Integrating Computational and Biological Hemodynamic Approaches to Improve Modeling of Atherosclerotic Arteries

Atherosclerosis is the primary cause of cardiovascular disease, resulting in mortality, elevated healthcare costs, diminished productivity, and reduced quality of life for individuals and their communities. This is exacerbated by the limited understanding of its underlying causes and limitations in current therapeutic interventions, highlighting the need for sophisticated models of atherosclerosis. This review critically evaluates the computational and biological models of atherosclerosis, focusing on the study of hemodynamics in atherosclerotic coronary arteries. Computational models account for the geometrical complexities and hemodynamics of the blood vessels and stenoses, but they fail to capture the complex biological processes involved in atherosclerosis. Different in vitro and in vivo biological models can capture aspects of the biological complexity of healthy and stenosed vessels, but rarely mimic the human anatomy and physiological hemodynamics, and require significantly more time, cost, and resources. Therefore, emerging strategies are examined that integrate computational and biological models, and the potential of advances in imaging, biofabrication, and machine learning is explored in developing more effective models of atherosclerosis.

Engineering blood and lymphatic microvascular networks

The human vasculature plays a crucial role in the blood supply of nearly all organs as well as the drainage of the interstitial fluid. Consequently, if these physiological systems go awry, pathological changes might occur. Hence, the regeneration of existing vessels, as well as approaches to engineer artificial blood and lymphatic structures represent current challenges within the field of vascular research. In this review, we provide an overview of both the vascular blood circulation and the long-time neglected but equally important lymphatic system, with regard to their organotypic vasculature. We summarize the current knowledge within the field of vascular tissue engineering focusing on the design of co-culture systems, thereby mainly discussing suitable cell types, scaffold design and disease models. This review will mainly focus on addressing those subjects concerning atherosclerosis. Moreover, current technological approaches such as vascular organ-on-a-chip models and microfluidic devices will be discussed.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications—Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications-Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Long-term dietary nitrate supplementation slows the progression of established atherosclerosis in ApoE-/- mice fed a high fat diet

BACKGROUND AND AIMS

Atherosclerosis is associated with a reduction in the bioavailability and/or bioactivity of endogenous nitric oxide (NO). Dietary nitrate has been proposed as an alternate source when endogenous NO production is reduced. Our previous study demonstrated a protective effect of dietary nitrate on the development of atherosclerosis in the apoE-/- mouse model. However most patients do not present clinically until well after the disease is established. The aims of this study were to determine whether chronic dietary nitrate supplementation can prevent or reverse the progression of atherosclerosis after disease is already established, as well as to explore the underlying mechanism of these cardiovascular protective effects.

METHODS

60 apoE-/- mice were given a high fat diet (HFD) for 12 weeks to allow for the development of atherosclerosis. The mice were then randomized to (i) control group (HFD + 1 mmol/kg/day NaCl), (ii) moderate-dose group (HFD +1 mmol/kg/day NaNO3), or (iii) high-dose group (HFD + 10 mmol/kg/day NaNO3) (20/group) for a further 12 weeks. A group of apoE-/- mice (n = 20) consumed a normal laboratory chow diet for 24 weeks and were included as a reference group.

RESULTS

Long-term supplementation with high dose nitrate resulted in ~ 50% reduction in plaque lesion area. Collagen expression and smooth muscle accumulation were increased, and lipid deposition and macrophage accumulation were reduced within atherosclerotic plaques of mice supplemented with high dose nitrate. These changes were associated with an increase in nitrite reductase as well as activation of the endogenous eNOS-NO pathway.

CONCLUSION

Long-term high dose nitrate significantly attenuated the progression of established atherosclerosis in the apoE-/- mice fed a HFD. This appears to be mediated in part through a XOR-dependent reduction of nitrate to NO, as well as enhanced eNOS activation via increased Akt and eNOS phosphorylation.

Promoting Angiogenesis Using Immune Cells for Tissue-Engineered Vascular Grafts

Implantable tissue-engineered vascular grafts (TEVGs) usually trigger the host reaction which is inextricably linked with the immune system, including blood-material interaction, protein absorption, inflammation, foreign body reaction, and so on. With remarkable progress, the immune response is no longer considered to be entirely harmful to TEVGs, but its therapeutic and impaired effects on angiogenesis and tissue regeneration are parallel. Although the implicated immune mechanisms remain elusive, it is certainly worthwhile to gain detailed knowledge about the function of the individual immune components during angiogenesis and vascular remodeling. This review provides a general overview of immune cells with an emphasis on macrophages in light of the current literature. To the extent possible, we summarize state-of-the-art approaches to immune cell regulation of the vasculature and suggest that future studies are needed to better define the timing of the activity of each cell subpopulation and to further reveal key regulatory switches.

PRDX6-mediated pulmonary artery endothelial cell ferroptosis contributes to monocrotaline-induced pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening cardiopulmonary disorder whose underlying pathogenesis is unknown. Our previous study showed that pulmonary endothelial cell (PAEC) ferroptosis is involved in the progression of PH by releasing High-mobility group box 1 (HMGB1) and activating Toll-like receptor 4/NOD-like receptor family pyrin domain containing 3 (TLR4/NLRP3) inflammasome signalling. The precise mechanisms that regulate ferroptosis in PH are unclear. This study aimed to investigate the effect of peroxiredoxin 6 (PRDX6) on PAEC ferroptosis in PH.

METHODS

A rat model of PH was established with monocrotaline (MCT), and the distribution and expression of PRDX6 in the pulmonary artery were examined. Lentiviral vectors carrying PRDX6 (LV-PRDX6) were transfected into PAECs and injected into MCT-induced PH rats. Cell viability, MDA levels, reactive oxygen species (ROS) levels, labile iron pool (LIP) levels and mitochondrial morphology were examined. Ferroptosis-related proteins (NADPH oxidase-4 (NOX4), glutathione peroxidase 4 (GPX4), and ferritin heavy chain 1(FTH1)), TLR4, NLRP3 inflammasome markers, HMGB1 and inflammatory cytokines were examined. Pulmonary vascular remodelling and right ventricular structure and function were measured.

RESULTS

PRDX6 was expressed in PAECs and was significantly decreased in PH. PRDX6 overexpression significantly inhibited ferroptosis in PAECs under PH conditions in vitro and in vivo, as indicated by increased cell viability, decreased MDA, ROS and LIP levels, inhibited mitochondrial damage, upregulated GPX4 and FTH1 expression, and downregulated NOX4 expression. PRDX6 overexpression attenuated pulmonary vascular remodelling and changes in right ventricle structure and function in MCT-induced PH rats. Moreover, PRDX6 overexpression prevented HMGB1 release by PAECs and decreased TLR4 and NLRP3 inflammasome expression and inflammatory cytokine release in macrophages, while RSL3, a specific activator of ferroptosis, reversed these effects.

CONCLUSIONS

Taken together, these findings indicate that PRDX6 regulates PAEC ferroptosis through the release of HMGB1 and activation of the TLR4/NLRP3 inflammasome signalling pathway, providing novel therapeutic targets for the treatment of PH.

STING mediates SU5416/hypoxia-induced pulmonary arterial hypertension in rats by regulating macrophage NLRP3 inflammasome activation

BACKGROUND

The NLRP3 inflammasome in macrophages is known to promote infection-related vascular growth, and NLRP3 inflammasome activation interacts with PAH. STING is a crucial inflammatory reaction link that can increase the overexpression of NLRP3. However, the expression and effect of STING in PAH have not been elucidated. We examined the expression and articulation of STING in PAH and researched its hidden mechanism.

METHODS

A SU5416 plus hypoxia (Su/Hy)-induced rat model of PAH was constructed to examine STING activation. Su/Hy induced PAH rats were given a prophylactic injection of STING the inhibitor C-176. After modeling, hemodynamic changes, right ventricular hypertrophy index, lung morphological features, inflammasome activation, and proinflammatory cytokine secretion levels were assessed. In addition, the STING agonist DMXAA or inhibitor C-176 was used to interfere with LPS-induced BMDMs, NLRP3 inflammasome activation and cytokine secretion were examined, and the effect on PASMCs was evaluated in a coculture system.

RESULTS

STING expression increased significantly in the lung tissue of Su/Hy-treated PAH rats compared with normoxia-treated rats. Moreover, STING inhibitors can alleviate the Su/Hy-induced increase in pulmonary artery pressure and restrain the activation of the NLRP3 inflammasome and proinflammatory cytokines. In vitro experiments confirmed that STING affected the expression of the NLRP3 inflammasome and the secretion of inflammatory cytokines in BMDMs and promoted the proliferation of PASMCs in the coculture system.

CONCLUSION

Our study shows that STING is activated in Su/Hy-induced PAH and boosts the actuation of the macrophage NLRP3 inflammasome to advance the inflammatory response and vascular proliferation in rats with Su/Hy-induced pulmonary hypertension.

Targeting the Crosstalk of Immune Response and Vascular Smooth Muscle Cells Phenotype Switch for Arteriovenous Fistula Maturation

Plaque formation, thrombosis, and embolism are the underlying causes of acute cardiovascular events such as myocardial infarction and stroke while early thrombosis and stenosis are common pathologies for the maturation failure of arteriovenous fistula (AVF). Chronic inflammation is a common underlying pathogenesis mediated by innate and adaptive immune response involving infiltration of immune cells and secretion of pro- and anti-inflammatory cytokines. Impaired immune cell infiltration and change in vascular smooth muscle cell (VSMC) phenotype play a crucial role in the underlying pathophysiology. However, the change in the phenotype of VSMCs in a microenvironment of immune cell infiltration and increased secretion of cytokines have not been investigated. Since change in VSMC phenotype regulates vessel remodeling after intimal injury, in this study, we investigated the effect of macrophages and pro-inflammatory cytokines, IL-6, IL-1β, and TNF-α, on the change in VSMC phenotype under in vitro conditions. We also investigated the expression of the markers of VSMC phenotypes in arteries with atherosclerotic plaques and VSMCs isolated from control arteries. We found that the inhibition of cytokine downstream signaling may mitigate the effect of cytokines on the change in VSMCs phenotype. The results of this study support that regulating or targeting immune cell infiltration and function might be a therapeutic strategy to mitigate the effects of chronic inflammation to attenuate plaque formation, early thrombosis, and stenosis, and thus enhance AVF maturation.

Smooth Muscle Cell—Macrophage Interactions Leading to Foam Cell Formation in Atherosclerosis: Location, Location, Location

Cholesterol-overloaded cells or “foam cells” in the artery wall are the biochemical hallmark of atherosclerosis, and are responsible for much of the growth, inflammation and susceptibility to rupture of atherosclerotic lesions. While it has previously been thought that macrophages are the main contributor to the foam cell population, recent evidence indicates arterial smooth muscle cells (SMCs) are the source of the majority of foam cells in both human and murine atherosclerosis. This review outlines the timeline, site of appearance and proximity of SMCs and macrophages with lipids in human and mouse atherosclerosis, and likely interactions between SMCs and macrophages that promote foam cell formation and removal by both cell types. An understanding of these SMC-macrophage interactions in foam cell formation and regression is expected to provide new therapeutic targets to reduce the burden of atherosclerosis for the prevention of coronary heart disease, stroke and peripheral vascular disease.

Boosting Cholesterol Efflux from Foam Cells by Sequential Administration of rHDL to Deliver MicroRNA and to Remove Cholesterol in a Triple-Cell 2D Atherosclerosis Model

Cardiovascular disease, the leading cause of mortality worldwide, is primarily caused by atherosclerosis, which is characterized by lipid and inflammatory cell accumulation in blood vessels and carotid intima thickening. Although disease management has improved significantly, new therapeutic strategies focused on accelerating atherosclerosis regression must be developed. Atherosclerosis models mimicking in vivo-like conditions provide essential information for research and new advances toward clinical application. New nanotechnology-based therapeutic opportunities have emerged with apoA-I nanoparticles (recombinant/reconstituted high-density lipoproteins, rHDL) as ideal carriers to deliver molecules and the discovery that microRNAs participate in atherosclerosis establishment and progression. Here, a therapeutic strategy to improve cholesterol efflux is developed based on a two-step administration of rHDL consisting of a first dose of antagomiR-33a-loaded rHDLs to induce adenosine triphosphate-binding cassette transporters A1 overexpression, followed by a second dose of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine rHDLs, which efficiently remove cholesterol from foam cells. A triple-cell 2D-atheroma plaque model reflecting the cellular complexity of atherosclerosis is used to improve efficiency of the nanoparticles in promoting cholesterol efflux. The results show that sequential administration of rHDL potentiates cholesterol efflux indicating that this approach may be used in vivo to more efficiently target atherosclerotic lesions and improve prognosis of the disease.

Endothelial cell ferroptosis mediates monocrotaline-induced pulmonary hypertension in rats by modulating NLRP3 inflammasome activation

Inflammation triggers pulmonary vascular remodelling. Ferroptosis, a nonapoptotic form of cell death that is triggered by iron-dependent lipid peroxidation and contributes to the pathogenesis of several inflammation-related diseases, but its role in pulmonary hypertension (PH) has not been studied. We examined endothelial cell ferroptosis in PH and the potential mechanisms. Pulmonary artery endothelial cells (PAECs) and lung tissues from monocrotaline (MCT)-induced PH rats were analysed for ferroptosis markers, including lipid peroxidation, the labile iron pool (LIP) and the protein expression of glutathione peroxidase 4 (GPX4), ferritin heavy chain 1 (FTH1) and NADPH oxidase-4 (NOX4). The effects of the ferroptosis inhibitor ferrostatin-1 (Fer-1) on endothelial cell ferroptosis and pulmonary vascular remodelling in MCT-induced rats were studied in vitro and in vivo. Ferroptosis was observed in PAECs from MCT-induced PH rats in vitro and in vivo and was characterized by a decline in cell viability accompanied by increases in the LIP and lipid peroxidation, the downregulation of GPX4 and FTH1 expression and the upregulation of NOX4 expression. High-mobility group box 1 (HMGB1)/Toll-like receptor 4 (TLR4)/NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signalling was measured by western blotting. These changes were significantly blocked by Fer-1 administration in vitro and in vivo. These results suggest that Fer-1 plays a role in inhibiting ferroptosis-mediated PAEC loss during the progression of PH. The ferroptosis-induced inflammatory response depended on the activation of HMGB1/TLR4 signalling, which activated the NLRP3 inflammasome in vivo. We are the first to suggest that pulmonary artery endothelial ferroptosis triggers inflammatory responses via the HMGB1/TLR4/NLRP3 inflammasome signalling pathway in MCT-induced rats. Treating PH with a ferroptosis inhibitor and exploring new treatments based on ferroptosis regulation might be promising therapeutic strategies for PH.

Recent Progress in in vitro Models for Atherosclerosis Studies

Atherosclerosis is the primary cause of hardening and narrowing arteries, leading to cardiovascular disease accounting for the high mortality in the United States. For developing effective treatments for atherosclerosis, considerable efforts have been devoted to developing in vitro models. Compared to animal models, in vitro models can provide great opportunities to obtain data more efficiently, economically. Therefore, this review discusses the recent progress in in vitro models for atherosclerosis studies, including traditional two-dimensional (2D) systems cultured on the tissue culture plate, 2D cell sheets, and recently emerged microfluidic chip models with 2D culture. In addition, advanced in vitro three-dimensional models such as spheroids, cell-laden hydrogel constructs, tissue-engineered blood vessels, and vessel-on-a-chip will also be covered. Moreover, the functions of these models are also summarized along with model discussion. Lastly, the future perspectives of this field are discussed.

Molecular Interactions Between Vascular Smooth Muscle Cells and Macrophages in Atherosclerosis

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

CTRP9 induces macrophages polarization into M1 phenotype through activating JNK pathway and enhances VSMCs apoptosis in macrophages and VSMCs co-culture system

Inflammation plays a critical role in the development of atherosclerosis (AS), which has been identified as a major predisposing factor for stroke. Macrophages and VSMCs are associated with plaque formation and progression. Macrophages can dynamically change into two main functional phenotypes, namely M1 and M2, they can produce either pro-inflammatory or anti-inflammatory factors which may affect the outcome of inflammation. As a member of CTRPs family, CTRP9 has been reported play important protective roles in the cardiovascular system. However, whether CTRP9 can regulate macrophage activation status in inflammatory responses and have effect on VSMCs behaviors in co-culture system have not been fully investigated. In the present study, using peritoneal macrophages treated with CTRP9, we found that CTRP9 facilitated macrophages towards M1 phenotype, promoted TNF-α secretion and MMPs expression. CTRP9 showed synergistic effect with LPS in inducing M1 macrophages. In macrophages-VSMCs co-culture system, apoptosis and down-regulated proliferation of VSMCs were accelerated with CTRP9-treated macrophages. Then we attempted to explore the underlying molecular mechanisms of CTRP9 resulting in M1 activation. The c-Jun NH2-terminal kinases (JNK) are members of the mitogen activated protein kinases (MAPK) family, plays a central role in the cell stress response, with outcomes ranging from cell death to cell proliferation and survival. We found JNK expression was upregulated following CTRP9 stimulation, and inhibiting JNK phosphorylation level was associated with decreased expression of M1 markers and TNF-α concentration. Moreover, VSMCs apoptosis were ameliorated after inhibition of JNK. These results suggested that CTRP9 may promote macrophage towards M1 activation status through JNK signaling pathway activation.

Human Cell Modeling for Cardiovascular Diseases

The availability of appropriate and reliable in vitro cell models recapitulating human cardiovascular diseases has been the aim of numerous researchers, in order to retrace pathologic phenotypes, elucidate molecular mechanisms, and discover therapies using simple and reproducible techniques. In the past years, several human cell types have been utilized for these goals, including heterologous systems, cardiovascular and non-cardiovascular primary cells, and embryonic stem cells. The introduction of induced pluripotent stem cells and their differentiation potential brought new prospects for large-scale cardiovascular experiments, bypassing ethical concerns of embryonic stem cells and providing an advanced tool for disease modeling, diagnosis, and therapy. Each model has its advantages and disadvantages in terms of accessibility, maintenance, throughput, physiological relevance, recapitulation of the disease. A higher level of complexity in diseases modeling has been achieved with multicellular co-cultures. Furthermore, the important progresses reached by bioengineering during the last years, together with the opportunities given by pluripotent stem cells, have allowed the generation of increasingly advanced in vitro three-dimensional tissue-like constructs mimicking in vivo physiology. This review provides an overview of the main cell models used in cardiovascular research, highlighting the pros and cons of each, and describing examples of practical applications in disease modeling.

A Novel Triple-Cell Two-Dimensional Model to Study Immune-Vascular Interplay in Atherosclerosis

Atherosclerosis is a complex inflammatory pathology underpinning cardiovascular diseases (CVD), which are the leading cause of death worldwide. The interplay between vascular stromal cells and immune cells is fundamental to the progression and outcome of atherosclerotic disease, however, the majority of in vitro studies do not consider the implications of these interactions and predominantly use mono-culture approaches. Here we present a simple and robust methodology involving the co-culture of vascular endothelial (ECs) and smooth muscle cells (SMCs) alongside an inflammatory compartment, in our study containing THP-1 macrophages, for studying these complex interactions. Using this approach, we demonstrate that the interaction between vascular stromal and immune cells produces unique cellular phenotypes and soluble mediator profiles not observed in double-cell 2D cultures. Our results highlight the importance of cellular communication and support the growing idea that in vitro research must evolve from mono-culture systems to provide data more representative of the multi-cellular environment found in vivo. The methodology presented, in comparison with established approaches, has the advantage of being technically simple whilst enabling the isolation of pure populations of ECs, SMCs and immune cells directly from the co-culture without cell sorting. The approach described within would be applicable to those studying mechanisms of vascular inflammation, particularly in relation to understanding the impact cellular interaction has on the cumulative immune-vascular response to atherogenic or inflammatory stimuli.

Pathways of smooth muscle foam cell formation in atherosclerosis

PURPOSE OF REVIEW

Smooth muscle cells (SMCs) are the major cell type in human atherosclerosis-prone arteries and take up excess lipids, thereby contributing to luminal occlusion. Here we provide a focused review on pathways by which smooth muscle cells (SMCs) can become foam cells in atherosclerosis.

RECENT FINDINGS

A synthesis of recent and older investigations provides key mechanistic insights into SMC foam cell formation. LDL and other apoB-containing lipoproteins are modified by a diverse array of oxidative, enzymatic, and nonenzymatic processes present in the arterial intima. These modifications of LDL all promote the aggregation of LDL (agLDL), a key finding from analysis of arterial lesion particles. Scavenger receptor and phagocytic capacity of SMCs can vary greatly, perhaps related to differences in SMC phenotype or in-vitro cell culture environments, and can be increased with exposure to cytokines, growth factors, and cholesterol. Macrophages promote the formation of SMC foam cells in direct or indirect co-culture models.

SUMMARY

SMCs contribute significantly to the foam cell population in atherosclerosis. Further investigation and identification of key mechanisms of SMC foam cell formation will help drive new therapeutics to reduce cardiovascular disease.

Physiologic levels of resistin induce a shift from proliferation to apoptosis in macrophage and VSMC co-culture

BACKGROUND

Resistin, an adipokine with inflammatory properties, has been associated with plaque vulnerability. Vascular smooth muscle cells and macrophages are the major cellular components in advanced atherosclerotic plaques and interdependently affect plaque stability. The purpose of this study was to examine the effects of resistin on the interactions of vascular smooth muscle cells and macrophages using co-culture systems.

METHODS

Human monocytes were differentiated into macrophages. Vascular smooth muscle cells were grown and starved prior to co-culture condition. Indirect co-culture was performed by treating macrophages with resistin at 10 ng/mL for 24 hours with/without εV1-2, a selective protein kinase C epsilon inhibitor. Macrophages supernatants were then used to treat vascular smooth muscle cells for 24 hours. Direct co-culture was performed by culturing macrophages and vascular smooth muscle cells together for 24 to 48 hours. Cultures were evaluated for changes in proliferation, apoptosis, and gene expression of apoptosis, proliferation, and inflammation-associated genes.

RESULTS

Macrophages induced vascular smooth muscle cells proliferation, which was further exaggerated in resistin-treated macrophages in the indirect co-culture model. Resistin also upregulated cyclin D1 and proliferating cell nuclear antigen via protein kinase C epsilon in the indirect co-culture. Augmented proliferation was further confirmed in the direct co-culture model, particularly at increased macrophage ratios. However, resistin treatment induced apoptosis in the presence of direct cell to cell interactions. Along with the shift to apoptosis, expressions of caspase 3 and caspase 8 were upregulated. The expression of kappa-light-chain-enhancer of activated B cells 1 and 2 was similar in direct and indirect co-cultures.

CONCLUSION

Resistin promotes a shift from proliferation to apoptosis in vascular smooth muscle cells and macrophage co-culture systems with cellular composition similar to that found in vulnerable regions of plaques. Protein kinase C epsilon mediates the effects of resistin, suggesting that protein kinase C epsilon may represent a therapeutic strategy in resistin-associated atherosclerotic complications.

Determining the cross-talk between smooth muscle cells and macrophages on a cobalt-chromium stent material surface using an in vitro postimplantation coculture model

Smooth muscle cells (SMCs) and macrophages are important cellular components involved in the development of complications following the implantation of cardiovascular devices. This leads to various disorders such as restenosis, chronic inflammation, and may ultimately result in device failure. In this study, we developed a postimplant stent coculture model using different ratios of SMCs and macrophages seeded on to cobalt-chromium alloy. The macrophages had an increased affinity to the coculture surfaces, which resulted in decreased SMC attachment to the alloy surfaces at the initial time point. Once adhered, the macrophages spread freely and displayed advanced stages of inflammation at 48 h when cocultured with SMCs. This resulted in an increased secretion of proinflammatory cytokines (tumor necrosis factor alpha, monocyte chemotactic protein 1, interleukin [IL]-6, and IL-8) by 48 h in the coculture samples with the greatest increase observed with the high number of macrophages. Therefore, the increased levels of proinflammatory cytokines promoted the growth of SMCs in coculture to a greater extent than when the SMCs were culture alone. Thus, this study demonstrated the constant cross-talk between SMCs and macrophages occurring on the postimplant stent surface. Similar coculture models can be used to test the biocompatibility of drugs and biomaterials at possible postimplantation scenarios. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 673-685, 2018.

Semiautomatic High-Content Analysis of Complex Images from Cocultures of Vascular Smooth Muscle Cells and Macrophages: A CellProfiler Showcase

Automatization in microscopy, cell culture, and the ease of digital imagery allow obtainment of more information from single samples and upscaling of image-based analysis to high-content approaches. Simple segmentation algorithms of biological imagery are nowadays widely spread in biomedical research, but processing of complex sample structures, for example, variable sample compositions, cell shapes, and sizes, and rare events remains a difficult task. As there is no perfect method for image segmentation and fully automatic image analysis of complex content, we aimed to succeed by identification of unique and reliable features within the sample. Through exemplary use of a coculture of vascular smooth muscle cells (VSMCs) and macrophages (MPs), we demonstrate how rare interactions within this highly variable sample type can be analyzed. Because of limitations in immunocytochemistry in our specific setup, we developed a semiautomatic approach to examine the interaction of lipid-laden MPs with VSMCs under hypoxic conditions based on nuclei morphology by high-content analysis using the open-source software CellProfiler ( www.cellprofiler.org ). We provide evidence that, in comparison with fully automatic analysis, a low threshold within the analysis workflow and subsequent manual control save time, while providing more objective and reliable results.

PKC-epsilon and TLR4 synergistically regulate resistin-mediated inflammation in human macrophages

BACKGROUND AND AIMS

Resistin has been associated with atherosclerotic inflammation and cardiovascular complications. We and others have previously shown that PKC-epsilon (PKCε) is involved in resistin-induced smooth muscle cell (VSMC) dysfunction at a high pathological concentration. This study aimed to evaluate the role and potential pathways of resistin at a physiological concentration, in atherosclerosis-related inflammation.

METHODS

Plasma from patients with atherosclerosis was analyzed for resistin concentration. Patients were divided into tertiles based on resistin levels and cytokines were compared between tertiles. Macrophages were then treated with resistin in the presence or absence of PKCε inhibitor and/or TLR4 blocking-antibody, and their inflammatory state was evaluated with ELISA, RT-PCR, immunocytochemistry, and Western blot.

RESULTS

We observed significant associations between plasma resistin levels and TNF-α, IL-6, IL-12, MIP-1α, MIP-1β, and CD40L. Our in vitro analyses revealed that resistin activated PKCε via TLR4. This was followed by NF-kB activation and induction of a pro-inflammatory phenotype in macrophages, significantly upregulating CD40, downregulating CD206 and stimulating gene expression and secretion of the inflammatory cytokines, for which we found association in our plasma analysis. Resistin also induced persistent TRAM and CD40L upregulation up to 36 h after resistin treatment. PKCε and TLR4 inhibitors suppressed gene expression to levels similar to control, especially when used in combination.

CONCLUSIONS

Resistin, at a physiological concentration, exacerbates the inflammatory response of macrophages. PKCε is a key upstream mediator in resistin-induced inflammation that may interact synergistically with TLR4 to promote NF-kB activation, while TRAM is an important signal. PKCε and TRAM may represent novel molecular targets for resistin-associated chronic atherosclerotic inflammation.

Impact of Polyunsaturated Fatty Acids on miRNA Profiles of Monocytes/Macrophages and Endothelial Cells-A Pilot Study

Alteration of miRNAs and dietary polyunsaturated fatty acids (PUFAs) underlies vascular inflammation. PUFAs are known to be incorporated into the cell membrane of monocytes/macrophages or endothelial cells, the major cellular players of vascular diseases, thereby affecting cellular signal transduction. Nevertheless, there are no investigations concerning the PUFA impact on miRNA expression by these cells. With regard to the key role miRNAs play for overall cellular functionality, this study aims to elucidate whether PUFAs affect miRNA expression profiles. To this end, the monocyte/macrophage cell line RAW264.7 and the endothelial cell line TIME were enriched with either docosahexaenoic acid (DHA; n3-PUFA) or arachidonic acid (AA; n6-PUFA) until reaching a stable incorporation into the plasma membrane and, at least in part, exposed to an inflammatory milieu. Expressed miRNAs were determined by deep sequencing, and compared to unsupplemented/unstimulated controls. Data gained clearly show that PUFAs in fact modulate miRNA expression of both cell types analyzed regardless the presence/absence of an inflammatory stimulator. Moreover, certain miRNAs already linked to vascular inflammation were found to be affected by cellular PUFA enrichment. Hence, vascular inflammation appears to be influenced by dietary fatty acids, inter alia, via PUFA-mediated modulation of the type and amount of miRNAs synthesized by cells involved in the inflammatory process.

Does plasma membrane lipid composition impact the miRNA-mediated regulation of vascular inflammation?

BACKGROUND

Both PUFA and miRNAs are believed to be of importance in vascular diseases. On the one hand diverse nutrition societies recommend PUFA consumption to dampen inflammatory processes. On the other hand scientists intensify efforts to use miRNAs for diagnostics or therapy in context of vascular disorders.

PRESENTATION OF THE HYPOTHESIS

There might be is a causal link between the plasma membrane lipid composition and the miRNA expression of monocytes and endothelial cells. PUFA enrichment of cells may affect the type and the amount of particular miRNAs produced. In this way dietary fatty acids are supposed to impact the miRNA-mediated regulation of vascular inflammatory processes.

PROPOSED EXPERIMENTAL SETTING TO TEST THE HYPOTHESIS

PUFA-supplemented monocytes and endothelial cells are analyzed with respect to membrane fatty acid patterns, typical markers of vascular inflammation and miRNA expression. Experiments are performed both for undifferentiated/unstimulated as well as for differentiated/stimulated cells. Verification of identified miRNA targets is performed by means of mimics/antagomirs.

IMPLICATIONS OF THE HYPOTHESIS

Innovative mechanism of action, which could point the way to a new understanding of the PUFA-mediated modulation of cellular signal transduction. If confirmed experimentally, it might stimulate vascular inflammation research and immunologic lipid science, hence, acting as source of inspiration for future therapeutic interventions in vascular diseases.

Revisiting cardiovascular calcification: A multifaceted disease requiring a multidisciplinary approach

The presence of cardiovascular calcification significantly predicts patients' morbidity and mortality. Calcific mineral deposition within the soft cardiovascular tissues disrupts the normal biomechanical function of these tissues, leading to complications such as heart failure, myocardial infarction, and stroke. The realization that calcification results from active cellular processes offers hope that therapeutic intervention may prevent or reverse the disease. To this point, however, no clinically viable therapies have emerged. This may be due to the lack of certainty that remains in the mechanisms by which mineral is deposited in cardiovascular tissues. Gaining new insight into this process requires a multidisciplinary approach. The pathological changes in cell phenotype that lead to the physicochemical deposition of mineral and the resultant effects on tissue biomechanics must all be considered when designing strategies to treat cardiovascular calcification. In this review, we overview the current cardiovascular calcification paradigm and discuss emerging techniques that are providing new insight into the mechanisms of ectopic calcification.