Involvement of YKL-40-positive macrophages commonly identified in polymyositis and dermatomyositis in the pathogenesis of myositis: a retrospective study.

YKL-40 is implicated in inflammation and tissue repair, but no reports have investigated its involvement in myositis in polymyositis (PM) and dermatomyositis (DM). Therefore, we aimed to investigate the relationship between YKL-40 and PM/DM. We retrospectively enrolled 35 patients diagnosed with PM/DM along with 26 healthy controls (HCs). Both PM and DM were diagnosed according to Bohan and Peter's criteria. Serum YKL-40 levels were measured, age-corrected to YKL-40 percentile values, and compared to HCs. Patients with myositis without interstitial lung disease were also enrolled and compared to HCs. Immunofluorescence staining was performed to identify YKL-40-positive inflammatory cells in muscle biopsy samples from two patients each with PM and DM. Age-corrected serum YKL-40 levels were significantly higher in patients with PM/DM compared to HCs with and without lung disease; however, these levels decreased significantly after treatment. Immunohistochemical analysis showed infiltration of YKL-40-positive inflammatory cells into the intramuscular sheath and perimuscular membrane. Immunofluorescence staining showed CD68 expression in YKL-40-positive inflammatory cells, suggesting that these cells were macrophages. To the best of our knowledge, this is the first study to demonstrate that YKL-40-positive macrophages are present in PM and DM, indicating that YKL-40 may be involved in PM/DM.

Potential of Adult Endogenous Neural Stem/Progenitor Cells in the Spinal Cord to Contribute to Remyelination in Experimental Autoimmune Encephalomyelitis.

Demyelination and remyelination play pivotal roles in the pathological process of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), a well-established animal model of MS. Although increasing evidence shows that various stimuli can promote the activation/induction of endogenous neural stem/progenitor cells (NSPCs) in the central nervous system, the potential contributions of these cells to remyelination following inflammatory injury remain to be fully investigated. In the present study, using an adult mouse model of EAE induced by myelin oligodendrocyte glycoprotein (MOG) peptide, we investigated whether adult NSPCs in the spinal cord can lead to remyelination under inflammatory conditions. Immunohistochemistry showed that cells expressing the NSPC marker Nestin appeared after MOG peptide administration, predominantly at the sites of demyelination where abundant inflammatory cells had accumulated, whereas Nestin+ cells were rarely present in the spinal cord of PBS-treated control mice. In vitro, Nestin+ NSPCs obtained from EAE mice spinal cords could differentiate into multiple neural lineages, including neurons, astrocytes, and myelin-producing oligodendrocytes. Using the Cre-LoxP system, we established a mouse strain expressing yellow fluorescent protein (YFP) under the control of the Nestin promoter and investigated the expression patterns of YFP-expressing cells in the spinal cord after EAE induction. At the chronic phase of the disease, immunohistochemistry showed that YFP+ cells in the injured regions expressed markers for various neural lineages, including myelin-forming oligodendrocytes. These results show that adult endogenous NSPCs in the spinal cord can be subject to remyelination under inflammatory conditions, such as after EAE, suggesting that endogenous NSPCs represent a therapeutic target for MS treatment.

Sulfatide accumulation in the dystrophic terminals of gracile axonal dystrophy mice: lipid analysis using matrix-assisted laser desorption/ionization imaging mass spectrometry.

The gracile axonal dystrophy (gad) mutation in Uch-l1, the gene encoding the ubiquitin carboxy-terminal hydrolase isozyme L1 (UCH-L1), causes selective dying back degeneration of dorsal root ganglion neuron in the medulla oblongata along with progressive sensory-motor ataxia. Axonal spheroids are observed within degenerating axons, and their contents may illuminate the pathogenic mechanisms leading to neurodegeneration in gad mice. To analyze changes in negatively charged lipid molecules in dystrophic axons of gad mice, we performed matrix-assisted laser desorption/ionization (MALDI)-imaging mass spectrometry (IMS), electron microscopy, and fluorescence immunohistochemistry on tissue sections from gad and wild-type mouse medulla. MALDI-IMS revealed that m/z 806.68 and 822.68 molecules, assigned to sulfatide (ST) C18:0 and ST C18:0(OH), respectively, were concentrated in the dorsomedial medulla. This spatial distribution overlapped significantly with that of axonal spheroids. Immunostaining revealed that spheroids accumulated myelin and lymphocyte protein, a known ST binding protein. Sulfatides with short-chain fatty acids (C16-C20) are generally localized in intracellular vesicles; therefore, ST C18:0 accumulation may reflect intracellular vesicle aggregation within spheroids. Ubiquitin system disruption apparently alters lipid metabolism, membrane organization, protein turnover, and axonal transport. Changes in membrane organization, particularly STs within lipid rafts, may disrupt cellular signaling pathways necessary for neuronal viability.

Muscleblind-like 1 knockout mice reveal novel splicing defects in the myotonic dystrophy brain.

Myotonic dystrophy type 1 (DM1) is a multi-systemic disorder caused by a CTG trinucleotide repeat expansion (CTG(exp)) in the DMPK gene. In skeletal muscle, nuclear sequestration of the alternative splicing factor muscleblind-like 1 (MBNL1) explains the majority of the alternative splicing defects observed in the HSA(LR) transgenic mouse model which expresses a pathogenic range CTG(exp). In the present study, we addressed the possibility that MBNL1 sequestration by CUG(exp) RNA also contributes to splicing defects in the mammalian brain. We examined RNA from the brains of homozygous Mbnl1(ΔE3/ΔE3) knockout mice using splicing-sensitive microarrays. We used RT-PCR to validate a subset of alternative cassette exons identified by microarray analysis with brain tissues from Mbnl1(ΔE3/ΔE3) knockout mice and post-mortem DM1 patients. Surprisingly, splicing-sensitive microarray analysis of Mbnl1(ΔE3/ΔE3) brains yielded only 14 candidates for mis-spliced exons. While we confirmed that several of these splicing events are perturbed in both Mbnl1 knockout and DM1 brains, the extent of splicing mis-regulation in the mouse model was significantly less than observed in DM1. Additionally, several alternative exons, including Grin1 exon 4, App exon 7 and Mapt exons 3 and 9, which have previously been reported to be aberrantly spliced in human DM1 brain, were spliced normally in the Mbnl1 knockout brain. The sequestration of MBNL1 by CUG(exp) RNA results in some of the aberrant splicing events in the DM1 brain. However, we conclude that other factors, possibly other MBNL proteins, likely contribute to splicing mis-regulation in the DM1 brain.

Mice lacking the schizophrenia-associated protein FEZ1 manifest hyperactivity and enhanced responsiveness to psychostimulants.

FEZ1 (fasciculation and elongation protein zeta 1), a mammalian ortholog of Caenorhabditis elegans UNC-76, interacts with DISC1 (disrupted in schizophrenia 1), a schizophrenia susceptibility gene product, and polymorphisms of human FEZ1 have been associated with schizophrenia. We have now investigated the role of FEZ1 in brain development and the pathogenesis of schizophrenia by generating mice that lack Fez1. Immunofluorescence staining revealed FEZ1 to be located predominantly in gamma-aminobutyric acid-containing interneurons. The Fez1(-/-) mice showed marked hyperactivity in a variety of behavioral tests as well as enhanced behavioral responses to the psychostimulants MK-801 and methamphetamine. In vivo microdialysis revealed that the methamphetamine-induced release of dopamine in the nucleus accumbens was exaggerated in the mutant mice, suggesting that enhanced mesolimbic dopaminergic transmission contributes to their hyperactivity phenotype. These observations implicate impairment of FEZ1 function in the pathogenesis of schizophrenia.