Free DNA precipitates calcium phosphate apatite crystals in the arterial wall in vivo

Equilibrium interactions of biomimetic DNA aptamers produce intrafibrillar calcium phosphate mineralization of collagen

Native and biomimetic DNA structures have been demonstrated to impact materials synthesis under a variety of conditions but have only just begun to be explored in this role compared to other biopolymers such as peptides, proteins, polysaccharides, and glycopolymers. One selected DNA aptamer has been explored in calcium phosphate and calcium carbonate mineralization, demonstrating sequence-dependent control of kinetics, morphology, and crystallinity. This aptamer is here applied to a biologically-relevant bone model system that uses collagen hydrogels. In the presence of the aptamer, intrafibrillar collagen mineralization is observed compared to negative controls and a positive control using well-studied poly-aspartic acid. The mechanism of interaction is explored through affinity measurements, kinetics of calcium uptake, and kinetics of aptamer uptake into the forming mineral. There is a marked difference observed between the selected aptamer containing a G-quadruplex secondary structure compared to a control sequence with no G-quadruplex. It is hypothesized that the equilibrium interaction of the aptamer with calcium-phosphate precursors and with the collagen itself leads to slow kinetic mineral formation and a morphology appropriate to bone. This points to new uses for DNA aptamers in biologically-relevant mineralization systems and the possibility of future biomedical applications. STATEMENT OF SIGNIFICANCE: Collagen is the protein structural component that mineralizes with calcium phosphate to form durable bone. Crystalline calcium phosphate must be infused throughout the collagen fiber structure to produce a strong material. This process is assisted by soluble proteins that interact with both calcium phosphate precursors and the collagen protein and has been proposed to follow a polymer-induce liquid precursor (PILP) model. Further understanding of this model and control of the process through synthetic, biomimetic molecules could have significant advantages in biomedical, restorative procedures. For the first time, synthetic DNA aptamers with specific secondary structures are here shown to influence and direct collagen mineralization. The mechanism of this process has been studied to demonstrate an important equilibrium between the DNA aptamer, calcium phosphate precursors, and collagen.

Macrophage-Derived Extracellular DNA Initiates Heterotopic Ossification

Heterotopic ossification (HO) severely affects people's lives; however, its pathological mechanism remains poorly understood. Although extracellular DNA (ecDNA) has been shown to play important roles in pathological calcification, its effects in HO development and progression remain unknown. The in vivo rat Achilles tendon injury model and in vitro collagen I calcification model were used to evaluate the effects of ecDNA in the ectopic calcifications and the main cell types involved in those pathological process. Histology, immunofluorescent staining, reverse transcriptase-polymerase chain reaction analysis and micro-computed tomography were used to identify the distribution of macrophage-derived ecDNA and elucidate their roles in HO. The results showed that the amount of ecDNA and ectopic calcification increased significantly and exhibited a strong correlation in the injured tendons of HO model compared with those of the controls, which was accompanied by a significantly increased number of M2 macrophages in the injured tendon. During in vitro co-culture experiments, M2 macrophages calcified the reconstituted type I collagen and ectopic bone collected from the injured tendons of HO rats, while those effects were inhibited by deoxyribonuclease. More importantly, deoxyribonuclease reversed the pathological calcification in the injured rat tendon HO model. The present study showed that ecDNA from M2 macrophages initiates pathological calcification in HO, and the elimination of ecDNA might be developed into a clinical strategy to prevent ectopic mineralization diseases. The use of deoxyribonuclease for the targeted degradation of ecDNA at affected tissue sites provides a potential solution to treat diseases associated with ectopic mineralization.

Elastic fiber alterations and calcifications in calcific uremic arteriolopathy

Calcific uremic arteriolopathy (CUA) is a severely morbid disease, affecting mostly dialyzed end-stage renal disease (ESRD) patients, associated with calcium deposits in the skin. Calcifications have been identified in ESRD patients without CUA, indicating that their presence is not specific to the disease. The objective of this retrospective multicenter study was to compare elastic fiber structure and skin calcifications in ESRD patients with CUA to those without CUA using innovative structural techniques. Fourteen ESRD patients with CUA were compared to 12 ESRD patients without CUA. Analyses of elastic fiber structure and skin calcifications using multiphoton microscopy followed by machine-learning analysis and field-emission scanning electron microscopy coupled with energy dispersive X-ray were performed. Elastic fibers specifically appeared fragmented in CUA. Quantitative analyses of multiphoton images showed that they were significantly straighter in ESRD patients with CUA than without CUA. Interstitial and vascular calcifications were observed in both groups of ESRD patients, but vascular calcifications specifically appeared massive and circumferential in CUA. Unlike interstitial calcifications, massive circumferential vascular calcifications and elastic fibers straightening appeared specific to CUA. The origins of such specific elastic fiber's alteration are still to be explored and may involve relationships with ischemic vascular or inflammatory processes.

Unusual Histopathological Findings in Mechanically Removed Stroke Thrombi - A Multicenter Experience

Background

Several studies have investigated the histopathology of mechanically retrieved thrombi from stroke patients. Thrombi with unusual components constitute about 1–2% of all stroke thrombi in clinical practice. Knowledge about these rare components is limited.

Objectives

To characterize the histopathology of unusual stroke thrombi from a real-world setting with relation to clinical presentation, patient characteristics and procedural aspects of mechanical thrombectomy.

Methods

One-thousand and eight thrombi retrieved from stroke patients with mechanical thrombectomy at three different hospitals were retrospectively reviewed for unusual histological components. Fifteen thrombi were included in the study for further histopathological analysis. Clinical data and data on procedural aspects were collected.

Results

We identified six cases with large amounts of extracellular DNA, of which three were calcified. All six cases except one received anticoagulant therapy. We describe two types of calcifications that differ with respect to general calcification morphology, von Kossa staining pattern, macrophage immunophenotype and presence of multinucleated giant cells. Cholesterol-rich (n = 3), adipocyte-like pattern-rich (n = 2), collagen-rich (n = 2) and myxomatous (n = 1) thrombi were also identified and are discussed with regard to pathogenesis and clinical and intervention characteristics. Finally, a thrombus with parts of a vascular wall is described. Suggestions for future studies are made and clinical and technical aspects of the management for these rare but important patients are discussed.

Conclusion

In our retrospective multicenter study, we characterized stroke thrombi histopathologically and found subgroups of thrombi defined by presence of rarely seen components. These defined subgroups showed relation to underlying cardiovascular disease, patient characteristics, and mechanical thrombectomy technique. Knowledge about these components may increase our understanding of stroke pathophysiology and influence interventional procedures.

New Therapeutics Targeting Arterial Media Calcification: Friend or Foe for Bone Mineralization?

The presence of arterial media calcification, a highly complex and multifactorial disease, puts patients at high risk for developing serious cardiovascular consequences and mortality. Despite the numerous insights into the mechanisms underlying this pathological mineralization process, there is still a lack of effective treatment therapies interfering with the calcification process in the vessel wall. Current anti-calcifying therapeutics may induce detrimental side effects at the level of the bone, as arterial media calcification is regulated in a molecular and cellular similar way as physiological bone mineralization. This especially is a complication in patients with chronic kidney disease and diabetes, who are the prime targets of this pathology, as they already suffer from a disturbed mineral and bone metabolism. This review outlines recent treatment strategies tackling arterial calcification, underlining their potential to influence the bone mineralization process, including targeting vascular cell transdifferentiation, calcification inhibitors and stimulators, vascular smooth muscle cell (VSMC) death and oxidative stress: are they a friend or foe? Furthermore, this review highlights nutritional additives and a targeted, local approach as alternative strategies to combat arterial media calcification. Paving a way for the development of effective and more precise therapeutic approaches without inducing osseous side effects is crucial for this highly prevalent and mortal disease.

Extracellular DNA: A Missing Link in the Pathogenesis of Ectopic Mineralization

Although deoxyribonucleic acid (DNA) is the genetic coding for the very essence of life, these macromolecules or components thereof are not necessarily lost after a cell dies. There appears to be a link between extracellular DNA and biomineralization. Here the authors demonstrate that extracellular DNA functions as an initiator of collagen intrafibrillar mineralization. This is confirmed with in vitro and in vivo biological mineralization models. Because of their polyanionic property, extracellular DNA molecules are capable of stabilizing supersaturated calcium phosphate solution and mineralizing 2D and 3D collagen matrices completely as early as 24 h. The effectiveness of extracellular DNA in biomineralization of collagen is attributed to the relatively stable formation of amorphous liquid droplets triggered by attraction of DNA to the collagen fibrils via hydrogen bonding. These findings suggest that extracellular DNA is biomimetically significant for fabricating inorganic-organic hybrid materials for tissue engineering. DNA-induced collagen intrafibrillar mineralization provides a clue to the pathogenesis of ectopic mineralization in different body tissues. The use of DNase for targeting extracellular DNA at destined tissue sites provides a potential solution for treatment of diseases associated with ectopic mineralization.

Properties and Application of Cell-Free DNA as a Clinical Biomarker

Biomarkers are valuable tools in clinical practice. In 2001, the National Institutes of Health (NIH) standardized the definition of a biomarker as a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. A biomarker has clinical relevance when it presents precision, standardization and reproducibility, suitability to the patient, straightforward interpretation by clinicians, and high sensitivity and/or specificity by the parameter it proposes to identify. Thus, serum biomarkers should have advantages related to the simplicity of the procedures and to the fact that venous blood collection is commonplace in clinical practice. We described the potentiality of cfDNA as a general clinical biomarker and focused on endothelial dysfunction. Circulating cell-free DNA (cfDNA) refers to extracellular DNA present in body fluid that may be derived from both normal and diseased cells. An increasing number of studies demonstrate the potential use of cfDNA as a noninvasive biomarker to determine physiologic and pathologic conditions. However, although still scarce, increasing evidence has been reported regarding using cfDNA in cardiovascular diseases. Here, we have reviewed the history of cfDNA, its source, molecular features, and release mechanism. We also show recent studies that have investigated cfDNA as a possible marker of endothelial damage in clinical settings. In the cardiovascular system, the studies are quite new, and although interesting, stronger evidence is still needed. However, some drawbacks in cfDNA methodologies should be overcome before its recommendation as a biomarker in the clinical setting.

Clinical Approach to Vascular Calcification in Patients With Non-dialysis Dependent Chronic Kidney Disease: Mineral-Bone Disorder-Related Aspects

Chronic kidney disease (CKD) is associated with a very high morbimortality, mainly from cardiovascular origin, and CKD is currently considered in the high- or very high risk- cardiovascular risk category. CKD-mineral and bone disorders (CKD-MBDs), including vascular and/or valvular calcifications, are also associated with these poor outcomes. Vascular calcification (VC) is very prevalent (both intimal and medial), even in non-dialysis dependent patients, with a greater severity and more rapid progression. Simple X-ray based-scores such as Adragão's (AS) are useful prognostic tools and AS (even AS based on hand-X-ray only) may be superior to the classic Kauppila's score when evaluating non-dialysis CKD patients. Thus, in this mini-review, we briefly review CKD-MBD-related aspects of VC and its complex pathophysiology including the vast array of contributors and inhibitors. Furthermore, although VC is a surrogate marker and is not yet considered a treatment target, we consider that the presence of VC may be relevant in guiding therapeutic interventions, unless all patients are treated with the mindset of reducing the incidence or progression of VC with the currently available armamentarium. Avoiding phosphate loading, restricting calcium-based phosphate binders and high doses of vitamin D, and avoiding normalizing (within the normal limits for the assay) parathyroid hormone levels seem logical approaches. The availability of new drugs and future studies, including patients in early stages of CKD, may lead to significant improvements not only in patient risk stratification but also in attenuating the accelerated progression of VC in CKD.

Vascular Calcification in Chronic Kidney Disease: Diversity in the Vessel Wall

Vascular calcification (VC) is one of the major causes of cardiovascular morbidity and mortality in patients with chronic kidney disease (CKD). VC is a complex process expressing similarity to bone metabolism in onset and progression. VC in CKD is promoted by various factors not limited to hyperphosphatemia, Ca/Pi imbalance, uremic toxins, chronic inflammation, oxidative stress, and activation of multiple signaling pathways in different cell types, including vascular smooth muscle cells (VSMCs), macrophages, and endothelial cells. In the current review, we provide an in-depth analysis of the various kinds of VC, the clinical significance and available therapies, significant contributions from multiple cell types, and the associated cellular and molecular mechanisms for the VC process in the setting of CKD. Thus, we seek to highlight the key factors and cell types driving the pathology of VC in CKD in order to assist in the identification of preventative, diagnostic, and therapeutic strategies for patients burdened with this disease.

Detailed histological analysis of a thrombectomy-resistant ischemic stroke thrombus: a case report

Background

Mechanical removal of a thrombus by thrombectomy can be quite challenging. For reasons that are not fully understood, some thrombi require multiple passes to achieve successful recanalization, whereas other thrombi are efficiently removed in a single pass. Since first pass success is associated with better clinical outcome, it is important to better understand the nature of thrombectomy resistant thrombi. The aim of this study was therefore to characterize the cellular and molecular composition of a thrombus that was very hard to retrieve via mechanical thrombectomy.

Case presentation

In a patient that was admitted with a right middle cerebral artery M1-occlusion, 11 attempts using various thrombectomy devices and techniques were required for removal of the thrombus. This peculiar case provided a rare opportunity to perform an in-depth histopathological study of a difficult to retrieve thrombus. Thrombus material was histologically analyzed using hematoxylin and eosin, Martius Scarlet Blue stain (red blood cells and fibrin), Feulgen stain (DNA), von Kossa stain (calcifications) and immunohistochemical analysis of von Willebrand factor, platelets, leukocytes and neutrophil extracellular traps. Histological analysis revealed abnormally high amounts of extracellular DNA, leukocytes, von Willebrand factor and calcifications. Extracellular DNA stained positive for markers of leukocytes and NETs, suggesting that a significant portion of DNA is derived from neutrophil extracellular traps.

Conclusion

In this unique case of a nearly thrombectomy-resistant stroke thrombus, our study showed an atypical composition compared to the common structural features found in ischemic stroke thrombi. The core of the retrieved thrombus consisted of extracellular DNA that colocalized with von Willebrand factor and microcalcifications. These results support the hypothesis that von Willebrand factor, neutrophil extracellular traps and microcalcifications contribute to mechanical thrombectomy resistance. Such information is important to identify novel targets in order to optimize technical treatment protocols and techniques to increase first pass success rates.

From organic and inorganic phosphates to valvular and vascular calcifications

Calcification of the arterial wall and valves is an important part of the pathophysiological process of peripheral and coronary atherosclerosis, aortic stenosis, ageing, diabetes, and chronic kidney disease. This review aims to better understand how extracellular phosphates and their ability to be retained as calcium phosphates on the extracellular matrix initiate the mineralization process of arteries and valves. In this context, the physiological process of bone mineralization remains a human model for pathological soft tissue mineralization. Soluble (ionized) calcium precipitation occurs on extracellular phosphates; either with inorganic or on exposed organic phosphates. Organic phosphates are classified as either structural (phospholipids, nucleic acids) or energetic (corresponding to phosphoryl transfer activities). Extracellular phosphates promote a phenotypic shift in vascular smooth muscle and valvular interstitial cells towards an osteoblast gene expression pattern, which provokes the active phase of mineralization. A line of defense systems protects arterial and valvular tissue calcifications. Given the major roles of phosphate in soft tissue calcification, phosphate mimetics, and/or prevention of phosphate dissipation represent novel potential therapeutic approaches for arterial and valvular calcification.

Phylogenic Determinants of Cardiovascular Frailty, Focus on Hemodynamics and Arterial Smooth Muscle Cells

The evolution of the circulatory system from invertebrates to mammals has involved the passage from an open system to a closed in-parallel system via a closed in-series system, accompanying the increasing complexity and efficiency of life’s biological functions. The archaic heart enables pulsatile motion waves of hemolymph in invertebrates, and the in-series circulation in fish occurs with only an endothelium, whereas mural smooth muscle cells appear later. The present review focuses on evolution of the circulatory system. In particular, we address how and why this evolution took place from a closed, flowing, longitudinal conductance at low pressure to a flowing, highly pressurized and bifurcating arterial compartment. However, although arterial pressure was the latest acquired hemodynamic variable, the general teleonomy of the evolution of species is the differentiation of individual organ function, supported by specific fueling allowing and favoring partial metabolic autonomy. This was achieved via the establishment of an active contractile tone in resistance arteries, which permitted the regulation of blood supply to specific organ activities via its localized function-dependent inhibition (active vasodilation). The global resistance to viscous blood flow is the peripheral increase in frictional forces caused by the tonic change in arterial and arteriolar radius, which backscatter as systemic arterial blood pressure. Consequently, the arterial pressure gradient from circulating blood to the adventitial interstitium generates the unidirectional outward radial advective conductance of plasma solutes across the wall of conductance arteries. This hemodynamic evolution was accompanied by important changes in arterial wall structure, supported by smooth muscle cell functional plasticity, including contractility, matrix synthesis and proliferation, endocytosis and phagocytosis, etc. These adaptive phenotypic shifts are due to epigenetic regulation, mainly related to mechanotransduction. These paradigms actively participate in cardio-arterial pathologies such as atheroma, valve disease, heart failure, aneurysms, hypertension, and physiological aging.

Roles of Histone Acetylation Modifiers and Other Epigenetic Regulators in Vascular Calcification

Vascular calcification (VC) is characterized by calcium deposition inside arteries and is closely associated with the morbidity and mortality of atherosclerosis, chronic kidney disease, diabetes, and other cardiovascular diseases (CVDs). VC is now widely known to be an active process occurring in vascular smooth muscle cells (VSMCs) involving multiple mechanisms and factors. These mechanisms share features with the process of bone formation, since the phenotype switching from the contractile to the osteochondrogenic phenotype also occurs in VSMCs during VC. In addition, VC can be regulated by epigenetic factors, including DNA methylation, histone modification, and noncoding RNAs. Although VC is commonly observed in patients with chronic kidney disease and CVD, specific drugs for VC have not been developed. Thus, discovering novel therapeutic targets may be necessary. In this review, we summarize the current experimental evidence regarding the role of epigenetic regulators including histone deacetylases and propose the therapeutic implication of these regulators in the treatment of VC.

Innovative application of nested PCR for detection of Porphyromonas gingivalis in human highly calcified atherothrombotic plaques

Atherothrombosis, leading to stroke and myocardial infarction, is responsible for most of the deaths in the world. An increased risk of atherothrombotic vascular events has been reported in patients with periodontitis. Periodontitis is a chronic multifactorial inflammatory disease, which involves a dysbiotic microbiota, and leads to a progressive destruction of the tooth-supporting apparatus. Transcient periodontal pathogen blood translocation, mainly bacteremia, has been associated with the severity of gingival inflammation. The identification of periodontal bacteria within atherothrombotic plaques is challenging and unpredictable. This review aims to summarize existing molecular technics for identifying periodontal microbiota in human atherothrombotic samples. A secondary objective is to describe a protocol for the identification of Porphyromonas gingivalis from highly calcified, atherothrombotic human samples that is based on our experience in translational cardiovascular research. Compared to direct real-time PCR, our protocol based on nested PCR has increased the detection of Porphyromonas gingivalis by 22.2% with good specificity.

Persistence of Intraluminal Thrombus Makes Saccular Aneurysm More Biologically Active than Fusiform in an Experimental Rat Model

INTRODUCTION

Saccular aneurysms are thought to have a worse prognosis than fusiform aneurysms in humans, due to hemodynamic reasons. However, data comparing hemodynamic and biology in saccular and fusiform aneurysms are lacking. The main objective was to evaluate the impact of aneurysm morphology on intra-luminal thrombus (ILT) formation and activity.

METHODS

Forty Lewis rats were ran-domly divided into 2 groups of 20: "saccular" (Group A) and "fusiform" (Group B) aneurysms. Decellularized thoracic aortas from guinea pigs were xenografted to create saccular or fusiform aneurysms. Final imaging evaluation of the aneurysms was carried out during the third week, by quantitative Doppler ultrasound and magnetic resonance imaging. Assays of myeloperoxidase (MPO), platelet factor 4 (PF4), advanced oxidation protein products (AOPPs) iron and matrix metallopeptidase-9 (MMP-9) were performed as biological criteria.

RESULTS

Quantitatively, saccular aneurysms are characterized by a more thicker ILT, lower inflow velocities and more important relative backflow velocities as compared to fusiform aneurysms. Compared to fusiform, saccular aneurysms released significantly more MPO (p = 0.004), PF4 (p = 0.02), AOPPs (p < 0.002), iron (p < 0.0001) and MMP-9 (p < 0.04).

CONCLUSION

Experimental saccular and fusiform aneurysms show differential specific hemodynamics, which seem to impact the histology and the biology of the ILT in each type of aneurysm.

Selected DNA aptamers as hydroxyapatite affinity reagents

DNA aptamers were selected for their ability to bind specifically and quickly to crystalline hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂; HAP), the primary mineral component of enamel and bone. Aptamers were found to have an enhanced percent of G-nucleotides and a propensity for forming a G-quadruplex secondary structure. One aptamer was studied in comparison to control sequences and was found to bind with high affinity and at high loading capacity, with enhanced binding kinetics, and with specificity for crystalline HAP material over amorphous calcium phosphate (ACP) and β-tricalcium phosphate (TCP). The fluorescently-functionalized aptamer was demonstrated to specifically label HAP in a surface binding experiment and suggests the usefulness of this selected aptamer in biomedical or biotechnology fields where the labeling of specific calcium phosphate materials is required.

New Insights into the Roles of Monocytes/Macrophages in Cardiovascular Calcification Associated with Chronic Kidney Disease

Cardiovascular disease (CVD) is an important cause of death in patients with chronic kidney disease (CKD), and cardiovascular calcification (CVC) is one of the strongest predictors of CVD in this population. Cardiovascular calcification results from complex cellular interactions involving the endothelium, vascular/valvular cells (i.e., vascular smooth muscle cells, valvular interstitial cells and resident fibroblasts), and monocyte-derived macrophages. Indeed, the production of pro-inflammatory cytokines and oxidative stress by monocyte-derived macrophages is responsible for the osteogenic transformation and mineralization of vascular/valvular cells. However, monocytes/macrophages show the ability to modify their phenotype, and consequently their functions, when facing environmental modifications. This plasticity complicates efforts to understand the pathogenesis of CVC-particularly in a CKD setting, where both uraemic toxins and CKD treatment may affect monocyte/macrophage functions and thereby influence CVC. Here, we review (i) the mechanisms by which each monocyte/macrophage subset either promotes or prevents CVC, and (ii) how both uraemic toxins and CKD therapies might affect these monocyte/macrophage functions.

Role of smooth muscle cells in vascular calcification: implications in atherosclerosis and arterial stiffness

Vascular calcification is associated with a significant increase in all-cause mortality and atherosclerotic plaque rupture. Calcification has been determined to be an active process driven in part by vascular smooth muscle cell (VSMC) transdifferentiation within the vascular wall. Historically, VSMC phenotype switching has been viewed as binary, with the cells able to adopt a physiological contractile phenotype or an alternate ‘synthetic’ phenotype in response to injury. More recent work, including lineage tracing has however revealed that VSMCs are able to adopt a number of phenotypes, including calcific (osteogenic, chondrocytic, and osteoclastic), adipogenic, and macrophagic phenotypes. Whilst the mechanisms that drive VSMC differentiation are still being elucidated it is becoming clear that medial calcification may differ in several ways from the intimal calcification seen in atherosclerotic lesions, including risk factors and specific drivers for VSMC phenotype changes and calcification. This article aims to compare and contrast the role of VSMCs in driving calcification in both atherosclerosis and in the vessel media focusing on the major drivers of calcification, including aging, uraemia, mechanical stress, oxidative stress, and inflammation. The review also discusses novel findings that have also brought attention to specific pro- and anti-calcifying proteins, extracellular vesicles, mitochondrial dysfunction, and a uraemic milieu as major determinants of vascular calcification.

Current and Emerging Preclinical Approaches for Imaging-Based Characterization of Atherosclerosis

Atherosclerotic plaques can remain quiescent for years, but become life threatening upon rupture or disruption, initiating clot formation in the vessel lumen and causing acute myocardial infarction and ischemic stroke. Whether and how a plaque ruptures is determined by its macroscopic structure and microscopic composition. Rupture-prone plaques usually consist of a thin fibrous cap with few smooth muscle cells, a large lipid core, a dense infiltrate of inflammatory cells, and neovessels. Such lesions, termed high-risk plaques, can remain asymptomatic until the thrombotic event. Various imaging technologies currently allow visualization of morphological and biological characteristics of high-risk atherosclerotic plaques. Conventional protocols are often complex and lack specificity for high-risk plaque. Conversely, new imaging approaches are emerging which may overcome these limitations. Validation of these novel imaging techniques in preclinical models of atherosclerosis is essential for effective translational to clinical practice. Imaging the vessel wall, as well as its biological milieu in small animal models, is challenging because the vessel wall is a small structure that undergoes continuous movements imposed by the cardiac cycle as it is adjacent to circulating blood. The focus of this paper is to provide a state-of-the-art review on techniques currently available for preclinical imaging of atherosclerosis in small animal models and to discuss the advantages and limitations of each approach.

Suppression of SIRT1 in Diabetic Conditions Induces Osteogenic Differentiation of Human Vascular Smooth Muscle Cells via RUNX2 Signalling

Vascular calcification is associated with significant morbidity and mortality within diabetes, involving activation of osteogenic regulators and transcription factors. Recent evidence demonstrates the beneficial role of Sirtuin 1 (SIRT1), an NAD⁺ dependant deacetylase, in improved insulin sensitivity and glucose homeostasis, linking hyperglycaemia and SIRT1 downregulation. This study aimed to determine the role of SIRT1 in vascular smooth muscle cell (vSMC) calcification within the diabetic environment. An 80% reduction in SIRT1 levels was observed in patients with diabetes, both in serum and the arterial smooth muscle layer, whilst both RUNX2 and Osteocalcin levels were elevated. Human vSMCs exposed to hyperglycaemic conditions in vitro demonstrated enhanced calcification, which was positively associated with the induction of cellular senescence, verified by senescence-associated β-galactosidase activity and cell cycle markers p16 and p21. Activation of SIRT1 by SRT1720 reduced Alizarin red staining by a third, via inhibition of the RUNX2 pathway and prevention of senescence. Conversely, inhibition of SIRT1 via Sirtinol and siRNA increased RUNX2 by over 50%. These findings demonstrate the key role that SIRT1 plays in preventing calcification in a diabetic environment, through the inhibition of RUNX2 and senescence pathways, suggesting a downregulation of SIRT1 may be responsible for perpetuating vascular calcification in diabetes.

Detection of nucleic acids and other low abundance components in native bone and osteosarcoma extracellular matrix by isotope enrichment and DNP-enhanced NMR

Sensitivity enhancement by isotope enrichment and DNP NMR enables detection of minor but biologically relevant species in native intact bone, including nucleic acids, choline from phospholipid headgroups, and histidinyl and hydroxylysyl groups. Labelled matrix from the aggressive osteosarcoma K7M2 cell line confirms the assignments of nucleic acid signals arising from purine, pyrimidine, ribose, and deoxyribose species. Detection of these species is an important and necessary step in elucidating the atomic level structural basis of their functions in intact tissue.

Towards elucidating their biological roles in intact tissue, DNP NMR reveals nucleic acids, and other important low abundance biomolecules in a complex biomaterial, bone, and in cancer extracellular matrix.

Abdominal aortic aneurysms

An abdominal aortic aneurysm (AAA) is a localized dilatation of the infrarenal aorta. AAA is a multifactorial disease, and genetic and environmental factors play a part; smoking, male sex and a positive family history are the most important risk factors, and AAA is most common in men >65 years of age. AAA results from changes in the aortic wall structure, including thinning of the media and adventitia due to the loss of vascular smooth muscle cells and degradation of the extracellular matrix. If the mechanical stress of the blood pressure acting on the wall exceeds the wall strength, the AAA ruptures, causing life-threatening intra-abdominal haemorrhage - the mortality for patients with ruptured AAA is 65-85%. Although AAAs of any size can rupture, the risk of rupture increases with diameter. Intact AAAs are typically asymptomatic, and in settings where screening programmes with ultrasonography are not implemented, most cases are diagnosed incidentally. Modern functional imaging techniques (PET, CT and MRI) may help to assess rupture risk. Elective repair of AAA with open surgery or endovascular aortic repair (EVAR) should be considered to prevent AAA rupture, although the morbidity and mortality associated with both techniques remain non-negligible.

Biochemical transformation of calciprotein particles in uraemia

Calciprotein particles (CPP) have emerged as nanoscale mediators of phosphate-induced toxicity in Chronic Kidney Disease (CKD). Uraemia favors ripening of the particle mineral content from the amorphous (CPP-I) to the crystalline state (CPP-II) but the pathophysiological significance of this transformation is uncertain. Clinical studies suggest an association between CPP ripening and inflammation, vascular dysfunction and mortality. Although ripening has been modelled in vitro, it is unknown whether particles synthesised in serum resemble their in vivo counterparts. Here we show that in vitro formation and ripening of CPP in uraemic serum is characterised by extensive physiochemical rearrangements involving the accretion of mineral, loss of surface charge and transformation of the mineral phase from a spherical arrangement of diffuse domains of amorphous calcium phosphate to densely-packed lamellar aggregates of crystalline hydroxyapatite. These physiochemical changes were paralleled by enrichment with small soluble apolipoproteins, complement factors and the binding of fatty acids. In comparison, endogenous CPP represent a highly heterogeneous mixture of particles with characteristics mostly intermediate to synthetic CPP-I and CPP-II, but are also uniquely enriched for carbonate-substituted apatite, DNA fragments, small RNA and microbe-derived components. Pathway analysis of protein enrichment predicted the activation of cell death and pro-inflammatory processes by endogenous CPP and synthetic CPP-II alike. This comprehensive characterisation validates the use of CPP-II generated in uraemic serum as in vitro equivalents of their endogenous counterparts and provides insight into the nature and pathological significance of CPP in CKD, which may act as vehicles for various bioactive ligands.

Schistosoma mansoni and endocarditis: from egg to free DNA detection in Egyptian patients and infected BALB/c mice

With the growing incidence of closed schistosomiasis and uncommon presentations, there is a risk of the infection rate being underestimated. A study in Japan reported an unexplained case of endocarditis that was finally diagnosed as a complex Schistosoma japonicum infection; in the absence of advanced techniques, the diagnosis was delayed. We therefore set out to explore the incidence of Schistosoma mansoni in endocarditis patients coming from areas of Egypt where S. mansoni is endemic. We also investigated histopathological changes in the cardiac valves and the presence of cell-free parasite DNA (CFPD) in cardiac tissues of laboratory mice infected with S. mansoni. The study included 186 patients with the manifestations of infective endocarditis. Eggs were detected in the stool samples of 5.91% of patients. Seropositivity was reported in 23.66% of patients and antigen was detected in the urine samples of 10.21%. Using real-time polymerase chain reaction (PCR), CFPD was detected in the blood of 6.98% of the endocarditis patients and 95% of the infected mice, while the cardiac samples of 45% of the mice tested positive for CFPD (means ± SD = 1390.2 ± 283.65, 2158.72 ± 1103.1 and 5.71 ± 2.91, respectively). Histopathological examination revealed abnormal collagen deposition, inflammatory cells and haemorrhagic pigmentation in the heart sections. Despite the low incidence of S. mansoni infection in the studied cohort, the presence of CFPD in the cardiac tissue of infected mice makes it necessary to: (1) investigate the hazards of CFPD deposition in endothelium-rich organs; and (2) test the potential of CFPD to trigger tissue inflammation, abnormal proliferation or genome integration.