High prevalence of KRAS/BRAF somatic mutations in brain and spinal cord arteriovenous malformations

Identification of Somatic Genetic Variants in Superficial Vascular Malformations by Liquid Biopsy in a Cohort of 88 Patients from a French Hospital

BACKGROUND AND OBJECTIVE

Superficial vascular anomalies are complex disorders characterized by abnormal vascular growth. Next-generation sequencing has recently identified somatic genetic alterations associated with these malformations, offering new insights for targeted treatments. However, tissue biopsies for genetic testing can be invasive and difficult to obtain, especially in arteriovenous malformations (AVM) with hemorrhagic risks. A liquid biopsy, a non-invasive approach, offers a promising solution by detecting genetic mutations in cell-free DNA. This pilot study aimed to evaluate the feasibility of using a liquid biopsy for the genetic analysis of patients with superficial vascular anomalies through cell-free DNA sampling. Additionally, it explored whether specific sampling sites, such as the afferent artery, nidus, and efferent vein, could enhance the sensitivity of detecting pathogenic variants in patients with AVM.

METHODS

A total of 88 patients were enrolled, including 55 with AVM and 33 with lymphatic malformations. For patients with AVM, cell-free DNA samples were collected from peripheral blood, efferent veins, afferent arteries, and the AVM nidus. In patients with lymphatic malformations, cystic lymphatic fluid was collected by a direct puncture during diagnostic procedures. A molecular analysis was performed using a targeted gene panel relevant to somatic alterations in solid tumors. Pathogenic variants were validated by digital polymerase chain reaction for patients with lymphatic malformations.

RESULTS

Pathogenic variants were identified in 23.6% of patients with AVM, predominantly in MAP2K1 and KRAS genes, with higher sensitivity near the AVM nidus. In addition, pathogenic variants were identified in 27.3% of patients with lymphatic malformations, all involving the PIK3CA gene. Despite the lower sensitivity of a cell-free DNA analysis compared with a tissue biopsy, especially in patients with AVM, the detection rate suggests the utility for a cell-free DNA analysis, particularly when a tissue biopsy is not feasible.

CONCLUSIONS

This study confirms the feasibility of using a cell-free DNA liquid biopsy for genotyping patients with superficial vascular anomalies, although a tissue biopsy remains the gold standard for comprehensive genetic profiling because of its higher sensitivity. A liquid biopsy offers a non-invasive option for molecular analysis that is useful as a preliminary or alternative approach when direct tissue sampling is not possible. Importantly, the sensitivity of cell-free DNA sampling in AVM appeared highest when obtained close to the nidus, indicating an optimal sampling location for future studies. Further research is needed to improve detection sensitivity, especially for samples taken near the nidus, to validate and strengthen these findings. Although our study focused on superficial/extra-cranial AVM, further research should assess the applicability of this approach to cerebral AVM, where a tissue biopsy is particularly risky.

RAS Pathway Mutations and Therapeutics in Vascular Anomalies

Vascular anomalies (VAs) are a diverse group of vascular tumors and vascular malformations (VMs). VMs are characterized by abnormal vessel development, overgrowth, and dysfunction. Coagulopathy, edema, and effusions can cause severe morbidity and mortality in children and adults with these diseases. Germline or somatic mutations in the RAS/RAF/MAPK pathway have been identified in multiple types of VAs. RAS genes (KRAS, NRAS, and HRAS) are small GTPase proteins that play an important role in normal development and cell function. In healthy cells, RAS proteins cycle between GDP (inactive) and GTP (active) states that regulate important functions such as proliferation, migration, and survival. "Hot spot" mutations in codons 12, 13, or 61 of RAS genes are found in multiple tumor types and VAs. RAS mutations often cause excessive MAP kinase signaling, driving unchecked cell proliferation. In this review, we discuss the different RAS pathway mutations discovered in VAs and the role that these may play using insights from cell and animal models. Current therapies targeting RAS pathways are presented. In the future, a better understanding of the role of RAS pathway mutations may advance therapeutic strategies for people with VAs.

Advances in sporadic brain arteriovenous malformations: Novel genetic insights, innovative animal models and emerging therapeutic approaches

Brain arteriovenous malformations (bAVMs) are a notable cause of intracranial hemorrhage, strongly associated with severe morbidity and mortality. Contemporary treatment options include surgery, stereotactic radiosurgery, and endovascular embolization, each of which has limitations. Hence, development of pharmacological interventions is urgently needed. The recent discovery of the presence of activating Kirsten rat sarcoma (KRAS) viral oncogene homologue mutations in most sporadic bAVMs has opened the door for a more comprehensive understanding of the pathogenesis of bAVMs and has pointed to entirely novel possible therapeutic targets. Herein, we review the status quo of genetics, animal models, and therapeutic approaches in bAVMs.

Neuroinflammation and hypoxia promote astrocyte phenotypic transformation and propel neurovascular dysfunction in brain arteriovenous malformation

Brain arteriovenous malformation (BAVM) is a complex cerebrovascular disease characterized by an abnormal high-flow vascular network, which increases the risk of hemorrhage, particularly in young individuals. Endothelial dysfunction has traditionally been considered the primary cause, while the contributions of the microenvironment and glial cells have not been fully explored. Astrocytes, as a key component of the central nervous system, play a crucial role in regulating neurovascular function, maintaining the integrity of the blood-brain barrier, and ensuring neural homeostasis. However, under the pathological conditions of BAVM, the phenotypic changes in astrocytes and their role in disease progression remain poorly understood. In our study, we emphasized the critical role of neuroinflammation and hypoxia in the progression of BAVM within its pathological microenvironment. Specifically, reactive astrocytes undergo phenotypic changes under these pathological conditions, significantly promoting vascular instability. Moreover, nitric oxide (NO) produced by BAVM endothelial cells activates signaling pathways that stabilize HIF-1α in astrocytes, initiating a "hypoxic" gene program under normoxic conditions. Furthermore, we discovered that COX-2, a direct target gene of HIF-1α, is upregulated in the BAVM microenvironment. These changes promoted endothelial dysfunction and vascular fragility, creating a vicious cycle that exacerbates hemorrhage risk. The application of COX-2 inhibitors significantly reduced neuroinflammation, stabilized blood vessels, and decreased hemorrhage risk. Our findings highlighted the crucial interaction between the BAVM microenvironment and astrocytes in driving disease progression, suggesting that COX-2 could be a potential therapeutic target for stabilizing BAVM vessels and reducing hemorrhagic events.

Local DIO2 Elevation Is an Adaption in Malformed Cerebrovasculature

BACKGROUND

Cerebrovascular malformations are a pivotal cause of hemorrhage and neurological disability alongside lacking effective medication. Thyroid hormones (THs), including thyroxine and triiodothyronine, are essential for vascular development, yet whether they participate in malformed cerebrovascular pathology remains elusive.

METHODS

Single-cell transcriptome analysis characterized human cerebral cavernous malformations and brain arteriovenous malformations, 2 typical cerebrovascular malformation diseases. Adeno-associated virus-mediated Dio2 (iodothyronine deiodinase 2; an enzyme that converts thyroxine to active triiodothyronine) overexpression/knockdown or triiodothyronine/methimazole (an antithyroid drug) treatment was applied to mouse models of cerebral cavernous malformations (endothelial-specific Pdcd10 knockout mice, Pdcd10 endothelial-specific knockout [KO]) and brain arteriovenous malformations (endothelial-specific KrasG12D mutant mice, KrasG12D) to evaluate the involvement of DIO2 and TH signaling in cerebrovascular malformations.

RESULTS

TH signaling was markedly activated in fibroblasts of human cerebral cavernous malformation and arteriovenous malformation single-cell samples, accompanied by elevated DIO2 expression. Similar DIO2 upregulation was observed in cerebrovascular fibroblasts of Pdcd10 KO/KrasG12D mice and patient brain sections. Exogenous Dio2 or triiodothyronine replenishment effectively reduced brain hemorrhage, excessive ECM (extracellular matrix) remodeling, and vascular leakage in juvenile and adult male and female Pdcd10 KO/KrasG12D mice. In contrast, Dio2 silencing or TH inhibition deteriorated vascular anomalies. Mechanistically, transcription factor FOXK1 (forkhead box K1) was determined to interact with the DIO2 promoter region. The activation of fibroblast PI3K (phosphoinositide 3-kinase)-Akt (protein kinase B)-mTOR (mammalian target of rapamycin) signaling in Pdcd10 KO/KrasG12D mice triggered Foxk1 nuclear translocation to promote Dio2 transcription. Triiodothyronine treatment mitigated inflammatory infiltration, normalized mitochondrial morphology, and restored mitochondrial biogenesis in malformed brain vessels by activating the Pgc1a (peroxisome proliferator-activated receptor gamma coactivator 1-alpha)-Sod2 (superoxide dismutase 2)/Prdx3 (peroxiredoxin 3)/Gpx1 (glutathione peroxidase 1) axis to reduce reactive oxygen species accumulation. We also determined that the vascular repair effects of triiodothyronine were Pgc1a-dependent.

CONCLUSIONS

We delineate a novel DIO2-mediated adaption in malformed cerebrovasculature and conclude that targeting TH signaling may represent a potential therapy for cerebrovascular disorders.

Metabolic reprogramming in cancer and senescence

The rising trend in global cancer incidence has caused widespread concern, one of the main reasons being the aging of the global population. Statistical data show that cancer incidence and mortality rates show a clear upward trend with age. Although there is a commonality between dysregulated nutrient sensing, which is one of the main features of aging, and metabolic reprogramming of tumor cells, the specific regulatory relationship is not clear. This manuscript intends to comprehensively analyze the relationship between senescence and tumor metabolic reprogramming; as well as reveal the impact of key factors leading to cellular senescence on tumorigenesis. In addition, this review summarizes the current intervention strategies targeting nutrient sensing pathways, as well as the clinical cases of treating tumors targeting the characteristics of senescence with the existing nanodelivery research strategies. Finally, it also suggests sensible dietary habits for those who wish to combat aging. In conclusion, this review attempts to sort out the link between aging and metabolism and provide new ideas for cancer treatment.

From bench to bedside: murine models of inherited and sporadic brain arteriovenous malformations

Brain arteriovenous malformations are abnormal vascular structures in which an artery shunts high pressure blood directly to a vein without an intervening capillary bed. These lesions become highly remodeled over time and are prone to rupture. Historically, brain arteriovenous malformations have been challenging to treat, using primarily surgical approaches. Over the past few decades, the genetic causes of these malformations have been uncovered. These can be divided into (1) familial forms, such as loss of function mutations in TGF-β (BMP9/10) components in hereditary hemorrhagic telangiectasia, or (2) sporadic forms, resulting from somatic gain of function mutations in genes involved in the RAS-MAPK signaling pathway. Leveraging these genetic discoveries, preclinical mouse models have been developed to uncover the mechanisms underlying abnormal vessel formation, and thus revealing potential therapeutic targets. Impressively, initial preclinical studies suggest that pharmacological treatments disrupting these aberrant pathways may ameliorate the abnormal pathologic vessel remodeling and inflammatory and hemorrhagic nature of these high-flow vascular anomalies. Intriguingly, these studies also suggest uncontrolled angiogenic signaling may be a major driver in bAVM pathogenesis. This comprehensive review describes the genetics underlying both inherited and sporadic bAVM and details the state of the field regarding murine models of bAVM, highlighting emerging therapeutic targets that may transform our approach to treating these devastating lesions.

Subarachnoid hemorrhage triggered by spinal cord vascular malformation in a pediatric patient: case report and review of literature

Background

Spinal cord vascular malformations (SCVMs) in children are relatively rare and present unique challenges due to their distinct physiological characteristics. These malformations often manifest with nonspecific clinical symptoms, increasing the likelihood of misdiagnosis. The treatment of pediatric SCVMs requires a tailored approach, with the choice between microsurgical intervention and endovascular embolization depending on the specific type of malformation and individual patient factors.

Case report

We report a case of a 6-year-old male who presented with a sudden onset of headache. Initial cranial imaging did not reveal any significant intracranial vascular malformations. However, thoracic spine magnetic resonance imaging (MRI) identified an abnormal signal, and digital subtraction angiography (DSA) confirmed the diagnosis of SCVMs. The patient underwent microsurgical treatment and was discharged in good health. Follow-up DSA confirmed the complete resolution of the vascular malformations.

Conclusion

This case, along with a review of the literature, underscores the importance of thorough spinal evaluations in pediatric patients with spontaneous intracranial hemorrhage, especially when intracranial vascular malformations are not identified. A high index of suspicion for SCVMs is crucial. Early and accurate diagnosis, followed by appropriate treatment through microsurgical resection or endovascular embolization, can significantly improve therapeutic outcomes in children with SCVMs.

Somatic Mosaicism in Brain Disorders

Research efforts over the past decade have defined the genetic landscape of somatic variation in the brain. Neurons accumulate somatic mutations from development through aging with potentially profound functional consequences. Recent studies have revealed the contribution of somatic mosaicism to various brain disorders including focal epilepsy, neuropsychiatric disease, and neurodegeneration. One notable finding is that the effect of somatic mosaicism on clinical outcomes can vary depending on contextual factors, such as the developmental origin of a variant or the number and type of cells affected. In this review, we highlight current knowledge regarding the role of somatic mosaicism in brain disorders and how biological context can mediate phenotypes. First, we identify the origins of brain somatic variation throughout the lifespan of an individual. Second, we explore recent discoveries that suggest somatic mosaicism contributes to various brain disorders. Finally, we discuss neuropathological associations of brain mosaicism in different biological contexts and potential clinical utility.

Inhibition of Angiopoietin-2 rescues sporadic brain arteriovenous malformations by reducing pericyte loss

Brain arteriovenous malformations (bAVMs) are a major cause of hemorrhagic stroke in children and young adults. These lesions are thought to result from somatic KRAS/BRAF mutations in brain endothelial cells (bECs). In this study, we introduce a new bAVM model by inducing a brain endothelial-specific BrafV600E mutation using the Slc1o1c1(BAC)-CreER driver line. The pathological characteristics of this model resemble human bAVMs, including dilated and hyperpermeable vessels, as well as parenchymal hemorrhage. We observed that these lesions showed a typical reduction in pericyte coverage and disruption of the pericyte-endothelial cell connection. Additionally, we found that ANGPT2 levels were significantly increased in the endothelium of bAVM lesions, which may be a critical factor in the pericyte deficits of the malformed vessels. Treatment with an ANGPT2 neutralizing antibody confirmed that blocking ANGPT2 can restore pericyte density in bAVM lesions, improve pericyte coverage around microvessels, enhance tight junction protein coverage related to endothelial cells, and normalize endothelial barrier function. In summary, our findings suggest that increased ANGPT2 expression in endothelial cells with the BrafV600E mutation is a key factor in pericyte deficiencies in bAVMs, highlighting the potential effectiveness of anti-ANGPT2 therapy in treating bAVMs.

Untangling sporadic brain arteriovenous malformations: towards targeting the KRAS/MAPK pathway

Brain arteriovenous malformations (AVMs) are vascular lesions characterized by abnormal connections between parenchymal arteries and veins, bypassing a capillary bed, and forming a nidus. Brain AVMs are consequential as they are prone to rupture and associated with significant morbidity. They can broadly be subdivided into hereditary vs. sporadic lesions with sporadic brain AVMs representing the majority of all brain AVMs. However, little had been known about the pathogenesis of sporadic brain AVMs until the landmark discovery in 2018 that the majority of sporadic brain AVMs carry somatic activating mutations of the oncogene, Kirsten rat sarcoma viral oncogene homologue (KRAS), in their endothelial cells. Here, we review the history of brain AVMs, their treatments, and recent advances in uncovering the pathogenesis of sporadic brain AVMs. We specifically focus on the latest studies suggesting that pharmacologically targeting the KRAS/MEK pathway may be a potentially efficacious treatment for sporadic brain AVMs.

Cerebral vascular malformations: pathogenesis and therapy

Cerebral vascular malformations (CVMs), particularly cerebral cavernous malformations and cerebral arteriovenous malformations, pose significant neurological challenges due to their complex etiologies and clinical implications. Traditionally viewed as congenital conditions with structural abnormalities, CVMs have been treated primarily through resection, embolization, and stereotactic radiosurgery. While these approaches offer some efficacy, they often pose risks to neurological integrity due to their invasive nature. Advances in next-generation sequencing, particularly high-depth whole-exome sequencing and bioinformatics, have facilitated the identification of gene variants from neurosurgically resected CVMs samples. These advancements have deepened our understanding of CVM pathogenesis. Somatic mutations in key mechanistic pathways have been identified as causative factors, leading to a paradigm shift in CVM treatment. Additionally, recent progress in noninvasive and minimally invasive techniques, including gene imaging genomics, liquid biopsy, or endovascular biopsies (endovascular sampling of blood vessel lumens), has enabled the identification of gene variants associated with CVMs. These methods, in conjunction with clinical data, offer potential for early detection, dynamic monitoring, and targeted therapies that could be used as monotherapy or adjuncts to surgery. This review highlights advancements in CVM pathogenesis and precision therapies, outlining the future potential of precision medicine in CVM management.

CRISPR/CasRx suppresses KRAS-induced brain arteriovenous malformation developed in postnatal brain endothelial cells in mice

Brain arteriovenous malformations (bAVMs) are anomalies forming vascular tangles connecting the arteries and veins, which cause hemorrhagic stroke in young adults. Current surgical approaches are highly invasive, and alternative therapeutic methods are warranted. Recent genetic studies identified KRAS mutations in endothelial cells of bAVMs; however, the underlying process leading to malformation in the postnatal stage remains unknown. Here we established a mouse model of bAVM developing during the early postnatal stage. Among 4 methods tested, mutant KRAS specifically introduced in brain endothelial cells by brain endothelial cell-directed adeno-associated virus (AAV) and endothelial cell-specific Cdh5-CreERT2 mice successfully induced bAVMs in the postnatal period. Mutant KRAS led to the development of multiple vascular tangles and hemorrhage in the brain with increased MAPK/ERK signaling and growth in endothelial cells. Three-dimensional analyses in cleared tissue revealed dilated vascular networks connecting arteries and veins, similar to human bAVMs. Single-cell RNA-Seq revealed dysregulated gene expressions in endothelial cells and multiple cell types involved in the pathological process. Finally, we employed CRISPR/CasRx to knock down mutant KRAS expression, which efficiently suppressed bAVM development. The present model reveals pathological processes that lead to postnatal bAVMs and demonstrates the efficacy of therapeutic strategies with CRISPR/CasRx.

Pediatric Spinal Vascular Abnormalities: Overview, Diagnosis, and Management

Hemangioblastomas are true benign vascular neoplasms arising from pluripotent mesenchymal stem cells that give rise to vascular endothelial cells and are most commonly found in the cerebellum, spinal cord, brainstem, and retina. These tumors may be isolated sporadic lesions or may be associated with hereditary genetic factors in the case of von Hippel-Lindau (VHL) syndrome. Spinal cord haemangioblastomas constitute 1.1% to 2.4% of all central nervous system tumors105, with the majority being single tumors that present in the fourth decade of life 106. In the pediatric population, sporadic spinal cord hemangioblastomas are exceedingly rare. The prevalence of spinal cord hemangioblastomas in children is increased among those with VHL syndrome. The thoracic cord is the most common site for spinal cord hemangioblastomas, followed by the cervical cord. Although these tumors are benign, they cause disabling symptoms due to spinal cord compression, syringomyelia, or hemorrhage from the tumor itself or from aneurysms that form on tumor-feeding arteries or intra-tumoral vessels.

A Simple Model to Study Mosaic Gene Expression in 3D Endothelial Spheroids

AIMS

The goal of this study was to establish a simple model of 3D endothelial spheroids with mosaic gene expression using adeno-associated virus (AAV) transduction, with a future aim being to study the activity of post-zygotic mutations common to vascular malformations.

METHODS

In this study, 96-well U-bottom plates coated with a commercial repellent were seeded with two immortalized human endothelial cell lines and aggregation monitored using standard microscopy or live-cell analysis. The eGFP expression was used to monitor the AAV transduction.

RESULTS

HUVEC-TERT2 could not form spheroids spontaneously. The inclusion of collagen I in the growth medium could stimulate cell aggregation; however, these spheroids were not stable. In contrast, the hCMEC/D3 cells aggregated spontaneously and formed reproducible, robust 3D spheroids within 3 days, growing steadily for at least 4 weeks without the need for media refreshment. The hCMEC/D3 spheroids spontaneously developed a basement membrane, including collagen I, and expressed endothelial-specific CD31 at the spheroid surface. Serotypes AAV1 and AAV2QUADYF transduced these spheroids without toxicity and established sustained, mosaic eGFP expression.

CONCLUSIONS

In the future, this simple approach to endothelial spheroid formation combined with live-cell imaging could be used to rapidly assess the 3D phenotypes and drug and radiation sensitivities arising from mosaic mutations common to brain vascular malformations.

Surgical timing and long-term outcomes in patients with severe haemorrhagic spinal cord cavernous malformations

BACKGROUND

Surgical resection of the lesions remains the main treatment method for most symptomatic spinal cord cavernous malformations (SCCMs) to eliminate the occupation and associated subsequent lifelong haemorrhagic risk. However, the timing of surgical intervention remains controversial, especially for patients in the acute stage after severe haemorrhage.

METHODS

Patients diagnosed with SCCMs who were surgically treated between January 2002 and December 2021 were selected and retrospectively reviewed. The Modified McCormick Scale (MMS) was used to evaluate neurological and disability status. All medical information was reviewed, and all patients were followed up for at least 6 months.

RESULTS

A total of 279 patients were ultimately included. With regard to long-term outcomes, 110 (39.4%) patients improved, 159 (57.0%) remained unchanged and 10 (3.6%) worsened. For patients with an MMS score of 2-5 on admission, in univariate and multivariate analyses, a ≤6 weeks period between onset and surgery (adjusted OR 3.211, 95% CI 1.504 to 6.856, p=0.003) was a significant predictor of improved MMS. Among 69 patients who first presented with severe haemorrhage, undergoing surgery within 6 weeks of the onset of severe haemorrhage (adjusted OR 4.901, 95% CI 1.126 to 21.325, p=0.034) was significantly associated with improvement of MMS score.

CONCLUSION

Surgical timing can influence the long-term outcome of SCCMs. For patients with symptomatic SCCMs, especially those with severe haemorrhage, early surgical intervention within 6 weeks can provide more benefit.

Pathophysiology in Brain Arteriovenous Malformations: Focus on Endothelial Dysfunctions and Endothelial-to-Mesenchymal Transition

Brain arteriovenous malformations (bAVMs) substantially increase the risk for intracerebral hemorrhage (ICH), which is associated with significant morbidity and mortality. However, the treatment options for bAVMs are severely limited, primarily relying on invasive methods that carry their own risks for intraoperative hemorrhage or even death. Currently, there are no pharmaceutical agents shown to treat this condition, primarily due to a poor understanding of bAVM pathophysiology. For the last decade, bAVM research has made significant advances, including the identification of novel genetic mutations and relevant signaling in bAVM development. However, bAVM pathophysiology is still largely unclear. Further investigation is required to understand the detailed cellular and molecular mechanisms involved, which will enable the development of safer and more effective treatment options. Endothelial cells (ECs), the cells that line the vascular lumen, are integral to the pathogenesis of bAVMs. Understanding the fundamental role of ECs in pathological conditions is crucial to unraveling bAVM pathophysiology. This review focuses on the current knowledge of bAVM-relevant signaling pathways and dysfunctions in ECs, particularly the endothelial-to-mesenchymal transition (EndMT).

Somatic BrafV600E mutation in the cerebral endothelium induces brain arteriovenous malformations

Current treatments of brain arteriovenous malformation (BAVM) are associated with considerable risks and at times incomplete efficacy. Therefore, a clinically consistent animal model of BAVM is urgently needed to investigate its underlying biological mechanisms and develop innovative treatment strategies. Notably, existing mouse models have limited utility due to heterogenous and untypical phenotypes of AVM lesions. Here we developed a novel mouse model of sporadic BAVM that is consistent with clinical manifestations in humans. Mice with BrafV600E mutations in brain ECs developed BAVM closely resembled that of human lesions. This strategy successfully induced BAVMs in mice across different age groups and within various brain regions. Pathological features of BAVM were primarily dilated blood vessels with reduced vascular wall stability, accompanied by spontaneous hemorrhage and neuroinflammation. Single-cell sequencing revealed differentially expressed genes that were related to the cytoskeleton, cell motility, and intercellular junctions. Early administration of Dabrafenib was found to be effective in slowing the progression of BAVMs; however, its efficacy in treating established BAVM lesions remained uncertain. Taken together, our proposed approach successfully induced BAVM that closely resembled human BAVM lesions in mice, rendering the model suitable for investigating the pathogenesis of BAVM and assessing potential therapeutic strategies.

Sotorasib for Vascular Malformations Associated with KRAS G12C Mutation

KRAS gain-of-function mutations are frequently observed in sporadic arteriovenous malformations. The mechanisms underlying the progression of such KRAS-driven malformations are still incompletely understood, and no treatments for the condition are approved. Here, we show the effectiveness of sotorasib, a specific KRAS G12C inhibitor, in reducing the volume of vascular malformations and improving survival in two mouse models carrying a mosaic Kras G12C mutation. We then administered sotorasib to two adult patients with severe KRAS G12C-related arteriovenous malformations. Both patients had rapid reductions in symptoms and arteriovenous malformation size. Targeting KRAS G12C appears to be a promising therapeutic approach for patients with KRAS G12C-related vascular malformations. (Funded by the European Research Council and others.).

Defining the Role of Oral Pathway Inhibitors as Targeted Therapeutics in Arteriovenous Malformation Care

Arteriovenous malformations (AVMs) are vascular malformations that are prone to rupturing and can cause significant morbidity and mortality in relatively young patients. Conventional treatment options such as surgery and endovascular therapy often are insufficient for cure. There is a growing body of knowledge on the genetic and molecular underpinnings of AVM development and maintenance, making the future of precision medicine a real possibility for AVM management. Here, we review the pathophysiology of AVM development across various cell types, with a focus on current and potential druggable targets and their therapeutic potentials in both sporadic and familial AVM populations.

An Updated Review on the Pathogenesis of Brain Arteriovenous Malformations and Its Therapeutic Targets

Brain arteriovenous malformations (bAVMs) are associated with a high risk of intracerebral hemorrhage, which causes severe complications in patients. Although the genetic factors leading to hereditary bAVMs have been extensively investigated, their pathogenesis are still under study. This review examines updated data on the molecular and genetic aspects of bAVMs, the architecture of microvasculature, the roles of angiogenic factors, and signaling pathways. The compiled information may help us understand the pathogenesis of both sporadic and hereditary bAVMs and develop appropriate preemptive treatment approaches.

MEK signaling represents a viable therapeutic vulnerability of KRAS-driven somatic brain arteriovenous malformations

Brain arteriovenous malformations (bAVMs) are direct connections between arteries and veins that remodel into a complex nidus susceptible to rupture and hemorrhage. Most sporadic bAVMs feature somatic activating mutations within KRAS, and endothelial-specific expression of the constitutively active variant KRASG12D models sporadic bAVM in mice. By leveraging 3D-based micro-CT imaging, we demonstrate that KRASG12D-driven bAVMs arise in stereotypical anatomical locations within the murine brain, which coincide with high endogenous Kras expression. We extend these analyses to show that a distinct variant, KRASG12C, also generates bAVMs in predictable locations. Analysis of 15,000 human patients revealed that, similar to murine models, bAVMs preferentially occur in distinct regions of the adult brain. Furthermore, bAVM location correlates with hemorrhagic frequency. Quantification of 3D imaging revealed that G12D and G12C alter vessel density, tortuosity, and diameter within the mouse brain. Notably, aged G12D mice feature increased lethality, as well as impaired cognition and motor function. Critically, we show that pharmacological blockade of the downstream kinase, MEK, after lesion formation ameliorates KRASG12D-driven changes in the murine cerebrovasculature and may also impede bAVM progression in human pediatric patients. Collectively, these data show that distinct KRAS variants drive bAVMs in similar patterns and suggest MEK inhibition represents a non-surgical alternative therapy for sporadic bAVM.

Most Promising Approaches to Improve Brain AVM Management: ARISE I Consensus Recommendations

Brain arteriovenous malformations (bAVMs) are complex, and rare arteriovenous shunts that present with a wide range of signs and symptoms, with intracerebral hemorrhage being the most severe. Despite prior societal position statements, there is no consensus on the management of these lesions. ARISE (Aneurysm/bAVM/cSDH Roundtable Discussion With Industry and Stroke Experts) was convened to discuss evidence-based approaches and enhance our understanding of these complex lesions. ARISE identified the need to develop scales to predict the risk of rupture of bAVMs, and the use of common data elements to perform prospective registries and clinical studies. Additionally, the group underscored the need for comprehensive patient management with specialized centers with expertise in cranial and spinal microsurgery, neurological endovascular surgery, and stereotactic radiosurgery. The collection of prospective multicenter data and gross specimens was deemed essential for improving bAVM characterization, genetic evaluation, and phenotyping. Finally, bAVMs should be managed within a multidisciplinary framework, with clinical studies and research conducted collaboratively across multiple centers, harnessing the collective expertise and centralization of resources.

GPRASP1 loss-of-function links to arteriovenous malformations by endothelial activating GPR4 signals

Arteriovenous malformations (AVMs) are fast-flow vascular malformations and refer to important causes of intracerebral haemorrhage in young adults. Getting deep insight into the genetic pathogenesis of AVMs is necessary. Herein, we identified two vital missense variants of G protein-coupled receptor (GPCR) associated sorting protein 1 (GPRASP1) in AVM patients for the first time and congruously determined to be loss-of-function variants in endothelial cells. GPRASP1 loss-of-function caused endothelial dysfunction in vitro and in vivo. Endothelial Gprasp1 knockout mice suffered a high probability of cerebral haemorrhage, AVMs and exhibited vascular anomalies in multiple organs. GPR4 was identified to be an effective GPCR binding with GPRASP1 to develop endothelial disorders. GPRASP1 deletion activated GPR4/cAMP/MAPK signalling to disturb endothelial functions, thus contributing to vascular anomalies. Mechanistically, GPRASP1 promoted GPR4 degradation. GPRASP1 enabled GPR4 K63-linked ubiquitination, enhancing the binding of GPR4 and RABGEF1 to activate RAB5 for conversions from endocytic vesicles to endosomes, and subsequently increasing the interactions of GPR4 and ESCRT members to package GPR4 into multivesicular bodies or late endosomes for lysosome degradation. Notably, the GPR4 antagonist NE 52-QQ57 and JNK inhibitor SP600125 effectively rescued the vascular phenotype caused by endothelial Gprasp1 deletion. Our findings provided novel insights into the roles of GPRASP1 in AVMs and hinted at new therapeutic strategies.

Updates in Genetic Testing for Head and Neck Vascular Anomalies

Vascular anomalies include benign or malignant tumors or benign malformations of the arteries, veins, capillaries, or lymphatic vasculature. The genetic etiology of the lesion is essential to define the lesion and can help navigate choice of therapy. . In the United States, about 1.2% of the population has a vascular anomaly, which may be underestimating the true prevalence as genetic testing for these conditions continues to evolve.

Lymphatic Malformations in Parkes Weber's Syndrome: Retrospective Review of 16 Cases in a Vascular Anomalies Center

INTRODUCTION

 Parkes Weber's syndrome (PWS) is a rare genetic disorder characterized by overgrowth and vascular malformations, primarily affecting the extremities. While PWS is known to be associated with arteriovenous and capillary malformations, the potential involvement of lymphatic malformations (LMs) has not been previously reported. The objective of this study is to investigate the presence of lymphatic anomalies in PWS patients and their role in the development of limb asymmetry.

MATERIALS AND METHODS

 This is a retrospective study of patients diagnosed with PWS in a Vascular Anomalies Center from 1994 to 2020. Clinical data were obtained from medical records including diagnostic imaging, lymphoscintigraphy, and genetic testing. The Institutional Review Board and Ethics Committee have approved this study.

RESULTS

 A total of 16 patients aged 18 interquartile range 14.7 years diagnosed with PWS were included (50% female). Six of the 16 patients with PWS had clinical and imaging data suggestive of LM (37.5%) and 3 of them had genetic variants in RASA1 (2/3) or KRAS (1/3). Limb asymmetry was greater in patients with isolated PWS (2.6 ± 0.8 cm) than in the PWS-lymphatic anomalies population (2 ± 0.7 cm), although not significant (p = 0.247). One in 6 patients with PWS-LM required amputation (16.6%) versus 1 in 10 in isolated PWS (10%).

CONCLUSION

 Lymphatic anomalies may be present in a significant number of patients with PWS and could have a role in limb asymmetry and outcomes. It is paramount to investigate their existence and distinguish them from true overgrowth.

The expansion of liquid biopsies to vascular care: an overview of existing principles, techniques and potential applications to vascular malformation diagnostics

Vascular malformations are congenital lesions that occur due to mutations in major cellular signalling pathways which govern angiogenesis, cell proliferation, motility, and cell death. These pathways have been widely studied in oncology and are substrates for various small molecule inhibitors. Given their common molecular biology, there is now a potential to repurpose these cancer drugs for vascular malformation care; however, a molecular diagnosis is required in order to tailour specific drugs to the individual patient's mutational profile. Liquid biopsies (LBs), emerging as a transformative tool in the field of oncology, hold significant promise in this feat. This paper explores the principles and technologies underlying LBs and evaluates their potential to revolutionize the management of vascular malformations. The review begins by delineating the fundamental principles of LBs, focusing on the detection and analysis of circulating biomarkers such as cell-free DNA, circulating tumor cells, and extracellular vesicles. Subsequently, an in-depth analysis of the technological advancements driving LB platforms is presented. Lastly, the paper highlights the current state of research in applying LBs to various vascular malformations, and uses the aforementioned principles and techniques to conceptualize a liquid biopsy framework that is unique to vascular malformation research and clinical care.

Current perspectives and trends in the treatment of brain arteriovenous malformations: a review and bibliometric analysis

Background

Currently, there is a lack of intuitive analysis regarding the development trend, main authors, and research hotspots in the field of cerebral arteriovenous malformation treatment, as well as a detailed elaboration of possible research hotspots.

Methods

A bibliometric analysis was conducted on data retrieved from the Web of Science core collection database between 2000 and 2022. The analysis was performed using R, VOSviewer, CiteSpace software, and an online bibliometric platform.

Results

A total of 1,356 articles were collected, and the number of publications has increased over time. The United States and the University of Pittsburgh are the most prolific countries and institutions in the field. The top three cited authors are Kondziolka D, Sheehan JP, and Lunsford LD. The Journal of Neurosurgery and Neurosurgery are two of the most influential journals in the field of brain arteriovenous malformation treatment research, with higher H-index, total citations, and number of publications. Furthermore, the analysis of keywords indicates that "aruba trial," "randomised trial," "microsurgery," "onyx embolization," and "Spetzler-Martin grade" may become research focal points. Additionally, this paper discusses the current research status, existing issues, and potential future research directions for the treatment of brain arteriovenous malformations.

Conclusion

This bibliometric study comprehensively analyses the publication trend of cerebral arteriovenous malformation treatment in the past 20 years. It covers the trend of international cooperation, publications, and research hotspots. This information provides an important reference for scholars to further study cerebral arteriovenous malformation.

Clarifying the clinical landscape of pediatric spinal arteriovenous shunts: an institutional experience and individual patient-data meta-analysis

BACKGROUND

Pediatric spinal arteriovenous shunts (SAVS) are rare lesions with heterogeneous pathogenesis and clinical manifestations.

OBJECTIVE

To evaluate the clinical characteristics, angioarchitecture, and technical/clinical outcomes in SAVS through a large single-center cohort analysis and meta-analysis of individual patient data.

METHODS

A retrospective institutional database identified children (aged 0-21 years) who underwent digital subtraction spinal angiography (DSA) for SAVS between January 1996 and July 2021. Clinical data were recorded to evaluate angioarchitecture, generate modified Aminoff-Logue gait disturbance scores (AL) and McCormick grades (MC), and assess outcomes. We then performed a systematic literature review following PRISMA-IPD (Preferred Reporting Items for Systematic Reviews and Meta-Analyses for individual patient data) guidelines, extracting similar data on individual patients for meta-analysis.

RESULTS

The cohort consisted of 28 children (M:F=11:17) with 32 SAVS lesions, with a mean age of 12.8±1.1 years at diagnosis. At presentation, SAVS were most highly concentrated in the cervical region (40.6%). Children had a median AL=2 and MC=2, with thoracolumbar AVS carrying the greatest disability. Among treated cases, complete obliteration was achieved in 48% of cases and median AL scores and MC grades both improved by one point. Systematic literature review identified 161 children (M:F=96:65) with 166 SAVS lesions with a mean age of 8.7±0.4 years. Among studies describing symptom chronicity, 37/51 (72.5%) of children presented acutely. At presentation, children had a median AL=4 and MC=3, with thoracolumbar AVS carrying the highest MC grades. After intervention, median AL and MC both improved by one point.

CONCLUSIONS

This study provides epidemiologic information on the location, onset, and presentation of the full spectrum of pediatric SAVS, highlighting the role of targeted treatment of high-risk features.

Understanding the pathogenesis of brain arteriovenous malformation: genetic variations, epigenetics, signaling pathways, and immune inflammation

Brain arteriovenous malformation (BAVM) is a rare but serious cerebrovascular disease whose pathogenesis has not been fully elucidated. Studies have found that epigenetic regulation, genetic variation and their signaling pathways, immune inflammation, may be the cause of BAVM the main reason. This review comprehensively analyzes the key pathways and inflammatory factors related to BAVMs, and explores their interplay with epigenetic regulation and genetics. Studies have found that epigenetic regulation such as DNA methylation, non-coding RNAs and m6A RNA modification can regulate endothelial cell proliferation, apoptosis, migration and damage repair of vascular malformations through different target gene pathways. Gene defects such as KRAS, ACVRL1 and EPHB4 lead to a disordered vascular environment, which may promote abnormal proliferation of blood vessels through ERK, NOTCH, mTOR, Wnt and other pathways. PDGF-B and PDGFR-β were responsible for the recruitment of vascular adventitial cells and smooth muscle cells in the extracellular matrix environment of blood vessels, and played an important role in the pathological process of BAVM. Recent single-cell sequencing data revealed the diversity of various cell types within BAVM, as well as the heterogeneous expression of vascular-associated antigens, while neutrophils, macrophages and cytokines such as IL-6, IL-1, TNF-α, and IL-17A in BAVM tissue were significantly increased. Currently, there are no specific drugs targeting BAVMs, and biomarkers for BAVM formation, bleeding, and recurrence are lacking clinically. Therefore, further studies on molecular biological mechanisms will help to gain insight into the pathogenesis of BAVM and develop potential therapeutic strategies.

Key biomarkers in cerebral arteriovenous malformations: Updated review

The formation of vascular networks consisting of arteries, capillaries, and veins is vital in embryogenesis. It is also crucial in adulthood for the formation of a functional vasculature. Cerebral arteriovenous malformations (CAVMs) are linked with a remarkable risk of intracerebral hemorrhage because arterial blood is directly shunted into the veins before the arterial blood pressure is dissipated. The underlying mechanisms responsible for arteriovenous malformation (AVM) growth, progression, and rupture are not fully known, yet the critical role of inflammation in AVM pathogenesis has been noted. The proinflammatory cytokines are upregulated in CAVM, which stimulates overexpression of cell adhesion molecules in endothelial cells (ECs), leading to improved leukocyte recruitment. It is well-known that metalloproteinase-9 secretion by leukocytes disrupts CAVM walls resulting in rupture. Moreover, inflammation alters the angioarchitecture of CAVMs by upregulating angiogenic factors impacting the apoptosis, migration, and proliferation of ECs. A better understanding of the molecular signature of CAVM might allow us to identify biomarkers predicting this complication, acting as a goal for further investigations that may be potentially targeted in gene therapy. The present review is focused on the numerous studies conducted on the molecular signature of CAVM and the associated hemorrhage. The association of numerous molecular signatures with a higher risk of CAVM rupture is shown through inducing proinflammatory mediators, as well as growth factors signaling, Ras-mitogen-activated protein kinase-extracellular signal-regulated kinase, and NOTCH pathways, which are accompanied by cellular level inflammation and endothelial alterations resulting in vascular wall instability. According to the studies, it is assumed that matrix metalloproteinase, interleukin-6, and vascular endothelial growth factor are the biomarkers most associated with CAVM and the rate of hemorrhage, as well as diagnostic methods, with respect to enhancing the patient-specific risk estimation and improving treatment choices.

VEGFR2 Expression Correlates with Postnatal Development of Brain Arteriovenous Malformations in a Mouse Model of Type I Hereditary Hemorrhagic Telangiectasia

Brain arteriovenous malformations (BAVMs) are a critical concern in hereditary hemorrhagic telangiectasia (HHT) patients, carrying the risk of life-threatening intracranial hemorrhage. While traditionally seen as congenital, the debate continues due to documented de novo cases. Our primary goal was to identify the precise postnatal window in which deletion of the HHT gene Endoglin (Eng) triggers BAVM development. We employed SclCreER(+);Eng2f/2f mice, enabling timed Eng gene deletion in endothelial cells via tamoxifen. Tamoxifen was given during four postnatal periods: P1-3, P8-10, P15-17, and P22-24. BAVM development was assessed at 2-3 months using latex dye perfusion. We examined the angiogenic activity by assessing vascular endothelial growth factor receptor 2 (VEGFR2) expression via Western blotting and Flk1-LacZ reporter mice. Longitudinal magnetic resonance angiography (MRA) was conducted up to 9 months. BAVMs emerged in 88% (P1-3), 86% (P8-10), and 55% (P15-17) of cases, with varying localization. Notably, the P22-24 group did not develop BAVMs but exhibited skin AVMs. VEGFR2 expression peaked in the initial 2 postnatal weeks, coinciding with BAVM onset. These findings support the "second hit" theory, highlighting the role of early postnatal angiogenesis in initiating BAVM development in HHT type I mice.

Localized conditional induction of brain arteriovenous malformations in a mouse model of hereditary hemorrhagic telangiectasia

BACKGROUND

Longitudinal mouse models of brain arteriovenous malformations (AVMs) are crucial for developing novel therapeutics and pathobiological mechanism discovery underlying brain AVM progression and rupture. The sustainability of existing mouse models is limited by ubiquitous Cre activation, which is associated with lethal hemorrhages resulting from AVM formation in visceral organs. To overcome this condition, we developed a novel experimental mouse model of hereditary hemorrhagic telangiectasia (HHT) with CreER-mediated specific, localized induction of brain AVMs.

METHODS

Hydroxytamoxifen (4-OHT) was stereotactically delivered into the striatum, parietal cortex, or cerebellum of R26CreER; Alk12f/2f (Alk1-iKO) littermates. Mice were evaluated for vascular malformations with latex dye perfusion and 3D time-of-flight magnetic resonance angiography (MRA). Immunofluorescence and Prussian blue staining were performed for vascular lesion characterization.

RESULTS

Our model produced two types of brain vascular malformations, including nidal AVMs (88%, 38/43) and arteriovenous fistulas (12%, 5/43), with an overall frequency of 73% (43/59). By performing stereotaxic injection of 4-OHT targeting different brain regions, Alk1-iKO mice developed vascular malformations in the striatum (73%, 22/30), in the parietal cortex (76%, 13/17), and in the cerebellum (67%, 8/12). Identical application of the stereotaxic injection protocol in reporter mice confirmed localized Cre activity near the injection site. The 4-week mortality was 3% (2/61). Seven mice were studied longitudinally for a mean (SD; range) duration of 7.2 (3; 2.3-9.5) months and demonstrated nidal stability on sequential MRA. The brain AVMs displayed microhemorrhages and diffuse immune cell invasion.

CONCLUSIONS

We present the first HHT mouse model of brain AVMs that produces localized AVMs in the brain. The mouse lesions closely resemble the human lesions for complex nidal angioarchitecture, arteriovenous shunts, microhemorrhages, and inflammation. The model's longitudinal robustness is a powerful discovery resource to advance our pathomechanistic understanding of brain AVMs and identify novel therapeutic targets.

Etiologies of Brain Arteriovenous Malformation Recurrence: A Focus on Pediatric Disease

Pediatric brain arteriovenous malformations are a major cause of morbidity and mortality, with the harmful effects of this disease compounded by the additional disability-years experienced by children with ruptured or other symptomatic arteriovenous malformations. In addition to the risks shared with their adult counterparts, pediatric patients frequently experience recurrence following radiographic cure, which presents an additional source of morbidity and mortality. Therefore, there is a need to synthesize potential mechanisms contributing to the elevated recurrence risk in the pediatric population and discuss how these translate to practical considerations for managing these patients.

The Role and Therapeutic Implications of Inflammation in the Pathogenesis of Brain Arteriovenous Malformations

Brain arteriovenous malformations (bAVMs) are focal vascular lesions composed of abnormal vascular channels without an intervening capillary network. As a result, high-pressure arterial blood shunts directly into the venous outflow system. These high-flow, low-resistance shunts are composed of dilated, tortuous, and fragile vessels, which are prone to rupture. BAVMs are a leading cause of hemorrhagic stroke in children and young adults. Current treatments for bAVMs are limited to surgery, embolization, and radiosurgery, although even these options are not viable for ~20% of AVM patients due to excessive risk. Critically, inflammation has been suggested to contribute to lesion progression. Here we summarize the current literature discussing the role of the immune system in bAVM pathogenesis and lesion progression, as well as the potential for targeting inflammation to prevent bAVM rupture and intracranial hemorrhage. We conclude by proposing that a dysfunctional endothelium, which harbors the somatic mutations that have been shown to give rise to sporadic bAVMs, may drive disease development and progression by altering the immune status of the brain.

Somatic variants of MAP3K3 are sufficient to cause cerebral and spinal cord cavernous malformations

Cerebral cavernous malformations (CCMs) and spinal cord cavernous malformations (SCCMs) are common vascular abnormalities of the CNS that can lead to seizure, haemorrhage and other neurological deficits. Approximately 85% of patients present with sporadic (versus congenital) CCMs. Somatic mutations in MAP3K3 and PIK3CA were recently reported in patients with sporadic CCM, yet it remains unknown whether MAP3K3 mutation is sufficient to induce CCMs. Here we analysed whole-exome sequencing data for patients with CCM and found that ∼40% of them have a single, specific MAP3K3 mutation [c.1323C>G (p.Ile441Met)] but not any other known mutations in CCM-related genes. We developed a mouse model of CCM with MAP3K3I441M uniquely expressed in the endothelium of the CNS. We detected pathological phenotypes similar to those found in patients with MAP3K3I441M. The combination of in vivo imaging and genetic labelling revealed that CCMs were initiated with endothelial expansion followed by disruption of the blood-brain barrier. Experiments with our MAP3K3I441M mouse model demonstrated that CCM can be alleviated by treatment with rapamycin, the mTOR inhibitor. CCM pathogenesis has usually been attributed to acquisition of two or three distinct genetic mutations involving the genes CCM1/2/3 and/or PIK3CA. However, our results demonstrate that a single genetic hit is sufficient to cause CCMs.

Comprehensive profiling of pathogenic germline large genomic rearrangements in a pan-cancer analysis

The presence of large genomic rearrangements (LGRs) has been heavily investigated in breast and ovarian cancer. However, correlations between LGRs and cancer types beyond these two have not been extensively profiled, likely due to the highly inefficient methods of detecting these types of alterations. This study utilized next-generation sequencing (NGS) to analyze and classify the germline LGR profile in 17 025 cancer patients across 22 cancer types. We characterized newly identified LGRs based on predicted pathogenicity and took a closer look at genes that acquire both germline and somatic mutations within our samples. The detection method for LGRs was validated using droplet digital polymerase chain reaction (ddPCR) assay of commonly investigated LGR genes. In total, 15 659 samples from across 22 cancer types were retained for analysis after filtering. We observed that, in our cohort, the cancer types with the highest proportion of germline LGRs were ovarian cancer (4.7%), renal cell carcinoma (2.5%), breast cancer (2%), glioma (1.8%) and thyroid carcinoma (1.8%). Annotation of detected germline variants revealed several genes-MSH2, FANCA and PMS2-that contain novel LGRs. We observed co-occurrences between germline LGRs in MSH2 and somatic single nucleotide variants/insertion and deletions (SNVs/InDels) in BRCA2, KTM2B, KDM5A, CHD8, and HNF1A. Furthermore, our analysis showed that samples with pathogenic and likely pathogenic germline LGRs tended to also have higher mutational burden, chromosomal instability, and microsatellite instability ratio compared to samples with pathogenic germline SNVs/InDels. In this study, we demonstrated the prevalence of pathogenic germline LGRs beyond breast and ovarian cancer. The profiles of these pathogenic or likely pathogenic alterations will fuel further investigations and highlight new understanding of LGRs across multiple cancer types.

Pericytes and vascular smooth muscle cells in central nervous system arteriovenous malformations

Previously considered passive support cells, mural cells-pericytes and vascular smooth muscle cells-have started to garner more attention in disease research, as more subclassifications, based on morphology, gene expression, and function, have been discovered. Central nervous system (CNS) arteriovenous malformations (AVMs) represent a neurovascular disorder in which mural cells have been shown to be affected, both in animal models and in human patients. To study consequences to mural cells in the context of AVMs, various animal models have been developed to mimic and predict human AVM pathologies. A key takeaway from recently published work is that AVMs and mural cells are heterogeneous in their molecular, cellular, and functional characteristics. In this review, we summarize the observed perturbations to mural cells in human CNS AVM samples and CNS AVM animal models, and we discuss various potential mechanisms relating mural cell pathologies to AVMs.

KRAS mutation-induced EndMT of brain arteriovenous malformation is mediated through the TGF-β/BMP-SMAD4 pathway

OBJECTIVE

Somatic KRAS mutations have been identified in the majority of brain arteriovenous malformations (bAVMs), and subsequent in vivo experiments have confirmed that KRAS mutation in endothelial cells (ECs) causes AVMs in mouse and zebrafish models. Our previous study demonstrated that the KRASG12D mutant independently induced the endothelial-mesenchymal transition (EndMT), which was reversed by treatment with the lipid-lowering drug lovastatin. However, the underlying mechanisms of action were unclear.

METHODS

We used human umbilical vein ECs (HUVECs) overexpressing the KRASG12D mutant for Western blotting, quantitative real-time PCR, and immunofluorescence and wound healing assays to evaluate the EndMT and determine the activation of downstream pathways. Knockdown of SMAD4 by RNA interference was performed to explore the role of SMAD4 in regulating the EndMT. BAVM ECs expressing the KRASG12D mutant were obtained to verify the SMAD4 function. Finally, we performed a coimmunoprecipitation assay to probe the mechanism by which lovastatin affects SMAD4.

RESULTS

HUVECs infected with KRASG12D adenovirus underwent the EndMT. Transforming growth factor beta (TGF-β) and bone morphogenetic protein (BMP) signalling pathways were activated in the KRASG12D-mutant HUVECs and ECs in bAVM tissue. Knocking down SMAD4 expression in both KRASG12D-mutant HUVECs and ECs in bAVM tissues inhibited the EndMT. Lovastatin attenuated the EndMT by downregulating p-SMAD2/3, p-SMAD1/5 and acetylated SMAD4 expression in KRASG12D-mutant HUVECs.

CONCLUSIONS

Our findings suggest that the KRASG12D mutant induces the EndMT by activating the ERK-TGF-β/BMP-SMAD4 signalling pathway and that lovastatin inhibits the EndMT by suppressing TGF-β/BMP pathway activation and SMAD4 acetylation.

Ruptured bilateral brain arteriovenous malformations in a young woman with early pregnancy: a case report

BACKGROUND

Brain arteriovenous malformations (AVMs) are rare congenital developmental vascular lesions, and often presents with symptoms upon rupture. The controversy exists as to whether pregnancy confers an increased risk of intracranial hemorrhage. The diagnosis of brain AVMs, in the absence of brain imaging, is challenging in resource-limited settings, particularly in sub-Saharan Africa.

CASE PRESENTATION

A 22-year old black African woman, primigravida at 14 weeks of gestation, presented with a history of persistent throbbing headache which was treated at primary health care facilities with analgesics and anti-migraine medications without relief. She later developed severe headache 2 weeks prior to admission and one-day history of serial partial generalized tonic-clonic seizures which were followed by post-ictal confusion and persistent right upper limb weakness. Initial evaluation revealed her to be pregnant and she later underwent a brain magnetic resonance angiography (MRA) at a university teaching hospital which revealed bleeding bilateral parietal AMVs with intracerebral haematoma and associated perilesional vasogenic oedema. The patient was managed conservatively using antifibrinolytic drugs and prophylactic anti-seizure drugs. Seven months later, she underwent a control brain MRA which revealed resolution of intracranial haematoma and associated vasogenic oedema and had her seizures well controlled. The headache had subsided and the pregnancy was allowed to continue to term under close obstetric and neurological observation. On follow up visits she reported episodes of nasal bleeding which upon ENT examination revealed nasal AVMs, suggesting the diagnosis of hereditary hemorrhagic telangiectasia (HHT).

CONCLUSION

AVMs are rare but should prompt suspicion in young patients with atypical Central Nervous System (CNS) manifestations without evident underlying causes.

Nitric oxide synthase and reduced arterial tone contribute to arteriovenous malformation

Mechanisms underlying arteriovenous malformations (AVMs) are poorly understood. Using mice with endothelial cell (EC) expression of constitutively active Notch4 (Notch4*EC), we show decreased arteriolar tone in vivo during brain AVM initiation. Reduced vascular tone is a primary effect of Notch4*EC, as isolated pial arteries from asymptomatic mice exhibited reduced pressure-induced arterial tone ex vivo. The nitric oxide (NO) synthase (NOS) inhibitor NG-nitro-l-arginine (L-NNA) corrected vascular tone defects in both assays. L-NNA treatment or endothelial NOS (eNOS) gene deletion, either globally or specifically in ECs, attenuated AVM initiation, assessed by decreased AVM diameter and delayed time to moribund. Administering nitroxide antioxidant 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl also attenuated AVM initiation. Increased NOS-dependent production of hydrogen peroxide, but not NO, superoxide, or peroxynitrite was detected in isolated Notch4*EC brain vessels during AVM initiation. Our data suggest that eNOS is involved in Notch4*EC-mediated AVM formation by up-regulating hydrogen peroxide and reducing vascular tone, thereby permitting AVM initiation and progression.

Recurrence of brain arteriovenous malformations in pediatric patients: a long-term follow-up study

BACKGROUND

Previously thought to be congenital, AVMs have shown evidence of de-novo formation and continued growth, thus shifting thoughts on their pathophysiology. Pediatric AVM patients have been reported to be more prone to develop AVM recurrence after a seemingly complete cure. Therefore, we assessed the risk of AVM treated in childhood to recur in adulthood after a long-term follow-up in our own cohort.

METHODS

Control DS-angiography was arranged during 2021-2022 as part of a new protocol for all AVM patients who were under 21 years of age at the time of their treatment and in whom the treatment had occurred at least five years earlier. Angiography was offered only to patients under 50 years of age at the time of the new protocol. The complete eradication of AVM after the primary treatment had been originally confirmed with DSA in every patient.

RESULTS

A total of 42 patients participated in the late DSA control, and 41 of them were included in this analysis after excluding the patient diagnosed with HHT. The median age at the time of admission for AVM treatment was 14.6 (IQR 12-19, range 7-21 years) years. The median age at the time of the late follow-up DSA was 33.8 years (IQR 29.8-38.6, range 19.4-47.9 years). Two recurrent sporadic AVMs and one recurrent AVM in a patient with hereditary hemorrhagic telangiectasia (HHT) were detected. The recurrence rate was 4.9% for sporadic AVMs and 7.1% if HHT-AVM was included. All the recurrent AVMs had originally bled and been treated microsurgically. The patients with sporadic AVM recurrence had been smoking their whole adult lives.

CONCLUSIONS

Pediatric and adolescent patients are prone to develop recurrent AVMs, even after complete AVM obliteration verified by angiography. Therefore, imaging follow-up is recommended.

Treatment of Challenging Extracranial Arteriovenous Malformations: A Single-Center Experience and Literature Review

ABSTRACT

Extracranial arteriovenous malformation (AVM) is a high-flow congenital vascular malformation, where direct communication between the arteries and veins impedes perfusion of capillary beds and causes disfigurement of the affected tissue. Surgery and endovascular therapy are currently the main treatment for extracranial AVMs. Nevertheless, management of complex cases is sometimes challenging because of severe complications such as refractory ulceration, life-threatening bleeding, and even cardiac insufficiency. Here, we reviewed the development and potential treatment for extracranial AVMs and shared our single-center experiences of diagnosis and treatment of this challenging disease.

RAS pathway: The new frontier of brain mosaicism in epilepsy

As cells divide during development, errors in DNA replication and repair lead to somatic mosaicism - a phenomenon in which different cell lineages harbor unique constellations of genetic variants. Over the past decade, somatic variants that disrupt mTOR signaling, protein glycosylation, and other functions during brain development have been linked to cortical malformations and focal epilepsy. More recently, emerging evidence points to a role for Ras pathway mosaicism in epilepsy. The Ras family of proteins is a critical driver of MAPK signaling. Disruption of the Ras pathway is most known for its association with tumorigenesis; however, developmental disorders known as RASopathies commonly have a neurological component that sometimes includes epilepsy, offering evidence for Ras involvement in brain development and epileptogenesis. Brain somatic variants affecting the Ras pathway (e.g., KRAS, PTPN11, BRAF) are now strongly associated with focal epilepsy through genotype-phenotype association studies as well as mechanistic evidence. This review summarizes the Ras pathway and its involvement in epilepsy and neurodevelopmental disorders, focusing on new evidence regarding Ras pathway mosaicism and the potential future clinical implications.

Shaping the brain vasculature in development and disease in the single-cell era

The CNS critically relies on the formation and proper function of its vasculature during development, adult homeostasis and disease. Angiogenesis - the formation of new blood vessels - is highly active during brain development, enters almost complete quiescence in the healthy adult brain and is reactivated in vascular-dependent brain pathologies such as brain vascular malformations and brain tumours. Despite major advances in the understanding of the cellular and molecular mechanisms driving angiogenesis in peripheral tissues, developmental signalling pathways orchestrating angiogenic processes in the healthy and the diseased CNS remain incompletely understood. Molecular signalling pathways of the 'neurovascular link' defining common mechanisms of nerve and vessel wiring have emerged as crucial regulators of peripheral vascular growth, but their relevance for angiogenesis in brain development and disease remains largely unexplored. Here we review the current knowledge of general and CNS-specific mechanisms of angiogenesis during brain development and in brain vascular malformations and brain tumours, including how key molecular signalling pathways are reactivated in vascular-dependent diseases. We also discuss how these topics can be studied in the single-cell multi-omics era.

High-depth next-generation sequencing panel testing in the evaluation of arteriovenous malformations

Arteriovenous malformations (AVMs) are vascular lesions in which an overgrowth of blood vessels of varying sizes develops with one or more direct connections between the arterial and venous circulation. We performed a retrospective review of a cohort of 54 patients with AVMs referred to our clinical genomic laboratory for high-depth next-generation sequencing (NGS) panel of Disorders of Somatic Mosaicism (DoSM). Thirty-seven of 54 patients were female (68.5%). Among the 54 cases, 37 (68.5%) cases had pathogenic and/or likely pathogenic (P/LP) variants identified, two cases (3.7%) had variants of uncertain clinical significance, and the remaining 15 cases (27.8%) had negative results. MAP2K1 variants were found in 12 cases, followed by eight cases with KRAS variants and seven with TEK variants, and the remainder being identified in several other genes on the panel. Among the 37 positive cases, 32 cases had somatic alterations only; the remaining five cases had at least one germline P/LP variant, including four cases with PTEN and one with RASA1. Of note, two cases had the unexpected co-existence of two P/LP variants. In summary, this study illustrated the molecular diagnostic yield (68.5%) of this cohort of patients with a clinical indication of AVMs by our high-depth DoSM NGS panel.

Genetics of brain arteriovenous malformations and cerebral cavernous malformations

Cerebrovascular malformations comprise abnormal development of cerebral vasculature. They can result in hemorrhagic stroke due to rupture of lesions as well as seizures and neurological defects. The most common forms of cerebrovascular malformations are brain arteriovenous malformations (bAVMs) and cerebral cavernous malformations (CCMs). They occur in both sporadic and inherited forms. Rapidly evolving molecular genetic methodologies have helped to identify causative or associated genes involved in genesis of bAVMs and CCMs. In this review, we highlight the current knowledge regarding the genetic basis of these malformations.

Increasing precision in the management of pediatric neurosurgical cerebrovascular diseases with molecular genetics

Recent next-generation DNA and RNA sequencing studies of congenital and pediatric cerebrovascular anomalies such as moyamoya disease, arteriovenous malformations, vein of Galen malformations, and cavernous malformations have shed new insight into the genetic regulation of human cerebrovascular development by implicating multiple novel disease genes and signaling pathways in the pathogenesis of these disorders. These diseases are now beginning to be categorized by molecular disruptions in canonical signaling pathways that impact the differentiation and proliferation of specific venous, capillary, or arterial cells during the hierarchical development of the cerebrovascular system. Here, the authors discuss how the continued study of these and other congenital cerebrovascular conditions has the potential to replace the current antiquated, anatomically based disease classification systems with a molecular taxonomy that has the potential to increase precision in genetic counseling, prognostication, and neurosurgical and endovascular treatment stratification. Importantly, the authors also discuss how molecular genetic data are already informing clinical trials and catalyzing the development of targeted therapies for these conditions historically considered as exclusively neurosurgical lesions.

New approaches for brain arteriovenous malformations-related epilepsy

BACKGROUND

The purpose of this review is to present the current literature and to highlight the most recent findings in brain arteriovenous malformations (bAVM)-related epilepsy research.

METHODS

We searched Medline, PubMed, Biblioinserm, Cochrane Central to study the latest research reports about the different factors that could be responsible for the genesis of bAVM-related epilepsy. We analyzed if epileptogenesis has any characteristics traits and its relation with the vascular malformation. The results of different treatments on epilepsy were considered. Typical errors that may lead towards incorrect or worse management of the seizures for these patients were also examined.

RESULTS

The development of bAVM results from multifactorial etiologies and bAVM-related epileptogenesis is likely specific for this pathology. Different types of evidence demonstrate a bidirectional relationship between bAVM and epilepsy. Currently, there is not enough published data to determine what may be the right management for these patients.

CONCLUSIONS

A better understanding of epileptogenesis in conjunction with knowledge of the complex alterations of structures and functions following bAVM-related seizures is necessary. Identification of biomarkers that can identify subgroups most likely to benefit from a specific intervention are needed to help guide clinical management. A new concept for the treatment of epilepsy related to an unruptured bAVM that cannot be treated invasively is proposed as well as new therapeutic perspectives. The next necessary step will be to propose additional algorithms to improve the development of future trials.