Josefine Radke

Early Loss of Pericytes and Perivascular Stromal Cell-Induced Scar Formation after Stroke

Despite its limited regenerative capacity, the central nervous system (CNS) shares more repair mechanisms with peripheral tissues than previously recognized. Scar formation is a ubiquitous healing mechanism aimed at patching tissue defects via the generation of fibrous extracellular matrix (ECM). This process, orchestrated by stromal cells, can unfavorably affect the capacity of tissues to restore function. Vascular mural cells have been found to contribute to scarring after spinal cord injury. In the case of stroke, little is known about the responses of pericytes (PCs) and stromal cells. Here, we show that capillary PCs are rapidly lost after cerebral ischemia in both experimental and human stroke. Coincident with this loss is a massive proliferation of resident platelet-derived growth factor receptor beta (PDGFRβ)+ and CD105+ stromal cells, which originate from the neurovascular unit and deposit ECM in the ischemic mouse brain. The presence of PDGFRβ+ stromal cells demarcates a fibrotic, contracted, and macrophage-laden lesion core from the rim of hypertrophic astroglia in both experimental and human stroke. We suggest that a previously unrecognized population of CNS-resident stromal cells drives a dynamic process of scarring after cerebral ischemia, which appears distinct from the glial scar and represents a novel target for regenerative stroke therapies.

P2Y12 receptor is expressed on human microglia under physiological conditions throughout development and is sensitive to neuroinflammatory diseases

Microglia are resident immune cells in the central nervous system (CNS), which are essential for immune defence and critically contribute to neuronal functions during homeostasis. Until now, little is known about microglia biology in humans in part due to the lack of microglia‐specific markers. We therefore investigated the expression of the purinergic receptor P2Y12 in human brain tissue. Compared to classical markers used to identify microglia such as Iba1, CD68 or MHCII, we found that P2Y12 is expressed on parenchymal microglia but is absent from perivascular or meningeal macrophages. We further demonstrate that P2Y12 expression is stable throughout human brain development, including fetal phases, and quantification of P2 Y12+ microglia revealed that the density of human microglia is constant throughout lifetime. In contrast, CD68 expression increases during aging in cerebellar but not in cortical microglia, indicating regional heterogeneity. CNS pathologies such as Alzheimers disease or multiple sclerosis—but not schizophrenia—result in decreased P2Y12 immunoreactivity in plaque‐ or lesion‐associated myeloid cells, whereas Iba1 expression remains detectable. Our results suggest that P2Y12 is a useful marker for the identification of human microglia throughout the lifespan. Moreover, P2Y12 expression might help to discriminate activated microglia and infiltrating myeloid cells from quiescent microglia in the human CNS. GLIA 2017;65:375–387

MicroRNA-138 is a potential regulator of memory performance in humans

Genetic factors underlie a substantial proportion of individual differences in cognitive functions in humans, including processes related to episodic and working memory. While genetic association studies have proposed several candidate “memory genes,” these currently explain only a minor fraction of the phenotypic variance. Here, we performed genome-wide screening on 13 episodic and working memory phenotypes in 1318 participants of the Berlin Aging Study II aged 60 years or older. The analyses highlight a number of novel single nucleotide polymorphisms (SNPs) associated with memory performance, including one located in a putative regulatory region of microRNA (miRNA) hsa-mir-138-5p (rs9882688, P-value = 7.8 × 10−9). Expression quantitative trait locus analyses on next-generation RNA-sequencing data revealed that rs9882688 genotypes show a significant correlation with the expression levels of this miRNA in 309 human lymphoblastoid cell lines (P-value = 5 × 10−4). In silico modeling of other top-ranking GWAS signals identified an additional memory-associated SNP in the 3′ untranslated region (3′ UTR) of DCP1B, a gene encoding a core component of the mRNA decapping complex in humans, predicted to interfere with hsa-mir-138-5p binding. This prediction was confirmed in vitro by luciferase assays showing differential binding of hsa-mir-138-5p to 3′ UTR reporter constructs in two human cell lines (HEK293: P-value = 0.0470; SH-SY5Y: P-value = 0.0866). Finally, expression profiling of hsa-mir-138-5p and DCP1B mRNA in human post-mortem brain tissue revealed that both molecules are expressed simultaneously in frontal cortex and hippocampus, suggesting that the proposed interaction between hsa-mir-138-5p and DCP1B may also take place in vivo. In summary, by combining unbiased genome-wide screening with extensive in silico modeling, in vitro functional assays, and gene expression profiling, our study identified miRNA-138 as a potential molecular regulator of human memory function.

Prognostic impact of B-cell lymphoma 6 in primary CNS lymphoma

BACKGROUND We investigated the prognostic significance of B-cell differentiation status and common B-cell differentiation markers in a post hoc analysis of 119 patients with primary CNS lymphoma (PCNSL) homogeneously receiving high-dose methotrexate (HDMTX)-based chemotherapy within the prospective G-PCNSL-SG1 trial. METHODS We evaluated protein expression of B-cell lymphoma 2 (BCL2), BCL6, CD10, and multiple myeloma oncogene 1/interferon regulatory factor 4 (MUM1/IRF4) by immunohistochemistry and analyzed the association with survival. RESULTS The median follow-up of all patients was 67.5 months. Median progression-free survival (PFS) was 10.61 months (95% CI: 4.23-17.00). Median overall survival (OS) was 28.85 months (95% CI: 17.96-39.73). Eighty-nine tumors expressed BCL2 (92.7%), 24 (20.5%) expressed CD10, 60 (54.1%) expressed BCL6, and 87 (79.0%) expressed MUM1/IRF4. On the basis of the Hans algorithm, 80 tumors (73.4%) were classified to the non-germinal center B group, suggesting a post-germinal center origin of PCNSL. Expression of BCL6 (cutoff point 30%), but none of the other markers, was associated with shorter PFS (P = .047) and OS (P = .035). On multivariate analysis, BCL6 expression was associated with shorter PFS (hazard ratio: 1.95, 95% CI: 1.22-3.12, P = .005) but not OS (hazard ratio: 1.85, 95% CI: 0.71-4.80, P = .21). Classification according to Hans algorithm and expression status of the single B-cell markers BCL2, CD10, and MUM1/IRF4 did not correlate with prognosis. CONCLUSION The findings are limited by the fact that only 23% of all G-PCNSL-SG1 patients could be included in the analysis. If validated in an independent cohort, BCL6 may assume clinical relevance as an unfavorable prognostic biomarker in PCNSL.

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.

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.

The evolution of the anaplastic cerebellar liponeurocytoma: case report and review of the literature.

Cerebellar liponeurocytoma, first recognized as a distinct entity in the revised WHO classification of Tumors of the Central Nervous System in 2000, is a rare tumor with characteristic histological features and predominant location in the cerebellum. The proliferative index is usually low, and previous reports supported a favorable prognosis. We report a case of a second recurrence of a cerebellar liponeurocytoma with increased proliferative and mitotic activity in which extensive immunohistochemical characterization and genetic profiling were performed. The tumor specimen was characterized in terms of genetic changes frequently associated with gliomas and medulloblastomas. Considering the low number of reported cases, the prognosis of cerebellar liponeurocytoma seems difficult to assess. Our case suggests the existence of different histological grades of cerebellar liponeurocytoma and its possible progression towards a dedifferentiated, malignant phenotype, which has not yet been adequately taken into consideration in the current WHO classification.

Prognostic Relevance of Tumor Purity and TERT Promoter Mutations on MGMT Promoter Methylation in Glioblastoma.

Promoter methylation status of O-6-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme, is a critical biomarker in glioblastoma (GBM), as treatment decisions and clinical trial inclusion rely on its accurate assessment. However, interpretation of results is complicated by poor interassay reproducibility as well as a weak correlation between methylation status and expression levels of MGMT. This study systematically investigates the influence of tumor purity on tissue subjected to MGMT analysis. A quantitative, allele-specific real-time PCR (qAS-PCR) assay was developed to determine genotype and mutant allele frequency of telomerase promoter (pTERT) mutations as a direct measure of tumor purity. We studied tumor purity, pTERT mutation by Sanger sequencing, MGMT methylation by pyrosequencing, IDH1 mutation status, and clinical parameters in a cohort of high-grade gliomas (n = 97). The qAS-PCR reliably predicted pTERT genotype and tumor purity compared with independent methods. Tumor purity positively and significantly correlated with the extent of methylation in MGMT methylated GBMs. Extent of MGMT methylation differed significantly with respect to pTERT mutation hotspot (C228T vs. C250T). Interestingly, frontal lobe tumors showed greater tumor purity than those in other locations. Above all, tumor purity was identified as an independent prognostic factor in GBM. In conclusion, we determined mutual associations of tumor purity with MGMT methylation and pTERT mutations and found that the extent of MGMT methylation reflects tumor purity. In turn, tumor purity is prognostic in IDH1 wild-type GBM. Implications: Tumor purity is an independent prognostic marker in glioblastoma and is associated with the extent of MGMT methylation. Mol Cancer Res; 15(5); 532–40. ©2017 AACR.

Cellular heterogeneity contributes to subtype-specific expression of ZEB1 in human glioblastoma

The transcription factor ZEB1 has gained attention in tumor biology of epithelial cancers because of its function in epithelial-mesenchymal transition, DNA repair, stem cell biology and tumor-induced immunosuppression, but its role in gliomas with respect to invasion and prognostic value is controversial. We characterized ZEB1 expression at single cell level in 266 primary brain tumors and present a comprehensive dataset of high grade gliomas with Ki67, p53, IDH1, and EGFR immunohistochemistry, as well as EGFR FISH. ZEB1 protein expression in glioma stem cell lines was compared to their parental tumors with respect to gene expression subtypes based on RNA-seq transcriptomic profiles. ZEB1 is widely expressed in glial tumors, but in a highly variable fraction of cells. In glioblastoma, ZEB1 labeling index is higher in tumors with EGFR amplification or IDH1 mutation. Co-labeling studies showed that tumor cells and reactive astroglia, but not immune cells contribute to the ZEB1 positive population. In contrast, glioma cell lines constitutively express ZEB1 irrespective of gene expression subtype. In conclusion, our data indicate that immune infiltration likely contributes to differential labelling of ZEB1 and confounds interpretation of bulk ZEB1 expression data.

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.