Osteogenesis associates with inflammation in early-stage atherosclerosis evaluated by molecular imaging in vivo

Exercise and Competitive Sport: Physiology, Adaptations, and Uncertain Long-Term Risks

OPINION STATEMENT

The benefits of regular and moderate exercise training on cardiovascular outcomes have been well established. In addition, strenuous exercise training leads to corollary cardiac structural and functional adaptations that are sport-specific and facilitate athletic performance. In this review, the normal physiologic and hemodynamic changes that occur during exercise and the subsequent differential exercise-induced cardiac remodeling patterns that develop will be discussed. Paradoxically, recent data have raised concern about the long-term impact of higher doses of physical activity and exercise on mortality and cardiovascular health outcomes. We will discuss important aspects of these controversial data and review the supporting evidence as well as the limitations of prior research. Specifically, we will address the association between high levels of exercise and relative reductions in overall mortality, increased risk of atrial fibrillation, arrhythmogenic cardiac remodeling, and accelerated coronary artery calcifications. For the practitioner, this review aims to detail these contemporary sports cardiology controversies and highlights the critical need to incorporate shared decision making with the athlete in dealing with the uncertainties that exist. Finally, we will discuss key "athlete-specific" variables that should be considered in the design of future important research in this arena.

Lower limb arterial calcification (LLAC) scores in patients with symptomatic peripheral arterial disease are associated with increased cardiac mortality and morbidity

AIMS

The association of coronary arterial calcification with cardiovascular morbidity and mortality is well-recognized. Lower limb arterial calcification (LLAC) is common in PAD but its impact on subsequent health is poorly described. We aimed to determine the association between a LLAC score and subsequent cardiovascular events in patients with symptomatic peripheral arterial disease (PAD).

METHODS

LLAC scoring, and the established Bollinger score, were derived from a database of unenhanced CT scans, from patients presenting with symptomatic PAD. We determined the association between these scores outcomes. The primary outcome was combined cardiac mortality and morbidity (CM/M) with a secondary outcome of all-cause mortality.

RESULTS

220 patients (66% male; median age 69 years) were included with follow-up for a median 46 [IQR 31-64] months. Median total LLAC scores were higher in those patients suffering a primary outcome (6831 vs. 1652; p = 0.012). Diabetes mellitus (p = 0.039), ischaemic heart disease (p = 0.028), chronic kidney disease (p = 0.026) and all-cause mortality (p = 0.012) were more common in patients in the highest quartile of LLAC scores. The area under the curve of the receiver operator curve for the LLAC score was greater (0.929: 95% CI [0.884-0.974]) than for the Bollinger score (0.824: 95% CI [0.758-0.890]) for the primary outcome. A LLAC score ≥ 4400 had the best diagnostic accuracy to determine the outcome measure.

CONCLUSION

This is the largest study to investigate links between lower limb arterial calcification and cardiovascular events in symptomatic PAD. We describe a straightforward, reproducible, CT-derived measure of calcification-the LLAC score.

A novel fluorescent probe-based flow cytometric assay for mineral-containing nanoparticles in serum

Calciprotein particles, nanoscale aggregates of insoluble mineral and binding proteins, have emerged as potential mediators of phosphate toxicity in patients with Chronic Kidney Disease. Although existing immunochemical methods for their detection have provided compelling data, these approaches are indirect, lack specificity and are subject to a number of other technical and theoretical shortcomings. Here we have developed a rapid homogeneous fluorescent probe-based flow cytometric method for the detection and quantitation of individual mineral-containing nanoparticles in human and animal serum. This method allows the discrimination of membrane-bound from membrane-free particles and different mineral phases (amorphous vs. crystalline). Critically, the method has been optimised for use on a conventional instrument, without the need for manual hardware adjustments. Using this method, we demonstrate a consistency in findings across studies of Chronic Kidney Disease patients and commonly used uraemic animal models. These studies demonstrate that renal dysfunction is associated with the ripening of calciprotein particles to the crystalline state and reveal bone metabolism and dietary mineral as important modulators of circulating levels. Flow cytometric analysis of calciprotein particles may enhance our understanding of mineral handling in kidney disease and provide a novel indicator of therapeutic efficacy for interventions targeting Chronic Kidney Disease-Mineral Bone Disorder.

Silent Monosodium Urate Crystal Deposits Are Associated With Severe Coronary Calcification in Asymptomatic Hyperuricemia: An Exploratory Study

OBJECTIVE

To evaluate the association between monosodium urate (MSU) crystal deposits in patients with asymptomatic hyperuricemia and the severity and extension of coronary artery disease (CAD).

METHODS

In this cross-sectional study, consecutive inpatients with a non-ST elevation acute coronary event and asymptomatic hyperuricemia (serum uric acid concentration of ≥7.0 mg/dl) or normouricemia (serum uric acid concentration of <7.0 mg/dl) were enrolled. In patients with asymptomatic hyperuricemia, the presence of MSU crystals was determined by ultrasound evaluation of both knees and first metatarsophalangeal joints and by compensated polarized light microscopy. CAD was assessed by coronary angiography, and the following variables were considered: 1) the presence of moderate-to-severe coronary artery calcification, 2) the number of significant coronary stenoses, and 3) the presence of multivessel disease. The association between variables indicating the severity of CAD and the presence of MSU crystals was analyzed by multivariate regression.

RESULTS

One hundred forty patients were enrolled. After ultrasonography and microscopic analyses were performed, the patients were classified as having normouricemia (n = 66), asymptomatic hyperuricemia alone (n = 61), and asymptomatic hyperuricemia with MSU crystals (n = 13). The prevalence of moderate-to-severe coronary calcification was significantly higher in the patients with asymptomatic hyperuricemia with MSU crystals compared with patients with asymptomatic hyperuricemia alone and patients with normouricemia (P = 0.003). An independent association was observed between the presence of moderate-to-severe calcification and asymptomatic hyperuricemia with crystals (odds ratio 16.8, P = 0.002). No significant association was observed for the other variables.

CONCLUSION

Silent deposition of MSU crystals in patients with asymptomatic hyperuricemia was associated with more severe coronary calcification, which suggests more severe CAD in relation to crystal deposition.

Pathophysiology of Aortic Stenosis and Mitral Regurgitation

The global impact of the spectrum of valve diseases is a crucial, fast-growing, and underrecognized health problem. The most prevalent valve diseases, requiring surgical intervention, are represented by calcific and degenerative processes occurring in heart valves, in particular, aortic and mitral valve. Due to the increasing elderly population, these pathologies will gain weight in the global health burden. The two most common valve diseases are aortic valve stenosis (AVS) and mitral valve regurgitation (MR). AVS is the most commonly encountered valve disease nowadays and affects almost 5% of elderly population. In particular, AVS poses a great challenge due to the multiple comorbidities and frailty of this patient subset. MR is also a common valve pathology and has an estimated prevalence of 3% in the general population, affecting more than 176 million people worldwide. This review will focus on pathophysiological changes in both these valve diseases, starting from the description of the anatomical aspects of normal valve, highlighting all the main cellular and molecular features involved in the pathological progression and cardiac consequences. This review also evaluates the main approaches in clinical management of these valve diseases, taking into account of the main published clinical guidelines. © 2017 American Physiological Society. Compr Physiol 7:799-818, 2017.

Dynamin-Related Protein 1 Inhibition Attenuates Cardiovascular Calcification in the Presence of Oxidative Stress

RATIONALE

Mitochondrial changes occur during cell differentiation and cardiovascular disease. DRP1 (dynamin-related protein 1) is a key regulator of mitochondrial fission. We hypothesized that DRP1 plays a role in cardiovascular calcification, a process involving cell differentiation and a major clinical problem with high unmet needs.

OBJECTIVE

To examine the effects of osteogenic promoting conditions on DRP1 and whether DRP1 inhibition alters the development of cardiovascular calcification.

METHODS AND RESULTS

DRP1 was enriched in calcified regions of human carotid arteries, examined by immunohistochemistry. Osteogenic differentiation of primary human vascular smooth muscle cells increased DRP1 expression. DRP1 inhibition in human smooth muscle cells undergoing osteogenic differentiation attenuated matrix mineralization, cytoskeletal rearrangement, mitochondrial dysfunction, and reduced type 1 collagen secretion and alkaline phosphatase activity. DRP1 protein was observed in calcified human aortic valves, and DRP1 RNA interference reduced primary human valve interstitial cell calcification. Mice heterozygous for Drp1 deletion did not exhibit altered vascular pathology in a proprotein convertase subtilisin/kexin type 9 gain-of-function atherosclerosis model. However, when mineralization was induced via oxidative stress, DRP1 inhibition attenuated mouse and human smooth muscle cell calcification. Femur bone density was unchanged in mice heterozygous for Drp1 deletion, and DRP1 inhibition attenuated oxidative stress-mediated dysfunction in human bone osteoblasts.

CONCLUSIONS

We demonstrate a new function of DRP1 in regulating collagen secretion and cardiovascular calcification, a novel area of exploration for the potential development of new therapies to modify cellular fibrocalcific response in cardiovascular diseases. Our data also support a role of mitochondrial dynamics in regulating oxidative stress-mediated arterial calcium accrual and bone loss.

Interferon-γ Released by Activated CD8+ T Lymphocytes Impairs the Calcium Resorption Potential of Osteoclasts in Calcified Human Aortic Valves

In calcific aortic valve disease (CAVD), activated T lymphocytes localize with osteoclast regions; however, the functional consequences of this association remain unknown. We hypothesized that CD8+ T cells modulate calcification in CAVD. CAVD valves (n = 52) dissected into noncalcified and calcified portions were subjected to mRNA extraction, real-time quantitative PCR, enzyme-linked immunosorbent assay, and immunohistochemical analyses. Compared with noncalcified portions, calcified regions exhibited elevated transcripts for CD8, interferon (IFN)-γ, CXCL9, Perforin 1, Granzyme B, and heat shock protein 60. Osteoclast-associated receptor activator of NK-κB ligand (RANKL), tartrate-resistant acid phosphatase (TRAP), and osteoclast-associated receptor increased significantly. The stimulation of tissue with phorbol-12-myristate-13-acetate and ionomycin, recapitulating CAVD microenvironment, resulted in IFN-γ release. Real-time quantitative PCR detected mRNAs for CD8+ T-cell activation (Perforin 1, Granzyme B). In stimulated versus unstimulated organoid cultures, elevated IFN-γ reduced the mRNAs encoding for RANKL, TRAP, and Cathepsin K. Molecular imaging showed increased calcium signal intensity in stimulated versus unstimulated parts. CD14+ monocytes treated either with recombinant human IFN-γ or with conditioned media-derived IFN-γ exhibited low levels of Cathepsin K, TRAP, RANK, and tumor necrosis factor receptor-associated factor 6 mRNAs, whereas concentrations of the T-cell co-activators CD80 and CD86 increased in parallel with reduced osteoclast resorptive function, effects abrogated by neutralizing anti-IFN-γ antibodies. CD8+ cell-derived IFN-γ suppresses osteoclast function and may thus favor calcification in CAVD.

Imaging Atherosclerotic Plaque Calcification: Translating Biology

Calcification of atherosclerotic lesions was long thought to be an age - related, passive process, but increasingly data has revealed that atherosclerotic calcification is a more active process, involving complex signaling pathways and bone-like genetic programs. Initially, imaging of atherosclerotic calcification was limited to gross assessment of calcium burden, which is associated with total atherosclerotic burden and risk of cardiovascular mortality and of all cause mortality. More recently, sophisticated molecular imaging studies of the various processes involved in calcification have begun to elucidate information about plaque calcium composition and consequent vulnerability to rupture, leading to hard cardiovascular events like myocardial infarction. As such, there has been renewed interest in imaging calcification to advance risk assessment accuracy in an evolving era of precision medicine. Here we summarize recent advances in our understanding of the biologic process of atherosclerotic calcification as well as some of the molecular imaging tools used to assess it.

Noninvasive Molecular Imaging of Disease Activity in Atherosclerosis

Major focus has been placed on the identification of vulnerable plaques as a means of improving the prediction of myocardial infarction. However, this strategy has recently been questioned on the basis that the majority of these individual coronary lesions do not in fact go on to cause clinical events. Attention is, therefore, shifting to alternative imaging modalities that might provide a more complete pan-coronary assessment of the atherosclerotic disease process. These include markers of disease activity with the potential to discriminate between patients with stable burnt-out disease that is no longer metabolically active and those with active atheroma, faster disease progression, and increased risk of infarction. This review will examine how novel molecular imaging approaches can provide such assessments, focusing on inflammation and microcalcification activity, the importance of these processes to coronary atherosclerosis, and the advantages and challenges posed by these techniques.

18F-Fluoride and 18F-Fluorodeoxyglucose Positron Emission Tomography After Transient Ischemic Attack or Minor Ischemic Stroke: Case-Control Study

Supplemental Digital Content is available in the text.

Background—

Combined positron emission tomography (PET) and computed tomography (CT) can assess both anatomy and biology of carotid atherosclerosis. We sought to assess whether ¹⁸F-fluoride or ¹⁸F-fluorodeoxyglucose can identify culprit and high-risk carotid plaque.

Methods and Results—

We performed ¹⁸F-fluoride and ¹⁸F-fluorodeoxyglucose PET/CT in 26 patients after recent transient ischemic attack or minor ischemic stroke: 18 patients with culprit carotid stenosis awaiting carotid endarterectomy and 8 controls without culprit carotid atheroma. We compared standardized uptake values in the clinically adjudicated culprit to the contralateral asymptomatic artery, and assessed the relationship between radiotracer uptake and plaque phenotype or predicted cardiovascular risk (ASSIGN score [Assessing Cardiovascular Risk Using SIGN Guidelines to Assign Preventive Treatment]). We also performed micro PET/CT and histological analysis of excised plaque. On histological and micro PET/CT analysis, ¹⁸F-fluoride selectively highlighted microcalcification. Carotid ¹⁸F-fluoride uptake was increased in clinically adjudicated culprit plaques compared with asymptomatic contralateral plaques (log₁₀standardized uptake value_mean 0.29±0.10 versus 0.23±0.11, P=0.001) and compared with control patients (log₁₀standardized uptake value_mean 0.29±0.10 versus 0.12±0.11, P=0.001). ¹⁸F-Fluoride uptake correlated with high-risk plaque features (remodeling index [r=0.53, P=0.003], plaque burden [r=0.51, P=0.004]), and predicted cardiovascular risk [r=0.65, P=0.002]). Carotid ¹⁸F-fluorodeoxyglucose uptake appeared to be increased in 7 of 16 culprit plaques, but no overall differences in uptake were observed in culprit versus contralateral plaques or control patients. However, ¹⁸F-fluorodeoxyglucose did correlate with predicted cardiovascular risk (r=0.53, P=0.019), but not with plaque phenotype.

Conclusions—

¹⁸F-Fluoride PET/CT highlights culprit and phenotypically high-risk carotid plaque. This has the potential to improve risk stratification and selection of patients who may benefit from intervention.

18F-sodium fluoride positron emission tomography for molecular imaging of coronary atherosclerosis based on computed tomography analysis

BACKGROUND AND AIMS

We aimed at evaluating the relation of ¹⁸F-sodium fluoride (¹⁸F-NaF) uptake on positron emission tomography (PET) to coronary atherosclerosis detected and assessed by computed tomography (CT).

METHODS

Thirty-two patients with one or more coronary atherosclerotic lesions detected on cardiac CT underwent ¹⁸F-NaF PET/CT. Each coronary atherosclerotic lesion was evaluated on CT angiography for plaque types (calcified plaque [CP], non-calcified plaque [NCP], partially calcified plaque [PCP]), and the presence of CT-based high-risk features (minimum CT density <30 Hounsfield units and vascular remodeling index >1.1). Focal ¹⁸F-NaF uptake of each lesion was quantified using maximum tissue-to-background ratio (TBR_max).

RESULTS

A total of 111 lesions were studied. In a patient-based analysis, logarithmically transformed coronary calcium score correlated positively with maximum TBR_max per patient, and 15 patients with myocardial infarction or unstable angina history showed a higher maximum TBR_max per patient than those without (1.36 ± 0.15 versus 1.15 ± 0.15, p = 0.0006). In a lesion-based analysis, PCP showed a higher TBR_max than CP and NCP (1.17 ± 0.19 versus 1.00 ± 0.24 and 0.92 ± 0.18, respectively, p < 0.0001), and the lesions with high-risk features had a higher TBR_max than those without (1.20 ± 0.21 versus 1.02 ± 0.20, p = 0.0011).

CONCLUSIONS

Coronary arterial ¹⁸F-NaF uptake is related to total plaque burden, coronary event history, and specific features of coronary atherosclerosis based on CT analysis. ¹⁸F-NaF PET/CT, in combination with cardiac CT, may provide a new molecular imaging approach to identify high-risk patients and coronary atherosclerotic lesions.

Altered MicroRNA Expression Is Responsible for the Pro-Osteogenic Phenotype of Interstitial Cells in Calcified Human Aortic Valves

BACKGROUND

The transition of aortic valve interstitial cells (AVICs) to myofibroblastic and osteoblast-like phenotypes plays a critical role in calcific aortic valve disease progression. Several microRNAs (miRs) are implicated in stem cell differentiation into osteoblast. We hypothesized that an epigenetic mechanism regulates valvular pro-osteogenic activity. This study examined miR profile in AVICs of calcified valves and identified miRs responsible for AVIC phenotypic transition.

METHODS AND RESULTS

AVICs were isolated from normal and diseased valves. The miR microarray analysis revealed 14 upregulated and 12 downregulated miRs in diseased AVICs. Increased miR-486 and decreased miR-204 levels were associated with higher levels of myofibroblastic biomarker α-smooth muscle actin and osteoblastic biomarkers runt-related transcription factor 2 (Runx2) and osterix (Osx). Cotransfection of miR-486 antagomir and miR-204 mimic in diseased AVICs reduced their ability to express Runx2 and Osx. The miR-486 mimic upregulated α-smooth muscle actin expression in normal AVICs through the protein kinase B pathway and moderately elevated Runx2 and Osx levels. Knockdown of α-smooth muscle actin attenuated Runx2 and Osx expression induced by miR-486. The miR-486 mimic and miR-204 antagomir synergistically promoted Runx2 and Osx expression and calcium deposition in normal AVICs and normal aortic valve tissue.

CONCLUSIONS

In AVICs of calcified valves, increased levels of miR-486 induce myofibroblastic transition to upregulate Runx2 and Osx expression and synergize with miR-204 deficiency to elevate cellular and valvular pro-osteogenic activity. These novel findings indicate that modulation of the epigenetic mechanism underlying valvular pro-osteogenic activity has therapeutic potential for prevention of calcific aortic valve disease progression.

Quantification of temporal changes in calcium score in active atherosclerotic plaque in major vessels by 18F-sodium fluoride PET/CT

PURPOSE

Our aim was to assess whether ¹⁸F-NaF PET/CT is able to predict progression of the CT calcium score.

METHODS

Between August 2007 and November 2015, 34 patients (18 women, 16 men; age, mean ± standard deviation, 57.5 ± 13.9 years; age range 19-78 years) with malignancy or orthopaedic disease were enrolled in this study, with approximately 1-year follow-up data. Baseline and follow-up CT images were retrospectively evaluated for the presence of calcification sites in major vessel walls. The maximum and mean CT values (CTmax and CTmean, in Hounsfield units), calcification volumetric score (CVS, in cubic millimetres) and Agatston units score (AU) were evaluated for each site. Subsequent changes in CTmax, CTmean, CVS and AU were calculated and expressed as ΔCTmax, ΔCTmean, ΔCVS and ΔAU, respectively. We then evaluated the relationship between ¹⁸F-NaF uptake (using the maximum target-to-background ratio, TBRmax, and the maximum blood-subtracted ¹⁸F-NaF activity, bsNaFmax, which was obtained by subtracting the SUVmax of each calcified plaque lesion and NaF-avid site from the SUVmean in the right atrium blood pool) and the change in calcified plaque volume and characteristics obtained after 1 year.

RESULTS

We detected and analysed 182 calcified plaque sites and 96 hot spots on major vessel walls. ¹⁸F-NaF uptake showed very weak correlations with CTmax, CTmean, CVS, CVS after 1 year, AU and AU after 1 year on both baseline and follow-up PET/CT scans for each site. ¹⁸F-NaF uptake showed no correlation with ΔCTmax or ΔCTmean. However, there was a significant correlation between the intensity of ¹⁸F-NaF uptake and ΔCVS and ΔAU.

CONCLUSION

¹⁸F-NaF uptake has a strong correlation with calcium score progression which was a predictor of future cardiovascular disease risk. PET/CT using ¹⁸F-NaF may be able to predict calcium score progression which is known to be the major characteristic of atherosclerosis.

Serum Sortilin Associates With Aortic Calcification and Cardiovascular Risk in Men

OBJECTIVE

Genome-wide association studies and preclinical studies demonstrated a role of sortilin in lipid metabolism, inflammation, and vascular calcification-all cardiovascular risk factors. We evaluated the association of serum sortilin levels with the risk of major adverse cerebrovascular and cardiovascular events (MACCE) and the severity of abdominal aortic calcification (AAC).

APPROACH AND RESULTS

A cohort of community-dwelling men aged ≥50 years (n=830) was assessed. At baseline, sortilin levels were measured by ELISA, and AAC was assessed on lateral spine scans obtained by dual-energy X-ray absorptiometry. Men aged ≥60 years (n=745) were followed up prospectively for the incidence of MACCE. During the median follow-up of 7.9 years, 76 MACCE occurred. The unadjusted incidence of MACCE across increasing sortilin quartiles was 8.0, 7.4, 19.8, and 20.3 per 1000 person-years. In multivariate-adjusted analysis, sortilin associated with increased risk of MACCE (hazard ratio, 1.70 per SD; 95% confidence interval, 1.30-2.20; P<0.001). The third and fourth quartiles associated with 3.42-fold (95% confidence interval, 1.61-7.25; P<0.005) and 3.82-fold (95% confidence interval, 1.77-8.26; P<0.001) higher risk of MACCE compared with the first quartile. High sortilin also predicted MACCE independent of traditional Framingham risk factors. Higher sortilin associated with higher odds of severe AAC (score>5) after adjustment for confounders (odds ratio, 1.43 per SD; 95% confidence interval, 1.10-1.85; P<0.01). The highest sortilin quartile associated with 2-fold higher odds of severe AAC (versus 3 lower quartiles combined). After adjustment for low-density lipoprotein cholesterol, the odds of severe AAC remained significant.

CONCLUSIONS

In older men, higher serum sortilin levels associated with higher MACCE risk and severe AAC independently of relevant confounders, including C-reactive protein and low-density lipoprotein cholesterol. This finding, however, needs to be validated in other cohorts.

Hyperphosphatemia and hs-CRP Initiate the Coronary Artery Calcification in Peritoneal Dialysis Patients

Background. Coronary artery calcification (CAC) contributes to high risk of cardiocerebrovascular diseases in dialysis patients. However, the risk factors for CAC initiation in peritoneal dialysis (PD) patients are not known clearly. Methods. Adult patients with baseline CaCS = 0 and who were followed up for at least 3 years or until the conversion from absent to any measurable CAC detected were included in this observational cohort study. Binary logistic regression was performed to identify the risk factors for CAC initiation in PD patients. Results. 70 patients recruited to our study were split into a noninitiation group (n = 37) and an initiation group (n = 33) according to the conversion of any measurable CAC during their follow-up or not. In univariate analysis, systolic blood pressure, serum phosphorus, fibrinogen, hs-CRP, serum creatinine, and triglycerides were positively associated with the initiation of CAC, while the high density lipoprotein and nPCR did the opposite function. Multivariate analysis revealed that hyperphosphatemia and hs-CRP were the independent risk factors for CAC initiation after adjustments. Conclusions. Hyperphosphatemia and hs-CRP were the independent risk factors for CAC initiation in PD patients. These results suggested potential clinical strategies to prevent the initiation of CAC in PD patients.

Molecular Imaging of Atherosclerosis: A Clinical Focus

Molecular imaging of cardiovascular disease is a powerful clinical and experimental approach that can inform our understanding of atherosclerosis biology. Complementing cross-sectional imaging techniques that provide detailed anatomical information, molecular imaging can further detect important biological changes occurring within atheroma, and refine the prediction of vascular complications. In addition, molecular imaging of atherosclerosis can illuminate underlying pathophysiology and serve as a surrogate end-point in clinical trials of new drugs. This review showcases promising molecular approaches for imaging atherosclerosis, with a focus on PET, MRI, and intravascular near-infrared fluorescence (NIRF) imaging methods that are in the clinic or close-to-clinical usage.

Rac2 Modulates Atherosclerotic Calcification by Regulating Macrophage Interleukin-1β Production

OBJECTIVE

The calcium composition of atherosclerotic plaque is thought to be associated with increased risk for cardiovascular events, but whether plaque calcium itself is predictive of worsening clinical outcomes remains highly controversial. Inflammation is likely a key mediator of vascular calcification, but immune signaling mechanisms that promote this process are minimally understood.

APPROACH AND RESULTS

Here, we identify Rac2 as a major inflammatory regulator of signaling that directs plaque osteogenesis. In experimental atherogenesis, Rac2 prevented progressive calcification through its suppression of Rac1-dependent macrophage interleukin-1β (IL-1β) expression, which in turn is a key driver of vascular smooth muscle cell calcium deposition by its ability to promote osteogenic transcriptional programs. Calcified coronary arteries from patients revealed decreased Rac2 expression but increased IL-1β expression, and high coronary calcium burden in patients with coronary artery disease was associated with significantly increased serum IL-1β levels. Moreover, we found that elevated IL-1β was an independent predictor of cardiovascular death in those subjects with high coronary calcium burden.

CONCLUSIONS

Overall, these studies identify a novel Rac2-mediated regulation of macrophage IL-1β expression, which has the potential to serve as a powerful biomarker and therapeutic target for atherosclerosis.

PET Imaging of Atherosclerotic Disease: Advancing Plaque Assessment from Anatomy to Pathophysiology

Atherosclerosis is a leading cause of morbidity and mortality. It is now widely recognized that the disease is more than simply a flow-limiting process and that the atheromatous plaque represents a nidus for inflammation with a consequent risk of plaque rupture and atherothrombosis, leading to myocardial infarction or stroke. However, widely used conventional clinical imaging techniques remain anatomically focused, assessing only the degree of arterial stenosis caused by plaques. Positron emission tomography (PET) has allowed the metabolic processes within the plaque to be detected and quantified directly. The increasing armory of radiotracers has facilitated the imaging of distinct metabolic aspects of atherogenesis and plaque destabilization, including macrophage-mediated inflammatory change, hypoxia, and microcalcification. This imaging modality has not only furthered our understanding of the disease process in vivo with new insights into mechanisms but has also been utilized as a non-invasive endpoint measure in the development of novel treatments for atherosclerotic disease. This review provides grounding in the principles of PET imaging of atherosclerosis, the radioligands in use and in development, its research and clinical applications, and future developments for the field.

TNAP stimulates vascular smooth muscle cell trans-differentiation into chondrocytes through calcium deposition and BMP-2 activation: Possible implication in atherosclerotic plaque stability

Atherosclerotic plaque calcification varies from early, diffuse microcalcifications to a bone-like tissue formed by endochondral ossification. Recently, a paradigm has emerged suggesting that if the bone metaplasia stabilizes the plaques, microcalcifications are harmful. Tissue-nonspecific alkaline phosphatase (TNAP), an ectoenzyme necessary for mineralization by its ability to hydrolyze inorganic pyrophosphate (PP_i), is stimulated by inflammation in vascular smooth muscle cells (VSMCs). Our objective was to determine the role of TNAP in trans-differentiation of VSMCs and calcification. In rodent MOVAS and A7R5 VSMCs, addition of exogenous alkaline phosphatase (AP) or TNAP overexpression was sufficient to stimulate the expression of several chondrocyte markers and induce mineralization. Addition of exogenous AP to human mesenchymal stem cells cultured in pellets also stimulated chondrogenesis. Moreover, TNAP inhibition with levamisole in mouse primary chondrocytes dropped mineralization as well as the expression of chondrocyte markers. VSMCs trans-differentiated into chondrocyte-like cells, as well as primary chondrocytes, used TNAP to hydrolyze PP_i, and PP_i provoked the same effects as TNAP inhibition in primary chondrocytes. Interestingly, apatite crystals, associated or not to collagen, mimicked the effects of TNAP on VSMC trans-differentiation. AP and apatite crystals increased the expression of BMP-2 in VSMCs, and TNAP inhibition reduced BMP-2 levels in chondrocytes. Finally, the BMP-2 inhibitor noggin blocked the rise in aggrecan induced by AP in VSMCs, suggesting that TNAP induction in VSMCs triggers calcification, which stimulates chondrogenesis through BMP-2. Endochondral ossification in atherosclerotic plaques may therefore be induced by crystals, probably to confer stability to plaques with microcalcifications.

Cigarette Smoking-Induced Cardiac Hypertrophy, Vascular Inflammation and Injury Are Attenuated by Antioxidant Supplementation in an Animal Model

Background: Cardiovascular diseases are the leading causes of morbidity and mortality worldwide. Cigarette smoking remains a global health epidemic with associated detrimental effects on the cardiovascular system. In this work, we investigated the effects of cigarette smoke exposure on cardiovascular system in an animal model. The study then evaluated the effects of antioxidants (AO), represented by pomegranate juice, on cigarette smoke induced cardiovascular injury. This study aims at evaluating the effect of pomegranate juice supplementation on the cardiovascular system of an experimental rat model of smoke exposure.

Methods: Adult rats were divided into four different groups: Control, Cigarette smoking (CS), AO, and CS + AO. Cigarette smoke exposure was for 4 weeks (5 days of exposure/week) and AO group received pomegranate juice while other groups received placebo. Assessment of cardiovascular injury was documented by assessing different parameters of cardiovascular injury mediators including: (1) cardiac hypertrophy, (2) oxidative stress, (3) expression of inflammatory markers, (4) expression of Bradykinin receptor 1 (Bdkrb1), Bradykinin receptor 2 (Bdkrb2), and (5) altered expression of fibrotic/atherogenic markers [(Fibronectin (Fn1) and leptin receptor (ObR))].

Results: Data from this work demonstrated that cigarette smoke exposure induced cardiac hypertrophy, which was reduced upon administration of pomegranate in CS + AO group. Cigarette smoke exposure was associated with elevation in oxidative stress, significant increase in the expression of IL-1β, TNFα, Fn1, and ObR in rat's aorta. In addition, an increase in aortic calcification was observed after 1 month of cigarette smoke exposure. Furthermore, cigarette smoke induced a significant up regulation in Bdkrb1 expression level. Finally, pomegranate supplementation exhibited cardiovascular protection assessed by the above findings and partly contributed to ameliorating cardiac hypertrophy in cigarette smoke exposed animals.

Conclusion: Findings from this work showed that cigarette smoking exposure is associated with significant cardiovascular pathology such as cardiac hypertrophy, inflammation, pro-fibrotic, and atherogenic markers and aortic calcification in an animal model as assessed 1 month post exposure. Antioxidant supplementation prevented cardiac hypertrophy and attenuated indicators of atherosclerosis markers associated with cigarette smoke exposure.

Activating transcription factor-4 promotes mineralization in vascular smooth muscle cells

Emerging evidence indicates that upregulation of the ER stress-induced pro-osteogenic transcription factor ATF4 plays an important role in vascular calcification, a common complication in patients with aging, diabetes, and chronic kidney disease (CKD). In this study, we demonstrated the pathophysiological role of ATF4 in vascular calcification using global Atf4 KO, smooth muscle cell-specific (SMC-specific) Atf4 KO, and transgenic (TG) mouse models. Reduced expression of ATF4 in global ATF4-haplodeficient and SMC-specific Atf4 KO mice reduced medial and atherosclerotic calcification under normal kidney and CKD conditions. In contrast, increased expression of ATF4 in SMC-specific Atf4 TG mice caused severe medial and atherosclerotic calcification. We further demonstrated that ATF4 transcriptionally upregulates the expression of type III sodium-dependent phosphate cotransporters (PiT1 and PiT2) by interacting with C/EBPβ. These results demonstrate that the ER stress effector ATF4 plays a critical role in the pathogenesis of vascular calcification through increased phosphate uptake in vascular SMCs.

Policosanol as a new inhibitor candidate for vascular calcification in diabetic hyperlipidemic rats

This work mainly aimed to investigate the probable changes of aortic calcification by policosanol, omega-3 fatty acids in comparison with atorvastatin and subsequent progression of atherosclerosis in diabetic hyperlipemic rat model. Adult male albino rats of wistar strain (30) were divided into five groups (n = 6/group); one was fed normal diet and was used as a normal group, the other groups received alloxan, atherogenic diet (CCT - rat chow diet supplemented with 4% cholesterol, 1% cholic acid, and 0.5% thiouracil) and categorized as follows: the second group received no treatment and kept as control (diabetic hyperlipidemic control group (DHC)). The other groups received daily oral doses of atorvastatin, policosanol (10 mg/kg body weight) and ω-3 (50 mg/kg body weight), respectively, for eight weeks. Different biomarkers were used for the evaluation that included inflammatory (C reactive protein (CRP), tumor necrosis factor α (TNF-α)), oxidative stress (glutathione (GSH), malondialdehyde (MDA)) bone calcification markers (alkaline phosphatase (ALP), Vitamin D, parathyroid hormone (PTH)), lipogram pattern in addition to histochemical demonstration of calcium in the aorta. Diabetic hyperlipemic group demonstrated significant hyperglycemia, hyperlipidemia, and increased inflammation, oxidative stress, calcification, and finally atherogenesis progression. Treatment of diabetic hyperlipemic rats with, policosanol, omega-3 fatty acids (natural products) and atorvastatin for eight weeks significantly increased high-density lipoprotein cholesterol (HDL-C), Vitamin D, decreased aortic vacuoles number, and inhibited calcification process. Policosanol induced more remarkable reduction in the density and number of foam cells and improved the intimal lesions of the aorta as compared to atorvastatin. Drugs under study exerted hypoglycemic effect along with an inhibition of inflammation, oxidative stress, and calcium deposition with certain variations but policosanol effect was remarkable in comparison with other drugs.

Fast-degrading bioresorbable arterial vascular graft with high cellular infiltration inhibits calcification of the graft

OBJECTIVE

Bioresorbable vascular grafts are biologically active grafts that are entirely reconstituted by host-derived cells through an inflammation-mediated degradation process. Calcification is a detrimental condition that can severely affect graft performance. Therefore, prevention of calcification is of great importance to the success of bioresorbable arterial vascular grafts. The objective of this study was to test whether fast-degrading (FD) bioresorbable arterial grafts with high cellular infiltration will inhibit calcification of grafts.

METHODS

We created two versions of bioresorbable arterial vascular grafts, slow-degrading (SD) grafts and FD grafts. Both grafts had the same inner layer composed of a 50:50 poly(l-lactic-co-ε-caprolactone) copolymer scaffold. However, the outer layer of SD grafts was composed of poly(l-lactic acid) nanofiber, whereas the outer layer of FD grafts was composed of a combination of poly(l-lactic acid) and polyglycolic acid nanofiber. Both grafts were implanted in 8- to 10-week-old female mice (n = 15 in the SD group, n = 10 in the FD group) as infrarenal aortic interposition conduits. Animals were observed for 8 weeks.

RESULTS

von Kossa staining showed calcification in 7 of 12 grafts in the SD group but zero in the FD group (P < .01, χ² test). The cell number in the outer layer of FD grafts was significantly higher than in the SD grafts (SD, 0.87 ± 0.65 × 10³/mm²; FD, 2.65 ± 1.91 × 10³/mm²; P = .02).

CONCLUSIONS

The FD bioresorbable arterial vascular graft with high cellular infiltration into the scaffold inhibited calcification of grafts.

Molecular Imaging of Vulnerable Atherosclerotic Plaques in Animal Models

Atherosclerosis is characterized by intimal plaques of the arterial vessels that develop slowly and, in some cases, may undergo spontaneous rupture with subsequent heart attack or stroke. Currently, noninvasive diagnostic tools are inadequate to screen atherosclerotic lesions at high risk of acute complications. Therefore, the attention of the scientific community has been focused on the use of molecular imaging for identifying vulnerable plaques. Genetically engineered murine models such as ApoE^−/− and ApoE^−/−Fbn1C1039G^+/− mice have been shown to be useful for testing new probes targeting biomarkers of relevant molecular processes for the characterization of vulnerable plaques, such as vascular endothelial growth factor receptor (VEGFR)-1, VEGFR-2, intercellular adhesion molecule (ICAM)-1, P-selectin, and integrins, and for the potential development of translational tools to identify high-risk patients who could benefit from early therapeutic interventions. This review summarizes the main animal models of vulnerable plaques, with an emphasis on genetically altered mice, and the state-of-the-art preclinical molecular imaging strategies.

Adventitial MSC-like Cells Are Progenitors of Vascular Smooth Muscle Cells and Drive Vascular Calcification in Chronic Kidney Disease

Mesenchymal stem cell (MSC)-like cells reside in the vascular wall, but their role in vascular regeneration and disease is poorly understood. Here, we show that Gli1⁺ cells located in the arterial adventitia are progenitors of vascular smooth muscle cells and contribute to neointima formation and repair after acute injury to the femoral artery. Genetic fate tracing indicates that adventitial Gli1⁺ MSC-like cells migrate into the media and neointima during athero- and arteriosclerosis in ApoE^-/- mice with chronic kidney disease. Our data indicate that Gli1⁺ cells are a major source of osteoblast-like cells during calcification in the media and intima. Genetic ablation of Gli1⁺ cells before induction of kidney injury dramatically reduced the severity of vascular calcification. These findings implicate Gli1⁺ cells as critical adventitial progenitors in vascular remodeling after acute and during chronic injury and suggest that they may be relevant therapeutic targets for mitigation of vascular calcification.

Clinical Utility and Future Applications of PET/CT and PET/CMR in Cardiology

Over the past several years, there have been major advances in cardiovascular positron emission tomography (PET) in combination with either computed tomography (CT) or, more recently, cardiovascular magnetic resonance (CMR). These multi-modality approaches have significant potential to leverage the strengths of each modality to improve the characterization of a variety of cardiovascular diseases and to predict clinical outcomes. This review will discuss current developments and potential future uses of PET/CT and PET/CMR for cardiovascular applications, which promise to add significant incremental benefits to the data provided by each modality alone.

Mechanically resilient, injectable, and bioadhesive supramolecular gelatin hydrogels crosslinked by weak host-guest interactions assist cell infiltration and in situ tissue regeneration

Although considered promising materials for assisting organ regeneration, few hydrogels meet the stringent requirements of clinical translation on the preparation, application, mechanical property, bioadhesion, and biocompatibility of the hydrogels. Herein, we describe a facile supramolecular approach for preparing gelatin hydrogels with a wide array of desirable properties. Briefly, we first prepare a supramolecular gelatin macromer via the efficient host-guest complexation between the aromatic residues of gelatin and free diffusing photo-crosslinkable acrylated β-cyclodextrin (β-CD) monomers. The subsequent crosslinking of the macromers produces highly resilient supramolecular gelatin hydrogels that are solely crosslinked by the weak host-guest interactions between the gelatinous aromatic residues and β-cyclodextrin (β-CD). The obtained hydrogels are capable of sustaining excessive compressive and tensile strain, and they are capable of quick self healing after mechanical disruption. These hydrogels can be injected in the gelation state through surgical needles and re-molded to the targeted geometries while protecting the encapsulated cells. Moreover, the weak host-guest crosslinking likely facilitate the infiltration and migration of cells into the hydrogels. The excess β-CDs in the hydrogels enable the hydrogel-tissue adhesion and enhance the loading and sustained delivery of hydrophobic drugs. The cell and animal studies show that such hydrogels support cell recruitment, differentiation, and bone regeneration, making them promising carrier biomaterials of therapeutic cells and drugs via minimally invasive procedures.

Future imaging of atherosclerosis: molecular imaging of coronary atherosclerosis with (18)F positron emission tomography

Atherosclerosis is characterized by the formation of complex atheroma lesions (plaques) in arteries that pose risk by their flow-limiting nature and propensity for rupture and thrombotic occlusion. It develops in the context of disturbances to lipid metabolism and immune response, with inflammation underpinning all stages of plaque formation, progression and rupture. As the primary disease process responsible for myocardial infarction, stroke and peripheral vascular disease, atherosclerosis is a leading cause of morbidity and mortality on a global scale. A precise understanding of its pathogenic mechanisms is therefore critically important. Integral to this is the role of vascular wall imaging. Over recent years, the rapidly evolving field of molecular imaging has begun to revolutionize our ability to image beyond just the anatomical substrate of vascular disease, and more dynamically assess its pathobiology. Nuclear imaging by positron emission tomography (PET) can target specific molecular and biological pathways involved in atherosclerosis, with the application of (18)Fluoride PET imaging being widely studied for its potential to identify plaques that are vulnerable or high risk. In this review, we discuss the emergence of (18)Fluoride PET as a promising modality for the assessment of coronary atherosclerosis, focusing on the strengths and limitations of the two main radionuclide tracers that have been investigated to date: 2-deoxy-2-((18)F)fluoro-D-glucose ((18)F-FDG) and sodium (18)F-fluoride ((18)F-NaF).

A single injection of gain-of-function mutant PCSK9 adeno-associated virus vector induces cardiovascular calcification in mice with no genetic modification

BACKGROUND AND AIMS

Studying atherosclerotic calcification in vivo requires mouse models with genetic modifications. Previous studies showed that injection of recombinant adeno-associated virus vector (AAV) encoding a gain-of-function mutant PCSK9 into mice promotes atherosclerosis. We aimed to study cardiovascular calcification induced by PCSK9 AAV in C57BL/6J mice.

METHODS

10 week-old C57BL/6J mice received a single injection of AAV encoding mutant mPCSK9 (rAAV8/D377Y-mPCSK9). Ldlr(-/-) mice served as positive controls. Mice consumed a high-fat, high-cholesterol diet for 15 or 20 weeks. Aortic calcification was assessed by fluorescence reflectance imaging (FRI) of a near-infrared calcium tracer.

RESULTS

Serum levels of PCSK9 (0.14 μg/mL to 20 μg/mL, p < 0.01) and total cholesterol (82 mg/dL to 820 mg/dL, p < 0.01) increased within one week after injection and remained elevated for 20 weeks. Atherosclerotic lesion size was similar between PCSK9 AAV and Ldlr(-/-) mice. Aortic calcification was 0.01% ± 0.01 in PCSK9 AAV mice and 15.3% ± 6.1 in Ldlr(-/-) mice at 15 weeks (p < 0.01); by 20 weeks, the PCSK9 AAV mice aortic calcification grew to 12.4% ± 4.9. Tissue non-specific alkaline phosphatase activity was similar in PCSK9 AAV mice and Ldlr(-/-) mice at 15 and 20 weeks, respectively. As example of the utility of this model in testing modulators of calcification in vivo, PCSK9 AAV injection to sortilin-deficient mice demonstrated reduced aortic calcification by 46.3% (p < 0.05) compared to littermate controls.

CONCLUSIONS

A single injection of gain-of-function PCSK9 AAV into C57BL/6J mice is a useful tool to study cardiovascular calcification in mice with no genetic manipulation.

Increase in Dye:Dendrimer Ratio Decreases Cellular Uptake of Neutral Dendrimers in RAW Cells

Neutral generation 3 poly(amidoamine) dendrimers were labeled with Oregon Green 488 (G3-OG_n) to obtain materials with controlled fluorophore:dendrimer ratios (n = 1-2), a mixture containing mostly 3 dyes per dendrimer, a mixture containing primarily 4 or more dyes per dendrimer (n = 4+), and a stochastic mixture (n = 4_avg). The UV absorbance of the dye conjugates increased linearly as n increased and the fluorescence emission decreased linearly as n increased. Cellular uptake was studied in RAW cells and HEK 293A cells as a function of the fluorophore:dendrimer ratio (n). The cellular uptake of G3-OG _n (n = 3, 4+, 4_avg) into RAW cells was significantly lower than G3-OG _n (n = 1, 2). The uptake of G3-OG _n (n = 3, 4+, 4_avg) into HEK 293A cells was not significantly different from G3-OG₁. Thus, the fluorophore:dendrimer ratio was observed to change the extent of uptake in the macrophage uptake mechanism but not in the HEK 293A cell. This difference in endocytosis indicates the presence of a pathway in the macrophage that is sensitive to hydrophobicity of the particle.

Cell-matrix mechanics and pattern formation in inflammatory cardiovascular calcification

Calcific diseases of the cardiovascular system, such as atherosclerotic calcification and calcific aortic valve disease, are widespread and clinically significant, causing substantial morbidity and mortality. Vascular cells, like bone cells, interact with their matrix substrate through molecular signals, and through biomechanical signals, such as traction forces transmitted from cytoskeleton to matrix. The interaction of contractile vascular cells with their matrix may be one of the most important factors controlling pathological mineralisation of the artery wall and cardiac valves. In many respects, the matricrine and matrix mechanical changes in calcific vasculopathy and valvulopathy resemble those occurring in embryonic bone development and normal bone mineralisation. The matrix proteins provide a microenvironment for propagation of crystal growth and provide mechanical cues to the cells that direct differentiation. Small contractions of the cytoskeleton may tug on integrin links to sites on matrix proteins, and thereby sense the stiffness, possibly through deformation of binding proteins causing release of differentiation factors such as products of the members of the transforming growth factor-β superfamily. Inflammation and matrix characteristics are intertwined: inflammation alters the matrix such as through matrix metalloproteinases, while matrix mechanical properties affect cellular sensitivity to inflammatory cytokines. The adhesive properties of the matrix also regulate self-organisation of vascular cells into patterns through reaction-diffusion phenomena and left-right chirality. In this review, we summarise the roles of extracellular matrix proteins and biomechanics in the development of inflammatory cardiovascular calcification.

Identifying Small Coronary Calcification in Non-Contrast 0.5-mm Slice Reconstruction to Diagnose Coronary Artery Disease in Patients with a Conventional Zero Coronary Artery Calcium Score

Aims: In a new-generation computed tomography (CT) scanner, coronary artery calcium (CAC) scores were measured using 3.0-mm slice reconstruction images originally acquired with 0.5 mm thickness scans in a single beat. This study investigated the usefulness of thin-slice (0.5 mm) reconstruction for identifying small calcifications in coronary arteries and evaluated the association with coronary plaques and stenosis compared to conventional 3.0-mm reconstruction images.

Methods: We evaluated 132 patients with zero CAC scores in conventional 3.0-mm Agatston method using a 320-slice CT. Then, 0.5-mm slice reconstruction was performed to identify small calcifications. The presence of stenosis and coronary plaques was assessed using coronary CT angiography.

Results: In total, 22 small calcifications were identified in 18 patients. There were 28 (21%) patients with any (≥ 25%) stenosis (34 lesions). Forty-seven coronary plaques were found in 33 patients (25%), including 7 calcified plaques in 7 patients (5%), 34 noncalcified plaques in 27 patients (20%), and 6 partially calcified plaques in 5 patients (4%). Patients with small calcifications had a significantly higher prevalence of noncalcified or partially calcified plaques (83% vs 14%; p < 0.001) and obstructive stenosis (33% vs 5.2%; p < 0.001) compared to those without small calcifications. The addition of small calcifications to the coronary risk factors when diagnosing stenosis significantly improved the diagnostic value.

Conclusion: Small calcifications detected by thin-slice 0.5-mm reconstruction are useful for distinguishing coronary atherosclerotic lesions in patients with zero CAC scores from conventional CT reconstruction.

Shift of Macrophage Phenotype Due to Cartilage Oligomeric Matrix Protein Deficiency Drives Atherosclerotic Calcification

RATIONALE

Intimal calcification is highly correlated with atherosclerotic plaque burden, but the underlying mechanism is poorly understood. We recently reported that cartilage oligomeric matrix protein (COMP), a component of vascular extracellular matrix, is an endogenous inhibitor of vascular smooth muscle cell calcification.

OBJECTIVE

To investigate whether COMP affects atherosclerotic calcification.

METHODS AND RESULTS

ApoE(-/-)COMP(-/-) mice fed with chow diet for 12 months manifested more extensive atherosclerotic calcification in the innominate arteries than did ApoE(-/-) mice. To investigate which origins of COMP contributed to atherosclerotic calcification, bone marrow transplantation was performed between ApoE(-/-) and ApoE(-/-)COMP(-/-) mice. Enhanced calcification was observed in mice transplanted with ApoE(-/-)COMP(-/-) bone marrow compared with mice transplanted with ApoE(-/-) bone marrow, indicating that bone marrow-derived COMP may play a critical role in atherosclerotic calcification. Furthermore, microarray profiling of wild-type and COMP(-/-) macrophages revealed that COMP-deficient macrophages exerted atherogenic and osteogenic characters. Integrin β3 protein was attenuated in COMP(-/-) macrophages, and overexpression of integrin β3 inhibited the shift of macrophage phenotypes by COMP deficiency. Furthermore, adeno-associated virus 2-integrin β3 infection attenuated atherosclerotic calcification in ApoE(-/-)COMP(-/-) mice. Mechanistically, COMP bound directly to β-tail domain of integrin β3 via its C-terminus, and blocking of the COMP-integrin β3 association by β-tail domain mimicked the COMP deficiency-induced shift in macrophage phenotypes. Similar to COMP deficiency in mice, transduction of adeno-associated virus 2-β-tail domain enhanced atherosclerotic calcification in ApoE(-/-) mice.

CONCLUSIONS

These results reveal that COMP deficiency acted via integrin β3 to drive macrophages toward the atherogenic and osteogenic phenotype and thereby aggravate atherosclerotic calcification.

Histopathological assessment of calcification and inflammation of calcific aortic valves from patients with and without diabetes mellitus

BACKGROUND

Calcific aortic valve disease (CAVD) is the most common valvular heart disease and likely evolves from inflammatory pre-conditions in the valve. Type II diabetes mellitus (DMII) has been associated with pathogenesis of CAVD, however, the mechanism initiating CAVD in DMII is not well understood and the human valve pathology in DMII has not been described. We therefore performed quantitative histological analyses of aortic valves of CAVD patients with and without DMII.

METHODS

CAVD human aortic valves (n=45) obtained after surgical valve replacement were examined macroscopically with gross measurements of calcified areas. Inflammation and calcification were assessed by immunohistochemistry and immunofluorescence staining.

RESULTS

Calcification was increased in diabetic patients according to gross measurements (p<0.01) and alizarin red staining (p=0.05). Early calcification markers, including Runx2 (p=0.02) and alkaline phosphatase (ALP, p=0.03) were significantly elevated in diabetic patients. Furthermore, in diabetic patients we found significantly increased expression of annexin II (p=0.04) and annexin V (p=0.04), both of which are thought to play a role in microcalcification formation via apoptosis or extracellular vesicle release. Macrophage numbers were comparable in both groups (p=0.41), while the expression of the pro-inflammatory protein S100A9 (p<0.01) was significantly decreased in diabetic individuals. Evaluation of lymphocytes revealed similar CD8 (p=0.45) and CD4 (p=0.92) T cell counts in diabetic and non-diabetic aortic valves.

CONCLUSION

Aortic valves from diabetic patients show more calcification, while inflammation is similar in both patient populations. Considering the generally accepted theory of an inflammation-dependent mechanism of calcification, these data suggest that in patients with CAVD requiring valve replacement, diabetic patients could be molecularly in a more advanced disease stage with a higher grade of mineralization than non-diabetic patients.

Progression of coronary artery calcification at the crossroads: sign of progression or stabilization of coronary atherosclerosis?

Coronary artery calcification (CAC) has been strongly established as an independent predictor of adverse events, with a significant incremental prognostic value over traditional risk stratification algorithms. CAC progression has been associated with a higher rate of events. In parallel, several randomized studies and meta-analysis have shown the effectiveness of statins to slow progression and even promote plaque regression. However, evidence regarding the effect of routine medical therapy on CAC has yielded conflicting results, with initial studies showing significant CAC regression, and contemporaneous data showing rather the opposite. Accordingly, there is currently a great controversy on whether progression of CAC is a sign of progression or stabilization of coronary artery disease (CAD). The finding of inexorable CAC progression despite the implementation of intensive contemporaneous medical therapy suggests that further understanding of this phenomenon should be undertaken before the implementation of CAC as a surrogate endpoint for longitudinal studies, or for prospective follow-up of patients under routine medical treatment.

Characterisation of matrix vesicles in skeletal and soft tissue mineralisation

The importance of matrix vesicles (MVs) has been repeatedly highlighted in the formation of cartilage, bone, and dentin since their discovery in 1967. These nano-vesicular structures, which are found in the extracellular matrix, are believed to be one of the sites of mineral nucleation that occurs in the organic matrix of the skeletal tissues. In the more recent years, there have been numerous reports on the observation of MV-like particles in calcified vascular tissues that could be playing a similar role. Therefore, here, we review the characteristics MVs possess that enable them to participate in mineral deposition. Additionally, we outline the content of skeletal tissue- and soft tissue-derived MVs, and discuss their key mineralisation mediators that could be targeted for future therapeutic use.

Extracellular vesicles in cardiovascular calcification: expanding current paradigms

Vascular calcification is a major contributor to the progression of cardiovascular disease, one of the leading causes of death in industrialized countries. New evidence on the mechanisms of mineralization identified calcification-competent extracellular vesicles (EVs) derived from smooth muscle cells, valvular interstitial cells and macrophages as the mediators of calcification in diseased heart valves and atherosclerotic plaques. However, the regulation of EV release and the mechanisms of interaction between EVs and the extracellular matrix leading to the formation of destabilizing microcalcifications remain unclear. This review focuses on current limits in our understanding of EVs in cardiovascular disease and opens up new perspectives on calcific EV biogenesis, release and functions within and beyond vascular calcification. We propose that, unlike bone-derived matrix vesicles, a large population of EVs implicated in cardiovascular calcification are of exosomal origin. Moreover, the milieu-dependent loading of EVs with microRNA and calcification inhibitors fetuin-A and matrix Gla protein suggests a novel role for EVs in intercellular communication, adding a new mechanism to the pathogenesis of vascular mineralization. Similarly, the cell type-dependent enrichment of annexins 2, 5 or 6 in calcifying EVs posits one of several emerging factors implicated in the regulation of EV release and calcifying potential. This review aims to emphasize the role of EVs as essential mediators of calcification, a major determinant of cardiovascular mortality. Based on recent findings, we pinpoint potential targets for novel therapies to slow down the progression and promote the stability of atherosclerotic plaques.

Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation

Cardiovascular disease is the leading cause of morbidity and mortality in the world. Atherosclerotic plaques, consisting of lipid-laden macrophages and calcification, develop in the coronary arteries, aortic valve, aorta, and peripheral conduit arteries and are the hallmark of cardiovascular disease. In humans, imaging with computed tomography allows for the quantification of vascular calcification; the presence of vascular calcification is a strong predictor of future cardiovascular events. Development of novel therapies in cardiovascular disease relies critically on improving our understanding of the underlying molecular mechanisms of atherosclerosis. Advancing our knowledge of atherosclerotic mechanisms relies on murine and cell-based models. Here, a method for imaging aortic calcification and macrophage infiltration using two spectrally distinct near-infrared fluorescent imaging probes is detailed. Near-infrared fluorescent imaging allows for the ex vivo quantification of calcification and macrophage accumulation in the entire aorta and can be used to further our understanding of the mechanistic relationship between inflammation and calcification in atherosclerosis. Additionally, a method for isolating and culturing animal aortic vascular smooth muscle cells and a protocol for inducing calcification in cultured smooth muscle cells from either murine aortas or from human coronary arteries is described. This in vitro method of modeling vascular calcification can be used to identify and characterize the signaling pathways likely important for the development of vascular disease, in the hopes of discovering novel targets for therapy.

HMGB1 Induces Secretion of Matrix Vesicles by Macrophages to Enhance Ectopic Mineralization

Numerous clinical conditions have been linked to ectopic mineralization (EM). This process of pathological biomineralization is complex and not fully elucidated, but thought to be started within matrix vesicles (MVs). We hypothesized that high mobility group box 1 (HMGB1), a cytokine associated with biomineralizing process under physiological and pathological conditions, induces EM via promoting MVs secretion from macrophages. In this study, we found that HMGB1 significantly promoted secretion of MVs from macrophages and subsequently led to mineral deposition in elevated Ca/Pi medium in vitro. Transmission electron microscopy of calcifying MVs showed formation of hydroxyapatite crystals in the vesicle interior. Subcutaneous injection into mice with MVs derived from HMGB1-treated cells showed a greater potential to initiate regional mineralization. Mechanistic experiments revealed that HMGB1 activated neutral sphingomyelinase2 (nSMase2) that involved the receptor for advanced glycation end products (RAGE) and p38 MAPK (upstream of nSMase2). Inhibition of nSMase2 with GW4869 or p38 MAPK with SB-239063 prevented MVs secretion and mineral deposition. Collectively, HMGB1 induces MVs secretion from macrophages at least in part, via the RAGE/p38 MAPK/nSMase2 signaling pathway. Our findings thus reveal a novel mechanism by which HMGB1 induces ectopic mineralization.

Imaging of coronary atherosclerosis - evolution towards new treatment strategies

Coronary atherosclerosis and the precipitation of acute myocardial infarction are highly complex processes, which makes accurate risk prediction challenging. Rapid developments in invasive and noninvasive imaging technologies now provide us with detailed, exquisite images of the coronary vasculature that allow direct investigation of a wide range of these processes. These modalities include sophisticated assessments of luminal stenoses and myocardial perfusion, complemented by novel measures of the atherosclerotic plaque burden, adverse plaque characteristics, and disease activity. Together, they can provide comprehensive, individualized assessments of coronary atherosclerosis as it occurs in patients. Not only can this information provide important pathological insights, but it can also potentially be used to guide personalized treatment decisions. In this Review, we describe the latest advances in both established and emerging imaging techniques, focusing on the strengths and weakness of each approach. Moreover, we discuss how these technological advances might be translated from attractive images into novel imaging strategies and definite improvements in clinical risk prediction and patient outcomes. This process will not be easy, and the many potential barriers and difficulties are also reviewed.