Acta Neuropathologica最新文献

Tumor-associated macrophages (TAMs) represent the main immune cell population in various brain malignancies, but there is rare knowledge on the functional and, in particular, the prognostic role of TAMs in the meningioma (MGM) microenvironment. Here, we investigated TAM frequencies, activation state, survival-associated changes, and their association with tumor-infiltrating T lymphocytes (TILs) in two independent study samples comprising altogether 680 MGMs. To this end, we performed tissue cytometry analyses, quantified tissue cytokine levels, and integrated previously published TIL infiltration and microarray datasets in the discovery cohort comprising n = 195 clinically well-annotated cases. This was complemented by a DNA methylation-based deconvolution approach to predict TAM and TIL infiltration rates using immune cell-specific CpG sites as well as survival associations in an independent validation cohort of n = 485 MGMs. Our findings revealed substantial but heterogeneous TAM infiltration in newly diagnosed MGMs, with increased numbers of pro-tumoral TAMs in clinically aggressive tumors. Additional cytokine and transcriptome analyses corroborated the presence of an immunosuppressive niche in TAM-enriched MGMs. Importantly, a high frequency of pro-tumoral TAMs was associated with poor patient outcome, and high TAM infiltration was further identified as an independent prognostic factor for inferior survival, counteracting the beneficial prognostic effect of TILs. Moreover, methylation-based deconvolution analyses confirmed the opposing prognostic roles of TAMs and TILs in the validation cohort. Altogether, higher numbers of TAMs appear to be a hallmark of clinically aggressive behavior in newly diagnosed and recurrent MGMs. Unlike TILs, immunosuppressive TAMs seem to play a dominant role in the immunological landscape of MGMs with a significant negative impact on patient outcome, highlighting pro-tumoral TAMs to be an attractive treatment target in MGMs. Furthermore, our deconvolution approach presents a pipeline to computationally determine TAM and TIL infiltrates in the MGM microenvironment, which might be highly valuable for patient stratification for future immunotherapeutic treatments.

Disturbances within the cerebrovascular system substantially contribute to the pathogenesis of age-related cognitive impairment and Alzheimer’s disease (AD). Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid-β (Aβ) in the leptomeningeal and cortical arteries and is highly prevalent in AD, affecting over 90% of cases. While the ε4 allele of apolipoprotein E (APOE) represents the strongest genetic risk factor for AD, it is also associated with cerebrovascular dysregulations. APOE plays a crucial role in brain lipid transport, particularly in the trafficking of cholesterol and phospholipids. Lipid metabolism is increasingly recognized as a critical factor in AD pathogenesis. However, the precise mechanism by which APOE influences cerebrovascular lipid signatures in AD brains remains unclear. In this study, we conducted non-targeted lipidomics on cerebral vessels isolated from the middle temporal cortex of 89 postmortem human AD brains, representing varying degrees of CAA and different APOE genotypes: APOE ε2/ε3 (N = 9), APOE ε2/ε4 (N = 14), APOE ε3/ε3 (N = 21), APOE ε3/ε4 (N = 23), and APOE ε4/ε4 (N = 22). Lipidomics detected 10 major lipid classes with phosphatidylcholine (PC) and phosphatidylethanolamine (PE) being the most abundant lipid species. While we observed a positive association between age and total acyl-carnitine (CAR) levels (p = 0.0008), the levels of specific CAR subclasses were influenced by the APOE ε4 allele. Notably, APOE ε4 was associated with increased PE (p = 0.049) and decreased sphingomyelin (SM) levels (p = 0.028) in the cerebrovasculature. Furthermore, cerebrovascular Aβ40 and Aβ42 levels showed associations with sphingolipid levels including SM (p = 0.0079) and ceramide (CER) (p = 0.024). Weighted correlation network analysis revealed correlations between total tau and phosphorylated tau and lipid clusters enriched for PE plasmalogen and lysoglycerophospholipids. Taken together, our results suggest that cerebrovascular lipidomic profiles offer novel insights into the pathogenic mechanisms of AD, with specific lipid alterations potentially serving as biomarkers or therapeutic targets for AD.

People with type 1 or type 2 diabetes mellitus (T1DM or T2DM) often experience cognitive impairment. We profiled cells in the nucleus basalis of Meynert (NBM) in postmortem human brain tissue to investigate the neuropathological changes. Sixty-eight postmortem NBM samples were grouped as T1DM, T2DM, and controls without diabetes, with Braak stage 0–II or III–VI. T1DM subjects had only Braak stage 0–II and were thus compared only to controls with a similar Braak stage and not subjects with Braak stage III–VI. We analyzed neurons expressing choline acetyltransferase (ChAT), phosphorylated tau, amyloid-beta, glial cells, and vasculature with their respective markers. We found significantly lower neuronal expression of ChAT in T1DM individuals than in controls and T2DM individuals with Braak stage 0–II. Later-stage hyperphosphorylated tau levels were higher in T2DM compared to controls with Braak stage III–VI. Our results suggest that reduced acetylcholine production by NBM neurons may underlie the cognitive complaints of people with T1DM. In contrast, T2DM may exacerbate neuropathological changes associated with Alzheimer’s disease-like alterations.

Tau hyperphosphorylation, a key neuropathological feature of tauopathies such as Alzheimer’s disease (AD), also occurs physiologically during mammalian hibernation and is fully reversed upon arousal, offering a unique translational model to study tau metabolism. However, limited data exist on insoluble and soluble tau alterations during hibernation and on patterns of tau fragment concentrations in the hibernating mammalian brain. We quantified tau biomarkers in plasma samples from ten free-ranging brown bears (Ursus arctos), captured during both their active summer period and hibernation in the winter, using clinically validated immunoassays and immunoprecipitation mass spectrometry (IP-MS) techniques. We also analyzed brain tissue from ten golden Syrian hamsters (Mesocricetus auratus) subjected to induced torpor (hibernation) versus euthermic (non-hibernating) states by quantifying multiple phosphorylated and non-phosphorylated tau peptides with an IP-MS method previously applied in human brain tissue. In brown bears, plasma levels of phosphorylated tau (p-tau) biomarkers p-tau181 and p-tau217 significantly increased during hibernation compared to summer (median increases of 362% and 294% by IP-MS, respectively), with similar increases found with immunoassays. Additional plasma p-tau biomarkers associated with AD pathology, including p-tau205 and p-tau231, were also increased during bear hibernation. In hamster brains, p-tau217, and p-tau231 were similarly elevated during torpor, while tau fragments from the microtubule-binding region (MTBR), associated with tangle aggregation, were not increased. In contrast, brain tissue from n = 10 AD patients, analyzed with the same IP-MS method, exhibited striking increases in p-tau (~ 50,000% for p-tau217) and MTBR fragments (~ 20,000% for MTBR tau354-369) compared with n = 10 human controls. We show that hibernation-linked tau hyperphosphorylation involves some of the same phospho-sites altered in AD, but occurs without MTBR tau aggregation. This highlights hibernation as a reversible, non-pathological model to study tau biology and mechanisms underlying AD due to its reversibility and lack of tau aggregation despite hyperphosphorylation in key AD tau phospho-sites.

DNA methylation-based classification using the Heidelberg Classifier is a state-of-the-art data-driven method for molecular diagnosis of central nervous system (CNS) tumors. However, many pediatric low-grade glioma (pLGG) samples fail to yield a confident methylation-based classification, often suspected due to low tumor cell content. Here, we present a rapid, reference-based in silico purification framework that systematically removes the epigenetic signatures of five non-malignant cell types—microglia, monocytes, neutrophils, T cells, and neurons—from tumor profiles to enable classification of previously non-classifiable pLGG samples. To validate our approach, we analyzed paired DNA methylation profiles from the same biopsy, where one was initially classifiable and the other was not. After purification, predictions for all newly classifiable samples matched the classification of their corresponding initially classifiable counterparts (9/9, 100%). Application of our method to two independent pLGG cohorts allowed confident classification in 24.1% (26/108) and 22.7% (5/22) of previously non-classifiable cases. In conclusion, our in silico purification framework enables confident classification of previously non-classifiable pLGG samples, supporting accurate molecular diagnosis and timely clinical decision-making, and can seamlessly be integrated into current classification workflows. Its independence from tumor type, classifier, and reference signatures further suggests the potential for broader application to other low-purity tumor types.

Chronic-inflammatory demyelinating polyneuropathy (CIDP) is a rare immune-mediated polyneuropathy causing substantial disability. While both cell-mediated and humoral mechanisms contribute to CIDP, the role of complement remains poorly understood. Considering the rise of complement-targeted treatment, it is crucial to examine the role of complement in CIDP. In this cross-sectional, study, sural nerve biopsies from 55 CIDP patients were analyzed using histopathology, gene- and protein-based techniques, comparing them to two non-diseased controls (NDCs), as well as 8 patients with hereditary neuropathy (HN) and idiopathic axonal neuropathy (IPN). Overall, 94% (n = 52) revealed abnormal and prominent deposition of terminal complement complex C5b-9 on endoneurial capillaries. Patients with significant complement deposition presented with a progressive disease course (n = 52) and the number and distribution of infiltrating CD8 + T cells and CD68 + macrophages, since a basic immunological paradigm holds that those two may form an immunological synapse, correlated with clinical disease severity as measured by inflammatory neuropathy cause and treatment sensory sum (INCAT) score (p < 0.001). Furthermore, changes in abundances of complement proteins as unveiled by untargeted proteomics accord with changes on transcript level as identified by targeted gene expression studies. In contrast, there was no complement deposition in NDC nor DC. This study provides an extensive evaluation of sural nerve specimens of CIDP patients finding a marked involvement of complement supporting the postulated concept of complement mediated demyelination in CIDP. Our results support the approach of targeting the complement system as a new and promising therapeutic strategy—at least in a subgroup of CIDP. Further research is warranted to unravel the functional implications and role of complement in CIDP progression and optimize patient care. Clinical Trial Registration: The study is registered under the German clinical trial registry (https://www.drks.de), DRKS0003245.

Oligodendroglial alpha-synuclein (aSyn) deposits are a key feature in the atypical parkinsonian disorder, multiple system atrophy (MSA) linked to profound myelin loss and neurodegeneration while precise cellular and molecular mechanisms remain unclear. We generated human oligodendrocytes (hOLs) from induced pluripotent stem cells to investigate the impact of aSyn on oligodendroglial morphology, differentiation, and function. We observed an aSyn-induced myelinogenic dysfunction characterized by impaired oligodendroglial process outgrowth, altered cell shape, and increased perinuclear accumulation of the tubulin polymerization promoting protein TPPP/p25α. These changes were associated with a reduced capacity to ensheath axons and were linked to compromised actin remodeling machinery. Actin imbalances were confirmed in post-mortem putaminal tissue from MSA patients. Treatment with a rho-associated protein kinase inhibitor rescued oligodendroglial process formation and improved ensheathment in aSyn-expressing hOLs. Our work emphasizes the aSyn-mediated interference with actin dynamics as a key pathogenic mechanism in MSA, pointing toward a novel therapeutic target for improving myelin maintenance.

The SH3PXD2A-HTRA1 fusion gene has recently been identified in a subset of schwannomas, but its frequency and clinical significance remain unclear. This study aimed to investigate the prevalence and clinical relevance of this fusion gene in intracranial schwannomas, stratified by cranial nerve of origin. We retrospectively investigated the fusion gene in 237 intracranial schwannomas. Fusion detection was performed using reverse transcription polymerase chain reaction and confirmed by Sanger sequencing. Somatic NF2 status was evaluated using whole-genome sequencing or Merlin immunohistochemistry in fusion gene-positive cases. Clinical characteristics and postoperative tumor recurrence were compared between fusion gene-positive and fusion gene-negative tumors, and subgroup analyses were performed by cranial nerve of origin. The fusion gene was detected in 30 tumors (12.7%), with the highest frequency observed in trigeminal schwannomas (25.9%). Tumors classified as recurrent at baseline (odds ratio [OR], 3.74; P = 0.012), trigeminal nerve origin (OR, 2.88; P = 0.042), and intratumoral hemorrhage (OR, 18.61; P = 0.028) were significantly associated with fusion gene-positive tumors. In the trigeminal schwannomas, fusion gene-positive cases were significantly younger (P = 0.029). In the vestibular schwannomas, recurrence status was found to be independently associated with positive fusion gene status (OR, 4.53; P = 0.010). Furthermore, even after gross or nearly total resection, fusion gene-positive vestibular schwannomas exhibited a significantly higher incidence of recurrence after surgery (P = 0.046). Only 33% of fusion gene-positive tumors indicated somatic NF2 alteration. The SH3PXD2A-HTRA1 fusion gene may define a molecular subset of intracranial schwannomas with distinctive anatomical distribution and biological aggressiveness. It may contribute to tumorigenesis through an alternative pathway independent of NF2. Our findings provide a basis for future clinical investigations.