Morphologic Changes of Cerebral Veins in Hypertensive Rats: Venous Collagenosis Is Associated with Hypertension

Venous Collagenosis as Pathogenesis of White Matter Hyperintensity

OBJECTIVE

Periventricular white matter hyperintensities (pvWMHs) are commonly observed on MRI in older individuals and are associated with cognitive and motor decline. The etiology of pvWMH remains unknown. Venous collagenosis has been implicated, which may also interfere with perivascular fluid flow leading to dilation of perivascular spaces (PVS). Here, we examine relationships between in vivo pvWMH volume and ex vivo morphological quantification of collagenosis and the PVS in veins and arteries.

METHODS

Brain tissue from 25 Oregon Alzheimer's Disease Research Center subjects was selected to cover the full range of WMH burden. Tissue from white matter abutting the ventricle was stained with Masson's trichrome and smooth muscle actin. An automated hue based algorithm identified and segmented vessel into collagenized vessel walls, lumen, and PVS. Multiple linear regressions with pvWMH volume as the dependent variable and either collagen thickness or PVS width were performed with covariates of vessel diameter, age at death, sex, and interval between MRI and death.

RESULTS

PVS width and collagen thickness were significantly correlated in both arteries (r = 0.21, p = 0.001) and veins (r = 0.23, p = 0.001). Increased venous collagen (p = 0.017) was a significant predictor of higher pvWMH burden while arterial collagen was not (p = 0.128). Neither PVS width in arteries (p = 0.937) nor veins (p = 0.133) predicted pvWMH burden.

INTERPRETATION

These findings are consistent with a model in which venous collagenosis mediates the relationship between vascular risk factors and pvWMH. This study confirms the importance of changes to the venous system in contributing to MRI white matter lesions commonly observed with advanced age. ANN NEUROL 2022;92:992-1000.

Reduced white matter venous density on MRI is associated with neurodegeneration and cognitive impairment in the elderly

High-resolution susceptibility weighted imaging (SWI) provides unique contrast to small venous vasculature. The conspicuity of these mesoscopic veins, such as deep medullary veins in white matter, is subject to change from SWI venography when venous oxygenation in these veins is altered due to oxygenated blood susceptibility changes. The changes of visualization in small veins shows potential to depict regional changes of oxygen utilization and/or vascular density changes in the aging brain. The goal of this study was to use WM venous density to quantify small vein visibility in WM and investigate its relationship with neurodegenerative features, white matter hyperintensities (WMHs), and cognitive/functional status in elderly subjects (N = 137). WM venous density was significantly associated with neurodegeneration characterized by brain atrophy (β = 0.046± 0.01, p < 0.001), but no significant association was found between WM venous density and WMHs lesion load (p = 0.3963). Further analysis of clinical features revealed a negative trend of WM venous density with the sum-of-boxes of Clinical Dementia Rating and a significant association with category fluency (1-min animal naming). These results suggest that WM venous density on SWI can be used as a sensitive marker to characterize cerebral oxygen metabolism and different stages of cognitive and functional status in neurodegenerative diseases.

Pathogeneses and Imaging Features of Cerebral White Matter Lesions of Vascular Origins

White matter lesion (WML), also known as white matter hyperintensities or leukoaraiosis, was first termed in 1986 to describe the hyperintense signals on T2-weighted imaging (T2WI) and fluid-attenuated inversion recovery (FLAIR) maps. Over the past decades, a growing body of pathophysiological findings regarding WMLs have been discovered and discussed. Currently, the generally accepted WML pathogeneses mainly include hypoxia-ischemia, endothelial dysfunction, blood-brain barrier disruption, and infiltration of inflammatory mediators or cytokines. However, none of them can explain the whole dynamics of WML formation. Herein, we primarily focus on the pathogeneses and neuroimaging features of vascular WMLs. To achieve this goal, we searched papers with any type published in PubMed from 1950 to 2020 and cross-referenced the keywords including “leukoencephalopathy”, “leukoaraiosis”, “white matter hyperintensity”, “white matter lesion”, “pathogenesis”, “pathology”, “pathophysiology”, and “neuroimaging”. Moreover, references of the selected articles were browsed and searched for additional pertinent articles. We believe this work will supply the robust references for clinicians to further understand the different WML patterns of varying vascular etiologies and thus make customized treatment.

Emerging role of white matter lesions in cerebrovascular disease

White matter lesions have been implicated in the setting of stroke, dementia, intracerebral haemorrhage, several other cerebrovascular conditions, migraine, various neuroimmunological diseases like multiple sclerosis, disorders of metabolism, mitochondrial diseases and others. While much is understood vis a vis neuroimmunological conditions, our knowledge of the pathophysiology of these lesions, and their role in, and implications to, management of cerebrovascular diseases or stroke, especially in the elderly, are limited. Several clinical assessment tools are available for delineating white matter lesions in clinical practice. However, their incorporation into clinical decision-making and specifically prognosis and management of patients is suboptimal for use in standards of care. This article sought to provide an overview of the current knowledge and recent advances on pathophysiology, as well as clinical and radiological assessment, of white matter lesions with a focus on its development, progression and clinical implications in cerebrovascular diseases. Key indications for clinical practice and recommendations on future areas of research are also discussed. Finally, a conceptual proposal on putative mechanisms underlying pathogenesis of white matter lesions in cerebrovascular disease has been presented. Understanding of pathophysiology of white matter lesions and how they mediate outcomes is important to develop therapeutic strategies.

Eclampsia and postpartum onset of subarachnoid hemorrhage in dual setting of cerebral venous thrombosis and posterior reversible encephalopathy syndrome: A case report

Subarachnoid hemorrhage (SAH) can be an initial presentation of cerebral venous thrombosis. Eclampsia and postpartum onset of SAH should prompt physicians to identify possible causes and institute prompt management to avert irreversible cerebrovascular sequelae.

A Review of Translational Magnetic Resonance Imaging in Human and Rodent Experimental Models of Small Vessel Disease

Cerebral small vessel disease (SVD) is a major health burden, yet the pathophysiology remains poorly understood with no effective treatment. Since much of SVD develops silently and insidiously, non-invasive neuroimaging such as MRI is fundamental to detecting and understanding SVD in humans. Several relevant SVD rodent models are established for which MRI can monitor in vivo changes over time prior to histological examination. Here, we critically review the MRI methods pertaining to salient rodent models and evaluate synergies with human SVD MRI methods. We found few relevant publications, but argue there is considerable scope for greater use of MRI in rodent models, and opportunities for harmonisation of the rodent-human methods to increase the translational potential of models to understand SVD in humans. We summarise current MR techniques used in SVD research, provide recommendations and examples and highlight practicalities for use of MRI SVD imaging protocols in pre-selected, relevant rodent models.

Relationship Between Venules and Perivascular Spaces in Sporadic Small Vessel Diseases

Supplemental Digital Content is available in the text.

Perivascular spaces (PVS) around venules may help drain interstitial fluid from the brain. We examined relationships between suspected venules and PVS visible on brain magnetic resonance imaging.

Potential Mechanism of Venous System for Leukoaraiosis: From post-mortem to in vivo Research

BACKGROUND

Leukoaraiosis (LA), widely accepted as a feature of cerebral small vessel disease, significantly increases the incidence of stroke, dementia, and death. Cerebral small artery disease has been considered as one of the main causes of LA. However, since the term "venous collagenosis" (VC) was proposed in an atrophy research in 1995, there have been pathological and neuroimaging studies proving the association between the venous system and LA in aging, Alz-heimer's disease (AD), and Parkinson's disease.

SUMMARY

Autopsy studies confirmed that thickening of the lumen wall in venules, which results from the deposition of collagen I and III, leading to vessel stenosis or occlusion, is closely associated with LA. Susceptibility-weighted imaging research revealed a controversial association of deep medullary veins and LA in vivo, regarding which there are no standard criteria currently. Nevertheless, retinal venous changes had been reported to increase the risk of LA development, providing a novel way for in vivo evaluation. As for the internal jugular vein, jugular venous reflux could double the LA score in aging and modulate circulation of cerebral spinal fluids. Key Messages: Disruption of the venous system was notably associated with LA in aging, AD, and Parkinson's disease post-mortem and in in vivo models. The venous pathological changes may induce cerebral hypoperfusion, drainage system disruption, and vasogenic oedema in the veins around the periventricular white matter. The clarification of VC in LA may provide an early prevention and early treatment strategy for LA patients.

A Novel Model of Mixed Vascular Dementia Incorporating Hypertension in a Rat Model of Alzheimer's Disease

Alzheimer's disease (AD) and mixed dementia (MxD) comprise the majority of dementia cases in the growing global aging population. MxD describes the coexistence of AD pathology with vascular pathology, including cerebral small vessel disease (SVD). Cardiovascular disease increases risk for AD and MxD, but mechanistic synergisms between the coexisting pathologies affecting dementia risk, progression and the ultimate clinical manifestations remain elusive. To explore the additive or synergistic interactions between AD and chronic hypertension, we developed a rat model of MxD, produced by breeding APPswe/PS1ΔE9 transgenes into the stroke-prone spontaneously hypertensive rat (SHRSP) background, resulting in the SHRSP/FAD model and three control groups (FAD, SHRSP and non-hypertensive WKY rats, n = 8-11, both sexes, 16-18 months of age). After behavioral testing, rats were euthanized, and tissue assessed for vascular, neuroinflammatory and AD pathology. Hypertension was preserved in the SHRSP/FAD cross. Results showed that SHRSP increased FAD-dependent neuroinflammation (microglia and astrocytes) and tau pathology, but plaque pathology changes were subtle, including fewer plaques with compact cores and slightly reduced plaque burden. Evidence for vascular pathology included a change in the distribution of astrocytic end-foot protein aquaporin-4, normally distributed in microvessels, but in SHRSP/FAD rats largely dissociated from vessels, appearing disorganized or redistributed into neuropil. Other evidence of SVD-like pathology included increased collagen IV staining in cerebral vessels and PECAM1 levels. We identified a plasma biomarker in SHRSP/FAD rats that was the only group to show increased Aqp-4 in plasma exosomes. Evidence of neuron damage in SHRSP/FAD rats included increased caspase-cleaved actin, loss of myelin and reduced calbindin staining in neurons. Further, there were mitochondrial deficits specific to SHRSP/FAD, notably the loss of complex II, accompanying FAD-dependent loss of mitochondrial complex I. Cognitive deficits exhibited by FAD rats were not exacerbated by the introduction of the SHRSP phenotype, nor was the hyperactivity phenotype associated with SHRSP altered by the FAD transgene. This novel rat model of MxD, encompassing an amyloidogenic transgene with a hypertensive phenotype, exhibits several features associated with human vascular or "mixed" dementia and may be a useful tool in delineating the pathophysiology of MxD and development of therapeutics.

The relationship between deep medullary veins score and the severity and distribution of intracranial microbleeds

Background

Microbleeds are frequently detected in normal elderly population, and their presence is associated with an increased risk of intracerebral hemorrhage, ischemic stroke and cognitive impairment. Previous histopathologic findings mainly focused on arteries and capillaries. Nevertheless, few studies investigated the relationship between venous disruption and microbleeds.

Objective

We aimed to evaluate the extent of venous disruption in vivo and assess the correlation between deep medullary veins (DMVs) disruption and the severity and distribution of intracranial microbleeds in patients with cerebral small vessel disease (cSVD).

Methods

We retrospectively reviewed the clinical, laboratory and imaging data of the patients admitted to our department who received brain MRI and presented with CSVD imaging markers. Susceptibility weighted imaging (SWI) phase images were used to observe characteristics of DMVs and derive a brain region-based DMVs visual score. SWI magnitude images were used to evaluate microbleeds. We recorded the number and distribution (lobar or deep or infratentorial) of microbleeds. One-way ANOVA and logistic-regression analysis were used to examine the association between the DMVs score and microbleeds.

Results

A total of 369 cSVD patients were analyzed, including 177 (48.0%) patients with microbleeds, among whom 81(45.8%) patients had 1–2 microbleeds and 96 (54.2%) patients had ≥3 microbleeds (extensive microbleeds). The patients' DMVs score ranged from 0 to18, with a median score of 8(6–12). Higher DMVs score was independently associated with extensive microbleeds (OR = 1.108, 95%Cl: 1.010–1.215, p = 0.03) after adjusting for gender, hypertension, hyperhomocysteinemia, Fazekas score and number of lacunas. According to the distribution, 38 (21.5%) patients were found with strict lobar microbleeds, while 139 (78.5%) patients had non-strict lobar microbleeds. Higher DMVs score was also independently associated with non-strict lobar microbleeds (OR = 1.106, 95% Cl: 1.019–1.200, p = 0.016) after adjusting for gender, hypertension, hyperhomocysteinemia, Fazekas score and number of lacunas. DMVs score was not associated with strict lobar microbleeds (p = 0.307).

Conclusion

DMVs disruption might be involved in the development of extensive microbleeds, especially non-strict lobar cerebral microbleeds.

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Deep medullary veins disruption was associated with extensive microbleeds.

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Deep medullary veins disruption was associated with non-strict lobar microbleeds.

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Venous insufficiency may be one of the pathogenic mechanisms of microbleeds.

Vascular cognitive impairment: pathophysiological mechanisms, insights into structural basis, and perspectives in specific treatments

Vascular cognitive impairment (VCI) and vascular dementia are the most common forms of cognitive disorder associated with cerebrovascular disease and related to increased morbidity and mortality among the older population. Growing evidence suggests the contribution of blood-pressure variability, cardiac arrhythmia, hyperactivation of the renin-angiotensin-aldosterone system, endothelial dysfunction, vascular remodeling and stiffness, different angiopathies, neural tissue homeostasis, and systemic metabolic disorders to the pathophysiology of VCI. In this review, we focus on factors contributing to cerebrovascular disease, neurovascular unit alterations, and novel approaches to cognitive improvement in patients with cognitive decline. One of the important factors associated with the neuronal causes of VCI is the S100B protein, which can affect the expression of cytokines in the brain, support homeostasis, and regulate processes of differentiation, repair, and apoptosis of the nervous tissue. Since the pathological basis of VCI is complex and diverse, treatment affecting the mechanisms of cognitive disorders should be developed. The prospective role of a novel complex drug consisting of released-active antibodies to S100 and to endothelial NO synthase in VCI treatment is highlighted.

Retinal microvasculature changes in amyloid-negative subcortical vascular cognitive impairment compared to amyloid-positive Alzheimer's disease

BACKGROUND AND PURPOSE

To investigate small vessel abnormalities in patients with cognitive impairment, we compared retinal microvascular alterations between patients with cognitive impairment related to Alzheimer's disease (ADCI) and those with subcortical vascular cognitive impairment (SVCI).

METHODS

We prospectively recruited 29 amyloid-positive ADCI patients, 28 amyloid-negative SVCI patients that were confirmed by ¹¹C-PiB-PET scan and 34 individuals with normal cognition (NC). The three groups were compared in terms of retinal vascular variables (retinal fractal dimension, vascular caliber, tortuosity and branching angle) by using a semi-automated, computer-assisted analysis of digital fundus photographs. We also investigated the relationship between retinal variables and white matter hyperintensities (WMH) on MRI.

RESULTS

Compared to NC individuals, the SVCI patients had smaller total and arteriolar fractal dimensions, whereas there was no significant difference of fractal dimension between ADCI and NC. Other retinal variables did not differ among the three groups. A significant correlation existed between fractal dimension and WMH volume.

CONCLUSIONS

Retinal microvascular alterations, especially retinal fractal dimension, may be useful markers that reflect cerebral microvascular changes in patients with SVCI as opposed to ADCI, who had no definite difference in retinal variables compared to the NC group.

Does pathology of small venules contribute to cerebral microinfarcts and dementia?

Microinfarcts are small, but strikingly common, ischemic brain lesions in the aging human brain. There is mounting evidence that microinfarcts contribute to vascular cognitive impairment and dementia, but the origins of microinfarcts are unclear. Understanding the vascular pathologies that cause microinfarcts may yield strategies to prevent their occurrence and reduce their deleterious effects on brain function. Current thinking suggests that cortical microinfarcts arise from the occlusion of penetrating arterioles, which are responsible for delivering oxygenated blood to small volumes of tissue. Unexpectedly, pre-clinical studies have shown that the occlusion of penetrating venules, which drain deoxygenated blood from cortex, lead to microinfarcts that appear identical to those resulting from arteriole occlusion. Here we discuss the idea that cerebral venule pathology could be an overlooked source for brain microinfarcts in humans. This article is part of the Special Issue "Vascular Dementia". Cover Image for this Issue: doi: 10.1111/jnc.14167.

Cerebral Venous Collagen Remodeling in a Modified White Matter Lesions Animal Model

To mimic the expected pathological changes of white matter lesions (WMLs) and increase the stability, we applied modified two-vessel occlusion (modified 2VO) (1-week interval bilateral carotid artery occlusion) in stroke-prone renovascular hypertensive rats (RHRSP) and established a modified WMLs model (RHRSP/modified 2VO) that compared their phenotypes with RHRSP and sham-operated rats. In addition, we tried to differentiate small veins from small arteries through the presence of smooth muscle to study the pathological changes of small veins detailed in the model. RHRSP/modified 2VO rats showed higher stability and more extensive white matter damage without an obvious increase in mortality rate at 12 weeks after the modified 2VO operation compared to RHRSP rats. RHRSP/modified 2VO rats showed more severe small venous collagen deposition than RHRSP rats, and the majority of the deposition was collagen I and IV rather than collagen III. In addition, RHRSP/modified 2VO rats possessed cognitive impairment, mild wall thickness and blood-brain barrier disruption. Our findings suggest that the modified WMLs model (RHRSP/modified 2VO) mimics cognitive impairment and small vessel pathological changes similar to WMLs in humans. Differentiating small veins from small arteries through smooth muscle is feasible, and marked small venous deposition may play an important role in the hypertensive white matter lesions.

CADASIL accelerated by acute hypotension: Arterial and venous contribution to leukoaraiosis

OBJECTIVE

To underline the importance of blood pressure regulation in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and to describe changes that occur in the veins in this condition, specifically venous collagenosis associated with leukoaraiosis.

METHODS

Case report with neuroimaging and pathologic data.

RESULTS

A 61-year-old man with genetically confirmed CADASIL was initially lucid following a motor vehicle accident but subsequently became hypotensive (60/40 mm Hg) due to an open femur fracture and required intubation. Multiple new white matter infarcts appeared on brain imaging. A second hypotensive episode days later was associated with new coin-sized infarcts in the bilateral corona radiata and cerebellar peduncles, and resulted in quadriplegia. No embolic source was found on cardiac or vascular imaging. He died 5 weeks post trauma. Autopsy revealed extensive subcortical and periventricular leukoencephalopathy and multiple cavitations involving deep subcortical gray and white matter. Small arteries had thickened walls, disruption of the muscularis, and intimal periodic acid-Schiff (PAS)-positive material. Both larger periventricular and small caliber veins had thickened walls that were PAS-negative and trichrome-positive, consistent with venous collagenosis. There was no pathologic evidence of global hypoxia or diffuse axonal injury.

CONCLUSIONS

The findings suggest rapid acceleration of CADASIL pathology from acute hypotension in the setting of impaired vasoreactivity. In addition, collagenosis of veins in the affected white matter regions suggests that the veins may play an important, though largely overlooked, role in maintaining white matter integrity.

Beneficial Effects of Paeoniflorin Enriched Extract on Blood Pressure Variability and Target Organ Damage in Spontaneously Hypertensive Rats

Blood pressure variability (BPV) is associated with the development and progression of severe target organ damage (TOD). This study aims to evaluate the protective effect of paeoniflorin enriched extract from Radix Paeoniae Alba (PG) on BPV and TOD in spontaneously hypertensive rats (SHR). All SHR were orally treated with distilled water, metoprolol (MP, 20 mg/kg), and PG (PG-H, 90 mg/kg or PG-L, 30 mg/kg) for a single time or daily for 7 weeks. The 24-hour dynamic blood pressure was monitored and then calculated BPV including long- and short-term systolic blood pressure variability (SBPV), diastolic blood pressure variability (DBPV), mean blood pressure variability (MBPV), and heart rate variability (HRV) as well as the 24-hour-SBP, 24-hour-DBP, and 24-hour-MBP. The protective effects of PG on TOD were observed by histopathologic and biochemical detection. The results indicated that long- and short-term SBPV, DBPV, MBPV, and HRV as well as 24-hour-SBP, 24-hour-DBP, and 24-hour-MBP showed no significant changes after single-dose administration of PG and significantly decreased after administration with PG for 7 weeks. PG could also markedly improve the damage of aorta, heart, kidney, and brain. This study suggested that PG could notably reduce BPV, stabilize blood pressure, and mitigate TOD in SHR.

[Effect of cytoflavin on the clinical and autonomic-psychological manifestations of hypertensive disease]

AIM

To evaluate the impact of incorporating cytoflavin in a treatment regimen for patients with different stages of hypertensive disease (HD).

SUBJECTS AND METHODS

The results of treatment were analyzed in 140 patients with HD (53 with Stage I, 50 with Stage II, and 37 with Stage III). According to the treatment regimen, the patients were divided into 2 groups. A study group (n=74) received combination treatment involving antihypertensive therapy and cytoflavin intravenously dropwisely in a single dose of 200 ml of 5% glucose solution for 10 days, then 2 tablets twice daily for 60 days, with a total cycle time being 70 days. A comparison group (n=66) had antihypertensive therapy only. Thirty apparently healthy individuals (a control group) were examined to have reference values. All the patients were examined using conventional clinical and laboratory studies. The patients' complaints and neurological status were assessed using respective questionnaires over time - before and after treatment.

RESULTS

The incorporation of cytoflavin in a treatment regimen was ascertained to reduce the degree of anxiety, depressive, dissomnic, and cognitive disorders, improves quality of life in patients with Stage I HD, and lowers the degree of asthenic and autonomic disorders in all disease stages.

CONCLUSION

The found efficacy and safety of the drug may recommend its incorporation in combination therapy regimens for Stages I-III HD.

Vascular cognitive impairment and dementia

Vascular contributions to cognitive impairment are receiving heightened attention as potentially modifiable factors for dementias of later life. These factors have now been linked not only to vascular cognitive disorders but also Alzheimer's disease. In this chapter we review 3 related topics that address vascular contributions to cognitive impairment: 1. vascular pathogenesis and mechanisms; 2. neuropsychological and neuroimaging phenotypic manifestations of cerebrovascular disease; and 3. prospects for prevention of cognitive impairment of later life based on cardiovascular and stroke risk modification. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Unraveling the potential co-contributions of cerebral small vessel vasculopathy to the pathogenesis of Alzheimer's dementia

Emerging evidence for the potential co-contributions of small vessel vasculopathy to dementia has resulted in a more nuanced view of Alzheimer's disease (AD) pathogenesis. Although cerebral small vessel disease, visualized on magnetic resonance imaging as hyperintense signal abnormalities, independently predicts the incidence and clinical progression of dementia, the relationships between AD pathology, white matter hyperintensity volume, genotype, and cognitive decline in AD remain unclear. The study by Morgen and colleagues, recently published in Alzheimer's Research & Therapy, presents important new findings on the associations between apolipoprotien E ε4 genotype, white matter hyperintensities, and cognition, independent of vascular risk, in a cohort of AD patients.