Perivascular Adipose Tissue: the Sixth Man of the Cardiovascular System

An Obligatory Role of Perivascular Adipose Tissue in Improved Saphenous Vein Graft Patency in Coronary Artery Bypass Grafting

The gold standard graft for coronary artery bypass grafting (CABG) is the internal thoracic artery (ITA), and the second recommendation is the radial artery. However, complete revascularization with arterial grafts alone is often difficult, and the saphenous vein (SV) is the most commonly used autologous graft for CABG, because it is easier to use without restriction for the length of the graft. On the other hand, the patency of SV grafts (SVGs) is poor compared with that of arterial grafts. The SVG is conventionally harvested as a distended conduit with surrounding tissue removed, a procedure that may cause vascular damage. A no-touch technique of SVG harvesting has been reported to result in improved long-term patency in CABG comparable to that when using the ITA for grafting. Possible reasons for the excellent long-term patency of no-touch SVGs are the physical support provided by preserved surrounding perivascular adipose tissue, preservation of the vascular wall structure including the vasa vasorum, and production of adipocyte-derived factors. In this review, we discuss recent strategies aimed at improving the performance of SVGs, including no-touch harvesting, minimally invasive harvesting and mechanical support using external stents.

Exercise attenuates high-fat diet-induced PVAT dysfunction through improved inflammatory response and BMP4-regulated adipose tissue browning

Background

Perivascular adipose tissue (PVAT) dysfunction impairs vascular homeostasis. Impaired inflammation and bone morphogenetic protein-4 (BMP4) signaling are involved in thoracic PVAT dysfunction by regulating adipokine secretion and adipocyte phenotype transformation. We investigated whether aerobic exercise training could ameliorate high-fat diet (HFD)-induced PVAT dysfunction via improved inflammatory response and BMP4-mediated signaling pathways.

Methods

Sprague-Dawley rats (n = 24) were divided into three groups, namely control, high-fat diet (HFD), and HFD plus exercise (HEx). After a 6-week intervention, PVAT functional efficiency and changes in inflammatory biomarkers (circulating concentrations in blood and mRNA expressions in thoracic PVAT) were assessed.

Results

Chronic HFD feeding caused obesity and dyslipidemia in rats. HFD decreased the relaxation response of PVAT-containing vascular rings and impaired PVAT-regulated vasodilatation. However, exercise training effectively reversed these diet-induced pathological changes to PVAT. This was accompanied by significantly (p < 0.05) restoring the morphological structure and the decreased lipid droplet size in PVAT. Furthermore, HFD-induced impaired inflammatory response (both in circulation and PVAT) was notably ameliorated by exercise training (p < 0.05). Specifically, exercise training substantially reversed HFD-induced WAT-like characteristics to BAT-like characteristics as evidenced by increased UCP1 and decreased FABP4 protein levels in PVAT against HFD. Exercise training promoted transcriptional activation of BMP4 and associated signaling molecules (p38/MAPK, ATF2, PGC1α, and Smad5) that are involved in browning of adipose tissue. In conjunction with gene expressions, exercise training increased BMP4 protein content and activated downstream cascades, represented by upregulated p38/MAPK and PGC1α proteins in PVAT.

Conclusion

Regular exercise training can reverse HFD-induced obesity, dyslipidemia, and thoracic PVAT dysfunction in rats. The browning of adipose tissue through exercise appears to be modulated through improved inflammatory response and/or BMP4-mediated signaling cascades in obese rats.

Perivascular fat tissue and vascular aging: A sword and a shield

The understanding of the function of perivascular adipose tissue (PVAT) in vascular aging has significantly changed due to the increasing amount of information regarding its biology. Adipose tissue surrounding blood vessels is increasingly recognized as a key regulator of vascular disorders. It has significant endocrine and paracrine effects on the vasculature and is mediated by the production of a variety of bioactive chemicals. It also participates in a number of pathological regulatory processes, including oxidative stress, immunological inflammation, lipid metabolism, vasoconstriction, and dilation. Mechanisms of homeostasis and interactions between cells at the local level tightly regulate the function and secretory repertoire of PVAT, which can become dysregulated during vascular aging. The PVAT secretion group changes from being reducing inflammation and lowering cholesterol to increasing inflammation and increasing cholesterol in response to systemic or local inflammation and insulin resistance. In addition, the interaction between the PVAT and the vasculature is reciprocal, and the biological processes of PVAT are directly influenced by the pertinent indicators of vascular aging. The architectural and biological traits of PVAT, the molecular mechanism of crosstalk between PVAT and vascular aging, and the clinical correlation of vascular age-related disorders are all summarized in this review. In addition, this paper aims to elucidate and evaluate the potential benefits of therapeutically targeting PVAT in the context of mitigating vascular aging. Furthermore, it will discuss the latest advancements in technology used for targeting PVAT.

Relationship Between Perivascular Adipose Tissue and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis

We conducted a systematic review and meta-analysis aimed at estimating the association between perivascular adipose tissue (PVAT) and some of the cardiovascular risk factors. A systematic search was conducted from January 1980 up to and including 2022 to identify studies that examined the relationship between PVAT and cardiovascular risk factors as obesity and its indices, hypertension, lipids, and glucose intolerance/diabetes. The Medline and Embase databases were searched using the PubMed and Scopus. Data were extracted from 23 studies that fit the criteria. To conduct meta-analysis, we used an approximation of equating the method of correlating assessment because different authors used either Pearson or Spearman correlation. Interrelations of PVAT and body mass index were analyzed in eight studies. Most studies revealed reliable direct correlation; the results of the meta-analysis also showed a significant (P = 0.37, P < 0.01, n = 12,346) correlation. PVAT and waist circumference were analyzed in six studies. Meta-analysis on the selected sample (n = 10,947) showed a significant (r = 0.45, P < 0.01) correlation. Relationship between PVAT and hypertension was revealed in three studies. Direct correlations were found in all studies. Meta-analysis showed the reliability of the correlation dependence (r = 0.21, P < 0.01, n = 3996). PVAT and blood glucose was evaluated in three studies (n = 3689). In each study a reliable (P < 0.05) direct correlation was obtained. Meta-analysis showed a significant correlation of weak strength (r = 0.24, P < 0.01). We demonstrated significant positive correlations of PVAT with the levels of total cholesterol (r = 0.05, P < 0.01), low-density lipoprotein cholesterol (r = 0.13, P < 0.01), and triglycerides (r = 0.29, P < 0.01), and a negative relationship with high-density lipoprotein cholesterol (r = -0.18, P < 0.01) in this meta-analysis. Despite some limitations, the findings of this systematic review and meta-analysis confirmed that PVAT significantly correlates with studied cardiovascular risk factors. Because PVAT presents a great interest in terms of cardiovascular remodeling and cardiovascular disease, its assessment in patients with and without cardiovascular pathology needs further research.

Sodium-Glucose Cotransporter Protein 2 Inhibitors: Novel Application for the Treatment of Obesity-Associated Hypertension

Obesity is becoming increasingly prevalent in China and worldwide and is closely related to the development of hypertension. The pathophysiology of obesity-associated hypertension is complex, including an overactive sympathetic nervous system (SNS), activation of the renin-angiotensin-aldosterone system (RAAS), insulin resistance, hyperleptinemia, renal dysfunction, inflammatory responses, and endothelial function, which complicates treatment. Sodium-glucose cotransporter protein 2 (SGLT-2) inhibitors, novel hypoglycemic agents, have been shown to reduce body weight and blood pressure and may serve as potential novel agents for the treatment of obesity-associated hypertension. This review discusses the beneficial mechanisms of SGLT-2 inhibitors for the treatment of obesity-associated hypertension. SGLT-2 inhibitors can inhibit SNS activity, reduce RAAS activation, ameliorate insulin resistance, reduce leptin secretion, improve renal function, and inhibit inflammatory responses. SGLT-2 inhibitors can, therefore, simultaneously target multiple mechanisms of obesity-associated hypertension and may serve as an effective treatment for obesity-associated hypertension.

The Role of Perivascular Adipose Tissue in the Pathogenesis of Endothelial Dysfunction in Cardiovascular Diseases and Type 2 Diabetes Mellitus

Cardiovascular diseases (CVDs) and type 2 diabetes mellitus (T2DM) are two of the four major chronic non-communicable diseases (NCDs) representing the leading cause of death worldwide. Several studies demonstrate that endothelial dysfunction (ED) plays a central role in the pathogenesis of these chronic diseases. Although it is well known that systemic chronic inflammation and oxidative stress are primarily involved in the development of ED, recent studies have shown that perivascular adipose tissue (PVAT) is implicated in its pathogenesis, also contributing to the progression of atherosclerosis and to insulin resistance (IR). In this review, we describe the relationship between PVAT and ED, and we also analyse the role of PVAT in the pathogenesis of CVDs and T2DM, further assessing its potential therapeutic target with the aim of restoring normal ED and reducing global cardiovascular risk.

AT1 receptors modulate ethanol-induced loss of anticontractile effect of perivascular adipose tissue

Ethanol consumption activates renin-angiotensin-aldosterone system (RAAS), which plays a major role in the pro-contractile and hypertensive effects linked to ethanol. We hypothesized that ethanol consumption induces loss of the anticontractile effect of perivascular adipose tissue (PVAT)through RAAS-mediated mechanisms. We examined the contribution of angiotensin II type 1 receptors (AT1R) to ethanol-induced PVAT dysfunction. With this purpose, male Wistar Hannover rats were treated with ethanol 20 % (in volume ratio) and/or losartan (antagonist of AT1R; 10 mg/kg/day, gavage) for 9 weeks. Losartan prevented the increase in blood pressure and the loss of the anticontractile effect of PVAT induced by ethanol consumption. PVAT dysfunction occurred after 3 and 9 weeks of treatment with ethanol in an endothelium-dependent manner. Blockade of AT1R prevented ethanol-induced reduction of adiponectin levels in PVAT from ethanol-treated rats. Functional assays revealed that ethanol impaired the anticontractile effect of PVAT-derived angiotensin (1-7) and endothelial nitric oxide (NO). In conclusion, AT1R are implicated in ethanol-induced loss of the anticontractile effect of PVAT. In PVAT, AT1R activation decreases the production of adiponectin, a PVAT-derived factor that promotes vasorelaxation in an endothelium-dependent manner. In the endothelium, AT1R favors the production of superoxide (O2•-) leading to a reduction in NO bioavailability. These responses impair the vasodilator action induced by PVAT-derived angiotensin (1-7), which occurs via Mas receptors located in endothelial cells. Ethanol-induced PVAT dysfunction favors vascular hypercontractility, a response that could contribute to the hypertensive state associated with ethanol consumption.

Perivascular Adipose Tissue and Vascular Smooth Muscle Tone: Friends or Foes?

Perivascular adipose tissue (PVAT) is a specialized type of adipose tissue that surrounds most mammalian blood vessels. PVAT is a metabolically active, endocrine organ capable of regulating blood vessel tone, endothelium function, vascular smooth muscle cell growth and proliferation, and contributing critically to cardiovascular disease onset and progression. In the context of vascular tone regulation, under physiological conditions, PVAT exerts a potent anticontractile effect by releasing a plethora of vasoactive substances, including NO, H₂S, H₂O₂, prostacyclin, palmitic acid methyl ester, angiotensin 1-7, adiponectin, leptin, and omentin. However, under certain pathophysiological conditions, PVAT exerts pro-contractile effects by decreasing the production of anticontractile and increasing that of pro-contractile factors, including superoxide anion, angiotensin II, catecholamines, prostaglandins, chemerin, resistin, and visfatin. The present review discusses the regulatory effect of PVAT on vascular tone and the factors involved. In this scenario, dissecting the precise role of PVAT is a prerequisite to the development of PVAT-targeted therapies.

Pericoronary adipose tissue differences among plaque types: a retrospective assessment

PURPOSE

To assess differences in pericoronary adipose tissue (PCAT) in patients with different plaque types by using several quantitative parameters of PCAT and investigate the relationship between PCAT and different plaque types.

MATERIALS AND METHODS

We retrospectively recruited 488 patients diagnosed with stable coronary artery disease (CAD) via coronary computed tomographic angiography, including 279 with calcified plaques (CP), 153 with non-calcified plaques (NCP), and 56 with mixed plaques (MP). Volume, fat attenuation index (FAI), and 10^th percentile, 90^th percentile, median, and minimum Hounsfield unit (HU) values of PCAT surrounding plaques were quantified. Clinical features and quantitative PCAT parameters were compared between different plaque types.

RESULTS

No intergroup differences were observed for age, sex, body mass index, risk factors, and plaque location. Length and PCAT volume in the NCP group were lower than those of the CP and MP groups (P < 0.001), whereas there were no significant differences between the CP and MP groups (P > 0.05). Patients with NCP and MP had a higher FAI and 10^th percentile, 90^th percentile, median, and minimum HU values of PCAT than CP (P < 0.001); however these values were not significantly different between the NCP and MP groups (P > 0.05).

CONCLUSION

The quantitative parameters of PCAT, as a biosensor for CAD, vary among the different plaque types.

Perivascular adipose tissue: Fine-tuner of vascular redox status and inflammation

Perivascular adipose tissue (PVAT) refers to the aggregate of adipose tissue surrounding the vasculature, exhibiting the phenotypes of white, beige and brown adipocytes. PVAT has emerged as an active modulator of vascular homeostasis and pathogenesis of cardiovascular diseases in addition to its structural role to provide mechanical support to blood vessels. More specifically, PVAT is closely involved in the regulation of reactive oxygen species (ROS) homeostasis and inflammation along the vascular tree, through the tight interaction between PVAT and cellular components of the vascular wall. Furthermore, the phenotype-genotype of PVAT at different regions of vasculature varies corresponding to different cardiovascular risks. During ageing and obesity, the cellular proportions and signaling pathways of PVAT vary in favor of cardiovascular pathogenesis by promoting ROS generation and inflammation. Physiological means and drugs that alter PVAT mass, components and signaling may provide new therapeutic insights in the treatment of cardiovascular diseases. In this review, we aim to provide an updated understanding towards PVAT in the context of redox regulation, and to highlight the therapeutic potential of targeting PVAT against cardiovascular complications.

miRNA-22 is involved in the aortic reactivity in physiological conditions and mediates obesity-induced perivascular adipose tissue dysfunction

AIMS

Blood vessels are surrounded by perivascular adipose tissue (PVAT), which plays an important role in vascular tonus regulation due to its anticontractile effect; however, this effect is impaired in obesity. We previously demonstrated that miRNA-22 is involved in obesity-related metabolic disorders. However, the impact of miRNA-22 on vascular reactivity and PVAT function is unknown.

AIM

To investigate the role of miRNA-22 on vascular reactivity and its impact on obesity-induced PVAT dysfunction.

MAIN METHODS

Wild-type and miRNA-22 knockout (KO) mice were fed a control or a high-fat (HF) diet. To characterize the vascular response, concentration-responses curves to noradrenaline were performed in PVAT- or PVAT+ thoracic aortic rings in absence and presence of L-NAME. Expression of adipogenic and thermogenic markers and NOS isoforms were evaluated by western blotting or qPCR.

KEY FINDINGS

HF diet and miRNA-22 deletion reduced noradrenaline-induced contraction in PVAT- aortic rings. Additionally, miRNA-22 deletion increased noradrenaline-induced contraction in PVAT+ aortic rings without affecting its sensitivity; however, this effect was not observed in miRNA-22 KO mice fed a HF diet. Interestingly, miRNA-22 deletion reduced the contraction of aortic rings to noradrenaline via a NOS-dependent mechanism. Moreover, HF diet abolished the NOS-mediated anticontractile effect of PVAT, which was attenuated by miRNA-22 deletion. Mechanistically, we found that PVAT from miRNA-22 KO mice fed a HF diet presented increased protein expression of nNOS.

SIGNIFICANCE

These results suggest that miRNA-22 is important for aorta reactivity under physiological circumstances and its deletion attenuates the loss of the NOS-mediated anticontractile effect of PVAT in obesity.

RNA sequencing reveals perivascular adipose tissue plasticity in response to angiotensin II

Most blood vessels are surrounded by perivascular adipose tissue (PVAT), which is a unique adipose tissue that plays critical roles in vascular physiology and pathophysiology. PVAT displays regional differences that impact vascular homeostasis. Angiotensin II (Ang II) is the main biologically active component of the renin-angiotensin-aldosterone system (RAAS), which has been extensively studied in vascular biology. However, the effects of Ang II on PVAT are less explored and remain to be elucidated. In this study, we systematically investigated the regional heterogeneity of three portions of aortic PVAT, i.e., ascending thoracic aortic PVAT (ATA-PVAT), descending thoracic aortic PVAT (DTA-PVAT) and abdominal aortic PVAT (AA-PVAT), and their responses to 7-day Ang II infusion using RNA sequencing. We found that AA-PVAT is clearly distinguished from both ATA-PVAT and DTA-PVAT, with significantly down-regulated oxidative phosphorylation and up-regulated inflammatory response pathways. Furthermore, AA-PVAT expresses lower levels of brown adipocyte marker genes, such as Ucp1, Cidea, Cox8b, Dio2 and Pgc1α, but expresses higher levels of proinflammatory genes, such as Ccl2, Il1β and Tnfα, and components of the RAAS, including Agt, Ace and Agtr1a. Ang II infusion significantly down-regulated oxidative phosphorylation in all regions of aortic PVAT and significantly up-regulated inflammatory response specifically in ATA-PVAT and DTA-PVAT. Moreover, ATA-PVAT was most responsive to Ang II induced inflammation. We further used CDGSH iron-sulfur domain-containing protein 1 (a.k.a. mitoNEET) transgenic mice that exhibit enhanced brown adipose tissue (BAT)-like phenotype in aortic PVAT, as indicated by elevated expression levels of brown adipocyte marker genes, and found that the enhanced BAT-like phenotype of aortic PVAT could counterbalance Ang II induced inflammatory and oxidative effects.

Ectopic Fat Depots: Physiological Role And Impact On Cardiovascular Disease Continuum

Obesity is a non-infectious pandemic. The visceral distribution of adipose tissue is a significant factor in the development of cardiovascular diseases and their complications. Along with the visceral abdominal depot in omentum and subcutaneous tissue, there are other ectopic adipose tissue depots: epicardial adipose tissue (EAT), perivascular adipose tissue (PVAT) and perirenal adipose tissue. This article presents a review of the physiological role and molecular basis of the PVAT and EAT function in healthy, as well as in pathological, conditions; the interaction of adipokines and cytokines, their contribution to the development and progression of cardiovascular diseases. The review discusses well-known facts and controversial issues in this field. Comprehensive investigation of the mechanisms of vascular and myocardial pathology in obese people, along with identification of biomarkers for early prediction of cardiovascular complications, would contribute to the development of targeted preventive measures and choice of therapeutic strategies, which is consistent with the contemporary concept of personalized medicine. We have analyzed domestic and foreign literature sources in eLIBRARY and PubMed scientific libraries for the period of 2001-2020.

Maternal Obesity Programming of Perivascular Adipose Tissue and Associated Immune Cells: An Understudied Area With Few Answers and Many Questions

At present, the worldwide prevalence of obesity has become alarmingly high with estimates foreshadowing a continued escalation in the future. Furthermore, there is growing evidence attributing an individual’s predisposition for developing obesity to maternal health during gestation. Currently, 60% of pregnancies in the US are to either overweight or obese mothers which in turn contributes to the persistent rise in obesity rates. While obesity itself is problematic, it conveys an increased risk for several diseases such as diabetes, inflammatory disorders, cancer and cardiovascular disease (CVD). Additionally, as we are learning more about the mechanisms underlying CVD, much attention has been brought to the role of perivascular adipose tissue (PVAT) in maintaining cardiovascular health. PVAT regulates vascular tone and for a significant number of individuals, obesity elicits PVAT disruption and dysregulation of vascular function. Obesity elicits changes in adipocyte and leukocyte populations within PVAT leading to an inflammatory state which promotes vasoconstriction thereby aiding the onset/progression of CVD. Our current understanding of obesity, PVAT and CVD has only been examined at the individual level without consideration for a maternal programming effect. It is unknown if maternal obesity affects the propensity for PVAT remodeling in the offspring, thereby enhancing the obesity/CVD link, and what role PVAT leukocytes play in this process. This perspective will focus on the maternal contribution of the interplay between obesity, PVAT disruption and CVD and will highlight the leukocyte/PVAT interaction as a novel target to stem the tide of the current obesity epidemic and its secondary health consequences.

Urban fine particulate air pollution exposure promotes atherosclerosis in apolipoprotein E-deficient mice by activating perivascular adipose tissue inflammation via the Wnt5a/Ror2 signaling pathway

Urban fine particulate matter (PM_2.5) is a deleterious risk factor in the ambient air and is recognized to exacerbate atherosclerosis. Perivascular adipose tissue (PVAT) secretes a large number of inflammatory cytokines and plays a crucial role in the pathogenic microenvironment of atherogenesis. However, there is a lack of knowledge about the role of PVAT inflammation in the genesis of PM_2.5-related atherosclerosis. The aim of this research was to probe the latent links between PM_2.5 exposure and PVAT inflammation and further discovered the underlying mechanisms of PM_2.5-triggered atherosclerosis pathogenesis. Apolipoprotein E-deficient (ApoE^-/-) mice were exposed to real-world atmospheric PM_2.5 or filtered clean air for three months, the Wnt5a inhibitor Box5 and the Ror2 inhibitor β-Arrestin2 were applied to verify the possible mechanisms. We noticed that the average daily PM_2.5 mass concentration was 84.27 ± 28.84 μg/m³. PM_2.5 inhalation might significantly expedite the deterioration of atherosclerosis, increase the protein and mRNA expressions of MCP-1, IL-6, TNF-α, Wnt5a, and Ror2 in PVAT tissues, upregulate the distributions of IL-6, TNF-α, MCP-1, and leptin in the histological sections of PVAT, promote lipid deposition in the aorta, elevate the plasma levels of leptin, MCP-1, IL-6, TNF-α, LDL-C, TC, and TG, however, decrease the plasma levels of adiponectin and HDL-C, downregulate the distribution of adiponectin. Nevertheless, these effects caused by PM_2.5 exposure were dramatically diminished after the administration of Box5 or β-Arrestin2. This research illuminated that PVAT inflammation was involved in the PM_2.5-induced atherosclerosis process, as well as lipid deposition, which was closely associated with the activation of the Wnt5a/Ror2 signaling pathway.

Physiological Changes and Pathological Pain Associated with Sedentary Lifestyle-Induced Body Systems Fat Accumulation and Their Modulation by Physical Exercise

A sedentary lifestyle is associated with overweight/obesity, which involves excessive fat body accumulation, triggering structural and functional changes in tissues, organs, and body systems. Research shows that this fat accumulation is responsible for several comorbidities, including cardiovascular, gastrointestinal, and metabolic dysfunctions, as well as pathological pain behaviors. These health concerns are related to the crosstalk between adipose tissue and body systems, leading to pathophysiological changes to the latter. To deal with these health issues, it has been suggested that physical exercise may reverse part of these obesity-related pathologies by modulating the cross talk between the adipose tissue and body systems. In this context, this review was carried out to provide knowledge about (i) the structural and functional changes in tissues, organs, and body systems from accumulation of fat in obesity, emphasizing the crosstalk between fat and body tissues; (ii) the crosstalk between fat and body tissues triggering pain; and (iii) the effects of physical exercise on body tissues and organs in obese and non-obese subjects, and their impact on pathological pain. This information may help one to better understand this crosstalk and the factors involved, and it could be useful in designing more specific training interventions (according to the nature of the comorbidity).

Comparative Proteomic Analysis of tPVAT during Ang II Infusion

Perivascular adipose tissue (PVAT) homeostasis plays an important role in maintaining vascular function, and PVAT dysfunction may induce several pathophysiological situations. In this study, we investigated the effect and mechanism of the local angiotensin II (Ang II) on PVAT. High-throughput comparative proteomic analysis, based on TMT labeling combined with LC-MS/MS, were performed on an in vivo Ang II infusion mice model to obtain a comprehensive view of the protein ensembles associated with thoracic PVAT (tPVAT) dysfunction induced by Ang II. In total, 5037 proteins were confidently identified, of which 4984 proteins were quantified. Compared with the saline group, 145 proteins were upregulated and 146 proteins were downregulated during Ang II-induced tPVAT pathogenesis. Bioinformatics analyses revealed that the most enriched GO terms were annotated as gene silencing, monosaccharide binding, and extracellular matrix. In addition, some novel proteins, potentially associated with Ang II infusion, were identified, such as acyl-CoA carboxylase α, very long-chain acyl-CoA synthetase (ACSVL), uncoupling protein 1 (UCP1), perilipin, RAS protein-specific guanine nucleotide-releasing factor 2 (RasGRF2), and hypoxia inducible factor 1α (HIF-1α). Ang II could directly participate in the regulation of lipid metabolism, transportation, and adipocyte differentiation by affecting UCP1 and perilipin. Importantly, the key KEGG pathways were involved in fatty acid biosynthesis, FABP3-PPARα/γ, RasGRF2-ERK-HIF-1α, RasGRF2-PKC-HIF-1α, and STAT3-HIF-1α axis. The present study provided the most comprehensive proteome profile of mice tPVAT and some novel insights into Ang II-mediated tPVAT dysfunction and will be helpful for understanding the possible relationship between local RAS activation and PVAT dysfunction.

Perivascular Adipose Tissue in Vascular Function: Does Locally Synthesized Angiotensinogen Play a Role?

ABSTRACT

In recent years, perivascular adipose tissue (PVAT) research has gained special attention in an effort to understand its involvement in vascular function. PVAT is recognized as an important endocrine organ that secretes procontractile and anticontractile factors, including components of the renin-angiotensin-aldosterone system, particularly angiotensinogen (AGT). This review critically addresses the occurrence of AGT in PVAT, its release into the blood stream, and its contribution to the generation and effects of angiotensins (notably angiotensin-(1-7) and angiotensin II) in the vascular wall. It describes that the introduction of transgenic animals, expressing AGT at 0, 1, or more specific location(s), combined with the careful measurement of angiotensins, has revealed that the assumption that PVAT independently generates angiotensins from locally synthesized AGT is incorrect. Indeed, selective deletion of AGT from adipocytes did not lower circulating AGT, neither under a control diet nor under a high-fat diet, and only liver-specific AGT deletion resulted in the disappearance of AGT from blood plasma and adipose tissue. An entirely novel scenario therefore develops, supporting local angiotensin generation in PVAT that depends on the uptake of both AGT and renin from blood, in addition to the possibility that circulating angiotensins exert vascular effects. The review ends with a summary of where we stand now and recommendations for future research.

The Role of Obesity-Induced Perivascular Adipose Tissue (PVAT) Dysfunction in Vascular Homeostasis

Perivascular adipose tissue (PVAT) is an additional special type of adipose tissue surrounding blood vessels. Under physiological conditions, PVAT plays a significant role in regulation of vascular tone, intravascular thermoregulation, and vascular smooth muscle cell (VSMC) proliferation. PVAT is responsible for releasing adipocytes-derived relaxing factors (ADRF) and perivascular-derived relaxing factors (PDRF), which have anticontractile properties. Obesity induces increased oxidative stress, an inflammatory state, and hypoxia, which contribute to PVAT dysfunction. The exact mechanism of vascular dysfunction in obesity is still not well clarified; however, there are some pathways such as renin-angiotensin-aldosterone system (RAAS) disorders and PVAT-derived factor dysregulation, which are involved in hypertension and endothelial dysfunction development. Physical activity has a beneficial effect on PVAT function among obese patients by reducing the oxidative stress and inflammatory state. Diet, which is the second most beneficial non-invasive strategy in obesity treatment, may have a positive impact on PVAT-derived factors and may restore the balance in their concentration.

Expression of Melatonin Receptor 1 in Rat Mesenteric Artery and Perivascular Adipose Tissue and Vasoactive Action of Melatonin

Melatonin is released by the pineal gland and can modulate cardiovascular system function via the G protein-coupled melatonin receptors MT1 and MT2. Most vessels are surrounded by perivascular adipose tissue (PVAT), which affects their contractility. The aim of our study was to evaluate mRNA and protein expression of MT1 and MT2 in the mesenteric artery (MA) and associated PVAT of male rats by RT-PCR and Western blot. Receptor localization was further studied by immunofluorescence microscopy. Effects of melatonin on neurogenic contractions were explored in isolated superior MA ex vivo by measurement of isometric contractile tension. MT1, but not MT2, was present in MA, and MT1 was localized mainly in vascular smooth muscle. Moreover, we proved the presence of MT1, but not MT2 receptors, in MA-associated PVAT. In isolated superior MA with intact PVAT, neuro-adrenergic contractile responses were significantly smaller when compared to arteries with removed PVAT. Pre-treatment with melatonin of PVAT-stripped arterial rings enhanced neurogenic contractions, while the potentiating effect of melatonin was not detected in preparations with preserved PVAT. We hypothesize that melatonin can stimulate the release of PVAT-derived relaxing factor(s) via MT1, which can override the direct pro-contractile effect of melatonin on vascular smooth muscle. Our results suggest that melatonin is involved in the control of vascular tone in a complex way, which is vessel specific and can reflect a sum of action on different layers of the vessel wall and surrounding PVAT.

A GLP-1 analog lowers ER stress and enhances protein folding to ameliorate homocysteine-induced endothelial dysfunction

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases and increases mortality in type 2 diabetic patients. HHcy induces endoplasmic reticulum (ER) stress and oxidative stress to impair endothelial function. The glucagon-like peptide 1 (GLP-1) analog exendin-4 attenuates endothelial ER stress, but the detailed vasoprotective mechanism remains elusive. The present study investigated the beneficial effects of exendin-4 against HHcy-induced endothelial dysfunction. Exendin-4 pretreatment reversed homocysteine-induced impairment of endothelium-dependent relaxations in C57BL/6 mouse aortae ex vivo. Four weeks subcutaneous injection of exendin-4 restored the impaired endothelial function in both aortae and mesenteric arteries isolated from mice with diet-induced HHcy. Exendin-4 treatment lowered superoxide anion accumulation in the mouse aortae both ex vivo and in vivo. Exendin-4 decreased the expression of ER stress markers (e.g., ATF4, spliced XBP1, and phosphorylated eIF2α) in human umbilical vein endothelial cells (HUVECs), and this change was reversed by cotreatment with compound C (CC) (AMPK inhibitor). Exendin-4 induced phosphorylation of AMPK and endothelial nitric oxide synthase in HUVECs and arteries. Exendin-4 increased the expression of endoplasmic reticulum oxidoreductase (ERO1α), an important ER chaperone in endothelial cells, and this effect was mediated by AMPK activation. Experiments using siRNA-mediated knockdown or adenoviral overexpression revealed that ERO1α mediated the inhibitory effects of exendin-4 on ER stress and superoxide anion production, thus ameliorating HHcy-induced endothelial dysfunction. The present results demonstrate that exendin-4 reduces HHcy-induced ER stress and improves endothelial function through AMPK-dependent ERO1α upregulation in endothelial cells and arteries. AMPK activation promotes the protein folding machinery in endothelial cells to suppress ER stress.

The physiologic and physiopathologic roles of perivascular adipose tissue and its interactions with blood vessels and the renin-angiotensin system

The perivascular adipose tissue (PVAT) refers to an ectopic local deposit of connective tissue that anatomically surrounds most of the blood vessels. While it was initially known only as a structural support for vasculature, the landmark findings of Soltis and Cassis (1991), first demonstrating that PVAT reduces the contractions of norepinephrine in the isolated rat aorta, brought the potential vascular role of PVAT into the limelight. This seminal work implied the potential ability of PVAT to influence vascular responsiveness. Several vasoactive/vasocrine substances influencing vascular homeostasis were successively shown to be released from PVAT that include both adipocyte-derived relaxing and contracting factors. The PVAT is currently recognized as a metabolically active endocrine organ and is eventually considered as the 'protagonist' in vascular homeostasis. It plays prominent defending and opposing roles in vascular function, while the actual vascular influences of PVAT vary with an increase in adiposity. Recent studies have presented compelling evidence implicating the pivotal role of PVAT in the local activation of the renin-angiotensin system (RAS), which substantially impacts vascular physiology and physiopathology. Current findings have advanced our understanding of the role of PVAT in favorably or adversely modulating the vascular function through differential RAS activation. Given that adipocytes also produce major RAS components locally to influence vascular function, this review provides a scientific basis to distinctly understand the key role of PVAT in regulating the autocrine and paracrine functions of vascular RAS components and its potential as an emerging therapeutic target for mitigating cardiovascular complications.

RNF213 and GUCY1A3 in Moyamoya Disease: Key Regulators of Metabolism, Inflammation, and Vascular Stability

Moyamoya disease is an idiopathic chronically progressive cerebrovascular disease, which causes both ischemic and hemorrhagic stroke. Genetic studies identified RNF213/Mysterin and GUCY1A3 as disease-causing genes. They were also known to be associated with non-moyamoya intracranial large artery disease, coronary artery disease and pulmonary artery hypertension. This review focused on these two molecules and their strong linker, calcineurin/NFAT signaling and caveolin to understand the pathophysiology of moyamoya disease and related vascular diseases. They are important regulators of lipid metabolism especially lipotoxicity, NF-κB mediated inflammation, and nitric oxide-mediated vascular protection. Although intimal thickening with fibrosis and damaged vascular smooth muscle cells are the distinguishing features of moyamoya disease, origin of the fibrous tissue and the mechanism of smooth muscle cell damages remains not fully elucidated. Endothelial cells and smooth muscle cells have long been a focus of interest, but other vascular components such as immune cells and extracellular matrix also need to be investigated in future studies. Molecular research on moyamoya disease would give us a clue to understand the mechanism preserving vascular stability.

Role of Perivascular Adipose Tissue and Exercise on Arterial Function with Obesity

Adipose tissue and arterial dysfunction are common in the obese state. Perivascular adipose tissue (PVAT) plays an important role in mediating arterial health, and with obesity, the PVAT dysfunction negatively affects arterial health. Exercise training exerts direct and beneficial effects on PVAT, providing an additional and novel pathway by which exercise can improve arterial health in diseased populations.

Mineralocorticoid Receptor in Myeloid Cells Mediates Angiotensin II-Induced Vascular Dysfunction in Female Mice

Enhanced mineralocorticoid receptor (MR) signaling is critical to the development of endothelial dysfunction and arterial stiffening. However, there is a lack of knowledge about the role of MR-induced adipose tissue inflammation in the genesis of vascular dysfunction in women. In this study, we hypothesize that MR activation in myeloid cells contributes to angiotensin II (Ang II)-induced aortic stiffening and endothelial dysfunction in females via increased pro-inflammatory (M1) macrophage polarization. Female mice lacking MR in myeloid cells (MyMRKO) were infused with Ang II (500 ng/kg/min) for 4 weeks. This was followed by determinations of aortic stiffness and vasomotor responses, as well as measurements of markers of inflammation and macrophage infiltration/polarization in different adipose tissue compartments. MyMRKO mice were protected against Ang II-induced aortic endothelial stiffening, as assessed via atomic force microscopy in aortic explants, and vasorelaxation dysfunction, as measured by aortic wire myography. In alignment, MyMRKO mice were protected against Ang II-induced macrophage infiltration and M1 polarization in visceral adipose tissue (VAT) and thoracic perivascular adipose tissue (tPVAT). Collectively, this study demonstrates a critical role of MR activation in myeloid cells in the pathogenesis of vascular dysfunction in females associated with pro-inflammatory macrophage polarization in VAT and tPVAT. Our data have potential clinical implications for the prevention and management of cardiovascular disease in women, who are disproportionally at higher risk for poor outcomes.

SIRT3 (Sirtuin-3) Prevents Ang II (Angiotensin II)-Induced Macrophage Metabolic Switch Improving Perivascular Adipose Tissue Function

OBJECTIVE

Infiltrated macrophages actively promote perivascular adipose tissue remodeling and represent a dominant population in the perivascular adipose tissue microenvironment of hypertensive mice. However, the role of macrophages in initiating metabolic inflammation remains uncertain. SIRT3 (sirtuin-3), a NAD-dependent deacetylase, is sensitive to metabolic status and mediates adaptation responses. In this study, we investigated the role of SIRT3-mediated metabolic shift in regulating NLRP3 (Nod-like receptor family pyrin domain-containing 3) inflammasome activation. Approach and Results: Here, we report that Ang II (angiotensin II) accelerates perivascular adipose tissue inflammation and fibrosis, accompanied by NLRP3 inflammasome activation and IL (interleukin)-1β secretion in myeloid SIRT3 knockout (SIRT3-/-) mice. This effect is associated with adipose tissue mitochondrial dysfunction. In vitro studies indicate that the deletion of SIRT3 in bone marrow-derived macrophages induces IL-1β production by shifting the metabolic phenotype from oxidative phosphorylation to glycolysis. Mechanistically, SIRT3 deacetylates and activates PDHA1 (pyruvate dehydrogenase E1 alpha) at lysine 83, and the loss of SIRT3 leads to PDH activity decrease and lactate accumulation. Knocking down LDHA (lactate dehydrogenase A) or using carnosine, a buffer against lactic acid, attenuates IL-1β secretion. Furthermore, the blockade of IL-1β from macrophages into brown adipocytes restores thermogenic markers and mitochondrial oxygen consumption. Moreover, NLRP3 knockout (NLRP3-/-) mice exhibited reduced IL-1β production while rescuing the mitochondrial function of brown adipocytes and alleviating perivascular adipose tissue fibrosis.

CONCLUSIONS

SIRT3 represents a potential therapeutic target to attenuate NLRP3-related inflammation. Pharmacological targeting of glycolytic metabolism may represent an effective therapeutic approach.

Blood pressure changes PVAT function and transcriptome: use of the mid-thoracic aorta coarcted rat

Perivascular adipose tissue (PVAT) modifies the contractile function of the vessel it surrounds (outside-in signaling). Little work points to the vessel actively affecting its surrounding PVAT. We hypothesized that inside-out arterial signaling to PVAT would be evidenced by the response of PVAT to changes in tangential vascular wall stress. Rats coarcted in the mid-thoracic aorta created PVAT tissues that would exemplify pressure-dependent changes (above vs. below coarctation); a sham rat was used as a control. Radiotelemetry revealed a ∼20 mmHg systolic pressure gradient across the coarctation 4 wk after surgery. Four measures (histochemical, adipocyte progenitor proliferation and differentiation, isometric tone, and bulk mRNA sequencing) were used to compare PVAT above versus below the ligature in sham and coarcted rats. Neither aortic collagen deposition in PVAT nor arterial media/radius ratio above coarctation was increased versus below segments. However, differentiated adipocytes derived from PVAT above the coarctation accumulated substantially less triglycerides versus those below; their relative proliferation rate as adipogenic precursors was not different. Functionally, the ability of PVAT to assist stress relaxation of isolated aorta was reduced in rings above versus below the coarctation. Transcriptomic analyses revealed that the coarctation resulted in more differentially expressed genes (DEGs) between PVAT above versus below when compared with sham samples from the same locations. A majority of DEGs were in PVAT below the coarctation and were enriched in neuronal/synaptic terms. These findings provide initial evidence that signaling from the vascular wall, as stimulated by a pressure change, influences the function and transcriptional profile of its PVAT.NEW & NOTEWORTHY A mid-thoracic aorta coarcted rat was created to generate a stable pressure difference above versus below the coarctation ligature. This study determined that the PVAT around the thoracic aorta exposed to a higher pressure has a significantly reduced ability to assist stress relaxation versus that below the ligature and appears to retain the ability to be anticontractile. At the same time, the PVAT around the thoracic aorta exposed to higher pressure had a reduced adipogenic potential versus that below the ligature. Transcriptomics analyses indicated that PVAT below the coarctation showed the greatest number of DEGs with an increased profile of the synaptic neurotransmitter gene network.

Inflammatory cells in perivascular adipose tissue and the integrity of the tunica media in atherosclerotic coronary arteries

Obstructive coronary artery disease (CAD) is characterized by inflammation within the atherosclerotic coronary arteries. Infiltration of inflammatory cells into muscular media can lead to remodeling and weakening of the arterial wall. We examined the relationship between inflammatory infiltration in perivascular adipose tissue (PVAT), state of the external elastic membrane, and the intensity of inflammatory infiltration in the tunica media of coronary arteries obtained by endarterectomy from symptomatic patients with diffuse CAD. We analyzed endarterectomy sequesters from 22 coronary arteries that contained the intima, media, a part of the adventitia, and PVAT in at least one part of the sequester. The coronary arteries were divided into two groups according to the presence or absence of inflammatory infiltration in PVAT. Staining with hematoxylin-eosin and by the Movat's method showed atherosclerotic changes in the intima and media. Immunohistochemistry (anti-leukocyte common antigen [LCA] antibody) was used for the detection of leukocytes. We found a significant positive correlation between inflammatory infiltration in PVAT and preservation of the external elastic membrane of coronary arteries. Furthermore, we found a significant negative correlation between inflammatory infiltration in PVAT and the intensity of inflammatory infiltration in the media. It seems that the integrity of the external elastic membrane and the proinflammatory properties of PVAT restrain inflammatory cells within PVAT. Both effects may prevent the migration of inflammatory cells into the media and delay the development of CAD.

PVAT: an important guardian of the cardiovascular system

Perivascular adipose tissue (PVAT) had long been considered to serve only structural, vessel-supporting purposes, but today PVAT is recognized to be an endocrine organ with important physiological and pathological effects. The expansion of PVAT in vascular homeostasis and vascular disease has attracted much interest. PVAT has been shown to release a wide spectrum of molecules, such as PVAT-derived relaxing factors (PVATRFs) and PVAT-derived contracting factors (PVATCFs). PVAT dysfunction may lead to obesity, atherosclerosis, and other cardiovascular diseases. This review describes recent advances in our understanding of PVAT's important effects on the cardiovascular system.

A New Function for Perivascular Adipose Tissue (PVAT): Assistance of Arterial Stress Relaxation

In health, PVAT secretes anti-contractile factors that relax the underlying artery. PVAT’s contributions to vascular function include more than production of vasoactive substances. We hypothesized that PVAT benefits the artery by assisting the function of stress (–induced) relaxation. Thoracic aorta rings from Sprague Dawley rats were mounted in isolated tissue baths with (+) and without (−) PVAT. A cumulative length tension (0–6 grams) was generated. The tension to which the tissue stress relaxed over 30 minutes was recorded; the tension lost was stress relaxation. The presence of PVAT increased the amount of stress relaxation (final tension in mgs; aortic ring −PVAT = 4578 ± 190; aortic ring + PVAT = 2730 ± 274, p < 0.05). PVAT left attached but not encompassing the aorta provided no benefit in cumulative stress relaxation (aortic ring +/− PVAT = 4122 ± 176; p > 0.05 vs −PVAT). A PVAT ring separated from the aorta demonstrated more profound stress relaxation than did the aortic ring itself. Finally, PVAT-assisted stress relaxation was observed in an artery with white fat (superior mesenteric artery) and in aorta from both male and female of another rat strain, the Dahl S rat. Knowledge of this new PVAT function supports PVAT as an essential player in vascular health.

Specific Biological Features of Adipose Tissue, and Their Impact on HIV Persistence

Although white AT can contribute to anti-infectious immune responses, it can also be targeted and perturbed by pathogens. The AT's immune involvement is primarily due to strong pro-inflammatory responses (with both local and paracrine effects), and the large number of fat-resident macrophages. Adipocytes also exert direct antimicrobial responses. In recent years, it has been found that memory T cells accumulate in AT, where they provide efficient secondary responses against viral pathogens. These observations have prompted researchers to re-evaluate the links between obesity and susceptibility to infections. In contrast, AT serves as a reservoir for several persistence pathogens, such as human adenovirus Ad-36, Trypanosoma gondii, Mycobacterium tuberculosis, influenza A virus, and cytomegalovirus (CMV). The presence and persistence of bacterial DNA in AT has led to the concept of a tissue-specific microbiota. The unexpected coexistence of immune cells and pathogens within the specific AT environment is intriguing, and its impact on anti-infectious immune responses requires further evaluation. AT has been recently identified as a site of HIV persistence. In the context of HIV infection, AT is targeted by both the virus and the antiretroviral drugs. AT's intrinsic metabolic features, large overall mass, and wide distribution make it a major tissue reservoir, and one that may contribute to the pathophysiology of chronic HIV infections. Here, we review the immune, metabolic, viral, and pharmacological aspects that contribute to HIV persistence in AT. We also evaluate the respective impacts of both intrinsic and HIV-induced factors on AT's involvement as a viral reservoir. Lastly, we examine the potential consequences of HIV persistence on the metabolic and immune activities of AT.

Pharmacological basis and new insights of resveratrol action in the cardiovascular system

Resveratrol (trans-3,4',5-trihydroxystilbene) belongs to the family of natural phytoalexins. Resveratrol first came to our attention in 1992, following reports of the cardioprotective effects of red wine. Thereafter, resveratrol was shown to exert antioxidant, anti-inflammatory, anti-proliferative, and angio-regulatory effects against atherosclerosis, ischaemia, and cardiomyopathy. This article critically reviews the current findings on the molecular basis of resveratrol-mediated cardiovascular benefits, summarizing the broad effects of resveratrol on longevity regulation, energy metabolism, stress resistance, exercise mimetics, circadian clock, and microbiota composition. In addition, this article also provides an update, both preclinically and clinically, on resveratrol-induced cardiovascular protection and discusses the adverse and inconsistent effects of resveratrol reported in both preclinical and clinical studies. Although resveratrol has been claimed as a master anti-aging agent against several age-associated diseases, further detailed mechanistic investigation is still required to thoroughly unravel the therapeutic value of resveratrol against cardiovascular diseases at different stages of disease development. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Liraglutide improves vascular dysfunction by regulating a cAMP-independent PKA-AMPK pathway in perivascular adipose tissue in obese mice

BACKGROUND

Perivascular adipose tissue (PVAT) attenuates its anti-contractile effect through an endothelial-dependent mechanism that aggravates endothelial dysfunction in obesity. The present study was conducted to explore whether liraglutide could improve vascular dysfunction, including the anti-contractile effect of PVAT and endothelial function, by modulating PVAT-related signaling pathways in obesity.

METHODS

C57BL/6 mice were fed a normal-chow diet or a high-fat diet (HFD) with or without liraglutide treatment. Vascular function of the thoracic aorta with or without PVAT were measured. Protein levels of components of the PKA-AMPK-PGC1α and antioxidant signaling pathway in PVAT were determined by western blotting. Brown adipose tissue-related gene in PVAT was measured by qRT-PCR.

RESULTS

Metabolic profiles of HFD-fed mice were improved after treatment with liraglutide. Liraglutide improved PVAT-induced anti-contractile capability and PVAT-induced endothelial dysfunction in HFD-fed mice both in vivo and ex vivo. However, blocking PKA, or AMPK, but not cAMP, attenuated these beneficial effects of liraglutide. Treating HFD-fed mice with liraglutide activated the AMPK/eNOS pathway and induced browning-related gene expression. Moreover, liraglutide increased antioxidant capability. The protective effects were related to activation of a cAMP-independent PKA-AMPK pathway, as demonstrated by western blot and PCR.

CONCLUSIONS

Liraglutide improved vascular dysfunction by modulating a cAMP-independent PKA-AMPK pathway in PVAT in HFD-induced obese mice. The findings provide a novel mechanism for the cardiovascular protection of liraglutide by modulating PVAT function in obesity.

Influence of Age on Anticontractile Effect of Perivascular Adipose Tissue in Normotensive and Hypertensive Rats

Perivascular adipose tissue (PVAT) and its vasomodulatory effects play an important role in the physiology and pathophysiology of blood vessels. Alterations in PVAT associated with reduction in its anticontractile influence are proven to contribute to vascular dysfunction in hypertension. The aim of this study was to examine whether the changes in PVAT properties could participate in progression of vascular abnormalities in developing spontaneously hypertensive rats (SHR). Normotensive Wistar-Kyoto (WKY) rats and SHR, both in 5th and in 12th week of age, were used. Systolic blood pressure was similar between WKY rats and SHR in 5th week of age; however, in 12th week, it was significantly increased in SHR comparing to WKY rats. The amount of retroperitoneal fat was higher in WKY rats in both age groups, whereas body weight was higher in WKY rats only in 12th week, when compared to age-matched SHR. From isolated superior mesenteric arteries, two ring preparations were prepared for isometric tension recording, one with PVAT intact and other with PVAT removed. In WKY rats as well as in SHR, arterial contractile responses to noradrenaline, applied cumulatively on rings, were significantly inhibited in the presence of intact PVAT. In both age groups, anticontractile effect of PVAT was higher in WKY rats than in SHR. Neurogenic contractions, induced by electrical stimulation of perivascular sympathoadrenergic nerves, were significantly attenuated in the presence of PVAT in WKY mesenteric arteries from both age groups; however, in arteries from SHR, intact PVAT had no influence on this type of contractile responses. The results suggest that in SHR impairment of anticontractile effect of PVAT precedes hypertension and might contribute to its development.

Examining Vascular Structure and Function Using Confocal Microscopy and 3D Imaging Techniques

The structure of the blood vessel wall has historically been studied using thin cut sections using standard histological stains. In the mid-80s laser scanning confocal microscopes became available and offered investigators the chance to examine the 3D structure of thicker sections (i.e. ~60 μm depth penetration for a typical vascular wall). Unfortunately, desktop computers lagged far behind in their capacity to process and display large 3D (confocal) data sets. Even extremely highly priced graphics workstations of the early to mid-90s offered little in the way of flexible 3D viewing. Today's gaming PCs provide the kind of processing power that 3D confocal users have been waiting for. Coupled with high end animation software, virtual reality and game design software, we now have the capacity to exploit the huge data sets that modern microscopes can produce. In this chapter, the vascular wall will be used as an example of a biological tissue that can benefit from these developments in imaging hardware and software.