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

Quantifying carotid stiffness in chronic kidney disease using ultrafast ultrasound imaging

Background

The mortality and disability of chronic kidney disease (CKD) are highly linked to the incidence of atherosclerotic cardiovascular events. Numerous clinical biochemical indicators of renal function often only increase in advanced stages of CKD, driving an urgent need for reliable indicators of atherosclerosis in early CKD. Ultrafast pulse wave velocity (ufPWV) can evaluate the stiffness of the straight carotid in vivo and quantitatively reflect the degree of early atherosclerosis. However, the use of ufPWV in CKD has not yet been reported. In this study, we aimed to explore the association between carotid stiffness, quantified using ufPWV, and renal function in CKD patients.

Methods

This cross-sectional study enrolled a total of 582 participants between March 2017 and May 2022 in the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine. Among those, 205 individuals without a history of CKD and estimated glomerular filtration rate (eGFR) ≥90 mL/min/1.73 m2 were included as controls. According to the Kidney Disease Outcomes Quality Initiative (K/DOQI) expert group of the American Kidney Foundation staging for CKD, 44 stages 1 and 2 CKD patients were included in the early CKD group, whereas 49 stages 3, 4, and 5 CKD patients were included in the advanced CKD group. Clinical and serum parameters, ultrasonic characteristics including carotid intima-media thickness (cIMT), and pulse wave velocity at the beginning of systole (PWV-BS) and pulse wave velocity at the end of systole (PWV-ES) of systole were analyzed. One-way analysis of variance (ANOVA) and least significant difference (LSD) tests were performed to compare cIMT, PWV-BS, and PWV-ES among subgroups in pairs. Pearson's correlation analysis, scatter plots, and subgroups correlation analysis were used to determine the relationships among ultrasound characteristics (cIMT, PWV-BS, PWV-ES), and major cardiovascular risk factors.

Results

PWV-BS and PWV-ES for the early and advanced CKD groups were significantly higher than those for controls (all P<0.05). PWV-ES had the greatest correlation with age (r=0.474, P<0.001). PWV-ES had the greatest increase with age in the early CKD group (r=0.698, P<0.001).

Conclusions

ufPWV can be used for the quantitative evaluation of carotid stiffness in CKD patients. PWV-ES may be more advantageous in the assessment of carotid atherosclerosis in early CKD patients.

Bile Acid Network and Vascular Calcification-Associated Diseases: Unraveling the Intricate Connections and Therapeutic Potential

Bile acids play a crucial role in promoting intestinal nutrient absorption and biliary cholesterol excretion, thereby protecting the liver from cholesterol accumulation and bile acid toxicity. Additionally, bile acids can bind to specific nuclear and membrane receptors to regulate energy expenditure and specific functions of particular tissues. Vascular calcification refers to the pathological process of calcium-phosphate deposition in blood vessel walls, which serves as an independent predictor for cardiovascular adverse events. In addition to aging, this pathological change is associated with aging-related diseases such as atherosclerosis, hypertension, chronic kidney disease, diabetes mellitus, and osteoporosis. Emerging evidence suggests a close association between the bile acid network and these aforementioned vascular calcification-associated conditions. Several bile acids have been proven to participate in calcium-phosphate metabolism, affecting the transdifferentiation of vascular smooth muscle cells and thus influencing vascular calcification. Targeting the bile acid network shows potential for ameliorating these diseases and their concomitant vascular calcification by regulating pathways such as energy metabolism, inflammatory response, oxidative stress, and cell differentiation. Here, we present a summary of the metabolism and functions of the bile acid network and aim to provide insights into the current research on the profound connections between the bile acid network and these vascular calcification-associated diseases, as well as the therapeutic potential.

Vascular calcification: from the perspective of crosstalk

Vascular calcification (VC) is highly correlated with cardiovascular disease morbidity and mortality, but anti-VC treatment remains an area to be tackled due to the ill-defined molecular mechanisms. Regardless of the type of VC, it does not depend on a single cell but involves multi-cells/organs to form a complex cellular communication network through the vascular microenvironment to participate in the occurrence and development of VC. Therefore, focusing only on the direct effect of pathological factors on vascular smooth muscle cells (VSMCs) tends to overlook the combined effect of other cells and VSMCs, including VSMCs-VSMCs, ECs-VMSCs, Macrophages-VSMCs, etc. Extracellular vesicles (EVs) are a collective term for tiny vesicles with a membrane structure that are actively secreted by cells, and almost all cells secrete EVs. EVs docked on the surface of receptor cells can directly mediate signal transduction or transfer their contents into the cell to elicit a functional response from the receptor cells. They have been proven to participate in the VC process and have also shown attractive therapeutic prospects. Based on the advantages of EVs and the ability to be detected in body fluids, they may become a novel therapeutic agent, drug delivery vehicle, diagnostic and prognostic biomarker, and potential therapeutic target in the future. This review focuses on the new insight into VC molecular mechanisms from the perspective of crosstalk, summarizes how multi-cells/organs interactions communicate via EVs to regulate VC and the emerging potential of EVs as therapeutic methods in VC. We also summarize preclinical experiments on crosstalk-based and the current state of clinical studies on VC-related measures.

Extracellular vesicles in atherosclerosis and vascular calcification: the versatile non-coding RNAs from endothelial cells and vascular smooth muscle cells

Atherosclerosis (AS) is characterized by the accumulation of lipids, fibrous elements, and calcification in the innermost layers of arteries. Vascular calcification (VC), the deposition of calcium and phosphate within the arterial wall, is an important characteristic of AS natural history. However, medial arterial calcification (MAC) differs from intimal calcification and cannot simply be explained as the consequence of AS. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are directly involved in AS and VC processes. Understanding the communication between ECs and VSMCs is critical in revealing mechanisms underlying AS and VC. Extracellular vesicles (EVs) are found as intercellular messengers in kinds of physiological processes and pathological progression. Non-coding RNAs (ncRNAs) encapsulated in EVs are involved in AS and VC, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). The effects of ncRNAs have not been comprehensively understood, especially encapsulated in EVs. Some ncRNAs have demonstrated significant roles in AS and VC, but it remains unclear the functions of the majority ncRNAs detected in EVs. In this review, we summarize ncRNAs encapsulated in EC-EVs and VSMC-EVs, and the signaling pathways that are involved in AS and VC.

Endothelial Cell Dysfunction and Increased Cardiovascular Risk in Patients With Chronic Kidney Disease

The endothelium is considered to be the gatekeeper of the vessel wall, maintaining and regulating vascular integrity. In patients with chronic kidney disease, protective endothelial cell functions are impaired due to the proinflammatory, prothrombotic and uremic environment caused by the decline in kidney function, adding to the increase in cardiovascular complications in this vulnerable patient population. In this review, we discuss endothelial cell functioning in healthy conditions and the contribution of endothelial cell dysfunction to cardiovascular disease. Further, we summarize the phenotypic changes of the endothelium in chronic kidney disease patients and the relation of endothelial cell dysfunction to cardiovascular risk in chronic kidney disease. We also review the mechanisms that underlie endothelial changes in chronic kidney disease and consider potential pharmacological interventions that can ameliorate endothelial health.

Calciphylaxis and its co-occurrence with connective tissue diseases

Calciphylaxis, also known as calcific uremic arteriopathy, is a rare calcification syndrome that presents as ischemic skin necrosis and severe pain. It has a high mortality rate and is characterised by calcification of the small and medium arteries and micro-thrombosis. Calciphylaxis mainly occurs in patients with end-stage renal disease. In recent years, there have been an increasing number of cases of calciphylaxis associated with connective tissue diseases. Given the absence of clear diagnostic criteria for calciphylaxis thus far, an early diagnosis is crucial for designing an effective multidisciplinary treatment plan. In this article, we review the research progress on calciphylaxis and describe its characteristics in the context of connective tissue diseases.

Soluble guanylate cyclase agonist, isoliquiritigenin attenuates renal damage and aortic calcification in a rat model of chronic kidney failure

AIMS

Chronic kidney disease (CKD) is a growing fatal health problem worldwide associated with vascular calcification. Therapeutic approaches are limited with higher costs and poor outcomes. Adenine supplementation is one of the most relevant CKD models to human. Insufficient Nitric Oxide (NO)/ cyclic Guanosine Monophosphate (cGMP) signaling plays a key role in rapid development of renal fibrosis. Natural products display proven protection against CKD. Current study therefore explored isoliquiritigenin, a bioflavonoid extracted from licorice roots, potential as a natural activator for soluble Guanylate Cyclase (sGC) in a CKD rat model.

MATERIALS AND METHODS

60 male Wistar rats were grouped into Control group (n = 10) and the remaining rats received adenine (200 mg/kg, p.o) for 2 wk to induce CKD. They were equally sub-grouped into: Adenine untreated group and 4 groups orally treated by isoliquiritigenin low or high dose (20 or 40 mg/kg) with/without a selective sGC inhibitor, ODQ (1-H(1,2,4)oxadiazolo(4,3-a)-quinoxalin-1-one, 2 mg/kg, i.p) for 8 wk.

KEY FINDINGS

Long-term treatment with isoliquiritigenin dose-dependently and effectively amended adenine-induced chronic renal and endothelial dysfunction. It not only alleviated renal fibrosis and apoptosis markers but also aortic calcification. Additionally, this chalcone neutralized renal inflammatory response and oxidative stress. Isoliquiritigenin beneficial effects were associated with up-regulation of serum NO, renal and aortic sGC, cGMP and its dependent protein kinase (PKG). However, co-treatment with ODQ antagonized isoliquiritigenin therapeutic impact.

SIGNIFICANCE

Isoliquiritigenin seems to exert protective effects against CKD and vascular calcification by activating sGC, increasing cGMP and its downstream PKG.

Pathogenesis of Chronic Kidney Disease Is Closely Bound up with Alzheimer's Disease, Especially via the Renin-Angiotensin System

Chronic kidney disease (CKD) is a clinical syndrome secondary to the definitive change in function and structure of the kidney, which is characterized by its irreversibility and slow and progressive evolution. Alzheimer's disease (AD) is characterized by the extracellular accumulation of misfolded β-amyloid (Aβ) proteins into senile plaques and the formation of neurofibrillary tangles (NFTs) containing hyperphosphorylated tau. In the aging population, CKD and AD are growing problems. CKD patients are prone to cognitive decline and AD. However, the connection between CKD and AD is still unclear. In this review, we take the lead in showing that the development of the pathophysiology of CKD may also cause or exacerbate AD, especially the renin-angiotensin system (RAS). In vivo studies had already shown that the increased expression of angiotensin-converting enzyme (ACE) produces a positive effect in aggravating AD, but ACE inhibitors (ACEIs) have protective effects against AD. Among the possible association of risk factors in CKD and AD, we mainly discuss the RAS in the systemic circulation and the brain.

Extracellular Vesicles and Ischemic Cardiovascular Diseases

Characterized by coronary artery obstruction or stenosis, ischemic cardiovascular diseases as advanced stages of coronary heart diseases commonly lead to left ventricular aneurysm, ventricular septal defect, and mitral insufficiency. Extracellular vesicles (EVs) secreted by diverse cells in the body exert roles in cell-cell interactions and intrinsic cellular regulations. With a lipid double-layer membrane and biological components such as DNA, protein, mRNA, microRNAs (miRNA), and siRNA inside, the EVs function as paracrine signaling for the pathophysiology of ischemic cardiovascular diseases and maintenance of the cardiac homeostasis. Unlike stem cell transplantation with the potential tumorigenicity and immunogenicity, the EV-based therapeutic strategy is proposed to satisfy the demand for cardiac repair and regeneration while the circulating EVs detected by a noninvasive approach can act as precious biomarkers. In this chapter, we extensively summarize the cardioprotective functions of native EVs and bioengineered EVs released from stem cells, cardiomyocytes, cardiac progenitor cells (CPCs), endothelial cells, fibroblast, smooth muscle cells, and immune cells. In addition, the potential of EVs as robust molecule biomarkers is discussed for clinical diagnosis of ischemic cardiovascular disease, attributed to the same pathology of EVs as that of their origin. Finally, we highlight EV-based therapy as a biocompatible alternative to direct cell-based therapy for ischemic cardiovascular diseases.

The role of extracellular vesicles in vascular calcification in chronic kidney disease

Widespread vascular calcification (VC) in patients with chronic kidney disease (CKD) is the pathological basis for the development of cardiovascular disease, and VC has been identified as an independent risk factor for increased cardiovascular mortality in cases of CKD. While VC was earlier thought to be a passive deposition process following calcium and phosphorus supersaturation, recent studies have suggested that it is an active, modifiable, biological process similar to bone development. The involvement of extracellular vesicles (EVs) in the process of VC has been reported as an important transporter of material transport and intercellular communication. This paper reviews the mechanism of the role of EVs, especially exosomes, in VC and the regulation of VC by stem cell-derived EVs, and discusses the possible and promising application of related therapeutic targets in the clinical setting.

Endothelial Cell TGF-β (Transforming Growth Factor-Beta) Signaling Regulates Venous Adaptive Remodeling to Improve Arteriovenous Fistula Patency

BACKGROUND

Arteriovenous fistulae (AVF) are the gold standard for vascular access for hemodialysis. Although the vein must thicken and dilate for successful hemodialysis, excessive wall thickness leads to stenosis causing AVF failure. Since TGF-β (transforming growth factor-beta) regulates ECM (extracellular matrix) deposition and smooth muscle cell (SMC) proliferation-critical components of wall thickness-we hypothesized that disruption of TGF-β signaling prevents excessive wall thickening during venous remodeling.

METHODS

A mouse aortocaval fistula model was used. SB431542-an inhibitor of TGF-β receptor I-was encapsulated in nanoparticles and applied to the AVF adventitia in C57BL/6J mice. Alternatively, AVFs were created in mice with conditional disruption of TGF-β receptors in either SMCs or endothelial cells. Doppler ultrasound was performed serially to confirm patency and to measure vessel diameters. AVFs were harvested at predetermined time points for histological and immunofluorescence analyses.

RESULTS

Inhibition of TGF-β signaling with SB431542-containing nanoparticles significantly reduced p-Smad2-positive cells in the AVF wall during the early maturation phase (days 7-21) and was associated with decreased AVF wall thickness that showed both decreased collagen density and decreased SMC proliferation. SMC-specific TGF-β signaling disruption decreased collagen density but not SMC proliferation or wall thickness. Endothelial cell-specific TGF-β signaling disruption decreased both collagen density and SMC proliferation in the AVF wall and was associated with reduced wall thickness, increased outward remodeling, and improved AVF patency.

CONCLUSIONS

Endothelial cell-targeted TGF-β inhibition may be a translational strategy to improve AVF patency.

Phosphate in the Context of Cognitive Impairment and Other Neurological Disorders Occurrence in Chronic Kidney Disease

The nervous system and the kidneys are linked under physiological states to maintain normal body homeostasis. In chronic kidney disease (CKD), damaged kidneys can impair the central nervous system, including cerebrovascular disease and cognitive impairment (CI). Recently, kidney disease has been proposed as a new modifiable risk factor for dementia. It is reported that uremic toxins may have direct neurotoxic (astrocyte activation and neuronal death) and/or indirect action through vascular effects (cerebral endothelial dysfunction, calcification, and inflammation). This review summarizes the evidence from research investigating the pathophysiological effects of phosphate toxicity in the nervous system, raising the question of whether the control of hyperphosphatemia in CKD would lower patients’ risk of developing cognitive impairment and dementia.

The Contribution of Extracellular Vesicles From Senescent Endothelial and Vascular Smooth Muscle Cells to Vascular Calcification

Vascular calcification is an irreversible pathological process associated with a loss of vascular wall function. This process occurs as a result of aging and age-related diseases, such as cardiovascular and chronic kidney diseases, and leads to comorbidities. During these age-related diseases, the endothelium accumulates senescent cells, which stimulate calcification in vascular smooth muscle cells. Currently, vascular calcification is a silent pathology, and there are no early diagnostic tools. Therefore, by the time vascular calcification is diagnosed, it is usually untreatable. Some mediators, such as oxidative stress, inflammation, and extracellular vesicles, are inducers and promoters of vascular calcification. They play a crucial role during vascular generation and the progression of vascular calcification. Extracellular vesicles, mainly derived from injured endothelial cells that have acquired a senescent phenotype, contribute to calcification in a manner mostly dependent on two factors: (1) the number of extracellular vesicles released, and (2) their cargo. In this review, we present state-of-the-art knowledge on the composition and functions of extracellular vesicles involved in the generation and progression of vascular calcification.

Circulating miRNA-29b and Sclerostin Levels Correlate with Coronary Artery Calcification and Cardiovascular Events in Maintenance Hemodialysis Patients

Objective

Coronary artery calcification (CAC) is a common complication in end-stage renal disease (ESRD) patients undergoing maintenance hemodialysis (MHD), and the extent of CAC is a predominant predictor of cardiovascular outcomes in MHD patients. In this study, we sought to uncover the relationship between circulating miRNA-29b, sclerostin levels, CAC, and cardiovascular events (CVEs) in MHD patients.

Methods

This study recruited patients receiving MHD for at least three months in the Hainan General Hospital between January 2016 and June 2019, and all patients were followed up 24 months for CVEs. The serum level of sclerostin was determined by enzyme-linked immunosorbent assay (ELISA) and miRNA-29b expression by real-time qPCR (RT-qPCR). All patients received cardiac CT scans to evaluate CAC, and CAC scores were expressed in Agatston units. The MHD patients with CACs <100 were arranged into the CAC (<100) group, those with 100–400 CACs into the CAC (100–400) group, and those with CACs >400 into the CAC (>400) group. Net reclassification index (NRI) and integrated discrimination index (IDI) were calculated to assess the predictive performance of serum sclerostin level for the occurrence of CVEs.

Results

Compared with the CAC (<100) group, the CAC (>400) group had higher proportions of older patients, hypertension and diabetes mellitus patients, longer dialysis duration, higher mean arterial pressure (MAP), higher levels of high-sensitivity C-reactive protein (hs-CRP), alkaline phosphatase (ALP), and phosphate (P < 0.05). It was found that the CAC (100–400) and CAC (>400) groups exhibited higher serum levels of sclerostin but lower levels of miRNA-29b than the CAC (<100) group (P < 0.05) and the CAC (>400) group had a higher level of sclerostin and a lower level of miRNA-29b than the CAC (100–400) group (P < 0.05). The circulating level of miRNA-29b was negatively correlated with the serum level of sclerostin in MHD patients (r = −0.329, P < 0.01). The multivariate logistic regression analysis showed that hs-CRP, phosphate, sclerostin, and miRNA-29b were independent risk factors for CAC in MHD patients (P < 0.05, Table 2). ROC for prediction of CAC by sclerostin yielded 0.773 AUC with 95% CI 0.683–0.864 (P < 0.01). As depicted by Kaplan–Meier curves of CVE incidence in MHD patients according to median sclerostin (491.88 pg/mL) and median miRNA-29b (Ct = 25.15), we found that serum levels of sclerostin and miRNA-29b were correlated with the incidence of CVEs in MHD patients. When a new model was used to predict the incidence of CVEs, NRI 95% CI was 0.60 (0.16–1.03) (P < 0.05) and IDI 95% CI was 0.002 (−0.014 to 0.025) (P < 0.05), suggesting that sclerostin added into the old model could improve the prediction of the incidence of CVEs.

Conclusions

These data suggest that circulating miRNA-29b and sclerostin levels are correlated with CAC and incidence of CVEs in MHD patients. Higher sclerostin and lower miRNA-29b may serve as independent risk factors for the incidence of CVEs in MHD patients.

The Role of AIF-1 in the Aldosterone-Induced Vascular Calcification Related to Chronic Kidney Disease: Evidence From Mice Model and Cell Co-Culture Model

Increasing evidence suggests that aldosterone (Aldo) plays an essential role in vascular calcification which is a serious threat to cardiovascular disease (CVD) developed from chronic kidney disease (CKD). However, the exact pathogenesis of vascular calcification is still unclear. First, we established CKD-associated vascular calcification mice model and knockout mice model to investigate the causal relationship between allograft inflammatory factor 1 (AIF-1) and vascular calcification. Then, endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) co-culture experiments were performed to further explore the mechanisms of calcification. The results of the Aldo intervention mice model and transgenic mice model showed that Aldo could cause calcification by increasing the AIF-1 level. The results of in vitro co-culture model of ECs and VSMCs showed that AIF-1 silence in ECs may alleviate Aldo-induced calcification of VSMCs. In conclusion, our study indicated that Aldo may induce vascular calcification related to chronic renal failure via the AIF-1 pathway which may provide a potential therapeutic target.

Fabrication and dialysis performance of functionalized multiwall carbon nanotubes integrated cellulose acetate/poly(vinylpyrrolidone) membranes

Mixed matrix membranes (MMMs) of cellulose acetate/poly(vinylpyrrolidone) (CA/PVP) infused with acid functionalized multiwall carbon nanotubes (f-MWCNTs) were fabricated by an immersion phase separation technique for hemodialysis application. Membranes were characterized using FTIR, water uptake, contact angle, TGA, DMA and SEM analysis. The FTIR was used to confirm the bonding interaction between CA/PVP membrane matrix and f-MWCNTs. Upon addition of f-MWCNTs, TGA thermograms and glass transition temperature indicated improved thermal stability of MMMs. The surface morphological analysis demonstrated revealed uniform distribution of f-MWCNTs and asymmetric membrane structure. The water uptake and contact angle confirmed that hydrophilicity was increased after incorporation of f-MWCNTs. The membranes demonstrated enhancement in water permeate flux, bovine serum albumin (BSA) rejection with the infusion of f-MWCNTs; whereas BSA based anti-fouling analysis using flux recovery ratio test shown up to 8.4% improvement. The urea and creatinine clearance performance of MMMs were evaluated by dialysis experiment. It has been found that f-MWCNTs integrated membranes demonstrated the higher urea and creatinine clearance with increase of 12.6% and 10.5% in comparison to the neat CA/PVP membrane. Thus, the prepared CA/PVP membranes embedded with f-MWCNTs can be employed for wide range of dialysis applications.

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.