Junichiro Satomi

Cerebral Vascular Abnormalities in a Murine Model of Hereditary Hemorrhagic Telangiectasia

Background and Purpose— Hereditary hemorrhagic telangiectasia type 1 (HHT1) is an autosomal dominant vascular dysplasia caused by mutations in the endoglin gene and characterized by dilated vessels and arteriovenous malformations (AVMs). To understand the etiology of this disorder, we evaluated the cerebral vasculature of endoglin heterozygous (Eng+/−) mice, which represent the only animal model of HHT1. Methods— The cerebral vasculature of Eng+/− and Eng+/+ mice from C57BL/6 (B6) and 129/Ola (129) strains with a differential susceptibility to HHT1 was studied with corrosion casting. Casts were observed by scanning electron microscopy to detect malformations and evaluate arterial diameters and orientation of endothelial nuclei. Measurements were taken to assess relative constriction at arteriolar branching points and downstream relative dilatation. Results— Three of 10 Eng+/− mice demonstrated abnormal vascular findings including AVMs, while none of 15 Eng+/+ mice did. The incidence of relative constriction at arteriolar branching points was significantly less in both Eng+/− groups than in their Eng+/+ counterparts. The occurrence of relative dilatation was significantly greater in B6-Eng+/− than in B6-Eng+/+ mice. Endothelial nuclei were significantly rounder and deviated more from the direction of blood flow in Eng+/− than in Eng+/+ mice. Conclusions— Eng+/− mice showed significant structural alterations in cerebral blood vessels, indicating that the level of endoglin on endothelium is critical for maintenance of normal vasculature. Since endoglin haploinsufficiency is associated with HHT1, such changes in arteriolar structures might occur in HHT1 patients and predispose them to AVMs and their sequelae.

Angiographic changes in venous drainage of cavernous sinus dural arteriovenous fistulae after palliative transarterial embolization or observational management: a proposed stage classification.

OBJECTIVE:We assessed whether angiographic changes in venous drainage patterns occur over time in cavernous sinus dural arteriovenous fistulae (dAVFs) without a complete cure. METHODS:We classified 65 cavernous sinus dAVFs into three types on the basis of initial angiographic findings. In Type 1, both anterior and posterior drainage routes were open; in Type 2, the posterior drainage route was closed, whereas the anterior drainage route was open; and in Type 3, both the posterior and anterior drainage routes were closed. RESULTS:Of the 65 dAVFs, 40 were of Type 1, 21 of Type 2, and 4 of Type 3. During the follow-up period, 17 of the dAVFs that were treated palliatively with transarterial embolization (n = 11) or monitored without therapy (n = 6) demonstrated angiographic changes. In these 11 patients, there was a change in the venous drainage pattern from Type 1 to Type 2 (n = 5), from Type 2 to Type 3 (n = 3), and from Type 1 to Type 3 (n = 3). One of 11 had a conversion into a lesion with cortical venous drainage. The remaining 6 dAVFs (4 with observational management, 2 with transarterial embolization) demonstrated closure of the fistula; in 5 of these, the affected cavernous sinus was not depicted on follow-up angiograms. CONCLUSION:In some cavernous sinus dAVFs with palliative transarterial embolization or observational management, there was a change in the venous drainage patterns, consisting of a decrease in the number of venous drainage routes. There was a trend for the posterior route to close before the anterior drainage or cortical drainage route. This suggests the occurrence of a staged progression in a regular direction in cavernous sinus dAVFs. Without treatment aiming at a complete cure, most cavernous sinus dAVFs can behave benignly, with a low possibility of development of cortical venous reflux during follow-up.

Phenotypic modulation of smooth muscle cells in human cerebral aneurysmal walls.

Abstract We used immunohistochemical methods to analyze the phenotypes of smooth muscle cells (SMCs) in human cerebral arteries and aneurysmal walls. Thirty-two aneurysmal walls were studied; 31 aneurysmal walls were resected at operation and 1 aneurysm was obtained at autopsy. Seven control arteries were obtained at autopsy. Semiserial sections were subjected to immunohistochemical staining with antibodies to α-smooth muscle actin (α-SMA), desmin and smooth muscle myosin heavy chain isoforms: SM1, SM2 and SMemb. In control cerebral arteries, SMCs in the media were strongly immunostained for α-SMA, desmin, SM1 and SM2; immunoreactivity for SMemb was faint or weakly positive. SMCs in both non-ruptured and ruptured aneurysmal walls showed no staining for desmin; the expression of α-SMA was well preserved. Compared with control cerebral arteries, in 4 of 11 non-ruptured aneurysmal walls, the staining intensity of SMCs for SMemb was clearly increased. In ruptured aneurysmal walls, the expression of SM2 was lower than in control cerebral arteries and non-ruptured aneurysmal walls. Our study suggests that the phenotype of SMCs in aneurysmal walls is different from the contractile type in the media of normal cerebral arteries, at least partially changing to the synthetic type in some non-ruptured aneurysms. SMCs in ruptured aneurysmal walls may have lost both phenotypes before rupture. Phenotypic modulation of SMCs in the aneurysmal walls appears to be related to a remodeling of the aneurysmal wall and to a rupture mechanism.

Reduction of endothelial tight junction proteins is related to cerebral aneurysm formation in rats.

Objective The formation of cerebral aneurysms is associated with endothelial damage and macrophage migration. Hypothesizing that the opening of tight junctions due to the disappearance of the tight junction proteins occludin and zona occludens-1 (ZO-1) in damaged endothelia allows macrophage migration, leading to cerebral aneurysm formation, we investigated the role of tight junction proteins. Methods The vascular wall of female rats subjected to hypertension, oophorectomy (OVX), and hemodynamic stress to induce cerebral aneurysms was evaluated morphologically, immunohistochemically, and by quantitative RT-PCR. We also assessed the regulation of tight junction proteins in human brain endothelial cells (HBECs). Results In the very early stage before aneurysm formation, the expression of occludin and ZO-1 was reduced in injured endothelial cell junctions exhibiting gaps. In the course of aneurysmal progression their reduction progressed and was correlated with macrophage migration. In hypertension along with OVX rats we observed an increase in angiotensin II and the degradation molecules matrix metalloproteinase-9 (MMP-9), nicotinamide-adenine dinucleotide phosphate oxidases and monocyte chemoattractant protein-1. The mineralocorticoid receptor blocker eplerenone increased occludin and ZO-1 expression; this was associated with a reduction in angiotensin II and the degradation molecules and resulted in the inhibition of macrophage exudation and aneurysm formation. In HBECs, occludin and ZO-1 downregulation by angiotensin II and estrogen deficiency was reversed by eplerenone, the MMP inhibitor SB3CT, and apocynin. Our results suggest that macrophage migration is associated with the reduction in tight junction proteins induced by the degradation molecules. Conclusion In rats, the destruction of tight junctions may facilitate macrophage migration and cerebral-aneurysm formation.

Role of Mineralocorticoid Receptor on Experimental Cerebral Aneurysms in Rats

Activation of the renin-angiotensin (Ang)-aldosterone system is involved in the pathology of vascular diseases. Although the blockade of the mineralocorticoid receptor protects against vascular diseases, its role in cerebral aneurysms remains to be elucidated. We treated female rats subjected to renal hypertension, increased hemodynamic stress, and estrogen deficiency for 3 months with the mineralocorticoid receptor blocker eplerenone (30 or 100 mg/kg per day) or vehicle (vehicle control). Eplerenone reduced the incidence of cerebral aneurysms and saline intake without lowering of the blood pressure. In the aneurysmal wall, the production of Ang II and nitrotyrosine was increased. The mRNA levels of Ang-converting enzyme 1 and NADPH oxidase subunits NOX4, Rac1, monocyte chemoattractant protein 1, and matrix metalloproteinase 9 were increased. Eplerenone brought about a reduction in these molecules, suggesting that mineralocorticoid receptor blockade suppresses cerebral aneurysm formation by inhibiting oxidative stress, inflammatory factors, local renin-Ang system activation, and saline intake. Other female rats implanted with pellets of the mineralocorticoid receptor agonist deoxycorticosterone acetate manifested a high incidence of cerebral aneurysm formation and the upregulation of molecules related to oxidative stress, inflammatory factors, and the local renin-Ang system; their saline intake was increased. We demonstrate that mineralocorticoid receptor activation at least partly contributes to the pathogenesis of cerebral aneurysms.

Significance of the Hemorrhagic Site for Recurrent Bleeding: Prespecified Analysis in the Japan Adult Moyamoya Trial

Background and Purpose— The primary results of the Japan Adult Moyamoya Trial revealed the statistically marginal superiority of bypass surgery over medical treatment alone in preventing rebleeding in moyamoya disease. The purpose of this analysis is to test the prespecified subgroup hypothesis that the natural course and surgical effects vary depending on the hemorrhagic site at onset. Methods— The hemorrhagic site, classified as either anterior or posterior, was the only stratifying variable for randomization. Statistical analyses were focused on the assessment of effect modification according to the hemorrhagic site and were based on tests of interaction. Results— Of 42 surgically treated patients, 24 were classified as anterior hemorrhage and 18 as posterior hemorrhage; of 38 medically treated patients, 21 were classified as anterior and 17 as posterior. The hazard ratio of the primary end points (all adverse events) for the surgical group relative to the nonsurgical group was 0.07 (95% confidence interval, 0.01–0.55) for the posterior group, as compared with 1.62 (95% confidence interval, 0.39–6.79) for the anterior group (P=0.013 for interaction). Analysis within the nonsurgical group revealed that the incidence of the primary end point was significantly higher in the posterior group than in the anterior group (17.1% per year versus 3.0% per year; hazard ratio, 5.83; 95% confidence interval, 1.60–21.27). Conclusions— Careful interpretation of the results suggests that patients with posterior hemorrhage are at higher risk of rebleeding and accrue greater benefit from surgery, subject to verification in further studies. Clinical Trial Registration— URL: http://www.umin.ac.jp/ctr/index.htm. Unique identifier: C000000166.

Statins Promote the Growth of Experimentally Induced Cerebral Aneurysms in Estrogen-Deficient Rats

Background and Purpose— The pathogenesis of cerebral aneurysms is linked to inflammation, degradation of the extracellular matrix, and vascular wall apoptosis. Statins exert pleiotropic effects on the vasculature, independent of their cholesterol-lowering properties. To explore the detailed pathogenesis of cerebral aneurysms, we examined their progression in a rat model and studied whether statins prevent their initiation and growth. Methods— Cerebral aneurysms were induced in female rats subjected to hypertension, increased hemodynamic stress, and estrogen deficiency. The development of aneurysm was assessed morphologically on corrosion casts. The effects of pravastatin (5, 25, or 50 mg/kg per day) and of simvastatin (5 mg/kg per day) on their aneurysms were studied. Human brain endothelial cells were also used to determine the effects of pravastatin. Results— Pravastatin (5 mg/kg per day) reduced endothelial damage and inhibited aneurysm formation; there was an association with increased endothelial nitric oxide synthase (eNOS) levels and a decrease in human brain endothelial cell adhesion molecules. Unexpectedly, 25 mg/kg per day and 50 mg/kg per day pravastatin and 5 mg/kg per day simvastatin promoted aneurysmal growth, and high-dose pravastatin induced aneurysmal rupture. The deleterious effects exerted by these statins were associated with an increase in apoptotic caspase-3 levels and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, suggesting that statins exert bidirectional effects. Conclusions— Our results provide the first evidence that cerebral aneurysm growth is partly associated with apoptosis and issue a warning that statins exert bidirectional effects on cerebral aneurysms. Additional intensive research is necessary to understand better their mechanisms and to identify patients in whom the administration of statins may elicit deleterious effects.

Ibudilast inhibits cerebral aneurysms by down-regulating inflammation-related molecules in the vascular wall of rats.

OBJECTIVEPhosphodiesterase-4 (PDE-4) is a cyclic adenosine monophosphate–specific enzyme involved in various inflammatory diseases. We studied its role in and the effect of ibudilast, which predominantly blocks PDE-4, on rat cerebral aneurysms. METHODSCerebral aneurysms were induced at the anterior cerebral artery–olfactory artery bifurcation of female rats subjected to hypertension, increased hemodynamic stress, and estrogen deficiency. The effect of ibudilast (30 or 60 mg/kg/d for 3 months) on their cerebral aneurysms was studied by morphological and immunohistochemical assessment and quantitative real-time polymerase chain reaction assay. In our in vitro study, we grew endothelial cells stimulated by angiotensin II under estrogen-free conditions and examined the effect of ibudilast on PDE-4 activation and the cyclic adenosine monophosphate level. RESULTSMorphological evaluation using vascular corrosion casts showed ibudilast significantly suppressed cerebral aneurysms in a dose-dependent manner. In rats with induced cerebral aneurysms, the gene and protein expression of PDE-4 was high, and endothelial leukocyte adhesion molecules (P-selectin, intracellular adhesion molecule 1, and vascular adhesion molecule 1), matrix metalloproteinase-9, and tumor necrosis α were expressed. Macrophage migration was also increased. Treatment with ibudilast down-regulated these molecules, suppressed macrophage migration into the aneurysm wall, and inhibited PDE-4 activation and the elevation of cyclic adenosine monophosphate in endothelial cells. CONCLUSIONThese results suggest that blocking of PDE4 is associated with the reduction of inflammation-related molecules and macrophage migration, thereby reducing the progression of cerebral aneurysms. It may represent a new conservative therapy to treat patients with cerebral aneurysms.

Activation of estrogen receptor-α and of angiotensin-converting enzyme 2 suppresses ischemic brain damage in oophorectomized rats.

Like the angiotensin II type 1 receptor blocker, endogenous estrogen (17&bgr;-estradiol) is neuroprotective against cerebral ischemia; its effects are thought to be mediated by estrogen receptors (ERs). To verify the role of ERs and the brain renin-angiotensin system in estrogen-deficient rats with ischemia induced by middle cerebral artery occlusion, we compared rats subjected to oophorectomy (OVX+) with sham-oophorectomized rats (OVX−) and OVX+ rats treated with 0.3 or 3.0 mg/kg of olmesartan for 2 weeks before middle cerebral artery occlusion. Independent of the blood pressure, the cortical infarct volume was larger in OVX+ than in OVX− rats. It was smaller in olmesartan-pretreated OVX+ rats. The expression of ER&agr; in the peri-infarct region was correlated with the reduction of cortical infarct but not that of ER&bgr; or G protein–coupled estrogen receptor. Olmesartan prevented ER&agr; downregulation in the cortical peri-infarct area, without affecting ER&bgr; or G protein–coupled estrogen receptor. Olmesartan also increased mRNA expression of angiotensin-converting enzyme 2, Bcl-2, and Bcl-xL and reduced angiotensin II and cleaved caspase 3. These effects were augmented by olmesartan and abolished by the ER inhibitor. In OVX+ rats treated with the ER&agr; agonist alone, the infarct size was decreased, and the neuroprotective genes were upregulated. These findings suggest that the transactivation of neuroprotective genes and the reduction in brain angiotensin II are ER&agr; dependent and that this may augment neuroprotection together with an angiotensin II type 1 receptor blockade by olmesartan. We present the new insight that the activation of ER&agr; independent of estrogen contributes at least partly to limiting cerebral ischemic damage.

Does multimodality therapy of arteriovenous malformations improve patient outcome

Abstract The strategy for treating arteriovenous malformations (AVMs) has undergone changes and long-term follow-up results remain unclear. To compare the outcomes of different treatment strategies, we divided 112 patients with 113 AVMs into groups with hemorrhagic (n = 71, 62.8%) and nonhemorrhagic (n = 42, 37.2%) AVMs and subdivided these according to the period in which they were treated (before/after 1990). In the more recent period, treatment more frequently involved the use of the γ-knife and microembolization to the AVM as well as combination therapy. Long-term follow-up showed that the complication rate was lower and the Rankin scale better, in the more recently treated group. Based on our findings we suggest that AVMs should be treated aggressively using a multimodality strategy.