The effect of microglial ablation and mesenchymal stem cell transplantation on a cuprizone‐induced demyelination model

Abstract

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system with symptoms such as neuroinflammation, astrocytosis, microgliosis, and axonal degeneration. Mesenchymal stem cells (MSCs) with their immunomodulation, differentiation, and neuroprotection abilities can influence the remyelination process. The goal of this study is to investigate the impact of microglial ablation and MSCs transplantation on remyelination processes in the corpus callosum (CC) of the cuprizone demyelination model. For the induction of a chronic demyelination model, C57BL6 mice were fed with chow containing 0.2% cuprizone (wt/wt) for 12 weeks. For the depletion of microglia, PLX3397 was used as a colony‐stimulating factor 1 receptor inhibitor for 21 days. MSCs were injected to the right lateral ventricle and after 2 weeks, the mice were killed. We assessed glial cells using specific markers such as APC, Iba‐1, and GFAP using the immunohistochemistry method. Remyelination was evaluated by Luxol fast blue (LFB) staining and transmission electron microscope (TEM). The specific genes of microglia and MSCs were evaluated by a quantitative real‐time polymerase chain reaction. According to the results of the study, 21 days of PLX3397 treatment significantly reduced microglial cells, and MSCs transplantation decreased the number of astrocytes, whereas the oligodendrocytes population increased significantly in PLX + MSC group in comparison with the cuprizone mice. Furthermore, PLX and MSC treatment elevated levels of remyelination compared with the cuprizone group, as confirmed by LFB staining and TEM analysis. The molecular results showed that MSC transplantation significantly decreased the number of microglia through the CX3CL1/CX3CR1 axis. These results revealed that PLX3397 treatment and MSCs injection reduced microgliosis and astrocytosis. It also increased the oligodendrocytes population by enhancing remyelination in the CC of the cuprizone model of MS.

Effect of CSF1R Inhibitor on Glial Cells Population and Remyelination in The Cuprizone Model

“…Moreover, the results of IF and qRT-PCR showed that PLX3397 administration for 3, 7, 14 and 21 days lead to microglial ablation in the cuprizone model. The data suggest that PLX treatment for 21 days decreased to microglial number to more than 95% compared to the cells in the cuprizone model, but different doses of PLX administration had no effect on astrocytes population, which is similar to the study of Tahmasebi et al (2020) (Tahmasebi et al 2020).…”

“…The cuprizone model is a toxic experimental model (without an autoimmune component) with pathogenesis comparable to MS (Kipp et al 2009). In this study, we rst used the chronic cuprizone model, after which microglia were ablated by the CSF1R inhibitor (PLX3397) according to our previous study (Tahmasebi et al 2020). Cuprizone-induced demyelination model in animals is used to study MSrelated lesions.…”

Oligodendrocyte death and myelin loss in the cuprizone model: an updated overview of the intrinsic and extrinsic causes of cuprizone demyelination

“…PLX3397 is a CSFR1 inhibitor that ablates microglia with minimal upregulation of inflammatory genes [ 204 ], suggesting that inflammation is not overtly induced. Ablation of microglia with PLX3397 during cuprizone treatment reduces the loss of oligodendrocytes and the severity of demyelination in the corpus callosum after 3 weeks and 5 weeks [ 189 , 205 ]. Pre-treatment of mice with PLX3397 for two weeks before cuprizone treatment to ablate microglia to low levels and continued PLX3397 treatment maintains microglia at very low numbers during cuprizone treatment.…”

What microglia depletion approaches tell us about the role of microglia on synaptic function and behavior

“…Microglia depletion has been reported to ameliorate motor impairment in the lysosomal storage disease (Berve et al, 2020) and spinocerebellar ataxia (Qu et al, 2017) when administered before the appearance of the symptoms. Microglia depletion also ameliorated motor impairment after the induction of cuprizone demyelinating model of multiple sclerosis (Tahmasebi et al, 2019(Tahmasebi et al, , 2021. The improved behavioral outcomes were associated with the preservation of nerve fibers (Tahmasebi et al, 2019;Berve et al, 2020), increased post-synaptic densities (Qu et al, 2017), increased re-myelination (Tahmasebi et al, 2019) and reduced neuroinflammation (Qu et al, 2017;Tahmasebi et al, 2019;Berve et al, 2020).…”