transforming-growth-factor-beta and Hemangioma--Cavernous--Central-Nervous-System

Correct organization of the vascular tree requires the balanced activities of several signaling pathways that regulate tubulogenesis and vascular branching, elongation, and pruning. When this balance is lost, the vessels can be malformed and fragile, and they can lose arteriovenous differentiation. In this review, we concentrate on the transforming growth factor (TGF)-β/bone morphogenetic protein (BMP) pathway, which is one of the most important and complex signaling systems in vascular development. Inactivation of these pathways can lead to altered vascular organization in the embryo. In addition, many vascular malformations are related to deregulation of TGF-β/BMP signaling. Here, we focus on two of the most studied vascular malformations that are induced by deregulation of TGF-β/BMP signaling: hereditary hemorrhagic telangiectasia (HHT) and cerebral cavernous malformation (CCM). The first of these is related to loss-of-function mutation of the TGF-β/BMP receptor complex and the second to increased signaling sensitivity to TGF-β/BMP. In this review, we discuss the potential therapeutic targets against these vascular malformations identified so far, as well as their basis in general mechanisms of vascular development and stability.

Topics: Animals; Blood Vessels; Bone Morphogenetic Proteins; Disease Models, Animal; Genetic Predisposition to Disease; Hemangioma, Cavernous, Central Nervous System; Humans; Mice, Transgenic; Mutation; Neovascularization, Physiologic; Phenotype; Risk Factors; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Malformations

Cerebral cavernous malformations (CCMs) are vascular malformations located within the central nervous system often resulting in cerebral hemorrhage. Pharmacological treatment is needed, since current therapy is limited to neurosurgery. Familial CCM is caused by loss-of-function mutations in any of Ccm1, Ccm2, and Ccm3 genes. CCM cavernomas are lined by endothelial cells (ECs) undergoing endothelial-to-mesenchymal transition (EndMT). This switch in phenotype is due to the activation of the transforming growth factor beta/bone morphogenetic protein (TGFβ/BMP) signaling. However, the mechanism linking Ccm gene inactivation and TGFβ/BMP-dependent EndMT remains undefined. Here, we report that Ccm1 ablation leads to the activation of a MEKK3-MEK5-ERK5-MEF2 signaling axis that induces a strong increase in Kruppel-like factor 4 (KLF4) in ECs in vivo. KLF4 transcriptional activity is responsible for the EndMT occurring in CCM1-null ECs. KLF4 promotes TGFβ/BMP signaling through the production of BMP6. Importantly, in endothelial-specific Ccm1 and Klf4 double knockout mice, we observe a strong reduction in the development of CCM and mouse mortality. Our data unveil KLF4 as a therapeutic target for CCM.

Topics: Animals; Bone Morphogenetic Protein 6; Cell Proliferation; Disease Models, Animal; Disease Progression; Endothelial Cells; HEK293 Cells; Hemangioma, Cavernous, Central Nervous System; Humans; KRIT1 Protein; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; Mice; Mice, Inbred C57BL; Mice, Knockout; Microtubule-Associated Proteins; Mitogen-Activated Protein Kinase 7; Mutation; Proto-Oncogene Proteins; RNA Interference; Signal Transduction; Smad1 Protein; Transforming Growth Factor beta

Cerebral cavernous malformation (CCM) is a disease of the central nervous system causing hemorrhage-prone multiple lumen vascular malformations and very severe neurological consequences. At present, the only recommended treatment of CCM is surgical. Because surgery is often not applicable, pharmacological treatment would be highly desirable. We describe here a murine model of the disease that develops after endothelial-cell-selective ablation of the CCM3 gene. We report an early, cell-autonomous, Wnt-receptor-independent stimulation of β-catenin transcription activity in CCM3-deficient endothelial cells both in vitro and in vivo and a triggering of a β-catenin-driven transcription program that leads to endothelial-to-mesenchymal transition. TGF-β/BMP signaling is then required for the progression of the disease. We also found that the anti-inflammatory drugs sulindac sulfide and sulindac sulfone, which attenuate β-catenin transcription activity, reduce vascular malformations in endothelial CCM3-deficient mice. This study opens previously unidentified perspectives for an effective pharmacological therapy of intracranial vascular cavernomas.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Apoptosis Regulatory Proteins; beta Catenin; Central Nervous System Neoplasms; Disease Models, Animal; Endothelial Cells; Gene Expression Regulation, Neoplastic; Hemangioma, Cavernous, Central Nervous System; Immunohistochemistry; Intracellular Signaling Peptides and Proteins; Mice, Knockout; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Sulindac; Transforming Growth Factor beta

Cerebral cavernous malformation (CCM) is a vascular dysplasia, mainly localized within the brain and affecting up to 0.5% of the human population. CCM lesions are formed by enlarged and irregular blood vessels that often result in cerebral haemorrhages. CCM is caused by loss-of-function mutations in one of three genes, namely CCM1 (also known as KRIT1), CCM2 (OSM) and CCM3 (PDCD10), and occurs in both sporadic and familial forms. Recent studies have investigated the cause of vascular dysplasia and fragility in CCM, but the in vivo functions of this ternary complex remain unclear. Postnatal deletion of any of the three Ccm genes in mouse endothelium results in a severe phenotype, characterized by multiple brain vascular malformations that are markedly similar to human CCM lesions. Endothelial-to-mesenchymal transition (EndMT) has been described in different pathologies, and it is defined as the acquisition of mesenchymal- and stem-cell-like characteristics by the endothelium. Here we show that endothelial-specific disruption of the Ccm1 gene in mice induces EndMT, which contributes to the development of vascular malformations. EndMT in CCM1-ablated endothelial cells is mediated by the upregulation of endogenous BMP6 that, in turn, activates the transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) signalling pathway. Inhibitors of the TGF-β and BMP pathway prevent EndMT both in vitro and in vivo and reduce the number and size of vascular lesions in CCM1-deficient mice. Thus, increased TGF-β and BMP signalling, and the consequent EndMT of CCM1-null endothelial cells, are crucial events in the onset and progression of CCM disease. These studies offer novel therapeutic opportunities for this severe, and so far incurable, pathology.

Topics: Animals; Bone Morphogenetic Protein 6; Disease Models, Animal; Disease Progression; Epithelial-Mesenchymal Transition; Hemangioma, Cavernous, Central Nervous System; Humans; KRIT1 Protein; Mice; Microtubule-Associated Proteins; Proto-Oncogene Proteins; Signal Transduction; Transforming Growth Factor beta; Up-Regulation

The authors studied the expression of angiogenic and growth factors and various proliferative indices in cavernous angiomas of the brain. The goal was to define whether the often progressive clinical course of both sporadic and familial forms of the lesion is correlated with different expression of these factors.. Forty-three cavernomas of the brain were investigated with immunohistochemical studies and stained for four growth factors (vascular endothelial growth factor [VEGF], tenascin, transforming growth factor-b [TGFb], and platelet-derived growth factor [PDGF]), and for Ki-67 and bcl-2. The intensity of expression was tested in all cases in the walls of cavernoma vessels, in the perivascular tissue, and in the perilesional brain parenchyma. Among the 43 cavernomas, 32 were stable and sporadic single lesions less than 2 cm in size, whereas 11 were cavernomas larger than 2 cm (up to 6 cm). These larger cavernomas had more aggressive behavior (documented growth in five cases, mass effect in eight, significant hemorrhage in four), familial occurrence (six cases), and/or multiple lesions (five cases). The expression of VEGF, tenascin, and PDGF in cavernomas did not significantly differ in the two groups of patients, whereas TGFb expression was higher in the more aggressive forms of cavernomas. The expression of Ki-67 and bcl-2 was always absent in stable lesions, and it was positive in eight (72.7%) of 11 aggressive lesions. The perilesional brain parenchyma showed a significantly higher expression of TGFb, PDGF, and tenascin in more aggressive cavernomas.. The familial occurrence and more aggressive clinical behavior of cavernous angiomas of the brain are associated with higher expression of Ki-67 and bcl-2 in the cavernoma tissue, as in other proliferative lesions. These features are also associated with higher expression of some growth factors (excluding VEGF) in the perilesional brain parenchyma, suggesting that the neighboring vasculature and glia may be predisposed to and recruited for further growth and progression.

Topics: Adolescent; Adult; Aged; Angiogenic Proteins; Brain Neoplasms; Cerebral Veins; Child; Child, Preschool; Disease Progression; Endothelial Cells; Female; Growth Substances; Hemangioma, Cavernous, Central Nervous System; Humans; Inheritance Patterns; Ki-67 Antigen; Male; Middle Aged; Neovascularization, Pathologic; Platelet-Derived Growth Factor; Proto-Oncogene Proteins c-bcl-2; Tenascin; Transforming Growth Factor beta; Up-Regulation; Vascular Endothelial Growth Factor A

Topics: Angiopoietins; Central Nervous System Vascular Malformations; Fibroblast Growth Factor 2; Gene Expression; Genetic Counseling; Genetic Therapy; Genotype; Hemangioma, Cavernous, Central Nervous System; Hepatocyte Growth Factor; Humans; Phenotype; Platelet-Derived Growth Factor; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A