SUMMARY Cerebral cavernous malformations (CCMs) are a cause of stroke and seizure for which no medical therapies exist. CCMs arise from loss of an adaptor complex that negatively regulates MEKK3-KLF2/4 signaling in brain endothelial cells, but upstream activators of this disease pathway remain unknown. Here, we identify endothelial TLR4 and the gut microbiome as critical stimulants of CCM formation. Activation of TLR4 by gram negative bacteria or lipopolysaccharide accelerates CCM formation, while genetic or pharmacologic blockade of TLR4 signaling prevents CCM formation in mice. Polymorphisms that increase expression of TLR4 or its co-receptor CD14 are associated with higher CCM lesion burden in humans. Germ-free mice are protected from CCM formation, and a single course of antibiotics permanently alters CCM susceptibility in mice. These studies identify unexpected roles for the microbiome and innate immune signaling in the pathogenesis of a cerebrovascular disease, as well as novel strategies for its treatment.

Loss of Krit1 disables an angiogenic checkpoint by reducing TSP1 expression, thereby enabling cerebral cavernous malformation (CCM) formation. Lopez-Ramirez et al. propose that replacing TSP1 by TSP1 fragments or angiogenesis inhibitors may provide an approach to inhibit CCM development.

OBJECTIVE Vascular permeability and iron leakage are central features of cerebral cavernous malformation (CCM) pathogenesis. The authors aimed to correlate prospective clinical behavior of CCM lesions with longitudinal changes in biomarkers of dynamic contrast-enhanced quantitative permeability (DCEQP) and quantitative susceptibility mapping (QSM) assessed by MRI. METHODS Forty-six patients with CCMs underwent 2 or more permeability and/or susceptibility studies in conjunction with baseline and follow-up imaging and clinical surveillance during a mean 12.05 months of follow-up (range 2.4-31.27 months). Based on clinical and imaging features, cases/lesions were classified as stable, unstable, or recovering. Associated and predictive changes in quantitative permeability and susceptibility were investigated. RESULTS Lesional mean permeability and QSM values were not significantly different in stable versus unstable lesions at baseline. Mean lesional permeability in unstable CCMs with lesional bleeding or growth increased significantly (+85.9% change; p = 0.005), while mean permeability in stable and recovering lesions did not significantly change. Mean lesional QSM values significantly increased in unstable lesions (+44.1% change; p = 0.01), decreased slightly with statistical significance in stable lesions (-3.2% change; p = 0.003), and did not significantly change in recovering lesions. Familial cases developing new lesions during the follow-up period showed a higher background brain permeability at baseline (p = 0.001), as well as higher regional permeability (p = 0.003) in the area that would later develop a new lesion as compared with the homologous contralateral brain region. CONCLUSIONS In vivo assessment of vascular permeability and iron deposition on MRI can serve as objective and quantifiable biomarkers of disease activity in CCMs. This may be applied in natural history studies and may help calibrate clinical trials. The 2 techniques are likely applicable in other disorders of vascular integrity and iron leakage such as aging, hemorrhagic microangiopathy, and traumatic brain injury.

Background and Purpose We sought to compare the effect of chronic treatment with commonly tolerated doses of Fasudil, a specific RhoA kinase (ROCK) inhibitor, and simvastatin (with pleiotropic effects including ROCK inhibition) on cerebral cavernous malformation (CCM) genesis and maturation in two models that recapitulate the human disease. Methods Two heterozygous murine models, Ccm1+/-Msh2-/- and Ccm2+/-Trp53-/-, were treated from weaning to 4-5 months of age with Fasudil (100 mg/kg/day), simvastatin (40 mg/kg/day) or with placebo. Mouse brains were blindly assessed for CCM lesion burden, non-heme iron deposition (as a quantitative measure of chronic lesional hemorrhage) and ROCK activity. Results Fasudil, but not simvastatin, significantly decreased mature CCM lesion burden in Ccm1+/-Msh2-/- mice, and in meta-analysis of both models combined, when compared to mice receiving placebo. Fasudil and simvastatin both significantly decreased the integrated iron density per mature lesion area in Ccm1+/-Msh2-/- mice, and in both models combined, compared to mice given placebo. ROCK activity in mature lesions of Ccm1+/-Msh2-/- mice was similar with both treatments. Fasudil, but not simvastatin, improved survival in Ccm1+/-Msh2-/- mice. Fasudil and simvastatin treatment did not affect survival or lesion development significantly in Ccm2+/-Trp53-/- mice alone, and Fasudil benefit appeared limited to males. Conclusion ROCK inhibitor Fasudil was more efficacious than simvastatin in improving survival and blunting the development of mature CCM lesions. Both drugs significantly decreased chronic hemorrhage in CCM lesions. These findings justify the development of ROCK inhibitors, and the clinical testing of commonly used statin agents in CCM.

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.

BACKGROUND More than a million Americans harbor a cerebral cavernous angioma (CA), and those who suffer a prior symptomatic hemorrhage have an exceptionally high rebleeding risk. Preclinical studies show that atorvastatin blunts CA lesion development and hemorrhage through inhibiting RhoA kinase (ROCK), suggesting it may confer a therapeutic benefit. OBJECTIVE To evaluate whether atorvastatin produces a difference compared to placebo in lesional iron deposition as assessed by quantitative susceptibility mapping (QSM) on magnetic resonance imaging in CAs that have demonstrated a symptomatic hemorrhage in the prior year. Secondary aims shall assess effects on vascular permeability, ROCK activity in peripheral leukocytes, signal effects on clinical outcomes, adverse events, and prespecified subgroups. METHODS The phase I/IIa placebo-controlled, double-blinded, single-site clinical trial aims to enroll 80 subjects randomized 1-1 to atorvastatin (starting dose 80 mg PO daily) or placebo. Dosing shall continue for 24-mo or until reaching a safety endpoint. EXPECTED OUTCOMES The trial is powered to detect an absolute difference of 20% in the mean percent change in lesional QSM per year (2-tailed, power 0.9, alpha 0.05). A decrease in QSM change would be a signal of potential benefit, and an increase would signal a safety concern with the drug. DISCUSSION With firm mechanistic rationale, rigorous preclinical discoveries, and biomarker validations, the trial shall explore a proof of concept effect of a widely used repurposed drug in stabilizing CAs after a symptomatic hemorrhage. This will be the first clinical trial of a drug aimed at altering rebleeding in CA.

The clinical course of cerebral cavernous malformations (CCMs) is highly variable. Based on recent discoveries implicating angiogenic and inflammatory mechanisms, we hypothesized that serum biomarkers might reflect chronic or acute disease activity. This single-site prospective observational cohort study included 85 CCM patients, in whom 24 a priori chosen plasma biomarkers were quantified and analyzed in relation to established clinical and imaging parameters of disease categorization and severity. We subsequently validated the positive correlations in longitudinal follow-up of 49 subjects. Plasma levels of matrix metalloproteinase-2 and intercellular adhesion molecule 1 were significantly higher (P = 0.02 and P = 0.04, respectively, FDR corrected), and matrix metalloproteinase-9 was lower (P = 0.04, FDR corrected) in patients with seizure activity at any time in the past. Vascular endothelial growth factor and endoglin (both P = 0.04, FDR corrected) plasma levels were lower in patients who had suffered a symptomatic bleed in the prior 3 months. The hierarchical clustering analysis revealed a cluster of four plasma inflammatory cytokines (interleukin 2, interferon gamma, tumor necrosis factor alpha, and interleukin 1 beta) separating patients into what we designated "high" and "low" inflammatory states. The "high" inflammatory state was associated with seizure activity (P = 0.02) and more than one hemorrhagic event during a patient's lifetime (P = 0.04) and with a higher rate of new hemorrhage, lesion growth, or new lesion formation (P < 0.05) during prospective follow-up. Peripheral plasma biomarkers reflect seizure and recent hemorrhagic activity in CCM patients. In addition, four clustered inflammatory biomarkers correlate with cumulative disease aggressiveness and predict future clinical activity.

BACKGROUND. Cerebral cavernous angiomas (CAs) with a symptomatic hemorrhage (CASH) have a high risk of recurrent hemorrhage and serious morbidity. METHODS. Eighteen 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. RESULTS. The 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. CONCLUSION. Shared 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.