Impairment of tight junctions and glucose transport in endothelial cells of human cerebral cavernous malformations

Profiling Tight Junction Protein Expression in Brain Vascular Malformations

Recent studies suggest that blood-brain barrier (BBB) disruption plays a key role in the clinical course and bleeding risk of brain arteriovenous malformations (bAVMs). The tight junctions (TJs) are complex endothelial transmembrane proteins with a significant physical contribution to BBB disruption. In this study, we hypothesized that bAVMs display a different TJ pattern than other vascular malformations and normal brain tissue. We studied the expression of claudin-5 and occludin as essential factors for functional TJs. Human specimens of surgically resected cavernomas (CCMs) (n = 9), bAVMs (n = 17), and perilesional brain parenchyma (6 from CCMs and 16 from bAVM patients) were analyzed via immunofluorescence staining, transmission electron microscopy (TEM), and Western blot tests. Compared to perilesional parenchyma, bAVMs showed a significant decrease in TJ protein expression, and these alterations were more apparent in ruptured bAVMs than in unruptured bAVMs or CCMs. TEM images provided evidence of disrupted connectivity between endothelial cells of bAVMs. This is the first clinical investigation that studies the expression of TJs in human bAVMs and their surrounding parenchyma. Despite the limitations of the sample size, we found significant differences in the expression and composition of TJs in bAVMs when compared to surrounding parenchyma and other vascular lesions such as CCMs. These results add further evidence to the role of BBB disruption in the clinical course of bAVM. A deeper understanding of these mechanisms may lead to the development of new therapeutic targets and management strategies for bAVMs.

Tailored management of cavernous malformations in women: considerations and strategies-a review

Purpose of review

Cavernous malformations (CM) are vascular lesions in the brain and spinal cord, characterized by clusters of endothelial-lined caverns lacking proper tight junctions. These malformations may be discovered incidentally or present with symptoms such as headaches, focal neurologic deficits, or seizures, with or without hemorrhage. This review focuses on non-surgical management considerations important for women with CM, who face challenges related to pregnancy, exogenous hormone use, anticonvulsive therapy, bone health, and mental health.

Recent findings

Emerging evidence suggests that both estrogen and progesterone may influence CM lesion behavior. Exogenous hormones, including those in oral contraceptives and oral hormone replacement therapy, indicate an elevated risk of symptomatic hemorrhage (SH) and may also influence seizure frequency and severity, particularly in women taking antiseizure medications (ASMs). Data suggest that the risk of CM hemorrhage during pregnancy is similar to the risk when not pregnant, although limitations to these studies will be reviewed.

Summary

This review synthesizes the current literature on the interplay between estrogen and progesterone and CM lesion behavior, highlighting the importance of gender- and sex-specific factors in clinical decision-making. Special attention is given to the implications of exogenous hormone use, seizure management, and the psychological well-being of women with CM, underscoring the need for a multidisciplinary approach tailored to the unique needs of this patient population.

Diabetes compromises tight junction protein claudin 14 in the urinary bladder

Infections are common in patients with diabetes. Moreover, increasing incidence of antibiotic resistance impedes the complete bacterial clearance and calls for alternative treatment strategies. Along with antibacterial resistance, compromised host conditions create a favorable condition for the disease progression. In particular, cell junction proteins are of major importance as they contribute to a tight cell barrier, protecting against invading pathogens. However, the impact of high glucose on cell junction proteins has received little attention in the urinary bladder but merits closer investigation. Here, we report that during diabetes the expression of cell junction protein, claudin 14 is compromised in the human urine exfoliated cells and in the urinary bladder of type 2 diabetic mouse. Further in vitro analysis confirmed a direct correlation of lower intracellular calcium levels with claudin 14 expression in high glucose-treated human uroepithelial cells. Moreover, external calcium supplementation in high glucose-treated cells significantly affected the cell migration and restored the claudin 14 expression through focal adhesion and β-1 integrins. Strengthening the epithelial barrier is essential, especially in individuals with diabetes where basal calcium levels could contribute.

20 kDa isoform of connexin-43 augments spatial reorganization of the brain endothelial junctional complex and lesion leakage in cerebral cavernous malformation type-3

Cerebral cavernous malformation type-3 (CCM3) is a type of brain vascular malformation caused by mutations in programmed cell death protein-10 (PDCD10). It is characterized by early life occurrence of hemorrhagic stroke and profound blood-brain barrier defects. The pathogenic mechanisms responsible for microvascular hyperpermeability and lesion progression in CCM3 are still largely unknown. The current study examined brain endothelial barrier structural defects formed in the absence of CCM3 in vivo and in vitro that may lead to CCM3 lesion leakage. We found significant upregulation of a 20 kDa isoform of connexin 43 (GJA1-20 k) in brain endothelial cells (BEC) in both non-leaky and leaky lesions, as well as in an in vitro CCM3 knockdown model (CCM3KD-BEC). Morphological, biochemical, FRET, and FRAP analyses of CCM3KD-BEC found GJA1-20 k regulates full-length GJA1 biogenesis, prompting uncontrolled gap junction growth. Furthermore, by binding to a tight junction scaffolding protein, ZO-1, GJA1-20 k interferes with Cx43/ZO-1 interactions and gap junction/tight junction crosstalk, promoting ZO-1 dissociation from tight junction complexes and diminishing claudin-5/ZO-1 interaction. As a consequence, the tight junction complex is destabilized, allowing "replacement" of tight junctions with gap junctions leading to increased brain endothelial barrier permeability. Modifying cellular levels of GJA1-20 k rescued brain endothelial barrier integrity re-establishing the spatial organization of gap and tight junctional complexes. This study highlights generation of potential defects at the CCM3-affected brain endothelial barrier which may underlie prolonged vascular leakiness.

NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression

The loss function of cerebral cavernous malformation (CCM) genes leads to most CCM lesions characterized by enlarged leaking vascular lesions in the brain. Although we previously showed that NOGOB receptor (NGBR) knockout in endothelial cells (ECs) results in cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NGBR regulates CCM1/2 expression has not been elucidated. Here, we show that genetic depletion of Ngbr in ECs at both postnatal and adult stages results in CCM1/2 expression deficiency and cerebrovascular lesions such as enlarged vessels, blood-brain-barrier hyperpermeability, and cerebral hemorrhage. To reveal the molecular mechanism, we used RNA-sequencing analysis to examine changes in the transcriptome. Surprisingly, we found that the acetyltransferase HBO1 and histone acetylation were downregulated in NGBR-deficient ECs. The mechanistic studies elucidated that NGBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NGBR impairs the binding of HBO1 and acetylated histone H4K5 and H4K12 on the promotor of the CCM1 and CCM2 genes. Our findings on epigenetic regulation of CCM1 and CCM2 that is modulated by NGBR and HBO1-mediated histone H4 acetylation provide a perspective on the pathogenesis of sporadic CCMs.

Is Location Everything? Regulation of the Endothelial CCM Signaling Complex

Recent advances have steadily increased the number of proteins and pathways known to be involved in the development of cerebral cavernous malformation (CCM). Our ability to synthesize this information into a cohesive and accurate signaling model is limited, however, by significant gaps in our knowledge of how the core CCM proteins, whose loss of function drives development of CCM, are regulated. Here, we review what is known about the regulation of the three core CCM proteins, the scaffolds KRIT1, CCM2, and CCM3, with an emphasis on binding interactions and subcellular location, which frequently control scaffolding protein function. We highlight recent work that challenges the current model of CCM complex signaling and provide recommendations for future studies needed to address the large number of outstanding questions.

Bringing CCM into a dish: cell culture models for cerebral cavernous malformations

Cerebral cavernous malformations (CCMs) are vascular lesions that can cause severe neurological complications due to intracranial hemorrhage. Although the CCM disease genes, CCM1, CCM2, and CCM3, have been known for more than 15 years now, our understanding of CCM pathogenesis is still incomplete. CCM research currently focuses on three main disease mechanisms: (1) clonal expansion of endothelial cells with biallelic inactivation of CCM1, CCM2, or CCM3, (2) recruitment of cells with preserved CCM protein expression into the growing lesion, and (3) disruption of endothelial cell-cell junctions in CCMs. We here describe novel CRISPR/Cas9-based in vitro models of CCM and discuss their strengths and limitations in the context of high-throughput drug screening and repurposing approaches.

Inactivation of Cerebral Cavernous Malformation Genes Results in Accumulation of von Willebrand Factor and Redistribution of Weibel-Palade Bodies in Endothelial Cells

Cerebral cavernous malformations are slow-flow thrombi-containing vessels induced by two-step inactivation of the CCM1, CCM2 or CCM3 gene within endothelial cells. They predispose to intracerebral bleedings and focal neurological deficits. Our understanding of the cellular and molecular mechanisms that trigger endothelial dysfunction in cavernous malformations is still incomplete. To model both, hereditary and sporadic CCM disease, blood outgrowth endothelial cells (BOECs) with a heterozygous CCM1 germline mutation and immortalized wild-type human umbilical vein endothelial cells were subjected to CRISPR/Cas9-mediated CCM1 gene disruption. CCM1 -/- BOECs demonstrated alterations in cell morphology, actin cytoskeleton dynamics, tube formation, and expression of the transcription factors KLF2 and KLF4. Furthermore, high VWF immunoreactivity was observed in CCM1 -/- BOECs, in immortalized umbilical vein endothelial cells upon CRISPR/Cas9-induced inactivation of either CCM1, CCM2 or CCM3 as well as in CCM tissue samples of familial cases. Observer-independent high-content imaging revealed a striking reduction of perinuclear Weibel-Palade bodies in unstimulated CCM1 -/- BOECs which was observed in CCM1 +/- BOECs only after stimulation with PMA or histamine. Our results demonstrate that CRISPR/Cas9 genome editing is a powerful tool to model different aspects of CCM disease in vitro and that CCM1 inactivation induces high-level expression of VWF and redistribution of Weibel-Palade bodies within endothelial cells.

Fibronectin rescues aberrant phenotype of endothelial cells lacking either CCM1, CCM2 or CCM3

Loss-of-function variants in CCM1/KRIT1, CCM2, and CCM3/PDCD10 are associated with autosomal dominant cerebral cavernous malformations (CCMs). CRISPR/Cas9-mediated CCM3 inactivation in human endothelial cells (ECs) has been shown to induce profound defects in cell-cell interaction as well as actin cytoskeleton organization. We here show that CCM3 inactivation impairs fibronectin expression and consequently leads to reduced fibers in the extracellular matrix. Despite the complexity and high molecular weight of fibronectin fibrils, our in vitro model allowed us to reveal that fibronectin supplementation restored aberrant spheroid formation as well as altered EC morphology, and suppressed actin stress fiber formation. Yet, fibronectin replacement neither enhanced the stability of tube-like structures nor inhibited the survival advantage of CCM3^-/- ECs. Importantly, CRISPR/Cas9-mediated introduction of biallelic loss-of-function variants into either CCM1 or CCM2 demonstrated that the impaired production of a functional fibronectin matrix is a common feature of CCM1-, CCM2-, and CCM3-deficient ECs.

Targeting miR-27a/VE-cadherin interactions rescues cerebral cavernous malformations in mice

Cerebral cavernous malformations (CCMs) are vascular lesions predominantly developing in the central nervous system (CNS), with no effective treatments other than surgery. Loss-of-function mutation in CCM1/krev interaction trapped 1 (KRIT1), CCM2, or CCM3/programmed cell death 10 (PDCD10) causes lesions that are characterized by abnormal vascular integrity. Vascular endothelial cadherin (VE-cadherin), a major regulator of endothelial cell (EC) junctional integrity is strongly disorganized in ECs lining the CCM lesions. We report here that microRNA-27a (miR-27a), a negative regulator of VE-cadherin, is elevated in ECs isolated from mouse brains developing early CCM lesions and in cultured ECs with CCM1 or CCM2 depletion. Furthermore, we show miR-27a acts downstream of kruppel-like factor (KLF)2 and KLF4, two known key transcription factors involved in CCM lesion development. Using CD5-2 (a target site blocker [TSB]) to prevent the miR-27a/VE-cadherin mRNA interaction, we present a potential therapy to increase VE-cadherin expression and thus rescue the abnormal vascular integrity. In CCM1- or CCM2-depleted ECs, CD5-2 reduces monolayer permeability, and in Ccm1 heterozygous mice, it restores dermal vessel barrier function. In a neonatal mouse model of CCM disease, CD5-2 normalizes vasculature and reduces vascular leakage in the lesions, inhibits the development of large lesions, and significantly reduces the size of established lesions in the hindbrain. Furthermore, CD5-2 limits the accumulation of inflammatory cells in the lesion area. Our work has established that VE-cadherin is a potential therapeutic target for normalization of the vasculature and highlights that targeting miR-27a/VE-cadherin interaction by CD5-2 is a potential novel therapy for the devastating disease, CCM.

Cerebral cavernous malformation (CCM) is a disease for which, hitherto, surgery has been the only option. This study shows that a potential therapeutic, CD5-2, inhibits lesion development and vascular leak in the brains of CCM neonatal mice by targeting the endothelial cell–specific adhesion molecule VE-cadherin and restoring the vascular integrity of CCM lesions.

Cerebral Cavernous Malformation Proteins in Barrier Maintenance and Regulation

Cerebral cavernous malformation (CCM) is a disease characterized by mulberry shaped clusters of dilated microvessels, primarily in the central nervous system. Such lesions can cause seizures, headaches, and stroke from brain bleeding. Loss-of-function germline and somatic mutations of a group of genes, called CCM genes, have been attributed to disease pathogenesis. In this review, we discuss the impact of CCM gene encoded proteins on cellular signaling, barrier function of endothelium and epithelium, and their contribution to CCM and potentially other diseases.

Library Preparation for Small RNA Transcriptome Sequencing in Patients Affected by Cerebral Cavernous Malformations

Small RNA sequencing by Illumina's Next Generation technology has revolutionized the transcriptome analysis by facilitating massive parallel sequencing of RNA molecules at low cost. Illumina's Next Generation RNA sequencing is ideal for profiling small RNA (microRNAs, snoRNAs, and piRNAs) libraries in the identification of novel biomarkers for better clinical diagnosis. This method offers significant advantages when compared to microarray analysis with the ability to identify novel transcripts, higher sensitivity, specificity, and detection of rare and low-abundance transcripts. Small RNAs, including microRNAs and snoRNAs, belong to the class of small non-coding RNAs with 50-200 nucleotides in length and are involved in post-transcriptional regulation of gene expression. Executing Illumina's Next Generation Sequencing technology, we have recently deciphered microRNAs and snoRNAs expressed in cerebral cavernous malformations (CCMs). Small RNA library preparation is a prerequisite step prior to RNA sequencing for the identification of microRNAs and snoRNAs. Here, we describe stepwise small RNA library preparation starting from total RNA isolated from CCMs patient until library validation using the Illumina^® TruSeq^® Small RNA Sample preparation kit. We believe this method will shed light into the functional identification of other novel small non-coding RNAs in CCMs that awaits discovery.

NIR-II window tracking of hyperglycemia induced intracerebral hemorrhage in cerebral cavernous malformation deficient mice

Left panel: Pseudocolor map of 3 principle components from NIR-II kinetic imaging, Right panel (top to bottom): In vivo Ag₂S QD NIR-II fluorescence, ex vivo iodine micro-CT, FITC dextran perfusion, and H&E staining in control vs CCM1+/− mice brain.

Transcriptome clarifies mechanisms of lesion genesis versus progression in models of Ccm3 cerebral cavernous malformations

Cerebral cavernous malformations (CCMs) are dilated capillaries causing epilepsy and stroke. Inheritance of a heterozygous mutation in CCM3/PDCD10 is responsible for the most aggressive familial form of the disease. Here we studied the differences and commonalities between the transcriptomes of microdissected lesional neurovascular units (NVUs) from acute and chronic in vivo Ccm3/Pdcd10ECKO mice, and cultured brain microvascular endothelial cells (BMECs) Ccm3/Pdcd10ECKO.We identified 2409 differentially expressed genes (DEGs) in acute and 2962 in chronic in vivo NVUs compared to microdissected brain capillaries, as well as 121 in in vitro BMECs with and without Ccm3/Pdcd10 loss (fold change ≥ |2.0|; p < 0.05, false discovery rate corrected). A functional clustered dendrogram generated using the Euclidean distance showed that the DEGs identified only in acute in vivo NVUs were clustered in cellular proliferation gene ontology functions. The DEGs only identified in chronic in vivo NVUs were clustered in inflammation and immune response, permeability, and adhesion functions. In addition, 1225 DEGs were only identified in the in vivo NVUs but not in vitro BMECs, and these clustered within neuronal and glial functions. One miRNA mmu-miR-3472a was differentially expressed (FC = - 5.98; p = 0.07, FDR corrected) in the serum of Ccm3/Pdcd10+/- when compared to wild type mice, and this was functionally related as a putative target to Cand2 (cullin associated and neddylation dissociated 2), a DEG in acute and chronic lesional NVUs and in vitro BMECs. Our results suggest that the acute model is characterized by cell proliferation, while the chronic model showed inflammatory, adhesion and permeability processes. In addition, we highlight the importance of extra-endothelial structures in CCM disease, and potential role of circulating miRNAs as biomarkers of disease, interacting with DEGs. The extensive DEGs library of each model will serve as a validation tool for potential mechanistic, biomarker, and therapeutic targets.

Phenotypic characterization of murine models of cerebral cavernous malformations

Cerebral cavernous malformations (CCMs) are clusters of dilated capillaries that affect around 0.5% of the population. CCMs exist in two forms, sporadic and familial. Mutations in three documented genes, KRIT1(CCM1), CCM2, and PDCD10(CCM3), cause the autosomal dominant form of the disease, and somatic mutations in these same genes underlie lesion development in the brain. Murine models with constitutive or induced loss of respective genes have been applied to study disease pathobiology and therapeutic manipulations. We aimed to analyze the phenotypic characteristic of two main groups of models, the chronic heterozygous models with sensitizers promoting genetic instability, and the acute neonatal induced homozygous knockout model. Acute model mice harbored a higher lesion burden than chronic models, more localized in the hindbrain, and largely lacking iron deposition and inflammatory cell infiltrate. The chronic model mice showed a lower lesion burden localized throughout the brain, with significantly greater perilesional iron deposition, immune B- and T-cell infiltration, and less frequent junctional protein immunopositive endothelial cells. Lesional endothelial cells in both models expressed similar phosphorylated myosin light chain immunopositivity indicating Rho-associated protein kinase activity. These data suggest that acute models are better suited to study the initial formation of the lesion, while the chronic models better reflect lesion maturation, hemorrhage, and inflammatory response, relevant pathobiologic features of the human disease.

Plasma Biomarkers of Inflammation and Angiogenesis Predict Cerebral Cavernous Malformation Symptomatic Hemorrhage or Lesional Growth

RATIONALE

The clinical course of cerebral cavernous malformations is highly unpredictable, with few cross-sectional studies correlating proinflammatory genotypes and plasma biomarkers with prior disease severity.

OBJECTIVE

We hypothesize that a panel of 24 candidate plasma biomarkers, with a reported role in the physiopathology of cerebral cavernous malformations, may predict subsequent clinically relevant disease activity.

METHODS AND RESULTS

Plasma biomarkers were assessed in nonfasting peripheral venous blood collected from consecutive cerebral cavernous malformation subjects followed for 1 year after initial sample collection. A first cohort (N=49) was used to define the best model of biomarker level combinations to predict a subsequent symptomatic lesional hemorrhagic expansion within a year after the blood sample. We generated the receiver operating characteristic curves and area under the curve for each biomarker individually and each weighted linear combination of relevant biomarkers. The best model to predict lesional activity was selected as that minimizing the Akaike information criterion. In this cohort, 11 subjects experienced symptomatic lesional hemorrhagic expansion (5 bleeds and 10 lesional growths) within a year after the blood draw. Subjects had lower soluble CD14 (cluster of differentiation 14; P=0.05), IL (interleukin)-6 (P=0.04), and VEGF (vascular endothelial growth factor; P=0.0003) levels along with higher plasma levels of IL-1β (P=0.008) and soluble ROBO4 (roundabout guidance receptor 4; P=0.03). Among the 31 weighted linear combinations of these 5 biomarkers, the best model (with the lowest Akaike information criterion value, 25.3) was the weighted linear combination including soluble CD14, IL-1β, VEGF, and soluble ROBO4, predicting a symptomatic hemorrhagic expansion with a sensitivity of 86% and specificity of 88% (area under the curve, 0.90; P<0.0001). We then validated our best model in the second sequential independent cohort (N=28).

CONCLUSIONS

This is the first study reporting a predictive association between plasma biomarkers and subsequent cerebral cavernous malformation disease clinical activity. This may be applied in clinical prognostication and stratification of cases in clinical trials.

Thrombospondin1 (TSP1) replacement prevents cerebral cavernous malformations

KRIT1 mutations are the most common cause of cerebral cavernous malformation (CCM). Acute Krit1 gene inactivation in mouse brain microvascular endothelial cells (BMECs) changes expression of multiple genes involved in vascular development. These changes include suppression of Thbs1, which encodes thrombospondin1 (TSP1) and has been ascribed to KLF2- and KLF4-mediated repression of Thbs1 In vitro reconstitution of TSP1 with either full-length TSP1 or 3TSR, an anti-angiogenic TSP1 fragment, suppresses heightened vascular endothelial growth factor signaling and preserves BMEC tight junctions. Furthermore, administration of 3TSR prevents the development of lesions in a mouse model of CCM1 (Krit1ECKO ) as judged by histology and quantitative micro-computed tomography. Conversely, reduced TSP1 expression contributes to the pathogenesis of CCM, because inactivation of one or two copies of Thbs1 exacerbated CCM formation. Thus, loss of Krit1 function disables an angiogenic checkpoint to enable CCM formation. These results suggest that 3TSR, or other angiogenesis inhibitors, can be repurposed for TSP1 replacement therapy for CCMs.

Genome-Wide Sequencing Reveals MicroRNAs Downregulated in Cerebral Cavernous Malformations

Cerebral cavernous malformations (CCM) are vascular lesions associated with loss-of-function mutations in one of the three genes encoding KRIT1 (CCM1), CCM2, and PDCD10. Recent understanding of the molecular mechanisms that lead to CCM development is limited. The role of microRNAs (miRNAs) has been demonstrated in vascular pathologies resulting in loss of tight junction proteins, increased vascular permeability and endothelial cell dysfunction. Since the relevance of miRNAs in CCM pathophysiology has not been elucidated, the primary aim of the study was to identify the miRNA-mRNA expression network associated with CCM. Using small RNA sequencing, we identified a total of 764 matured miRNAs expressed in CCM patients compared to the healthy brains. The expression of the selected miRNAs was validated by qRT-PCR, and the results were found to be consistent with the sequencing data. Upon application of additional statistical stringency, five miRNAs (let-7b-5p, miR-361-5p, miR-370-3p, miR-181a-2-3p, and miR-95-3p) were prioritized to be top CCM-relevant miRNAs. Further in silico analyses revealed that the prioritized miRNAs have a direct functional relation with mRNAs, such as MIB1, HIF1A, PDCD10, TJP1, OCLN, HES1, MAPK1, VEGFA, EGFL7, NF1, and ENG, which are previously characterized as key regulators of CCM pathology. To date, this is the first study to investigate the role of miRNAs in CCM pathology. By employing cutting edge molecular and in silico analyses on clinical samples, the current study reports global miRNA expression changes in CCM patients and provides a rich source of data set to understand detailed molecular machinery involved in CCM pathophysiology.

PHACE syndrome is associated with intracranial cavernous malformations

INTRODUCTION

PHACE syndrome is a neurocutaneous disorder involving large facial hemangiomas in association with posterior fossa abnormalities, cerebral arterial anomalies, cardiac defects, and eye abnormalities. A recent consensus statement has delineated criteria necessary for the diagnosis of PHACE syndrome. Extracutaneous manifestations of PHACE syndrome predominately affect the cerebrovascular system. To date, there are no reports of cerebral cavernous malformations (CCMs) in children with PHACE syndrome.

METHODS

We reviewed the charts of children admitted to the Children''s Hospital of Pittsburgh who met criteria for PHACE syndrome, and evaluated neuroimaging for cerebrovascular abnormalities, including the finding of CCMs.

RESULTS

Six children met criteria for PHACE syndrome at our institution over a 10-year period. All children were female. All children had cerebrovascular abnormalities sufficient to meet major criteria for diagnosis. Four children (66.7 %) were found incidentally to have CCMs; all lesions measured less than 5 mm at the time of diagnosis and were asymptomatic.

CONCLUSION

At present, CCMs are not listed among the diagnostic criteria for PHACE syndrome, and they have not previously been reported in association with PHACE syndrome. Hypoxic injury in utero may be the common denominator in the pathogenesis of many of the abnormalities already accepted in the criteria for PHACE syndrome and the formation of CCMs. In the setting of PHACE syndrome, we encourage clinicians to evaluate children for CCMs, which are readily apparent on the already-recommended screening MRIs.

PDCD10 (CCM3) regulates brain endothelial barrier integrity in cerebral cavernous malformation type 3: role of CCM3-ERK1/2-cortactin cross-talk

Impairment of brain endothelial barrier integrity is critical for cerebral cavernous malformation (CCM) lesion development. The current study investigates changes in tight junction (TJ) complex organization when PDCD10 (CCM3) is mutated/depleted in human brain endothelial cells. Analysis of lesions with CCM3 mutation and brain endothelial cells transfected with CCM3 siRNA (CCM3-knockdown) showed little or no increase in TJ transmembrane and scaffolding proteins mRNA expression, but proteins levels were generally decreased. CCM3-knockdown cells had a redistribution of claudin-5 and occludin from the membrane to the cytosol with no alterations in protein turnover but with diminished protein-protein interactions with ZO-1 and ZO-1 interaction with the actin cytoskeleton. The most profound effect of CCM3 mutation/depletion was on an actin-binding protein, cortactin. CCM3 depletion caused cortactin Ser-phosphorylation, dissociation from ZO-1 and actin, redistribution to the cytosol and degradation. This affected cortical actin ring organization, TJ complex stability and consequently barrier integrity, with constant hyperpermeability to inulin. A potential link between CCM3 depletion and altered cortactin was tonic activation of MAP kinase ERK1/2. ERK1/2 inhibition increased cortactin expression and incorporation into the TJ complex and improved barrier integrity. This study highlights the potential role of CCM3 in regulating TJ complex organization and brain endothelial barrier permeability.

Increased number of white matter lesions in patients with familial cerebral cavernous malformations

BACKGROUND AND PURPOSE

Familial cerebral cavernous malformations, an autosomal dominant disorder, result in excess morbidity and mortality in affected patients. The disorder is most prevalent in the Southwest United States, where the affected families are most often carriers of the CCM1-KRIT1 Common Hispanic Mutation. The brain and spinal cord parenchyma in these individuals is usually affected by multiple cavernous malformations. Previous studies have shown abnormalities of endothelial cell junctions and the blood-brain barrier in cerebral cavernous malformations. Endothelial cell abnormalities have also been described in pathologic studies of white matter hyperintensities. We compared the prevalence of white matter hyperintensities in a population with known familial cerebral cavernous malformations.

MATERIALS AND METHODS

We examined 191 subjects with familial cerebral cavernous malformations who were enrolled into an institutional review board-approved study. All carry the same Common Hispanic Mutation in the CCM1 gene. Each subject underwent 3T MR imaging, including gradient recalled-echo, SWI, and FLAIR sequences. The number of cavernous malformations and the number of nonhemorrhagic white matter hyperintensities were counted. Subjects older than 60 years of age were excluded due to the high prevalence of white matter lesions in this population, and children younger than 6 were excluded due to potential sedation requirements. Logistic regression analysis was performed to determine the prevalence of abnormal white matter hyperintensities in those with familial cerebral cavernous malformations compared with healthy controls or those with sporadic cerebral cavernous malformation within the familial cerebral cavernous malformations group; it was also performed to evaluate the associations between abnormal white matter hyperintensities and age, sex, headaches, thyroid disease, diabetes, hypertension, hyperlipidemia, seizure history, or modified Rankin Scale score.

RESULTS

Familial CCM1 carriers have a higher prevalence of abnormal white matter hyperintensities (15.4%) compared with both control populations (2.1% and 2.5%, respectively) (P < .05). Logistic regression showed no statistical association with sex, headaches, hyperlipidemia, hypertension, thyroid disease, seizure history, number of cerebral cavernous malformations, or modified Rankin Scale score among those with familial cerebral cavernous malformation. An expected correlation with age was shown.

CONCLUSIONS

Familial CCM1 carriers have not only an increased number of cerebral cavernous malformations but also an increased number of white matter T2 hyperintensities, spatially distinct from cerebral cavernous malformations, which exceeded that of a healthy population. Clinical findings did not explain the association with abnormal white matter hyperintensities in the familial cerebral cavernous malformation population. To our knowledge, these relationships have not been previously reported. This finding suggests an additional manifestation of endothelial abnormalities in this population.

Bleeding propensity of cavernous malformations: impact of tight junction alterations on the occurrence of overt hematoma

OBJECT

Endothelial tight junction (TJ) expression is mostly absent in cerebral cavernous malformations (CMs), which causes increased perilesional erythrocyte and fluid oozing. However, in a subset of CM lesions, foci of preserved TJ staining are observed along endothelial cell contacts. The clinical relevance of this finding is unclear. This study investigates the relevance of the focal TJ protein expression and its association with CM bleeding propensity.

METHODS

Immunohistochemical staining for the TJ proteins claudin-5, occludin, and ZO-1 was performed on 32 CM specimens that were resected during 2008-2010. The patients were allocated to 2 groups according to TJ protein expression, and the clinical and radiological parameters of aggressiveness were analyzed and compared. RESULTS Complete absence of TJ expression was identified in 20 specimens, and focal TJ protein expression in 12. CMs without TJ immunoreactivity were significantly larger (p = 0.022) and had a significantly greater propensity for development of frank hematomas (p = 0.028) and perilesional edema (p = 0.013). Symptom severity, multiplicity, developmental venous anomaly (DVA) presence, and CM location did not show a significant difference depending on TJ expression.

CONCLUSIONS

In a univariate analysis the authors observed significantly less propensity for frank hematomas and perilesional edema as well as smaller size in CM lesions with focal TJ expression compared with CMs without TJ expression. The observed difference in TJ protein expression might be the reason for differences in bleeding propensity of the CM lesions. Although this finding cannot be used in predictive manner at this time, it is a basis for further multivariate analyses of possible CM biological predictors.

Systems biology and proteomic analysis of cerebral cavernous malformation

Cerebral cavernous malformations (CCM) are vascular anomalies caused by mutations in genes encoding KRIT1, OSM and PDCD10 proteins causing hemorrhagic stroke. We examine proteomic change of loss of CCM gene expression. Using human umbilical vein endothelial cells, label-free differential protein expression analysis with multidimensional liquid chromatography/tandem mass spectrometry was applied to three CCM protein knockdown cell lines and two control cell lines: ProteomeXchange identifier PXD000362. Principle component and cluster analyses were used to examine the differentially expressed proteins associated with CCM. The results from the five cell lines revealed 290 and 192 differentially expressed proteins (p < 0.005 and p < 0.001, respectively). Most commonly affected proteins were cytoskeleton-associated proteins, in particular myosin-9. Canonical genetic pathway analysis suggests that CCM may be a result of defective cell-cell interaction through dysregulation of cytoskeletal associated proteins.

CONCLUSION

The work explores signaling pathways that may elucidate early detection and novel therapy for CCM.

STRIPAK complexes: structure, biological function, and involvement in human diseases

The mammalian striatin family consists of three proteins, striatin, S/G2 nuclear autoantigen, and zinedin. Striatin family members have no intrinsic catalytic activity, but rather function as scaffolding proteins. Remarkably, they organize multiple diverse, large signaling complexes that participate in a variety of cellular processes. Moreover, they appear to be regulatory/targeting subunits for the major eukaryotic serine/threonine protein phosphatase 2A. In addition, striatin family members associate with germinal center kinase III kinases as well as other novel components, earning these assemblies the name striatin-interacting phosphatase and kinase (STRIPAK) complexes. Recently, there has been a great increase in functional and mechanistic studies aimed at identifying and understanding the roles of STRIPAK and STRIPAK-like complexes in cellular processes of multiple organisms. These studies have identified novel STRIPAK and STRIPAK-like complexes and have explored their roles in specific signaling pathways. Together, the results of these studies have sparked increased interest in striatin family complexes because they have revealed roles in signaling, cell cycle control, apoptosis, vesicular trafficking, Golgi assembly, cell polarity, cell migration, neural and vascular development, and cardiac function. Moreover, STRIPAK complexes have been connected to clinical conditions, including cardiac disease, diabetes, autism, and cerebral cavernous malformation. In this review, we discuss the expression, localization, and protein domain structure of striatin family members. Then we consider the diverse complexes these proteins and their homologs form in various organisms, emphasizing what is known regarding function and regulation. Finally, we explore possible roles of striatin family complexes in disease, especially cerebral cavernous malformation.

Cerebral cavernous malformation proteins at a glance

Loss-of-function mutations in genes encoding KRIT1 (also known as CCM1), CCM2 (also known as OSM and malcavernin) or PDCD10 (also known as CCM3) cause cerebral cavernous malformations (CCMs). These abnormalities are characterized by dilated leaky blood vessels, especially in the neurovasculature, that result in increased risk of stroke, focal neurological defects and seizures. The three CCM proteins can exist in a trimeric complex, and each of these essential multi-domain adaptor proteins also interacts with a range of signaling, cytoskeletal and adaptor proteins, presumably accounting for their roles in a range of basic cellular processes including cell adhesion, migration, polarity and apoptosis. In this Cell Science at a Glance article and the accompanying poster, we provide an overview of current models of CCM protein function focusing on how known protein-protein interactions might contribute to cellular phenotypes and highlighting gaps in our current understanding.

Dynamic contrast-enhanced MRI evaluation of cerebral cavernous malformations

The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76 years, mean 48.1 years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025 mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4 min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects.

Fetal opercular cavernous angioma causing cerebral cleft: contralateral primitive vascular anomaly and subicular dysgenesis

We describe a 22-week female fetus after pregnancy was terminated because of fetal magnetic resonance imaging showing a large left cerebral hemispheric cleft suggestive of porencephaly or schizencephaly. Postmortem examination revealed a large cavernous angioma of the left opercular region with evidence of previous hemorrhage and extensive cerebral infarction. In the right hemisphere, another vascular malformation within the frontal germinal matrix consisted of an aggregate of primitive vessels not yet canalized. Selective dysgenesis of the right subiculum also was demonstrated. This case illustrates not only a severe encephaloclastic effect of cavernous angioma in fetal brain but also the importance of fetal autopsy to help correlate and explain fetal neuroimaging. Potential future prenatal treatment of fetal angiomata requires precise in utero diagnosis.