White matter damage is associated with matrix metalloproteinases in vascular dementia

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

CCR2+ monocytes promote white matter injury and cognitive dysfunction after myocardial infarction

Survivors of myocardial infarction are at increased risk for vascular dementia. Neuroinflammation has been implicated in the pathogenesis of vascular dementia, yet little is known about the cellular and molecular mediators of neuroinflammation after myocardial infarction. Using a mouse model of myocardial infarction coupled with flow cytometric analyses and immunohistochemistry, we discovered increased monocyte abundance in the brain after myocardial infarction, which was associated with increases in brain-resident perivascular macrophages and microglia. Myeloid cell recruitment and activation was also observed in post-mortem brains of humans that died after myocardial infarction. Spatial and single cell transcriptomic profiling of brain-resident myeloid cells after experimental myocardial infarction revealed increased expression of monocyte chemoattractant proteins. In parallel, myocardial infarction increased crosstalk between brain-resident myeloid cells and oligodendrocytes, leading to neuroinflammation, white matter injury, and cognitive dysfunction. Inhibition of monocyte recruitment preserved white matter integrity and cognitive function, linking monocytes to neurodegeneration after myocardial infarction. Together, these preclinical and clinical results demonstrate that monocyte infiltration into the brain after myocardial infarction initiate neuropathological events that lead to vascular dementia.

Hexahydrocurcumin attenuated demyelination and improved cognitive impairment in chronic cerebral hypoperfusion rats

Age-related white matter lesions (WML) frequently present vascular problems by decreasing cerebral blood supply, resulting in the condition known as chronic cerebral hypoperfusion (CCH). This study aimed to investigate the effect of hexahydrocurcumin (HHC) on the processes of demyelination and remyelination induced by the model of the Bilateral Common Carotid Artery Occlusion (BCCAO) for 29 days to mimic the CCH condition. The pathological appearance of myelin integrity was significantly altered by CCH, as evidenced by Transmission Electron Microscopy (TEM) and Luxol Fast Blue (LFB) staining. In addition, CCH activated A1-astrocytes and reactive-microglia by increasing the expression of Glial fibrillary acidic protein (GFAP), complement 3 (C3d) and pro-inflammatory cytokines. However, S100a10 expression, a marker of neuroprotective astrocytes, was suppressed, as were regenerative factors including (IGF-1) and Transglutaminase 2 (TGM2). Therefore, the maturation step was obstructed as shown by decreases in the levels of myelin basic protein (MBP) and the proteins related with lipid synthesis. Cognitive function was therefore impaired in the CCH model, as evidenced by the Morris water maze test. By contrast, HHC treatment significantly improved myelin integrity, and inhibited A1-astrocytes and reactive-microglial activity. Consequently, pro-inflammatory cytokines and A1-astrocytes were attenuated, and regenerative factors increased assisting myelin maturation and hence improving cognitive performance. In conclusion, HHC improves cognitive function and also the integrity of white matter in CCH rats by reducing demyelination, and pro-inflammatory cytokine production and promoting the process of remyelination.

Blood-based biomarkers of cerebral small vessel disease

Age-associated cerebral small vessel disease (CSVD) represents a clinically heterogenous condition, arising from diverse microvascular mechanisms. These lead to chronic cerebrovascular dysfunction and carry a substantial risk of subsequent stroke and vascular cognitive impairment in aging populations. Owing to advances in neuroimaging, in vivo visualization of cerebral vasculature abnormities and detection of CSVD, including lacunes, microinfarcts, microbleeds and white matter lesions, is now possible, but remains a resource-, skills- and time-intensive approach. As a result, there has been a recent proliferation of blood-based biomarker studies for CSVD aimed at developing accessible screening tools for early detection and risk stratification. However, a good understanding of the pathophysiological processes underpinning CSVD is needed to identify and assess clinically useful biomarkers. Here, we provide an overview of processes associated with CSVD pathogenesis, including endothelial injury and dysfunction, neuroinflammation, oxidative stress, perivascular neuronal damage as well as cardiovascular dysfunction. Then, we review clinical studies of the key biomolecules involved in the aforementioned processes. Lastly, we outline future trends and directions for CSVD biomarker discovery and clinical validation.

Regional contribution of vascular dysfunction in white matter dementia: clinical and neuropathological insights

The maintenance of adequate blood supply and vascular integrity is fundamental to ensure cerebral function. A wide range of studies report vascular dysfunction in white matter dementias, a group of cerebral disorders characterized by substantial white matter damage in the brain leading to cognitive impairment. Despite recent advances in imaging, the contribution of vascular-specific regional alterations in white matter dementia has been not extensively reviewed. First, we present an overview of the main components of the vascular system involved in the maintenance of brain function, modulation of cerebral blood flow and integrity of the blood-brain barrier in the healthy brain and during aging. Second, we review the regional contribution of cerebral blood flow and blood-brain barrier disturbances in the pathogenesis of three distinct conditions: the archetypal white matter predominant neurocognitive dementia that is vascular dementia, a neuroinflammatory predominant disease (multiple sclerosis) and a neurodegenerative predominant disease (Alzheimer's). Finally, we then examine the shared landscape of vascular dysfunction in white matter dementia. By emphasizing the involvement of vascular dysfunction in the white matter, we put forward a hypothetical map of vascular dysfunction during disease-specific progression to guide future research aimed to improve diagnostics and facilitate the development of tailored therapies.

Chronic cerebral hypoperfusion: a critical feature in unravelling the etiology of vascular cognitive impairment

Vascular cognitive impairment (VCI) describes a wide spectrum of cognitive deficits related to cerebrovascular diseases. Although the loss of blood flow to cortical regions critically involved in cognitive processes must feature as the main driver of VCI, the underlying mechanisms and interactions with related disease processes remain to be fully elucidated. Recent clinical studies of cerebral blood flow measurements have supported the role of chronic cerebral hypoperfusion (CCH) as a major driver of the vascular pathology and clinical manifestations of VCI. Here we review the pathophysiological mechanisms as well as neuropathological changes of CCH. Potential interventional strategies for VCI are also reviewed. A deeper understanding of how CCH can lead to accumulation of VCI-associated pathology could potentially pave the way for early detection and development of disease-modifying therapies, thus allowing preventive interventions instead of symptomatic treatments.

Chronic cerebral hypoperfusion alters the CypA-EMMPRIN-gelatinase pathway: Implications for vascular dementia

Chronic cerebral hypoperfusion (CCH) is postulated to underlie multiple pathophysiological processes in vascular dementia (VaD), including extracellular matrix dysfunction. While several extracellular matrix proteins, namely cyclophilin A (CypA), extracellular matrix metalloproteinase inducer (EMMPRIN) and gelatinases (matrix metalloproteinases, MMP-2 and -9) have been investigated in acute stroke, their involvement in CCH and VaD remains unclear. In this study, CypA-EMMPRIN-gelatinase proteins were analysed in a clinical cohort of 36 aged, cognitively unimpaired subjects and 48 VaD patients, as well as in a bilateral carotid artery stenosis mouse model of CCH. Lower CypA and higher EMMPRIN levels were found in both VaD serum and CCH mouse brain. Furthermore, gelatinases were differentially altered in CCH mice and VaD patients, with significant MMP-2 increase in CCH brain and serum, whilst serum MMP-9 was elevated in VaD but reduced in CCH, suggesting complex CypA-EMMPRIN-gelatinase regulatory mechanisms. Interestingly, subjects with cortical infarcts had higher serum MMP-2, while white matter hyperintensities, cortical infarcts and lacunes were associated with higher serum MMP-9. Taken together, our data indicate that perturbations of CypA-EMMPRIN signalling may be associated with gelatinase-mediated vascular sequelae, highlighting the potential utility of the CypA-EMMPRIN-gelatinase pathway as clinical biomarkers and therapeutic targets in VaD.

Association between Systemic Immune Inflammation Index and Cognitive Impairment after Acute Ischemic Stroke

Background and Aims: Post-stroke cognitive impairment (PSCI) is one of the major complications after ischemic stroke. PSCI has been shown to be associated with low-grade systemic inflammation. As a novel inflammatory marker, the systemic immune-inflammation (SII) index could reflect clinical outcomes in severe cardiovascular diseases. We therefore performed a prospective study to investigate the correlation between the SII index and the risk of PSCI in patients with ischemic stroke. Methods: We prospectively enrolled 254 patients with ischemic stroke with symptoms onset <72 h. The SII index was detected within 24 h after admission. The Montreal Cognitive Scale (MoCA) was utilized to evaluate cognitive function, and PSCI was defined as a MoCA score of <25 points. Results: During the 3-month follow-up, 70 participants (27.6%) had mild cognitive impairment and 60 (23.6%) had severe cognitive impairment. In binary logistic regression analysis, each one-standard deviation increase in the SII index was significantly associated with the prevalence of PSCI after adjusting for age, sex, and other confounders (odds ratio 2.341; 95% confidence interval, 1.439–3.809, p = 0.001). Similar significant findings were observed when SII was defined as a categorical variable. In addition, the multiple-adjusted spline regression model showed a linear association between the SII index and cognitive impairment (p = 0.003 for linearity). Conclusions: Our study indicated that an increased SII index was closely related to PSCI at 3 months in patients with ischemic stroke. Further research is required to evaluate the efficacy of inflammation management in these patients.

Association of Brain Arterial Elongation With Risk of Stroke and Death in Stroke-Free Individuals: Results From NOMAS

BACKGROUND

Brain arterial dilation and elongation characterize dolichoectasia, an arteriopathy associated with risk of stroke and death. We aim to determine whether brain arterial elongation increases the risk of stroke and death independent of brain arterial diameters.

METHODS

We analyzed 1210 stroke-free participants (mean age 71±9 years, 41% men, 65% Hispanic) with available time-of-flight magnetic resonance angiogram from the Northern Manhattan Study, a population-based cohort study across a multiethnic urban community. We obtained baseline middle cerebral artery M1-segment (MCA-M1) and basilar artery (BA) mean lengths and diameters using a semi-automated software. Cox proportional hazards models adjusted for brain arterial diameters and potential confounders yielded adjusted hazards ratios with 95% CIs for the primary outcomes of incident stroke and all-cause mortality, as well as secondary outcomes including noncardioembolic stroke, vascular death, and any vascular event.

RESULTS

Neither MCA-M1 nor BA lengths correlated with incident stroke or all-cause mortality. Both MCA-M1 and BA larger diameters correlated with all-cause mortality (MCA-M1 aHR, 1.52 [95% CI, 1.03-2.23], BA aHR, 1.28 [95% CI, 1.02-1.61]), as well as larger MCA-M1 diameters with vascular death (aHR, 1.84 [95% CI, 1.02-3.31]). Larger MCA-M1 and BA diameters did not correlate with incident stroke. However, larger BA diameters were associated with posterior circulation noncardioembolic stroke (aHR, 2.93 [95% CI, 1.07-8.04]). There were no statistical interactions between brain arterial lengths and diameters in relation to study outcomes.

CONCLUSIONS

In a multiethnic cohort of stroke-free adults, brain arterial elongation did not correlate with risk of stroke or death, nor influenced the significant association between brain arterial dilation and vascular risk.

Septal E/e' Ratio Is Associated With Cerebral White Matter Hyperintensity Progression in Young-Old Hypertensive Patients

Background: The incidence of hypertension increases with age, as does that of brain abnormalities associated with cerebral pathologic and functional degeneration. Little is known about the relationship between hypertension-related cardiac changes and cerebral pathologic degeneration. We examined the relationship between left ventricular (LV) diastolic dysfunction and cerebral white matter hyperintensity (WMH) progression in young-old hypertensive patients. Methods and Results: This single-center prospective longitudinal observational study included 156 individuals aged 65-75 years with well-controlled hypertension, normal LV contraction, and no history of symptomatic heart failure. WMH was quantified on brain magnetic resonance imaging (MRI). The primary outcome was the rate of WMH volume progression between the baseline and follow-up MRI (∆WMH). Participants were classified into tertiles on the basis of ∆WMH (small, medium, and large ∆WMH). The mean (±SD) age at recruitment was 69.6±2.8 years, and the mean follow-up period was 4.6 years. The ratio of early diastolic mitral inflow velocity to early diastolic septal mitral annulus velocity (septal E/e') was significantly higher in the large ∆WMH group than in the small and medium ∆WMH groups. On multiple regression analysis, septal E/e' was significantly positively associated with square-root-transformed ∆WMH (β=0.457, P<0.001). Conclusions: Septal E/e' was significantly positively associated with the rate of progression of WMH volume, suggesting that LV diastolic dysfunction is associated with the progression of abnormal brain aging.

Willis Lecture: Biomarkers for Inflammatory White Matter Injury in Binswanger Disease Provide Pathways to Precision Medicine

Binswanger disease is the small vessel form of vascular cognitive impairment and dementia. Deposition of Alzheimer disease proteins can begin in midlife and progress slowly, whereas aging of the vasculature also can begin in midlife, continuing to progress into old age, making mixed dementia the most common type of dementia. Biomarkers facilitate the early diagnosis of dementias. It is possible to diagnose mixed dementia before autopsy with biomarkers for vascular disease derived from diffusor tensor images on magnetic resonance imaging and Alzheimer disease proteins, Aβ (amyloid β), and phosphorylated tau, in cerebrospinal fluid or in brain with positron emission tomography. The presence of vascular disease accelerates cognitive decline. Both misfolded proteins and vascular disease promote inflammation, which can be detected in cerebrospinal fluid by the presence of MMPs (matrix metalloproteinases), angiogenic growth factors, and cytokines. MMPs disrupt the blood-brain barrier and break down myelin, producing Binswanger disease's 2 main pathological features. Advances in detecting biomarkers in plasma will provide early detection of dementia and aided by machine learning and artificial intelligence, will enhance diagnosis and form the basis for early treatments.

Vascular dementia: A microglia's perspective

Vascular dementia (VaD) is a second most common form of age-related dementia. It is characterized by cognitive impairment associated with vascular pathology, symptoms mainly caused by cerebral damage due to inadequate blood flow to the brain. The pathogenesis of VaD is complex, and a growing body of literature emphasizes on the involvement of microglia in disease development and progression. Here, we review the current knowledge on the role of microglia in regulating neuroinflammation under the pathogenesis of VaD. The commonly used animal and cell models for understanding the disease pathogenesis were summarized. The mechanisms by which microglia contribute to VaD are multifactorial, and we specifically focus on some of the predominant functions of microglia, including chemotaxis, secretory property, phagocytosis, and its crosstalk with other neurovascular unit cells. Finally, potential therapeutic strategies targeting microglia-modulated neuroinflammation are discussed.

The emerging role of furin in neurodegenerative and neuropsychiatric diseases

Furin is an important mammalian proprotein convertase that catalyzes the proteolytic maturation of a variety of prohormones and proproteins in the secretory pathway. In the brain, the substrates of furin include the proproteins of growth factors, receptors and enzymes. Emerging evidence, such as reduced FURIN mRNA expression in the brains of Alzheimer's disease patients or schizophrenia patients, has implicated a crucial role of furin in the pathophysiology of neurodegenerative and neuropsychiatric diseases. Currently, compared to cancer and infectious diseases, the aberrant expression of furin and its pharmaceutical potentials in neurological diseases remain poorly understood. In this article, we provide an overview on the physiological roles of furin and its substrates in the brain, summarize the deregulation of furin expression and its effects in neurodegenerative and neuropsychiatric disorders, and discuss the implications and current approaches that target furin for therapeutic interventions. This review may expedite future studies to clarify the molecular mechanisms of furin deregulation and involvement in the pathogenesis of neurodegenerative and neuropsychiatric diseases, and to develop new diagnosis and treatment strategies for these diseases.

Small Vessel Disease: Ancient Description, Novel Biomarkers

Small vessel disease (SVD) is one of the most frequent pathological conditions which lead to dementia. Biochemical and neuroimaging might help correctly identify the clinical diagnosis of this relevant brain disease. The microvascular alterations which underlie SVD have common origins, similar cognitive outcomes, and common vascular risk factors. Nevertheless, the arteriolosclerosis process, which underlines SVD development, is based on different mechanisms, not all completely understood, which start from a chronic hypoperfusion state and pass through a chronic brain inflammatory condition, inducing a significant endothelium activation and a consequent tissue remodeling action. In a recent review, we focused on the pathophysiology of SVD, which is complex, involving genetic conditions and different co-morbidities (i.e., diabetes, chronic hypoxia condition, and obesity). Currently, many points still remain unclear and discordant. In this paper, we wanted to focus on new biomarkers, which can be the expression of the endothelial dysfunction, or of the oxidative damage, which could be employed as markers of disease progression or for future targets of therapies. Therefore, we described the altered response to the endothelium-derived nitric oxide-vasodilators (ENOV), prostacyclin, C-reactive proteins, and endothelium-derived hyperpolarizing factors (EDHF). At the same time, due to the concomitant endothelial activation and chronic neuroinflammatory status, we described hypoxia-endothelial-related markers, such as HIF 1 alpha, VEGFR2, and neuroglobin, and MMPs. We also described blood–brain barrier disruption biomarkers and imaging techniques, which can also describe perivascular spaces enlargement and dysfunction. More studies should be necessary, in order to implement these results and give them a clinical benefit.

Inflammation and Rho-Associated Protein Kinase-Induced Brain Changes in Vascular Dementia

Patients with vascular dementia, caused by cerebral ischemia, experience long-term cognitive impairment due to the lack of effective treatment. The mechanisms of and treatments for vascular dementia have been investigated in various animal models; however, the insufficient information on gene expression changes that define pathological conditions hampers progress. To investigate the underlying mechanism of and facilitate treatment development for vascular dementia, we established a mouse model of chronic cerebral hypoperfusion, including bilateral carotid artery stenosis, by using microcoils, and elucidated the molecular pathway underlying vascular dementia development. Rho-associated protein kinase (ROCK) 1/2, which regulates cellular structure, and inflammatory cytokines (IL-1 and IL-6) were upregulated in the vascular dementia model. However, expression of claudin-5, which maintains the blood–brain barrier, and MAP2 as a nerve cell-specific factor, was decreased in the hippocampal region of the vascular dementia model. Thus, we revealed that ROCK pathway activation loosens the tight junction of the blood–brain barrier and increases the influx of inflammatory cytokines into the hippocampal region, leading to neuronal death and causing cognitive and emotional dysfunction. Our vascular dementia model allows effective study of the vascular dementia mechanism. Moreover, the ROCK pathway may be a target for vascular dementia treatment development in the future.

Resolving inflammatory links between myocardial infarction and vascular dementia

Myocardial infarction is associated with increased risk for vascular dementia. In both myocardial infarction and vascular dementia, there is evidence that elevated inflammatory biomarkers are associated with worsened clinical outcomes. Myocardial infarction leads to a systemic inflammatory response, which may contribute to recruitment or activation of myeloid cells, including monocytes, microglia, and perivascular macrophages, within the central nervous system. However, our understanding of the causative roles for these cells linking cardiac injury to the development and progression of dementia is incomplete. Herein, we provide an overview of inflammatory cellular and molecular links between myocardial infarction and vascular dementia and discuss strategies to resolve inflammation after myocardial infarction to limit neurovascular injury.

Metalloproteinases and their inhibitors in neurological disease

Matrix metalloproteinases (MMPs) are a group of endopeptidases that degrade the extracellular matrix and are responsible for many physiological and pathological processes. We aim to review the MMP inhibition from a clinical perspective and its possible therapeutic use in the future. MMPs play a role in various neurodegenerative and cerebrovascular diseases such as large artery atherosclerosis and ischemic stroke; for example, MMPs increase blood-brain barrier permeability favoring neuroinflammation. Synthetic MMPs inhibitors have been tested mostly in oncological trials and failed to demonstrate efficacy; some of them were discontinued because of the severe adverse reactions. Tetracyclines, in submicrobial doses, act as an MMP inhibitor, although tetracyclines have not yet been proven effective in several neurological conditions in which they were tested against placebo; it is uncertain whether there may be a use for tetracyclines in cerebrovascular disease, as a neuroprotective agent or in dolichoectasia.

Dynamics of biomarkers across the stages of traumatic spinal cord injury - implications for neural plasticity and repair

BACKGROUND

Traumatic spinal cord injury (SCI) is a complex medical condition causing significant physical disability and psychological distress. While the adult spinal cord is characterized by poor regenerative potential, some recovery of neurological function is still possible through activation of neural plasticity mechanisms. We still have limited knowledge about the activation of these mechanisms in the different stages after human SCI.

OBJECTIVE

In this review, we discuss the potential role of biomarkers of SCI as indicators of the plasticity mechanisms at work during the different phases of SCI.

METHODS

An extensive review of literature related to SCI pathophysiology, neural plasticity and humoral biomarkers was conducted by consulting the PubMed database. Research and review articles from SCI animal models and SCI clinical trials published in English until January 2021 were reviewed. The selection of candidates for humoral biomarkers of plasticity after SCI was based on the following criteria: 1) strong evidence supporting involvement in neural plasticity (mandatory); 2) evidence supporting altered expression after SCI (optional).

RESULTS

Based on selected findings, we identified two main groups of potential humoral biomarkers of neural plasticity after SCI: 1) neurotrophic factors including: Brain derived neurotrophic factor (BDNF), Nerve growth factor (NGF), Neurotrofin-3 (NT-3), and Insulin-like growth factor 1 (IGF-1); 2) other factors including: Tumor necrosis factor-alpha (TNF-α), Matrix Metalloproteinases (MMPs), and MicroRNAs (miRNAs). Plasticity changes associated with these biomarkers often can be both adaptive (promoting functional improvement) and maladaptive. This dual role seems to be influenced by their concentrations and time-window during SCI.

CONCLUSIONS

Further studies of dynamics of biomarkers across the stages of SCI are necessary to elucidate the way in which they reflect the remodeling of neural pathways. A better knowledge about the mechanisms underlying plasticity could guide the selection of more appropriate therapeutic strategies to enhance positive spinal network reorganization.

Brevican and Neurocan Peptides as Potential Cerebrospinal Fluid Biomarkers for Differentiation Between Vascular Dementia and Alzheimer's Disease

BACKGROUND

Brevican and neurocan are central nervous system-specific extracellular matrix proteoglycans. They are degraded by extracellular enzymes, such as metalloproteinases. However, their degradation profile is largely unexplored in cerebrospinal fluid (CSF).

OBJECTIVE

The study aim was to quantify proteolytic peptides derived from brevican and neurocan in human CSF of patients with Alzheimer's disease (AD) and vascular dementia (VaD) compared with controls.

METHODS

The first cohort consisted of 75 individuals including 25 patients with AD, 7 with mild cognitive impairment (MCI) diagnosed with AD upon follow-up, 10 patients with VaD or MCI diagnosed with VaD upon follow-up, and 33 healthy controls and cognitively stable MCI patients. In the second cohort, 31 individuals were included (5 AD patients, 14 VaD patients and 12 healthy controls). Twenty proteolytic peptides derived from brevican (n = 9) and neurocan (n = 11) were quantified using high-resolution parallel reaction monitoring mass spectrometry.

RESULTS

In the first cohort, the majority of CSF concentrations of brevican and neurocan peptides were significantly decreased inVaDas compared withADpatients (AUC = 0.83.0.93, p≤0.05) and as compared with the control group (AUC = 0.79.0.87, p ≤ 0.05). In the second cohort, CSF concentrations of two brevican peptides (B87, B156) were significantly decreased in VaD compared with AD (AUC = 0.86.0.91, p ≤ 0.05) and to controls (AUC = 0.80.0.82, p ≤ 0.05), while other brevican and neurocan peptides showed a clear trend to be decreased in VaD compared with AD (AUC = 0.64.80, p > 0.05). No peptides differed between AD and controls.

CONCLUSION

Brevican and neurocan peptides are potential diagnostic biomarkers for VaD, with ability to separate VaD from AD.

The Roles of Nitric Oxide Synthase/Nitric Oxide Pathway in the Pathology of Vascular Dementia and Related Therapeutic Approaches

Vascular dementia (VaD) is the second most common form of dementia worldwide. It is caused by cerebrovascular disease, and patients often show severe impairments of advanced cognitive abilities. Nitric oxide synthase (NOS) and nitric oxide (NO) play vital roles in the pathogenesis of VaD. The functions of NO are determined by its concentration and bioavailability, which are regulated by NOS activity. The activities of different NOS subtypes in the brain are partitioned. Pathologically, endothelial NOS is inactivated, which causes insufficient NO production and aggravates oxidative stress before inducing cerebrovascular endothelial dysfunction, while neuronal NOS is overactive and can produce excessive NO to cause neurotoxicity. Meanwhile, inflammation stimulates the massive expression of inducible NOS, which also produces excessive NO and then induces neuroinflammation. The vicious circle of these kinds of damage having impacts on each other finally leads to VaD. This review summarizes the roles of the NOS/NO pathway in the pathology of VaD and also proposes some potential therapeutic methods that target this pathway in the hope of inspiring novel ideas for VaD therapeutic approaches.

Plasma osteopontin as a biomarker of Alzheimer's disease and vascular cognitive impairment

Cerebrovascular disease (CeVD) and neurodegenerative dementia such as Alzheimer’s disease (AD) are frequently associated comorbidities in the elderly, sharing common risk factors and pathophysiological mechanisms including neuroinflammation. Osteopontin (OPN) is an inflammatory marker found upregulated in vascular diseases as well as in AD. However, its involvement in vascular dementia (VaD) and pre-dementia stages, namely cognitive impairment no dementia (CIND), both of which fall under the spectrum of vascular cognitive impairment (VCI), has yet to be examined. Its correlations with inflammatory cytokines in cognitive impairment also await investigation. 80 subjects with no cognitive impairment (NCI), 160 with CIND and 144 with dementia were included in a cross-sectional study on a Singapore-based memory clinic cohort. All subjects underwent comprehensive clinical, neuropsychological and brain neuroimaging assessments, together with clinical diagnoses based on established criteria. Blood samples were collected and OPN as well as inflammatory cytokines interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF) were measured using immunoassays. Multivariate regression analyses showed significant associations between increased OPN and VCI groups, namely CIND with CeVD, AD with CeVD and VaD. Interestingly, higher OPN was also significantly associated with AD even in the absence of CeVD. We further showed that increased OPN significantly associated with neuroimaging markers of CeVD and neurodegeneration, including cortical infarcts, lacunes, white matter hyperintensities and brain atrophy. OPN also correlated with elevated levels of IL-6, IL-8 and TNF. Our findings suggest that OPN may play a role in both VCI and neurodegenerative dementias. Further longitudinal analyses are needed to assess the prognostic utility of OPN in disease prediction and monitoring.

A new role for matrix metalloproteinase-3 in the NGF metabolic pathway: Proteolysis of mature NGF and sex-specific differences in the continuum of Alzheimer's pathology

Matrix metalloproteinase-3 (MMP-3) has been associated with risk of Alzheimer's disease (AD). In this study we introduce a novel role for MMP-3 in degrading nerve growth factor (NGF) in vivo and examine its mRNA and protein expression across the continuum of AD pathology. We provide evidence that MMP-3 participates in the degradation of mature NGF in vitro and in vivo and that it is secreted from the rat cerebral cortex in an activity-dependent manner. We show that cortical MMP-3 is upregulated in the McGill-R-Thy1-APP transgenic rat model of AD-like amyloidosis. A similar upregulation was found in AD and MCI brains as well as in cognitively normal individuals with elevated amyloid deposition. We also observed that frontal cortex MMP-3 protein levels are higher in males. MMP-3 protein correlated with more AD neuropathology, markers of NGF metabolism, and lower cognitive scores in males but not in females. These results suggest that MMP-3 upregulation in AD might contribute to NGF dysmetabolism, and therefore to cholinergic atrophy and cognitive deficits, in a sex-specific manner. MMP-3 should be further investigated as a biomarker candidate or as a therapeutic target in AD.

Pathophysiology of Blood-Brain Barrier Permeability Throughout the Different Stages of Ischemic Stroke and Its Implication on Hemorrhagic Transformation and Recovery

The blood-brain barrier (BBB) is a dynamic interface responsible for maintaining the central nervous system homeostasis. Its unique characteristics allow protecting the brain from unwanted compounds, but its impairment is involved in a vast number of pathological conditions. Disruption of the BBB and increase in its permeability are key in the development of several neurological diseases and have been extensively studied in stroke. Ischemic stroke is the most prevalent type of stroke and is characterized by a myriad of pathological events triggered by an arterial occlusion that can eventually lead to fatal outcomes such as hemorrhagic transformation (HT). BBB permeability seems to follow a multiphasic pattern throughout the different stroke stages that have been associated with distinct biological substrates. In the hyperacute stage, sudden hypoxia damages the BBB, leading to cytotoxic edema and increased permeability; in the acute stage, the neuroinflammatory response aggravates the BBB injury, leading to higher permeability and a consequent risk of HT that can be motivated by reperfusion therapy; in the subacute stage (1-3 weeks), repair mechanisms take place, especially neoangiogenesis. Immature vessels show leaky BBB, but this permeability has been associated with improved clinical recovery. In the chronic stage (>6 weeks), an increase of BBB restoration factors leads the barrier to start decreasing its permeability. Nonetheless, permeability will persist to some degree several weeks after injury. Understanding the mechanisms behind BBB dysregulation and HT pathophysiology could potentially help guide acute stroke care decisions and the development of new therapeutic targets; however, effective translation into clinical practice is still lacking. In this review, we will address the different pathological and physiological repair mechanisms involved in BBB permeability through the different stages of ischemic stroke and their role in the development of HT and stroke recovery.

Correlation Between Internal Carotid Artery Tortuosity and Imaging of Cerebral Small Vessel Disease

Background and Purpose: An association between artery tortuosity and neuroimaging of cerebral small vessel disease (SVD) has been reported, especially in the posterior circulation. However, few studies involved the whole magnetic resonance imaging (MRI) spectrum of SVD in association with anterior circulation arterial tortuosity. This study aimed to investigate the relationship between internal carotid artery (ICA) tortuosity and the neuroimaging of SVD.

Methods: Data of 1,264 consecutive patients in whom cerebral vessel diseases were suspected and who underwent both MRI and computed tomography angiography were reviewed from a prospective registry. Internal carotid artery tortuosity was evaluated using the tortuosity index (TI), which was defined as the ratio of the vessel centerline length divided by the straight length. Magnetic resonance imaging was used to assess cerebral microbleeds (CMBs), white matter hyperintensities (WMHs), enlarged perivascular spaces (EPVSs), and lacunes.

Results: The TIs of the ICA for patients with and without SVD MRI markers were 1.81 ± 0.42 and 1.72 ± 0.33, respectively (P < 0.001). Univariate analysis showed that the ICA TI were positively correlated with each SVD MRI marker (P < 0.001), and the correlation coefficients (r_s) were 0.57, 0.42, 0.30, and 0.26 for EPVSs, WMHs, CMBs, and lacunes, respectively. The adjusted ORs of the ICA TI were 1.52 (95% CI 1.44–1.60, P < 0.001) for EPVS grade 1, 2.05 (95% CI 1.93–2.18, P < 0.001) for EPVS grades 2–4, and 1.09 (95% CI 1.03–1.15, P = 0.004) for WMH grade 3.

Conclusions: The TI of ICA was higher in patients with neuroimaging of SVD. Internal carotid arteries tortuosity was associated with MRI-defined markers of SVD, including EPVS and high-grade WMH, and positively correlated with EPVS severity. Arterial tortuosity might be a risk factor for SVD. This finding may have potential clinical significance for identifying patients with suspected SVD.

Echocardiographic index E/e' in association with cerebral white matter hyperintensity progression

Cerebral white-matter hyperintensities (WMHs) on MRI is associated with reduced compliance of the cerebral arterioles. We hypothesized that an echocardiography index for left ventricular (LV) diastolic function, E/e', might reflect the cerebral arteriolar compliance and evaluated the association between E/e' and long-term progression rate of the cerebral WMH volume. This retrospective study included individuals who were ≥ 50 years of age, with a preserved LV ejection fraction (≥ 50%) and neurological function status (modified Rankin scale score ≤1), and underwent initial and follow-up MRI evaluations within intervals of 34-45 months. Baseline clinical, laboratory, and echocardiography markers such as ejection fraction, LV mass index, and E/e' were obtained. WMH volume progression rate between the baseline and follow-up MRIs was designated as the outcome factor. 392 individuals (57.1% men; mean age: 66.7±8.4 years) were followed-up for 38.2±3.4 months. The mean WMH volume progression rate was 1.35±2.65 mL/year. The log-transformed value of WMH volume progression rate was linearly associated with the log-transformed E/e' (B coefficient = 0.365; 95% confidence interval [CI] 0.180-0.551; P = 0.001), along with the log-transformed values of baseline WMH volume (B = 0.142; 95% CI 0.106-0.179; P<0.001) and glomerular filtration rate (B = -0.182; 95% CI -0.321-0.044; P = 0.010). Additionally, a subgroup with an E/e' ≥15 exhibited a significantly higher WMH progression rate compared to the subgroups with lower E/e' values (P<0.001), especially in the lower quartiles (quartiles 1 and 2) of the baseline WMH volume. We concluded that echocardiographic marker E/e' is associated with the long-term progression rate of cerebral WMHs in population with preserved LV systolic function.

Optical coherence tomography-based assessment of retinal vascular pathology in cerebral small vessel disease

Background

Cerebral small vessel disease (CSVD) is a disorder of brain vasculature that causes various structural changes in the brain parenchyma, and is associated with various clinical symptoms such as cognitive impairment and gait disorders. Structural changes of brain arterioles cannot be visualized with routine imaging techniques in vivo. However, optical coherence tomography (OCT) is thought to be a “window to the brain”. Thus, retinal vessel parameters may correlate with CSVD characteristic brain lesions and cerebrospinal fluid biomarkers (CSF) of the neuropathological processes in CSVD like endothelial damage, microglial activation and neuroaxonal damage.

Methods

We applied OCT-based assessment of retinal vessels, magnetic resonance imaging (MRI), and CSF biomarker analysis in a monocentric prospective cohort of 24 patients with sporadic CSVD related stroke and cognitive impairment. MRI lesions were defined according to the STandards for ReportIng Vascular changes on nEuroimaging (STRIVE). Biomarkers were assessed using commercially available ELISA kits. Owing to the unavailability of an age-matched control-group lacking MRI-characteristics of CSVD, we compared the retinal vessel parameters in CSVD patients (73.8 ± 8.5 years) with a younger group of healthy controls (51.0 ± 16.0 years) by using an age- and sex-adjusted multiple linear regression analysis model.

Results

Among the parameters measured with OCT, the Wall to Lumen Ratio (WLR) but not Mean Wall Thickness (MWT) of the superior branch of the retinal artery correlated significantly with the volume of white matter hyperintensities on MRI (r_s = − 0.5) and with CSF-levels of Chitinase 3 like 1 protein (r_s = − 0.6), zona occludens 1 protein (r_s = − 0.5) and GFAP (r_s = − 0.4). MWT and WLR were higher in CSVD than in controls (28.9 μm vs. 23.9 μm, p = 0.001 and 0.32 vs. 0.25, p = 0.001).

Conclusions

In this exploratory study, WLR correlated with the volume of white matter hyperintensities, and markers of vascular integrity, microglial activation, and neuroaxonal damage in CSVD. Further prospective studies should clarify whether retinal vessel parameters and CSF biomarkers may serve to monitor the natural course and treatment effects in clinical studies on CSVD.

Review of Alterations in Perlecan-Associated Vascular Risk Factors in Dementia

Perlecan is a heparan sulfate proteoglycan protein in the extracellular matrix that structurally and biochemically supports the cerebrovasculature by dynamically responding to changes in cerebral blood flow. These changes in perlecan expression seem to be contradictory, ranging from neuroprotective and angiogenic to thrombotic and linked to lipid retention. This review investigates perlecan's influence on risk factors such as diabetes, hypertension, and amyloid that effect Vascular contributions to Cognitive Impairment and Dementia (VCID). VCID, a comorbidity with diverse etiology in sporadic Alzheimer's disease (AD), is thought to be a major factor that drives the overall clinical burden of dementia. Accordingly, changes in perlecan expression and distribution in response to VCID appears to be injury, risk factor, location, sex, age, and perlecan domain dependent. While great effort has been made to understand the role of perlecan in VCID, additional studies are needed to increase our understanding of perlecan's role in health and in cerebrovascular disease.

Oxygenation differs among white matter hyperintensities, intersected fiber tracts and unaffected white matter

White matter hyperintensities of presumed vascular origin are frequently observed on magnetic resonance imaging in normal aging. They are typically found in cerebral small vessel disease and suspected culprits in the etiology of complex age- and small vessel disease-related conditions, such as late-onset depression. White matter hyperintensities may interfere with surrounding white matter metabolic demands by disrupting fiber tract integrity. Meanwhile, risk factors for small vessel disease are thought to reduce tissue oxygenation, not only by reducing regional blood supply, but also by impairing capillary function. To address white matter oxygen supply–demand balance, we estimated voxel-wise capillary density as an index of resting white matter metabolism, and combined estimates of blood supply and capillary function to calculate white matter oxygen availability. We conducted a cross-sectional study with structural, perfusion- and diffusion-weighted magnetic resonance imaging in 21 patients with late-onset depression and 21 controls. We outlined white matter hyperintensities and used tractography to identify the tracts they intersect. Perfusion data comprised cerebral blood flow, blood volume, mean transit time and relative transit time heterogeneity—the latter a marker of capillary dysfunction. Based on these, white matter oxygenation was calculated as the steady state cerebral metabolic rate of oxygen under the assumption of normal tissue oxygen tension and vice versa. The number, volume and perfusion characteristics of white matter hyperintensities did not differ significantly between groups. Hemodynamic data showed white matter hyperintensities to have lower blood flow and blood volume, but higher relative transit time heterogeneity, than normal-appearing white matter, resulting in either reduced capillary metabolic rate of oxygen or oxygen tension. Intersected tracts showed significantly lower blood flow, blood volume and capillary metabolic rate of oxygen than normal-appearing white matter. Across groups, lower lesion oxygen tension was associated with higher lesion number and volume. Compared with normal-appearing white matter, tissue oxygenation is significantly reduced in white matter hyperintensities as well as the fiber tracts they intersect, independent of parallel late-onset depression. In white matter hyperintensities, reduced microvascular blood volume and concomitant capillary dysfunction indicate a severe oxygen supply–demand imbalance with hypoxic tissue injury. In intersected fiber tracts, parallel reductions in oxygenation and microvascular blood volume are consistent with adaptations to reduced metabolic demands. We speculate, that aging and vascular risk factors impair white matter hyperintensity perfusion and capillary function to create hypoxic tissue injury, which in turn affect the function and metabolic demands of the white matter tracts they disrupt.

Heterogeneity of microglia and their differential roles in white matter pathology

Microglia are resident immune cells that play multiple roles in central nervous system (CNS) development and disease. Although the classical concept of microglia/macrophage activation is based on a biphasic beneficial‐versus‐deleterious polarization, growing evidence now suggests a much more heterogenous profile of microglial activation that underlie their complex roles in the CNS. To date, the majority of data are focused on microglia in gray matter. However, demyelination is a prominent pathologic finding in a wide range of diseases including multiple sclerosis, Alzheimer's disease, and vascular cognitive impairment and dementia. In this mini‐review, we discuss newly discovered functional subsets of microglia that contribute to white matter response in CNS disease onset and progression. Microglia show different molecular patterns and morphologies depending on disease type and brain region, especially in white matter. Moreover, in later stages of disease, microglia demonstrate unconventional immuno‐regulatory activities such as increased phagocytosis of myelin debris and secretion of trophic factors that stimulate oligodendrocyte lineage cells to facilitate remyelination and disease resolution. Further investigations of these multiple microglia subsets may lead to novel therapeutic approaches to treat white matter pathology in CNS injury and disease.

Spectral Diffusion Analysis of Intravoxel Incoherent Motion MRI in Cerebral Small Vessel Disease

Background

Cerebral intravoxel incoherent motion (IVIM) imaging assumes two components. However, more compartments are likely present in pathologic tissue. We hypothesized that spectral analysis using a nonnegative least‐squares (NNLS) approach can detect an additional, intermediate diffusion component, distinct from the parenchymal and microvascular components, in lesion‐prone regions.

Purpose

To investigate the presence of this intermediate diffusion component and its relation with cerebral small vessel disease (cSVD)‐related lesions.

Study Type

Prospective cross‐sectional study.

Population

Patients with cSVD (n = 69, median age 69.8) and controls (n = 39, median age 68.9).

Field Strength/Sequence

Whole‐brain inversion recovery IVIM acquisition at 3.0T.

Assessment

Enlarged perivascular spaces (PVS) were rated by three raters. White matter hyperintensities (WMH) were identified on a fluid attenuated inversion recovery (FLAIR) image using a semiautomated algorithm.

Statistical Tests

Relations between IVIM measures and cSVD‐related lesions were studied using the Spearman's rank order correlation.

Results

NNLS yielded diffusion spectra from which the intermediate volume fraction f_int was apparent between parenchymal diffusion and microvasular pseudodiffusion. WMH volume and the extent of MRI‐visible enlarged PVS in the basal ganglia (BG) and centrum semiovale (CSO) were correlated with f_int in the WMHs, BG, and CSO, respectively. f_int was 4.2 ± 1.7%, 7.0 ± 4.1% and 13.6 ± 7.7% in BG and 3.9 ± 1.3%, 4.4 ± 1.4% and 4.5 ± 1.2% in CSO for the groups with low, moderate, and high number of enlarged PVS, respectively, and increased with the extent of enlarged PVS (BG: r = 0.49, P < 0.01; CSO: r = 0.23, P = 0.02). f_int in the WMHs was 27.1 ± 13.1%, and increased with the WMH volume (r = 0.57, P < 0.01).

Data Conclusion

We revealed the presence of an intermediate diffusion component in lesion‐prone regions of cSVD and demonstrated its relation with enlarged PVS and WMHs. In tissue with these lesions, tissue degeneration or perivascular edema can lead to more freely diffusing interstitial fluid contributing to f_int.

Level of Evidence: 2

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2020;51:1170–1180.

Basilar Artery Tortuosity Is Associated With White Matter Hyperintensities by TIMP-1

Background and Purpose

To test the hypothesis that the imbalance between matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) may play a potential role in bridging vertebrobasilar dolichoectasia (VBD) with lacunar infarction (LI) and white matter hyperintensities (WMH).

Methods

We studied 212 patients with vertigo who underwent multimodal magnetic resonance imaging (MRI) tests for VBD, LI, and WMH identification. We investigated biomarkers of VBD with magnetic resonance angiography (MRA) via various physical characteristics of the vertebrobasilar arteries (VBAs). Similarly, LI and WMH biomarkers were extracted using T2-weighted and fluid attenuated inversion recovery (FLAIR) images. We first determined which of these neuroimaging markers were significant identifiers of VBD, LI and the different grades of WMH. We then sought to draw potential mechanistic conclusions from these MRI-derived parameters, by associating the aforementioned biomarkers with MMP and TIMP serum levels in patient blood samples using non-parametric statistical tests.

Results

MMP-9 serum level was significantly higher in vertigo patients with VBAs dilation and basilar artery (BA) elongation compared to those with healthy arterial size, and the ratio of MMP-9/TIMP-1 level were higher in those patients. TIMP-1 level was also markedly higher in vertigo patients with BA tortuosity than those without BA tortuosity. The bending length (BL) of the BA was positively correlated with TIMP-1. The length, BL, and tortuosity index of the BA, as well as serum levels of TIMP-1 were greater in patients with higher WMH grades compared to those with low WMH grades. The vertebral artery and BA diameters, and the levels of MMP-2, -3, -9, TIMP-2 and cathepsin L were similar in patients with different WMH grades.

Conclusion

In vertigo patients, we found various probably associations between MMP-9 and TIMP-1 with arterial alterations linked to both VBD and WMH that may help with the diagnosis and treatment of such diseases in the future.

Multiple biomarkers covering several pathways improve predictive ability for cognitive impairment among ischemic stroke patients with elevated blood pressure

BACKGROUND AND AIMS

We aimed to evaluate the ability of multiple novel biomarkers representing several pathophysiological pathways to improve risk prediction of post-stroke cognitive impairment.

METHODS

We conducted a prospective multicenter study in 638 ischemic stroke patients with elevated blood pressure based on a random subsample from China Antihypertensive Trial in Acute Ischemic Stroke and measured 12 circulating biomarkers in these participants. Cognitive impairment was assessed at 3 months after stroke with definitions of Mini-Mental State Examination (MMSE) score <27 or Montreal Cognitive Assessment (MoCA) score <25.

RESULTS

According to MMSE score, 1 SD increase of rheumatoid factor (odds ratio [OR] 1.22, 95% confidence interval [CI] 1.02-1.46), matrix metalloproteinase-9 (OR 1.47, 95% CI 1.22-1.77) and total homocysteine (OR 1.22, 95% CI 1.01-1.49) after log transformation was significantly associated with the risk of post-stroke cognitive impairment. The ORs associated with their simultaneously high levels were 4.89 (95% CI, 2.31-10.35; p_trend<0.001) and 3.09 (95% CI, 1.60-5.98; p_trend<0.001) for cognitive impairment and the severity of cognitive impairment, respectively. Adding these 3 biomarkers to conventional model significantly improved the risk prediction of cognitive impairment (C statistic 0.729 vs. 0.688, p = 0.004; net reclassification improvement = 33.67%, p < 0.001; integrated discrimination index = 4.61%; p < 0.001). Similar significant findings were observed when cognitive impairment was defined by MoCA score.

CONCLUSIONS

Combination of rheumatoid factor, matrix metalloproteinase-9 and total homocysteine can improve the risk prediction of cognitive impairment among ischemic stroke patients with elevated blood pressure. Further studies are warranted to validate our findings and explore their roles as potential therapeutic targets.

Blood-brain barrier impairment and hypoperfusion are linked in cerebral small vessel disease

OBJECTIVE

To investigate the link between blood-brain-barrier (BBB) permeability and cerebral blood flow (CBF) and the relation with white matter hyperintensities (WMH) in cerebral small vessel disease (cSVD).

METHODS

Twenty-seven patients with cSVD received dynamic susceptibility contrast and dynamic contrast-enhanced MRI to determine CBF and BBB permeability (expressed as leakage rate and volume), respectively. Structural MRI were segmented into normal-appearing white matter (NAWM) and WMH, for which a perilesional zone was defined. In these regions, we investigated the BBB permeability, CBF, and their relation using Pearson correlation r.

RESULTS

We found a decrease in CBF of 2.2 mL/min/100 g (p < 0.01) and an increase in leakage volume of 0.7% (p < 0.01) per mm closer to the WMH in the perilesional zones. Lower CBF values correlated with higher leakage measures in the NAWM and WMH (-0.53 < r < -0.40, p < 0.05). This relation was also observed in the perilesional zones, which became stronger in the proximity of WMH (p = 0.03).

CONCLUSION

BBB impairment and hypoperfusion appear in the WMH and NAWM, which increase in the proximity of the WMH, and are linked. Both BBB and CBF are regulated in the neurovascular unit (NVU) and the observed link might be due to the physiologic regulation mechanism of the NVU. This link may suggest an early overall deterioration of this unit.

Small Vessel Disease Is Associated with Tissue Inhibitor of Matrix Metalloproteinase-4 After Ischaemic Stroke

Small vessel disease (SVD) is frequent in aging and stroke patients. Inflammation and remodeling of extracellular matrix have been suggested as concurrent mechanisms of SVD. We investigated the relationship between imaging features of SVD and circulating metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in patients with ischaemic stroke. In patients treated with intravenous thrombolysis, we took blood samples before intravenous thrombolysis and 90 days after the acute stroke and analysed levels of MMPs and TIMPs. We assessed leukoaraiosis, number of lacunes and brain atrophy on pre-treatment CT scan and graded global SVD burden combining such features. We investigated associations between single features, global SVD and MMPs and TIMPs at baseline and at follow-up, retaining univariate statistically significant associations in multivariate linear regression analysis and adjusting for clinical confounders. A total of 255 patients [mean (±SD) = 68.6 (± 12.7) years, 154 (59%) males] were included, 107 (42%) had no signs of SVD; 47 (19%) had from moderate to severe SVD burden. A total of 107 (42%) patients had no signs of SVD; 47 (19%) had from moderate to severe SVD burden. After adjustment, only TIMP-4 proved associations with SVD features. Brain atrophy was associated with baseline TIMP-4 (β = 0.20;p = 0.019) and leukoaraiosis with 90 days TIMP-4 (β = 0.19; p = 0.013). Global SVD score was not associated with baseline TIMP-4 levels (β = 0.10; p = 0.072), whereas was associated with 90 days TIMP-4 levels (β = 0.21; p = 0.003). Total SVD burden was associated with higher TIMP-4 levels 90 days after stroke, whereas was not during the acute phase. Our results support a biological relationship between SVD grade and TIMP-4.

Cerebral small vessel disease and systemic arteriopathy in intracranial arterial dolichoectasia patients

OBJECTIVES

To investigate clinical and demographic characteristics of patients with intracranial arterial dolichoectasia (IADE) and describe the possible coexistence of cerebral small vessel disease (SVD) and systemic arteriopathy.

MATERIAL AND METHODS

From January 2015 to March 2016, all the patients attending an outpatient service for chronic cerebrovascular diseases were screened for suspected IADE. Identified patients underwent a predefined protocol including: brain MR angiography for the diagnosis of IADE; brain MRI with visual rating of SVD features; whole-body CT angiography to assess signs of systemic arteriopathy; and neuropsychological examination.

RESULTS

Among the 251 patients screened, IADE was diagnosed in seven (mean age ± SD 68.8 ± 7.2 years, six males). Hypertension was the most frequent risk factor. All patients had basilar artery dolichoectasia, two also ectasia of a vessel of the anterior circulation. All patients had white matter hyperintensities that were moderate or severe in six, five had at least one lacune, and all had enlarged perivascular spaces. At least one microbleed was detected in six patients. A variable grade of global cortical atrophy was found in six patients. Systemic arterial ectasia was found in all but one patient. Neuropsychological examination showed a multidomain cognitive impairment in five patients.

CONCLUSIONS

Our study confirms the high prevalence of cerebral SVD in IADE. The involvement of the brain-supplying arteries is probably part of a systemic arteriopathy in IADE patients, thus suggesting the usefulness of assessing the whole arterial tree in clinical practice. Cognitive deterioration signs are frequent in these patients.

MRI-based evaluation of structural degeneration in the ageing brain: Pathophysiology and assessment

Advances in MRI technology have significantly contributed to our ability to understand the process of brain ageing, allowing us to track and assess changes that occur during normal ageing and neurological conditions. This paper focuses on reviewing structural changes of the ageing brain that are commonly seen using MRI, summarizing the pathophysiology, prevalence, and neuroanatomical distribution of changes including atrophy, lacunes, white matter lesions, and dilated perivascular spaces. We also review the clinically accessible methodology for assessing these MRI-based changes, covering visual rating scales, as well computer-aided and fully automated methods. Subsequently, we consider novel assessment methods designed to evaluate changes across the whole brain, and finally discuss new directions in this field of research.

The effect of age-related risk factors and comorbidities on white matter injury and repair after ischemic stroke

White matter injury is a crucial component of human stroke, but it has often been neglected in preclinical studies. Most human stroke is associated with one or more comorbidities, including aging, hypertension, diabetes and metabolic syndrome including hyperlipidemia. The purpose of this review is to examine how age and hypertension impact stroke-induced white matter injury as well as white matter repair in both human stroke and preclinical models. It is essential that comorbidities be examined in preclinical trials as they may impact translatability to the clinic. In addition, understanding how comorbidities impact white matter injury and repair may provide new therapeutic opportunities for patients with those conditions.

Association between matrix metalloproteinase family gene polymorphisms and risk of ischemic stroke: A systematic review and meta-analysis of 29 studies

BACKGROUND

Ischemic stroke (IS) is a complex and devastating vascular disease that has become one of the leading causes of disability and mortality worldwide. Several studies have shown the association between matrix metalloproteinase (MMP) family gene polymorphisms and IS. However, the results have been indecisive.

OBJECTIVE

To investigate the association between Matrix Metalloproteinase gene polymorphisms and risk of IS.

METHODS

A literature search for eligible candidate gene studies published before, 28 June 2017, was conducted in the PubMed, EMBASE, Cochrane and Google Scholar databases. The following combinations of main keywords were used: ('Matrix Metalloproteinase' or 'MMP' or 'Stromelysin-1' or 'Gelatinase b') AND ('ischemic stroke' or 'IS') AND ('single nucleotide polymorphism' or 'gene polymorphism' or 'SNP'). Fixed or random effects models were used to estimate the Pooled Odds ratio (OR) and 95% confidence interval (CI). Statistical analysis was carried out by using STATA version 13.0 software.

RESULTS

Total 29 studies were included in our meta-analysis. A significant association was observed for MMP-9 (-1562C/T) (OR 1.27; 95% CI 1.06 to 1.53; p value = 0.01) and MMP-12 (-1082 A/G) (OR 2.55; 95% CI 1.75 to 3.71; p value<0.001) gene polymorphisms and risk of IS. No significant association was found for any of the MMP-1(-1607 1G/2G), MMP-2 (-1306C/T) & (-735C/T) and MMP-3 (-1612 5A/6A) gene polymorphisms with the risk of IS.

CONCLUSION

Our meta-analysis suggests that MMP-9 (-1562C/T) and MMP-12 (-1082 A/G) gene polymorphisms could be a risk factor for IS while MMP-1 (-1607 1G/2G), MMP-2 (-1306C/T) & (-735C/T) and MMP-3 (-1612 5A/6A) have no association with the risk of causing IS. However, large prospective studies with sufficient power are required to validate our findings.

NOS3 Inhibition Confers Post-Ischemic Protection to Young and Aging White Matter Integrity by Conserving Mitochondrial Dynamics and Miro-2 Levels

White matter (WM) damage following a stroke underlies a majority of the neurological disability that is subsequently observed. Although ischemic injury mechanisms are age-dependent, conserving axonal mitochondria provides consistent post-ischemic protection to young and aging WM. Nitric oxide synthase (NOS) activation is a major cause of oxidative and mitochondrial injury in gray matter during ischemia; therefore, we used a pure WM tract, isolated male mouse optic nerve, to investigate whether NOS inhibition provides post-ischemic functional recovery by preserving mitochondria. We show that pan-NOS inhibition applied before oxygen-glucose deprivation (OGD) promotes functional recovery of young and aging axons and preserves WM cellular architecture. This protection correlates with reduced nitric oxide (NO) generation, restored glutathione production, preserved axonal mitochondria and oligodendrocytes, and preserved ATP levels. Pan-NOS inhibition provided post-ischemic protection to only young axons, whereas selective inhibition of NOS3 conferred post-ischemic protection to both young and aging axons. Concurrently, genetic deletion of NOS3 conferred long-lasting protection to young axons against ischemia. OGD upregulated NOS3 levels in astrocytes, and we show for the first time that inhibition of NOS3 generation in glial cells prevents axonal mitochondrial fission and restores mitochondrial motility to confer protection to axons by preserving Miro-2 levels. Interestingly, NOS1 inhibition exerted post-ischemic protection selectively to aging axons, which feature age-dependent mechanisms of oxidative injury in WM. Our study provides the first evidence that inhibition of glial NOS activity confers long-lasting benefits to WM function and structure and suggests caution in defining the role of NO in cerebral ischemia at vascular and cellular levels.SIGNIFICANCE STATEMENT White matter (WM) injury during stroke is manifested as the subsequent neurological disability in surviving patients. Aging primarily impacts CNS WM and mechanisms of ischemic WM injury change with age. Nitric oxide is involved in various mitochondrial functions and we propose that inhibition of glia-specific nitric oxide synthase (NOS) isoforms promotes axon function recovery by preserving mitochondrial structure, function, integrity, and motility. Using electrophysiology and three-dimensional electron microscopy, we show that NOS3 inhibition provides a common target to improve young and aging axon function, whereas NOS1 inhibition selectively protects aging axons when applied after injury. This study provides the first evidence that inhibition of glial cell NOS activity confers long-lasting benefits to WM structure and function.

Vascular tight junction disruption and angiogenesis in spontaneously hypertensive rat with neuroinflammatory white matter injury

Vascular cognitive impairment is a major cause of dementia caused by chronic hypoxia, producing progressive damage to white matter (WM) secondary to blood-brain barrier (BBB) opening and vascular dysfunction. Tight junction proteins (TJPs), which maintain BBB integrity, are lost in acute ischemia. Although angiogenesis is critical for neurovascular remodeling, less is known about its role in chronic hypoxia. To study the impact of TJP degradation and angiogenesis during pathological progression of WM damage, we used the spontaneously hypertensive/stroke prone rats with unilateral carotid artery occlusion and Japanese permissive diet to model WM damage. MRI and IgG immunostaining showed regions with BBB damage, which corresponded with decreased endothelial TJPs, claudin-5, occludin, and ZO-1. Affected WM had increased expression of angiogenic factors, Ki67, NG2, VEGF-A, and MMP-3 in vascular endothelial cells and pericytes. To facilitate the study of angiogenesis, we treated rats with minocycline to block BBB disruption, reduce WM lesion size, and extend survival. Minocycline-treated rats showed increased VEGF-A protein, TJP formation, and oligodendrocyte proliferation. We propose that chronic hypoxia disrupts TJPs, increasing vascular permeability, and initiating angiogenesis in WM. Minocycline facilitated WM repair by reducing BBB damage and enhancing expression of TJPs and angiogenesis, ultimately preserving oligodendrocytes.

Impact of pulse pressure on cerebrovascular events leading to age-related cognitive decline

Aging is a modern concept: human life expectancy has more than doubled in less than 150 yr in Western countries. Longer life span, however, reveals age-related diseases, including cerebrovascular diseases. The vascular system is a prime target of aging: the "wear and tear" of large elastic arteries exposed to a lifelong pulsatile pressure causes arterial stiffening by fragmentation of elastin fibers and replacement by stiffer collagen. This arterial stiffening increases in return the amplitude of the pulse pressure (PP), its wave penetrating deeper into the microcirculation of low-resistance, high-flow organs such as the brain. Several studies have associated peripheral arterial stiffness responsible for the sustained increase in PP, with brain microvascular diseases such as cerebral small vessel disease, cortical gray matter thinning, white matter atrophy, and cognitive dysfunction in older individuals and prematurely in hypertensive and diabetic patients. The rarefaction of white matter is also associated with middle cerebral artery pulsatility that is strongly dependent on PP and artery stiffness. PP and brain damage are likely associated, but the sequence of mechanistic events has not been established. Elevated PP promotes endothelial dysfunction that may slowly develop in parallel with the accumulation of proinflammatory senescent cells and oxidative stress, generating cerebrovascular damage and remodeling, as well as brain structural changes. Here, we review data suggesting that age-related increased peripheral artery stiffness may promote the penetration of a high PP to cerebral microvessels, likely causing functional, structural, metabolic, and hemodynamic alterations that could ultimately promote neuronal dysfunction and cognitive decline.

Oxidative Stress Assessment in Alzheimer's Disease: A Clinic Setting Study

BACKGROUND

Oxidative stress (OS) is a physiological age-related brain process, dramatically overexpressed in neurodegenerative disorders like Alzheimer's disease (AD). Nevertheless, the pathophysiological role of OS in AD pathology has not been clarified yet. OS as a biomarker for AD is a controversial issue. A comparison of previous data is difficult due to a remarkable methodological variability. Most of the previous studies have shown higher levels of OS markers and lower antioxidant power in patients with dementia when compared to mild cognitive impairment (MCI) and healthy controls.

METHODS

We followed a strict protocol in order to limit intrasite variability of OS assessment. In addition, we have taken into account possible confounding factors.

RESULTS

In agreement with previous reports, we found both lower plasmatic OS and higher plasmatic antioxidant defenses when comparing patients with AD having dementia that is stably treated to patients with MCI-AD.

DISCUSSION

A speculative hypothesis based on correlative data is provided.

Serum Matrix Metalloproteinase-9 and Cognitive Impairment After Acute Ischemic Stroke

Background

The impact of serum matrix metalloproteinases‐9 (MMP‐9) on cognitive impairment after ischemic stroke is unclear. We aimed to investigate the association between serum MMP‐9 in the short‐term acute phase of ischemic stroke and cognitive impairment at 3 months.

Methods and Results

Our study was based on a subsample from the CATIS (China Antihypertensive Trial in Acute Ischemic Stroke); a total of 558 patients with serum MMP‐9 levels from 7 of 26 participating sites of the trial were included in this analysis. Cognitive impairment severity was categorized as severe, mild, or none (Mini‐Mental State Examination score, <23, 23–26, or ≥27, respectively; Montreal Cognitive Assessment score, <20, 20–24, or ≥25, respectively). Cognitive impairment was defined as a score of <27 for Mini‐Mental State Examination or <25 for Montreal Cognitive Assessment. According to Mini‐Mental State Examination score, 143 participants (25.6%) had mild cognitive impairment and 153 (27.4%) had severe cognitive impairment at 3 months. After adjustment for age, National Institutes of Health stroke score, education, and other covariates, the odds ratio for the highest quartile of serum MMP‐9 compared with the lowest quartile was 3.20 (95% confidence interval, 1.87–5.49) for cognitive impairment. Multiple‐adjusted spline regression model showed a linear association between MMP‐9 levels and cognitive impairment (P<0.001 for linearity). Sensitivity and subgroup analyses further confirmed these results. Similar significant findings were observed when cognitive impairment was defined by Montreal Cognitive Assessment score.

Conclusions

Increased serum MMP‐9 levels in the short‐term phase of ischemic stroke were associated with 3‐month cognitive impairment, independently of established risk factors.

Chronic cerebral hypoperfusion: a key mechanism leading to vascular cognitive impairment and dementia. Closing the translational gap between rodent models and human vascular cognitive impairment and dementia

Increasing evidence suggests that vascular risk factors contribute to neurodegeneration, cognitive impairment and dementia. While there is considerable overlap between features of vascular cognitive impairment and dementia (VCID) and Alzheimer's disease (AD), it appears that cerebral hypoperfusion is the common underlying pathophysiological mechanism which is a major contributor to cognitive decline and degenerative processes leading to dementia. Sustained cerebral hypoperfusion is suggested to be the cause of white matter attenuation, a key feature common to both AD and dementia associated with cerebral small vessel disease (SVD). White matter changes increase the risk for stroke, dementia and disability. A major gap has been the lack of mechanistic insights into the evolution and progress of VCID. However, this gap is closing with the recent refinement of rodent models which replicate chronic cerebral hypoperfusion. In this review, we discuss the relevance and advantages of these models in elucidating the pathogenesis of VCID and explore the interplay between hypoperfusion and the deposition of amyloid β (Aβ) protein, as it relates to AD. We use examples of our recent investigations to illustrate the utility of the model in preclinical testing of candidate drugs and lifestyle factors. We propose that the use of such models is necessary for tackling the urgently needed translational gap from preclinical models to clinical treatments.

High Serum Levels of Malondialdehyde and 8-OHdG are both Associated with Early Cognitive Impairment in Patients with Acute Ischaemic Stroke

Post-stroke cognitive impairment (PSCI) is an increasingly prevalent sequel after stroke that may associate with poor functional outcome and increased risk of recurrent stroke. We aimed to explore the relationship between oxidative stress biomarkers and the presence of PSCI. 193 first-ever acute ischaemic stroke patients were consecutively enrolled in the current study. The oxidative stress biomarkers malondialdehyde (MDA) and 8-hydroxydeoxyquanosine (8-OHdG) were measured within 24 h after admission. Cognition function was evaluated by the Mini-Mental State Examination (MMSE) at 1 month after stroke. Serum levels of 8-OHdG and MDA were both significantly higher in the PSCI (p < 0.001) compared with the non-PSCI group. Both the serum levels of both 8-OHdG and MDA were negatively correlated with the MMSE score. Receiver operating characteristic curve analysis was used to evaluate 8-OHdG and MDA as markers of a high risk of PSCI and produced area under curve values of 0.700 and 0.793. Adjusted logistic regression showed that serum 8-OHdG and MDA levels remained as independent markers of PSCI. High serum levels of malondialdehyde and 8-OHdG are associated with the presence of PSCI at 1 month after stroke.

Intracranial Arterial Dolichoectasia

An increased diameter (ectasis) and/or long and tortuous course (dolichosis) of at least one cerebral artery define intracranial arterial dolichoectasia (IADE). IADE could be detected incidentally or may give rise to an array of neurological complications including ischemic stroke, intracranial hemorrhage, or compression of surrounding neural structures. The basilar artery is preferentially affected and has been studied in more detail, mainly due to the presence of accepted diagnostic criteria proposed by Smoker and colleagues in 1986 (1). Criteria for the diagnoses of dolichoectasia in other cerebral arteries have been suggested. However, they lack validation across studies. The prevalence of IADE is approximately 0.08–6.5% in the general population, while in patients with stroke, the prevalence ranges from 3 to 17%. Variations among case series depend on the characteristics of the studied population, diagnostic tests used, and diagnostic criteria applied. In rare instances, an underlying hereditary condition, connective tissue disorder, or infection predispose to the development of IADE. However, most cases are sporadic and associated with traditional vascular risk factors including advanced age, male gender, and arterial hypertension. The link between this dilative arteriopathy and other vascular abnormalities, such as abdominal aortic aneurysm, coronary artery ectasia, and cerebral small vessel disease, suggests the underlying diffuse vascular process. Further understanding is needed on the physiopathology of IADE and how to prevent its progression and clinical complications.

Extracellular matrix inflammation in vascular cognitive impairment and dementia

Vascular cognitive impairment and dementia (VCID) include a wide spectrum of chronic manifestations of vascular disease related to large vessel strokes and small vessel disease (SVD). Lacunar strokes and white matter (WM) injury are consequences of SVD. The main vascular risk factor for SVD is brain hypoperfusion from cerebral blood vessel narrowing due to chronic hypertension. The hypoperfusion leads to activation and degeneration of astrocytes with the resulting fibrosis of the extracellular matrix (ECM). Elasticity is lost in fibrotic cerebral vessels, reducing the response of stiffened blood vessels in times of increased metabolic need. Intermittent hypoxia/ischaemia activates a molecular injury cascade, producing an incomplete infarction that is most damaging to the deep WM, which is a watershed region for cerebral blood flow. Neuroinflammation caused by hypoxia activates microglia/macrophages to release proteases and free radicals that perpetuate the damage over time to molecules in the ECM and the neurovascular unit (NVU). Matrix metalloproteinases (MMPs) secreted in an attempt to remodel the blood vessel wall have the undesired consequences of opening the blood-brain barrier (BBB) and attacking myelinated fibres. This dual effect of the MMPs causes vasogenic oedema in WM and vascular demyelination, which are the hallmarks of the subcortical ischaemic vascular disease (SIVD), which is the SVD form of VCID also called Binswanger's disease (BD). Unravelling the complex pathophysiology of the WM injury-related inflammation in the small vessel form of VCID could lead to novel therapeutic strategies to reduce damage to the ECM, preventing the progressive damage to the WM.

Elucidation of mechanism of blood-brain barrier damage for prevention and treatment of vascular dementia

It is well-known that the blood-brain barrier (BBB) plays significant roles in transporting intravascular substances into the brain. The BBB in cerebral capillaries essentially impedes the influx of intravascular compounds from the blood to the brain, while nutritive substances, such as glucose, can be selectively transported through several types of influx transporters in endothelial cells. In the choroid plexus, intravascular substances can invade the parenchyma as fenestrations exist in endothelial cells of capillaries. However, the substances cannot invade the ventricles easily as there are tight junctions between epithelial cells in the choroid plexus. This restricted movement of the substances across the cytoplasm of the epithelial cells constitutes a blood-cerebrospinal fluid barrier (BCSFB). In the brain, there are circumventricular organs, in which the barrier function is imperfect in capillaries. Accordingly, it is reasonable to consider that intravascular substances can move in and around the parenchyma of the organs. Actually, it was reported in mice that intravascular substances moved in the corpus callosum, medial portions of the hippocampus, and periventricular areas via the subfornical organs or the choroid plexus. Regarding pathways of intracerebral interstitial and cerebrospinal fluids to the outside of the brain, two representative drainage pathways, or perivascular drainage and glymphatic pathways, are being established. The first is the pathway in a retrograde direction to the blood flow through the basement membrane in walls of cerebral capillaries, the tunica media of arteries, and the vessels walls of the internal carotid artery. The second is in an anterograde direction to blood flow through the para-arterial routes, aquaporin 4-dependent transport through the astroglial cytoplasm, and para-venous routes, and then the fluids drain into the subarachnoid CSF. These fluids are finally considered to drain into the cervical lymph nodes or veins. These clearance pathways may play a role in maintenance of the barrier in the entire brain. Obstruction of the passage of fluids through the perivascular drainage and glymphatic pathways as well as damage of the BBB and BCSFB may induce several kinds of brain disorders, such as vascular dementia. In this review, we focus on the relationship between damage of the barriers and the pathogenesis of vascular dementia and introduce recent findings including our experimental data using animal models.

The ameliorative effects of exercise on cognitive impairment and white matter injury from blood-brain barrier disruption induced by chronic cerebral hypoperfusion in adolescent rats

Vascular dementia is the progressive change in blood vessels that leads to neuronal injuries in vulnerable areas induced by chronic cerebral hypoperfusion (CCH). CCH induces disruption of blood-brain barrier (BBB), and this BBB disruption can initiate the cognitive impairment and white matter injury. In the present study, we evaluated the effect of treadmill exercise on the cognitive impairment, white matter injury, and BBB disruption induced by CCH. Vascular dementia was induced by permanent bilateral common carotid arteries occlusion (BCCAO) in rats. The rats in the exercise group were made to run on a treadmill for 30min once a day for 14 weeks, starting 4 weeks after birth. Our results revealed that treadmill exercise group was alleviated the cognitive impairment and myelin degradation induced by CCH. The disruption of BBB after CCH indicates degradation of occludin, zonula occluden-1 (ZO-1), and up-regulation of matrix metalloproteinases (MMPs). Treadmill exercise may provide protective effects on BBB disruption from degradation of occludin, ZO-1, and overexpression of MMP-9 after CCH. These findings suggest that treadmill exercise ameliorates cognitive impairment and white matter injury from BBB disruption induced by CCH in rats. The present study will be valuable for means of prophylactic and therapeutic intervention for patients with CCH.