Mechanisms and clinical consequences of vascular calcification

Aerobic exercise modulates aortic chondrogenesis and calcification via 5-methoxytryptophan and P38MAPK in atherosclerotic rats

BACKGROUND

5-Methoxytryptophan (5-MTP), a new endothelial factor with vasoprotective and anti-inflammatory effects, reduces aortic chondrogenesis and calcification during atherosclerosis. The aim of this study was to investigate the effects of aerobic exercise on aortic chondrogenesis and calcification during atherosclerosis in rats. To investigate the effect of aerobic exercise on the expression of 5-MTP/P38 MAPK signaling pathway. To lay a theoretical foundation for the therapeutic effect of exercise in rat atherosclerosis model.

METHODS

Establishment of a rat model of atherosclerosis using a high-fat diet combined with intraperitoneal injection of vitamin D3 (VD3). The aerobic exercise group underwent moderate-intensity aerobic exercise on an exercise treadmill for 8 weeks, while the atherosclerosis model group and the control group did not exercise. After exercise, blood and aortic samples were collected from all rats to evaluate the levels of serum triglyceride (TG), cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDLC), aortic chondrogenesis, calcification, 5-MTP level, collagen II, P38MAPK, pp38 MAPK, and IL-6 protein content.

RESULTS

(1)8 weeks of aerobic exercise significantly reduced aortic chondrogenesis, area of calcification, serum LDL-C, TC levels, atherosclerotic index and serum IL-6 levels in rats (p < 0.01), and lowered TG levels (p < 0.05);(2)8 weeks of aerobic exercise significantly increased aortic 5-MTP levels (p < 0.01) and decreased the content of aortic pp38MAPK, collagen II and IL-6 proteins significantly (p < 0.01). The pp38MAPK/P38MAPK ratio was also decreased (p < 0.01).

CONCLUSION

8 weeks of aerobic exercise training improved dyslipidemia and reduced aortic chondrogenesis and calcification formation in AS rats. The mechanism may be related to increasing aortic 5-MTP levels and inhibiting the P38MAPK/ IL-6 signaling pathway.

Exploring Bone Morphogenetic Protein-2 and -4 mRNA Expression and Their Receptor Assessment in a Dynamic In Vitro Model of Vascular Calcification

BACKGROUND

Vascular calcification (VC) is a dynamic, tightly regulated process driven by cellular activity and resembling the mechanisms of bone formation, with specific molecules playing pivotal roles in its progression. We aimed to investigate the involvement of the bone morphogenic proteins (BMP-2, BMP-4, BMPR-1a/1b, and BMPR-2) system in this process. Our study used an advanced in vitro model that simulates the biological environment of the vascular wall, assessing the ability of a phosphate mixture to induce the osteoblastic switch in human coronary artery smooth muscle cells (HCASMCs).

METHODS

HCASMCs were grown in mono- and co-culture with human coronary artery endothelial cells (HCAECs) in a double-flow bioreactor (LiveBox2 and IVTech), allowing static and dynamic conditions through a peristaltic pump. The VC was stimulated by incubation in a calcifying medium for 7 days. A BMP system Real-Time PCR was performed at the end of each experiment.

RESULTS

In monocultures, BMP-2 expression increased in calcified HCASMCs in static (p = 0.01) and dynamic conditions. BMP-4 and the biological receptors were expressed in all the experimental settings, increasing mainly in dynamic flow conditions. In co-cultures, we observed a marked increase in BMP-2 and BMP-4, BMPR-1a (p = 0.04 and p = 0.01, respectively), and BMPR-2 (p = 0.001) in the calcifying setting mostly in dynamic conditions.

CONCLUSIONS

The increase in BMP-2/4 in co-culture suggests that these genes might promote the switch towards an osteogenic-like phenotype, data also supported by the rise of both BMPR-1a and BMPR-2. Thus, our findings provide insights into the mechanisms by which dynamic co-culture modulates the BMP system activation in an environment mimicking in vivo VC's cellular and mechanical characteristics.

The Physiological Functions and Therapeutic Potential of Hypoxia-Inducible Factor-1α in Vascular Calcification

HIF-1α plays a crucial regulatory role in vascular calcification (VC), primarily influencing the osteogenic differentiation of VSMCs through oxygen-sensing mechanisms. Under hypoxic conditions, the stability of HIF-1α increases, avoiding PHD and VHL protein-mediated degradation, which promotes its accumulation in cells and then activates gene expressions related to calcification. Additionally, HIF-1α modulates the metabolic state of VSMCs by regulating the pathways that govern the switch between glycolysis and oxidative phosphorylation, thereby further advancing the calcification process. The interaction between HIF-1α and other signaling pathways, such as nuclear factor-κB, Notch, and Wnt/β-catenin, creates a complex regulatory network that serves as a critical driving force in VC. Therefore, a deeper understanding of the role and regulatory mechanism of the HIF-1α signaling during the development and progression of VC is of great significance, as it is not only a key molecular marker for understanding the pathological mechanisms of VC but also represents a promising target for future anti-calcification therapies.

Gla-Rich Protein Is Associated with Vascular Calcification, Inflammation, and Mineral Markers in Peritoneal Dialysis Patients

Background/Objectives: Vascular calcification (VC) is a crucial risk factor for cardiovascular diseases (CVD), particularly in chronic kidney disease (CKD) populations. However, the specific relationship between VC and end-stage renal disease (ESRD) patients undergoing peritoneal dialysis (PD) remains to be fully understood. The identification of new biomarkers to improve VC diagnosis and monitoring would significantly impact cardiovascular risk management in these high-risk patients. Gla-rich protein (GRP) is a VC inhibitor and an anti-inflammatory agent and thus is a potential VC marker in CKD. Here we explored the potential role of GRP as a marker for CVD and investigated the impact of VC in 101 PD patients. Methods: Circulating total Gla-rich protein (tGRP) was quantified in serum and in 24 h dialysate samples. VC score (VCS) was determined using the Adragão method. Results: Serum tGRP was negatively associated with VCS, serum calcium (Ca), phosphate (P), and high-sensitivity C-reactive protein (hsCRP), while it was positively associated with magnesium (Mg). A total of 35.6% of PD patients presented with extensive calcifications (VCS ≥ 3), and the lowest tGRP serum levels were present in this group (419.4 ± 198.5 pg/mL). tGRP in the 24 h dialysate was also negatively associated with VCS and with serum Ca and P. Moreover, serum Ca, P, and VCS were identified as independent determinants of serum tGRP levels. Conclusions: The association of serum tGRP with VC, mineral, and inflammation markers reinforces its potential use as a novel VC biomarker in CKD patients undergoing PD.

Objective Methods to Assess Aorto-Iliac Calcifications: A Systematic Review

Vascular calcifications in aorto-iliac arteries are emerging as crucial risk factors for cardiovascular diseases (CVDs) with profound clinical implications. This systematic review, following PRISMA guidelines, investigated methodologies for measuring these calcifications and explored their correlation with CVDs and clinical outcomes. Out of 698 publications, 11 studies met the inclusion criteria. In total, 7 studies utilized manual methods, while 4 studies utilized automated technologies, including artificial intelligence and deep learning for image analyses. Age, systolic blood pressure, serum calcium, and lipoprotein(a) levels were found to be independent risk factors for aortic calcification. Mortality from CVDs was correlated with abdominal aorta calcification. Patients requiring reintervention after endovascular recanalization exhibited a significantly higher volume of calcification in their iliac arteries. Conclusions: This review reveals a diverse landscape of measurement methods for aorto-iliac calcifications; however, they lack a standardized reproducibility assessment. Automatic methods employing artificial intelligence appear to offer broader applicability and are less time-consuming. Assessment of calcium scoring could be routinely employed during preoperative workups for risk stratification and detailed surgical planning. Additionally, its correlation with clinical outcomes could be useful in predicting the risk of reinterventions and amputations.

Bisphenol A accelerates the vascular complications in patients with Type 2 diabetes mellitus through vascular calcification-a molecular approach

PURPOSE

Environmental pollutant Bisphenol A (BPA) strongly interacts with insulin resistance, which leads to type 2 diabetes mellitus (T2DM). Uncontrolled glucose levels in both blood and urine develops vascular complications in T2DM patients. However, glucose-controlled diabetic patients are also affected by vascular complications due to vascular calcification, and there is a lack of clinically relevant data on BPA levels available in patients with T2DM-associated vascular complications due to vascular calcification. Therefore, we measured BPA levels in T2DM-associated vascular complications and correlated systemic BPA levels with vascular calcification-related gene expression.

METHODS

This study included 120 participants with T2DM and its associated vascular complications. Serum and urinary BPA were estimated using an ELISA kit, and gene expression of the study participants in peripheral blood mononuclear cells (PBMCs) was studied with quantitative real-time PCR.

RESULTS

Serum and urinary BPA levels were higher in T2DM and its associated vascular complications with CVD and DN patients compared to control. Both Serum and urinary BPA had higher significance with Sirt1 (p < 0.001, p < 0.001), Runx2 (p < 0.01, p < 0.001) and IL-1beta (p < 0.001, p < 0.02) gene expression in the study groups, but, TNF-alpha significant with Serum BPA (p < 0.04), not urinary BPA (p < 0.31).

CONCLUSION

BPA levels were positively correlated with lower Sirt1 and increased Runx2 in T2DM-associated vascular complications patients. Also, higher expression of IL-1beta and TNF-alpha was observed in T2DM-associated vascular complications patients. Our study is the first to associate BPA levels with vascular calcification in patients with T2DM and its associated vascular complications.

Statin Use and Coronary Artery Calcification: a Systematic Review and Meta-analysis of Observational Studies and Randomized Controlled Trials

PURPOSE OF REVIEW

This review aimed to determine the association between statin use and coronary artery calcification (CAC), as detected by computed tomography in the general population, in previously published observational studies (OSs) and randomized controlled trials (RCTs).

RECENT FINDINGS

A systematic search until February 2022 identified 41 relevant studies, comprising 29 OSs and 12 RCTs. We employed six meta-analysis models, stratifying studies based on design and effect metrics. For cohort studies, the pooled β of the association with CAC quantified by the Agatston score was 0.11 (95% CI = 0.05; 0.16), with an average follow-up time per person (AFTP) of 3.68 years. Cross-sectional studies indicated a pooled odds ratio of 2.11 (95% CI = 1.61; 2.78) for the presence of CAC. In RCTs, the pooled standardized mean differences (SMDs) for CAC, quantified by Agatston score or volume, over and AFTP of 1.25 years were not statistically significant (SMD =  - 0.06, 95% CI =  - 0.19; 0.06 and SMD = 0.26, 95% CI =  - 0.66; 1.19), but significantly different (p-value = 0.04). Meta-regression and subgroup analyses did not show any significant differences in pooled estimates across covariates. The effect of statins on CAC differs across study designs. OSs demonstrate associations between statin use and higher CAC scores and presence while being prone to confounding by indication. Effects from RCTs do not reach statistical significance and vary depending on the quantification method, hampering drawing conclusions. Further investigations are required to address the limitations inherent in each approach.

The therapeutic potential of sphingolipids for cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide and Inflammation plays a critical role in the development of CVD. Despite considerable progress in understanding the underlying mechanisms and various treatment options available, significant gaps in therapy necessitate the identification of novel therapeutic targets. Sphingolipids are a family of lipids that have gained attention in recent years as important players in CVDs and the inflammatory processes that underlie their development. As preclinical studies have shown that targeting sphingolipids can modulate inflammation and ameliorate CVDs, targeting sphingolipids has emerged as a promising therapeutic strategy. This review discusses the current understanding of sphingolipids' involvement in inflammation and cardiovascular diseases, the existing therapeutic approaches and gaps in therapy, and explores the potential of sphingolipids-based drugs as a future avenue for CVD treatment.

Comparative analysis of calcified soft tissues revealed shared deregulated pathways

Introduction

Calcification of soft tissues is a common age-related pathology that primarily occurs within vascular tissue. The mechanisms underlying pathological calcification in humans and tissue specificity of the process is still poorly understood. Previous studies examined calcified tissues on one to one basis, thus preventing comparison of deregulated pathways across tissues.

Purpose

This study aimed to establish common and tissue-specific changes associated with calcification in aorta, artery tibial, coronary artery and pituitary gland in subjects from the Genotype-Tissue Expression (GTEx) dataset using its RNA sequencing and histological data.

Methods

We used publicly available data from the GTEx database https://gtexportal.org/home/aboutGTEx. All GTEx tissue samples were derived by the GTEx consorcium from deceased donors, with age from 20 to 79, both men and women. GTEx study authorization was obtained via next-of-kin consent for the collection and banking of de-identified tissue samples for scientific research. Hematoxylin and eosin (H&E) staining of arteries were manually graded based on the presence of calcification on a scale from zero to four, where zero designates absence of calcification and four designates severe calcification. Samples with fat contamination and mislabeled tissues were excluded, which left 430 aorta, 595 artery tibial, 124 coronary artery, and 283 pituitary samples for downstream gene expression analysis. Transcript levels of protein-coding genes were associated with calcification grade using sex, age bracket and cause of death as covariates, and tested for pathway enrichment using gene set enrichment analysis.

Results

We identified calcification deposits in 28 (6.5%) aortas, 121 (20%), artery tibials, 54 (43%), coronary arteries, and 24 (8%) pituitary glands of GTEx subjects. We observed an age-dependent increase in incidence of calcification in all vascular tissues, but not in pituitary. Subjects with calcification in the artery tibial were significantly more likely to have calcification in the coronary artery (OR = 2.56, p = 6.3e-07). Markers of calcification previously established in preclinical and in vitro studies, e.g., BMP2 and RUNX2, were deregulated in the calcified tibial and coronary arteries, confirming the relevance of these genes to human pathology. Differentially expressed genes associated with calcification poorly overlapped across tissues suggesting tissue-specific nuances in mechanisms of calcification. Nevertheless, calcified arteries unanimously down-regulated pathways of intracellular transport and up-regulated inflammatory pathways suggesting these as universal targets for pathological calcification. In particular, PD-1 and PD-L1 genes were up-regulated in calcified tissues but not in the blood of the same subjects, suggesting that localized inflammation contributes to pathological calcification.

Conclusion

Pathological calcification is a prevalent disease of aging that shares little changes in expression in individual genes across tissues. However, our analysis suggests that it potentially can be targeted by alleviating local inflammation of soft tissues.

Could hypoxia rehabilitate the osteochondral diseased interface? Lessons from the interplay of hypoxia and purinergic signals elsewhere

The osteochondral unit comprises the articular cartilage (90%), subchondral bone (5%) and calcified cartilage (5%). All cells present at the osteochondral unit that is ultimately responsible for matrix production and osteochondral homeostasis, such as chondrocytes, osteoblasts, osteoclasts and osteocytes, can release adenine and/or uracil nucleotides to the local microenvironment. Nucleotides are released by these cells either constitutively or upon plasma membrane damage, mechanical stress or hypoxia conditions. Once in the extracellular space, endogenously released nucleotides can activate membrane-bound purinoceptors. Activation of these receptors is fine-tuning regulated by nucleotides' breakdown by enzymes of the ecto-nucleotidase cascade. Depending on the pathophysiological conditions, both the avascular cartilage and the subchondral bone subsist to significant changes in oxygen tension, which has a tremendous impact on tissue homeostasis. Cell stress due to hypoxic conditions directly influences the expression and activity of several purinergic signalling players, namely nucleotide release channels (e.g. Cx43), NTPDase enzymes and purinoceptors. This review gathers experimental evidence concerning the interplay between hypoxia and the purinergic signalling cascade contributing to osteochondral unit homeostasis. Reporting deviations to this relationship resulting from pathological alterations of articular joints may ultimately unravel novel therapeutic targets for osteochondral rehabilitation. At this point, one can only hypothesize how hypoxia mimetic conditions can be beneficial to the ex vivo expansion and differentiation of osteo- and chondro-progenitors for auto-transplantation and tissue regenerative purposes.

p53 Regulates Mitochondrial Dynamics in Vascular Smooth Muscle Cell Calcification

Arterial calcification is an important characteristic of cardiovascular disease. It has key parallels with skeletal mineralization; however, the underlying cellular mechanisms responsible are not fully understood. Mitochondrial dynamics regulate both bone and vascular function. In this study, we therefore examined mitochondrial function in vascular smooth muscle cell (VSMC) calcification. Phosphate (Pi)-induced VSMC calcification was associated with elongated mitochondria (1.6-fold increase, p < 0.001), increased mitochondrial reactive oxygen species (ROS) production (1.83-fold increase, p < 0.001) and reduced mitophagy (9.6-fold decrease, p < 0.01). An increase in protein expression of optic atrophy protein 1 (OPA1; 2.1-fold increase, p < 0.05) and a converse decrease in expression of dynamin-related protein 1 (DRP1; 1.5-fold decrease, p < 0.05), two crucial proteins required for the mitochondrial fusion and fission process, respectively, were noted. Furthermore, the phosphorylation of DRP1 Ser637 was increased in the cytoplasm of calcified VSMCs (5.50-fold increase), suppressing mitochondrial translocation of DRP1. Additionally, calcified VSMCs showed enhanced expression of p53 (2.5-fold increase, p < 0.05) and β-galactosidase activity (1.8-fold increase, p < 0.001), the cellular senescence markers. siRNA-mediated p53 knockdown reduced calcium deposition (8.1-fold decrease, p < 0.01), mitochondrial length (3.0-fold decrease, p < 0.001) and β-galactosidase activity (2.6-fold decrease, p < 0.001), with concomitant mitophagy induction (3.1-fold increase, p < 0.05). Reduced OPA1 (4.1-fold decrease, p < 0.05) and increased DRP1 protein expression (2.6-fold increase, p < 0.05) with decreased phosphorylation of DRP1 Ser637 (3.20-fold decrease, p < 0.001) was also observed upon p53 knockdown in calcifying VSMCs. In summary, we demonstrate that VSMC calcification promotes notable mitochondrial elongation and cellular senescence via DRP1 phosphorylation. Furthermore, our work indicates that p53-induced mitochondrial fusion underpins cellular senescence by reducing mitochondrial function.

Circulating uncarboxylated matrix Gla protein in patients with atrial fibrillation or heart failure with preserved ejection fraction

CONTEXT

Circulating uncarboxylated matrix Gla protein (ucMGP) is possibly related to coronary arterial calcification (CAC) in cardiovascular disease (CVD) patients.

OBJECTIVE

We aimed to evaluate the relationships between circulating ucMGP, CVD pathology and CAC and its interplay with CVD risk factors.

MATERIALS AND METHODS

ucMGP was measured in 99 CVD-patients. CAC score was determined by multislice computed tomography. Circulating ucMGP, uncarboxylated (ucOC) and carboxylated osteocalcin (cOC) were assayed by ELISA kits. Vitamin-K status was evaluated by ucOC/cOC ratio.

RESULTS

A tendency for decreased ucMGP was observed for CAC ≥ 100 AU vs. CAC = 1-99 AU after exclusion of the patients on vitamin K-antagonist anticoagulants. Significant inverse correlations between ucMGP and vitamin-K status were indicated for the entire cohort and according to CAC score. Significant associations were found between ucMGP and risk factors for CVD.

CONCLUSION

Circulating ucMGP may reflect certain stages of CVD and CAC. Future studies are needed to clarify its role as potential biomarker.

Distinct role of mitochondrial function and protein kinase C in intimal and medial calcification in vitro

Introduction

Vascular calcification (VC) is a major risk factor for cardiovascular morbidity and mortality. Depending on the location of mineral deposition within the arterial wall, VC is classified as intimal and medial calcification. Using in vitro mineralization assays, we developed protocols triggering both types of calcification in vascular smooth muscle cells (SMCs) following diverging molecular pathways.

Materials and methods and results

Human coronary artery SMCs were cultured in osteogenic medium (OM) or high calcium phosphate medium (CaP) to induce a mineralized extracellular matrix. OM induces osteoblast-like differentiation of SMCs-a key process in intimal calcification during atherosclerotic plaque remodeling. CaP mimics hyperphosphatemia, associated with chronic kidney disease-a risk factor for medial calcification. Transcriptomic analysis revealed distinct gene expression profiles of OM and CaP-calcifying SMCs. OM and CaP-treated SMCs shared 107 differentially regulated genes related to SMC contraction and metabolism. Real-time extracellular efflux analysis demonstrated decreased mitochondrial respiration and glycolysis in CaP-treated SMCs compared to increased mitochondrial respiration without altered glycolysis in OM-treated SMCs. Subsequent kinome and in silico drug repurposing analysis (Connectivity Map) suggested a distinct role of protein kinase C (PKC). In vitro validation experiments demonstrated that the PKC activators prostratin and ingenol reduced calcification triggered by OM and promoted calcification triggered by CaP.

Conclusion

Our direct comparison results of two in vitro calcification models strengthen previous observations of distinct intracellular mechanisms that trigger OM and CaP-induced SMC calcification in vitro. We found a differential role of PKC in OM and CaP-calcified SMCs providing new potential cellular and molecular targets for pharmacological intervention in VC. Our data suggest that the field should limit the generalization of results found in in vitro studies using different calcification protocols.

Molecular Imaging and Quantification of Smooth Muscle Cell and Aortic Tissue Calcification In Vitro and Ex Vivo with a Fluorescent Hydroxyapatite-Specific Probe

Vessel calcification is characterized by the precipitation of hydroxyapatite (HAP) in the vasculature. Currently, no causal therapy exists to reduce or prevent vessel calcification. Studying the underlying pathways within vascular smooth muscle cells and testing pharmacological intervention is a major challenge in the vascular research field. This study aims to establish a rapid and efficient working protocol for specific HAP detection in cells and tissue using the synthetic bisphosphonate fluorescence dye OsteoSense™. This protocol facilitates especially early quantification of the fluorescence signal and permits co-staining with other markers of interest, enabling smaller experimental set-ups with lesser primary cells consumption and fast workflows. The fluorescence-based detection of vascular calcification with OsteoSense™ combines a high specificity with improved sensitivity. Therefore, this methodology can improve research of the pathogenesis of vascular calcification, especially for testing the therapeutic benefit of inhibitors in the case of in vitro and ex vivo settings.

Case Report: Unable to Jump Like a Kangaroo Due to Myositis Ossificans Circumscripta

A male 10-year-old captive red kangaroo (Macropus rufus) was presented with a chronic progressive pelvic limb lameness and reluctance to jump. The general examination revealed a palpable induration of the lumbar epaxial muscles. Magnetic resonance imaging performed under general anesthesia revealed bilateral almost symmetric, well-circumscribed mass lesions in superficial erector spinae muscles. The lesions had irregular to multilobulated appearance with hyper-, hypo-, and isointense areas in T2- and T1-weighted (w) sequences without contrast enhancement. On computed tomography, a peripheral rim of mineralization was apparent. Histopathological analysis of a muscle biopsy showed osseous trabeculae with rare clusters of chondrocytes indicating metaplasia of muscle tissue to bone. No indications of inflammation or malignancy were visible. The clinical, histopathological, and imaging workup of this case was consistent with myositis ossificans circumscripta. This disorder is particularly well-known among human professional athletes such as basketball players, where excessive, chronic-repetitive force or blunt trauma causes microtrauma to the musculature. Metaplasia of muscle tissue due to abnormal regeneration processes causes heterotopic ossification. The kangaroo's clinical signs improved with cyto-reductive surgery, cage rest, weight reduction, and meloxicam without further relapse.

A Reproducible Mouse Model of Moderate CKD With Early Manifestations of Osteoblastic Transition of Cardiovascular System

Chronic kidney disease (CKD) is a significant public health challenge with a substantial associated risk of mortality, morbidity, and health care expenditure. Culprits that lead to development and progression of CKD are multifaceted and heterogenous in nature. This notion underscores the need for diversification of animal models to investigate its pathophysiology, related complications, and to subsequently enable discovery of novel therapeutics. Importantly, animal models that could recapitulate complications of CKD in both genders are desperately needed. Cardiovascular disease is the most common cause of death in CKD patients that may be due in part to high prevalence of vascular calcification (VC). Using DBA/2 mice that are susceptible to development of VC, we sought to investigate the feasibility and reproducibility of a unilateral ischemia-reperfusion model followed by contralateral nephrectomy (UIRI/Nx) to induce CKD and its related complications in female and male mice. Our results demonstrate that irrespective of gender, mice faithfully displayed complications of moderate CKD following UIRI/Nx as evidenced by significant rise in serum creatinine, albuminuria, higher degree of collagen deposition, elevated expression of classic fibrotic markers, higher circulating levels of FGF-23, PTH and hepcidin. Moreover, we corroborate the osteoblastic transition of aortic smooth muscle cells and cardiomyocytes based on higher levels of osteoblastic markers namely, Cbfa-1, osteopontin, osteocalcin, and osterix. Our data confirms a viable, and consistent model of moderate CKD and its associated complications in both male and female mice. Furthermore, early evidence of osteoblastic transition of cardiovascular system in this model confirms its suitability for studying and implementing potential preventive and/or therapeutic approaches that are urgently needed in this field.

Pro-Calcific Environment Impairs Ischaemia-Driven Angiogenesis

Peripheral arterial disease (PAD) is characterised by accelerated arterial calcification and impairment in angiogenesis. Studies implicate vascular calcification as a contributor to PAD, but the mechanisms remain unclear. We aimed to determine the effect of calcification on ischaemia-driven angiogenesis. Human coronary artery endothelial cells (ECs) were treated with calcification medium (CM: CaCl₂ 2.7 mM, Na₂PO₄ 2.0 mM) for 24 h and exposed to normoxia (5% CO₂) or hypoxia (1.2% O₂; 5% CO₂ balanced with N₂). In normoxia, CM significantly inhibited tubule formation and migration and upregulated calcification markers of ALP, BMP2, and Runx2. CM elevated levels of calcification-protective gene OPG, demonstrating a compensatory mechanism by ECs. CM failed to induce pro-angiogenic regulators VEGFA and HIF-1α in hypoxia and further suppressed the phosphorylation of endothelial nitric oxide synthase (eNOS) that is essential for vascular function. In vivo, osteoprotegerin-deficient mice (OPG^−/−), a calcification model, were subjected to hind-limb ischaemia (HLI) surgery. OPG^−/− mice displayed elevated serum alkaline phosphatase (ALP) activity compared to wild-type controls. OPG^−/− mice experienced striking reductions in blood-flow reperfusion in both 8-week-old and 6-month-old mice post-HLI. This coincided with significant impairment in tissue ischaemia and reduced limb function as assessed by clinical scoring (Tarlov). This study demonstrated for the first time that a pro-calcific environment is detrimental to ischaemia-driven angiogenesis. The degree of calcification in patients with PAD can often be a limiting factor with the use of standard therapies. These highly novel findings require further studies for full elucidation of the mechanisms involved and have implications for the development of therapies to suppress calcification in PAD.

Gla-Rich Protein, Magnesium and Phosphate Associate with Mitral and Aortic Valves Calcification in Diabetic Patients with Moderate CKD

Accelerated and premature cardiovascular calcification is a hallmark of chronic kidney disease (CKD) patients. Valvular calcification (VC) is a critical indicator of cardiovascular disease and all-cause mortality in this population, lacking validated biomarkers for early diagnosis. Gla-rich protein (GRP) is a cardiovascular calcification inhibitor recently associated with vascular calcification, pulse pressure, mineral metabolism markers and kidney function. Here, we examined the association between GRP serum levels and mitral and aortic valves calcification in a cohort of 80 diabetic patients with CKD stages 2-4. Mitral and aortic valves calcification were detected in 36.2% and 34.4% of the patients and associated with lower GRP levels, even after adjustments for age and gender. In this pilot study, univariate, multivariate and Poisson regression analysis, show that low levels of GRP and magnesium (Mg), and high levels of phosphate (P) are associated with mitral and aortic valves calcification. Receiver operating characteristic (ROC) curves showed that the area under the curve (AUC) values of GRP for mitral (0.762) and aortic (0.802) valves calcification were higher than those of Mg and P. These results suggest that low levels of GRP and Mg, and high levels of P, are independent and cumulative risk factors for VC in this population; the GRP diagnostic value might be potentially useful in cardiovascular risk assessment.

Klotho deficiency-induced arterial calcification involves osteoblastic transition of VSMCs and activation of BMP signaling

Klotho is an aging-suppressor gene. The purpose of this study was to investigate whether Klotho deficiency affects arterial structure. We found that Klotho-deficient (kl/kl) mice developed severe arterial calcification and elastin fragmentation. Klotho-deficient mice demonstrated higher levels of bone morphogenetic proteins (BMP2, BMP4) and runt-related transcription factor 2 (RUNX2) in aortas, indicating that Klotho deficiency upregulates expression of BMP2 and RUNX2 (a key transcription factor in osteoblasts). To exclude the potential involvement of hyperphosphatemia in arterial calcification, Klotho-deficient mice were given a low phosphate diet (0.2%). The low phosphate diet normalized blood phosphate levels and abolished calcification in the lungs and kidneys, but it did not prevent calcification in the aortas in Klotho-deficient mice. Thus, Klotho deficiency per se might play a causal role in the pathogenesis of arterial calcification, which is independent of hyperphosphatemia. In cultured mouse aortic smooth muscle cells (ASMCs), Klotho-deficient serum-induced transition of ASMCs to osteoblasts. Klotho-deficient serum promoted BMP2/vitamin D3-induced protein expression of PIT2 and RUNX2, phosphorylation of SMAD1/5/8 and SMAD2/3, and extracellular matrix calcification. Interestingly, treatments with recombinant Klotho protein abolished BMP2/vitamin D3-induced osteoblastic transition and morphogenesis and calcification. Therefore, Klotho is a critical regulator in the maintenance of normal arterial homeostasis. Klotho deficiency-induced arterial calcification is an active process that involves the osteoblastic transition of SMCs and activation of the BMP2-RUNX2 signaling.

Restoration of 5-methoxytryptophan protects against atherosclerotic chondrogenesis and calcification in ApoE-/- mice fed high fat diet

Background

Toll-like receptor-2 (TLR2) promotes vascular smooth muscle cell (VSMC) transdifferentiation to chondrocytes and calcification in a p38 MAPK-dependent manner. Vascular 5-methoxytryptophan (5-MTP) is a newly identified factor with anti-inflammatory actions. As 5-MTP targets p38 MAPK for its actions, we postulated that 5-MTP protects against vascular chondrogenesis and calcification.

Methods

High-fat diet-induced advanced atherosclerosis in mice were performed to investigate the effect of 5-MTP on atherosclerotic lesions and calcification. VSMCs were used to determine the role of 5-MTP in VSMC chondrogenic differentiation and calcification. Alizarin red S and Alcian blue staining were used to measure VSMC calcification and chondrogenic differentiation, respectively.

Results

5-MTP was detected in aortic tissues of ApoE^−/− mice fed control chow. It was reduced in ApoE^−/− mice fed high-fat diet (HFD), but was restored in ApoE^−/−Tlr2^−/− mice, suggesting that HFD reduces vascular 5-MTP production via TLR2. Intraperitoneal injection of 5-MTP or its analog into ApoE^−/− mice fed HFD reduced aortic atherosclerotic lesions and calcification which was accompanied by reduction of chondrogenesis and calcium deposition. Pam3CSK4 (Pam3), ligand of TLR2, induced SMC phenotypic switch to chondrocytes. Pretreatment with 5-MTP preserved SMC contractile proteins and blocked Pam3-induced chondrocyte differentiation and calcification. 5-MTP inhibited HFD-induced p38 MAPK activation in vivo and Pam3-induced p38 MAPK activation in SMCs. 5-MTP suppressed HFD-induced CREB activation in aortic tissues and Pam3-induced CREB and NF-κB activation in SMCs.

Conclusions

These findings suggest that 5-MTP is a vascular arsenal against atherosclerosis and calcification by inhibiting TLR2–mediated SMC phenotypic switch to chondrocytes and the consequent calcification. 5-MTP exerts these effects by blocking p38 MAPK activation and inhibiting CREB and NF-κB transactivation activity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-021-00771-1.

Osteoclast-Mediated Cell Therapy as an Attempt to Treat Elastin Specific Vascular Calcification

Inflammation and stiffness in the arteries is referred to as vascular calcification. This process is a prevalent yet poorly understood consequence of cardiovascular disease and diabetes mellitus, comorbidities with few treatments clinically available. Because this is an active process similar to bone formation, it is hypothesized that osteoclasts (OCs), bone-resorbing cells in the body, could potentially work to reverse existing calcification by resorbing bone material. The receptor activator of nuclear kappa B-ligand (RANKL) is a molecule responsible for triggering a response in monocytes and macrophages that allows them to differentiate into functional OCs. In this study, OC and RANKL delivery were employed to determine whether calcification could be attenuated. OCs were either delivered via direct injection, collagen/alginate microbeads, or collagen gel application, while RANKL was delivered via injection, through either a porcine subdermal model or aortic injury model. While in vitro results yielded a decrease in calcification using OC therapy, in vivo delivery mechanisms did not provide control or regulation to keep cells localized long enough to induce calcification reduction. However, these results do provide context and direction for the future of OC therapy, revealing necessary steps for this treatment to effectively reduce calcification in vivo. The discrepancy between in vivo and in vitro success for OC therapy points to the need for a more stable and time-controlled delivery mechanism that will allow OCs not only to remain at the site of calcification, but also to be regulated so that they are healthy and functioning normally when introduced to diseased tissue.

Procyanidin B2 Reduces Vascular Calcification through Inactivation of ERK1/2-RUNX2 Pathway

Vascular calcification is strongly associated with atherosclerotic plaque burden and plaque instability. The activation of extracellular signal-regulated kinase 1/2 (ERK1/2) increases runt related transcription factor 2 (RUNX2) expression to promote vascular calcification. Procyanidin B2 (PB2), a potent antioxidant, can inhibit ERK1/2 activation in human aortic smooth muscle cells (HASMCs). However, the effects and involved mechanisms of PB2 on atherosclerotic calcification remain unknown. In current study, we fed apoE-deficient (apoE^−/−) mice a high-fat diet (HFD) while treating the animals with PB2 for 18 weeks. At the end of the study, we collected blood and aorta samples to determine atherosclerosis and vascular calcification. We found PB2 treatment decreased lesions in en face aorta, thoracic, and abdominal aortas by 21.4, 24.6, and 33.5%, respectively, and reduced sinus lesions in the aortic root by 17.1%. PB2 also increased α-smooth muscle actin expression and collagen content in lesion areas. In the aortic root, PB2 reduced atherosclerotic calcification areas by 75.8%. In vitro, PB2 inhibited inorganic phosphate-induced osteogenesis in HASMCs and aortic rings. Mechanistically, the expression of bone morphogenetic protein 2 and RUNX2 were markedly downregulated by PB2 treatment. Additionally, PB2 inhibited ERK1/2 phosphorylation in the aortic root plaques of apoE^−/− mice and calcified HASMCs. Reciprocally, the activation of ERK1/2 phosphorylation by C2-MEK1-mut or epidermal growth factor can partially restore the PB2-inhibited RUNX2 expression or HASMC calcification. In conclusion, our study demonstrates that PB2 inhibits vascular calcification through the inactivation of the ERK1/2-RUNX2 pathway. Our study also suggests that PB2 can be a potential option for vascular calcification treatment.

Monckeberg's Medial Sclerosis as a Cause for Headache and Facial Pain

PURPOSE OF REVIEW

Mönckeberg's medial sclerosis (MMS) is a chronic, non-inflammatory degenerative condition affecting primarily the tunica media of muscular arteries resulting in their calcification. The purpose of this comprehensive review is to describe MMS as it appears in the literature, in the context of headache and facial pain. Understanding the etiopathology, the associated conditions, and the differential diagnoses is important in managing MMS.

RECENT FINDINGS

Management of MMS primarily depends upon identification of its associated conditions and their treatment. Due to the rare incidence and inadequate literature on MMS presenting with headaches, the diagnosis of the pain and the entity itself is challenging. MMS is characterized by associated systemic conditions and absence of inflammatory markers. It can mimic giant cell arteritis (GCA) and other pain entities. An interdisciplinary approach involving appropriate specialties is recommended.

Plasma osteopontin versus intima media thickness of the common carotid arteries in well-characterised patients with systemic lupus erythematosus

Objective

The progress of accelerated atherosclerosis in systemic lupus erythematosus (SLE) is incompletely understood. Circulating osteopontin (OPN) is increased in autoimmune conditions, e.g. SLE, and its serum concentration was recently reported to associate with subclinical atherosclerosis in SLE, as measured by carotid intima-media thickness. The aim of this study was to investigate whether OPN may be used as a surrogate biomarker of subclinical atherosclerosis in SLE patients with different disease phenotypes.

Methods

We recruited 60 well-characterised SLE cases and 60 age- and sex-matched healthy controls. The SLE cases were divided into three different disease phenotypes: SLE with antiphospholipid syndrome (APS), lupus nephritis, and isolated skin and joint involvement. Plasma OPN was detected by ELISA (Quantikine®, R&D Systems). Common carotid arteries intima media thickness was compared between the studied groups in relation to OPN levels and risk factors for vascular changes. Intima media thickness of common carotid arteries was measured by using a sensitive ultrasound technique (LOGIQ™ E9 ultrasound, GE Healthcare).

Results

OPN levels were significantly higher among the entire SLE group (n = 60) compared to the healthy controls (P = 0.03). SLE cases with concomitant APS (n = 20) showed higher OPN levels than the controls (P = 0.004), whereas none of the other two subgroups differed significantly from the healthy controls. OPN and intima media thickness were correlated to several traditional risk factors of atherosclerosis, as well as to SLE-related factors. Yet, no significant correlation was observed between OPN levels and ultrasound findings of the common carotid arteries.

Conclusions

In line with previous studies, we observed increased OPN levels among SLE patients as compared to matched controls. However, the OPN concentrations did not correlate with intima media thickness of the common carotid arteries. Based on our findings, the use of OPN as a surrogate biomarker of subclinical atherosclerosis in SLE subjects, regardless of clinical phenotypes, cannot be recommended.

Prevention of Vascular Calcification by Magnesium and Selected Polyphenols

Arterial vascular calcification (VC) represents formation of calcium phosphate deposits on the interior of arteries, which could restrict blood flow leading to heart health problems, including morbidity and mortality. VC is a complex and tightly regulated process that involves transformation of vascular smooth muscle cells (VSMCs) to bone-like cells and subsequent deposition of calcium as hydroxyapatite. Natural bioactives, including quercetin (Q), curcumin (C), resveratrol (R), and magnesium (Mg), have been reported to inhibit VC. Thus, we conducted an in vitro study using rat vascular smooth muscle cells (rVSMCs) to evaluate the protective effect of natural bioactives found in OptiCel, that is, Mg combined with polyphenols (PPs), Q, C, and R. Calcification was induced by culturing rVSMCs in a high phosphate (HP) medium. The addition of Mg and Q + C + R separately decreased the HP-induced calcium deposition by 37.55% and 42.78%, respectively. In contrast, when Mg was combined with Q, C, and R, the inhibition of calcium deposition was decreased by 92.88%, which is greater than their calculated additive inhibition (80.33%). These results demonstrate that the combination of Mg with selected PPs (Q, C, and R) is more effective than when used separately. The findings also suggest the combination has a synergistic effect in inhibiting VC, which is a risk factor for cardiovascular disease. Thus, regular consumption of these natural bioactives could have a beneficial effect in reducing the development of heart diseases.

Hydrolysis of Extracellular ATP by Vascular Smooth Muscle Cells Transdifferentiated into Chondrocytes Generates Pi but Not PPi

(1) Background: Tissue non-specific alkaline phosphatase (TNAP) is suspected to induce atherosclerosis plaque calcification. TNAP, during physiological mineralization, hydrolyzes the mineralization inhibitor inorganic pyrophosphate (PP_i). Since atherosclerosis plaques are characterized by the presence of necrotic cells that probably release supraphysiological concentrations of ATP, we explored whether this extracellular adenosine triphosphate (ATP) is hydrolyzed into the mineralization inhibitor PP_i or the mineralization stimulator inorganic phosphate (P_i), and whether TNAP is involved. (2) Methods: Murine aortic smooth muscle cell line (MOVAS cells) were transdifferentiated into chondrocyte-like cells in calcifying medium, containing ascorbic acid and β-glycerophosphate. ATP hydrolysis rates were determined in extracellular medium extracted from MOVAS cultures during their transdifferentiation, using ³¹P-NMR and IR spectroscopy. (3) Results: ATP and PP_i hydrolysis by MOVAS cells increased during transdifferentiation. ATP hydrolysis was sequential, yielding adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine without any detectable PP_i. The addition of levamisole partially inhibited ATP hydrolysis, indicating that TNAP and other types of ectonucleoside triphoshatediphosphohydrolases contributed to ATP hydrolysis. (4) Conclusions: Our findings suggest that high ATP levels released by cells in proximity to vascular smooth muscle cells (VSMCs) in atherosclerosis plaques generate P_i and not PP_i, which may exacerbate plaque calcification.

Carotid Atherosclerosis in Predicting Coronary Artery Disease: A Systematic Review and Meta-Analysis

[Figure: see text].

Undercarboxylated osteocalcin has no adverse effect on endothelial function in rabbit aorta or human vascular cells

Undercarboxylated osteocalcin (ucOC) improves glucose metabolism; however, its effects on endothelial cell function are unclear. We examined the biological effect of ucOC on endothelial function in animal models ex vivo and human cells in vitro. Isometric tension and immunohistochemistry techniques were used on the aorta of male New Zealand white rabbits and cell culture techniques were used on human aortic endothelial cells (HAECs) to assess the effect of ucOC in normal and high-glucose environments. Overall, ucOC, both 10 and 30 ng/ml, did not significantly alter acetylcholine-induced blood vessel relaxation in rabbits (p > .05). UcOC treatment did not cause any significant changes in the immunoreactivity of cellular signalling markers (p > .05). In HAEC, ucOC did not change any of the assessed outcomes (p > .05). UcOC has no negative effects on endothelial function which is important to reduce the risks of off target adverse effects if it will be used as a therapeutic option for metabolic disease in the future.

Expression of Calcification and Extracellular Matrix Genes in the Cardiovascular System of the Healthy Domestic Sheep (Ovis aries)

The maintenance of a healthy cardiovascular system requires expression of genes that contribute to essential biological activities and repression of those that are associated with functions likely to be detrimental to cardiovascular homeostasis. Vascular calcification is a major disruption to cardiovascular homeostasis, where tissues of the cardiovascular system undergo ectopic calcification and consequent dysfunction, but little is known about the expression of calcification genes in the healthy cardiovascular system. Large animal models are of increasing importance in cardiovascular disease research as they demonstrate more similar cardiovascular features (in terms of anatomy, physiology and size) to humans than do rodent species. We used RNA sequencing results from the sheep, which has been utilized extensively to examine calcification of prosthetic cardiac valves, to explore the transcriptome of the heart and cardiac valves in this large animal, in particular looking at expression of calcification and extracellular matrix genes. We then examined genes implicated in the process of vascular calcification in a wide array of cardiovascular tissues and across multiple developmental stages, using RT-qPCR. Our results demonstrate that there is a balance between genes that promote and those that suppress mineralization during development and across cardiovascular tissues. We show extensive expression of genes encoding proteins involved in formation and maintenance of the extracellular matrix in cardiovascular tissues, and high expression of hematopoietic genes in the cardiac valves. Our analysis will support future research into the functions of implicated genes in the development of valve calcification, and increase the utility of the sheep as a large animal model for understanding ectopic calcification in cardiovascular disease. This study provides a foundation to explore the transcriptome of the developing cardiovascular system and is a valuable resource for the fields of mammalian genomics and cardiovascular research.

Metformin, resveratrol, and exendin-4 inhibit high phosphate-induced vascular calcification via AMPK-RANKL signaling

Vascular calcification increases the risk of developing cardiovascular disease, and it is closely associated with metabolic disorders such as diabetes mellitus and non-alcoholic fatty liver disease. We investigated whether the activators of AMP-activated protein kinase (AMPK), metformin, resveratrol, and exendin-4, improved inorganic phosphate (Pi)-induced vascular calcification in rat vascular smooth muscle cells (VSMCs) and whether these effects were via AMPK. Pi increased calcium deposition in a dose-dependent manner, and metformin, resveratrol, and exendin-4 significantly decreased calcium deposition in the Pi-treated VSMCs. Moreover, metformin and exendin-4 increased the expression of a SMC marker gene, α-smooth muscle actin, and Ampk and reduced the receptor activator of nuclear factor kappa-Β ligand (Rankl)/osteoprotegerin ratio. Metformin, resveratrol, and exendin-4 reduced the expression of osteoblast differentiation-associated factors, such as runt-related transcription factor 2, bone morphogenic protein-2, p-small mothers against decapentaplegic 1/5/8, and Rankl. Inhibition of AMPK by siRNA adversely affected the anti-calcification effects of metformin, resveratrol, and exendin-4 and reversed the reduction of the expression of Rankl by metformin and exendin-4 in the Pi-treated VSMCs. These data suggest that metformin, resveratrol, and exendin-4 ameliorate Pi-induced vascular calcification by inhibiting osteoblast differentiation of VSMCs, which is mediated by AMPK.

Hdac9 inhibits medial artery calcification through down-regulation of Osterix

BACKGROUNDS

Medial artery calcification (MAC) significantly contributes to the increased cardiovascular death in patients with chronic kidney disease (CKD). Previous genome-wide association studies have shown that various genetic variants of the histone deacetylase Hdac9 are associated with cardiovascular disease, but the role of Hdac9 in MAC under CKD conditions remains unclear.

METHODS

High phosphate-induced vascular smooth muscle cell (VSMC) calcification and MAC in mice administered with vitamin D3 (vD) were used in the present study. Alizarin red staining, calcium quantitative assay, qPCR, western blotting and histology were performed.

RESULTS

Hdac9 expression was significantly down-regulated during high phosphate-induced vascular smooth muscle cell (VSMC) calcification and MAC in mice administered with vitamin D₃ (vD). Furthermore, high phosphate treatment inhibited phosphorylation of Akt, and pharmacological inhibition of Akt signaling reduced Hdac9 expression in cultured VSMCs. Knockdown of Hdac9 significantly enhanced calcium deposition in VSMCs. Conversely, adenovirus mediated-overexpression of Hdac9 inhibited high phosphate induced VSMC in vitro calcification. Our subsequent mechanistic studies revealed that the anti-calcific effect of Hdac9 was mediated through down-regulation of osteoblast-specific transcription factor Osterix.

CONCLUSION

These data suggest that Hdac9 is a novel inhibitor of MAC and may represent a potential therapeutic target for MAC in CKD patients.

In vitro and in vivo investigation of osteogenic properties of self-contained phosphate-releasing injectable purine-crosslinked chitosan-hydroxyapatite constructs

Bone fracture repair is a multifaceted, coordinated physiological process that requires new bone formation and resorption, eventually returning the fractured bone to its original state. Currently, a variety of different approaches are pursued to accelerate the repair of defective bones, which include the use of 'gold standard' autologous bone grafts. However, such grafts may not be readily available, and procedural complications may result in undesired outcomes. Considering the ease of use and tremendous customization potentials, synthetic materials may become a more suitable alternative of bone grafts. In this study, we examined the osteogenic potential of guanosine 5′-diphosphate-crosslinked chitosan scaffolds with the incorporation of hydroxyapatite, with or without pyrophosphatase activity, both in vitro and in vivo. First, scaffolds embedded with cells were characterized for cell morphology, viability, and attachment. The cell-laden scaffolds were found to significantly enhance proliferation for up to threefold, double alkaline phosphatase activity and osterix expression, and increase calcium phosphate deposits in vitro. Next, chitosan scaffolds were implanted at the fracture site in a mouse model of intramedullary rod-fixed tibial fracture. Our results showed increased callus formation at the fracture site with the scaffold carrying both hydroxyapatite and pyrophosphatase in comparison to the control scaffolds lacking both pyrophosphatase and hydroxyapatite, or pyrophosphatase alone. These results indicate that the pyrophosphatase-hydroxyapatite composite scaffold has a promising capacity to facilitate bone fracture healing.

Intimal and medial calcification in relation to cardiovascular risk factors

Purpose

To assess specific risk factors and biomarkers associated with intimal arterial calcification (IAC) and medial arterial calcification (MAC).

Methods

We conducted a cross-sectional study in patients with or at risk of vascular disease from the SMART study(n = 520) and the DCS cohort(n = 198). Non-contrast computed tomography scanning of the lower extremities was performed and calcification in the femoral and crural arteries was scored as absent, predominant IAC, predominant MAC or indistinguishable. Multinomial regression models were used to assess the associations between cardiovascular risk factors and calcification patterns. Biomarkers for inflammation, calcification and vitamin K status were measured in a subset of patients with IAC(n = 151) and MAC(n = 151).

Results

Femoral calcification was found in 77% of the participants, of whom 38% had IAC, 28% had MAC and 11% were scored as indistinguishable. The absolute agreement between the femoral and crural arteries was high(69%). Higher age, male sex, statin use and history of coronary artery disease were associated with higher prevalences of femoral IAC and MAC compared to absence of calcification. Smoking and low ankle-brachial-index (ABI) were associated with higher prevalence of IAC and high ABI was associated with less IAC. Compared to patients with IAC, patients with MAC more often had diabetes, have a high ABI and were less often smokers. Inactive Matrix-Gla Protein was associated with increased MAC prevalence, while osteonectin was associated with decreased risk of MAC, compared to IAC.

Conclusions

When femoral calcification is present, the majority of the patients have IAC or MAC throughout the lower extremity, which have different associated risk factor profiles.

Associations between the serum levels of selected bone turnover markers and biological traits in nursing home women aged 80+ without inflammation. A pilot study

BACKGROUND

Bone turnover markers (BTM) reflect the status of bone remodeling processes responsible for bone mineral density. The existing body of evidence that osseous tissue can interact with many other body tissues and organs suggests that the cross-talks can lead to different relationships. The biological traits associated with BTMs have not been thoroughly studied in the elderly despite bone turnover being known to increase with age.

OBJECTIVE

To determine whether the C-terminal crosslinking telopeptides of type I collagen (CTXI) and the serum levels of total (TAP) and bone-specific (BAP) alkaline phosphatase are associated with the biological traits in nursing home women aged 80-92 years without inflammation and, if so, to indicate the best predictors of these BTM's blood concentrations.

METHODS

A group of 64 female volunteers aged 80 years and older, the residents of nursing homes, were screened for the study. Fifty two women were ineligible as they met the exclusion criteria. As a result, the study group consisted of 12 participants (85.1 ± 3.9 years; 58.1 ± 8.7 kg; 1.52 ± 0.06 m), all having blood C-reactive protein (CRP) levels below 3 mg/l. Also assessed were the participants' morphology, glucose and insulin levels, lipid profiles, CTXI, TAP, and BAP. Other measured parameters included body composition, resting heart rate and arterial blood pressure, isometric knee extension peak torque (IKEPT), and walking capacity (6-min walk test). The statistical analysis was performed using Pearson's correlation coefficients, the Benjamini-Hochberg procedure, and a stepwise multiple regression analysis with backward elimination.

RESULTS

Inverse correlations were found between CTX-I and hemoglobin concentration (HGB) (r = -0.680; p = .015), red blood cells count (RBC) (r = -0.664; p = .019), fat-free mass (r = -0.633; p = .027), body weight (r = -0.589; p = .044), and total cholesterol (r = -0.581; p = .048). The multiple regression analysis of CTX-I showed that body weight was the only independent variable that was statistically significant (r2 = 0.346; p < .05; SEE = 0.347 ng/ml). BAP was positively correlated with double product (DP) (r = 0.742; p = .006), RBC (r = 0.650; p = .022), HGB (r = 0.637; p = .026), mean arterial pressure (MAP) (r = 0.622; p = .031), diastolic blood pressure (DBP) (r = 0.612; p = .034), body height (r = 0.603; p = .038), IKEPT (r = 0.565; p = .056), and systolic blood pressure (SBP) (r = 0.538; p = .071). BAP, a dependent variable, was the most closely correlated with DP (r² = 0.550; p < .01; SEE = 9.161 U/l). TAP was also significantly associated with DP (r = 0.775; p = .003), with the association being stronger than between BAP and DP (r² = 0.600; p < .01; SEE = 1000.5 beats/min*mm Hg).

CONCLUSIONS

In relatively healthy the oldest-old nursing home women without inflammation, total body weight was the best predictor of bone resorption shown by the CTX-I concentration, whereas the rate pressure product (DP) turned out to best predict osteoblastic activity determinable from serum alkaline phosphatase activity. The results of the study suggest that the activity of serum TAP and BAP can be enhanced by different mechanisms.

LncRNA H19/Runx2 axis promotes VSMCs transition via MAPK pathway

Arterial calcification (AC) is mainly caused by osteoblast phenotypic transition of vascular smooth muscle cells (VSMCs). Long noncoding RNA H19 (lncRNA H19) has attracted increasingly attention because of their transcriptional regulation crucial potency. We reported that lncRNA H19 expression is up-regulated after VSMCs transition. Thus, we aim to study the role of H19 and the molecular mechanisms in VSMCs transition. To determine the expression of H19 in calcified VSMCs, we induced VSMCs calcification with 10 mM β-glycerophosphate. By qPCR and Western Blot analysis, we found that the expression of lncRNA H19, Runx2 and OSX were all highly increased in calcified VSMCs compared with normal VSMCs, while the expression of VSMCs differentiation markers, SM22-α and α-SMA, were significantly decreased. SiRNA study showed that knockdown of lncRNA H19 can decrease VSMCs calcification and Runx2 expression. We further validated that lncRNA H19 promoted VSMCs calcification via the p38 MAPK and ERK1/2 signal transduction pathways. As a conclusion, the present study showed that lncRNA H19/Runx2 axis promotes VSMCs transition via MAPK pathway. This finding not only reveal a novel function of lncRNA H19, but also provides a new opinion on the role of lncRNA H19 which participant in the Runx2 regulatory pathway in AC and can be a new indication for the diagnosis and treatment of AC at an early time.

Osteocalcin Regulates Arterial Calcification Via Altered Wnt Signaling and Glucose Metabolism

Arterial calcification is an important hallmark of cardiovascular disease and shares many similarities with skeletal mineralization. The bone-specific protein osteocalcin (OCN) is an established marker of vascular smooth muscle cell (VSMC) osteochondrogenic transdifferentiation and a known regulator of glucose metabolism. However, the role of OCN in controlling arterial calcification is unclear. We hypothesized that OCN regulates calcification in VSMCs and sought to identify the underpinning signaling pathways. Immunohistochemistry revealed OCN co-localization with VSMC calcification in human calcified carotid artery plaques. Additionally, 3 mM phosphate treatment stimulated OCN mRNA expression in cultured VSMCs (1.72-fold, p < 0.001). Phosphate-induced calcification was blunted in VSMCs derived from OCN null mice (Ocn ^-/- ) compared with cells derived from wild-type (WT) mice (0.37-fold, p < 0.001). Ocn ^-/- VSMCs showed reduced mRNA expression of the osteogenic marker Runx2 (0.51-fold, p < 0.01) and the sodium-dependent phosphate transporter, PiT1 (0.70-fold, p < 0.001), with an increase in the calcification inhibitor Mgp (1.42-fold, p < 0.05) compared with WT. Ocn ^-/- VSMCs also showed reduced mRNA expression of Axin2 (0.13-fold, p < 0.001) and Cyclin D (0.71 fold, p < 0.01), markers of Wnt signaling. CHIR99021 (GSK3β inhibitor) treatment increased calcium deposition in WT and Ocn ^-/- VSMCs (1 μM, p < 0.001). Ocn ^-/- VSMCs, however, calcified less than WT cells (1 μM; 0.27-fold, p < 0.001). Ocn ^-/- VSMCs showed reduced mRNA expression of Glut1 (0.78-fold, p < 0.001), Hex1 (0.77-fold, p < 0.01), and Pdk4 (0.47-fold, p < 0.001). This was accompanied by reduced glucose uptake (0.38-fold, p < 0.05). Subsequent mitochondrial function assessment revealed increased ATP-linked respiration (1.29-fold, p < 0.05), spare respiratory capacity (1.59-fold, p < 0.01), and maximal respiration (1.52-fold, p < 0.001) in Ocn ^-/- versus WT VSMCs. Together these data suggest that OCN plays a crucial role in arterial calcification mediated by Wnt/β-catenin signaling through reduced maximal respiration. Mitochondrial dynamics may therefore represent a novel therapeutic target for clinical intervention. © 2019 American Society for Bone and Mineral Research.

Clinical Value of Cardiovascular Calcifications on Non-Enhanced, Non-ECG-Gated Chest CT

심혈관계 석회화는 다양한 심혈관계 질환에서 나타나며 심혈관 사건 발생의 표지자의 역할을 한다. CT의 기술이 발전함에 따라 심전도동기 CT뿐만이 아닌 비 심전도동기 CT에서도 심혈관계 석회화를 평가하는 것이 가능해졌다. 이번 종설에서는 비 조영증강 비 심전도동기 흉부 CT에서 발견되는 심혈관계 석회화를 심혈관 사건 발생과 연관되었다고 알려진 3가지 석회화(관상동맥, 흉부 대동맥, 판막 석회화)에 대해 자세히 살펴보고 추가적으로 우연적으로 발견될 수 있는 심막 석회화에 대해서도 간단히 기술하였다. 우리나라에서 2019년 하반기부터 폐암 검진이 시작되면서 고령 흡연자의 비 조영증강 비 심전도동기 저선량 CT의 영상의 수가 늘어나고 있고 이에 우연히 발견되는 심혈관계 석회화도 늘어나고 있다. 그러므로 비 조영증강 비 심전도동기 흉부 CT에서 발견되는 심혈관계 석회화의 의미를 이해하고 적절히 보고하는 것이 영상의학과 의사에게 중요할 것이다.

Ossified blood vessels in primary familial brain calcification elicit a neurotoxic astrocyte response

Brain calcifications are commonly detected in aged individuals and accompany numerous brain diseases, but their functional importance is not understood. In cases of primary familial brain calcification, an autosomally inherited neuropsychiatric disorder, the presence of bilateral brain calcifications in the absence of secondary causes of brain calcification is a diagnostic criterion. To date, mutations in five genes including solute carrier 20 member 2 (SLC20A2), xenotropic and polytropic retrovirus receptor 1 (XPR1), myogenesis regulating glycosidase (MYORG), platelet-derived growth factor B (PDGFB) and platelet-derived growth factor receptor β (PDGFRB), are considered causal. Previously, we have reported that mutations in PDGFB in humans are associated with primary familial brain calcification, and mice hypomorphic for PDGFB (Pdgfb^ret/ret) present with brain vessel calcifications in the deep regions of the brain that increase with age, mimicking the pathology observed in human mutation carriers. In this study, we characterize the cellular environment surrounding calcifications in Pdgfb^ret/ret animals and show that cells around vessel-associated calcifications express markers for osteoblasts, osteoclasts and osteocytes, and that bone matrix proteins are present in vessel-associated calcifications. Additionally, we also demonstrate the osteogenic environment around brain calcifications in genetically confirmed primary familial brain calcification cases. We show that calcifications cause oxidative stress in astrocytes and evoke expression of neurotoxic astrocyte markers. Similar to previously reported human primary familial brain calcification cases, we describe high interindividual variation in calcification load in Pdgfb^ret/ret animals, as assessed by ex vivo and in vivo quantification of calcifications. We also report that serum of Pdgfb^ret/ret animals does not differ in calcification propensity from control animals and that vessel calcification occurs only in the brains of Pdgfb^ret/ret animals. Notably, ossification of vessels and astrocytic neurotoxic response is associated with specific behavioural and cognitive alterations, some of which are associated with primary familial brain calcification in a subset of patients.

Relation of Thoracic Aortic and Coronary Artery Calcium to Cardiovascular Risk Factors (from The Brazilian Longitudinal Study of Adult Health [ELSA-Brazil])

Thoracic aortic calcium (TAC) and coronary artery calcium (CAC) are associated with an increased risk of cardiovascular disease (CVD) and death. However, risk factors associated with arterial calcium may vary across vascular beds. We verified whether TAC is associated with the same risk factors as is CAC in adults without established CVD. Cross-sectional analysis including 2,433 participants (aged 38 to 78 years) of ELSA-Brasil cohort in Minas Gerais, Brazil. Nonenhanced ECG-gated multislice computed tomography were performed to detect calcium in the thoracic aorta and the coronaries (2015 to 2016). Multivariate logistic regression evaluated the associations of both TAC and CAC with CVD risk factors (smoking, body mass index, physical activity, alcohol intake, family history of CVD, low-density lipoprotein- and high-density lipoprotein-cholesterol, HbA1c, blood pressure, antidiabetic, antihypertensive, and lipid lowering medications). Overall prevalence of TAC and CAC were 69% and 43%, respectively. CAC prevalence was lower among women (31%) than men (56%) (Adjusted odds ratio [OR] 0.30; 0.24 to 0.38). After adjustments, black individuals were less likely to have any CAC as compared with whites (OR 0.63; 0.47 to 0.86). Neither sex, nor race/skin color were statistically associated with TAC. Use of antidiabetic medications remained associated with CAC (OR 1.80; 1.23 to 2.631.01), but not with TAC. All other risk factors, except education, alcohol, physical activity and HbA1c, persisted statistically associated with both TAC and CAC in the final analysis, with small differences in the magnitudes of the ORs. In conclusion, the only disagreements seen in the risk factors associated with CAC and TAC were sex, race/skin color, and use of antidiabetic medications.

Autophagy as a novel therapeutic target in vascular calcification

The autophagy pathway is a key regulator of cellular metabolism and homeostasis, and plays a critical role in maintaining normal vascular cell function. It is well recognised that autophagy can regulate endothelial cell homeostasis, vascular smooth muscle cell (VSMC) phenotype transition, and calcium (Ca²⁺) homeostasis in VSMCs. Emerging evidence has demonstrated that autophagy directly protects against vascular calcification (VC). Crosstalk between endosomes, dysfunctional mitochondria, autophagic vesicles and Ca²⁺ and phosphate (Pi) enriched matrix vesicles (MVs) may underpin the pathogenesis of VC. In this review, we summarize the current experimental evidence in understanding how autophagy maintains normal vascular cell function and its protective role against vascular calcification. We also discuss the underlying molecular and cellular mechanisms through which autophagy inhibits vascular calcification. Pharmacological modulation of autophagy may offer an exciting new strategy for the treatment of vascular calcification.

Strong Signs for a Weak Wall in Tricuspid Aortic Valve Associated Aneurysms and a Role for Osteopontin in Bicuspid Aortic Valve Associated Aneurysms

Central processes in the pathogenesis of TAV- (tricuspid aortic valve) and BAV- (bicuspid aortic valve) associated ascending thoracic aortic aneurysm (ATAA) development are still unknown. To gain new insights, we have collected aortic tissue and isolated smooth muscle cells of aneurysmal tissue and subjected them to in situ and in vitro analyses. We analyzed aortic tissue from 78 patients (31 controls, 28 TAV-ATAAs, and 19 BAV-ATAAs) and established 30 primary smooth muscle cell cultures. Analyses included histochemistry, immuno-, auto-fluorescence-based image analyses, and cellular analyses including smooth muscle cell contraction studies. With regard to TAV associated aneurysms, we observed a strong impairment of the vascular wall, which appears on different levels—structure and dimension of the layers (reduced media thickness, increased intima thickness, atherosclerotic changes, degeneration of aortic media, decrease of collagen, and increase of elastic fiber free area) as well as on the cellular level (accumulation of fibroblasts/myofibroblasts, and increase in the number of smooth muscle cells with a reduced alpha smooth muscle actin (α-SM actin) content per cell). The pathological changes in the aortic wall of BAV patients were much less pronounced—apart from an increased expression of osteopontin (OPN) in the vascular wall which stem from smooth muscle cells, we observed a trend towards increased calcification of the aortic wall (increase significantly associated with age). These observations provide strong evidence for different pathological processes and different disease mechanisms to occur in BAV- and TAV-associated aneurysms.

Different histological types of active intraplaque calcification underlie alternative miRNA-mRNA axes in carotid atherosclerotic disease

Arterial calcification is an actively regulated process, with different morphological manifestations. Micro-RNAs emerged as potential regulators of vascular calcification; they may become novel diagnostic tools and be used for a finest staging of the carotid plaque progression. The present study aimed at characterizing the different miRNA-mRNA axes in carotid plaques according to their histological patterns of calcification. Histopathological analysis was performed on 124 retrospective carotid plaques, with clinical data and preoperatory angio-CT. miRNA analysis was carried out with microfluidic cards. Real-time PCR was performed for selected miRNAs validation and for RUNX-2 and SOX-9 mRNA levels. CD31, CD68, SMA, and SOX-9 were analyzed by immunohistochemistry. miRNA levels on HUVEC cells were analyzed for confirming results under in vitro osteogenic conditions. Histopathological analysis revealed two main calcification subtypes of plaques: calcific cores (CC) and protruding nodules (PN). miRNA array and PCR validation of miR-1275, miR-30a-5p, and miR-30d indicated a significant upregulation of miR-30a-5p and miR-30d in the PN plaques. Likewise, the miRNA targets RUNX-2 and SOX-9 resulted poorly expressed in PN plaques. The inverse correlation between miRNA and RUNX-2 levels was confirmed on osteogenic-differentiated HUVEC. miR-30a-5p and miR-30d directly correlated with calcification extension and thickness at angio-CT imaging. Our study demonstrated the presence of two distinct morphological subtypes of calcification in carotid atheromatous plaques, supported by different miRNA signatures, and by different angio-CT features. These results shed the light on the use of miRNA as novel diagnostic markers, suggestive of plaque evolution.

Hydrogen Sulfide Prevents Elastin Loss and Attenuates Calcification Induced by High Glucose in Smooth Muscle Cells through Suppression of Stat3/Cathepsin S Signaling Pathway

Vascular calcification can be enhanced by hyperglycemia. Elastin loss in tunica media promotes the osteogenic transformation of smooth muscle cells (SMCs) and involves arterial medial calcification (AMC) that is associated with a high incidence of cardiovascular risk in patients with type 2 diabetes. Here, we tested whether hydrogen sulfide (H₂S), an endogenous gaseous mediator, can prevent elastin loss and attenuate calcification induced by high glucose in SMCs. Calcification was induced by high glucose (4500 mg/L) in human aortic SMCs (HASMCs) under the condition of calcifying medium containing 10 mM β-glycerophosphate (β-GP). The experiments showed that NaHS (an H₂S donor, 100 μM) mitigated the calcification of HASMCs treated with high glucose by decreasing calcium and phosphorus levels, calcium deposition and ALP activity and inhibited osteogenic transformation by increasing SMα-actin and SM22α, two phenotypic markers of smooth muscle cells, and decreasing core binding factor α-1 (Cbfα-1), a key factor in bone formation, protein expressions in HASMCs. Moreover, NaHS administration inhibited the activation of Stat3, cathepsin S (CAS) activity and its expression, but increased the level of elastin protein. Pharmacological inhibition or gene silencing Stat3 not only reversed elastin loss, but also attenuated CAS expression. Inhibition of CAS alleviated, while CAS overexpression exacerbated, elastin loss. Interestingly, overexpression of wild type (WT)-Stat3, but not its mutant C259S, elevated CAS protein expression and reduced elastin level. Moreover, NaHS induced S-sulfhydration in WT, but not in the C259S Stat3. These data suggest that H₂S may directly regulate Cys259 residue in Stat3 and then impair its signaling function. Our data indicate that H₂S may attenuate vascular calcification by upregulating elastin level through the inhibition of Stat3/CAS signaling.

Aortic Arch Calcification Is a Strong Predictor of the Severity of Coronary Artery Disease in Patients with Acute Coronary Syndrome

BACKGROUND

The purpose of this study was to investigate the correlation of the extent of aortic arch calcification (AAC) detectable on chest X-rays with the severity of coronary artery disease (CAD) as evaluated by the SYNTAX score (SS) in patients with acute coronary syndrome (ACS).

METHODS

A total of 1,418 patients (344 women; 59 ± 10 years) who underwent coronary angiography for ACS and were treated with coronary revascularization were included in the present study; chest X-rays were performed on admission. The AAC extent was divided into four grades (0-3). SS was calculated based on each patient's coronary angiographic findings. The relationship between the AAC extent and SS was assessed.

RESULTS

The AAC extent was positively correlated with SS (ρ = 0.639, P < 0.001). In the multivariate analysis, compared with grade 0, odds ratios (ORs) of AAC grades 1, 2, and 3 in predicting SS >22 were 12.95 (95% CI, 7.85-21.36), 191.76 (95% CI, 103.17-356.43), and 527.81 (95% CI, 198.24-1405.28), respectively. Receiver operating characteristic curve analysis yielded a strong predictive ability of the AAC extent for SS >22 (area under curve = 0.840, P < 0.001). Absence of AAC had a sensitivity, specificity, positive prognostic value, negative prognostic value, and accuracy of 46.7%, 95.9%, 94.1%, 56.4%, and 67.3%, respectively, for SS ≤22. AAC grades ≥2 had a sensitivity of 66.3%, specificity of 89.2%, positive prognostic value of 81.5%, negative prognostic value of 78.6%, and accuracy of 79.6% for the correct identification of SS >22.

CONCLUSIONS

The extent of AAC detectable on chest X-rays might provide valuable information in predicting CAD severity in ACS patients.

Inhibition of vascular smooth muscle cell calcification by ATP analogues

Arterial medial calcification (AMC) has been associated with phenotypic changes in vascular smooth muscle cells (VSMCs) that reportedly makes them more osteoblast-like. Previous work has shown that ATP/UTP can inhibit AMC directly via P2 receptors and indirectly by NPP1-mediated hydrolysis to produce the mineralisation inhibitor, pyrophosphate (PP_i). This study investigated the role of P2X receptors in the inhibitory effects of extracellular nucleotides on VSMC calcification. We found that Bz-ATP, α,β-meATP and β,γ-meATP inhibited calcification by up to 100%. Culture in a high-phosphate medium (2 mM) was associated with increased VSMC death and apoptosis; treatment with Bz-ATP, α,β-meATP and β,γ-meATP reduced apoptosis to levels seen in non-calcifying cells. Calcification was also associated with alterations in the protein levels of VSMC (e.g. SM22α and SMA) and osteoblast-associated (e.g. Runx2 and osteopontin) markers; Bz-ATP, α,β-meATP and β,γ-meATP attenuated these changes in protein expression. Long-term culture with Bz-ATP, α,β-meATP and β,γ-meATP resulted in lower extracellular ATP levels and an increased rate of ATP breakdown. P2X receptor antagonists failed to prevent the inhibitory effects of these analogues suggesting that they act via P2X receptor-independent mechanisms. In agreement, the breakdown products of α,β-meATP and β,γ-meATP (α,β-meADP and methylene diphosphonate, respectively) also dose-dependently inhibited VSMC calcification. Furthermore, the actions of Bz-ATP, α,β-meATP and β,γ-meATP were unchanged in VSMCs isolated from NPP1-knockout mice, suggesting that the functional effects of these compounds do not involve NPP1-mediated generation of PP_i. Together, these results indicate that the inhibitory effects of ATP analogues on VSMC calcification and apoptosis in vitro may be mediated, at least in part, by mechanisms that are independent of purinergic signalling and PP_i.

Elastolytic activity of cysteine cathepsins K, S, and V promotes vascular calcification

Elastin plays an important role in maintaining blood vessel integrity. Proteolytic degradation of elastin in the vascular system promotes the development of atherosclerosis, including blood vessel calcification. Cysteine cathepsins have been implicated in this process, however, their role in disease progression and associated complications remains unclear. Here, we showed that the degradation of vascular elastin by cathepsins (Cat) K, S, and V directly stimulates the mineralization of elastin and that mineralized insoluble elastin fibers were ~25–30% more resistant to CatK, S, and V degradation when compared to native elastin. Energy dispersive X-ray spectroscopy investigations showed that insoluble elastin predigested by CatK, S, or V displayed an elemental percentage in calcium and phosphate up to 8-fold higher when compared to non-digested elastin. Cathepsin-generated elastin peptides increased the calcification of MOVAS-1 cells acting through the ERK1/2 pathway by 34–36%. We made similar observations when cathepsin-generated elastin peptides were added to ex vivo mouse aorta rings. Altogether, our data suggest that CatK-, S-, and V-mediated elastolysis directly accelerates the mineralization of the vascular matrix by the generation of nucleation points in the elastin matrix and indirectly by elastin-derived peptides stimulating the calcification by vascular smooth muscle cells. Both processes inversely protect against further extracellular matrix degradation.

Ferritin in Kidney and Vascular Related Diseases: Novel Roles for an Old Player

Iron is at the forefront of a number of pivotal biological processes due to its ability to readily accept and donate electrons. However, this property may also catalyze the generation of free radicals with ensuing cellular and tissue toxicity. Accordingly, throughout evolution numerous pathways and proteins have evolved to minimize the potential hazardous effects of iron cations and yet allow for readily available iron cations in a wide variety of fundamental metabolic processes. One of the extensively studied proteins in the context of systemic and cellular iron metabolisms is ferritin. While clinicians utilize serum ferritin to monitor body iron stores and inflammation, it is important to note that the vast majority of ferritin is located intracellularly. Intracellular ferritin is made of two different subunits (heavy and light chain) and plays an imperative role as a safe iron depot. In the past couple of decades our understanding of ferritin biology has remarkably improved. Additionally, a significant body of evidence has emerged describing the significance of the kidney in iron trafficking and homeostasis. Here, we briefly discuss some of the most important findings that relate to the role of iron and ferritin heavy chain in the context of kidney-related diseases and, in particular, vascular calcification, which is a frequent complication of chronic kidney disease.

Differing calcification processes in cultured vascular smooth muscle cells and osteoblasts

Arterial medial calcification (AMC) is the deposition of calcium phosphate mineral, often as hydroxyapatite, in the medial layer of the arteries. AMC shares some similarities to skeletal mineralisation and has been associated with the transdifferentiation of vascular smooth muscle cells (VSMCs) towards an osteoblast-like phenotype. This study used primary mouse VSMCs and calvarial osteoblasts to directly compare the established and widely used in vitro models of AMC and bone formation. Significant differences were identified between osteoblasts and calcifying VSMCs. First, osteoblasts formed large mineralised bone nodules that were associated with widespread deposition of an extracellular collagenous matrix. In contrast, VSMCs formed small discrete regions of calcification that were not associated with collagen deposition and did not resemble bone. Second, calcifying VSMCs displayed a progressive reduction in cell viability over time (≤7-fold), with a 50% increase in apoptosis, whereas osteoblast and control VSMCs viability remained unchanged. Third, osteoblasts expressed high levels of alkaline phosphatase (TNAP) activity and TNAP inhibition reduced bone formation by to 90%. TNAP activity in calcifying VSMCs was ∼100-fold lower than that of bone-forming osteoblasts and cultures treated with β-glycerophosphate, a TNAP substrate, did not calcify. Furthermore, TNAP inhibition had no effect on VSMC calcification. Although, VSMC calcification was associated with increased mRNA expression of osteoblast-related genes (e.g. Runx2, osterix, osteocalcin, osteopontin), the relative expression of these genes was up to 40-fold lower in calcifying VSMCs versus bone-forming osteoblasts. In summary, calcifying VSMCs in vitro display some limited osteoblast-like characteristics but also differ in several key respects: 1) their inability to form collagen-containing bone; 2) their lack of reliance on TNAP to promote mineral deposition; and, 3) the deleterious effect of calcification on their viability.