changes in the cytoskeleton may be critically involved in the reaction of ependymal cells following a traumatic injury of the spinal cord.

Change in phospholipid species of retinal layer in traumatic optic neuropathy model.

Injured optic nerves induce death in almost all retinal ganglion cells (RGC) and cause a loss of axons. To date, we have studied injured RGC axon regeneration by using a traumatic optic nerve injury (TONI) rodent model, and we revealed that axonal regeneration is induced by the graft of an autologous peripheral nerve. The efficient approach to the regeneration of axons thus needs an environmental adjustment of RGC. However, the RGC environment induced by TONI remains unknown. Here, we analyzed female and male C57BL/6 mouse retinal tissue alterations in detail after TONI and focused on the major phospholipid species that are enriched in the whole retina. Reactive astrocyte accumulation, glia scar formation, and demyelination were observed in the injured optic nerve area, while RGC cell death, astrocyte accumulation, and Glial fibrillary acidic protein (GFAP) positive Müller cell increases were detected in the retinal layer. Furthermore, phosphatidylinositol (PI) 18:0/20:4 was localized to three nuclear layer structures: the ganglion cell layer (GCL), the inner nuclear layer (INL), and the outer nuclear layer (ONL) in control retina; however, the localization of 18:0/20:4 PI in TONI was disturbed. Meanwhile, phosphatidylserine (PS) 18:0/22:6 showed that the expression was specifically in the inner plexiform layer (IPL) with similar signal intensity in both cases. Other PS species and phosphatidylethanolamine (PE) were differentially localized in the retinal layer; however, the expressions of PE including docosahexaenoic acid (DHA) were affected by TONI. These results suggest that not only GCL but also other retinal layers were influenced by TONI.

Mild carotid stenosis creates gradual, progressive, lifelong brain, and eye damage: An experimental laboratory rat model.

In humans, carotid stenosis of 70% and above might be the cause of clinical symptoms such as transient ischemic attack and stroke. No clinical or animal studies have evaluated mild carotid occlusion, and few examined unilateral occlusion. Here, Westar rats underwent bilateral or unilateral carotid occlusion of 28-45%. Long-term effects were evaluated 9-11 months later. We conducted cognitive evaluation using spatial learning in a water maze and exploration behavior in an open field. Morphology of the brain was examined by MRI using diffusion-tensor imaging (DTI) and immunohistochemistry staining of the brain and eyes. Cognitive deficit was found in spatial memory and exploration behavior in both occluded groups. Brain and eyes histology presented severe damage in the bilateral group, compared to the unilateral one. DTI revealed an increase in mean diffusivity (MD) in the ventral thalamus and a decrease in fractional anisotropy in optic nerve and optic tract in bilateral rats, while unilateral rats showed only an increase in MD in the ventral pons. In those areas, a significant change in astrocytes, microglia, and number of apoptotic cells were found. Bilateral occlusion produced severe damage to both retinas, while unilateral occlusion produced damage mainly in the occluded side. We found that mild carotid stenosis, even in a unilateral occlusion, creates behavioral abnormalities presented by brain and eye histopathology. The results support our hypothesis that gradual formation of mild carotid stenosis along the life course leads to progressive damage that may create different degenerative diseases at a later age.

Brn3a and Brn3b knockout mice display unvaried retinal fine structure despite major morphological and numerical alterations of ganglion cells.

Ganglion cells (GCs), the retinal output neurons, receive synaptic inputs from bipolar and amacrine cells in the inner plexiform layer (IPL) and send information to the brain nuclei via the optic nerve. Although GCs constitute less than 1% of the total retinal cells, they occur in numerous types and are the first neurons formed during retinal development. Using Brn3a and Brn3b mutant mice in which the alkaline phosphatase gene was knocked-in (Badea et al. [Neuron] 2009;61:852-864; Badea and Nathans [Vision Res] 2011;51:269-279), we studied the general effects after gene removal on the retinal neuropil together with the consequences of lack of development of large numbers of GCs onto the remaining retinal neurons of the same class. We analyzed the morphology, number, and general architecture of various neuronal types presynaptic to GCs, searching for changes secondary to the decrement in the number of their postsynaptic partners, as well as the morphology and distribution of retinal astrocytes, for their strong topographical relation to GCs. We found that, despite GC losses, retinal organization in Brn3 null mice is remarkably similar to that of wild-type controls. J. Comp. Neurol. 527:187-211, 2019. © 2016 Wiley Periodicals, Inc.