Phenotypic Modulation of Cultured Primary Human Aortic Vascular Smooth Muscle Cells by Uremic Serum

Circulating Extracellular Vesicle-Propagated microRNA Signature as a Vascular Calcification Factor in Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) accelerates vascular calcification via phenotypic switching of vascular smooth muscle cells (VSMCs). We investigated the roles of circulating small extracellular vesicles (sEVs) between the kidneys and VSMCs and uncovered relevant sEV-propagated microRNAs (miRNAs) and their biological signaling pathways.

METHODS AND RESULTS

We established CKD models in rats and mice by adenine-induced tubulointerstitial fibrosis. Cultures of A10 embryonic rat VSMCs showed increased calcification and transcription of osterix (Sp7), osteocalcin (Bglap), and osteopontin (Spp1) when treated with rat CKD serum. sEVs, but not sEV-depleted serum, accelerated calcification in VSMCs. Intraperitoneal administration of a neutral sphingomyelinase and biogenesis/release inhibitor of sEVs, GW4869 (2.5 mg/kg per 2 days), inhibited thoracic aortic calcification in CKD mice under a high-phosphorus diet. GW4869 induced a nearly full recovery of calcification and transcription of osteogenic marker genes. In CKD, the miRNA transcriptome of sEVs revealed a depletion of 4 miRNAs, miR-16-5p, miR-17~92 cluster-originated miR-17-5p/miR-20a-5p, and miR-106b-5p. Their expression decreased in sEVs from CKD patients as kidney function deteriorated. Transfection of VSMCs with each miRNA-mimic mitigated calcification. In silico analyses revealed VEGFA (vascular endothelial growth factor A) as a convergent target of these miRNAs. We found a 16-fold increase in VEGFA transcription in the thoracic aorta of CKD mice under a high-phosphorus diet, which GW4869 reversed. Inhibition of VEGFA-VEGFR2 signaling with sorafenib, fruquintinib, sunitinib, or VEGFR2-targeted siRNA mitigated calcification in VSMCs. Orally administered fruquintinib (2.5 mg/kg per day) for 4 weeks suppressed the transcription of osteogenic marker genes in the mouse aorta. The area under the curve of miR-16-5p, miR-17-5p, 20a-5p, and miR-106b-5p for the prediction of abdominal aortic calcification was 0.7630, 0.7704, 0.7407, and 0.7704, respectively.

CONCLUSIONS

The miRNA transcriptomic signature of circulating sEVs uncovered their pathologic role, devoid of the calcification-protective miRNAs that target VEGFA signaling in CKD-driven vascular calcification. These sEV-propagated miRNAs are potential biomarkers and therapeutic targets for vascular calcification.

GDF11 Is a Novel Protective Factor Against Vascular Calcification

ABSTRACT

Vascular calcification (VC) occurs via an active cell-mediated process, which involves osteogenic differentiation, apoptosis, and phenotypic transformation of vascular smooth muscle cells (VSMCs). As a member of the transforming growth factor-β family, growth differentiation factor 11 (GDF11) can inhibit apoptosis and osteogenic differentiation and maintain the stability of atherosclerotic plaques. In this study, coronary artery calcium score (CACS) of participants with GDF11 measurements was measured using computed tomography angiography and was scored according to the Agatston score. β-glycerophosphate (10 mM), dexamethasone (100 nM), and l -ascorbic acid (50 µg/mL) [osteogenic medium (OM)] were used to induce calcification of human aortic smooth muscle cells. We found that CACS was negatively correlated with serum GDF11 levels in patients and GDF11 was a strong predictor of elevated CACS (OR = 0.967, 95% CI: 0.945-0.991; P = 0.006), followed by age (OR = 1.151, 95% CI: 1.029-1.286; P = 0.014), triglycerides (OR = 4.743, 95% CI: 1.170-19.236; P = 0.029), C-reactive protein (OR = 1.230, 95% CI: 1.010-1.498; P = 0.04), and hypertension (OR = 7.264, 95% CI: 1.099-48.002; P = 0.04). Furthermore, exogenous GDF11 inhibited OM-induced calcification by inhibiting osteogenic differentiation, the phenotypic transformation and apoptosis of human aortic smooth muscle cells. Our study demonstrates that GDF11 plays a crucial role in reducing vascular calcification and serves as a potential intervention target to vascular calcification.

Effects of Chronic Kidney Disease on Nanomechanics of the Endothelial Glycocalyx Are Mediated by the Mineralocorticoid Receptor

Endothelial mechanics control vascular reactivity and are regulated by the mineralocorticoid receptor (MR) and its downstream target, the epithelial Na⁺ channel (ENaC). Endothelial dysfunction is a hallmark of chronic kidney disease (CKD), but its mechanisms are poorly understood. We hypothesized that CKD disrupts endothelial mechanics in an MR/ENaC-dependent process.

METHODS

Primary human endothelial cells were cultured with uremic serum derived from children with stage 3-5 (predialysis) CKD or adult hemodialysis (HD) patients or healthy controls. The height and stiffness of the endothelial glycocalyx (eGC) and cortex were monitored by atomic force microscopy (AFM) using an ultrasensitive mechanical nanosensor.

RESULTS

In a stage-dependent manner, sera from children with CKD induced a significant increase in eGC and cortex stiffness and an incremental reduction of the eGC height. AFM measurements were significantly associated with individual pulse wave velocity and serum concentrations of gut-derived uremic toxins. Serum from HD patients increased MR expression and mechanical stiffness of the endothelial cortex, an effect reversed by MR and ENaC antagonists, decreased eNOS expression and NO bioavailability, and augmented monocyte adhesion.

CONCLUSION

These data indicate progressive structural damage of the endothelial surface with diminishing kidney function and identify the MR as a mediator of CKD-induced endothelial dysfunction.

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

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

Vascular Calcification in Chronic Kidney Disease: Distinct Features of Pathogenesis and Clinical Implication

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD) and leads to increased cardiovascular morbidity and mortality. In patients with CKD, traditional factors do not fully explain the high prevalence of VC. This suggests that a CKD-specific pathobiology is involved in the development of VC and mounting evidence indicates that VC in CKD patients has distinct features of clinical presentation and that clinical implications are changed compared to those in the general population. In this review, we discuss the mechanism, diagnostic imaging modalities, clinical features and implications, and management of VC in patients with CKD.

Chronic kidney disease (CKD) is associated with a higher prevalence of vascular calcification (VC) and cardiovascular disease. VC in CKD patients showed different pathophysiological features from those of the general population. The pathogenesis of VC in CKD is a highly organized process, and prior studies have suggested that patients with CKD have their own specific contributors to the phenotypic change of vascular smooth muscle cells (VSMCs), including uremic toxins, CKD-mineral and bone disease (CKD-MBD), inflammation, and oxidative stress. For the diagnosis and monitoring of VC in CKD, several imaging modalities, including plain radiography, ultrasound, and computed tomography have been utilized. VC in CKD patients has distinct clinical features and implications. CKD patients revealed a more intense and more prevalent calcification on the intimal and medial layers, whereas intimal calcification is predominantly observed in the general population. While a higher VC score is clearly associated with a higher risk of all-cause mortality and cardiovascular events, a greater VC score in CKD patients does not fully reflect the burden of atherosclerosis, because they have more calcification at equal volumes of atheromatous plaques. The primary goal of VC treatment in CKD is the prevention of VC progression, and the main management is to control the biochemical components of CKD-MBD. Cinacalcet and non-calcium-containing phosphate binders are the mainstay of VC prevention in CKD-MBD management. VC in patients with CKD is an ongoing area of research and is expected to advance soon.

Dextromethorphan Reduces Oxidative Stress and Inhibits Uremic Artery Calcification

Medial vascular calcification has emerged as a key factor contributing to cardiovascular mortality in patients with chronic kidney disease (CKD). Vascular smooth muscle cells (VSMCs) with osteogenic transdifferentiation play a role in vascular calcification. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors reduce reactive oxygen species (ROS) production and calcified-medium-induced calcification of VSMCs. This study investigates the effects of dextromethorphan (DXM), an NADPH oxidase inhibitor, on vascular calcification. We used in vitro and in vivo studies to evaluate the effect of DXM on artery changes in the presence of hyperphosphatemia. The anti-vascular calcification effect of DXM was tested in adenine-fed Wistar rats. High-phosphate medium induced ROS production and calcification of VSMCs. DXM significantly attenuated the increase in ROS production, the decrease in ATP, and mitochondria membrane potential during the calcified-medium-induced VSMC calcification process (p < 0.05). The protective effect of DXM in calcified-medium-induced VSMC calcification was not further increased by NADPH oxidase inhibitors, indicating that NADPH oxidase mediates the effect of DXM. Furthermore, DXM decreased aortic calcification in Wistar rats with CKD. Our results suggest that treatment with DXM can attenuate vascular oxidative stress and ameliorate vascular calcification.

Molecular Interactions Between Vascular Smooth Muscle Cells and Macrophages in Atherosclerosis

Atherosclerosis is the largest contributor toward life-threatening cardiovascular events. Cellular activity and cholesterol accumulation lead to vascular remodeling and the formation of fatty plaques. Complications arise from blood clots, forming at sites of plaque development, which may detach and result in thrombotic occlusions. Vascular smooth muscle cells and macrophages play dominant roles in atherosclerosis. A firm understanding of how these cells influence and modulate each other is pivotal for a better understanding of the disease and the development of novel therapeutics. Recent studies have investigated molecular interactions between both cell types and their impact on disease progression. Here we aim to review the current knowledge. Intercellular communications through soluble factors, physical contact, and extracellular vesicles are discussed. We also present relevant background on scientific methods used to study the disease, the general pathophysiology and intracellular factors involved in phenotypic modulation of vascular smooth muscle cells. We conclude this review with a discussion of the current state, shortcomings and potential future directions of the field.

Arterial Remodelling in Chronic Kidney Disease: Impact of Uraemic Toxins and New Pharmacological Approaches

Chronic kidney disease (CKD) is a major public health concern that affects around 10 percent of the world’s population. The severity of CKD is mainly due to the high prevalence of cardiovascular (CV) complications in this population. The aim of this review is to describe the arterial remodelling associated with CKD, to provide a quick overview of the mechanisms involved and to review the recent pharmacological approaches aimed at improving vascular health in CKD. CKD patients are exposed to metabolic and haemodynamic disorders that may affect the CV system. Large artery functional and geometric abnormalities have been well documented in CKD patients and are associated with an increase in arterial stiffness and a maladaptive remodelling. Uraemic toxins, such as indoxyl sulphate, p-cresyl sulphate, protein carbamylation and advanced glycation products, exert various effects on vascular smooth muscle cell functions. The low-grade inflammation associated with CKD may also affect arterial wall composition and remodelling. It is worth noting that the CV risk for CKD patients remains high despite the pharmacological control of traditional CV risk factors, suggesting the need for innovative therapeutic strategies. An interventional study targeting the NLRP3 inflammasome has provided some interesting preliminary results that need to be confirmed, especially in terms of safety.

Early inflammatory changes and CC chemokine ligand-8 upregulation in the heart contribute to uremic cardiomyopathy

Uremic cardiomyopathy is a common complication in chronic kidney disease (CKD) patients, accounting for a high mortality rate. Several mechanisms have been proposed to link CKD and cardiac alterations; however, the early cardiac modifications that occur in CKD that may trigger cardiac remodeling and dysfunction remain largely unexplored. Here, in a mouse model of CKD induced by 5/6 nephrectomy, we first analyzed the early transcriptional and inflammatory changes that occur in the heart. Five days after 5/6 nephrectomy, RNA-sequencing showed the upregulation of 54 genes in the cardiac tissue of CKD mice and the enrichment of biological processes related to immune system processes. Increased cardiac infiltration of T-CD4⁺ lymphocytes, myeloid cells, and macrophages during early CKD was observed. Next, since CC chemokine ligand-8 (CCL8) was one of the most upregulated genes in the heart of mice with early CKD, we investigated the effect of acute and transient CCL8 inhibition on uremic cardiomyopathy severity. An increase in CCL8 protein levels was confirmed in the heart of early CKD mice. CCL8 inhibition attenuated the early infiltration of T-CD4⁺ lymphocytes and macrophages to the cardiac tissue, leading to a protection against chronic cardiac fibrotic remodeling, inflammation and cardiac dysfunction induced by CKD. Altogether, our data show the occurrence of transcriptional and inflammatory changes in the heart during the early phases of CKD and identify CCL8 as a key contributor to the early cardiac inflammatory state that triggers further cardiac remodeling and dysfunction in uremic cardiomyopathy.

Role of crosstalk between endothelial cells and smooth muscle cells in vascular calcification in chronic kidney disease

Chronic kidney disease (CKD) is a severe health problem worldwide, and vascular calcification (VC) contributes substantially to the cardiovascular morbidity and high mortality of CKD. CKD is often accompanied by a variety of pathophysiological states, such as inflammation, oxidative stress, hyperglycaemia, hyperparathyroidism and haemodynamic derangement, that can cause injuries to smooth muscle cells (SMCs) and endothelial cells (ECs) to promote VC. Similar to SMCs, whose role has been widely explored in VC, ECs may contribute to VC via osteochondral transdifferentiation, apoptosis, etc. In addition, given their location in the innermost layer of the blood vessel lumen and preferential reception of various pro‐calcification stimuli, ECs can pass messages to vascular wall cells and communicate with them. Crosstalk between ECs and SMCs via cytokines through a paracrine mechanism, extracellular vesicles, miRNAs and myoendothelial gap junctions also plays a role in VC. In this review, we emphasize the role of intercellular crosstalk between ECs and SMCs in VC associated with CKD.

Kv1.3 Channel Inhibition Limits Uremia-Induced Calcification in Mouse and Human Vascular Smooth Muscle

Chronic kidney disease (CKD) significantly increases cardiovascular risk. In advanced CKD stages, accumulation of toxic circulating metabolites and mineral metabolism alterations triggers vascular calcification, characterized by vascular smooth muscle cell (VSMC) transdifferentiation and loss of the contractile phenotype. Phenotypic modulation of VSMC occurs with significant changes in gene expression. Even though ion channels are an integral component of VSMC function, the effects of uremia on ion channel remodeling has not been explored. We used an in vitro model of uremia-induced calcification of human aorta smooth muscle cells (HASMCs) to study the expression of 92 ion channel subunit genes. Uremic serum-induced extensive remodeling of ion channel expression consistent with loss of excitability but different from the one previously associated with transition from contractile to proliferative phenotypes. Among the ion channels tested, we found increased abundance and activity of voltage-dependent K+ channel Kv1.3. Enhanced Kv1.3 expression was also detected in aorta from a mouse model of CKD. Pharmacological inhibition or genetic ablation of Kv1.3 decreased the amount of calcium phosphate deposition induced by uremia, supporting an important role for this channel on uremia-induced VSMC calcification.

Uremic Toxins Affecting Cardiovascular Calcification: A Systematic Review

Cardiovascular calcification is highly prevalent and associated with increased morbidity in chronic kidney disease (CKD). This review examines the impact of uremic toxins, which accumulate in CKD due to a failing kidney function, on cardiovascular calcification. A systematic literature search identified 41 uremic toxins that have been studied in relation to cardiovascular calcification. For 29 substances, a potentially causal role in cardiovascular calcification was addressed in in vitro or animal studies. A calcification-inducing effect was revealed for 16 substances, whereas for three uremic toxins, namely the guanidino compounds asymmetric and symmetric dimethylarginine, as well as guanidinosuccinic acid, a calcification inhibitory effect was identified in vitro. At a mechanistic level, effects of uremic toxins on calcification could be linked to the induction of inflammation or oxidative stress, smooth muscle cell osteogenic transdifferentiation and/or apoptosis, or alkaline phosphatase activity. For all middle molecular weight and protein-bound uremic toxins that were found to affect cardiovascular calcification, an increasing effect on calcification was revealed, supporting the need to focus on an increased removal efficiency of these uremic toxin classes in dialysis. In conclusion, of all uremic toxins studied with respect to calcification regulatory effects to date, more uremic toxins promote rather than reduce cardiovascular calcification processes. Additionally, it highlights that only a relatively small part of uremic toxins has been screened for effects on calcification, supporting further investigation of uremic toxins, as well as of associated post-translational modifications, on cardiovascular calcification processes.

Aldosterone enhances high phosphate-induced vascular calcification through inhibition of AMPK-mediated autophagy

It remains unclear whether the necessity of calcified mellitus induced by high inorganic phosphate (Pi) is required and the roles of autophagy plays in aldosterone (Aldo)‐enhanced vascular calcification (VC) and vascular smooth muscle cell (VSMC) osteogenic differentiation. In the present study, we found that Aldo enhanced VC both in vivo and in vitro only in the presence of high Pi, alongside with increased expression of VSMC osteogenic proteins (BMP2, Runx2 and OCN) and decreased expression of VSMC contractile proteins (α‐SMA, SM22α and smoothelin). However, these effects were blocked by mineralocorticoid receptor inhibitor, spironolactone. In addition, the stimulatory effects of Aldo on VSMC calcification were further accelerated by the autophagy inhibitor, 3‐MA, and were counteracted by the autophagy inducer, rapamycin. Moreover, inhibiting adenosine monophosphate‐activated protein kinase (AMPK) by Compound C attenuated Aldo/MR‐enhanced VC. These results suggested that Aldo facilitates high Pi‐induced VSMC osteogenic phenotypic switch and calcification through MR‐mediated signalling pathways that involve AMPK‐dependent autophagy, which provided new insights into Aldo excess‐associated VC in various settings.

Uremic Toxins and Vascular Calcification-Missing the Forest for All the Trees

The cardiorenal syndrome relates to the detrimental interplay between the vascular system and the kidney. The uremic milieu induced by reduced kidney function alters the phenotype of vascular smooth muscle cells (VSMC) and promotes vascular calcification, a condition which is strongly linked to cardiovascular morbidity and mortality. Biological mechanisms involved include generation of reactive oxygen species, inflammation and accelerated senescence. A better understanding of the vasotoxic effects of uremic retention molecules may reveal novel avenues to reduce vascular calcification in CKD. The present review aims to present a state of the art on the role of uremic toxins in pathogenesis of vascular calcification. Evidence, so far, is fragmentary and limited with only a few uremic toxins being investigated, often by a single group of investigators. Experimental heterogeneity furthermore hampers comparison. There is a clear need for a concerted action harmonizing and standardizing experimental protocols and combining efforts of basic and clinical researchers to solve the complex puzzle of uremic vascular calcification.

Gustatory Function and the Uremic Toxin, Phosphate, Are Modulators of the Risk of Vascular Calcification among Patients with Chronic Kidney Disease: A Pilot Study

Patients with chronic kidney disease (CKD) have an increased risk of vascular calcification (VC), including aortic arch calcification (AAC). Few investigated the influence of gustatory function on the probability of having VC. We examined whether gustatory function results modulated the probability of having VC in patients with CKD. We prospectively enrolled adults with CKD (estimated glomerular filtration rate <60 mL/min/1.73 m²), with their AAC rated semi-quantitatively and gustatory function assessed by objective and subjective approaches. Multiple logistic regression was used to analyze the relationship between gustatory function results and AAC. Those with AAC had significantly better objective gustatory function in aggregate scores (p = 0.039) and categories (p = 0.022) and less defective bitter taste (p = 0.045) and scores (p = 0.037) than those without. Multiple regression analyses showed that higher aggregate scores (odds ratio (OR) 1.288, p = 0.032), or better gustatory function, and higher bitter taste scores (OR 2.558, p = 0.019) were each associated with a higher probability of having AAC among CKD patients; such an association was modulated by serum phosphate levels. In conclusion, better gustatory function was independently correlated with having AAC among CKD patients. A follow-up of VC severity may be an underrecognized component of care for CKD patients with a preserved gustatory function.

Superficial Femoral Artery Calcification Is a Novel Risk Factor of Microvascular Complications in T2DM Patients

Microvascular complications are prevalent in patients with type 2 diabetes mellitus (T2DM), resulting in increased risk of cardiovascular mortality. However, it is unclear whether above-knee artery calcification relates to microvascular complications. This study was aimed to investigate the role of calcification in superficial femoral arteries (SFA), the major above-knee artery, compared with anterior tibial arteries (ATA) and posterior tibial arteries (PTA), in T2DM-related microvascular complications and explore its risk factors. A single-center and observational study involving 359 T2DM patients was conducted. Clinical and laboratory data were collected. SFA calcification was evaluated by ultrasonography. Compared with ATA and PTA calcification, operating characteristics curve analysis showed that SFA calcification was the strongest predictor (63.1% sensitivity and 69.2% specificity) for T2DM-related microvascular complications (diabetic neuropathy, diabetic nephropathy and diabetic retinopathy). With the severity of SFA calcification increased, age, duration of T2DM, and SBP were significantly elevated, but triglyceride and glucose index and estimated glomerular filtration rate (eGFR) were significantly reduced (all P < 0.05). Multivariate logistic analysis showed that eGFR (OR 0.953; 95% CI 0.931-0.976; P < 0.001) was an independent risk factor of SFA calcification, especially in young patients with HbA1c > 7.0. We identified SFA calcification as a good predictor of microvascular complications in T2DM patients. Reduced eGFR was significantly associated with increased SFA calcification prevalence, especially in young T2DM patients with bad controlled hyperglycemia.

The Impact of Uremic Toxins on Vascular Smooth Muscle Cell Function

Chronic kidney disease (CKD) is associated with profound vascular remodeling, which accelerates the progression of cardiovascular disease. This remodeling is characterized by intimal hyperplasia, accelerated atherosclerosis, excessive vascular calcification, and vascular stiffness. Vascular smooth muscle cell (VSMC) dysfunction has a key role in the remodeling process. Under uremic conditions, VSMCs can switch from a contractile phenotype to a synthetic phenotype, and undergo abnormal proliferation, migration, senescence, apoptosis, and calcification. A growing body of data from experiments in vitro and animal models suggests that uremic toxins (such as inorganic phosphate, indoxyl sulfate and advanced-glycation end products) may directly impact the VSMCs’ physiological functions. Chronic, low-grade inflammation and oxidative stress—hallmarks of CKD—are also strong inducers of VSMC dysfunction. Here, we review current knowledge about the impact of uremic toxins on VSMC function in CKD, and the consequences for pathological vascular remodeling.