Missense Variants in COL4A1/2 Are Associated with Cerebral Aneurysms: A Case Report and Literature Review.

BACKGROUND: Although cerebral aneurysm (CA) is a defining complication of COL4A1/2-related vasculopathy, the specific factors influencing its onset remain uncertain. This study aimed to identify and analyze these factors. METHODS: We described a family presenting with a novel variant of the COL4A1 gene complicated with CA. Concurrently, an exhaustive review of previously documented patients with COL4A1/2-related vasculopathy was conducted by sourcing data from PubMed, Web of Science, Google Scholar, and Ichushi databases. We compared the variant types and locations between patients with CA (positive group) and those without CA (negative group). RESULTS: This study included 53 COL4A1/2 variants from 76 patients. Except for one start codon variant, all the identified variants in CA were missense variants. Otherwise, CA was not associated with other clinical manifestations, such as small-vessel disease or other large-vessel abnormalities. A higher frequency of missense variants (95.5% vs. 58.1%, p = 0.0035) was identified in the CA-positive group. CONCLUSIONS: CA development appears to necessitate qualitative alterations in COL4A1/2, and the underlying mechanism seems independent of small-vessel disease or other large-vessel anomalies. Our findings suggest that a meticulous evaluation of CA is necessary when missense variants in COL4A1/2 are identified.

Neuroprotective effects of oral metformin before stroke on cerebral small-vessel disease.

BACKGROUND: Metformin (MET) treatment prior to stroke might have neuroprotective effects other than hypoglycemic effects. This study evaluated whether MET treatment prior to stroke is associated with neurological severity and functional outcome in patients with stroke who were not indicated for endovascular treatment and whether the effects of MET differ for each ischemic stroke subtype. METHODS: We investigated 160 type 2 diabetes mellitus patients with ischemic stroke without endovascular treatment who were taking some oral antidiabetic agents prior to stroke in two tertiary hospitals. Lower neurological severity was defined as a National Institutes of Health Stroke Scale score of 3 or lower on admission, and favorable functional outcome was defined as a modified Rankin Scale score = 0-2 at discharge. We analyzed the effects of MET on the neurological severity and functional outcome in each ischemic stroke subtype on logistic regression analysis with adjustments for multiple confounding factors. RESULTS: MET treatment prior to stroke was associated with lower stroke severity and favorable functional outcome. In the stroke subtypes, MET use affected both neurological severity (P = 0.037) and functional outcome (P = 0.041) in only patients with small-vessel disease (SVD). CONCLUSIONS: MET may be useful to improve the outcome of patients with SVD.

A human induced pluripotent stem cell model from a patient with hereditary cerebral small vessel disease carrying a heterozygous R302Q mutation in HTRA1.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is an inherited cerebral small vessel disease (CSVD) caused by biallelic mutations in the high-temperature requirement serine peptidase A1 (HTRA1) gene. Even heterozygous mutations in HTRA1 are recently revealed to cause cardinal clinical features of CSVD. Here, we report the first establishment of a human induced pluripotent stem cell (hiPSC) line from a patient with heterozygous HTRA1-related CSVD. Peripheral blood mononuclear cells (PBMCs) were reprogrammed by the transfection of episomal vectors encoding human OCT3/4 (POU5F1), SOX2, KLF4, L-MYC, LIN28, and a murine dominant-negative mutant of p53 (mp53DD). The established iPSCs had normal morphology as human pluripotent stem cells and normal karyotype (46XX). Moreover, we found that the HTRA1 missense mutation (c.905G>A, p.R302Q) was heterozygous. These iPSCs expressed pluripotency-related markers and had the potential to differentiate into all three germ layers in vitro. HTRA1 and the supposed disease-associated gene NOG were differentially expressed in the patient iPSCs at mRNA levels compared to those of control lines. The iPSC line would facilitate in vitro research for understanding the cellular pathomechanisms caused by the HTRA1 mutation including its dominant-negative effect.

High frequency of HTRA1 AND ABCC6 mutations in Japanese patients with adult-onset cerebral small vessel disease.

BACKGROUND: This study aimed to clarify the frequency and clinical features of monogenic cerebral small vessel disease (mgCSVD) among patients with adult-onset severe CSVD in Japan. METHODS: This study included patients with adult-onset severe CSVD with an age of onset ≤55 years (group 1) or >55 years and with a positive family history (group 2). After conducting conventional genetic tests for NOTCH3 and HTRA1, whole-exome sequencing was performed on undiagnosed patients. Patients were divided into two groups according to the results of the genetic tests: monogenic and undetermined. The clinical and imaging features were compared between the two groups. RESULTS: Group 1 and group 2 included 75 and 31 patients, respectively. In total, 30 patients had NOTCH3 mutations, 11 patients had HTRA1 mutations, 6 patients had ABCC6 mutations, 1 patient had a TREX1 mutation, 1 patient had a COL4A1 mutation and 1 patient had a COL4A2 mutation. The total frequency of mutations in NOTCH3, HTRA1 and ABCC6 was 94.0% in patients with mgCSVD. In group 1, the frequency of a family history of first relatives, hypertension and multiple lacunar infarctions (LIs) differed significantly between the two groups (monogenic vs undetermined; family history of first relatives, 61.0% vs 25.0%, p=0.0015; hypertension, 34.1% vs 63.9%, p=0.0092; multiple LIs, 87.8% vs 63.9%, p=0.0134). CONCLUSIONS: More than 90% of mgCSVDs were diagnosed by screening for NOTCH3, HTRA1 and ABCC6. The target sequences for these three genes may efficiently diagnose mgCSVD in Japanese patients.

Patients with heterozygous HTRA1-related cerebral small vessel disease misdiagnosed with other diseases: Two case reports.

White matter hyperintensities (WMHs) on brain magnetic resonance (MR) images are characteristic of hereditary cerebral small vessel disease (CSVD), including high-temperature requirement serine peptidase A1 (HTRA1)-related CSVD. Although HTRA1-related CSVD is increasingly recognized, the diagnosis is still challenging. We encountered two patients with HTRA1-related CSVD who were misdiagnosed with other diseases, including multiple sclerosis and idiopathic normal-pressure hydrocephalus. Both patients had extended WMHs in addition to multiple lacunes and microbleeds on brain MR images, which are characteristic of CSVD. If lacunes or microbleeds are found in patients with severe WMHs, genetic tests for hereditary CSVD should be considered.

Candesartan prevents arteriopathy progression in cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy model.

Cerebral small vessel disease (CSVD) causes dementia and gait disturbance due to arteriopathy. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a hereditary form of CSVD caused by loss of high-temperature requirement A1 (HTRA1) serine protease activity. In CARASIL, arteriopathy causes intimal thickening, smooth muscle cell (SMC) degeneration, elastic lamina splitting, and vasodilation. The molecular mechanisms were proposed to involve the accumulation of matrisome proteins as substrates or abnormalities in transforming growth factor ß (TGF-ß) signaling. Here, we show that HTRA1-/- mice exhibited features of CARASIL-associated arteriopathy: intimal thickening, abnormal elastic lamina, and vasodilation. In addition, the mice exhibited reduced distensibility of the cerebral arteries and blood flow in the cerebral cortex. In the thickened intima, matrisome proteins, including the hub protein fibronectin (FN) and latent TGF-ß binding protein 4 (LTBP-4), which are substrates of HTRA1, accumulated. Candesartan treatment alleviated matrisome protein accumulation and normalized the vascular distensibility and cerebral blood flow. Furthermore, candesartan reduced the mRNA expression of Fn1, Ltbp-4, and Adamtsl2, which are involved in forming the extracellular matrix network. Our results indicate that these accumulated matrisome proteins may be potential therapeutic targets for arteriopathy in CARASIL.

Corrigendum: HTRA1 Mutations Identified in Symptomatic Carriers Have the Property of Interfering the Trimer-Dependent Activation Cascade.

[This corrects the article DOI: 10.3389/fneur.2019.00693.].

[Rethinking Lacunar Stroke: Beyond Fisher's Curse].

Lipohyalinosis is an important concept in the independence of lacunar stroke; however, its role has been overemphasized and has led to much confusion in the understanding of lacunar stroke. Classical lipohyalinosis has declined following the widespread availability of antihypertensive therapy, and lacunar stroke secondary to age-related hyaline atherosclerosis is more commonly observed in clinical practice. Clinically diagnosed lacunar stroke is associated with several etiopathogenetic contributors. Excluding cardiogenic embolism, lacunar stroke can be categorized based on the detection of an atheroma. Atheroma imaging is possible in recent years, and strokes that are not associated with an atheroma are shown to present with deep white matter hyperintensity on MRI. Additionally, risk gene analysis has confirmed a group of risk genes associated with the extracellular matrix in lacunar stroke with white matter hyperintensity on MRI. These findings suggest the role of a variety of etiopathogenetic mechanisms underlying lacunar stroke and that lacunar stroke with deep white matter hyperintensity on MRI may be attributable to unique pathogenetic contributors. This group is known to be strongly associated with genetic contributors. Hopefully, lacunar stroke will be diagnosed from this perspective with the development of interventional strategies tailored to the pathogenesis of this condition.

Strategies to prevent hemorrhagic transformation after reperfusion therapies for acute ischemic stroke: A literature review.

BACKGROUND: Reperfusion therapies by tissue plasminogen activator (tPA) and mechanical thrombectomy (MT) have ushered in a new era in the treatment of acute ischemic stroke (AIS). However, reperfusion therapy-related HT remains an enigma. AIM: To provide a comprehensive review focused on emerging concepts of stroke and therapeutic strategies, including the use of protective agents to prevent HT after reperfusion therapies for AIS. METHODS: A literature review was performed using PubMed and the ClinicalTrials.gov database. RESULTS: Risk of HT increases with delayed initiation of tPA treatment, higher baseline glucose level, age, stroke severity, episode of transient ischemic attack within 7 days of stroke onset, and hypertension. At a molecular level, HT that develops after thrombolysis is thought to be caused by reactive oxygen species, inflammation, remodeling factor-mediated effects, and tPA toxicity. Modulation of these pathophysiological mechanisms could be a therapeutic strategy to prevent HT after tPA treatment. Clinical mechanisms underlying HT after MT are thought to involve smoking, a low Alberta Stroke Program Early CT Score, use of general anesthesia, unfavorable collaterals, and thromboembolic migration. However, the molecular mechanisms are yet to be fully investigated. Clinical trials with MT and protective agents have also been planned and good outcomes are expected. CONCLUSION: To fully utilize the easily accessible drug-tPA-and the high recanalization rate of MT, it is important to reduce bleeding complications after recanalization. A future study direction could be to investigate the recovery of neurological function by combining reperfusion therapies with cell therapies and/or use of pleiotropic protective agents.

HTRA1-Related Cerebral Small Vessel Disease: A Review of the Literature.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is clinically characterized by early-onset dementia, stroke, spondylosis deformans, and alopecia. In CARASIL cases, brain magnetic resonance imaging reveals severe white matter hyperintensities (WMHs), lacunar infarctions, and microbleeds. CARASIL is caused by a homozygous mutation in high-temperature requirement A serine peptidase 1 (HTRA1). Recently, it was reported that several heterozygous mutations in HTRA1 also cause cerebral small vessel disease (CSVD). Although patients with heterozygous HTRA1-related CSVD (symptomatic carriers) are reported to have a milder form of CARASIL, little is known about the clinical and genetic differences between the two diseases. Given this gap in the literature, we collected clinical information on HTRA1-related CSVD from a review of the literature to help clarify the differences between symptomatic carriers and CARASIL and the features of both diseases. Forty-six symptomatic carriers and 28 patients with CARASIL were investigated. Twenty-eight mutations in symptomatic carriers and 22 mutations in CARASIL were identified. Missense mutations in symptomatic carriers are more frequently identified in the linker or loop 3 (L3)/loop D (LD) domains, which are critical sites in activating protease activity. The ages at onset of neurological symptoms/signs were significantly higher in symptomatic carriers than in CARASIL, and the frequency of characteristic extraneurological findings and confluent WMHs were significantly higher in CARASIL than in symptomatic carriers. As previously reported, heterozygous HTRA1-related CSVD has a milder clinical presentation of CARASIL. It seems that haploinsufficiency can cause CSVD among symptomatic carriers according to the several patients with heterozygous nonsense/frameshift mutations. However, the differing locations of mutations found in the two diseases indicate that distinct molecular mechanisms influence the development of CSVD in patients with HTRA1-related CSVD. These findings further support continued careful examination of the pathogenicity of mutations located outside the linker or LD/L3 domain in symptomatic carriers.

Excessive Production of Transforming Growth Factor ß1 Causes Mural Cell Depletion From Cerebral Small Vessels.

It is increasingly becoming apparent that cerebrovascular dysfunction contributes to the pathogenic processes involved in vascular dementia, Alzheimer's disease, and other neurodegenerative disorders. Under these pathologic conditions, the degeneration of cerebral blood vessels is frequently accompanied by a loss of mural cells from the vascular walls. Vascular mural cells play pivotal roles in cerebrovascular functions, such as regulation of cerebral blood flow and maintenance of the blood-brain barrier (BBB). Therefore, cerebrovascular mural cell impairment is involved in the pathophysiology of vascular-related encephalopathies, and protecting these cells is essential for maintaining brain health. However, our understanding of the molecular mechanism underlying mural cell abnormalities is incomplete. Several reports have indicated that dysregulated transforming growth factor ß (TGFß) signaling is involved in the development of cerebral arteriopathies. These studies have specifically suggested the involvement of TGFß overproduction. Although cerebrovascular toxicity via vascular fibrosis by extracellular matrix accumulation or amyloid deposition is known to occur with enhanced TGFß production, whether increased TGFß results in the degeneration of vascular mural cells in vivo remains unknown. Here, we demonstrated that chronic TGFß1 overproduction causes a dropout of mural cells and reduces their coverage on cerebral vessels in both smooth muscle cells and pericytes. Mural cell degeneration was also accompanied by vascular luminal dilation. TGFß1 overproduction in astrocytes significantly increased TGFß1 content in the cerebrospinal fluid (CSF) and increased TGFß signaling-regulated gene expression in both pial arteries and brain capillaries. These results indicate that TGFß is an important effector that mediates mural cell abnormalities under pathological conditions related to cerebral arteriopathies.

[Dural arteriovenous fistula causing complex visual hallucinations without an anopsia].

We report the case of a 76-year-old woman who presented with recurrent episodes of complex visual hallucinations in her right visual field without an anopsia. The electroencephalogram showed sharp transients in the left parietotemporal region with phase reversals at T5 and P3. FLAIR MRI revealed hyperintense lesions in the left temporo-occipital lobe, located mainly in the left inferior temporal lobe. Cerebral angiography revealed an arteriovenous shunt from the left occipital artery to the left transverse sinus with cortical venous reflux. The complex visual hallucinations were resolved after transarterial embolization. We therefore hypothesize that this patient's complex visual hallucinations were caused by epileptic seizures or changes in cortical blood flow caused by the cortical venous reflux from the arteriovenous fistula. In general, epileptic hallucinations expand into the bilateral visual field. We reveal that in rare cases, complex visual hallucinations can also be limited to the unilateral visual field without an anopsia. Additionally, we reveal that a dural arteriovenous fistula can cause visual hallucinations without hemianopia.

HTRA1 Mutations Identified in Symptomatic Carriers Have the Property of Interfering the Trimer-Dependent Activation Cascade.

Background: Mutations in the high-temperature requirement A serine peptidase 1 (HTRA1) cause cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Most carriers for HTRA1 mutations are asymptomatic, but more than 10 mutations have been reported in symptomatic carriers. The molecular differences between the mutations identified in symptomatic carriers and mutations identified only in CARASIL patients are unclear. HTRA1 is a serine protease that forms homotrimers, with each HTRA1 subunit activating the adjacent HTRA1 via the sensor domain of loop 3 (L3) and the activation domain of loop D (LD). Previously, we analyzed four HTRA1 mutant proteins identified in symptomatic carriers and found that they were unable to form trimers or had mutations in the LD or L3 domain. The mutant HTRA1s with these properties are presumed to inhibit trimer-dependent activation cascade. Indeed, these mutant HTRA1s inhibited wild-type (WT) protease activity. In this study, we further analyzed 15 missense HTRA1s to clarify the molecular character of mutant HTRA1s identified in symptomatic carriers. Methods: We analyzed 12 missense HTRA1s identified in symptomatic carriers (hetero-HTRA1) and three missense HTRA1s found only in CARASIL (CARASIL-HTRA1). The protease activity of the purified recombinant mutant HTRA1s was measured using fluorescein isothiocyanate-labeled casein as substrate. Oligomeric structure was evaluated by size-exclusion chromatography. The protease activities of mixtures of WT with each mutant HTRA1 were also measured. Results: Five hetero-HTRA1s had normal protease activity and were excluded from further analysis. Four of the seven hetero-HTRA1s and one of the three CARASIL-HTRA1s were unable to form trimers. The other three hetero-HTRA1s had mutations in the LD domain. Together with our previous work, 10 of 11 hetero-HTRA1s and two of six CARASIL-HTRA1s were either defective in trimerization or had mutations in the LD or L3 domain (P = 0.006). By contrast, eight of 11 hetero-HTRA1s and two of six CARASIL-HTRA1 inhibited WT protease activity (P = 0.162). Conclusions: HTRA1 mutations identified in symptomatic carriers have the property of interfering the trimer-dependent activation cascade of HTRA1.

[Cerebral Autosomal Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CARASIL)].

Cerebral small vessel disease (CSVD) is frequently observed among the elderly and is known to cause dementia and gait disturbance associated with white matter lesions, lacunar infarcts, and cerebral hemorrhage. Molecular mechanistic studies promise to provide new insights into the pathogenesis of hereditary CSVD. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is one of the hereditary CSVDs caused by a mutation in the high-temperature requirement serine peptidase A1 (HTRA1) gene. The loss of HTRA1 protease activity increases signaling via transforming growth factor (TGF)ß, thereby resulting in CARASIL. Although the CARASIL has been characterized by juvenile onset alopecia and spondylosis deformans, these features are not always observed in individuals with an HTRA1 mutation. Moreover, some HTRA1 mutations cause CSVD in heterozygous states. Therefore, the clinical features of CSVD resulting from an HTRA1 mutation extend to patients with CSVD alone or to those with dominantly inherited CSVD.

Visualization of the Intimal Flap in Intracranial Arterial Dissection Using High-Resolution 3T MRI.

BACKGROUND AND PURPOSE: Presence of an intimal flap is a critical imaging finding in diagnosing intracranial artery dissection (ICAD). Recent reports showed that high-resolution magnetic resonance imaging (MRI) was better at identifying intimal flaps as compared with routine MRI techniques used in clinical settings. However, no current standardized sequence for high-resolution MRI without gadolinium enhancement produces images of satisfactory quality with clinically tolerable scanning times. This study evaluated a nonenhanced high-resolution fast spin echo (HR-FSE) MRI sequence for visualizing intimal flaps in patients with ICAD. SUBJECTS AND METHODS: Three patients with ICAD underwent plain MRI examination using a 2-dimensional T2-weighted FSE imaging sequence optimized for our 3T system (in-plane pixel size, .23 mm × .23 mm; slice thickness 3 mm with no interslice gap), as well as scanning with conventional modalities, including CT angiography, magnetic resonance angiography, and digital subtraction angiography. We assessed whether these imaging methods could visualize an intimal flap and/or double lumen sign in the participants and compared the results between HR-FSE and the other modalities. RESULTS: HR-FSE images clearly showed intimal flaps and double lumen signs in all 3 patients, whereas the conventional modalities identified a double lumen sign in only 2 of the 3 patients. CONCLUSIONS: The present method of optimized HR-FSE imaging with a 3T system improved visualization of intimal flaps and should thus be considered for assessing patients with suspected ICAD that cannot be definitively diagnosed by conventional imaging modalities.