Experimental Demyelination and Axonal Loss Are Reduced in MicroRNA-146a Deficient Mice

Abstract

BackgroundThe cuprizone (CPZ) model of multiple sclerosis (MS) was used to identify microRNAs (miRNAs) related to in vivo de- and remyelination. We further investigated the role of miR-146a in miR-146a-deficient (KO) mice: this miRNA is differentially expressed in MS lesions and promotes differentiation of oligodendrocyte precursor cells (OPCs) during remyelination, but its role has not been examined during demyelination.MethodsMicroRNAs were examined by Agilent Mouse miRNA Microarray in the corpus callosum during CPZ-induced demyelination and remyelination. Demyelination, axonal loss, changes in number of oligodendrocytes, OPCs, and macrophages/microglia was compared by histology/immunohistochemistry between KO and WT mice. Differential expression of target genes and proteins of miR-146a was analyzed in the transcriptome (4 × 44K Agilent Whole Mouse Genome Microarray) and proteome (liquid chromatography tandem mass spectrometry) of CPZ-induced de- and remyelination in WT mice. Levels of proinflammatory molecules in the corpus callosum were compared in WT versus KO mice by Meso Scale Discovery multiplex protein analysis.ResultsmiR-146a was increasingly upregulated during CPZ-induced de- and remyelination. The absence of miR-146a in KO mice protected against demyelination, axonal loss, body weight loss, and atrophy of thymus and spleen. The number of CNP+ oligodendrocytes was increased during demyelination in the miR-146a KO mice, while there was a trend of increased number of NG2+ OPCs in the WT mice. miR-146a target genes, SNAP25 and SMAD4, were downregulated in the proteome of demyelinating corpus callosum in WT mice. Higher levels of SNAP25 were measured by ELISA in the corpus callosum of miR-146a KO mice, but there was no difference between KO and WT mice during demyelination. Multiplex protein analysis of the corpus callosum lysate revealed upregulated TNF-RI, TNF-RII, and CCL2 in the WT mice in contrast to KO mice. The number of Mac3+ and Iba1+ macrophages/microglia was reduced in the demyelinating corpus callosum of the KO mice.ConclusionDuring demyelination, absence of miR-146a reduced inflammatory responses, demyelination, axonal loss, the number of infiltrating macrophages, and increased the number of myelinating oligodendrocytes. The number of OPCs was slightly higher in the WT mice during remyelination, indicating a complex role of miR-146a during in vivo de- and remyelination.

Differential Expression of miRNAs and Behavioral Change in the Cuprizone-Induced Demyelination Mouse Model

“…After 6 weeks of CPZ treatment, the diet was changed to normal rodent chow for an additional 2, 4, and 6 weeks to examine remyelination. According to a bibliographic investigation before the start of the experiment [13,38,51,56], it was confirmed that both females and males were used to induce the cuprizone-induced model, and the test results were similar in the laboratory. Twenty-six animals were divided into two groups of 13 animals each.…”

“…One of the MS-related miRNAs, miR-146a, is differentially expressed in MS lesions and promotes the differentiation of oligodendrocyte precursor cells (OPCs) during remyelination [50]; moreover, it is upregulated during CPZ-induced de-and remyelination [51]. In particular, Martin et al (2018) reported that experimental demyelination and axonal loss are reduced in mice deficient in microRNA-146a and that the number of OPCs is slightly higher in WT mice during remyelination, indicating the complex role of miR-146a during in vivo de-and remyelination [51]. In our results, miR-146a-5p was significantly upregulated in mice subjected to CPZ-induced demyelination, suggesting that it may be a key miRNA involved in the induction of demyelination in CPZ-fed mice.…”

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

“…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). Studies have indicated that the apparent failure to trigger a T-cell-mediated CNS immune response is due to CPZ-induced atrophy of the thymus (the organ responsible for T-cell maturation and differentiation) and spleen (the organ of T and B lymphocyte production; Solti et al, 2015;Martin et al, 2018;Sui et al, 2019;Sen et al, 2019a). Two additional effects of CPZ on the integrity and function of the peripheral immune system include an increase in the abundance of splenic arginase-I (a protein expressed by myeloid-derived suppressor cells in spleen) and a decreased abundance of protein disulfide isomerize (a protein required for assembly of the major histocompatibility complex-I; Partridge et al, 2016).…”

Epigenetic regulation of myelination in health and disease

“…In cuprizone demyelination model, miR‐146a was upregulated during de‐ and remyelination (Martin et al., ). The depletion of miR‐146a protected demyelination and axonal loss (Martin et al., ). These studies then highlight the significance of miRNAs in the treatment of CNS demyelination disease.…”

“…In EAE mouse model, the expression of miR-19b is significantly reduced, and application of agomiR-19b may enhance the expression of MBP and CNPase and ameliorate demyelination symptoms (Hu, Hu, Zeng, Xiao, & Yang, 2018). In cuprizone demyelination model, miR-146a was upregulated during de-and remyelination (Martin et al, 2018). The depletion of miR-146a protected demyelination and axonal loss (Martin et al, 2018).…”