Effect of metabolic syndrome and aging on Ca2+ dysfunction in coronary smooth muscle and coronary artery disease severity in Ossabaw miniature swine

Progressive aortic stiffness in aging C57Bl/6 mice displays altered contractile behaviour and extracellular matrix changes

Aortic stiffness is a hallmark of cardiovascular disease, but its pathophysiology remains incompletely understood. This study presents an in-dept characterization of aortic aging in male C57Bl/6 mice (2–24 months). Cardiovascular measurements include echocardiography, blood pressure measurement, and ex vivo organ chamber experiments. In vivo and ex vivo aortic stiffness increases with age, and precede the development of cardiac hypertrophy and peripheral blood pressure alterations. Contraction-independent stiffening (due to extracellular matrix changes) is pressure-dependent. Contraction-dependent aortic stiffening develops through heightened α₁-adrenergic contractility, aberrant voltage-gated calcium channel function, and altered vascular smooth muscle cell calcium handling. Endothelial dysfunction is limited to a modest decrease in sensitivity to acetylcholine-induced relaxation with age. Our findings demonstrate that progressive arterial stiffening in C57Bl/6 mice precedes associated cardiovascular disease. Aortic aging is due to changes in extracellular matrix and vascular smooth muscle cell signalling, and not to altered endothelial function.

A 24-month aging study in male C57Bl/6 mice reveals that aortic aging precedes cardiovascular disease and is due to changes in the extracellular matrix and vascular smooth muscle cell signaling.

Aortic Stiffness in L-NAME Treated C57Bl/6 Mice Displays a Shift From Early Endothelial Dysfunction to Late-Term Vascular Smooth Muscle Cell Dysfunction

Introduction and Aims: Endothelial dysfunction is recognized as a cardiovascular aging hallmark. Administration of nitric oxide synthase blocker N-Ω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) constitutes a well-known small animal model of cardiovascular aging. Despite extensive phenotypic characterization, the exact aortic function changes in L-NAME treated mice are largely unknown. Therefore, this study presents a longitudinal characterization of the aortic reactivity and biomechanical alterations in L-NAME treated C57Bl/6 mice.

Methods and Results: Male C57Bl/6 mice were treated with L-NAME (0.5 mg/ml drinking water) for 1, 2, 4, 8, or 16 weeks. Peripheral blood pressure measurement (tail-cuff) and transthoracic echocardiograms were recorded, showing progressive hypertension after 4 weeks of treatment and progressive cardiac hypertrophy after 8–16 weeks of treatment. Aortic stiffness was measured in vivo as aortic pulse wave velocity (aPWV, ultrasound) and ex vivo as Peterson modulus (E_p). Aortic reactivity and biomechanics were investigated ex vivo in thoracic aortic rings, mounted isometrically or dynamically-stretched in organ bath set-ups. Aortic stiffening was heightened in L-NAME treated mice after all treatment durations, thereby preceding the development of hypertension and cardiac aging. L-NAME treatment doubled the rate of arterial stiffening compared to control mice, and displayed an attenuation of the elevated aortic stiffness at high distending pressure, possibly due to late-term reduction of medial collagen types I, III, and IV content. Remarkably, endothelial dysfunction, measured by acetylcholine concentration-response stimulation in precontracted aortic rings, was only observed after short-term (1–4 weeks) treatment, followed by restoration of endothelial function which coincided with increased phosphorylation of endothelial nitric oxide synthase (S¹¹⁷⁷). In the late-disease phase (8–16 weeks), vascular smooth muscle cell (VSMC) dysfunction developed, including increased contribution of voltage-dependent calcium channels (assessed by inhibition with diltiazem), basal VSMC cytoplasmic calcium loading (assessed by removal of extracellular calcium), and heightened intracellular contractile calcium handling (assessed by measurement of sarcoplasmic reticulum-mediated transient contractions).

Conclusion: Arterial stiffness precedes peripheral hypertension and cardiac hypertrophy in chronic L-NAME treated male C57Bl/6 mice. The underlying aortic disease mechanisms underwent a distinct shift from early endothelial dysfunction to late-term VSMC dysfunction, with continued disease progression.

High-fidelity porcine models of metabolic syndrome: a contemporary synthesis

This review aims to describe and compare porcine models of metabolic syndrome. This syndrome and its associated secondary comorbidities are set to become the greatest challenge to healthcare providers and policy makers in the coming century. However, an incomplete understanding of the pathogenesis has left significant knowledge gaps in terms of efficacious therapeutics. To further our comprehension and, in turn, management of metabolic syndrome, appropriate high-fidelity models of the disease complex are of great importance. In this context, our review aims to assess the most promising porcine models of metabolic syndrome currently available for their similarity to the human phenotype. In addition, we aim to highlight the strengths and shortcomings of each model in an attempt to identify the most appropriate application of each. Although no porcine model perfectly recapitulates the human metabolic syndrome, several pose satisfactory approximations. The Ossabaw miniature swine in particular represents a highly translatable model that develops each of the core parameters of the syndrome with many of the associated secondary comorbidities. Future high-fidelity porcine models of metabolic syndrome need to focus on secondary sequelae replication, which may require extended induction period to reveal.

Intracellular Ca2+ Dysregulation in Coronary Smooth Muscle Is Similar in Coronary Disease of Humans and Ossabaw Miniature Swine

Intracellular free Ca2+ ([Ca2+]i) dysregulation occurs in coronary smooth muscle (CSM) in atherosclerotic coronary artery disease (CAD) of metabolic syndrome (MetS) swine. Our goal was to determine how CAD severity, arterial structure, and MetS risk factors associate with [Ca2+]i dysregulation in human CAD compared to changes in Ossabaw miniature swine. CSM cells were dispersed from coronary arteries of explanted hearts from transplant recipients and from lean and MetS swine with CAD. CSM [Ca2+]i elicited by Ca2+ influx and sarcoplasmic reticulum (SR) Ca2+ release and sequestration was measured with fura-2. Increased [Ca2+]i signaling was associated with advanced age and a greater media area in human CAD. Decreased [Ca2+]i signaling was associated with a greater number of risk factors and a higher plaque burden in human and swine CAD. Similar [Ca2+]i dysregulation exhibited in human and Ossabaw swine CSM provides strong evidence for the translational relevance of this large animal model.

Identification of Potential Biomarkers for CAD Using Integrated Expression and Methylation Data

DNA methylation plays an essential role in the pathogenesis of coronary artery disease (CAD) through regulating mRNA expressions. This study aimed to identify hub genes regulated by DNA methylation as biomarkers of CAD. Gene expression and methylation datasets of peripheral blood leukocytes (PBLs) of CAD were downloaded from the Gene Expression Omnibus (GEO) database. Subsequently, multiple computational approaches were performed to analyze the regulatory networks and to recognize hub genes. Finally, top hub genes were verified in a case-control study, based on their differential expressions and methylation levels between CAD cases and controls. In total, 535 differentially expressed-methylated genes (DEMGs) were identified and partitioned into 4 subgroups. TSS200 and 5′UTR were confirmed as high enrichment areas of differentially methylated CpGs sites (DMCs). The function of DEMGs is enriched in processes of histone H3-K27 methylation, regulation of post-transcription and DNA-directed RNA polymerase activity. Pathway enrichment showed DEMGs participated in the VEGF signaling pathway, adipocytokine signaling pathway, and PI3K-Akt signaling pathway. Besides, expressions of hub genes fibronectin 1 (FN1), phosphatase (PTEN), and tensin homolog and RNA polymerase III subunit A (POLR3A) were discordantly expressed between CAD patients and controls and related with DNA methylation levels. In conclusion, our study identified the potential biomarkers of PBLs for CAD, in which FN1, PTEN, and POLR3A were confirmed.

Calcium channel Orai1 promotes lymphocyte IL-17 expression and progressive kidney injury

We hypothesized that the store-operated calcium entry (SOCE) channel, Orai1, participates in the activation of Th17 cells and influences renal injury. In rats, following renal ischemia/reperfusion (I/R), there was a rapid and sustained influx of Orai1+ CD4 T cells and IL-17 expression was restricted to Orai1+ cells. When kidney CD4+ cells of post-acute kidney injury (post-AKI) rats were stimulated with angiotensin II and elevated Na+ (10-7 M/170 mM) in vitro, there was an enhanced response in intracellular Ca2+ and IL-17 expression, which was blocked by SOCE inhibitors 2APB, YM58483/BTP2, or AnCoA4. In vivo, YM58483/BTP2 (1 mg/kg) attenuated IL-17+ cell activation, inflammation, and severity of AKI following either I/R or intramuscular glycerol injection. Rats treated with high-salt diet (5-9 weeks after I/R) manifested progressive disease indicated by enhanced inflammation, fibrosis, and impaired renal function. These responses were significantly attenuated by YM58483/BTP2. In peripheral blood of critically ill patients, Orai1+ cells were significantly elevated by approximately 10-fold and Th17 cells were elevated by approximately 4-fold in AKI versus non-AKI patients. Further, in vitro stimulation of CD4+ cells from AKI patients increased IL-17, which was blocked by SOCE inhibitors. These data suggest that Orai1 SOCE is a potential therapeutic target in AKI and CKD progression.

Swine Disease Models for Optimal Vascular Engineering

Swine disease models are essential for mimicry of human metabolic and vascular pathophysiology, thereby enabling high-fidelity translation to human medicine. The worldwide epidemic of obesity, metabolic disease, and diabetes has prompted the focus on these diseases in this review. We highlight the remarkable similarity between Ossabaw miniature swine and humans with metabolic syndrome and atherosclerosis. Although the evidence is strongest for swine models of coronary artery disease, findings are generally applicable to any vascular bed. We discuss the major strengths and weaknesses of swine models. The development of vascular imaging is an example of optimal vascular engineering in swine. Although challenges regarding infrastructure and training of engineers in the use of swine models exist, opportunities are ripe for gene editing, studies of molecular mechanisms, and use of swine in coronary artery imaging and testing of devices that can move quickly to human clinical studies.

Variation in Coronary Atherosclerosis Severity Related to a Distinct LDL (Low-Density Lipoprotein) Profile: Findings From a Familial Hypercholesterolemia Pig Model

OBJECTIVE

In an adult porcine model of familial hypercholesterolemia (FH), coronary plaque development was characterized. To elucidate the underlying mechanisms of the observed inter-individual variation in disease severity, detailed lipoprotein profiles were determined. Approach and Results: FH pigs (3 years old, homozygous LDLR R84C mutation) received an atherogenic diet for 12 months. Coronary atherosclerosis development was monitored using serial invasive imaging and histology. A pronounced difference was observed between mildly diseased pigs which exclusively developed early lesions (maximal plaque burden, 25% [23%-34%]; n=5) and advanced-diseased pigs (n=5) which developed human-like, lumen intruding plaques (maximal plaque burden, 69% [57%-77%]) with large necrotic cores, intraplaque hemorrhage, and calcifications. Advanced-diseased pigs and mildly diseased pigs displayed no differences in conventional risk factors. Additional plasma lipoprotein profiling by size-exclusion chromatography revealed 2 different LDL (low-density lipoprotein) subtypes: regular and larger LDL. Cholesterol, sphingosine-1-phosphate, ceramide, and sphingomyelin levels were determined in these LDL-subfractions using standard laboratory techniques and high-pressure liquid chromatography mass-spectrometry analyses, respectively. At 3 months of diet, regular LDL of advanced-diseased pigs contained relatively more cholesterol (LDL-C; regular/larger LDL-C ratio 1.7 [1.3-1.9] versus 0.8 [0.6-0.9]; P=0.008) than mildly diseased pigs, while larger LDL contained more sphingosine-1-phosphate, ceramides, and sphingomyelins. Larger and regular LDL was also found in plasma of 3 patients with homozygous FH with varying LDL-C ratios.

CONCLUSIONS

In our adult FH pig model, inter-individual differences in atherosclerotic disease severity were directly related to the distribution of cholesterol and sphingolipids over a distinct LDL profile with regular and larger LDL shortly after the diet start. A similar LDL profile was detected in patients with homozygous FH.

miR-3646 promotes vascular inflammation and augments vascular smooth muscle cell proliferation and migration in progression of coronary artery disease by directly targeting RHOH

Coronary artery disease (CAD) is one of the leading causes of mortality and morbidity worldwide and the number of individuals at CAD risk is increasing. To better manage cardiovascular disease, improved tools for risk prediction including the identification of novel accurate biomarkers are needed. MicroRNAs (miRNAs) are small non-coding RNAs that modulate the expression of protein-coding genes at the post-transcription level and their dysregulated expression has been implicated in various pathogenic processes including cardiovascular disease. Circulating miRNAs have been widely recommended as potential biomarkers for many diseases including coronary artery disease. In the present study, we found that miR-3646 was significantly upregulated in the serum samples of CAD patients and in the mice with acute myocardial infarction (AMI) compared with the healthy control group via using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Moreover, the serum levels of miR-3646 were significantly positively correlated with the expression of IL-6 both in CAD patient samples and AMI mice samples. In human THP-1 macrophages, transfection with miR-3646 mimic elevated the expression of IL-6 while silence of miR-3646 suppressed the IL-6 level. Further exploration of the downstream targets of miR-3646 identified that blocking RHOH expression also could upregulate IL-6 expression. In addition, our findings also showed that miR-3646 promoted vascular smooth muscle cell (VSMC) proliferation and migration by targeting RHOH. These results demonstrate that the miR-3646-RHOH axis may serve as a key regulator in the progression of CAD by modulating vascular inflammation and regulating the biologic behaviors of VSMCs.