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

Genetic variants in FCGR2A, PTPN2, VDR as predictive signatures of aggressive phenotypes in cerebral cavernous malformation

OBJECTIVE

The biological behavior of Cerebral Cavernous Malformation (CCM) is still controversial, lacking a clear-cut signature for a mechanistic explanation of lesion aggressiveness. In this study, we evaluated the predictive capacity of genetic variants concerning the aggressive behavior of CCM and their implications in biological processes.

METHODS

We genotyped the variants in VDRrs7975232, VDRrs731236, VDRrs11568820, PTPN2rs72872125 and FCGR2Ars1801274 genes using TaqMan Genotyping Assays in a cohort study with 103 patients, 42 of whom had close follow-up visits for 4 years, focusing on 2 main aspects of the disease: (1) symptomatic events, which included both intracranial bleeding or epilepsy, and (2) the onset of symptoms. The genotypes were correlated with the levels of several cytokines quantified in peripheral blood, measured using the x-MAP method.

RESULTS

We report a novel observation that the PTPN2rs72872125 CT and the VDRrs7975232 CC genotype were independently associated with an asymptomatic phenotype. Additionally, PTPN2rs72872125 CC genotype and serum level of GM-CSF could predict a diagnostic association with symptomatic phenotype in CCM patients, while the FCGR2Ars1801274 GG genotype could predict a symptomatic event during follow-up. The study also found a correlation between VDRrs731236 AA and VDRrs11568820 CC genotype to the time to the first symptomatic event.

CONCLUSIONS

These genetic markers could pave the way for precision medicine strategies for CCM, enhancing patient outcomes by enabling customized therapeutic approaches.

Quantitative susceptibility mapping of brain iron in healthy aging and cognition

Quantitative susceptibility mapping (QSM) is a magnetic resonance imaging (MRI) technique that can assess the magnetic properties of cerebral iron in vivo. Although brain iron is necessary for basic neurobiological functions, excess iron content disrupts homeostasis, leads to oxidative stress, and ultimately contributes to neurodegenerative disease. However, some degree of elevated brain iron is present even among healthy older adults. To better understand the topographical pattern of iron accumulation and its relation to cognitive aging, we conducted an integrative review of 47 QSM studies of healthy aging, with a focus on five distinct themes. The first two themes focused on age-related increases in iron accumulation in deep gray matter nuclei versus the cortex. The overall level of iron is higher in deep gray matter nuclei than in cortical regions. Deep gray matter nuclei vary with regard to age-related effects, which are most prominent in the putamen, and age-related deposition of iron is also observed in frontal, temporal, and parietal cortical regions during healthy aging. The third theme focused on the behavioral relevance of iron content and indicated that higher iron in both deep gray matter and cortical regions was related to decline in fluid (speed-dependent) cognition. A handful of multimodal studies, reviewed in the fourth theme, suggest that iron interacts with imaging measures of brain function, white matter degradation, and the accumulation of neuropathologies. The final theme concerning modifiers of brain iron pointed to potential roles of cardiovascular, dietary, and genetic factors. Although QSM is a relatively recent tool for assessing cerebral iron accumulation, it has significant promise for contributing new insights into healthy neurocognitive aging.

Circulating Plasma miRNA Homologs in Mice and Humans Reflect Familial Cerebral Cavernous Malformation Disease

Patients with familial cerebral cavernous malformation (CCM) inherit germline loss of function mutations and are susceptible to progressive development of brain lesions and neurological sequelae during their lifetime. To date, no homologous circulating molecules have been identified that can reflect the presence of germ line pathogenetic CCM mutations, either in animal models or patients. We hypothesize that homologous differentially expressed (DE) plasma miRNAs can reflect the CCM germline mutation in preclinical murine models and patients. Herein, homologous DE plasma miRNAs with mechanistic putative gene targets within the transcriptome of preclinical and human CCM lesions were identified. Several of these gene targets were additionally found to be associated with CCM-enriched pathways identified using the Kyoto Encyclopedia of Genes and Genomes. DE miRNAs were also identified in familial-CCM patients who developed new brain lesions within the year following blood sample collection. The miRNome results were then validated in an independent cohort of human subjects with real-time-qPCR quantification, a technique facilitating plasma assays. Finally, a Bayesian-informed machine learning approach showed that a combination of plasma levels of miRNAs and circulating proteins improves the association with familial-CCM disease in human subjects to 95% accuracy. These findings act as an important proof of concept for the future development of translatable circulating biomarkers to be tested in preclinical studies and human trials aimed at monitoring and restoring gene function in CCM and other diseases.

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.

Transcriptome Analysis Reveals Altered Expression of Genes Involved in Hypoxia, Inflammation and Immune Regulation in Pdcd10-Depleted Mouse Endothelial Cells

Cerebral cavernous malformations (CCM) are capillary malformations affecting the central nervous system and commonly present with headaches, epilepsy and stroke. Treatment of CCM is symptomatic, and its prevention is limited. CCM are often sporadic but sometimes may be multifocal and/or affect multiple family members. Heterozygous pathogenic variants in PDCD10 cause the rarest and apparently most severe genetic variant of familial CCM. We carried out an RNA-Seq and a Q-PCR validation analysis in Pdcd10-silenced and wild-type mouse endothelial cells in order to better elucidate CCM molecular pathogenesis. Ninety-four differentially expressed genes presented an FDR-corrected p-value < 0.05. A functionally clustered dendrogram showed that differentially expressed genes cluster in cell proliferation, oxidative stress, vascular processes and immune response gene-ontology functions. Among differentially expressed genes, the major cluster fell in signaling related to inflammation and pathogen recognition, including HIF1α and Nos2 signaling and immune regulation. Validation analysis performed on wild-type, Pdcd10-null and Pdcd10-null reconstituted cell lines was consistent with RNA-Seq data. This work confirmed previous mouse transcriptomic data in endothelial cells, which are recognized as a critical tissue for CCM formation and expands the potential molecular signatures of PDCD10-related familial CCM to alterations in inflammation and pathogen recognition pathways.

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.

A novel insight into differential expression profiles of sporadic cerebral cavernous malformation patients with different symptoms

Cerebral cavernous malformation (CCM) is a vascular lesion of the central nervous system that may lead to distinct symptoms among patients including cerebral hemorrhages, epileptic seizures, focal neurologic deficits, and/or headaches. Disease-related mutations were identified previously in one of the three CCM genes: CCM1, CCM2, and CCM3. However, the rate of these mutations in sporadic cases is relatively low, and new studies report that mutations in CCM genes may not be sufficient to initiate the lesions. Despite the growing body of research on CCM, the underlying molecular mechanism has remained largely elusive. In order to provide a novel insight considering the specific manifested symptoms, CCM patients were classified into two groups (as Epilepsy and Hemorrhage). Since the studied patients experience various symptoms, we hypothesized that the underlying cause for the disease may also differ between those groups. To this end, the respective transcriptomes were compared to the transcriptomes of the control brain tissues and among each other. This resulted into the identification of the differentially expressed coding genes and the delineation of the corresponding differential expression profile for each comparison. Notably, some of those differentially expressed genes were previously implicated in epilepsy, cell structure formation, and cell metabolism. However, no CCM1-3 gene deregulation was detected. Interestingly, we observed that when compared to the normal controls, the expression of some identified genes was only significantly altered either in Epilepsy (EGLN1, ELAVL4, and NFE2l2) or Hemorrhage (USP22, EYA1, SIX1, OAS3, SRMS) groups. To the best of our knowledge, this is the first such effort focusing on CCM patients with epileptic and hemorrhagic symptoms with the purpose of uncovering the potential CCM-related genes. It is also the first report that presents a gene expression dataset on Turkish CCM patients. The results suggest that the new candidate genes should be explored to further elucidate the CCM pathology. Overall, this work constitutes a step towards the identification of novel potential genetic targets for the development of possible future therapies.

CCM2-deficient endothelial cells undergo a ROCK-dependent reprogramming into senescence-associated secretory phenotype

Cerebral cavernous malformation (CCM) is a cerebrovascular disease in which stacks of dilated haemorrhagic capillaries form focally in the brain. Whether and how defective mechanotransduction, cellular mosaicism and inflammation interplay to sustain the progression of CCM disease is unknown. Here, we reveal that CCM1- and CCM2-silenced endothelial cells expanded in vitro enter into senescence-associated secretory phenotype (SASP) that they use to invade the extracellular matrix and attract surrounding wild-type endothelial and immune cells. Further, we demonstrate that this SASP is driven by the cytoskeletal, molecular and transcriptomic disorders provoked by ROCK dysfunctions. By this, we propose that CCM2 and ROCK could be parts of a scaffold controlling senescence, bringing new insights into the emerging field of the control of ageing by cellular mechanics. These in vitro findings reconcile the known dysregulated traits of CCM2-deficient endothelial cells into a unique endothelial fate. Based on these in vitro results, we propose that a SASP could link the increased ROCK-dependent cell contractility in CCM2-deficient endothelial cells with microenvironment remodelling and long-range chemo-attraction of endothelial and immune cells.