Project description:Failure of remyelination in multiple sclerosis (MS) is associated with inhibition of oligodendrocyte precursor (OPC) differentiation, but the cellular and molecular mechanisms involved remain poorly understood. We now report inflammatory demyelination in MS is associated with localized expression of fibroblast growth factor 9 (FGF9) by oligodendrocytes and to a lesser extent astrocytes, and demonstrate FGF9 inhibits myelination and remyelination in vitro. This inhibitory activity is reversible and due to an off target FGF9-dependent effect on astrocytes that disrupts in the growth factor milieu required to support myelination. We identify multiple downstream events induced by FGF9 associated with this effect including increased expression of leukaemia inhibitory growth factor (LIF) and FGF2, both of which are shown to inhibit myelination if present in excess. These studies identify FGF9-dependent signal transduction in astrocytes as a novel target for therapeutic strategies designed to enhance remyelination by endogenous OPC in MS. Gene expression profiles of rat myelinating cultures grown in the presence or absence of FGF9 (100 ng/ml) for 24h and 10 days were generated using Affymetrix GeneChip® Rat Gene 1.0 ST Arrays. Each time point (T1: 24 hrs, and T2: 10 days) has Control (CTR) and Treatment (FGF) groups, with two replicates in each group. In total, 8 arrays were generated from the four groups (CTR-T1, CTR-T2, FGF-T1 and FGF-T2).
Project description:Failure of remyelination in multiple sclerosis (MS) is associated with inhibition of oligodendrocyte precursor (OPC) differentiation, but the cellular and molecular mechanisms involved remain poorly understood. We now report inflammatory demyelination in MS is associated with localized expression of fibroblast growth factor 9 (FGF9) by oligodendrocytes and to a lesser extent astrocytes, and demonstrate FGF9 inhibits myelination and remyelination in vitro. This inhibitory activity is reversible and due to an off target FGF9-dependent effect on astrocytes that disrupts in the growth factor milieu required to support myelination. We identify multiple downstream events induced by FGF9 associated with this effect including increased expression of leukaemia inhibitory growth factor (LIF) and FGF2, both of which are shown to inhibit myelination if present in excess. These studies identify FGF9-dependent signal transduction in astrocytes as a novel target for therapeutic strategies designed to enhance remyelination by endogenous OPC in MS.
Project description:Multiple sclerosis (MS) is an immune-based demyelinating disease. Currently available therapeutics target inflammation but have little impact on promoting remyelination. Furthermore, MS diagnosis is sometimes challenging. Using a demyelination model mice, we previously found that protein tyrosine phosphatase receptor type zeta (PTPRZ) receives abnormal glycosylation, a branched O-mannosyl (O-Man) glycan and that branched O-Man glycosylated PTPRZ specifically occurs in reactive astrocytes of demyelinated lesions. Furthermore, by genetically deleting the branching enzyme, GnT-IX (also known as GnT-Vb), astrogliosis was attenuated and remyelination enhanced. To characterize the PTPRZ expressing astrocytes, microarray analysis was performed using astrocytes from mice after short and long term-cuprizone administration.
Project description:Multiple sclerosis involves an aberrant autoimmune response and progressive failure of remyelination in the central nervous system. Prevention of neural degeneration and subsequent disability requires remyelination through the generation of new oligodendrocytes, but current treatments exclusively target the immune system. Oligodendrocyte progenitor cells are stem cells in the central nervous system and the principal source of myelinating oligodendrocytes. These cells are abundant in demyelinated regions of patients with multiple sclerosis, yet fail to differentiate, thereby representing a cellular target for pharmacological intervention. To discover therapeutic compounds for enhancing myelination from endogenous oligodendrocyte progenitor cells, we screened a library of bioactive small molecules on mouse pluripotent epiblast stem-cell-derived oligodendrocyte progenitor cells. Here we show seven drugs function at nanomolar doses selectively to enhance the generation of mature oligodendrocytes from progenitor cells in vitro. Two drugs, miconazole and clobetasol, are effective in promoting precocious myelination in organotypic cerebellar slice cultures, and in vivo in early postnatal mouse pups. Systemic delivery of each of the two drugs significantly increases the number of new oligodendrocytes and enhances remyelination in a lysolecithin-induced mouse model of focal demyelination. Administering each of the two drugs at the peak of disease in an experimental autoimmune encephalomyelitis mouse model of chronic progressive multiple sclerosis results in striking reversal of disease severity. Immune response assays show that miconazole functions directly as a remyelinating drug with no effect on the immune system, whereas clobetasol is a potent immunosuppressant as well as a remyelinating agent. Mechanistic studies show that miconazole and clobetasol function in oligodendrocyte progenitor cells through mitogen-activated protein kinase and glucocorticoid receptor signalling, respectively. Furthermore, both drugs enhance the generation of human oligodendrocytes from human oligodendrocyte progenitor cells in vitro. Collectively, our results provide a rationale for testing miconazole and clobetasol, or structurally modified derivatives, to enhance remyelination in patients. RNA sequencing of oligodendrocyte progenitor cells treated with vehicle, miconazole or clobetasol for 0, 2, 6, or 12 hours. Cells were plated 1.5 hours prior to addition of drug.
Project description:In a previous study performed in our laboratory, the level of FGF1 RNA was found to be increased in remyelinated multiple sclerosis lesions compared to control brain (unpublished observation). Astrocytes play a key role in multiple sclerosis lesion formation. To shed light on potential FGF1-mediated functions in multiple sclerosis, the impact of FGF1 on astrocytes was investigated.
Project description:Demyelination and dysregulated myelination in the CNS are hallmarks of many neurodegenerative diseases such as multiple sclerosis (MS) and leukodystrophies. Here, we studied GFAP+ astrocytes during de- and remyelination in the cuprizone mouse by exploiting the ribosomal tagging (RiboTag) technology. Analyses were performed 5 weeks after cuprizone feeding, at the peak of demyelination in the corpus callosum, and 0.5 and 2 weeks after cuprizone withdrawal, when remyelination and tissue repair is initiated. After 5 weeks of cuprizone feeding, reactive astrocytes showed inflammatory signatures with enhanced expression of genes that modulate leukocyte migration (Tlr2, Cd86, Parp14,Cxcl10). Furthermore, demyelination-induced reactive astrocytes expressed numerous ligands including Cx3cl1, Csf1, Il34, and Gas6 that act on homeostatic as well as activated microglia and thus potentially mediate activation and recruitment of microglia as well as enhancement of their phagocytosis. During early remyelination, region-specific astrocytes displayed reduced inflammatory response signatures as indicated by shut down of CXCL10 production. During late remyelination, the signatures of GFAP+ astrocytes shifted towards resolving inflammation by active suppression of lymphocyte activation and differentiation and support of glia cell differentiation. Astrocytes showed enhanced expression of osteopontin (SPP1) as well as of factors that are relevant for tissue remodelling (Timp1), regeneration and axonal repair. In conclusion, we detected highly dynamic astroglial transcriptomic signatures in the cuprizone model, which reflects excessive communication amongst glia cells and highlights different astrocyte functions during neurodegeneration and regeneration.