Transcriptomic signatures of individual cell types in cerebral cavernous malformation

Cerebral cavernous malformation (CCM) is a hemorrhagic neurovascular disease with no currently available therapeutics. Prior evidence suggests that different cell types may play a role in CCM pathogenesis. The contribution of each cell type to the dysfunctional cellular crosstalk remains unclear. Herein, RNA-seq was performed on fluorescence-activated cell sorted endothelial cells (ECs), pericytes, and neuroglia from CCM lesions and non-lesional brain tissue controls. Differentially Expressed Gene (DEG), pathway and Ligand-Receptor (LR) analyses were performed to characterize the dysfunctional genes of respective cell types within CCMs. Common DEGs among all three cell types were related to inflammation and endothelial-to-mesenchymal transition (EndMT). DEG and pathway analyses supported a role of lesional ECs in dysregulated angiogenesis and increased permeability. VEGFA was particularly upregulated in pericytes. Further pathway and LR analyses identified vascular endothelial growth factor A/ vascular endothelial growth factor receptor 2 signaling in lesional ECs and pericytes that would result in increased angiogenesis. Moreover, lesional pericytes and neuroglia predominantly showed DEGs and pathways mediating the immune response. Further analyses of cell specific gene alterations in CCM endorsed potential contribution to EndMT, coagulation, and a hypoxic microenvironment. Taken together, these findings motivate mechanistic hypotheses regarding non-endothelial contributions to lesion pathobiology and may lead to novel therapeutic targets. Video Abstract.

Impact of socioeconomics and race on clinical follow-up and trial enrollment and adherence in cerebral cavernous malformation

OBJECTIVES

Cerebral cavernous malformation (CCM) affects more than a million Americans but advanced care for symptomatic lesions and access to research studies is largely limited to referral academic centers MATERIALS AND METHODS: A cohort of CCM patients screened for research studies at an accredited center of excellence for CCM was analyzed. Demographics, lesion location, history of hemorrhage, insurance type and area of deprivation index (ADI) were collected. Primary outcomes were clinical follow-up within a year from initial evaluation, and enrollment and adherence in clinical trials among eligible subjects RESULTS: A majority (52.8%) of CCM patients evaluated had a high socioeconomic status (SES) (ADI 1-3), and only 11.5% were African American. Patients who had a symptomatic bleed were more likely to follow-up (p=0.01), and those with brainstem lesion were more likely to enroll/adhere in a clinical trial (p=0.02). Rates of clinical follow-up were similar across different ADI groups, insurance coverage and race. Patients who were uninsured/self-paying, and African Americans were more likely to decline/drop from clinical trials (OR 2.4, 95% CI 0.46-10.20 and OR 2.2, 95% CI 0.33-10.75, respectively), but differences were not statistically significant CONCLUSIONS: Access of disadvantaged patients to center of excellence care and research remains limited despite geographic proximity to their community. Patients with lower SES and African Americans are as likely to follow-up clinically, but there were trends of differences in enrollment/adherence in clinical trials. Mitigation efforts should target systemic causes of low access to specialized care among uninsured and African American patients.

Plasma metabolites with mechanistic and clinical links to the neurovascular disease cavernous angioma

BACKGROUND

Cavernous angiomas (CAs) affect 0.5% of the population, predisposing to serious neurologic sequelae from brain bleeding. A leaky gut epithelium associated with a permissive gut microbiome, was identified in patients who develop CAs, favoring lipid polysaccharide producing bacterial species. Micro-ribonucleic acids along with plasma levels of proteins reflecting angiogenesis and inflammation were also previously correlated with CA and CA with symptomatic hemorrhage.

METHODS

The plasma metabolome of CA patients and CA patients with symptomatic hemorrhage was assessed using liquid-chromatography mass spectrometry. Differential metabolites were identified using partial least squares-discriminant analysis (p < 0.05, FDR corrected). Interactions between these metabolites and the previously established CA transcriptome, microbiome, and differential proteins were queried for mechanistic relevance. Differential metabolites in CA patients with symptomatic hemorrhage were then validated in an independent, propensity matched cohort. A machine learning-implemented, Bayesian approach was used to integrate proteins, micro-RNAs and metabolites to develop a diagnostic model for CA patients with symptomatic hemorrhage.

RESULTS

Here we identify plasma metabolites, including cholic acid and hypoxanthine distinguishing CA patients, while arachidonic and linoleic acids distinguish those with symptomatic hemorrhage. Plasma metabolites are linked to the permissive microbiome genes, and to previously implicated disease mechanisms. The metabolites distinguishing CA with symptomatic hemorrhage are validated in an independent propensity-matched cohort, and their integration, along with levels of circulating miRNAs, enhance the performance of plasma protein biomarkers (up to 85% sensitivity and 80% specificity).

CONCLUSIONS

Plasma metabolites reflect CAs and their hemorrhagic activity. A model of their multiomic integration is applicable to other pathologies.

Abstract TMP15: Transcriptomic Signatures Of Individual Cell Types In Cavernous Angioma

Introduction: Cavernous Angiomas (CAs) are vascular malformations characterized by clusters of blood-filled capillary spaces lined by “leaky” endothelium. While mutations in endothelial cells have long been recognized as necessary for lesion genesis, there is evidence of inflammation, response to hypoxia, and non-endothelial autonomous cell effects driving pathogenesis. Disrupted gene expression in the CA neurovascular unit (NVU) has been described but the contribution of each cell type has not been previously investigated.

Methods: Six CA and four control brain samples were collected and frozen during surgical resection. The endothelial cells, pericytes, and neuroglia (astrocytes and neurons) were sorted, and the RNA was extracted and sequenced. The differentially expressed genes (DEGs) were identified ( p <0.05, FDR corrected) for each cell type. Enrichment pathway analyses were performed through Ingenuity Pathway Analyses (IPA, Qiagen; p <0.05, FDR corrected), Gene Ontology (GO; p <0.1, FDR corrected) and Kyoto Encyclopedia of Genes and Genomes (KEGG; p <0.1, FDR corrected).

Results: In endothelial cells, 362 DEGs were identified contributing to 54 enriched IPA pathways. In addition, 484 DEGs were found in pericytes and 50 IPA pathways were identified. The common functions between these two cell types were related to angiogenesis, extracellular matrix organization, cell adhesion, and platelet activation, while the function related to response to hypoxia was only shown in pericytes. Finally, 242 DEGs and 52 IPA pathways were identified in neuroglia cells. The associated pathway functions were related to inflammatory response and cell adhesion. The IPA results were further confirmed by the GO term and KEGG pathway analyses.

Conclusion: We confirm that disrupted genes related to angiogenesis, blood-brain barrier integrity, cell adhesion and platelet activation in the CA lesion involve endothelial cells and pericytes primarily. Pericytes are particularly associated with disrupted genes related to response to hypoxia, while neuroglia is associated with greater gene disruptions related to inflammation. These results motivate novel mechanistic hypotheses regarding non-endothelial cell contributions to lesion pathobiology.

Abstract TMP18: Multiplexed Histopathological Characterization Of Cerebral Microbleeds In The Aging Brain

Background: Cerebral microbleeds (CMBs) are manifestations of age-related microangiopathies associated with an increased risk of hemorrhagic stroke and cognitive decline. The pathophysiology of this age-related breakdown of the neurovascular unit remain unclear. Understanding CMB cellular architecture is needed for gene, pathway, and mechanism analyses, to pave the way for biomarker and therapeutic development. Herein, we aim to systematically describe histopathological changes in the CMB lesional milieu.

Methods: Eight CMBs, along with contralateral non-lesional tissue, were identified by gross appearance at autopsy by a neuropathologist. Samples were first stained with H&E, then Prussian blue for non-heme iron, to localize the lesion. This was followed by multiplex fluorescence staining of β-amyloid and individual cell types including astrocytes (GFAP + ), macrophages (CD163 + /Iba1 + ), microglia (CD163 - /Iba1 + ), B-cells (CD20 + ), T-cells (CD3 + ), and endothelium (CD31 + ). The cell types within the lesional milieu, defined as 200μm from the periphery of the CMB, were quantified using QuPath. Astrocyte and microglia morphology were assessed via fluorescence imaging.

Results: One CMB contained dilated capillaries, 2 contained lipohyalinized arterioles, and 4 contained dystrophic arterioles due to amyloid angiopathy. Astrocytes and macrophages showed higher normalized cell counts in all CMB tissues compared with controls ( p<0.005 and p<0.05 , respectively). Astrocytes in 7 of 8 CMB milieux showed reactive morphological changes, including larger cell bodies with peripheral nuclei. Microglia had higher normalized cell counts in 4 CMB tissues, with senescence-associated amoeboid, as well as ramified, reactive morphologies. The lesional milieu also showed higher counts of B-cells in 7 CMB tissues and T-cells in 3 CMB tissues when compared with controls.

Conclusions: We provide the first description of the cellular architecture of the CMB and the associated lesional milieu. Despite heterogeneity of disrupted vasculature, there are common features of glial reactive changes and inflammation in CMBs. These results offer a basis for additional study of the CMB transcriptome and individual roles of respective cell types in CMB pathology.

Abstract 123: In Vivo Permeability Of The Aging Brain With Cerebral Microbleeds

Introduction: Age-related cerebral microbleeds (CMBs) are vascular changes associated with an increased risk of intracerebral hemorrhage (ICH) and neurocognitive decline. CMBs share a strikingly similar appearance on MRI to cerebral cavernous malformations (CCMs), which are leaky capillary lesions predisposing patients to brain bleeding. Our team had previously shown increased vascular permeability in CCM and in the brain of older subjects, with common circulating biomarkers of angiogenesis and inflammation. We examine here whether vascular permeability is greater in the aging brain harboring CBMs.

Methods: Dynamic Contrast-Enhanced Quantitative Perfusion (DCEQP) MRI, which assesses vascular permeability, was acquired for 7 patients with CMBs (>50 years old), 10 old (>50 years old), and 9 young (18-30 years old) healthy subjects without CMBs. Cases with active brain disease, stroke or seizure in the prior year were excluded. DCEQP scans were co-registered onto their respective T1-weighted images, normalized using the Desikan-Killiany atlas, and finally segmented into white and gray matter within frontal, temporal, parietal, and occipital lobes. The mean permeability was calculated within each segmented area, and values were compared between the 3 groups of interest.

Results: Increased permeability was observed within the frontal white and gray matter as well as the parietal gray matter of patients with CMBs compared to age matched old healthy controls (both: p<0.05). In addition, greater background brain permeability was also observed in old healthy controls compared to young healthy controls, in the occipital white matter, as well as the white and gray matter in the temporal and parietal lobes (all: p<0.05).

Conclusion: We confirm that the human brain exhibits increased vascular permeability with aging, and this is more pronounced in brains harboring CMBs. This may provide insight into the pathogenesis of CMBs, potentially reflecting end stage age-related failure of the blood brain barrier, associated with frank bleeding. These results offer a starting point for the development of diagnostic and prognostic imaging biomarkers of CMBs, which can help stratify patients at higher risk of future ICH and cognitive decline.

Abstract WP17: Plasma Proteins In Correlation With Lesional Iron Content And Permeability Imaging In Clinical Trial Of Cavernous Angioma With Symptomatic Hemorrhage

Background: Increases in mean lesional iron content (≥6%) measurement by QSM and vascular permeability (≥40%) assessed by DCEQP MRI have been associated with new bleeding, and are used as monitoring biomarkers in NINDS funded 1st clinical trial of pharmacotherapy (clinicaltrials.gov NCT02603328) in cavernous angiomas with symptomatic hemorrhage (CASH). Plasma protein levels previously associated with CASH in diagnostic and prognostic contexts have never been compared to lesional QSM and DCEQP in the same subjects.

Methods: Plasma samples and MRI sequences were simultaneously acquired during 1 year-epochs of prospective follow-up of CASH patients. Plasma levels of 16 proteins were assayed by ELISA and correlated with lesional QSM and DCEQP during the same epochs. Univariate correlations were followed by multivariate analyses combining multiple protein levels to minimize Akaike Information Criterion (AIC) and increase R 2 . Accuracy (AUC on receiver operating curves) and sum of squared error (SSE) are reported for associations achieving statistical significance with FDR correction.

Results: None of the proteins individually correlated with QSM/DCEQP (continuous or categorical). Relative change of angiopoietin2, and absolute change of the combination (endoglin+IL1B+IL16) had the highest accuracy (AUC 78.7%, SD 0.062 and 98.4%, SD 0.013 respectively) for lesional QSM increase ≥6%. Relative change of endoglin+IL1B, and absolute change of angiopoetin2+endoglin+thromobomodulin+VEGF, had the highest accuracy (AUC 64.6%, SD 0.057 and 93.2%, SD 0.040 respectively) for lesional DCEQP increase ≥40%. Relative change in angiopoetin1 had the lowest SSE (8.87) with QSM change as a continuous variable, and relative change in lipopolysaccharide binding protein had the lowest SSE (469.06) with DCEQP change as continuous variable.

Conclusion: Circulating proteins reflect changes in lesional iron content and permeability in CASH during prospective follow-up. Results are a proof of concept that blood tests could replace more complex and costly imaging biomarkers in the monitoring of hemorrhage in cavernous angiomas. Additional mechanistic plasma molecules (miRNAs and metabolites) may further enhance the accuracy of these monitoring biomarkers.

Cerebral Hemorrhage: Pathophysiology, Treatment, and Future Directions

Intracerebral hemorrhage (ICH) is a devastating form of stroke with high morbidity and mortality. This review article focuses on the epidemiology, cause, mechanisms of injury, current treatment strategies, and future research directions of ICH. Incidence of hemorrhagic stroke has increased worldwide over the past 40 years, with shifts in the cause over time as hypertension management has improved and anticoagulant use has increased. Preclinical and clinical trials have elucidated the underlying ICH cause and mechanisms of injury from ICH including the complex interaction between edema, inflammation, iron-induced injury, and oxidative stress. Several trials have investigated optimal medical and surgical management of ICH without clear improvement in survival and functional outcomes. Ongoing research into novel approaches for ICH management provide hope for reducing the devastating effect of this disease in the future. Areas of promise in ICH therapy include prognostic biomarkers and primary prevention based on disease pathobiology, ultra-early hemostatic therapy, minimally invasive surgery, and perihematomal protection against inflammatory brain injury.

Developmental venous anomalies are a genetic primer for cerebral cavernous malformations

Cerebral cavernous malformations (CCM) are a neurovascular anomaly that may occur sporadically, or be inherited due to autosomal dominant mutations in KRIT1 , CCM2 , or PDCD10 . Individual lesions are caused by somatic mutations which have been identified in KRIT1, CCM2, PDCD10, MAP3K3, and PIK3CA . However, the interactions between mutations, and their relative contributions to sporadic versus familial cases remain unclear. We show that mutations in KRIT1, CCM2, PDCD10, and MAP3K3 are mutually exclusive, but may co-occur with mutations in PIK3CA. We also find that MAP3K3 mutations may cause sporadic, but not familial CCM. Furthermore, we find identical PIK3CA mutations in CCMs and adjacent developmental venous anomalies (DVA), a common vascular malformation frequently found in the vicinity of sporadic CCMs. However, somatic mutations in MAP3K3 are found only in the CCM. This suggests that sporadic CCMs are derived from cells of the DVA which have acquired an additional mutation in MAP3K3 .

Abstract TMP9: Novel Single-cell Isolation From Cerebral Cavernous Angioma Specimens For Transcriptomic Studies

Introduction: Cavernous angiomas (CAs) are common neurovascular lesions predisposing patients to seizures and hemorrhagic stroke. Recent evidence shows non-endothelial cell autonomous effects contribute to CA pathogenesis within the dysfunctional neurovascular units (NVUs), consisting of endothelial cells, pericytes, astrocytes, and microglia. Herein, we developed a single-cell isolation protocol to study the transcriptome of each of these cell populations.

Method: CAs and control brain tissue were frozen in optimal cutting temperature compound immediately after surgical resection. Tissue was enzymatically digested with Collagenase Type IV and DNase I. The cell suspension was then filtered, washed, and pelleted. Cell debris and myelin were removed using 25% Percoll. A multispectral LED light was used for 30 minutes to reduce background autofluorescence. Cells were stained with a CD31, CD45, CD13, P2RY12, CD49f, GLAST, CD24 and CD90 antibody cocktail. Size, granularity, and antibody-specific gating were set to sort each cell population using the BD FACSymphony S6 Cell Sorter. After isolation, RNA was extracted for each cell population, and the quality was assessed. Cell-specific genes including VWF (endothelial cells), ACTA2 (pericytes ), AQP4 (astrocytes ) and IBA-1 (microglia ), as well as GAPDH were assessed with real-time qPCR (rt-qPCR) for validation.

Results: Endothelial cells (CD31 + , CD13 - , CD45 - , CD49f - , GLAST - ), pericytes (CD13 + , CD31 - , CD45 - , CD49f - , GLAST - ), astrocytes (CD49f + , GLAST + ) and microglia (P2RY12 + , CD45 + , CD31 - , CD13 - , CD49f - , GLAST - ) were individually isolated from both 5 CA lesions and 5 control brain tissue using FACS sorting. RNA quantity ranged from 31 to 83 pg/μl, with RNA Integrity Number ranging from 1 to 8.7. Each cell population within the CA lesion was validated by showing differential expression of cell-specific genes.

Conclusion: We have shown, for the first-time, feasibility of individual cell type isolation from frozen, surgically excised CA lesions. The RNA quantity and quality of each cell population was suitable for the establishment of cell-specific transcriptome libraries. These will help clarify individual cell type contributions to CA pathogenesis.

Abstract TMP1: Multi-omic Biomarker Development In A Mendelian Neurovascular Disease, Cavernous Angioma

Introduction: Cavernous Angioma (CA) is a hemorrhagic neurovascular disease characterized by either a familial form with autosomal dominant germline mutations in one of three CCM genes or a sporadic form with somatic mutations of the same genes. Circulating proteins have been previously investigated as possible diagnostic and prognostic biomarkers of disease activity, with up to 86% and 88% sensitivity and specificity, respectively. We hypothesize that differentially expressed (DE) plasma microRNAs and metabolites in CA patients can be integrated with plasma proteins to increase the sensitivity and specificity of circulating CA biomarkers.

Methods: Mechanistically relevant homologous DE miRNAs were identified between familial CA patients and preclinical murine models and validated in an independent cohort of patients using real time qPCR. In conjunction, DE metabolites were determined in CA patients using liquid-chromatography mass spectrometry. The interactions of these metabolites with the previously established CA transcriptome, proteome, and microbiome were queried to assess for mechanistic relevance. Optimal diagnostic models of proteins, DE miRNAs, and DE metabolites alone were next established. Plasma metabolites and miRNAs were then separately integrated with protein, using a machine learning-implemented, Bayesian approach to develop diagnostic CA biomarkers.

Results: The optimal diagnostic biomarker model with only DE miRNAs performed at up to 68%, while proteins and metabolites achieved up to 68%, and 82% accuracy respectively. The optimal combination for proteins with miRNAs improved the diagnostic association of familial-CA disease to up to 94.7% sensitivity and 100% specificity. Integrating metabolites and proteins improved the diagnosis of CA disease and its clinical manifestations to 100% sensitivity and 100% specificity.

Conclusion: Combining plasma proteins with miRNAs or metabolites can improve diagnostic accuracy of CA disease and its disease characteristics above any single molecular modality alone. Future studies should incorporate proteins, miRNAs, and metabolites to further increase diagnostic accuracy, and validate these in a larger cohort with control for demographic and disease features.

PIK3CA and CCM mutations fuel cavernomas through a cancer-like mechanism

Vascular malformations are thought to be monogenic disorders that result in dysregulated growth of blood vessels. In the brain, cerebral cavernous malformations (CCMs) arise owing to inactivation of the endothelial CCM protein complex, which is required to dampen the activity of the kinase MEKK31-4. Environmental factors can explain differences in the natural history of CCMs between individuals5, but why single CCMs often exhibit sudden, rapid growth, culminating in strokes or seizures, is unknown. Here we show that growth of CCMs requires increased signalling through the phosphatidylinositol-3-kinase (PI3K)-mTOR pathway as well as loss of function of the CCM complex. We identify somatic gain-of-function mutations in PIK3CA and loss-of-function mutations in the CCM complex in the same cells in a majority of human CCMs. Using mouse models, we show that growth of CCMs requires both PI3K gain of function and CCM loss of function in endothelial cells, and that both CCM loss of function and increased expression of the transcription factor KLF4 (a downstream effector of MEKK3) augment mTOR signalling in endothelial cells. Consistent with these findings, the mTORC1 inhibitor rapamycin effectively blocks the formation of CCMs in mouse models. We establish a three-hit mechanism analogous to cancer, in which aggressive vascular malformations arise through the loss of vascular 'suppressor genes' that constrain vessel growth and gain of a vascular 'oncogene' that stimulates excess vessel growth. These findings suggest that aggressive CCMs could be treated using clinically approved mTORC1 inhibitors.

A Roadmap for Developing Plasma Diagnostic and Prognostic Biomarkers of Cerebral Cavernous Angioma With Symptomatic Hemorrhage (CASH)

BACKGROUND

Cerebral cavernous angioma (CA) is a capillary microangiopathy predisposing more than a million Americans to premature risk of brain hemorrhage. CA with recent symptomatic hemorrhage (SH), most likely to re-bleed with serious clinical sequelae, is the primary focus of therapeutic development. Signaling aberrations in CA include proliferative dysangiogenesis, blood-brain barrier hyperpermeability, inflammatory/immune processes, and anticoagulant vascular domain. Plasma levels of molecules reflecting these mechanisms and measures of vascular permeability and iron deposition on magnetic resonance imaging are biomarkers that have been correlated with CA hemorrhage.

OBJECTIVE

To optimize these biomarkers to accurately diagnose cavernous angioma with symptomatic hemorrhage (CASH), prognosticate the risk of future SH, and monitor cases after a bleed and in response to therapy.

METHODS

Additional candidate biomarkers, emerging from ongoing mechanistic and differential transcriptome studies, would further enhance the sensitivity and specificity of diagnosis and prediction of CASH. Integrative combinations of levels of plasma proteins and characteristic micro-ribonucleic acids may further strengthen biomarker associations. We will deploy advanced statistical and machine learning approaches for the integration of novel candidate biomarkers, rejecting noncorrelated candidates, and determining the best clustering and weighing of combined biomarker contributions.

EXPECTED OUTCOMES

With the expertise of leading CA researchers, this project anticipates the development of future blood tests for the diagnosis and prediction of CASH to clinically advance towards precision medicine.

DISCUSSION

The project tests a novel integrational approach of biomarker development in a mechanistically defined cerebrovascular disease with a relevant context of use, with an approach applicable to other neurological diseases with similar pathobiologic features.

Abstract P737: Human Homologs Of Differentially Expressed Plasma MicroRNAs In Preclinical Murine Models Target Fundamental Mechanisms Of Cerebral Cavernous Malformation

Introduction: There is a current need for sensitive and specific biomarkers of Cerebral Cavernous Malformation (CCM) that can be readily translated from preclinical to human models to accurately diagnose and monitor disease states and response to novel therapeutics. MiRNAs are small non-coding RNAs that influence gene expression and whose levels can be affected by disease states. We hypothesize that there are human homologs of differentially expressed (DE) miRNA in the plasma of CCM murine models that can be identified in CCM patients. We further hypothesize that these miRNAs have gene targets within previously published CCM transcriptomes, mechanistically linking them to CCM disease.

Methods: Plasma miRNAs from homozygous and heterozygous Ccm1 and Ccm3 mice, as well as their respective wild type controls were sequenced and analyzed. Putative gene targets of DE miRNAs [p<0.05, false discovery rate (FDR) corrected] were queried in previously published mouse CCM transcriptomes. The human homologs of the DE miRNAs in the plasma of Ccm1 and Ccm3 mouse models were identified and assessed in the plasma of healthy controls (n=13), CCM1 (n=11), and CCM3 (n=11) patients using RT-qPCR.

Results: 5 miRNAs in homozygous and 10 in heterozygous for Ccm1 , while 45 in homozygous and 2 in heterozygous for Ccm3 were DE in the plasma of mouse models (p<0.05, FDR corrected), had gene targets within CCM mouse transcriptomes, and have a human homolog. Preliminary results show mmu-miR-375-3p as DE in both Ccm1 +/- and Ccm3 -/- mice. RT-qPCR assays show that plasma relative quantification values of the human homolog hsa-miR-375-3p were higher in CCM3 than in CCM1 patients ( p <0.001) and in healthy controls ( p <0.05).

Conclusion: DE plasma miRNAs identified in mouse models with human homologs and putative gene targets mechanistically implicated in CCM disease may be used as candidate biomarkers for specific clinical contexts.

Abstract P36: Lesional Perfusion and Permeability Are Diagnostic and Prognostic Biomarkers of Cavernous Angioma With Symptomatic Hemorrhage

Introduction: Diagnosis of cavernous angioma with symptomatic hemorrhage (CASH) requires MRI evidence of lesional bleeding associated directly with attributable symptoms. However, hemorrhagic signs of CASH may become clinically silent on conventional MRI after 3 months. As CASH is likely to rebleed for several years, accurate diagnosis of CASH that bled more than 3 months prior is needed.

Hypothesis: Perfusion and permeability derivations of dynamic contrast-enhanced quantitative perfusion (DCEQP) MRI can diagnose CASH and predict bleeding/growth in CAs.

Methods: CAs of 205 consecutively enrolled patients scanned with DCEQP during clinical visits were classified as CASH that bled 3 - 12 months prior (N = 55) versus non-CASH (N = 658) or CA with (N = 23) versus without (N = 721) bleeding/growth within a year after MRI. Demographics and 13 perfusion and 13 permeability derivations of DCEQP were assessed via machine learning and univariate analyses. Logistic regression models ln ( P / 1 - P ) = Σ (β i x i ) + β 0 were selected as the best diagnostic and prognostic biomarkers by minimizing the Bayesian information criterion (BIC).

Results: The best diagnostic biomarker of CASH that bled 3 - 12 months prior (BIC = 321.6, Figure A) showed 80% sensitivity and 82% specificity. Permeability derivations did not add diagnostic efficacy when combined with perfusion. The best prognostic biomarker of bleeding/growth (BIC = 201.5, Figure B) showed 77% sensitivity and 72% specificity.

Conclusion: Perfusion imaging may diagnose CASH even after hemorrhagic signs disappear on conventional MRI. A combination of permeability and perfusion derivations may help predict bleeding/growth in CAs.

Antibodies in cerebral cavernous malformations react with cytoskeleton autoantigens in the lesional milieu

Previous studies have reported robust inflammatory cell infiltration, synthesis of IgG, B-cell clonal expansion, deposition of immune complexes and complement within cerebral cavernous malformation (CCM) lesions. B-cell depletion has also been shown to reduce the maturation of CCM in murine models. We hypothesize that antigen(s) within the lesional milieu perpetuate the pathogenetic immune responses in CCMs. This study aims to identify those putative antigen(s) using monoclonal antibodies (mAbs) derived from plasma cells found in surgically removed human CCM lesions. We produced human mAbs from laser capture micro-dissected plasma cells from four CCM patients, and also germline-reverted versions. CCM mAbs were assayed using immunofluorescence on central nervous system (CNS) tissues and immunocytochemistry on human primary cell lines. Antigen characterization was performed using a combination of confocal microscopy, immunoprecipitation and mass spectrometry. Affinity was determined by enzyme-linked immunosorbent assay, and specificity by multi-color confocal microscopy and quantitative co-localization. CCM mAbs bound CNS tissue, especially endothelial cells and astrocytes. Non-muscle myosin heavy chain IIA (NMMHCIIA), vimentin and tubulin are three cytoskeleton proteins that were commonly targeted. Selection of cytoskeleton proteins by plasma cells was supported by a high frequency of immunoglobulin variable region somatic hypermutations, high affinity and selectivity of mAbs in their affinity matured forms, and profoundly reduced affinity and selectivity in the germline reverted forms. Antibodies produced by plasma cells in CCM lesions commonly target cytoplasmic and cytoskeletal autoantigens including NMMHCIIA, vimentin and tubulin that are abundant in endothelial cells and astrocytes. Binding to, and selection on autoantigen(s) in the lesional milieu likely perpetuates the pathogenetic immune response in CCMs. Blocking this in situ autoimmune response may yield a novel treatment for CCM.

Common transcriptome, plasma molecules, and imaging signatures in the aging brain and a Mendelian neurovascular disease, cerebral cavernous malformation

Brain senescence is associated with impaired endothelial barrier function, angiogenic and inflammatory activity, and propensity to brain hemorrhage. The same pathological changes occur in cerebral cavernous malformations (CCM), a genetic neurovascular anomaly. We hypothesized common transcriptomic and plasma cytokine signatures in the aging brain and CCM. We identified 320 genes [fold change ≥1.5; p < 0.05; false discovery rate (FDR) corrected] commonly dysregulated in the aging brain and CCM. Ontology and pathway analyses of the common differentially expressed genes were related to inflammation and extracellular matrix organization. Plasma levels of C-reactive protein and angiopoietin-2 were significantly greater in older compared to younger healthy non-CCM subjects and were also greater in CCM (Sporadic and Familial) subjects regardless of age (all: p < 0.05; FDR corrected). Plasma levels of vascular endothelial growth factor were significantly greater in older compared to younger subjects, in both healthy non-CCM and Sporadic-CCM groups (all: p_adj < 0.05). Plasma levels of vascular endothelial growth factor were also significantly greater in Familial-CCM cases with germ line mutations regardless of age (all: p_adj < 0.05) compared to both healthy non-CCM and Sporadic-CCM subjects. Brain white matter vascular permeability assessed by MRI followed the same pattern as vascular endothelial growth factor across all groups. In addition, quantitative susceptibility mapping of brain white matter, a measure of iron deposition, was increased in older compared to younger healthy non-CCM subjects. Genetic aberrations, plasma molecules, and imaging biomarkers in a well characterized Mendelian neurovascular disease may also be applicable in the aging brain. Graphical abstract.

Subclinical imaging changes in cerebral cavernous angiomas during prospective surveillance

OBJECTIVE

The purpose of this study was to systematically assess asymptomatic changes (ACs), including subclinical hemorrhage, growth, or new lesion formation (NLF) during longitudinal follow-up of cerebral cavernous angiomas (CAs), and to correlate these with symptomatic hemorrhage (SH) during the same period and with clinical features of the disease.

METHODS

One hundred ninety-two patients were included in this study, among 327 consecutive patients with CA, prospectively identified between September 2009 and February 2019. Included patients had undergone clinical and MRI follow-up, in conjunction with institutional review board-approved biomarker studies, and harbored ≥ 1 CA with a maximum diameter of ≥ 5 mm on T2-weighted MRI. Rates of AC and SH per lesion-year and patient-year were assessed using prospectively articulated criteria. In multifocal/familial cases, rates of NLF were also assessed.

RESULTS

There were no differences in demographic or disease features among cases included or excluded in the study cohort, except for a higher proportion of included patients with CCM3 mutation. Follow-up was 411 patient-years (2503 lesion-years). The rate of AC was higher than the rate of SH (12.9% vs 7.5% per patient-year, and 2.1% vs 1.2% per lesion-year, both p = 0.02). Patients presenting with a prior history of SH had a higher rate of AC than those with other forms of presentation (19.7% and 8.2% per patient-year, respectively; p = 0.003). A higher rate of NLF on T2-weighted MRI (p = 0.03) was observed in patients with prior SH. Three of 6 solitary/sporadic and 2 of 28 multifocal/familial patients underwent resection of the lesion after AC.

CONCLUSIONS

Rates of AC are greater than SH during prospective follow-up of CAs, and greater in cases with prior SH. AC may be a more sensitive biomarker of lesional activity, and a more efficient surrogate outcome in clinical trials than SH. Patients experiencing an AC are more likely to undergo a surgical intervention when CAs are solitary/sporadic than when they are multifocal/familial.

Abstract TMP115: Common Transcriptomic and Biomarker Signatures in the Aging Brain and in Mendelian Neurovascular Disease, Cerebral Cavernous Malformation

Background: Cellular senescence is associated with gene expression dysregulation affecting endothelial barrier function as well as angiogenic and inflammatory processes. These pathological changes occur in cerebral cavernous malformations (CCMs), a neurovascular anomaly predisposing patients to hemorrhagic stroke. We hypothesize common transcriptomic and biomarker signatures between the aging brain and CCMs.

Method: Brain specific genes dysregulate in Younger (age < 30) and Older (age > 50) human brain parenchyma were identified using the Genotype-Tissue Expression database, and compared with differential transcriptome in microdissected neurovascular units of human CCM lesions. Brain white matter vascular permeability in areas devoid of lesions was measured in non-CCM (23 Younger, 27 Older), Sporadic-CCM (S-CCM) (26 Younger, 37 Older) and Familial-CCM (F-CCM) (41 Younger, 17 Older) using dynamic contrast-enhanced quantitative perfusion MRI. Plasma levels of 6 proteins with reported roles in CCMs were quantified, including VEGF, angiopoietin (ANG 1 & 2), CRP, thrombospondin 2 (THBS 2), and endoglin (ENG). All reported correlations were significant at P< 0.05, FDR corrected.

Result: We identified 320 genes (absolute fold change≥1.5) commonly dysregulated in aging brain and CCM, related to inflammation and extracellular matrix organization pathways. Brain permeability was greater in Older non-CCM and S-CCM compared to Younger subjects. Brain permeability was higher in Younger F-CCM harboring germ line CCM mutations, than in both Younger non-CCM (p<0.001) and S-CCM (p<0.05) lacking those mutations. No difference was observed in Younger or Older F-CCM and Older S-CCM or controls. Plasma levels of VEGF, ANG-2 and CRP were greater in both Older non-CCM and S-CCM compared to Younger. No difference was found in Older or Younger F-CCM. No differences were observed in THBS2, ENG and ANG1.

Conclusion: There are common transcriptomic, and brain permeability and plasma biomarker signatures in the aging brain and CCM, suggesting common dysregulated pathways. Biomarkers and potential therapies identified in a well characterized Mendelian neurovascular disease may be applicable to mitigate the same mechanistic aberrations in the aging brain.

Abstract TMP120: Autoantigen(s) Trigger a Robust Immune Response in Cerebral Cavernous Malformations

Introduction: Previous studies have reported robust inflammatory cell infiltration, selective synthesis of IgG, B-cell clonal expansion, and deposition of immune complexes and complement within Cerebral Cavernous Malformation (CCM) lesions. Furthermore,B-cell depletion has been shown to reduce the maturation of CCM in murine models. We hypothesize that specific autoantigen(s) within the lesional milieu trigger the pathogenetic immune responses in CCMs. This study aims to identify those putative autoantigen(s) using recombinant antibodies (rAbs) derived from plasma cells found in surgical human CCM lesions.

Methods: CD138 + plasma cells were laser captured from fresh frozen surgically resected human CCM lesions. Clonally expanded immunoglobulin heavy- and light-chain variable region pairs were cloned into IgG expression vectors and expressed as monoclonal antibodies. Purified rAbs were assayed by immunofluorescence with CCM lesion tissue and normal brain tissue sections. rAbs assayed by immunocytochemistry with human primary cell line were used to further define the staining pattern. The cell lysates were immunoprecipitated with rAb, after protein purification by SDS-PAGE, and analyzed by Mass spectrometry.

Results: In normal brain tissue, rAbs stained endothelial cells with limited staining of glial cells. In CCM lesional tissue, rAbs stained endothelial cells, glial cells as well as structures in the acellular matrix adjacent to caverns. In cultured Human Brain Microvascular Endothelial Cells (HBMECs) and Human Astrocytes (HAs), rAbs co-localized with cytoplasmic components. After HBMEC and HA cell lysates were immunoprecipitated with rAb, a Coomassie Stain detected bands of approximately 50 kDa.

Conclusions: Our results suggest that autoantigen(s) in human CCM lesions are cytoplasmic components present in lesional tissue as well as in normal brain tissue. Molecular level identification of the triggering antigen is still ongoing by mass spectrometry. Identification of the autoantigen(s) in the lesional milieu might explain the propensity of lesion development from leaky endothelium in the neuroglial parenchyma. Characterization of the autoantigen triggers will open new venues for therapy or vaccine in this disease.

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.

Biomarkers of cavernous angioma with symptomatic hemorrhage

BACKGROUNDCerebral cavernous angiomas (CAs) with a symptomatic hemorrhage (CASH) have a high risk of recurrent hemorrhage and serious morbidity.METHODSEighteen plasma molecules with mechanistic roles in CA pathobiology were investigated in 114 patients and 12 healthy subjects. The diagnostic biomarker of a CASH in the prior year was derived as that minimizing the Akaike information criterion and validated using machine learning, and was compared with the prognostic CASH biomarker predicting bleeding in the subsequent year. Biomarkers were longitudinally followed in a subset of cases. The biomarkers were queried in the lesional neurovascular unit (NVU) transcriptome and in plasma miRNAs from CASH and non-CASH patients.RESULTSThe diagnostic CASH biomarker included a weighted combination of soluble CD14 (sCD14), VEGF, C-reactive protein (CRP), and IL-10 distinguishing CASH patients with 76% sensitivity and 80% specificity (P = 0.0003). The prognostic CASH biomarker (sCD14, VEGF, IL-1β, and sROBO-4) was confirmed to predict a bleed in the subsequent year with 83% sensitivity and 93% specificity (P = 0.001). Genes associated with diagnostic and prognostic CASH biomarkers were differentially expressed in CASH lesional NVUs. Thirteen plasma miRNAs were differentially expressed between CASH and non-CASH patients.CONCLUSIONShared and unique biomarkers of recent symptomatic hemorrhage and of future bleeding in CA are mechanistically linked to lesional transcriptome and miRNA. The biomarkers may be applied for risk stratification in clinical trials and developed as a tool in clinical practice.FUNDINGNIH, William and Judith Davis Fund in Neurovascular Surgery Research, Be Brave for Life Foundation, Safadi Translational Fellowship, Pritzker School of Medicine, and Sigrid Jusélius Foundation.

Comprehensive transcriptome analysis of cerebral cavernous malformation across multiple species and genotypes

The purpose of this study was to determine important genes, functions, and networks contributing to the pathobiology of cerebral cavernous malformation (CCM) from transcriptomic analyses across 3 species and 2 disease genotypes. Sequencing of RNA from laser microdissected neurovascular units of 5 human surgically resected CCM lesions, mouse brain microvascular endothelial cells, Caenorhabditis elegans with induced Ccm gene loss, and their respective controls provided differentially expressed genes (DEGs). DEGs from mouse and C. elegans were annotated into human homologous genes. Cross-comparisons of DEGs between species and genotypes, as well as network and gene ontology (GO) enrichment analyses, were performed. Among hundreds of DEGs identified in each model, common genes and 1 GO term (GO:0051656, establishment of organelle localization) were commonly identified across the different species and genotypes. In addition, 24 GO functions were present in 4 of 5 models and were related to cell-to-cell adhesion, neutrophil-mediated immunity, ion transmembrane transporter activity, and responses to oxidative stress. We have provided a comprehensive transcriptome library of CCM disease across species and for the first time to our knowledge in Ccm1/Krit1 versus Ccm3/Pdcd10 genotypes. We have provided examples of how results can be used in hypothesis generation or mechanistic confirmatory studies.

Abstract 63: Plasma Biomarkers of Cavernous Angioma With Symptomatic Hemorrhage (CASH)

Introduction: Cerebral cavernous angiomas with a documented symptomatic hemorrhage (CASH) are associated with an exceptionally high risk of recurrent hemorrhage and serious morbidity. It is unclear if peripheral blood plasma biomarkers implicated in disease biology can differentiate CASH, and whether the same or different biomarkers can distinguish cases who would rebleed.

Methods: Eighteen plasma molecules with postulated mechanistic roles in this disease were quantified in 114 patients and 12 healthy subjects. The best biomarker combination differentiating CASH in the prior year (+/- 30 days) was derived by minimizing the Akaike Information Criterion (AIC), and was validated using statistical and machine-learning simulations. This was compared to the biomarker predicting bleeding in the subsequent year (+/- 30 days), and both explanatory and predictive biomarkers were followed longitudinally in a subset of cases.

Results: Nine plasma molecules had significantly different levels expressed in CASH patients (p<0·05, FDR corrected). The best biomarker (AIC=75·9) included a weighted combination of 4 of these (sCD-14, VEGF, CRP, and IL-10), and distinguished CASH patients with 76% sensitivity and 80% specificity (p=0·0003). A weighed combination of two of these compounds (sCD14 and VEGF) and two others (IL-1β and sROBO-4) predicted which patients would bleed in the subsequent year with 83% sensitivity and 93% specificity (p=0·001). The CASH biomarker increased in recovering patients (p=0·01), while the predictive biomarker decreased after a bleed (p=0·01). No significant change over time was observed in stable subjects in either biomarker.

Conclusions: Our results suggest shared and unique biomarkers of recent symptomatic hemorrhage and of future bleeding in cavernous angiomas. This may be applied for risk stratification in clinical trials, and potentially developed as a tool in clinical practice.

Abstract TMP107: Microbiome Signature of Cerebral Cavernous Malformation Patients

Background: Cerebral cavernous malformation (CCM) patients have lesions comprised of dilated capillaries in the brain. Despite the knowledge that mutations of three CCM genes can cause this disease, other genetic and environmental factors that contribute to lesion formation are likely given the highly variable disease expression. Genome-wide association studies in CCM cohorts and mouse models of CCM, both point to a role of lipopolysaccharide. Mouse studies have shown that the microbiome, particularly Gram-negative bacteria, drive CCM lesion development. These data point to a possibility that CCM disease is affected by the gut microbiome. In this study, we investigated if human CCM disease could be linked to the gut microbiome.

Methods: Fecal samples from 88 CCM patients, from four sites, were assayed using 16S rRNA gene sequencing. Following taxonomic classification by exact sequence variant analysis (ESV) using DeBlur, microbiome composition was compared with those of a reference non-CCM population (n=348), or between subgroups of CCM patients based on clinical data elements.

Results: Analyses of microbiome composition statistics identified bacterial ESVs belonging to Clostridiales , Lachnospiraceae, Ruminococcaceae , and the genus Bacteroides that were significantly enriched in CCM patients compared to healthy controls. Within our CCM cohort, patients with germline CCM mutations had stool-associated enrichment of ESVs annotated to Clostridiales, and the genera Bacteroides and Prevotella , when compared to sporadic CCM patients, while patients with CCM1 and CCM2 mutations had different proportions of Clostridiales, Lachnospiraceae, and the genus Ruminococcus . Furthermore, Lachnospiraceae and Bacteroides proportions differentiated disease aggressiveness (All p<0.05, false discovery rate corrected).

Conclusions: These data are the first to show that CCM patients have a distinct microbiome signature. Germline mutation and disease aggressiveness can correlate with further unique microbiome composition. This study supports further investigation into the mechanistic link between CCM disease and the microbiome. This will enhance our understanding of the brain-gut axis in CCM disease and the use of microbiome as a therapeutic target.