Wim Van Hecke

Predominance of Nonatherosclerotic Internal Elastic Lamina Calcification in the Intracranial Internal Carotid Artery

Background and Purpose— Calcification of the intracranial internal carotid artery (iICA) is an independent risk factor for stroke. These calcifications are generally seen as manifestation of atherosclerosis, but histological investigations are limited. The aim of this study is to determine whether calcifications in the iICA are present in atherosclerotic plaques, or in other parts of the arterial wall. Methods— Thirty-nine iICAs were histologically assessed, using digital microscopy to quantify the amount of calcification in the different layers of the arterial wall. Results— Calcifications were found in the intima, around the internal elastic lamina and in the medial layer of the arterial wall. In 71% of the arteries, internal elastic lamina calcification contributed most to the total calcified cross-sectional surface area. Internal elastic lamina calcification was unrelated to the occurrence of atherosclerotic intimal lesions. Intimal calcifications were most often associated with atherosclerotic lesions, but also many noncalcified atherosclerotic lesions were found. Conclusions— In the iICA, calcifications are predominantly present around the internal elastic lamina, suggesting that this nonatherosclerotic type of calcification contributes to the previously observed increased risk of stroke in patients with iICA calcifications.

Specific pattern of maturation and differentiation in the formation of cortical tubers in tuberous sclerosis complex (TSC): evidence from layer-specific marker expression

BackgroundTuberous sclerosis complex (TSC) is a multisystem disorder that results from mutations in the TSC1 or TSC2 genes, leading to constitutive activation of the mammalian target of rapamycin (mTOR) signaling pathway. Cortical tubers represent typical lesions of the central nervous system (CNS) in TSC. The pattern of cortical layering disruption observed in brain tissue of TSC patients is not yet fully understood, and little is known about the origin and phenotype of individual abnormal cell types recognized in tubers.MethodsIn the present study, we aimed to characterize dysmorphic neurons (DNs) and giant cells (GCs) of cortical tubers using neocortical layer-specific markers (NeuN, SMI32, Tbr1, Satb2, Cux2, ER81, and RORβ) and to compare the features with the histo-morphologically similar focal cortical dysplasia (FCD) type IIb. We studied a cohort of nine surgically resected cortical tubers, five FCD type IIb, and four control samples using immunohistochemistry and in situ hybridization.ResultsCortical tuber displayed a prominent cell loss in all cortical layers. Moreover, we observed altered proportions of layer-specific markers within the dysplastic region. DNs, in both tubers and FCD type IIb, were found positive for different cortical layer markers, regardless of their laminar location, and their immunophenotype resembles that of cortical projection neurons.ConclusionsThese findings demonstrate that, similar to FCD type IIb, cortical layering is markedly disturbed in cortical tubers of TSC patients. Distribution of these disturbances is comparable in all tubers and suggests a dysmaturation affecting early and late migratory patterns, with a more severe impairment of the late stage of maturation.

Computed Tomographic Distinction of Intimal and Medial Calcification in the Intracranial Internal Carotid Artery

Background Intracranial internal carotid artery (iICA) calcification is associated with stroke and is often seen as a proxy of atherosclerosis of the intima. However, it was recently shown that these calcifications are predominantly located in the tunica media and internal elastic lamina (medial calcification). Intimal and medial calcifications are thought to have a different pathogenesis and clinical consequences and can only be distinguished through ex vivo histological analysis. Therefore, our aim was to develop CT scoring method to distinguish intimal and medial iICA calcification in vivo. Methods First, in both iICAs of 16 cerebral autopsy patients the intimal and/or medial calcification area was histologically assessed (142 slides). Brain CT images of these patients were matched to the corresponding histological slides to develop a CT score that determines intimal or medial calcification dominance. Second, performance of the CT score was assessed in these 16 patients. Third, reproducibility was tested in a separate cohort. Results First, CT features of the score were circularity (absent, dot(s), <90°, 90–270° or 270–360°), thickness (absent, ≥1.5mm, or <1.5mm), and morphology (indistinguishable, irregular/patchy or continuous). A high sum of features represented medial and a lower sum intimal calcifications. Second, in the 16 patients the concordance between the CT score and the dominant calcification type was reasonable. Third, the score showed good reproducibility (kappa: 0.72 proportion of agreement: 0.82) between the categories intimal, medial or absent/indistinguishable. Conclusions The developed CT score shows good reproducibility and can differentiate reasonably well between intimal and medial calcification dominance in the iICA, allowing for further (epidemiological) studies on iICA calcification.

Pediatric Primitive Neuroectodermal Tumors of the Central Nervous System Differentially Express Granzyme Inhibitors.

Background Central nervous system (CNS) primitive neuroectodermal tumors (PNETs) are malignant primary brain tumors that occur in young infants. Using current standard therapy, up to 80% of the children still dies from recurrent disease. Cellular immunotherapy might be key to improve overall survival. To achieve efficient killing of tumor cells, however, immunotherapy has to overcome cancer-associated strategies to evade the cytotoxic immune response. Whether CNS-PNETs can evade the immune response remains unknown. Methods We examined by immunohistochemistry the immune response and immune evasion strategies in pediatric CNS-PNETs. Results Here, we show that CD4+, CD8+, γδ-T-cells, and Tregs can infiltrate pediatric CNS-PNETs, although the activation status of cytotoxic cells is variable. Pediatric CNS-PNETs evade immune recognition by downregulating cell surface MHC-I and CD1d expression. Intriguingly, expression of SERPINB9, SERPINB1, and SERPINB4 is acquired during tumorigenesis in 29%, 29%, and 57% of the tumors, respectively. Conclusion We show for the first time that brain tumors express direct granzyme inhibitors (serpins) as a potential mechanism to overcome cellular cytotoxicity, which may have consequences for cellular immunotherapy.

Prognostic relevance of tumor-infiltrating lymphocytes and immune checkpoints in pediatric medulloblastoma

ABSTRACT Pediatric medulloblastomas are the most frequently diagnosed embryonal tumors of the central nervous system. Current therapies cause severe neurological and cognitive side effects including secondary malignancies. Cellular immunotherapy might be key to improve survival and to avoid morbidity. Efficient killing of tumor cells using immunotherapy requires to overcome cancer-associated strategies to evade cytotoxic immune responses. Here, we examined the immune response and immune evasion strategies in pediatric medulloblastomas. Cytotoxic T-cells, infiltrating medulloblastomas with variable activation status, showed no correlation with overall survival of the patients. We found limited numbers of PD1+ T-cells and complete absence of PD-L1 on medulloblastomas. Medulloblastomas downregulated immune recognition molecules MHC-I and CD1 d. Intriguingly, expression of granzyme inhibitors SERPINB1 and SERPINB4 was acquired in 23% and 50% of the tumors, respectively. Concluding, pediatric medulloblastomas exploit multiple immune evasion strategies to overcome immune surveillance. Absence of PD-L1 expression in medulloblastoma suggest limited or no added value for immunotherapy with PD1/PD-L1 blockers.

miR147b: A novel key regulator of interleukin 1 beta-mediated inflammation in human astrocytes

Astrocytes are important mediators of inflammatory processes in the brain and seem to play an important role in several neurological disorders, including epilepsy. Recent studies show that astrocytes produce several microRNAs, which may function as crucial regulators of inflammatory pathways and could be used as therapeutic target. We aim to study which miRNAs are produced by astrocytes during IL‐1β mediated inflammatory conditions in vitro, as well as their functional role and to validate these findings in human epileptogenic brain tissue. Sequencing was used to assess miRNA and mRNA expression in IL‐1β‐stimulated human fetal astrocyte cultures. miRNAs were overexpressed in cell cultures using miRNA mimics. Expression of miRNAs in resected brain tissue from patients with tuberous sclerosis complex or temporal lobe epilepsy with hippocampal sclerosis was examined using in situ hybridization. Two differentially expressed miRNAs were found: miR146a and miR147b, which were associated with increased expression of genes related to the immune/inflammatory response. As previously reported for miR146a, overexpression of miR147b reduced the expression of the pro‐inflammatory mediators IL‐6 and COX‐2 after IL‐1β stimulation in both astrocyte and tuberous sclerosis complex cell cultures. miR146a and miR147b overexpression decreased proliferation of astrocytes and promoted neuronal differentiation of human neural stem cells. Similarly to previous evidence for miR146a, miR147b was increased expressed in astrocytes in epileptogenic brain. Due to their anti‐inflammatory effects, ability to restore aberrant astrocytic proliferation and promote neuronal differentiation, miR146a and miR147b deserve further investigation as potential therapeutic targets in neurological disorders associated with inflammation, such as epilepsy.

Oncogenic role of cytomegalovirus in medulloblastoma

Medulloblastoma is the most common solid tumor among children. Current therapeutic strategies for this malignancy include surgical resection, radiation therapy and chemotherapy. However, these treatments are accompanied with serious side effects such as neurological complications and psychosocial problems, due to the severity of treatment on the developing nervous system. To solve this problem, novel therapeutic approaches are currently being investigated. One of them is targeting human cytomegalovirus in medulloblastoma cancer cells. However, this approach is still under debate, since the presence of cytomegalovirus in medulloblastomas remains controversial. In this review, we discuss the current controversies on the role of cytomegalovirus in medulloblastoma oncogenesis and the potential of cytomegalovirus as a novel (immuno)therapeutic target.

The amount of calcifications in pseudoxanthoma elasticum patients is underestimated in computed tomographic imaging; a post-mortem correlation of histological and computed tomographic findings in two cases

ObjectivesPseudoxanthoma elasticum (PXE) is a rare genetic disorder, characterised by elastic fibre degeneration and calcifications in multiple organ systems. Computed tomography (CT) imaging is a potential method to monitor disease progression in PXE patients; however, this method has not been validated. The aim of this study was to correlate histological and computed tomographic findings in PXE patients to investigate the ability of CT scanning to detect these alterations.MethodsPost mortem total body CT scans were obtained from two PXE patients (a 69-year-old male and 77-year-old female). Autopsy was performed, and 38 tissue samples of the first and 45 tissue samples of the second patient were extensively investigated histologically. The findings were compared with the CT scans.ResultsDegenerated and calcified elastic fibres and calcifications were histologically found in the skin, subcutaneous fat, heart, arteries and pleura and around the oesophagus. On CT imaging only the intradermal alterations of the skin and the larger vascular calcifications were detected. The smaller PXE-related abnormalities were not visible on CT.ConclusionsWith CT imaging vascular calcifications and skin alterations can be monitored in PXE patients. However, many of the subtle PXE-related abnormalities found in other organ systems during the autopsy were not visualised by CT scans. Furthermore, we extended the current knowledge on the disease location of PXE with subcutaneous, oesophageal and pleural lesions.Teaching Points• CT can be used to monitor gross vascular calcifications in PXE patients.• Many subtle PXE-related abnormalities are not visualised by CT scans.• PXE-related alterations can also be found in oesophagus, pleura and subcutaneous fat.

Data on vessel wall thickness measurements of intracranial arteries derived from human circle of Willis specimens

In this article, we report data on vessel wall thickness parameters derived from different arterial segments of the circle of Willis and its primary branches in patients with and without cerebrovascular disease. Also data on inter-rater reliability and agreement of the derived vessel wall parameters are reported. For further interpretation and discussion please refer to the research article “ex vivo vessel wall thickness measurements of the human circle of Willis using 7T MRI” (Harteveld et al., in press) [1].

Oxidative stress and inflammation in a spectrum of epileptogenic cortical malformations: molecular insights into their interdependence

Oxidative stress (OS) occurs in brains of patients with epilepsy and coincides with brain inflammation, and both phenomena contribute to seizure generation in animal models. We investigated whether expression of OS and brain inflammation markers co‐occurred also in resected brain tissue of patients with epileptogenic cortical malformations: hemimegalencephaly (HME), focal cortical dysplasia (FCD) and cortical tubers in tuberous sclerosis complex (TSC). Moreover, we studied molecular mechanisms linking OS and inflammation in an in vitro model of neuronal function. Untangling interdependency and underlying molecular mechanisms might pose new therapeutic strategies for treating patients with drug‐resistant epilepsy of different etiologies. Immunohistochemistry was performed for specific OS markers xCT and iNOS and brain inflammation markers TLR4, COX‐2 and NF‐κB in cortical tissue derived from patients with HME, FCD IIa, IIb and TSC. Additionally, we studied gene expression of these markers using the human neuronal cell line SH‐SY5Y in which OS was induced using H2O2. OS markers were higher in dysmorphic neurons and balloon/giant cells in cortex of patients with FCD IIb or TSC. Expression of OS markers was positively correlated to expression of brain inflammation markers. In vitro, 100 µM, but not 50 µM, of H2O2 increased expression of TLR4, IL‐1β and COX‐2. We found that NF‐κB signaling was activated only upon stimulation with 100 µM H2O2 leading to upregulation of TLR4 signaling and IL‐1β. The NF‐κB inhibitor TPCA‐1 completely reversed this effect. Our results show that OS positively correlates with neuroinflammation and is particularly evident in brain tissue of patients with FCD IIb and TSC. In vitro, NF‐κB is involved in the switch to an inflammatory state after OS. We propose that the extent of OS can predict the neuroinflammatory state of the brain. Additionally, antioxidant treatments may prevent the switch to inflammation in neurons thus targeting multiple epileptogenic processes at once.