The Effect of Stereotactic Injections on Demyelination and Remyelination: a Study in the Cuprizone Model

Abstract

Remyelination is the natural repair mechanism in demyelinating disorders of the central nervous system (CNS) such as multiple sclerosis. Several animal models have been used to study demyelination and remyelination. Among toxic animal models, oral administration of the toxin cuprizone leads to white and gray matter demyelination. In contrast, focal demyelination models include the stereotactic application of a toxin such as lysolecithin or ethidium bromide. The injection procedure generates a local disruption of the blood-brain barrier (BBB) and might thus trigger a local inflammatory reaction and consequently may influence demyelination and remyelination. In order to study such consequences, we applied stereotactic injections in the cuprizone model where demyelination and remyelination are mediated independent of this procedure. Immunohistochemistry was performed to detect the presence of lymphocytes and activated glial cells in the injection area. Blood protein stainings were used to assess the integrity of the BBB and myelin staining to evaluate demyelination and remyelination processes. Stereotactic injection led to a local disruption of the BBB as shown by local extravasation of blood proteins. Along the injection canal, T and B lymphocytes could be detected and there was a tendency of a higher microgliosis and astrocytosis. However, these changes did not influence demyelination and remyelination processes at the site of injection, in the corpus callosum, or in the cerebral cortex. Our results suggest that a local stereotactic injection has no major impact on CNS demyelination and remyelination.

CD8 T-cell Recruitment Into the Central Nervous System of Cuprizone-Fed Mice: Relevance to Modeling the Etiology of Multiple Sclerosis

“…Notably, the CD8 signal was also detected in brain and spinal cord tissue by western blot analysis when Cx was combined with 0.1% CPZ and PT. This preferential increase in CD8 levels was not observed in previous CPZ-feeding studies that did not include strategies to protect the peripheral immune system (Remington et al, 2007;Partridge et al, 2016;Traka et al, 2016;Tejedor et al, 2017;Sen et al, 2019a) or which the focus of analysis was on a pan T-cell marker (CD3; Caprariello et al, 2018). While it has been argued that ''cellular sources of CD8 were reactive macrophages/microglia'' (Zhang et al, 2009), here, double labeling of the brain and spinal cord sections with IBA 1 and CD8 showed distinct microglia and CD8 cell populations.…”

“…Furthermore, western blot analysis confirmed that Cx countered all CPZ-induced suppression of CD4/8 signal in the thymus and spleen. In the absence of the protective effects of Cx, the direct effects of CPZ-feeding on the thymus and spleen provide a plausible explanation as to why prior studies did not show the involvement of T-cells in the CNS of CPZ-fed mice (Remington et al, 2007;Tejedor et al, 2017;Sen et al, 2019a). Likewise, the demonstration that CPZ ameliorates and/or prevents the clinical and pathological features of EAE and Theiler's virus FIGURE 7 | Detection of CD4/8 signals in the CNS homogenate.…”

“…While there have been numerous reports of CPZ being used to study demyelination, these have not established the involvement of peripheral T-cells at the sites of CPZ-induced demyelination in the CNS (Remington et al, 2007;Partridge et al, 2016;Traka et al, 2016;Tejedor et al, 2017;Sen et al, 2019a). It was thought that as CPZ does not induce a breach of the blood-brain barrier (BBB), T-cells have no access to the CNS (Remington et al, 2007;Skripuletz et al, 2011;Tejedor et al, 2017). However, even when the BBB was breached using pertussis toxin (PT), CPZ evoked marked CNS demyelination, gliosis and changes in the abundance of proteoforms involved in metabolism, immune and synaptic functions, without detectable T-cell infiltration (Sen et al, 2019a).…”

Revisiting the Pathoetiology of Multiple Sclerosis: Has the Tail Been Wagging the Mouse?

“…Despite the marked CNS oligodendrocytosis, demyelination, and gliosis in CPZ-fed mice, no involvement of adaptive immune cells in the CNS lesions was found (82, 86). However, T-cell infiltration into the CNS was not evident even when the BBB was disrupted by injection of ethidium bromide, lysolecithin (86), or pertussis toxin (82). This indicated the presence of an alternative mechanism(s) in the adaptive immune cell response in the CPZ model, independent of BBB integrity or the lymphatic system.…”

Protein Nanoparticle Osmotic Pressure Modifies Nonselective Permeability of the Blood Brain Barrier by Increasing Membrane Fluidity

“…In order to clarify the role of intracellular PN in BBB permeability in vivo, MF and MT stabilizers were used to restore intracellular PN levels in an adult male SD rat BBB lesion model; the schematic diagram of the experiment is shown in Fig. 7A [31,32] . The SD rats were injected with Evans Blue (EB).…”