Mid- to Late-Life Time-Averaged Cumulative Blood Pressure and Late-Life Retinal Microvasculature: The ARIC Study.

Background The associations of time-averaged cumulative blood pressure (BP) from midlife to late life with microvasculature expressed as retinal vessel diameters is not well studied. The aim of this study was to evaluate the association of cumulative systolic BP and diastolic BP (DBP) with retinal vessel calibers, focusing on race differences. Methods and Results The analysis included 1818 adults from the ARIC (Atherosclerosis Risk in Communities) study attending the fifth visit (2011-2013; age 77±5 years, 17.1% Black participants). Time-averaged cumulative BPs were calculated as the sum of averaged BPs from adjacent consecutive visits (visits 1-5) indexed to total observation time (24±1 years). Summarized estimates for central retinal arteriolar equivalent and central retinal venular equivalent at the fifth visit represent average retinal vessel diameters. The arteriole:venule ratio was calculated. We tested for effect modification by race. Results from multiple linear regression models suggested that higher time-averaged cumulative DBP (ß [95% CI] per 1-SD increase: -1.78 [-2.53, -1.02], P<0.001 and -0.005 [-0.009, -0.002], P=0.004, respectively) but not systolic BP (-0.52 [-1.30, 0.26], P=0.189 and 0.001 [-0.002, 0.005], P=0.485, respectively) was associated with smaller central retinal arteriolar equivalent and arteriole:venule ratio. The association between time-averaged cumulative DBP and arteriole:venule ratio was strongest in White participants (interaction P=0.007). The association of cumulative systolic BP and DBP with central retinal venular equivalent was strongest in Black participants (interaction P=0.015 and 0.011, respectively). Conclusions Exposure to higher BP levels, particularly DBP, from midlife to late life is associated with narrower retinal vessel diameters in late life. Furthermore, race moderated the association of cumulative BP exposure with retinal microvasculature.

Identification of cardiovascular high-risk groups from dynamic retinal vessel signals using untargeted machine learning.

AIMS: Dynamic retinal vessel analysis (DVA) provides a non-invasive way to assess microvascular function in patients and potentially to improve predictions of individual cardiovascular (CV) risk. The aim of our study was to use untargeted machine learning on DVA in order to improve CV mortality prediction and identify corresponding response alterations. METHODS AND RESULTS: We adopted a workflow consisting of noise reduction and extraction of independent components within DVA signals. Predictor performance was assessed in survival random forest models. Applying our technique to the prediction of all-cause mortality in a cohort of 214 haemodialysis patients resulted in the selection of a component which was highly correlated to maximal venous dilation following flicker stimulation (vMax), a previously identified predictor, confirming the validity of our approach. When fitting for CV mortality as the outcome of interest, a combination of three components derived from the arterial signal resulted in a marked improvement in predictive performance. Clustering analysis suggested that these independent components identified groups of patients with substantially higher CV mortality. CONCLUSION: Our results provide a machine learning workflow to improve the predictive performance of DVA and identify groups of haemodialysis patients at high risk of CV mortality. Our approach may also prove to be promising for DVA signal analysis in other CV disease states.

Hypoxic pulmonary vasoconstriction as a regulator of alveolar-capillary oxygen flux: A computational model of ventilation-perfusion matching.

The relationship between regional variabilities in airflow (ventilation) and blood flow (perfusion) is a critical determinant of gas exchange efficiency in the lungs. Hypoxic pulmonary vasoconstriction is understood to be the primary active regulator of ventilation-perfusion matching, where upstream arterioles constrict to direct blood flow away from areas that have low oxygen supply. However, it is not understood how the integrated action of hypoxic pulmonary vasoconstriction affects oxygen transport at the system level. In this study we develop, and make functional predictions with a multi-scale multi-physics model of ventilation-perfusion matching governed by the mechanism of hypoxic pulmonary vasoconstriction. Our model consists of (a) morphometrically realistic 2D pulmonary vascular networks to the level of large arterioles and venules; (b) a tileable lumped-parameter model of vascular fluid and wall mechanics that accounts for the influence of alveolar pressure; (c) oxygen transport accounting for oxygen bound to hemoglobin and dissolved in plasma; and (d) a novel empirical model of hypoxic pulmonary vasoconstriction. Our model simulations predict that under the artificial test condition of a uniform ventilation distribution (1) hypoxic pulmonary vasoconstriction matches perfusion to ventilation; (2) hypoxic pulmonary vasoconstriction homogenizes regional alveolar-capillary oxygen flux; and (3) hypoxic pulmonary vasoconstriction increases whole-lobe oxygen uptake by improving ventilation-perfusion matching.

Impaired retinal microvascular function predicts long-term adverse events in patients with cardiovascular disease.

AIMS: Endothelial dysfunction is a precursor to the development of symptomatic atherosclerosis. Retinal microvascular reactivity to flicker light stimulation is a marker of endothelial function and can be quantified in vivo. We sought to determine whether retinal microvascular endothelial dysfunction predicts long-term major adverse cardiovascular events (MACE). METHODS AND RESULTS: In a single-centre prospective observational study, patients with coronary artery disease (CAD) or cardiovascular risk factors underwent dynamic retinal vessel assessment in response to flicker light stimulation and were followed up for MACE. Retinal microvascular endothelial dysfunction was quantified by measuring maximum flicker light-induced retinal arteriolar dilatation (FI-RAD) and flicker light-induced retinal venular dilatation (FI-RVD). In total, 252 patients underwent dynamic retinal vessel assessment and 242 (96%) had long-term follow-up. Of the 242 patients, 88 (36%) developed MACE over a median period of 8.6 years (interquartile range 6.0-9.1). After adjustment for traditional risk factors, patients within the lowest quintile of FI-RAD had the highest risk of MACE [odds ratio (OR) 5.21; 95% confidence interval (CI) 1.78-15.28]. Patients with lower FI-RAD were also more likely to die (OR 2.09; 95% CI 1.00-4.40, per standard deviation decrease in FI-RAD). In Kaplan-Meier analysis, patients with FI-RAD responses below the cohort median of 1.4% exhibited reduced MACE-free survival (55.5 vs. 71.5%; log-rank P = 0.004). FI-RVD was not predictive of MACE. CONCLUSION: Retinal arteriolar endothelial dysfunction is an independent predictor of MACE in patients with CAD or cardiovascular risk factors. Dynamic retinal vessel analysis may provide added benefit to traditional risk factors in stratifying patients at risk for cardiovascular events.

Capillary-venule malformation is a microfistulous variant of arteriovenous malformation.

OBJECTIVE: To describe typical clinical presentation of patients with microfistular, capillary-venule (CV) malformation as a variant form of arteriovenous malformations (AVM). METHODS: A retrospective clinical analysis of 15 patients with CV-AVM confirmed by a computational flow model enrolled in a prospective database of patients with congenital vascular malformation between January 2008 and May 2018. RESULTS: The mean age of the patients at first time of presentation was 30 years with balanced sex ratio. Presentation was dominated by soft tissue hypertrophy (n = 12 [80.0%]) and atypical varicose veins (n = 11 [73.3%]). The anatomic location of enlarged varicose veins gave no uniform pattern and did not correspond with the typical picture of primary varicose vein disease. Most often, symptomatic CV-AVM was found at the lower extremities in this series of unselected patients. The most frequent compartment affected was the subcutis (n = 14 [93.3%]), involvement of muscle was recorded in one-third and cutis in one-fourth of patients. CONCLUSIONS: A high grade of clinical suspicion is needed to recognize CV-AVM and to prevent inadequate therapy owing to missed diagnosis.

Skin auto-fluorescence as a measure of advanced glycation end-products is associated with microvascular health in patients with COPD.

BACKGROUND AND OBJECTIVES: Chronic obstructive pulmonary disease (COPD) is associated with systemic inflammation and oxidative stress. These physiological processes can lead to increased formation and accumulation of advanced glycation end-products (AGEs), that can play a role in vascular complications. In this cross-sectional study, we determined the association between skin AGEs and microvascular health in patients with COPD. METHODS: Clinical characteristics and cardiovascular parameters, including pulmonary function, metabolic and inflammatory parameters, and blood pressure, were obtained in this observational study with patients with COPD. Skin concentrations of AGEs were assessed non-invasively by measuring skin autofluorescence (AF). Retinal vessel analysis was used as a marker of microvascular health. RESULTS: 62 patients with COPD (52% males; mean age: 64.4 ± 8.4 years; mean FEV1: 45.0 ± 20.7%pred.) were analysed. Mean skin AF was 2.75 ± 0.64 arbitrary units. Skin AF in patients with COPD was negatively associated with retinal arteriolar diameter (ß -0.021, 95% CI -0.040 to -0.002; p = 0.031) and arteriole-to-venular ratio (ß -7.233, 95% CI -9.732 to -4.734; p < 0.001) and positively associated with retinal venular diameter (ß 0.029, 95% CI 0.019 to 0.038; p < 0.001) after adjustment for sex, age, lung function, pack-years of smoking and conventional cardiovascular risk factors. CONCLUSION: We document for the first time that skin AF in patients with COPD is independently associated with retinal arteriolar and venular vessel diameters, biological indicators for microvascular health. This adds to the evidence that AGEs are an accessible marker of microvascular health.

Development of Mucosal PNAd+ and MAdCAM-1+ Venules during Disease Course in Ulcerative Colitis.

PNAd and MAdCAM-1 addressins on venules are of importance in T-cell homing and potential therapeutic targets in ulcerative colitis (UC). Normally, PNAd+ high endothelial venules (HEVs) are only present in lymphoid organs, whereas small numbers of MAdCAM-1+ venules can be seen in non-lymphoid tissue. We aimed to study their presence in the intestinal mucosa of UC patients at diagnosis and during follow-up, and their correlation with disease activity. Colonic biopsy specimens of 378 UC patients were analyzed by immunohistochemistry for CD3, CD20, ERG, MECA-79 (PNAd) and MECA-376 (MAdCAM-1) and compared to healthy controls (HC). The proportion of PNAd+HEVs in UC at diagnosis was 4.9% (IQR 2.0%-8.3%), while none were detected in HC. During follow-up, PNAd+HEVs completely disappeared in remission (n = 93), whereas the proportion in active disease was similar to baseline (n = 285, p = 0.39). The proportion of MAdCAM-1+venules in UC at baseline was 5.8% (IQR 2.6-10.0). During follow-up, the proportion in remission was comparable to diagnosis, but upregulated (7.5% (IQR 4.4-10.9), p = 0.001) in active disease. In conclusion, PNAd+HEVs appear in UC during active inflammation which could thus serve as a marker for disease activity, whereas MAdCAM-1+venules remain present after inflammation is resolved and increase after subsequent flares, reflecting chronicity and potentially serving as a therapeutic target.

Effects of hemodialysis on blood volume, macro- and microvascular function.

BACKGROUND: Vascular dysfunction is considered to spur the progression of cardiovascular disease in hemodialysis (HD) patients. Whether the HD procedure itself contributes to vascular dysfunction remains incompletely investigated. The present study sought to comprehensively assess the effects of HD on arterial and venous function along with concomitant changes in blood volume (BV). METHODS AND RESULTS: We determined BV with high-precision, automated carbon monoxide-rebreathing, arterial stiffness using applanation tonometry and intrinsic microvascular function via retinal vessel analysis prior to and after conventional 4-hour HD in fasting-controlled conditions in 10 patients. All HD patients were non-smokers and non-obese (body mass index = 22.8 ±â€¯2.8 m·kg-2). Hypertension (70%), coronary artery disease (40%) and diabetes mellitus (20%) were the most prevalent comorbidities. Prior to HD, all patients presented with hypervolemia (+2208 ±â€¯1213 ml). HD decreased body weight (-1.72 ±â€¯1.25 kg, P = 0.002) and plasma volume (-689 ±â€¯566 ml, P = 0.004), while hematocrit (Hct) was concomitantly increased (+4.8 ±â€¯4.5%, P = 0.009). HD did not affect large elastic artery stiffness, as determined by carotid-femoral pulse wave velocity (P = 0.448) and carotid distensibility (P = 0.562). In contrast, flicker light-induced retinal venular dilation was reduced by three-fourths after HD (-2.4 ±â€¯1.7%, P = 0.039), in parallel to increased retinal venular diameter (+11.2 ±â€¯4.9 µm, P = 0.002). In regression analyses, a negative association was observed between HD-induced changes in Hct and retinal venular dilation (r ≥ -0.89, P ≤ 0.045). CONCLUSION: Conventional HD resulting in substantial plasma volume removal do not alter large artery elastic properties, whereas intrinsic microvascular venular dilator function is markedly impaired, an effect directly associated with the increase in hemoconcentration.

Cardiovascular health and retinal microvascular geometry in Australian 11-12 year-olds.

Traditional retinal microvascular parameters (smaller arteriolar and greater venular caliber) are associated with cardiovascular risk factors, pre-clinical vascular phenotypes and clinical cardiovascular events in adults. Although novel retinal microvascular geometric parameters showed analogous associations in adults, less is known whether these parameters are associated with cardiovascular health from childhood. In a population-based cross-sectional study in children (n = 1126, mean age 11.4 years, 50.3% girls), we examined associations of cardiovascular risk factors and pre-clinical arterial phenotypes with retinal geometric parameters. Cardiovascular parameters included body mass index (BMI), an inflammatory marker (GlycA), low-density lipoprotein and high-density lipoprotein (HDL) cholesterol, systolic (SBP) and diastolic blood pressure, large artery functional (pulse wave velocity, PWV and carotid arterial elasticity) and structural (carotid intima-media thickness) phenotypes. Retinal geometric parameters (fractal dimension (Df) and tortuosity) were quantified from retinal images. Multivariable regression models were performed and adjusted for potential confounders. Higher values for BMI, SBP and PWV showed weak associations with lower (i.e. worse) arteriolar but not venular Df (standardized mean difference (SMD) ranging from -0.07 to -0.09, 95% CIs -0.15 to -0.01). Higher HDL was associated with greater arteriolar Df (SMD 0.07, 95% CI 0.01 to 0.13). Only higher SBP was associated with higher (i.e. worse) arteriolar but not venular tortuosity (SMD 0.09, 95% CI 0.02 to 0.16). In generally healthy children, some risk factors and pre-clinical arterial phenotypes show small associations with retinal geometric parameters. In childhood, emerging relationships between microvascular parameters and cardiometabolic risk may be better described by retinal vascular caliber than by geometric parameters.

Microvascular reactivity in rehabilitating cardiac patients based on measurements of retinal blood vessel diameters.

BACKGROUND: Exercise-based rehabilitation improves general cardiovascular fitness. The impact on the microvascular system has been studied in less detail. We measured changes in retinal blood vessel diameters, as a proxy for microvascular reactivity, in cardiac patients and we assessed the impact of a rehabilitation program on retinal vessel diameters. DESIGN: Cardiac patients (n = 78) and age-matched healthy controls (n = 32) performed an initial maximal endurance cycling test. Patients then participated in a 12-week rehabilitation program with additional endurance tests being performed six and twelve weeks after the initial test. METHODS: Fundus images were collected immediately before and 0, 5, 10, 15 and 30 min after the endurance test. Widths of retinal blood vessels, represented as Central Retinal Arteriolar/Venular Equivalent (CRAE/CRVE) were calculated from the images. RESULTS: At the start of the rehabilitation program, CRAE and CRVE values of the patients changed immediately after the endurance test with respectively -1.90 µm (95% CI: -3.58; -0.22) and -5.32 µm (95% CI: -7.33; -3.30) compared to baseline values. In contrast, CRAE and CRVE values of healthy controls were respectively increased [3.52 µm (95% CI: 2.34; 4.69)] and decreased [-3.17 µm (95% CI: -5.27; -1.07)]. After six and twelve weeks, CRAE responses of patients immediately after endurance test increased respectively with 5.98 µm (95% CI: 4.25; 7.71) and 4.44 µm (95% CI: 3.18; 5.71). These responses were similar to the microvascular reactions observed in the control group. CONCLUSIONS: Arteriolar and venular retinal microvascular responses in cardiac patients were different from the ones of healthy controls. Retinal microvascular response of cardiac patients improved during rehabilitation.

Neutrophil elastase plays a non-redundant role in remodeling the venular basement membrane and neutrophil diapedesis post-ischemia/reperfusion injury.

Ischemia/reperfusion (I/R) injury is a severe inflammatory insult associated with numerous pathologies, such as myocardial infarction, stroke and acute kidney injury. I/R injury is characterized by a rapid influx of activated neutrophils secreting toxic free radical species and degrading enzymes that can irreversibly damage the tissue, thus impairing organ functions. Significant efforts have been invested in identifying therapeutic targets to suppress neutrophil recruitment and activation post-I/R injury. In this context, pharmacological targeting of neutrophil elastase (NE) has shown promising anti-inflammatory efficacy in a number of experimental and clinical settings of I/R injury and is considered a plausible clinical strategy for organ care. However, the mechanisms of action of NE, and hence its inhibitors, in this process are not fully understood. Here we conducted a comprehensive analysis of the impact of NE genetic deletion on neutrophil infiltration in four murine models of I/R injury as induced in the heart, kidneys, intestine and cremaster muscle. In all models, neutrophil migration into ischemic regions was significantly suppressed in NE-/- mice as compared with wild-type controls. Analysis of inflamed cremaster muscle and mesenteric microvessels by intravital and confocal microscopy revealed a selective entrapment of neutrophils within venular walls, most notably at the level of the venular basement membrane (BM) following NE deletion/pharmacological blockade. This effect was associated with the suppression of NE-mediated remodeling of the low matrix protein expressing regions within the venular BM used by transmigrating neutrophils as exit portals. Furthermore, whilst NE deficiency led to reduced neutrophil activation and vascular leakage, levels of monocytes and prohealing M2 macrophages were reduced in tissues of NE-/- mice subjected to I/R. Collectively our results identify a vital and non-redundant role for NE in supporting neutrophil breaching of the venular BM post-I/R injury but also suggest a protective role for NE in promoting tissue repair. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Characteristics of the retinal microvasculature in association with cardiovascular risk markers in children with overweight, obesity and morbid obesity.

To aim of this study was to evaluate characteristics of the retinal microvasculature, but particularly potential associations with classic and novel (endothelial function and low-grade inflammation)markers for cardiovascular risk, in a cohort of children with overweight and (morbid) obesity. Central retinal arteriolar equivalent(CRAE) and central retinal venular equivalent(CRVE) were assessed. CRAE was significantly lower and AVR significantly higher in children with morbid obesity than in children with overweight and normal weight(p < 0.01). CRVE did not differ significantly between the four weight categories. A multiple linear regression model with CRAE as dependent variable showed that only DBP z-score(ß = -2.848,p = 0.029) and plasma glucose concentrations(ß = 6.029,p = 0.019) contributed significantly to the variation in CRAE. Remarkably, despite a correlation between CRAE and circulating concentrations of the adhesion molecules VCAM-1 or ICAM-1, markers for inflammation and endothelial function did not contribute to the variation in CRAE. This is the first study showing in population of children with overweight and obesity that the retinal arteriolar microvasculature, but not venular diameter is aberrant, with increasing BMI z-score. CRAE was significantly associated with several cardiovascular risk markers, and multiple linear regression showed that a higher diastolic blood pressure z-score and lower fasting plasma glucose concentrations significantly contributed to the variance in CRAE.

Effects of different endurance exercise modalities on retinal vessel diameters in unipolar depression.

BACKGROUND: Psychiatric disorders are associated with a high prevalence of cardiovascular disease. Regular exercise is known to reduce depressive symptoms and improve vascular function, in turn lowering cardiovascular risk. We aimed to investigate the effects of different exercise modalities on retinal vessel diameters as a microvascular biomarker and depression severity index in patients suffering from unipolar depression. METHODS: 23 patients (female: 19, male: 4, age: 36.7, Beck-Depression-Inventory-II (BDI-II) score: 30.7) were enrolled in this two-armed randomized controlled trial. Static vessel analysis was performed to obtain central retinal arteriolar (CRAE) and venular (CRVE) diameter equivalents and the arterio-venous diameter ratio (AVR). Maximal bicycle ergometer exercise testing yielded maximal fitness parameters. Patients were assigned to either high intensity low volume (HILV) or moderate continuous aerobic training (MCT). Both intervention groups trained three times a week during a 4-week intervention period. RESULTS: Moderate interaction effects were found for AVR (ɳp2 = 0.12) whereby HILV showed a larger increase in AVR (HILV: pre: 0.89 (0.04), post: 0.91 (0.04), SMD = -0.50) compared to MCT (MCT: pre: 0.85 (0.06), post: 0.86 (0.05), SMD = -0.18). Parallel group trials revealed a 67% possibly beneficial effect of HILV over MCT. Moderate interaction effects on depression severity reduction (ɳp2 = 0.06) were found, whereby the effect size was slightly larger in MCT. CONCLUSION: Both exercise interventions improved AVR as well as BDI-II. HILV may be more effective in improving cerebrovascular health. The exercise-induced effects on retinal vessel diameter changes were relatively small and the clinical relevance remains to be investigated in larger and longer-term exercise trials.

Association of cardiorespiratory fitness with retinal vessel diameters as a biomarker of cardiovascular risk.

OBJECTIVE: We aimed to investigate the association of retinal microvascular health with cardiorespiratory fitness (VO2peak) and cardiovascular risk factors. METHODS: In a population of 260 obesity-enriched participants we investigated the association of retinal vessel diameters with cardiorespiratory fitness (CRF), body mass index (BMI) and blood pressure (BP). Retinal vessel imaging was performed by use of a fundus camera and a semi-automated processing software, calculating the central retinal arteriolar (CRAE) and venular equivalent (CRVE) as well as the arteriolar-to-venular diameter ratio (AVR). RESULTS: Participants had a mean age of 45.8 ±â€¯12.5 years and a BMI of 35.8 ±â€¯6.8 kg/m2. 45% of patients were diagnosed with hypertension, 26% with diabetes and 30% with dyslipidemia. Increasing VO2peak was independently associated with lower CRVE (ß = -0.600; CI -1.141, -0.060; p = 0.030). Higher BMI and mean arterial pressure were independently associated with narrower CRAE (ß = -0.492; CI -0.909, -0.076; p = 0.021 and ß = -0.268; CI -0.471, -0.066; p = 0.009, respectively) and lower AVR (ß = -0.002; CI -0.003, -0.000; p = 0.026 and ß = -0.001; CI -0.002, -0.000; p = 0.001, respectively). CONCLUSIONS: Higher cardiorespiratory fitness is associated with beneficial retinal microvascular health. Higher BMI and BP were associated with an impairment of retinal microvascular health. Exercise is known for its potential to improve body composition and reduce BP but may also prove to be an efficient therapy to counteract small vessel disease in cardiometabolic disease.

Microvascular retinopathy and angiographically-demonstrated coronary artery disease: A cross-sectional, observational study.

Epidemiological studies suggest retinal microvascular abnormalities predict cardiac events. This study examined microvascular features associated with coronary artery abnormalities. This was a single-centre, cross-sectional, observational study of 144 consecutive subjects undergoing coronary angiography for clinical indications. Their angiograms were deidentified and graded for disease (Leaman score, LAD stenosis ≥ 70%, number of vessels stenosed ≥ 70%), and Thrombolysis in Myocardial Infarction (TIMI) blush score. Subjects also underwent retinal photography (KOWA non-mydriatic camera, Japan), and their deidentified retinal images were graded for hypertensive microvascular retinopathy (Wong and Mitchell classification), vessel calibre using a computer-assisted method (IVAN, U Wisconsin), and diabetic retinopathy (modified Airlie House scheme) independently by a trained grader and an ophthalmologist. Retinal abnormalities were compared between subjects with high and low angiography scores using one way ANOVA, Chi squared and logistic regression analysis (StataCorp, Texas). Subjects had a mean age of 61 years (range 32-88), and included 101 males (70%). Seventeen (12%) had Leaman scores > 10.5, 46 (32%) had LAD stenosis, 13 (9%) had ≥ 3 arteries stenosed, and 20 (14%) had TIMI blush scores < 1. Twenty-six subjects (18%) had a retinal hemorrhage, and 115 (74%) a mild or moderate hypertensive retinopathy. Fifty-five (38%) had diabetes, and 24 (17%) a background (n = 20) or proliferative (n = 4) diabetic retinopathy. A retinal hemorrhage (p = 0.046), moderate microvascular retinopathy (p = 0.08) and proliferative diabetic retinopathy (p = 0.04) were all associated with a higher Leaman score. Venular calibre was increased with triple vessel disease (205.7 ± 21.6 µm, and 193.7 ± 22.3 µm in normals, p = 0.03). Diabetic retinopathy correlated with an increased TIMI blush score (p = 0.01). Retinal microvascular imaging warrants further evaluation in identifying the presence, extent and nature of coronary artery disease.

Microvascular Dysfunction Following Multiwalled Carbon Nanotube Exposure Is Mediated by Thrombospondin-1 Receptor CD47.

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) disrupts peripheral microvascular function. Thrombospondin-1 (TSP-1) is highly expressed during lung injury and has been shown to alter microvascular reactivity. It is unclear exactly how TSP-1 exerts effects on vascular function, but we hypothesized that the TSP-1 receptor CD47 may mediate changes in vasodilation. Wildtype (WT) or CD47 knockout (CD47 KO) C57B6/J-background animals were exposed to 50 µg of MWCNT or saline control via pharyngeal aspiration. Twenty-four hours postexposure, intravital microscopy was performed to assess arteriolar dilation and venular leukocyte adhesion and rolling. To assess tissue redox status, electron paramagnetic resonance and NOx measurements were performed, while inflammatory biomarkers were measured via multiplex assay.Vasodilation was impaired in the WT + MWCNT group compared with control (57 ± 9 vs 90 ± 2% relaxation), while CD47 KO animals showed no impairment (108 ± 8% relaxation). Venular leukocyte adhesion and rolling increased by >2-fold, while the CD47 KO group showed no change. Application of the antioxidant apocynin rescued normal leukocyte activity in the WT + MWCNT group. Lung and plasma NOx were reduced in the WT + MWCNT group by 47% and 32%, respectively, while the CD47 KO groups were unchanged from control. Some inflammatory cytokines were increased in the CD47 + MWCNT group only. In conclusion, TSP-1 is an important ligand mediating MWCNT-induced microvascular dysfunction, and CD47 is a component of this dysregulation. CD47 activation likely disrupts nitric oxide (•NO) signaling and promotes leukocyte-endothelial interactions. Impaired •NO production, signaling, and bioavailability is linked to a variety of cardiovascular diseases in which TSP-1/CD47 may play an important role.

Associations between retinal arteriolar and venular calibre with the prevalence of impaired fasting glucose and diabetes mellitus: A cross-sectional study.

BACKGROUND: This study aims to explore retinal vessel calibre in individuals at risk of coronary artery disease (CAD), diagnosed with impaired fasting glucose (IFG) or diabetes mellitus (DM), and whether indices of CAD extent and severity modifies these associations with DM. METHODS: A cross-sectional study was undertaken of 1680 patients presenting to Westmead Hospital (Sydney, Australia) for evaluation of potential CAD. Baseline digital retinal photographs, cardiovascular risk factor measurements, fasting blood tests and self-reported diabetes by patient questionnaire was recorded. Extent and severity of CAD was assessed using Extent and Gensini scores from angiography findings, respectively. Multivariate analysis including age and hypertension was undertaken to assess the association between retinal vessel calibre and IFG or DM. RESULTS: A total of 748 patients were included; 96 (12.8%) and 189 (25.3%), respectively, had IFG or DM (together termed 'hyperglycaemia'). No consistent association between hyperglycaemia and retinal arteriolar calibre was apparent. Wider retinal venular calibre (second and third tertile) carried a significantly higher odds of DM in men only (multivariable-adjusted OR 2.447, p = 0.005; and OR 2.76, p = 0.002; respectively). No equivalent association was apparent in women. This association was marginally significant (p = 0.08) in patients with CAD Extent scores below the median (i.e. less diffuse CAD). Retinal vessel calibre was not associated with impaired fasting glucose. CONCLUSIONS: This study reports a significant association between retinal venular widening and diabetes mellitus in men. This association was marginally stronger among participants with less diffuse CAD.

Downstream Microvascular Thrombosis in Cortical Venules Is an Early Response to Proximal Cerebral Arterial Occlusion.

BACKGROUND: Previous experimental studies have shown that downstream microvascular thromboinflammation is involved in brain damage from acute ischemic stroke. Using intravital microscopy, we investigated and characterized the sequence of downstream microvascular thromboinflammation in an ischemia/reperfusion acute ischemic stroke model. METHODS AND RESULTS: Rats underwent transient monofilament middle cerebral artery (MCA) occlusion. Cerebral microcirculation in the MCA territory was exposed through a craniotomy and analyzed using real-time intravital imaging coupled with laser Doppler interferometry. Leukocytes, platelets, fibrinogen, and blood-brain barrier permeability were analyzed by intravenous injection of fluorescent antibodies and bovine serum albumin. MCA occlusion induced a sudden and profound drop in downstream microvascular blood flow associated with leukocyte margination in the venous compartment. Leukocyte margination fostered fibrinogen deposition and thrombosis in postcapillary venules. Either in venules or arterioles, blood flow was not fully restored after MCA recanalization. Furthermore, venular thrombi persisted despite MCA recanalization, and leukocyte extravasation continued to develop in venules in association with blood-brain barrier disruption. Finally, microhemorrhages were occasionally observed, colocalizing with thrombosed venules characterized by marked leukocyte margination. CONCLUSIONS: We showed that microvascular thrombosis in transient monofilament MCA occlusion and blood-brain barrier disruption are initiated immediately after occlusion and are propagated through the venous compartment in close association with marginating leukocytes. MCA occlusion-induced downstream microvascular thromboinflammation response was responsible for incomplete reperfusion after MCA recanalization and delayed microhemorrhages.

ARTERIAL OXYGEN SATURATION IN NEOVASCULARIZATIONS IN PROLIFERATIVE DIABETIC RETINOPATHY.

PURPOSE: Retinal neovascularizations in proliferative diabetic retinopathy have been proposed to develop from larger retinal venules. However, angiographic evidence suggests that the new vessels may originate from both arterioles and venules, and the vitreous oxygen tension near retinal neovascularizations is similar to that of retinal arterioles. An assessment of the oxygen saturation in neovascularizations may help characterizing the vascular origin of these vessels in proliferative diabetic retinopathy. METHODS: Dual wavelength oximetry was used to study the oxygen saturation in arterioles, venules, and retinal neovascularizations in 40 eyes from 40 patients with proliferative diabetic retinopathy. RESULTS: The oxygen saturation was significantly lower in retinal venules than in arterioles and neovascularizations (P < 0.0001), and after a correction for the influence of vessel diameter, there was no significant difference between the oxygen saturation in retinal arterioles and neovascularizations (P = 0.71). Age at onset and duration of diabetes mellitus contributed significantly to the variation in oxygen saturation of the venules, whereas none of the clinical background parameters contributed to the variation in oxygen saturation in arterioles and neovascularizations. CONCLUSION: The oxygen saturation in retinal neovascularizations in proliferative diabetic retinopathy is similar to that of the arterioles. Neovascularizations may act as shunts to bypass areas of capillary occlusion.

Assessment of Conjunctival Microvascular Hemodynamics in Stages of Diabetic Microvasculopathy.

Diabetes impairs the microcirculation and function of various vital tissues throughout the body. The conjunctival microcirculation can be non-invasively imaged and thus enables assessment of microvascular hemodynamics. In this study, alterations in conjunctival microvascular hemodynamics were quantitatively assessed at stages of increasing diabetic microvasculopathy based on diabetic retinopathy (DR). Subjects were categorized into non-diabetic control (C, N = 34), no clinically visible DR (NDR, N = 47), non-proliferative DR (NPDR, N = 45), and proliferative DR (PDR, N = 35). Conjunctival hemodynamic descriptors, namely vessel diameter (D), blood velocity (V), blood flow (Q), wall shear rate (WSR), and wall shear stress (WSS) were measured in arterioles and venules, and compared between DR and C subjects using generalized linear mixed models. In arterioles, V, WSR, and WSS were lower in NDR (P ≤ 0.01). V was lower in NDR than NPDR and PDR subjects (P ≤ 0.02). In venules, D was higher in NDR and NPDR (P ≤ 0.03), while V was lower in PDR (P = 0.04). Venular V and Q were higher in NPDR than PDR subjects (P ≤ 0.04). WSR and WSS were lower in all stages of DR (P ≤ 0.05), suggestive of the potential of WSS as a marker of diabetic microvasculopathy. Quantitative assessment of conjunctival hemodynamics can potentially be useful for evaluation of diabetic microvasculopathy.