Genetic Basis and Therapies for Vascular Anomalies

Assessment of gene-disease associations and recommendations for genetic testing for somatic variants in vascular anomalies by VASCERN-VASCA

BACKGROUND

Vascular anomalies caused by somatic (postzygotic) variants are clinically and genetically heterogeneous diseases with overlapping or distinct entities. The genetic knowledge in this field is rapidly growing, and genetic testing is now part of the diagnostic workup alongside the clinical, radiological and histopathological data. Nonetheless, access to genetic testing is still limited, and there is significant heterogeneity across the approaches used by the diagnostic laboratories, with direct consequences on test sensitivity and accuracy. The clinical utility of genetic testing is expected to increase progressively with improved theragnostics, which will be based on information about the efficacy and safety of the emerging drugs and future molecules. The aim of this study was to make recommendations for optimising and guiding the diagnostic genetic testing for somatic variants in patients with vascular malformations.

RESULTS

Physicians and lab specialists from 11 multidisciplinary European centres for vascular anomalies reviewed the genes identified to date as being involved in non-hereditary vascular malformations, evaluated gene-disease associations, and made recommendations about the technical aspects for identification of low-level mosaicism and variant interpretation. A core list of 24 genes were selected based on the current practices in the participating laboratories, the ISSVA classification and the literature. In total 45 gene-phenotype associations were evaluated: 16 were considered definitive, 16 strong, 3 moderate, 7 limited and 3 with no evidence.

CONCLUSIONS

This work provides a detailed evidence-based view of the gene-disease associations in the field of vascular malformations caused by somatic variants. Knowing both the gene-phenotype relationships and the strength of the associations greatly help laboratories in data interpretation and eventually in the clinical diagnosis. This study reflects the state of knowledge as of mid-2023 and will be regularly updated on the VASCERN-VASCA website (VASCERN-VASCA, https://vascern.eu/groupe/vascular-anomalies/ ).

Complex lymphatic anomalies: Molecular landscape and medical management

The lymphatic system is one of the most essential and complex systems in the human body. Disorders that affect the development or function of the lymphatic system can lead to multi-system complications and life-long morbidity. The past two decades have seen remarkable progress in our knowledge of the basic biology and function of the lymphatic system, the molecular regulators of lymphatic development, and description of disorders associated with disrupted lymphangiogensis. In this chapter we will touch on the clinical features of complex lymphatic anomalies, new molecular knowledge of the drivers of these disorders, and novel developmental therapeutics for lymphatic disease.

Shear stress and pathophysiological PI3K involvement in vascular malformations

Molecular characterization of vascular anomalies has revealed that affected endothelial cells (ECs) harbor gain-of-function (GOF) mutations in the gene encoding the catalytic α subunit of PI3Kα (PIK3CA). These PIK3CA mutations are known to cause solid cancers when occurring in other tissues. PIK3CA-related vascular anomalies, or "PIKopathies," range from simple, i.e., restricted to a particular form of malformation, to complex, i.e., presenting with a range of hyperplasia phenotypes, including the PIK3CA-related overgrowth spectrum. Interestingly, development of PIKopathies is affected by fluid shear stress (FSS), a physiological stimulus caused by blood or lymph flow. These findings implicate PI3K in mediating physiological EC responses to FSS conditions characteristic of lymphatic and capillary vessel beds. Consistent with this hypothesis, increased PI3K signaling also contributes to cerebral cavernous malformations, a vascular disorder that affects low-perfused brain venous capillaries. Because the GOF activity of PI3K and its signaling partners are excellent drug targets, understanding PIK3CA's role in the development of vascular anomalies may inform therapeutic strategies to normalize EC responses in the diseased state. This Review focuses on PIK3CA's role in mediating EC responses to FSS and discusses current understanding of PIK3CA dysregulation in a range of vascular anomalies that particularly affect low-perfused regions of the vasculature. We also discuss recent surprising findings linking increased PI3K signaling to fast-flow arteriovenous malformations in hereditary hemorrhagic telangiectasias.

Ethanol embolization of arteriovenous malformations in the buttock: ten-year experiences in diagnoses and treatment options

BACKGROUND

Clinically, arteriovenous malformations in the buttocks (bAVMs) are extremely rare. Our study aimed to evaluate the efficacy and safety of ethanol embolotherapy in managing bAVMs.

RESULTS

A total of 32 patients with bAVMs (14 females and 18 males) from 2012 to 2021 were included in this study. All patients underwent complete clinical and imaging examinations. Further, the AVMs lesions were analyzed according to Schöbinger staging and Yakes classification. Each patient had undergone a multistage ethanol embolization. The amelioration of clinical symptoms and devascularization on angiography were evaluated at regular follow-ups. In the present cohort, the 11-20 age group had the most patients (15/32; 46.88%). A total of 124 embolization procedures were performed (average 3.88 procedures per patient), and the average dose of absolute ethanol was 18.96 mL per procedure. Thirteen patients with dominant draining veins underwent additional coil deployment before ethanol embolization (13/32; 40.63%). During follow-ups, clinical improvement was found in 23 of 27 who presented with a pulsating mass (85.19%), 17 of 20 with abnormal local skin temperature (85%), 5 of 6 with bleeding (83.33%), and 5 of 5 patients treated for pain (100%). More than 75% angiographic devascularization was achieved in 18 patients (18/32; 56.25%). Finally, 12 out of 13 patients (92.31%) reduced from Schöbinger Stage III to a lower grade, and ten patients exhibited a complete response (10/32; 31.23%). There was a single serious complication of local necrosis, while neither paranesthesia nor infection was observed postoperatively.

CONCLUSIONS

Ethanol embolization assisted with coils can treat bAVMs effectively and safely. The Yakes classification contributed to the optimal ethanol embolotherapy of bAVMs.

Management of Neonatal Hepatic Hemangiomas: A Single-Center Experience Focused on Challenging Cases

Background: Management of hepatic hemangioma (HH) in infancy ranges from close monitoring to surgical resection. We analyzed the clinical characteristics and outcomes of HH according to its treatment options, with particular focus on challenging cases. Methods: Data of patients diagnosed with HHs in their first year of life and followed up for at least 1 year were retrospectively reviewed and divided into treatment and observation groups. Serial imaging results, serum alpha-fetoprotein (AFP) levels, medications, and clinical outcomes were compared. The detailed clinical progress in the treatment group was reviewed separately. Results: A total of 87 patients (75 in the observation group and 12 in the treatment group) were included. The median HH size at the initial diagnosis and the maximum size were significantly larger in the treatment group than the observation group (2.2 [0.5-10.3] cm vs. 1.0 [0.4-4.0] cm and 2.1 [0.7-13.2] vs. 1.1 [0.4-4.0], respectively; all p < 0.05]. The median initial and last serum AFP levels were significantly higher in the treatment group than in the observation group (76,818.7 vs. 627.2 and 98.4 vs. 8.7, respectively; all p < 0.05). Serum AFP levels in both groups rapidly declined during the first 3 months of life and were almost undetectable after 6 months. Among the challenging cases, a large (14 × 10 × 6.5 cm sized) focal HH was successfully treated using stepwise medical-to-surgical treatment. Conclusions: Patients with large HH and mild symptoms can be treated using stepwise pharmacotherapy. More aggressive surgical treatment of tumors unresponsive to initial pharmacotherapy may help shorten the treatment period and improve outcomes.

Genome-wide profiling of angiogenic cis-regulatory elements unravels cis-regulatory SNPs for vascular abnormality

Angiogenesis is extensively involved in embryonic development and requires complex regulation networks, whose defects can cause a variety of vascular abnormalities. Cis-regulatory elements control gene expression at all developmental stages, but they have not been studied or profiled in angiogenesis yet. In this study, we exploited public DNase-seq and RNA-seq datasets from a VEGFA-stimulated in vitro angiogenic model, and carried out an integrated analysis of the transcriptome and chromatin accessibility across the entire process. Totally, we generated a bank of 47,125 angiogenic cis-regulatory elements with promoter (marker by H3K4me3) and/or enhancer (marker by H3K27ac) activities. Motif enrichment analysis revealed that these angiogenic cis-regulatory elements interacted preferentially with ETS family TFs. With this tool, we performed an association study using our WES data of TAPVC and identified rs199530718 as a cis-regulatory SNP associated with disease risk. Altogether, this study generated a genome-wide bank of angiogenic cis-regulatory elements and illustrated its utility in identifying novel cis-regulatory SNPs for TAPVC, expanding new horizons of angiogenesis as well as vascular abnormality genetics.

Extracranial Vascular Anomalies Driven by RAS/MAPK Variants: Spectrum and Genotype-Phenotype Correlations

BACKGROUND

We aimed to correlate alterations in the rat sarcoma virus (RAS)/mitogen-activated protein kinase pathway in vascular anomalies to the clinical phenotype for improved patient and treatment stratification.

METHODS AND RESULTS

This retrospective multicenter cohort study included 29 patients with extracranial vascular anomalies containing mosaic pathogenic variants (PVs) in genes of the RAS/mitogen-activated protein kinase pathway. Tissue samples were collected during invasive treatment or clinically indicated biopsies. PVs were detected by the targeted sequencing of panels of genes known to be associated with vascular anomalies, performed using DNA from affected tissue. Subgroup analyses were performed according to the affected genes with regard to phenotypic characteristics in a descriptive manner. Twenty-five vascular malformations, 3 vascular tumors, and 1 patient with both a vascular malformation and vascular tumor presented the following distribution of PVs in genes: Kirsten rat sarcoma viral oncogene (n=10), neuroblastoma ras viral oncogene homolog (n=1), Harvey rat sarcoma viral oncogene homolog (n=5), V-Raf murine sarcoma viral oncogene homolog B (n=8), and mitogen-activated protein kinase kinase 1 (n=5). Patients with RAS PVs had advanced disease stages according to the Schobinger classification (stage 3-4: RAS, 9/13 versus non-RAS, 3/11) and more frequent progression after treatment (RAS, 10/13 versus non-RAS, 2/11). Lesions with Kirsten rat sarcoma viral oncogene PVs infiltrated more tissue layers compared with the other PVs including other RAS PVs (multiple tissue layers: Kirsten rat sarcoma viral oncogene, 8/10 versus other PVs, 6/19).

CONCLUSIONS

This comparison of patients with various PVs in genes of the RAS/MAPK pathway provides potential associations with certain morphological and clinical phenotypes. RAS variants were associated with more aggressive phenotypes, generating preliminary data and hypothesis for future larger studies.

Capillary malformations

Capillary malformation (CM), or port wine birthmark, is a cutaneous congenital vascular anomaly that occurs in 0.1%-2% of newborns. Patients with a CM localized on the forehead have an increased risk of developing a neurocutaneous disorder called encephalotrigeminal angiomatosis or Sturge-Weber syndrome (SWS), with complications including seizure, developmental delay, glaucoma, and vision loss. In 2013, a groundbreaking study revealed causative activating somatic mutations in the gene (GNAQ) encoding guanine nucleotide-binding protein Q subunit α (Gαq) in CM and SWS patient tissues. In this Review, we discuss the disease phenotype, the causative GNAQ mutations, and their cellular origin. We also present the endothelial Gαq-related signaling pathways, the current animal models to study CM and its complications, and future options for therapeutic treatment. Further work remains to fully elucidate the cellular and molecular mechanisms underlying the formation and maintenance of the abnormal vessels.

Infantile hemangioma: the common and enigmatic vascular tumor

Infantile hemangioma (IH) is a benign vascular tumor that occurs in 5% of newborns. The tumor follows a life cycle of rapid proliferation in infancy, followed by slow involution in childhood. This unique life cycle has attracted the interest of basic and clinical scientists alike as a paradigm for vasculogenesis, angiogenesis, and vascular regression. Unanswered questions persist about the genetic and molecular drivers of the proliferating and involuting phases. The beta blocker propranolol usually accelerates regression of problematic IHs, yet its mechanism of action on vascular proliferation and differentiation is unclear. Some IHs fail to respond to beta blockers and regrow after discontinuation. Side effects occur and long-term sequelae of propranolol treatment are unknown. This poses clinical challenges and raises novel questions about the mechanisms of vascular overgrowth in IH.

Coexistence of kaposiform hemangioendothelioma and capillary malformation: More than a coincidence? Two case reports

The coexistence of kaposiform hemangioendothelioma (KHE) and capillary malformation (CM) is quite rare, and few relevant studies can be found to confirm whether this phenomenon is accidental. We diagnosed and treated two such patients, revealing interesting phenomena associated with the development of vascular diseases. These cases offer the possibility that the coexistence of KHE and CM is not accidental and open up a new field of research related to pediatric vascular tumors and vascular malformations. Personalization and precision are required in the diagnosis and treatment of such patients, and the present findings provide a reliable theoretical and practical basis for further research on the pathogenesis and therapy of patients with multiple vascular diseases.

Eph-ephrin signaling couples endothelial cell sorting and arterial specification

Cell segregation allows the compartmentalization of cells with similar fates during morphogenesis, which can be enhanced by cell fate plasticity in response to local molecular and biomechanical cues. Endothelial tip cells in the growing retina, which lead vessel sprouts, give rise to arterial endothelial cells and thereby mediate arterial growth. Here, we have combined cell type-specific and inducible mouse genetics, flow experiments in vitro, single-cell RNA sequencing and biochemistry to show that the balance between ephrin-B2 and its receptor EphB4 is critical for arterial specification, cell sorting and arteriovenous patterning. At the molecular level, elevated ephrin-B2 function after loss of EphB4 enhances signaling responses by the Notch pathway, VEGF and the transcription factor Dach1, which is influenced by endothelial shear stress. Our findings reveal how Eph-ephrin interactions integrate cell segregation and arteriovenous specification in the vasculature, which has potential relevance for human vascular malformations caused by EPHB4 mutations.

Infantile Hemangiomas and Vascular Anomalies

Vascular anomalies represent a diverse group of disorders of abnormal vascular development or proliferation. Vascular anomalies are classified as vascular tumors and vascular malformations. Significant advances have been made in the understanding of the pathogenesis, natural history, and genetics of vascular anomalies, allowing for improvements in management including targeted molecular therapies. Infantile hemangiomas are the most common vascular tumor of childhood and follow a distinct natural history of proliferation and involution. Although benign, infantile hemangiomas can be associated with important complications. The use of beta-blockers has revolutionized the management of infantile hemangiomas. Other vascular tumors include pyogenic granulomas, congenital hemangiomas, and kaposiform hemangioendotheliomas, among others. Vascular malformations are categorized based on the type of involved vessel, including capillary malformations, venous malformations, lymphatic malformations, arteriovenous malformations, and mixed vascular malformations. Expert multidisciplinary management of vascular anomalies is critical to optimize outcomes in these patients. [Pediatr Ann. 2024;53(4):e129-e137.].

Bisphenols and brominated bisphenols induced endothelial dysfunction via its disruption of endothelial nitric oxide synthase

Emerging literatures have concentrated on the association between cardiovascular diseases risk of typical endocrine disruptor bisphenols, which also put forward the further studies need respect to the potential mechanism. Herein, we investigated the endothelial dysfunction effects of bisphenols and brominated bisphenols involved in aortic pathological structure, endothelial nitric oxide synthase (eNOS) protein phosphorylation, synthase activity and nitric oxide (NO) production in human umbilical vein endothelial cells (HUVECs) and C57BL/6 mice. Bisphenol A (BPA) and bisphenol S (BPS) increased NO production by 85.7% and 68.8% at 10-6 M level in vitro and 74.3%, 41.5% in vivo, respectively, while tetrabromobisphenol S (TBBPS) significantly inhibited NO by 55.7% at 10-6 M in vitro and 28.9% in vivo at dose of 20 mg/kg BW/d. Aortic transcriptome profiling revealed that the process of 'regulation of NO mediated signal transduction' was commonly induced. The mRNA and protein expression of phosphorylated eNOS at Ser1177 were promoted by BPA and BPS but decreased by TBBPA and TBBPS in HUVECs. Phosphorylation and enzymatic activity of eNOS were significantly increased by 43.4% and 13.8% with the treatment of BPA and BPS at 10-7 M, but decreased by 16.9% after exposure to TBBPS at 10-6 M in vitro. Moreover, only TBBPS was observed to increase aorta thickness significantly in mice and induce endothelial dysfunction. Our work suggests that bisphenols and brominated bisphenols may exert adverse outcome on vascular health differently in vitro and in vivo, and emphasizes areas of public health concern similar endocrine disruptors vulnerable on the vascular endothelial function.

Defining the Functional Influence of Endothelial Cell-Expressed Oncogenic Activating Mutations on Vascular Morphogenesis and Capillary Assembly

This study sought to define key molecules and signals controlling major steps in vascular morphogenesis, and how these signals regulate pericyte recruitment and pericyte-induced basement membrane deposition. The morphogenic impact of endothelial cell (EC) expression of activating mutants of Kirsten rat sarcoma virus (kRas), mitogen-activated protein kinase 1 (Mek1), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), Akt serine/threonine kinase 1 (Akt1), Ras homolog enriched in brain (Rheb) Janus kinase 2 (Jak2), or signal transducer and activator of transcription 3 (Stat3) expression versus controls was evaluated, along with EC signaling events, pharmacologic inhibitor assays, and siRNA suppression experiments. Primary stimulators of EC lumen formation included kRas, Akt1, and Mek1, whereas PIK3CA and Akt1 stimulated a specialized type of cystic lumen formation. In contrast, the key drivers of EC sprouting behavior were Jak2, Stat3, Mek1, PIK3CA, and mammalian target of rapamycin (mTor). These conclusions are further supported by pharmacologic inhibitor and siRNA suppression experiments. EC expression of active Akt1, kRas, and PIK3CA led to markedly dysregulated lumen formation coupled to strongly inhibited pericyte recruitment and basement membrane deposition. For example, activated Akt1 expression in ECs excessively stimulated lumen formation, decreased EC sprouting behavior, and showed minimal pericyte recruitment with reduced mRNA expression of platelet-derived growth factor-BB, platelet-derived growth factor-DD, and endothelin-1, critical EC-derived factors known to stimulate pericyte invasion. The study identified key signals controlling fundamental steps in capillary morphogenesis and maturation and provided mechanistic details on why EC activating mutations induced a capillary deficiency state with abnormal lumens, impaired pericyte recruitment, and basement deposition: predisposing stimuli for the development of vascular malformations.

Lymphatic malformations: mechanistic insights and evolving therapeutic frontiers

The lymphatic vascular system is gaining recognition for its multifaceted role and broad pathological significance. Once perceived as a mere conduit for interstitial fluid and immune cell transport, recent research has unveiled its active involvement in critical physiological processes and common diseases, including inflammation, autoimmune diseases, and atherosclerosis. Consequently, abnormal development or functionality of lymphatic vessels can result in serious health complications. Here, we discuss lymphatic malformations (LMs), which are localized lesions that manifest as fluid-filled cysts or extensive infiltrative lymphatic vessel overgrowth, often associated with debilitating, even life-threatening, consequences. Genetic causes of LMs have been uncovered, and several promising drug-based therapies are currently under investigation and will be discussed.

Direct oral anticoagulants and venous malformations: literature review and retrospective study of 29 patients

Background

Venous malformations (VMs) are commonly associated with localized intravascular coagulopathy leading to elevated D-dimer and risks of hemorrhagic and thromboembolic events, particularly in extensive lesions. While low-molecular-weight heparin (LMWH) has been effective in managing coagulopathy and pain, direct oral anticoagulants (DOACs) emerge as a promising alternative.

Objectives

This study aims to evaluate the efficacy and safety of DOACs in treating VMs associated with localized intravascular coagulopathy, offering a comparative perspective to LMWH.

Methods

A retrospective study was conducted on 29 patients with VMs and secondary localized intravascular coagulopathy treated with DOACs between 2013 and 2023 in a single tertiary center specialized in vascular anomalies. Data were collected from February 24, 2023, to September 1, 2023.

Results

Patients' median age was 40 years (range, 22-76 years), with a female predominance of 66%. Descriptive statistical analysis showed that 85% of patients experienced pain improvement, and 86% showed a reduction in D-dimer by at least 25%, with a mean reduction of 57% (SD, ±32%; IQR, [38-81%]). Additionally, 37% of patients reported a bleeding event, mostly minor.

Conclusion

The study findings suggests that DOACs may serve as an alternative to LMWH for patients with VMs associated with pain management and reduced D-dimer, alongside a low observed risk of major bleeding. Tailored dosing considering the location of the malformation, bleeding and thrombotic tendencies, and laboratory abnormalities is recommended. Future studies with larger cohorts and extended follow-up are necessary for more conclusive evidence on DOACs' role in this patient population.

Comprehensive phenotypic and genomic characterization of venous malformations

Venous malformations (VMs) are the most common vascular malformations. TEK and PIK3CA are the causal genes of VMs, and may be involved in the PI3K/AKT pathway. However, the downstream mechanisms underlying the TEK or PIK3CA mutations in VMs are not completely understood. This study aimed to identify a possible association between genetic mutations and clinicopathological features. A retrospective clinical, pathological, and genetic study of 114 patients with VMs was performed. TEK, PIK3CA, and combined TEK/PIK3CA mutations were identified in 49 (43%), 13 (11.4%), and 2 (1.75%) patients, respectively. TEK-mutant VMs more commonly occurred in younger patients than TEK and PIK3CA mutation-negative VMs (other-mutant VMs), and showed more frequent skin involvement and no lymphocytic aggregates. No significant differences were observed in sex, location of occurrence, malformed vessel size, vessel density, or thickness of the vascular smooth muscle among the VM genotypes. Immunohistochemical analysis revealed that the expression levels of phosphorylated AKT (p-AKT) were higher in the TEK-mutant VMs than those in PIK3CA-mutant and other-mutant VMs. The expression levels of p-mTOR and its downstream effectors were higher in all the VM genotypes than those in normal vessels. Spatial transcriptomics revealed that the genes involved in "blood vessel development", "positive regulation of cell migration", and "extracellular matrix organization" were up-regulated in a TEK-mutant VM. Significant genotype-phenotype correlations in clinical and pathological features were observed among the VM genotypes, indicating gene-specific effects. Detailed analysis of gene-specific effects in VMs may offer insights into the underlying molecular pathways and implications for targeted therapies.

Somatic Loss-of-Function PIK3R1 and Activating Non-hotspot PIK3CA Mutations Associated with Capillary Malformation with Dilated Veins (CMDV)

Common capillary malformations are red vascular skin lesions, most commonly associated with somatic activating GNAQ or GNA11 mutations. We focused on capillary malformations lacking such a mutation to identify previously unreported genetic causes. We used targeted next-generation sequencing on 82 lesions. Bioinformatic analysis allowed the identification of 9 somatic pathogenic variants in PIK3R1 and PIK3CA, encoding for the regulatory and catalytic subunits of phosphoinositide 3-kinase, respectively. Recharacterization of these lesions unraveled a common phenotype: a pale capillary malformation associated with visible dilated veins. Primary endothelial cells from 2 PIK3R1-mutated lesions were isolated, and PI3k-Akt-mTOR and RAS-RAF-MAPK signaling were assessed by western blot. This unveiled an abnormal increase in Akt phosphorylation, effectively reduced by PI3K pathway inhibitors, such as mTOR, Akt, and PIK3CA inhibitors. The effects of mutant PIK3R1 were further studied using zebrafish embryos. Endothelium-specific expression of PIK3R1 mutants resulted in abnormal development of the posterior capillary-venous plexus. In summary, capillary malformation associated with visible dilated veins emerges as a clinical entity associated with somatic pathogenic variants in PIK3R1 or PIK3CA (nonhotspot). Our findings suggest that the activated Akt signaling can be effectively reversed by PI3K pathway inhibitors. In addition, the proposed zebrafish model holds promise as a valuable tool for future drug screening aimed at developing patient-tailored treatments.

Medical Management and Therapeutic Updates on Vascular Anomalies of the Head and Neck: Part 2

Discovery of inherited and somatic genetic mutations, along with advancements in clinical and scientific research, has improved understanding of vascular anomalies and changed the treatment paradigm. With aim of minimizing need for invasive procedures and improving disease outcomes, molecularly targeted medications and anti-angiogenesis agents have become important as both adjuncts to surgery, and increasingly, as the primary treatment of vascular anomalies. This article highlights the commonly used and emerging therapeutic medications for non-malignant vascular tumors and vascular malformations in addition to medical management of associated hematologic abnormalities.

Medical Therapeutics for the Treatment of Vascular Anomalies: Part 3

The discovery of inherited and somatic genetic mutations, along with advancements in clinical and scientific research, has improved the understanding of vascular anomalies and changed the treatment paradigm. With the aim of minimizing the need for invasive procedures and improving disease outcomes, molecularly targeted medications and anti-angiogenesis agents have become important as both adjuncts to surgery, and increasingly, as the primary treatment of vascular anomalies. This article highlights the commonly used and emerging therapeutic medications for nonmalignant vascular tumors and vascular malformations.

Targeting the microenvironment in the treatment of arteriovenous malformations

Extracranial arteriovenous malformations (AVMs) are regarded as rare diseases and are prone to complications such as pain, bleeding, relentless growth, and high volume of shunted blood. Due to the high vascular pressure endothelial cells of AVMs are exposed to mechanical stress. To control symptoms and lesion growth pharmacological treatment strategies are urgently needed in addition to surgery and interventional radiology. AVM cells were isolated from three patients and exposed to cyclic mechanical stretching for 24 h. Thalidomide and bevacizumab, both VEGF inhibitors, were tested for their ability to prevent the formation of circular networks and proliferation of CD31+ endothelial AVM cells. Furthermore, the effect of thalidomide and bevacizumab on stretched endothelial AVM cells was evaluated. In response to mechanical stress, VEGF gene and protein expression increased in patient AVM endothelial cells. Thalidomide and bevacizumab reduced endothelial AVM cell proliferation. Bevacizumab inhibited circular network formation of endothelial AVM cells and lowered VEGF gene and protein expression, even though the cells were exposed to mechanical stress. With promising in vitro results, bevacizumab was used to treat three patients with unresectable AVMs or to prevent regrowth after incomplete resection. Bevacizumab controlled bleeding, pulsation, and pain over the follow up of eight months with no patient-reported side effects. Overall, mechanical stress increases VEGF expression in the microenvironment of AVM cells. The monoclonal VEGF antibody bevacizumab alleviates this effect, prevents circular network formation and proliferation of AVM endothelial cells in vitro. The clinical application of bevacizumab in AVM treatment demonstrates effective symptom control with no side effects.

Medical Management of Nonmalignant Vascular Tumors of the Head and Neck: Part 1

Vascular anomalies, broadly classified as nonmalignant tumors and malformations, consist of a multitude of disorders that have a wide range of symptoms and complications as well as overlapping clinical, radiologic, and histologic findings. Although usually difficult, distinguishing between nonmalignant vascular tumors and malformations, as well as the precise diagnosis within these distinctions, is critical because prognosis, therapy, and chronicity of care vary greatly. In contrast to normal endothelial turnover in vascular malformations, vascular tumors are characterized by the abnormal proliferation of endothelial cells and aberrant blood vessels.

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.

Factors affecting the ability of patients with complex vascular anomalies to navigate the healthcare system

BACKGROUND

Vascular anomalies (VAs) are rare congenital disorders that can cause pain, disfigurement, coagulopathy, asymmetric growth, and disability. Patients with complex VAs experience multiple barriers to accessing expert care. It is imperative to understand which factors support these patients' ability to navigate the healthcare system.

RESULTS

We surveyed adult patients with VAs using previously validated measures, recruiting participants from five patient advocacy groups and multidisciplinary VA clinics. The primary outcome was self-reported ability to access needed medical care, using the "Navigating the Healthcare System" subscale of the Health Literacy Questionnaire. We evaluated factors associated with the ability to navigate the healthcare system using multivariate linear regression (n = 136). We also performed an exploratory model that included the primary care doctor's knowledge of VAs for the subset of participants with a primary care doctor (n = 114). Participants were predominantly women (n = 90, 66%), White and non-Hispanic (n = 109, 73%), and college-educated (n = 101, 73%). Most participants had PIK3CA-Related Overgrowth Spectrum (n = 107, 78%). Most participants reported that navigating the healthcare system was "sometimes" or "usually difficult" (mean score 16.4/30, standard deviation 5.6). In multivariate linear regression, ability to navigate the healthcare system was associated positively with quality of information exchange (β = 0.38, 95% Confidence Interval (CI) 0.22 to 0.55, p <.001) and whether patients had VA specialists (β = 2.31, 95% CI 0.35 to 4.28, p =.021), but not associated with patient self-advocacy, anxiety, education, age, race and ethnicity, gender, or having a primary care doctor. In exploratory analysis of participants with primary care doctors, ability to navigate the healthcare system was positively associated with quality of information exchange (β = 0.27, 95% CI 0.09 to 0.45, p =.004), having a VA specialist (β = 2.31, 95% CI 0.22 to 4.39, p =.031), and primary care doctors' VA knowledge (β = 0.27, 95% CI 0.04 to 0.50, p =.023).

CONCLUSION

Patients with VAs struggle to navigate the healthcare system. High-quality information from clinicians and more knowledgeable primary care doctors might help patients to access needed care. Relying on patient self-advocacy is insufficient. Future efforts should focus on patient-directed and clinician-directed educational interventions. Additionally, future work should assess the structural barriers that impede healthcare access for these patients.

Infectious complications of vascular anomalies treated with sirolimus: A systematic review

BACKGROUND AND OBJECTIVES

Initially developed as immunosuppressive agents, mammalian target of rapamycin (mTOR) inhibitors are currently used widely in the management of vascular malformations and tumors. The incidence of infectious complications in the vascular anomalies (VA) population is not well defined. The goal of this systematic review was to better define the types and severity of reported infectious complications in patients with VAs treated with mTOR inhibition.

METHODS

This was a systematic review conducted following PRISMA guidelines evaluating all research articles focused on infectious complications in patients with VAs treated with sirolimus or everolimus. Thirty articles including 1182 total patients and 316 infections (in 291 unique patients) were ultimately included.

RESULTS

The majority of infections were viral upper respiratory (n = 137, 54%), followed by pneumonia (n = 53, 20%), and cutaneous infections (n = 20, 8%). There were six total infection-related fatalities, which all occurred in patients younger than 2 years. Two cases of Pneumocystis jirovecii pneumonia (PJP) were reported. These were infants with kaposiform hemangioendothelioma (KHE) who were also treated with steroids and did not receive PJP prophylaxis. Almost one-third (n = 96, 32%) of infectious complications were graded 3-4 according to Common Terminology Criteria for Adverse Events (CTCAE) criteria. Details of patient age, subtype of VA, and timing of infection were lacking from many reports.

CONCLUSIONS

Most infectious complications reported in patients with VA on mTOR inhibitors were viral respiratory infections and non-severe. Bacteremia, infectious fatalities, and PJP are exceedingly rare. Future studies are needed to clarify the spectrum of infectious risks in VA patients and to provide guidance for infection prevention.

Microcystic lymphatic malformations in Turner syndrome are due to somatic mosaicism of PIK3CA

Turner syndrome (45,X) is caused by a complete or partial absence of a single X chromosome. Vascular malformations occur due to abnormal development of blood and/or lymphatic vessels. They arise from either somatic or germline pathogenic variants in the genes regulating growth and apoptosis of vascular channels. Aortic abnormalities are a common, known vascular anomaly of Turner syndrome. However, previous studies have described other vascular malformations as a rare feature of Turner syndrome and suggested that vascular abnormalities in individuals with Turner syndrome may be more generalized. In this study, we describe two individuals with co-occurrence of Turner syndrome and vascular malformations with a lymphatic component. In these individuals, genetic testing of the lesional tissue revealed a somatic pathogenic variant in PIK3CA-a known and common cause of lymphatic malformations. Based on this finding, we conclude that the vascular malformations presented here and likely those previously in the literature are not a rare part of the clinical spectrum of Turner syndrome, but rather a separate clinical entity that may or may not co-occur in individuals with Turner syndrome.

mTOR Pathway Substrates Present High Activation in Vascular Malformations and Significantly Decrease with Age

BACKGROUND

Vascular anomalies often result in aesthetic flaws, pain, and impair the quality of life. They require challenging treatments that frequently do not provide the desired results. The mammalian target of rapamycin (mTOR) is directly involved in the development of these malformations. However, the exact mechanism behind mTOR dysregulation has not been unambiguously defined. The purpose of this study is to investigate the activation of selected substrates of mTOR to partially assess its involvement in the disease process.

METHODS

We analyzed tissue samples collected from patients with vascular anomalies treated in our department. We included patients with histopathological diagnoses of lymphatic, venous, capillary malformations, mixed lesions, and a control group of healthy skin samples. We stained the samples using H and E and immunohistochemistry. We used primary antibodies against p70 S6 Kinase, 4EBP1, and p-4EBP1. We graded their color reactions. The statistical analyses were performed using the FactoMineR and factoextra R v.4.1 packages. p-values < 0.05 were considered statistically significant.

RESULTS

The analysis of 82 patients showed that healthy tissue vessels expressed lower levels of tested mTOR pathway substrates compared to high activation in vascular malformations. Elevated substrate expression in a comparison between sexes revealed higher P-4EBP1 expression in the female malformation group. We observed a decrease in mTOR substrate expression with age.

CONCLUSION

The higher expression of mTOR substrates in vascular malformations compared to healthy tissue confirms their involvement in abnormal vascular development. Age-related changes in mTOR substrate expression highlight the need for timely intervention. Our study contributes to the understanding of the mTOR signaling pathway in vascular malformations and highlights its potential as a therapeutic target, contributing to personalized medicine.

Monogenic Causes of Cerebrovascular Disease in Childhood: A Case Series

BACKGROUND

Despite an increase in the number of genes associated with pediatric stroke, imaging phenotypes in children have not been well reported. Guidelines are needed to facilitate the identification and treatment of patients with monogenic causes of cerebrovascular disorders.

METHODS

We performed a retrospective review of imaging and medical records of patients aged zero to 21 years with monogenic causes of vascular malformations, small or large vessel disease, transient ischemic attacks, and/or ischemic or hemorrhagic stroke. We classified patients according to their imaging phenotype and reviewed neurological and systemic features and management strategies. We reviewed the literature to identify genes associated with cerebrovascular disorders presenting in childhood.

RESULTS

We identified 18 patients with monogenic causes of cerebrovascular disorders and classified each patient as belonging to one or more of three cerebrovascular phenotypes according to predominant imaging characteristics: small vessel disease, large vessel disease, and/or vascular malformations. Preventative treatments included aspirin, N-acetylcysteine, tocilizumab, therapeutic low-molecular-weight heparin, and resection of vascular malformations.

CONCLUSIONS

Classifying pediatric patients with cerebrovascular disorders by imaging phenotype can aid in determining the next steps in genetic testing and treatment.

Ureteropelvic junction obstruction with primary lymphoedema associated with CELSR1 variants

BACKGROUND

Primary lymphoedema (PL) is a chronic, debilitating disease caused by developmental and functional defects of the lymphatic system. It is marked by an accumulation of interstitial fluid, fat and tissue fibrosis. There is no cure. More than 50 genes and genetic loci have been linked to PL. We sought to study systematically cell polarity signalling protein Cadherin Epidermal Growth Factor Laminin G Seven-pass G-type Receptor 1 (CELSR1) variants linked to PL.

METHODS

We investigated 742 index patients from our PL cohort using exome sequencing.

RESULTS

We identified nine variants predicted to cause CELSR1 loss of function. Four of them were tested for nonsense-mediated mRNA decay, but none was observed. Most of the truncated CELSR1 proteins would lack the transmembrane domain, if produced. The affected individuals had puberty/late-onset PL on lower extremities. The variants had a statistically significant difference in penetrance between female patients (87%) and male patients (20%). Eight variant carriers had a kidney anomaly, mostly in the form of ureteropelvic junction obstruction, which has not been associated with CELSR1 before. CELSR1 is located in the 22q13.3 deletion locus of the Phelan-McDermid syndrome. As variable renal defects are often seen in patients with the Phelan-McDermid syndrome, CELSR1 may be the long-sought gene for the renal defects.

CONCLUSION

PL associated with a renal anomaly suggests a CELSR1-related cause.

Netrin 1 directs vascular patterning and maturity in the developing kidney

The intricate vascular system of the kidneys supports body fluid and organ homeostasis. However, little is known about how vascular architecture is established during kidney development. More specifically, how signals from the kidney influence vessel maturity and patterning remains poorly understood. Netrin 1 (Ntn1) is a secreted ligand that is crucial for vessel and neuronal guidance. Here, we demonstrate that Ntn1 is expressed by Foxd1+ stromal progenitors in the developing mouse kidney and conditional deletion (Foxd1GC/+;Ntn1fl/fl) results in hypoplastic kidneys with extended nephrogenesis. Wholemount 3D analyses additionally revealed the loss of a predictable vascular pattern in Foxd1GC/+;Ntn1fl/fl kidneys. As vascular patterning has been linked to vessel maturity, we investigated arterialization. Quantification of the CD31+ endothelium at E15.5 revealed no differences in metrics such as the number of branches or branch points, whereas the arterial vascular smooth muscle metrics were significantly reduced at both E15.5 and P0. In support of our observed phenotypes, whole kidney RNA-seq revealed disruptions to genes and programs associated with stromal cells, vasculature and differentiating nephrons. Together, our findings highlight the significance of Ntn1 to proper vascularization and kidney development.

Preliminary results of the European multicentric phase III trial regarding sirolimus in slow-flow vascular malformations

BACKGROUNDSlow-flow vascular malformations frequently harbor activating mutations in the PI3K/AKT/mTOR cascade. Phase II trials pinpointed sirolimus effectiveness as a drug therapy. Efficacy and safety of sirolimus thus need to be evaluated in large prospective phase III trials.METHODSThe Vascular Anomaly-Sirolimus-Europe (VASE) trial, initiated in 2016, is a large multicentric prospective phase III trial (EudraCT 2015-001703-32), which evaluates efficacy and safety of sirolimus for 2 years in pediatric and adult patients with symptomatic slow-flow vascular malformations. In this interim analysis, we studied all patients enrolled up to October 2021 who received sirolimus for 12 or more months or who prematurely stopped the treatment.RESULTSThirty-one pediatric and 101 adult patients were included in this analysis; 107 completed 12 or more months of sirolimus, including 61 who were treated for the whole 2-year period. Sirolimus resulted in a clinical improvement in 85% of patients. The efficacy appeared within the first month for the majority of them. Grade 3-4 adverse events were observed in 24 (18%) patients; all resolved after treatment interruption/arrest. Sirolimus increased feasibility of surgery or sclerotherapy in 20 (15%) patients initially deemed unsuitable for intervention. Among the 61 patients who completed the 2-year treatment, 33 (54%) reported a recurrence of symptoms after a median follow-up of 13 months after sirolimus arrest. While there was no difference in efficacy, clinical improvement was faster but subsided more rapidly in PIK3CA-mutated (n = 24) compared with TIE2-mutated (n = 19) patients.CONCLUSIONSirolimus has a high efficacy and good tolerance in treatment of slow-flow vascular malformations in children and adults.TRIAL REGISTRATIONClinicalTrials.gov NCT02638389 and EudraCT 2015-001703-32.FUNDINGThe Fonds de la Recherche Scientifique (FNRS grants T.0247.19, P.C005.22, T.0146.16, and P.C013.20), the Fund Generet managed by the King Baudouin Foundation (grant 2018-J1810250-211305), the Walloon Region through the FRFS-WELBIO strategic research programme (WELBIO-CR-2019C-06), the MSCA-ITN network V.A. Cure no. 814316, the Leducq Foundation Networks of Excellence Program grant "ReVAMP" (LFCR grant 21CVD03), the European Union's Horizon 2020 research and innovation programme under grant agreement no. 874708 (Theralymph), the Swiss National Science Foundation under the Sinergia project no. CRSII5_193694, and a Pierre M. fellowship.

miR-182/183-Rasa1 axis induced macrophage polarization and redox regulation promotes repair after ischemic cardiac injury

Few therapies have produced significant improvement in cardiac structure and function after ischemic cardiac injury (ICI). Our possible explanation is activation of local inflammatory responses negatively impact the cardiac repair process following ischemic injury. Factors that can alter immune response, including significantly altered cytokine levels in plasma and polarization of macrophages and T cells towards a pro-reparative phenotype in the myocardium post-MI is a valid strategy for reducing infarct size and damage after myocardial injury. Our previous studies showed that cortical bone stem cells (CBSCs) possess reparative effects after ICI. In our current study, we have identified that the beneficial effects of CBSCs appear to be mediated by miRNA in their extracellular vesicles (CBSC-EV). Our studies showed that CBSC-EV treated animals demonstrated reduced scar size, attenuated structural remodeling, and improved cardiac function versus saline treated animals. These effects were linked to the alteration of immune response, with significantly altered cytokine levels in plasma, and polarization of macrophages and T cells towards a pro-reparative phenotype in the myocardium post-MI. Our detailed in vitro studies demonstrated that CBSC-EV are enriched in miR-182/183 that mediates the pro-reparative polarization and metabolic reprogramming in macrophages, including enhanced OXPHOS rate and reduced ROS, via Ras p21 protein activator 1 (RASA1) axis under Lipopolysaccharides (LPS) stimulation. In summary, CBSC-EV deliver unique molecular cargoes, such as enriched miR-182/183, that modulate the immune response after ICI by regulating macrophage polarization and metabolic reprogramming to enhance repair.

mTORC1 Inhibitor Rapamycin Inhibits Growth of Cerebral Cavernous Malformation in Adult Mice

BACKGROUND

Cerebral cavernous malformations (CCMs) are vascular malformations that frequently cause stroke. CCMs arise due to loss of function in one of the genes that encode the CCM complex, a negative regulator of MEKK3-KLF2/4 signaling in vascular endothelial cells. Gain-of-function mutations in PIK3CA (encoding the enzymatic subunit of the PI3K (phosphoinositide 3-kinase) pathway associated with cell growth) synergize with CCM gene loss-of-function to generate rapidly growing lesions.

METHODS

We recently developed a model of CCM formation that closely reproduces key events in human CCM formation through inducible CCM loss-of-function and PIK3CA gain-of-function in mature mice. In the present study, we use this model to test the ability of rapamycin, a clinically approved inhibitor of the PI3K effector mTORC1, to treat rapidly growing CCMs.

RESULTS

We show that both intraperitoneal and oral administration of rapamycin arrests CCM growth, reduces perilesional iron deposition, and improves vascular perfusion within CCMs.

CONCLUSIONS

Our findings further establish this adult CCM model as a valuable preclinical model and support clinical testing of rapamycin to treat rapidly growing human CCMs.

Overview of peripheral arteriovenous malformations: From diagnosis to treatment methods

Based on the latest classification by the International Society for the Study of Vascular Anomalies in 2018, vascular malformations (VMs) can be categorized into simple, combined VMs of major named vessels, and VMs associated with other anomalies. Simple VMs include lymphatic, venous, capillary, and arteriovenous malformations (AVMs). AVMs represent disorders of direct arteriovenous shunts caused by the absence of a capillary bed between the involved arteries and veins. This abnormal vascular communication causes arterial blood to accumulate in the venous vessels, thus resulting in venous hypertension and characteristic clinical manifestations, such as pulsation, tremors, and elevated temperature. AVMs can occur sporadically or as manifestations of syndromic lesions and are considered among the most complex and challenging VMs. The diagnosis and treatment of AVMs can vary depending on the lesion location and associated clinical symptoms, thus complicating their management. Herein, we discuss peripheral AVMs in terms of their clinical manifestations, imaging examinations, and staging systems to provide a comprehensive reference for the treatment, evaluation methods, and follow-up procedures for this vascular anomaly.

Vascular Anomalies Care in the United States: A Cross-Sectional National Survey

OBJECTIVE

To characterize the current distribution, composition, and practice patterns of multidisciplinary vascular anomalies (VAs) teams in the US.

STUDY DESIGN

This is a cross-sectional survey of children's hospitals in the US offering VAs care. We approached 142 children's hospitals that provided care for VAs via email. The survey evaluated VA clinic location, medical staffing, research participation, and treatments offered. The survey was administered between October 2021 and July 2022.

RESULTS

Participants from 95 eligible hospitals responded to the survey (response rate = 67%). Large areas of the Midwest and Northwest US had no available multidisciplinary VA teams or clinics. Most respondents worked at academic centers (89%), with 66% at a freestanding children's hospital, and 56% reported having a multidisciplinary clinic. Most common physician participants in clinic included hematology-oncology (91%), interventional radiology (87%), dermatology (85%), plastic surgery (81%), and otolaryngology (74%). Only 38% of programs included medical geneticists. Smaller hospitals had fewer medical and ancillary staff and offered fewer therapeutic options. Research was available at most larger institutions (69%) but less commonly at smaller hospitals (34%).

CONCLUSIONS

Major portions of the US lack multidisciplinary VA care. Furthermore, VA programs vary in composition and geneticists are absent from the majority of programs. These findings should inform efforts to address disparate access and develop standards of care for multidisciplinary VA care in the US.

A randomized, placebo-controlled study to evaluate safety and pharmacokinetics of ART-001 with a novel oral pediatric formulation in healthy subjects

ART-001 is an orally available selective PI3Kα inhibitor currently being developed for the treatment of slow-flow vascular malformations (SFVMs). ART-001 used to be developed for advanced solid tumors, but was suspended largely due to significant pharmacokinetic (PK) variability in its phase I studies. This phase I, randomized, double-blinded, placebo-controlled study evaluated safety, tolerability and PK of ART-001 with a newly developed dry syrup formulation, which was designed to optimize PK properties of ART-001 and to be compliant with the pediatric population. Single and multiple doses of ART-001 were administered to healthy male adults. ART-001 was rapidly absorbed after the single and repeated doses, and the exposure of ART-001 increased with increased dose. The dry syrup formulation substantially improved the intersubject PK variability. Food decreased area under the concentration-time curve (AUC) and maximum plasma concentration by 12% and 36%, respectively. The plasma concentration had reached a steady-state on day 5 of the repeated doses of 100 mg and AUC accumulation ratio was 1.9. There were no deaths or serious adverse events. The most frequent adverse event was hyperglycemia. All cases of hyperglycemia were mild to moderate and transient, and required no medical interventions. Serum creatinine increase was observed in 300 mg once daily dosing group leading to dose discontinuation on day 5. In conclusion, it was demonstrated that the single doses and repeated doses of the ART-001 dry syrup formulation, at up to 400 and 100 mg, respectively, were safe and tolerated with favorable PK profile, supporting further clinical development for the treatment of SFVMs.

Repurposing of antiangiogenic agents for treatment of vascular anomalies

Vascular anomalies (VA) are developmental anomalies of veins, arteries, lymphatics or capillaries thought to be caused by mutations in genes that drive angiogenesis. Treatments targeting these genes are limited. We review the literature for conventional medications and products from traditional medicine cultures that have been found to have antiangiogenic activity. Fewer than 50 drugs with credible human activity in VA were identified and include β blockers, monoclonal antibodies, microtubule inhibitors, multi-kinase inhibitors, PIK3CA- and RAS-MAPK pathway inhibitors, and thalidomides. Other drug categories of potential interest are ACE-inhibitors, antifungals, antimalarials, MMP9-inhibitors, and over-the-counter compounds used in Eastern traditional medicine. Low toxicity for some offers the possibility of combined use with known effective agents. In addition to already familiar drugs, others with antiangiogenic capabilities already in use in children or adults may deserve further attention for repurposing for VA.

Penile vascular anomalies: A retrospective single center study and cumulative analysis of studies from China

Objective

Penile vascular anomalies (PVAs) or hemangioma can arouse patient concern about aesthetics and cause symptoms like bleeding and sexual dysfunction. However, its low incidence and the deficiency of large-volume studies hinder urologists from making informed decisions. This study aimed to investigate the clinical features and treatment experience of PVAs at the Seventh Medical Center of PLA General Hospital, Beijing, China. Furthermore, by systematically analysis of studies on PVAs in Chinese people, we aimed to provide novel insights on the management of this condition.

Methods

We retrospectively investigated clinical features and pathology of surgery-treated PVAs at our center. Moreover, by systemically reviewing the literature from PubMed and the three largest medical databases (China National Knowledge Infrastructure, Wan Fang, and Chinese Medical Journal Database) in China, we analyzed the clinical features and various therapies of PVAs in Chinese people.

Results

Between March 1, 2018 and March 1, 2023, a total of 356 cases with vascular anomalies were treated with surgery at out center. Only seven (2.0%) cases had lesions involving the perineum and external genitalia. All the seven cases were pathologically benign and demonstrated no recurrence over a follow-up period of 1-52 months (median 14 months). A total of 410 cases from 44 studies were selected in the cumulative analysis. Most patients (92.4%) diagnosed with PVAs were asymptomatic, and 68.8% of the patients were treated with sclerotherapy. As to the pathology, 57.1% were venous malformation.

Conclusion

The most common PVA is venous malformation and the majority of patients are asymptomatic. Sclerotherapy and laser have emerged as viable options for treating small lesions. Surgery still has its role in treating large lesions and obtaining pathology. Although PVAs often relapse or demand multiple treatments, the prognosis is favorable.

rasa1-related arteriovenous malformation is driven by aberrant venous signalling

Arteriovenous malformations (AVMs) develop where abnormal endothelial signalling allows direct connections between arteries and veins. Mutations in RASA1, a Ras GTPase activating protein, lead to AVMs in humans and, as we show, in zebrafish rasa1 mutants. rasa1 mutants develop cavernous AVMs that subsume part of the dorsal aorta and multiple veins in the caudal venous plexus (CVP) - a venous vascular bed. The AVMs progressively enlarge and fill with slow-flowing blood. We show that the AVM results in both higher minimum and maximum flow velocities, resulting in increased pulsatility in the aorta and decreased pulsatility in the vein. These hemodynamic changes correlate with reduced expression of the flow-responsive transcription factor klf2a. Remodelling of the CVP is impaired with an excess of intraluminal pillars, which is a sign of incomplete intussusceptive angiogenesis. Mechanistically, we show that the AVM arises from ectopic activation of MEK/ERK in the vein of rasa1 mutants, and that cell size is also increased in the vein. Blocking MEK/ERK signalling prevents AVM initiation in mutants. Alterations in venous MEK/ERK therefore drive the initiation of rasa1 AVMs.

SMAD4 maintains the fluid shear stress set point to protect against arterial-venous malformations

Vascular networks form, remodel, and mature under the influence of both fluid shear stress (FSS) and soluble factors. Physiological FSS promotes and maintains vascular stability via synergy with bone morphogenic proteins 9 and 10 (BMP9 and BMP10). Conversely, mutation of the BMP receptors activin-like kinase 1 (ALK1), endoglin (ENG), or the downstream effector, SMAD family member 4 (SMAD4) leads to hereditary hemorrhagic telangiectasia (HHT), characterized by fragile and leaky arterial-venous malformations (AVMs). How endothelial cells (ECs) integrate FSS and BMP signals in vascular development and homeostasis and how mutations give rise to vascular malformations is not well understood. Here, we aimed to elucidate the mechanism of synergy between FSS and SMAD signaling in vascular stability and how disruption of this synergy leads to AVMs. We found that loss of Smad4 increased the sensitivity of ECs to flow by lowering the FSS set point, with resulting AVMs exhibiting features of excessive flow-mediated morphological responses. Mechanistically, loss of SMAD4 disinhibits flow-mediated KLF4-TIE2-PI3K/Akt signaling, leading to cell cycle progression-mediated loss of arterial identity due to KLF4-mediated repression of cyclin dependent Kinase (CDK) inhibitors CDKN2A and CDKN2B. Thus, AVMs caused by Smad4 deletion are characterized by chronic high flow remodeling with excessive EC proliferation and loss of arterial identity as triggering events.

Pathophysiology of Slow-Flow Vascular Malformations: Current Understanding and Unanswered Questions

Background

Slow-flow vascular malformations include venous, lymphatic, and lymphaticovenous malformations. Recent studies have linked genetic variants hyperactivating either the PI3K/AKT/mTOR and/or RAS/RAF/MAPK signaling pathways with slow-flow vascular malformation development, leading to the use of pharmacotherapies such as sirolimus and alpelisib. It is important that clinicians understand basic and translational research advances in slow-flow vascular malformations.

Methods

A literature review of basic science publications in slow-flow vascular malformations was performed on Pubmed, using search terms "venous malformation," "lymphatic malformation," "lymphaticovenous malformation," "genetic variant," "genetic mutation," "endothelial cells," and "animal model." Relevant publications were reviewed and summarized.

Results

The study of patient tissues and the use of primary pathogenic endothelial cells from vascular malformations shed light on their pathological behaviors, such as endothelial cell hyperproliferation and disruptions in vessel architecture. The use of xenograft and transgenic animal models confirmed the pathogenicity of genetic variants and allowed for preclinical testing of potential therapies. These discoveries underscore the importance of basic and translational research in understanding the pathophysiology of vascular malformations, which will allow for the development of improved biologically targeted treatments.

Conclusion

Despite basic and translation advances, a cure for slow-flow vascular malformations remains elusive. Many questions remain unanswered, including how genotype variants result in phenotypes, and genotype-phenotype heterogeneity. Continued research into venous and lymphatic malformation pathobiology is critical in understanding the mechanisms by which genetic variants contribute to vascular malformation phenotypic features.

Seven cases of hereditary haemorrhagic telangiectasia-like hepatic vascular abnormalities associated with EPHB4 pathogenic variants

BACKGROUND

EPHB4 loss of function is associated with type 2 capillary malformation-arteriovenous malformation syndrome, an autosomal dominant vascular disorder. The phenotype partially overlaps with hereditary haemorrhagic telangiectasia (HHT) due to epistaxis, telangiectases and cerebral arteriovenous malformations, but a similar liver involvement has never been described.

METHODS

Members of the French HHT network reported their cases of EPHB4 mutation identified after an initial suspicion of HHT. Clinical, radiological and genetic characteristics were analysed.

RESULTS

Among 21 patients with EPHB4, 15 had a liver imaging, including 7 with HHT-like abnormalities (2 female patients and 5 male patients, ages 43-69 years). Atypical epistaxis and telangiectases were noted in two cases each. They were significantly older than the eight patients with normal imaging (median: 51 vs 20 years, p<0.0006).The main hepatic artery was dilated in all the cases (diameter: 8-11 mm). Six patients had hepatic telangiectases. All kind of shunts were described (arteriosystemic: five patients, arterioportal: two patients, portosystemic: three patients). The overall liver appearance was considered as typical of HHT in six cases.Six EPHB4 variants were classified as pathogenic and one as likely pathogenic, with no specific hot spot.

CONCLUSION

EPHB4 loss-of-function variants can be associated with HHT-like hepatic abnormalities and should be tested for atypical HHT presentations.

Increased Matrix Metalloproteinase-1 Activation Enhances Disruption and Regression of k-RasV12-Expressing Arteriovenous Malformation-Like Vessels

This study sought to identify potential mechanisms by which k-RasV12-expressing endothelial cell (EC) tubes demonstrate an increased propensity to regress compared with controls. Activated k-Ras mutations play a role in a variety of pathological conditions, including arteriovenous malformations, which are prone to bleed, causing serious hemorrhagic complications. ECs expressing active k-RasV12 demonstrate markedly excessive lumen formation with widened and shortened tubes accompanied by reduced pericyte recruitment and basement membrane deposition, leading to deficient capillary network assembly. The current study showed that active k-Ras-expressing ECs secreted greater amounts of MMP-1 proenzyme compared with control ECs, and readily converted it to increased active MMP-1 levels through the action of plasmin or plasma kallikrein (generated from their added zymogens). Active MMP-1 degraded three-dimensional collagen matrices, leading to more rapid and extensive regression of the active k-Ras-expressing EC tubes, in conjunction with matrix contraction, compared with control ECs. Under conditions where pericytes protect control EC tubes from plasminogen- and MMP-1-dependent tube regression, this failed to occur with k-RasV12 ECs, due to reduced pericyte interactions. In summary, k-RasV12-expressing EC vessels showed an increased propensity to regress in response to serine proteinases through accentuated levels of active MMP-1, a novel pathogenic mechanism that may underlie hemorrhagic events associated with arteriovenous malformation lesions.

Genomic profiling informs diagnoses and treatment in vascular anomalies

Vascular anomalies are malformations or tumors of the blood or lymphatic vasculature and can be life-threatening. Although molecularly targeted therapies can be life-saving, identification of the molecular etiology is often impeded by lack of accessibility to affected tissue samples, mosaicism or insufficient sequencing depth. In a cohort of 356 participants with vascular anomalies, including 104 with primary complex lymphatic anomalies (pCLAs), DNA from CD31+ cells isolated from lymphatic fluid or cell-free DNA from lymphatic fluid or plasma underwent ultra-deep sequencing thereby uncovering pathogenic somatic variants down to a variant allele fraction of 0.15%. A molecular diagnosis, including previously undescribed genetic causes, was obtained in 41% of participants with pCLAs and 72% of participants with other vascular malformations, leading to a new medical therapy for 63% (43/69) of participants and resulting in improvement in 63% (35/55) of participants on therapy. Taken together, these data support the development of liquid biopsy-based diagnostic techniques to identify previously undescribed genotype-phenotype associations and guide medical therapy in individuals with vascular anomalies.

Case Report: Kaposiform hemangioendothelioma with PIK3CA mutation successfully treated with sirolimus

Kaposiform hemangioendothelioma (KHE) is an extremely rare, locally aggressive vascular neoplasm. The etiopathogenesis of KHE is still poorly understood. In the present study, we found a new mutation in KHE (c.685delA, p.Thr229fs). The KHE patient with the PIK3CA mutation showed complete regression after sirolimus treatment. We propose that the presence of the PIK3CA mutation in KHE may correlate with good response to sirolimus.

Netrin-1 directs vascular patterning and maturity in the developing kidney

Blood filtering by the kidney requires the establishment of an intricate vascular system that works to support body fluid and organ homeostasis. Despite these critical roles, little is known about how vascular architecture is established during kidney development. More specifically, how signals from the kidney influence vessel maturity and patterning remains poorly understood. Netrin-1 (Ntn1) is a secreted ligand critical for vessel and neuronal guidance. Here, we demonstrate that Ntn1 is expressed by stromal progenitors in the developing kidney, and conditional deletion of Ntn1 from Foxd1+ stromal progenitors (Foxd1GC/+;Ntn1fl/fl) results in hypoplastic kidneys that display extended nephrogenesis. Despite expression of the netrin-1 receptor Unc5c in the adjacent nephron progenitor niche, Unc5c knockout kidneys develop normally. The netrin-1 receptor Unc5b is expressed by embryonic kidney endothelium and therefore we interrogated the vascular networks of Foxd1GC/+;Ntn1fl/fl kidneys. Wholemount, 3D analyses revealed the loss of a predictable vascular pattern in mutant kidneys. As vascular patterning has been linked to vessel maturity, we investigated arterialization in these mutants. Quantification of the CD31+ endothelium at E15.5 revealed no differences in metrics such as the number of branches or branch points, whereas the arterial vascular smooth muscle metrics were significantly reduced at both E15.5 and P0. In support of these results, whole kidney RNA-seq showed upregulation of angiogenic programs and downregulation of muscle-related programs which included smooth muscle-associated genes. Together, our findings highlight the significance of netrin-1 to proper vascularization and kidney development.

MEK inhibition reduced vascular tumor growth and coagulopathy in a mouse model with hyperactive GNAQ

Activating non-inherited mutations in the guanine nucleotide-binding protein G(q) subunit alpha (GNAQ) gene family have been identified in childhood vascular tumors. Patients experience extensive disfigurement, chronic pain and severe complications including a potentially lethal coagulopathy termed Kasabach-Merritt phenomenon. Animal models for this class of vascular tumors do not exist. This has severely hindered the discovery of the molecular consequences of GNAQ mutations in the vasculature and, in turn, the preclinical development of effective targeted therapies. Here we report a mouse model expressing hyperactive mutant GNAQ in endothelial cells. Mutant mice develop vascular and coagulopathy phenotypes similar to those seen in patients. Mechanistically, by transcriptomic analysis we demonstrate increased mitogen activated protein kinase signaling in the mutant endothelial cells. Targeting of this pathway with Trametinib suppresses the tumor growth by reducing vascular cell proliferation and permeability. Trametinib also prevents the development of coagulopathy and improves mouse survival.

Immune-interacting lymphatic endothelial subtype at capillary terminals drives lymphatic malformation

Oncogenic mutations in PIK3CA, encoding p110α-PI3K, are a common cause of venous and lymphatic malformations. Vessel type-specific disease pathogenesis is poorly understood, hampering development of efficient therapies. Here, we reveal a new immune-interacting subtype of Ptx3-positive dermal lymphatic capillary endothelial cells (iLECs) that recruit pro-lymphangiogenic macrophages to promote progressive lymphatic overgrowth. Mouse model of Pik3caH1047R-driven vascular malformations showed that proliferation was induced in both venous and lymphatic ECs but sustained selectively in LECs of advanced lesions. Single-cell transcriptomics identified the iLEC population, residing at lymphatic capillary terminals of normal vasculature, that was expanded in Pik3caH1047R mice. Expression of pro-inflammatory genes, including monocyte/macrophage chemokine Ccl2, in Pik3caH1047R-iLECs was associated with recruitment of VEGF-C-producing macrophages. Macrophage depletion, CCL2 blockade, or anti-inflammatory COX-2 inhibition limited Pik3caH1047R-driven lymphangiogenesis. Thus, targeting the paracrine crosstalk involving iLECs and macrophages provides a new therapeutic opportunity for lymphatic malformations. Identification of iLECs further indicates that peripheral lymphatic vessels not only respond to but also actively orchestrate inflammatory processes.

Prenatal diagnosis of vascular anomalies

Vascular anomalies are rare disorders that encompass a group of lesions characterized by abnormal development of the lymphovascular system. Majority of these anomalies are present at birth and could potentially be detected during the prenatal period on imaging. This allows for early intervention and prompt management to improve outcomes. However, they can be difficult to diagnose, given the rarity and overlapping findings. In this review article, we provide a comprehensive overview of congenital vascular anomalies with a liberal use of images of recent cases at our center emphasizing prenatal imaging findings and the natural history of these conditions.