Analysing cerebrospinal fluid with explainable deep learning: From diagnostics to insights.

AIM: Analysis of cerebrospinal fluid (CSF) is essential for diagnostic workup of patients with neurological diseases and includes differential cell typing. The current gold standard is based on microscopic examination by specialised technicians and neuropathologists, which is time-consuming, labour-intensive and subjective. METHODS: We, therefore, developed an image analysis approach based on expert annotations of 123,181 digitised CSF objects from 78 patients corresponding to 15 clinically relevant categories and trained a multiclass convolutional neural network (CNN). RESULTS: The CNN classified the 15 categories with high accuracy (mean AUC 97.3%). By using explainable artificial intelligence (XAI), we demonstrate that the CNN identified meaningful cellular substructures in CSF cells recapitulating human pattern recognition. Based on the evaluation of 511 cells selected from 12 different CSF samples, we validated the CNN by comparing it with seven board-certified neuropathologists blinded for clinical information. Inter-rater agreement between the CNN and the ground truth was non-inferior (Krippendorff's alpha 0.79) compared with the agreement of seven human raters and the ground truth (mean Krippendorff's alpha 0.72, range 0.56-0.81). The CNN assigned the correct diagnostic label (inflammatory, haemorrhagic or neoplastic) in 10 out of 11 clinical samples, compared with 7-11 out of 11 by human raters. CONCLUSIONS: Our approach provides the basis to overcome current limitations in automated cell classification for routine diagnostics and demonstrates how a visual explanation framework can connect machine decision-making with cell properties and thus provide a novel versatile and quantitative method for investigating CSF manifestations of various neurological diseases.

Eosinophilic fasciitis (Shulman syndrome)-recognition of the histological spectrum allows for new insights into possible pathomechanisms.

OBJECTIVES: EF is a rare disease characterized by fibrosis and inflammation of the fascia, scleroderma-like skin indurations and optional blood eosinophilia. We aimed to expand the knowledge about its aetiology and pathogenesis. METHODS: Biopsy specimens from 16 EF patients were assessed by histology, immunohistochemistry and quantitative reverse transcription PCR in comparison with anti-Mi-2+ DM patients and non-disease controls. RESULTS: Histologically, EF shows mild to severe inflammation at the muscle-fascia interface, with frequent involvement of the underlying muscle tissue, though varying in degree. CD206+ macrophages predominate and eosinophils are detected within the fascia in the majority of cases, however in quite small numbers, and seen infrequently within the muscle. Activators of the so-called Th2-M2 pathway like STAT6 and IL-4 are upregulated leading to high expression levels of CD206. Activators of the so-called Th1-M1 pathway like STAT1 and IFN-γ (IFNG) are also upregulated, though not translating into a significant upregulation of the effector molecule COX2. Interestingly, activators or chemoattractants of eosinophils show no significant upregulation in EF compared with DM. EF shows features of perifascicular pathology comparable to DM, with upregulation of MHC class I and II; however, this is not accompanied by perifascicular atrophy or any signs of a type I IFN response or hypoxia-mediated processes. CONCLUSIONS: Our findings highlight a specific immune phenotype of leucocyte infiltrates in EF along features of perifascicular pathology similar to DM, while there is no evidence of hypoxia-mediated or type I IFN-associated processes with perifascicular fibre atrophy, indicating different pathomechanisms of muscle involvement.

Dermatomyositis With or Without Anti-Melanoma Differentiation-Associated Gene 5 Antibodies: Common Interferon Signature but Distinct NOS2 Expression.

The anti-melanoma differentiation-associated gene 5 (MDA5) autoantibody is specifically associated with dermatomyositis (DM). Nevertheless, anti-MDA5(+)-patients experience characteristic symptoms distinct from classic DM, including severe signs of extramuscular involvement; however, the clinical signs of myopathy are mild or even absent. The morphological and immunological features are not yet described in adulthood. Data concerning the pathophysiology of anti-MDA5 DM are sparse; however, the importance of the interferon (IFN) type I pathway involved in DM has been shown. Our aim was to define morphological alterations of the skeletal muscle and the intrinsic immune response of anti-MDA5-positive DM patients. Immunohistological and RT-PCR analysis of muscle biopsy specimens from anti-MDA5 and classic DM were compared. Those with anti-MDA5 DM did not present the classic features of perifascicular fiber atrophy and major histocompatibility complex class I expression. They did not show significant signs of capillary loss; tubuloreticular formations were observed less frequently. Inflammation was focal, clustering around single vessels but significantly less intense. Expression of IFN-stimulated genes was up-regulated in anti-MDA5 DM; however, the IFN score was significantly lower. Characteristic features were observed in anti-MDA5 DM and not in classic DM patients. Only anti-MDA5 DM showed numerous nitric oxide synthase 2-positive muscle fibers with sarcoplasmic colocalization of markers of regeneration and cell stress. Anti-MDA5-positive patients demonstrate a morphological pattern distinct from classic DM.

Th2-M2 immunity in lesions of muscular sarcoidosis and macrophagic myofasciitis.

OBJECTIVE: To analyse the paradox of a lack of giant cell formation and fibrosis in chronic lesions of macrophagic myofasciitis (MMF) in comparison with muscular sarcoidosis (MuS). METHODS: Inflammatory lesions and contiguous muscle regions from biopsy samples of 10 patients with MuS and 10 patients with MMF were cut out by laser microdissection. Mediators of the T helper cell (Th)1 inducing classical macrophage activation (e.g. STAT1, IFNγ and CXCR3), and Th2 inducing alternative activation of macrophages (e.g. CD206/MRC1, STAT6, SOCS1), molecules involved in development of fibrosis (e.g. TGFß) and giant cells (e.g. TYROBP), were assessed by immunohistochemistry and real-time polymerase chain reaction (PCR). RESULTS: STAT6-induced Th2 immunity was associated with up-regulated gene expression of MRC1, SOCS1 and TGFB in inflammatory foci, in comparison with adjacent tissue. TYROBP and TREM2, genes regulating giant cell formation, were more strongly expressed in lesions of MuS patients than in those of MMF. TGFß co-localized with CD206(+) macrophages in MuS but not in MMF. Conversely, Th1 immunity was illustrated by STAT1 staining both in macrophages and myofibres in MuS, but not in MMF. Also, STAT1-induced IFNG and CXCR3 expression in lesions and the surrounding tissue was elevated compared with normal controls, but without statistically significant differences. CONCLUSION: Giant cell and typical granuloma formations, including fibrogenesis, is dependent on two main mechanisms, both involving specific macrophage activation: a strong Th2-M2 polarization and a significant expression of TYROBP and TGFß in macrophages. The low-grade alternative activation of macrophages in MMF lesions and poor TYROBP and TGFßco-expression are obviously insufficient to produce giant cells.

Mast cells protect from post-traumatic spinal cord damage in mice by degrading inflammation-associated cytokines via mouse mast cell protease 4.

Mast cells (MCs) are found abundantly in the central nervous system and play a complex role in neuroinflammatory diseases such as multiple sclerosis and stroke. In the present study, we show that MC-deficient Kit(W-sh/W-sh) mice display significantly increased astrogliosis and T cell infiltration as well as significantly reduced functional recovery after spinal cord injury compared to wildtype mice. In addition, MC-deficient mice show significantly increased levels of MCP-1, TNF-α, IL-10 and IL-13 protein levels in the spinal cord. Mice deficient in mouse mast cell protease 4 (mMCP4), an MC-specific chymase, also showed increased MCP-1, IL-6 and IL-13 protein levels in spinal cord samples and a decreased functional outcome after spinal cord injury. A degradation assay using supernatant from MCs derived from either mMCP4(-/-) mice or controls revealed that mMCP4 cleaves MCP-1, IL-6, and IL-13 suggesting a protective role for MC proteases in neuroinflammation. These data show for the first time that MCs may be protective after spinal cord injury and that they may reduce CNS damage by degrading inflammation-associated cytokines via the MC-specific chymase mMCP4.

Mast cells protect from post-traumatic brain inflammation by the mast cell-specific chymase mouse mast cell protease-4.

Mast cells (MCs) are found abundantly in the brain and the meninges and play a complex role in neuroinflammatory diseases, such as stroke and multiple sclerosis. Here, we show that MC-deficient Kit/Kit mice display increased neurodegeneration in the lesion area after brain trauma. Furthermore, MC-deficient mice display significantly more brain inflammation, namely an increased presence of macrophages/microglia, as well as dramatically increased T-cell infiltration at days 4 and 14 after injury, combined with increased astrogliosis at day 14 following injury. The number of proliferating Ki67 macrophages/microglia and astrocytes around the lesion area is more than doubled in these MC-deficient mice. In parallel, MC-deficient Kit mice display increased presence of macrophages/microglia at day 4, and persistent astrogliosis at day 4 and 14 after brain trauma. Further analysis of mice deficient in one of the most relevant MC proteases, i.e., mouse mast cell protease 4 (mMCP-4), revealed that astrogliosis and T-cell infiltration are significantly increased in mMCP-4-knockout mice. Finally, treatment with an inhibitor of mMCP-4 significantly increased macrophage/microglia numbers and astrogliosis. These data suggest that MCs exert protective functions after trauma, at least in part via mMCP-4, by suppressing exacerbated inflammation via their proteases.

The genomic and transcriptional landscape of primary central nervous system lymphoma.

Primary lymphomas of the central nervous system (PCNSL) are mainly diffuse large B-cell lymphomas (DLBCLs) confined to the central nervous system (CNS). Molecular drivers of PCNSL have not been fully elucidated. Here, we profile and compare the whole-genome and transcriptome landscape of 51 CNS lymphomas (CNSL) to 39 follicular lymphoma and 36 DLBCL cases outside the CNS. We find recurrent mutations in JAK-STAT, NFkB, and B-cell receptor signaling pathways, including hallmark mutations in MYD88 L265P (67%) and CD79B (63%), and CDKN2A deletions (83%). PCNSLs exhibit significantly more focal deletions of HLA-D (6p21) locus as a potential mechanism of immune evasion. Mutational signatures correlating with DNA replication and mitosis are significantly enriched in PCNSL. TERT gene expression is significantly higher in PCNSL compared to activated B-cell (ABC)-DLBCL. Transcriptome analysis clearly distinguishes PCNSL and systemic DLBCL into distinct molecular subtypes. Epstein-Barr virus (EBV)+ CNSL cases lack recurrent mutational hotspots apart from IG and HLA-DRB loci. We show that PCNSL can be clearly distinguished from DLBCL, having distinct expression profiles, IG expression and translocation patterns, as well as specific combinations of genetic alterations.

Sequestosome-1 (p62) expression reveals chaperone-assisted selective autophagy in immune-mediated necrotizing myopathies.

Diffuse myofiber necrosis in the context of inflammatory myopathy is the hallmark of immune-mediated necrotizing myopathy (IMNM). We have previously shown that skeletal muscle fibers of IMNM patients may display nonrimmed vacuoles and sarcoplasmic irregularities. The dysfunctional chaperone activity has been linked to the defective assembly of skeletal muscle proteins and their degradation via lysosomes, autophagy and the proteasomal machinery. This study was undertaken to highlight a chaperone-assisted selective autophagy (CASA) pathway, functionally involved in protein homeostasis, cell stress and the immune response in skeletal muscle of IMNM patients. Skeletal muscle biopsies from 54 IMNM patients were analyzed by immunostaining, as well as by qPCR. Eight biopsies of sIBM patients served as pathological controls, and eight biopsies of nondisease control subjects were included. Alteration of autophagy was detectable in all IMNM biopsy samples highlighted via a diffuse sarcoplasmic staining pattern by p62 and LC3 independent of vacuoles. This pattern was at variance with the coarse focal staining pattern mostly confined to rimmed vacuoles in sIBM. Colocalization of p62 with the chaperone proteins HSP70 and αB-crystalline points to the specific targeting of misfolded proteins to the CASA machinery. Bcl2-associated athanogene 3 (BAG3) positivity of these fibers emphasizes the selectivity of autophagy processes and these fibers also express MHC class I sarcolemma. Expression of genes involved in autophagy and endoplasmic reticulum (ER) stress pathways studied here is significantly upregulated in IMNM. We highlight that vacuoles without sarcolemmal features may arise in IMNM muscle biopsies, and they must not be confounded with sIBM-specific vacuoles. Further, we show the activation of selective autophagy and emphasize the role of chaperones in this context. CASA occurs in IMNM muscle, and specific molecular pathways of autophagy differ from the ones in sIBM, with p62 as a unique identifier of this process.

Inflammation-induced fibrosis in skeletal muscle of female carriers of Duchenne muscular dystrophy.

Female carriers of DMD gene mutations may be symptomatic and show variable skeletal as well as cardiac muscle symptoms. Skeletal muscle can exhibit morphological alterations. However, inflammatory, degenerative and fibrotic changes as seen in Duchenne boys have not been specifically analysed yet, so we addressed the question whether skeletal muscle of female carriers show such alterations. Thirteen carriers with an age range of 3 to 50 years were studied retrospectively. Five out of 13 women had clinically affected relatives. Clinically, most women showed mild muscle weakness, while the CK levels were increased in nine of them. Histomorphological analyses highlighted the typical mosaic pattern of dystrophin-positive and -negative fibres. Regenerating fibres were diffusely scattered and focally pronounced, while endo- and perimysial fibrosis was a variable but constant feature. Infiltration of CD206+TGFß+ macrophages and scattered T cells was noted in the endomysium. TGFb and CCL18, were significantly increased. However, gene expression of markers involved in Th1/Th2 immunity did not reach statistical significance compared to non-diseased controls. In summary, skeletal muscle of clinically manifest female DMD gene mutation carriers shows mild fibrosis and increased regeneration associated with endomysial CD206+TGFß+ and STAT6+ macrophages, which are most likely involved in fibrotic remodelling.

Architectural B-cell organization in skeletal muscle identifies subtypes of dermatomyositis.

OBJECTIVE: To study the B-cell content, organization, and existence of distinct B-cell subpopulations in relation to the expression of type 1 interferon signature related genes in dermatomyositis (DM). METHODS: Evaluation of skeletal muscle biopsies from patients with adult DM (aDM) and juvenile DM (jDM) by histology, immunohistochemistry, electron microscopy, and quantitative reverse-transcription PCR. RESULTS: We defined 3 aDM subgroups-classic (containing occasional B cells without clusters), B-cell-rich, and follicle-like aDM-further elucidating IM B-lymphocyte maturation and immunity. The quantity of B cells and formation of ectopic lymphoid structures in a subset of patients with aDM were associated with a specific profile of cytokines and chemokines involved in lymphoid neogenesis. Levels of type 1 interferon signature related gene expression paralleled B-cell content and architectural organization and link B-cell immunity to the interferon type I signature. CONCLUSION: These data corroborate the important role of B cells in DM, highlighting the direct link between humoral mechanisms as key players in B-cell immunity and the role of type I interferon-related immunity.

Differential roles of hypoxia and innate immunity in juvenile and adult dermatomyositis.

Dermatomyositis (DM) can occur in both adults and juveniles with considerable clinical differences. The links between immune-mediated mechanisms and vasculopathy with respect to development of perifascicular pathology are incompletely understood. We investigated skeletal muscle from newly diagnosed, treatment-naïve juvenile (jDM) and adult dermatomyositis (aDM) patients focusing on hypoxia-related pathomechanisms, vessel pathology, and immune mechanisms especially in the perifascicular region. Therefore, we assessed the skeletal muscle biopsies from 21 aDM, and 15 jDM patients by immunohistochemistry and electron microscopy. Transcriptional analyses of genes involved in hypoxia, as well as in innate and adaptive immunity were performed by quantitative Polymerase chain reaction (qPCR) of whole tissue cross sections including perifascicular muscle fibers.Through these analysis, we found that basic features of DM, like perifascicular atrophy and inflammatory infiltrates, were present at similar levels in jDM and aDM patients. However, jDM was characterized by predominantly hypoxia-driven pathology in perifascicular small fibers and by macrophages expressing markers of hypoxia. A more pronounced regional loss of capillaries, but no relevant activation of type-1 Interferon (IFN)-associated pathways was noted. Conversely, in aDM, IFN-related genes were expressed at significantly elevated levels, and Interferon-stimulated gene (ISG)15 was strongly positive in small perifascicular fibers whereas hypoxia-related mechanisms did not play a significant role.In our study we could provide new molecular data suggesting a conspicuous pathophysiological 'dichotomy' between jDM and aDM: In jDM, perifascicular atrophy is tightly linked to hypoxia-related pathology, and poorly to innate immunity. In aDM, perifascicular atrophy is prominently associated with molecules driving innate immunity, while hypoxia-related mechanisms seem to be less relevant.

Deletion of Jun proteins in adult oligodendrocytes does not perturb cell survival, or myelin maintenance in vivo.

Oligodendrocytes, the myelin-forming glial cells of the central nervous system (CNS), are fundamental players in rapid impulse conduction and normal axonal functions. JunB and c-Jun are DNA-binding components of the AP-1 transcription factor, which is known to regulate different processes such as proliferation, differentiation, stress responses and death in several cell types, including cultured oligodendrocyte/lineage cells. By selectively inactivating Jun B and c-Jun in myelinating oligodendrocytes in vivo, we generated mutant mice that developed normally, and within more than 12 months showed normal ageing and survival rates. In the adult CNS, absence of JunB and c-Jun from mature oligodendrocytes caused low-grade glial activation without overt signs of demyelination or secondary leukocyte infiltration into the brain. Even after exposure to toxic or autoimmune oligodendrocyte insults, signs of altered oligodendrocyte viability were mild and detectable only upon cuprizone treatment. We conclude that JunB and c-Jun expression in post-mitotic oligodendrocytes is mostly dispensable for the maintainance of white matter tracts throughout adult life, even under demyelinating conditions.

Nuclear actin aggregation is a hallmark of anti-synthetase syndrome-induced dysimmune myopathy.

OBJECTIVE: To analyze antisynthetase syndrome-associated myositis by modern myopathologic methods and to define its place in the spectrum of idiopathic inflammatory myopathies (IIMs). METHODS: Skeletal muscle biopsies from antisynthetase syndrome-associated myositis and other IIMs from different institutions worldwide were analyzed by histopathology, quantitative PCR, and electron microscopy. RESULTS: Myonuclear actin filament inclusions were identified as a unique morphologic hallmark of antisynthetase syndrome-associated myositis. Nuclear actin inclusions were never found in dermatomyositis, polymyositis, sporadic inclusion body myositis, autoimmune necrotizing myopathy associated with signal recognition particle or 3-hydroxy-3-methylglutaryl-coenzyme A reductase autoantibodies, or nonspecific myositis associated with other systemic diseases, harboring myositis-associated autoantibodies, and presenting myofiber necrosis. We show that molecules involved in actin filament formation and actin shuttling mechanisms are altered in antisynthetase syndrome, and may thus be involved in pathologic myonuclear actin aggregation. In addition, we have identified a typical topographic distribution of necrotic myofibers predominantly located at the periphery of muscle fascicles accompanied by inflammation and destruction of the perimysial connective tissue. CONCLUSION: Antisynthetase syndrome-associated myositis is characterized by distinctive myonuclear actin filament inclusions, including rod formations and a typical necrotizing perimysial myositis. This supports the hypothesis that antisynthetase syndrome-associated myositis is unique and should not be grouped among dermatomyositis, polymyositis, sporadic inclusion body myositis, necrotizing autoimmune myositis, or nonspecific myositis. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that for patients with IIMs, the presence of myonuclear actin filament inclusions accurately identifies patients with antisynthetase syndrome-associated myositis (sensitivity 81%, specificity 100%).

The lymphoid follicle variant of dermatomyositis.

OBJECTIVE: To investigate the clinical and morphologic spectrum of early adult-onset dermatomyositis (DM), an inflammatory disease that affects small vessels of the muscle and the skin. METHODS: Histologic evaluation of frozen muscle samples was employed to visualize the cellular organization of ectopic lymphoid structures in muscle biopsies obtained from 2 patients diagnosed with DM. Clinical presentation and morphologic features, as well as treatment and follow-up, were assessed and documented. Electron microscopy was used to confirm the light microscopic diagnosis of DM. Clonality analysis of B-cell populations using PCR was performed. RESULTS: Muscle biopsy of both patients fulfilled the morphologic European Neuromuscular Centre criteria of DM. Analyses of muscle biopsy samples revealed ectopic lymphoid follicle-like structures that showed a remarkable similarity to secondary lymphoid organs (SLOs) with distinct T- and B-cell compartmentalization. Our 2 patients exhibited an atypical and mild clinical presentation and responded favorably to therapy. CONCLUSIONS: The clinical and histopathologic features of DM can be atypical, and the presence of SLOs is not inevitably linked to an unfavorable prognosis.