An In Vitro Murine Model of Vascular Smooth Muscle Cell Mineralization

A Dynamic Cellular Model as an Emerging Platform to Reproduce the Complexity of Human Vascular Calcification In Vitro

Vascular calcification (VC) is a cardiovascular disease characterized by calcium salt deposition in vascular smooth muscle cells (VSMCs). Standard in vitro models used in VC investigations are based on VSMC monocultures under static conditions. Although these platforms are easy to use, the absence of interactions between different cell types and dynamic conditions makes these models insufficient to study key aspects of vascular pathophysiology. The present study aimed to develop a dynamic endothelial cell-VSMC co-culture that better mimics the in vivo vascular microenvironment. A double-flow bioreactor supported cellular interactions and reproduced the blood flow dynamic. VSMC calcification was stimulated with a DMEM high glucose calcification medium supplemented with 1.9 mM NaH2PO4/Na2HPO4 (1:1) for 7 days. Calcification, cell viability, inflammatory mediators, and molecular markers (SIRT-1, TGFβ1) related to VSMC differentiation were evaluated. Our dynamic model was able to reproduce VSMC calcification and inflammation and evidenced differences in the modulation of effectors involved in the VSMC calcified phenotype compared with standard monocultures, highlighting the importance of the microenvironment in controlling cell behavior. Hence, our platform represents an advanced system to investigate the pathophysiologic mechanisms underlying VC, providing information not available with the standard cell monoculture.

Pharmacological modulation of vascular ageing: A review from VascAgeNet

Vascular ageing, characterized by structural and functional changes in blood vessels of which arterial stiffness and endothelial dysfunction are key components, is associated with increased risk of cardiovascular and other age-related diseases. As the global population continues to age, understanding the underlying mechanisms and developing effective therapeutic interventions to mitigate vascular ageing becomes crucial for improving cardiovascular health outcomes. Therefore, this review provides an overview of the current knowledge on pharmacological modulation of vascular ageing, highlighting key strategies and promising therapeutic targets. Several molecular pathways have been identified as central players in vascular ageing, including oxidative stress and inflammation, the renin-angiotensin-aldosterone system, cellular senescence, macroautophagy, extracellular matrix remodelling, calcification, and gasotransmitter-related signalling. Pharmacological and dietary interventions targeting these pathways have shown potential in ameliorating age-related vascular changes. Nevertheless, the development and application of drugs targeting vascular ageing is complicated by various inherent challenges and limitations, such as certain preclinical methodological considerations, interactions with exercise training and sex/gender-related differences, which should be taken into account. Overall, pharmacological modulation of endothelial dysfunction and arterial stiffness as hallmarks of vascular ageing, holds great promise for improving cardiovascular health in the ageing population. Nonetheless, further research is needed to fully elucidate the underlying mechanisms and optimize the efficacy and safety of these interventions for clinical translation.

Calciprotein Particle Synthesis Strategy Determines In Vitro Calcification Potential

Circulating calciprotein particles (CPP), colloids of calcium, phosphate and proteins, were identified as potential drivers of the calcification process in chronic kidney disease. The present study compared CPP produced using different protocols with respect to particle morphology, composition, particle number and in vitro calcification potency. CPP were synthesized with 4.4 mM (CPP-A and B) or 6 mM (CPP-C and D) phosphate and 2.8 mM (CPP-A and B) or 10 mM (CPP-C and D) calcium, with either bovine fetuin-A (CPP-C) or fetal bovine serum (CPP-A, B and D) as a source of protein, and incubated for 7 (CPP-A2) or 14 days (CPP-B2), 12 h (CPP-C2, D2 and B1) or 30 min (CPP-D1). Particle number was determined with nanoparticle tracking and calcium content was measured in CPP preparations and to determine human vascular smooth muscle cell (hVSMC) calcification. Morphologically, CPP-C2 were the largest. Particle number did not correspond to the calcium content of CPP. Both methods of quantification resulted in variable potencies of CPP2 to calcify VSMC, with CPP-B2 as most stable inducer of hVSMC calcification. In contrast, CPP-B1 and D1 were unable to induce calcification of hVSMC, and endogenous CPP derived from pooled serum of dialysis patients were only able to calcify hVSMC to a small extent compared to CPP2.CPP synthesized using different protocols appear morphologically similar, but in vitro calcification potency is dependent on composition and how the CPP are quantified. Synthetic CPP are not comparable to endogenous CPP in terms of the calcification propensity.

Characterization of murine cytomegalovirus infection and induction of calcification in Murine Aortic Vascular Smooth Muscle Cells (MOVAS)

Human cytomegalovirus (HCMV) is a widespread pathogen that causes lifelong latent infection in the majority of the world population. HCMV is associated with increased incidence and severity of many cardiovascular diseases including myocarditis, atherosclerosis, and transplant vasculopathy. Due to the species-restricted nature of cytomegalovirus infection, murine cytomegalovirus (MCMV) is a useful model that recapitulates many of the features of HCMV infection of the cardiovascular system. While in vivo MCMV studies are able to answer many questions regarding pathogenesis of infection, in vitro experiments using cell lines are useful tools to further understand the potential underlying mechanisms. In this study, we characterize MCMV infection of the murine aortic smooth muscle cell line (MOVAS). Our findings demonstrate that MOVAS cells are permissive for MCMV infection, form plaques under carboxymethyl cellulose overlay, and produce progeny virus similar to NIH 3T3 murine embryonic fibroblasts. In addition, MCMV infection induces calcification in MOVAS cells similar to that seen in the epicardium of MCMV-infected hearts. We conclude that MOVAS cells are a useful in vitro tool for studying CMV-mediated cardiac calcification.

Tannic acid attenuates vascular calcification-induced proximal tubular cells damage through paracrine signaling

Vascular calcification is common in chronic kidney disease; however, the extent to which such condition can affect the renal microvasculature and the neighboring cell types is unclear. Our induced-calcification model in renal proximal tubular (PT) cells exhibited endoplasmic reticulum (ER) stress and oxidative damage, leading to apoptosis. Here, we utilized such calcification in mouse vascular smooth muscle (MOVAS-1) cells as a vascular calcification model, because it exhibited reactive oxygen species (ROS) generation, ER and oxidative stress, inflammatory, and apoptotic gene expressions. To demonstrate whether the vascular calcification condition can dictate the function of the adjacent PT cell layer, we utilized a Transwell multilayer culture system by combining those MOVAS-1 cells in the bottom chamber and polarized PT cells in the upper chamber to show the dimensional cross-signaling effect. Interestingly, calcification of MOVAS-1 cells, in this co-culture, induced H2O2 and lactate dehydrogenase (LDH) release leading to store-operated Ca2+ entry, ROS generation, and activation of oxidative, inflammatory, and apoptotic gene expressions in PT cells through paracrine signaling. Interestingly, application of tannic acid (TA) to either calcified MOVAS-1 or uncalcified PT cells diminished such detrimental pathway activation. Furthermore, the TA-mediated protection was much higher in the PT cells when applied on the calcified MOVAS-1 cells, and the delayed the pathological effects in neighboring PT cells can well be via paracrine signaling. Together, these results provide evidence of vascular calcification-induced PT cell damage, and the protective role of TA in preventing such pathological consequences, which can potentially be used as a nephroprotective remedy.

A GTPase-activating protein-binding protein (G3BP1)/antiviral protein relay conveys arteriosclerotic Wnt signals in aortic smooth muscle cells

In aortic vascular smooth muscle (VSM), the canonical Wnt receptor LRP6 inhibits protein arginine (Arg) methylation, a new component of noncanonical Wnt signaling that stimulates nuclear factor of activated T cells (viz NFATc4). To better understand how methylation mediates these actions, MS was performed on VSM cell extracts from control and LRP6-deficient mice. LRP6-dependent Arg methylation was regulated on >500 proteins; only 21 exhibited increased monomethylation (MMA) with concomitant reductions in dimethylation. G3BP1, a known regulator of arteriosclerosis, exhibited a >30-fold increase in MMA in its C-terminal domain. Co-transfection studies confirm that G3BP1 (G3BP is Ras-GAP SH3 domain-binding protein) methylation is inhibited by LRP6 and that G3BP1 stimulates NFATc4 transcription. NFATc4 association with VSM osteopontin (OPN) and alkaline phosphatase (TNAP) chromatin was increased with LRP6 deficiency and reduced with G3BP1 deficiency. G3BP1 activation of NFATc4 mapped to G3BP1 domains supporting interactions with RIG-I (retinoic acid inducible gene I), a stimulus for mitochondrial antiviral signaling (MAVS) that drives cardiovascular calcification in humans when mutated in Singleton-Merten syndrome (SGMRT2). Gain-of-function SGMRT2/RIG-I mutants increased G3BP1 methylation and synergized with osteogenic transcription factors (Runx2 and NFATc4). A chemical antagonist of G3BP, C108 (C108 is 2-hydroxybenzoic acid, 2-[1-(2-hydroxyphenyl)ethylidene]hydrazide CAS 15533-09-2), down-regulated RIG-I-stimulated G3BP1 methylation, Wnt/NFAT signaling, VSM TNAP activity, and calcification. G3BP1 deficiency reduced RIG-I protein levels and VSM osteogenic programs. Like G3BP1 and RIG-I deficiency, MAVS deficiency reduced VSM osteogenic signals, including TNAP activity and Wnt5-dependent nuclear NFATc4 levels. Aortic calcium accumulation is decreased in MAVS-deficient LDLR^-/- mice fed arteriosclerotic diets. The G3BP1/RIG-I/MAVS relay is a component of Wnt signaling. Targeting this relay may help mitigate arteriosclerosis.

Exploiting novel valve interstitial cell lines to study calcific aortic valve disease

Calcific aortic valve disease (CAVD) involves progressive valve leaflet thickening and severe calcification, impairing leaflet motion. The in vitro calcification of primary rat, human, porcine and bovine aortic valve interstitial cells (VICs) is commonly employed to investigate CAVD mechanisms. However, to date, no published studies have utilised cell lines to investigate this process. The present study has therefore generated and evaluated the calcification potential of immortalized cell lines derived from sheep and rat VICs. Immortalised sheep (SAVIC) and rat (RAVIC) cell lines were produced by transduction with a recombinant lentivirus encoding the Simian virus (SV40) large and small T antigens (sheep), or large T antigen only (rat), which expressed markers of VICs (vimentin and α‑smooth muscle actin). Calcification was induced in the presence of calcium (Ca; 2.7 mM) in SAVICs (1.9 fold; P<0.001) and RAVICs (4.6 fold; P<0.01). Furthermore, a synergistic effect of calcium and phosphate was observed (2.7 mM Ca/2.0 mM Pi) on VIC calcification in the two cell lines (P<0.001). Analysis of SAVICs revealed significant increases in the mRNA expression of two key genes associated with vascular calcification in cells cultured under calcifying conditions, runt related transcription factor‑2 (RUNX2;1.3 fold; P<0.05 in 4.5 mM Ca) and sodium‑dependent phosphate transporter‑1 (PiT1; 1.2 fold; P<0.05 in 5.4 mM Ca). A concomitant decrease in the expression of the calcification inhibitor matrix Gla protein (MGP) was noted at 3.6 mM Ca (1.3 fold; P<0.01). Assessment of RAVICs revealed alterations in Runx2, Pit1 and Mgp mRNA expression levels (P<0.01). Furthermore, a significant reduction in calcification was observed in SAVICs following treatment with established calcification inhibitors, pyrophosphate (1.8 fold; P<0.01) and etidronate (3.2 fold; P<0.01). Overall, the present study demonstrated that the use of immortalised sheep and rat VIC cell lines is a convenient and cost effective system to investigate CAVD in vitro, and will make a useful contribution to increasing current understanding of the pathophysiological process.

Oligogalacturonic Acid Inhibits Vascular Calcification by Two Mechanisms: Inhibition of Vascular Smooth Muscle Cell Osteogenic Conversion and Interaction With Collagen

OBJECTIVE

Cardiovascular diseases constitute the leading cause of mortality worldwide. Calcification of the vessel wall is associated with cardiovascular morbidity and mortality in patients having many diseases, including diabetes mellitus, atherosclerosis, and chronic kidney disease. Vascular calcification is actively regulated by inductive and inhibitory mechanisms (including vascular smooth muscle cell adaptation) and results from an active osteogenic process. During the calcification process, extracellular vesicles (also known as matrix vesicles) released by vascular smooth muscle cells interact with type I collagen and then act as nucleating foci for calcium crystallization. Our primary objective was to identify new, natural molecules that inhibit the vascular calcification process.

APPROACH AND RESULTS

We have found that oligogalacturonic acids (obtained by the acid hydrolysis of polygalacturonic acid) reduce in vitro inorganic phosphate-induced calcification of vascular smooth muscle cells by 80% and inorganic phosphate-induced calcification of isolated rat aortic rings by 50%. A specific oligogalacturonic acid with a degree of polymerization of 8 (DP8) was found to inhibit the expression of osteogenic markers and, thus, prevent the conversion of vascular smooth muscle cells into osteoblast-like cells. We also evidenced in biochemical and immunofluorescence assays a direct interaction between matrix vesicles and type I collagen via the GFOGER sequence (where single letter amino acid nomenclature is used, O=hydroxyproline) thought to be involved in interactions with several pairs of integrins.

CONCLUSIONS

DP8 inhibits vascular calcification development mainly by inhibition of osteogenic marker expression but also partly by masking the GFOGER sequence-thereby, preventing matrix vesicles from binding to type I collagen.