Shear stress selectively upregulates intercellular adhesion molecule-1 expression in cultured human vascular endothelial cells

Blood Hemoglobin Concentrations and the Incidence of Lower Extremity Peripheral Arterial Disease in Patients Undergoing Hemodialysis: 10-Year Outcomes of the Q-Cohort Study

BACKGROUND

Lower extremity peripheral arterial disease is a potentially lethal cardiovascular complication in patients undergoing hemodialysis. Anemia is a risk factor for cardiovascular disease among the hemodialysis population. However, whether blood hemoglobin concentration is associated with the risk of peripheral arterial disease progression in this population remains undetermined.

METHODS AND RESULTS

This is an extension of a 4-year multicenter, prospective, observational cohort study to 10 years. A total of 3504 Japanese patients undergoing maintenance hemodialysis were recruited between 2006 and 2007. The primary exposure was blood hemoglobin concentration at baseline. The main outcome was the first-ever incidence of major adverse limb events (MALE), composed of endovascular treatment, bypass surgery, and amputation. Multivariable-adjusted Cox proportional hazards model, Fine-Gray subdistribution hazards model, restricted cubic spline analysis, and restricted mean survival time analysis were used to determine the association of blood hemoglobin concentration with the incidence of MALE. During a median follow-up of 8.0 years, 257 patients experienced MALE. A Cox proportional hazards model showed that the risk of MALE in patients with blood hemoglobin concentrations <10.0 g/dL was significantly higher than in patients with concentrations of 11.0 to 11.9 g/dL, even after adjusting for confounding factors. In contrast, elevated hemoglobin concentration (≥12.0 g/dL) was not significantly associated with increased risk of MALE. Similar associations were observed when the Fine-Gray subdistribution regression model was used by setting all-cause mortality as the competing risk.

CONCLUSIONS

A low blood hemoglobin concentration is an independent risk factor for peripheral arterial disease progression in patients undergoing maintenance hemodialysis.

Association between baseline hemoglobin level and early neurological deterioration after intravenous thrombolysis in patients with acute ischemic stroke

OBJECTIVES

To investigate the association between baseline hemoglobin level and early neurologic deterioration (END) after intravenous thrombolysis in patients with acute ischemic stroke (AIS).

METHODS

Data of AIS patients who received intravenous thrombolytic therapy at multiple hospitals across the country between January 2017 and July 2020 were collected from the online database Acute Stroke Patients for Stroke Management Quality Evaluation (CASE-Ⅱ, NCT04487340). Binary logistic regression analysis was used to study the factors affecting the occurrence of END after intravenous thrombolytic therapy, and the correlation between baseline hemoglobin level and END was investigated by limiting cubic spline curve analysis.

RESULTS

A total of 8162 patients were included. Patients with END had lower baseline hemoglobin levels (136 and 140 g/L, P<0.01) and higher rates of anemia (24.2% and 16.9%, P<0.01) compared with non-END patients. Binary logistic regression analysis showed that baseline hemoglobin level (OR=0.995, 95%CI: 0.991-0.999, P<0.05) and anemia (OR=1.238, 95%CI: 1.055-1.454, P<0.01) were independently correlated with the occurrence of END after intravenous thrombolysis in AIS patients. Restricted cubic spline regression showed that there was a U-shaped relationship between hemoglobin level and the risk of END after intravenous thrombolysis in AIS patients (P<0.01), although this relationship was only significant in male patients (P<0.05) and not in female patients (P>0.05).

CONCLUSIONS

There is a correlation between baseline hemoglobin level and the risk of END in AIS patients after intravenous thrombolysis, especially in male patients, in whom both lower and higher hemoglobin level may increase the risk of END.

Cutaneous vasculitis: insights into pathogenesis and histopathological features

The mechanisms underlying the onset and progression of vasculitis remain poorly understood. This condition is characterized by damage to the vascular wall, recruitment of inflammatory cells, and subsequent structural remodeling, which are hallmarks of vasculitis. The histopathological classification of vasculitis relies on the size of the affected vessel and the predominant type of inflammatory cell involved - neutrophils in acute cases, lymphocytes in chronic conditions, and histiocytes in granulomatous forms. Pathological changes progress in every context, and a single vasculitic pattern can be associated with various systemic conditions. Conversely, a single causative agent may lead to multiple distinct clinical and pathological manifestations of vasculitis. Moreover, many cases of vasculitis have no identifiable cause. A foundational understanding of the normal structure of the cutaneous vascular network is crucial. Similarly, identifying the cellular and molecular participants and their roles in forming the "dermal microvascular unit" is propedeutical.

This review aims to elucidate the complex mechanisms involved in the initiation and progression of vasculitis, offering a comprehensive overview of its histopathological classification, underlying causes, and the significant role of the cutaneous vascular network and cellular dynamics. By integrating the latest insights from studies on NETosis and the implications of lymphocytic infiltration in autoimmune diseases, we seek to bridge gaps in current knowledge and highlight areas for future research. Our discussion extends to the clinical implications of vasculitis, emphasizing the importance of identifying etiological agents and understanding the diverse histopathological manifestations to improve diagnostic accuracy and treatment outcomes.

Chemokine Fractalkine and Non-Obstructive Coronary Artery Disease-Is There a Link?

Non-obstructive coronary artery disease (NO-CAD) constitutes a heterogeneous group of conditions collectively characterized by less than 50% narrowing in at least one major coronary artery with a fractional flow reserve (FFR) of ≤0.80 observed in coronary angiography. The pathogenesis and progression of NO-CAD are still not fully understood, however, inflammatory processes, particularly atherosclerosis and microvascular dysfunction are known to play a major role in it. Chemokine fractalkine (FKN/CX3CL1) is inherently linked to these processes. FKN/CX3CL1 functions predominantly as a chemoattractant for immune cells, facilitating their transmigration through the vessel wall and inhibiting their apoptosis. Its concentrations correlate positively with major cardiovascular risk factors. Moreover, promising preliminary results have shown that FKN/CX3CL1 receptor inhibitor (KAND567) administered in the population of patients with ST-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI), inhibits the adverse reaction of the immune system that causes hyperinflammation. Whereas the link between FKN/CX3CL1 and NO-CAD appears evident, further studies are necessary to unveil this complex relationship. In this review, we critically overview the current data on FKN/CX3CL1 in the context of NO-CAD and present the novel clinical implications of the unique structure and function of FKN/CX3CL1 as a compound which distinctively contributes to the pathomechanism of this condition.

Bioactive TNIIIA2 Sequence in Tenascin-C Is Responsible for Macrophage Foam Cell Transformation; Potential of FNIII14 Peptide Derived from Fibronectin in Suppression of Atherosclerotic Plaque Formation

One of the extracellular matrix proteins, tenascin-C (TN-C), is known to be upregulated in age-related inflammatory diseases such as cancer and cardiovascular diseases. Expression of this molecule is frequently detected, especially in the macrophage-rich areas of atherosclerotic lesions; however, the role of TN-C in mechanisms underlying the progression of atherosclerosis remains obscure. Previously, we found a hidden bioactive sequence termed TNIIIA2 in the TN-C molecule and reported that the exposure of this sequence would be carried out through limited digestion of TN-C by inflammatory proteases. Thus, we hypothesized that some pro-atherosclerotic phenotypes might be elicited from macrophages when they were stimulated by TNIIIA2. In this study, TNIIIA2 showed the ability to accelerate intracellular lipid accumulation in macrophages. In this experimental condition, an elevation of phagocytic activity was observed, accompanied by a decrease in the expression of transporters responsible for lipid efflux. All these observations were mediated through the induction of excessive β1-integrin activation, which is a characteristic property of the TNIIIA2 sequence. Finally, we demonstrated that the injection of a drug that targets TNIIIA2's bioactivity could rescue mice from atherosclerotic plaque expansion. From these observations, it was shown that TN-C works as a pro-atherosclerotic molecule through an internal TNIIIA2 sequence. The possible advantages of clinical strategies targeting TNIIIA2 are also indicated.

Flow-induced reprogramming of endothelial cells in atherosclerosis

Atherosclerotic diseases such as myocardial infarction, ischaemic stroke and peripheral artery disease continue to be leading causes of death worldwide despite the success of treatments with cholesterol-lowering drugs and drug-eluting stents, raising the need to identify additional therapeutic targets. Interestingly, atherosclerosis preferentially develops in curved and branching arterial regions, where endothelial cells are exposed to disturbed blood flow with characteristic low-magnitude oscillatory shear stress. By contrast, straight arterial regions exposed to stable flow, which is associated with high-magnitude, unidirectional shear stress, are relatively well protected from the disease through shear-dependent, atheroprotective endothelial cell responses. Flow potently regulates structural, functional, transcriptomic, epigenomic and metabolic changes in endothelial cells through mechanosensors and mechanosignal transduction pathways. A study using single-cell RNA sequencing and chromatin accessibility analysis in a mouse model of flow-induced atherosclerosis demonstrated that disturbed flow reprogrammes arterial endothelial cells in situ from healthy phenotypes to diseased ones characterized by endothelial inflammation, endothelial-to-mesenchymal transition, endothelial-to-immune cell-like transition and metabolic changes. In this Review, we discuss this emerging concept of disturbed-flow-induced reprogramming of endothelial cells (FIRE) as a potential pro-atherogenic mechanism. Defining the flow-induced mechanisms through which endothelial cells are reprogrammed to promote atherosclerosis is a crucial area of research that could lead to the identification of novel therapeutic targets to combat the high prevalence of atherosclerotic disease.

Engineering choroid plexus-on-a-chip with oscillatory flow for modeling brain metastasis

The human brain choroid plexus (ChP) is a highly organized secretory tissue with a complex vascular system and epithelial layers in the ventricles of the brain. The ChP is the body's principal source of cerebrospinal fluid (CSF); it also functions as a barrier to separate the blood from CSF, because the movement of CSF through the body is pulsatile in nature. Thus far, it has been challenging to recreate the specialized features and dynamics of the ChP in a physiologically relevant microenvironment. In this study, we recapitulated the ChP structure by developing a microfluidic chip in accordance with established design rules. Furthermore, we used image processing and analysis to mimic CSF flow dynamics within a rlcking system; we also used a hydrogel containing laminin to mimic brain extracellular matrix (ECM). Human ChP cells were cultured in the ChP-on-a-chip with in vivo-like CSF dynamic flow and an engineered ECM. The key ChP characteristics of capillaries, the epithelial layer, and secreted components were recreated in the adjusted microenvironment of our human ChP-on-a-chip. The drug screening capabilities of the device were observed through physiologically relevant drug responses from breast cancer cells that had spread in the ChP. ChP immune responses were also recapitulated in this device, as demonstrated by the motility and cytotoxic effects of macrophages, which are the most prevalent immune cells in the ChP. Our human ChP-on-a-chip will facilitate the elucidation of ChP pathophysiology and support the development of therapeutics to treat cancers that have metastasized into the ChP.

Nuclear mechanosensing of the aortic endothelium in health and disease

The endothelium, the monolayer of endothelial cells that line blood vessels, is exposed to a number of mechanical forces, including frictional shear flow, pulsatile stretching and changes in stiffness influenced by extracellular matrix composition. These forces are sensed by mechanosensors that facilitate their transduction to drive appropriate adaptation of the endothelium to maintain vascular homeostasis. In the aorta, the unique architecture of the vessel gives rise to changes in the fluid dynamics, which, in turn, shape cellular morphology, nuclear architecture, chromatin dynamics and gene regulation. In this Review, we discuss recent work focusing on how differential mechanical forces exerted on endothelial cells are sensed and transduced to influence their form and function in giving rise to spatial variation to the endothelium of the aorta. We will also discuss recent developments in understanding how nuclear mechanosensing is implicated in diseases of the aorta.

Analysis of flow-induced transcriptional response and cell alignment of different sources of endothelial cells used in vascular tissue engineering

Endothelialization of tissue-engineered vascular grafts has proven crucial for implant functionality and thus clinical outcome, however, the choice of endothelial cells (ECs) is often driven by availability rather than by the type of vessel to be replaced. In this work we studied the response to flow of different human ECs with the aim of examining whether their response in vitro is dictated by their original in vivo conditions. Arterial, venous, and microvascular ECs were cultured under shear stress (SS) of 0, 0.3, 3, 1, 10, and 30 dyne/cm2 for 24 h. Regulation of flow-induced marker KLF2 was similar across the different ECs. Upregulation of anti-thrombotic markers, TM and TPA, was mainly seen at higher SS. Cell elongation and alignment was observed for the different ECs at 10 and 30 dyne/cm2 while at lower SS cells maintained a random orientation. Downregulation of pro-inflammatory factors SELE, IL8, and VCAM1 and up-regulation of anti-oxidant markers NQO1 and HO1 was present even at SS for which cell alignment was not observed. Our results evidenced similarities in the response to flow among the different ECs, suggesting that the maintenance of the resting state in vitro is not dictated by the SS typical of the tissue of origin and that absence of flow-induced cell orientation does not necessarily correlate with a pro-inflammatory state of the ECs. These results support the use of ECs from easily accessible sources for in vitro vascular tissue engineering independently from the target vessel.

Adhesion to the Brain Endothelium Selects Breast Cancer Cells with Brain Metastasis Potential

Tumor cells metastasize from a primary lesion to distant organs mainly through hematogenous dissemination, in which tumor cell re-adhesion to the endothelium is essential before extravasating into the target site. We thus hypothesize that tumor cells with the ability to adhere to the endothelium of a specific organ exhibit enhanced metastatic tropism to this target organ. This study tested this hypothesis and developed an in vitro model to mimic the adhesion between tumor cells and brain endothelium under fluid shear stress, which selected a subpopulation of tumor cells with enhanced adhesion strength. The selected cells up-regulated the genes related to brain metastasis and exhibited an enhanced ability to transmigrate through the blood-brain barrier. In the soft microenvironments that mimicked brain tissue, these cells had elevated adhesion and survival ability. Further, tumor cells selected by brain endothelium adhesion expressed higher levels of MUC1, VCAM1, and VLA-4, which were relevant to breast cancer brain metastasis. In summary, this study provides the first piece of evidence to support that the adhesion of circulating tumor cells to the brain endothelium selects the cells with enhanced brain metastasis potential.

Cerebral malaria - modelling interactions at the blood-brain barrier in vitro

The blood–brain barrier (BBB) is a continuous endothelial barrier that is supported by pericytes and astrocytes and regulates the passage of solutes between the bloodstream and the brain. This structure is called the neurovascular unit and serves to protect the brain from blood-borne disease-causing agents and other risk factors. In the past decade, great strides have been made to investigate the neurovascular unit for delivery of chemotherapeutics and for understanding how pathogens can circumvent the barrier, leading to severe and, at times, fatal complications. One such complication is cerebral malaria, in which Plasmodium falciparum-infected red blood cells disrupt the barrier function of the BBB, causing severe brain swelling. Multiple in vitro models of the BBB are available to investigate the mechanisms underlying the pathogenesis of cerebral malaria and other diseases. These range from single-cell monolayer cultures to multicellular BBB organoids and highly complex cerebral organoids. Here, we review the technologies available in malaria research to investigate the interaction between P. falciparum-infected red blood cells and the BBB, and discuss the advantages and disadvantages of each model.

Summary: This Review discusses the available in vitro models to investigate the impact of adhesion of Plasmodium falciparum-infected red blood cells on the blood–brain barrier, a process associated with cerebral malaria.

Application of blood brain barrier models in pre-clinical assessment of glioblastoma-targeting CAR-T based immunotherapies

Human blood brain barrier (BBB) models derived from induced pluripotent stem cells (iPSCs) have become an important tool for the discovery and preclinical evaluation of central nervous system (CNS) targeting cell and gene-based therapies. Chimeric antigen receptor (CAR)-T cell therapy is a revolutionary form of gene-modified cell-based immunotherapy with potential for targeting solid tumors, such as glioblastomas. Crossing the BBB is an important step in the systemic application of CAR-T therapy for the treatment of glioblastomas and other CNS malignancies. In addition, even CAR-T therapies targeting non-CNS antigens, such as the well-known CD19-CAR-T therapies, are known to trigger CNS side-effects including brain swelling due to BBB disruption. In this study, we used iPSC-derived brain endothelial-like cell (iBEC) transwell co-culture model to assess BBB extravasation of CAR-T based immunotherapies targeting U87MG human glioblastoma (GBM) cells overexpressing the tumor-specific mutated protein EGFRvIII (U87vIII). Two types of anti-EGFRvIII targeting CAR-T cells, with varying tonic signaling profiles (CAR-F263 and CAR-F269), and control Mock T cells were applied on the luminal side of BBB model in vitro. CAR-F263 and CAR-F269 T cells triggered a decrease in transendothelial electrical resistance (TEER) and an increase in BBB permeability. CAR-T cell extravasation and U87vIII cytotoxicity were assessed from the abluminal compartment using flow cytometry and Incucyte real-time viability imaging, respectively. A significant decrease in U87vIII cell viability was observed over 48 h, with the most robust cytotoxicity response observed for the constitutively activated CAR-F263. CAR-F269 T cells showed a similar cytotoxic profile but were approximately four fold less efficient at killing the U87vIII cells compared to CAR-F263, despite similar transmigration rates. Visualization of CAR-T cell extravasation across the BBB was further confirmed using BBTB-on-CHIP models. The described BBB assay was able to discriminate the cytotoxic efficacies of different EGFRvIII-CARs and provide a measure of potential alterations to BBB integrity. Collectively, we illustrate how BBB models in vitro can be a valuable tool in deciphering the mechanisms of CAR-T–induced BBB disruption, accompanying toxicity and effector function on post-barrier target cells.

Modular 3D In Vitro Artery-Mimicking Multichannel System for Recapitulating Vascular Stenosis and Inflammation

Inflammation and the immune response in atherosclerosis are complex processes involving local hemodynamics, the interaction of dysfunctional cells, and various pathological environments. Here, a modular multichannel system that mimics the human artery to demonstrate stenosis and inflammation and to study physical and chemical effects on biomimetic artery models is presented. Smooth muscle cells and endothelial cells were cocultured in the wrinkled surface in vivo-like circular channels to recapitulate the artery. An artery-mimicking multichannel module comprised four channels for the fabrication of coculture models and assigned various conditions for analysis to each model simultaneously. The manipulation became reproducible and stable through modularization, and each module could be replaced according to analytical purposes. A chamber module for culture was replaced with a microfluidic concentration gradient generator (CGG) module to achieve the cellular state of inflamed lesions by providing tumor necrosis factor (TNF)-α, in addition to the stenosis structure by tuning the channel geometry. Different TNF-α doses were administered in each channel by the CGG module to create functional inflammation models under various conditions. Through the tunable channel geometry and the microfluidic interfacing, this system has the potential to be used for further comprehensive research on vascular diseases such as atherosclerosis and thrombosis.

Plasma biomarker factors associated with neurodevelopmental outcomes in children with perinatal HIV infection and controlled viremia

OBJECTIVE

We examined relationships between plasma biomarkers and neurodevelopment in children from sub-Saharan Africa with perinatal HIV (PHIV) with controlled viremia on antiretroviral therapy (ART).

DESIGN

Longitudinal retrospective cohort study of children with controlled blood HIV replication.

METHODS

Children (N = 213; 57% girls) started ART at less than 3 years of age, had neurodevelopmental assessments (cognition, attention/impulsivity, motor proficiency, global executive functions) at 5-11 years, and achieved controlled viremia (HIV-1 RNA <400 copies/ml for ≥9 months before initial assessment). Twenty-three plasma biomarkers were measured at onset of controlled viremia, week 0 (first neurodevelopmental assessment), and week 48 (second neurodevelopmental assessment). Factor analysis was conducted at each time point. Multivariable linear regressions assessed associations between factors and neurodevelopmental scores.

RESULTS

Median age at week 0 was 7.0 years. Eighteen biomarkers loaded on six factors: a (L-10, IFNγ, IFNα2, IL-1β, IL-6, IP-10, TNFα); B (sCD163, sICAM-1, sVCAM-1, CRP); C (sE-selectin, sP-selectin); D [MIP-1β, vascular endothelial growth factor (VEGF)-A]; E (sCD14, CRP); and F (CX3CL1, MCP-1). Higher factor B scores were consistently associated with worse cognition and attention/impulsivity, and higher factor D scores with better attention/impulsivity.

CONCLUSION

These results suggest a detrimental effect of increased endothelial cell activation (sICAM-1, sVCAM-1) and monocyte/macrophage scavenger function (sCD163) and a beneficial effect of increased CCR5 ligand and HIV entry blocker MIP-1β and angiogenesis stimulant-VEGF concentrations on the neurodevelopment of children with PHIV. The model that emerges is of vascular inflammation leading to neurodevelopmental deficits. The role of persistent HIV replication in the central nervous system also needs to be further explored.

Simulations of Glomerular Shear and Hoop Stresses in Diabetes, Hypertension, and Reduced Renal Mass using a Network Model of a Rat Glomerulus

A novel anatomically accurate model of rat glomerular filtration is used to quantify shear stresses on the glomerular capillary endothelium and hoop stresses on the glomerular capillary walls. Plasma, erythrocyte volume, and plasma protein mass are distributed at network nodes using pressure differentials calculated taking into account volume loss to filtration, improving on previous models which only took into account blood apparent viscosity in calculating pressures throughout the network. Filtration is found to be heterogeneously distributed throughout the glomerular capillary network and is determined by concentration of plasma proteins and surface area of the filtering capillary segments. Hoop stress is primarily concentrated near the afferent arteriole, whereas shear stress is concentrated near the efferent arteriole. Using parameters from glomerular micropuncture studies, conditions of diabetes mellitus (DM), 5/6‐Nephrectomy (5/6‐Nx), and Angiotensin II‐induced hypertension (HTN) are simulated and compared to their own internal controls to assess the changes in mechanical stresses. Hoop stress is increased in all three conditions, while shear stress is increased in 5/6‐Nx, decreased in HTN, and maintained at control levels in DM by the hypertrophic response of the glomerular capillaries. The results indicate that these alterations in mechanical stresses and the consequent release of cytokines by or injury of the glomerular cells may play a significant role in the progression of glomerulopathy in these disease conditions.

Editorial: Understanding molecular interactions that underpin vascular mechanobiology

Cells are exposed to a variety of mechanical forces in their daily lives, especially endothelial cells that are stretched from vessel distention and are exposed to hemodynamic shear stress from a blood flow. Exposure to excessive forces can induce a disease, but the molecular details on how these cells perceive forces, transduce them into biochemical signals and genetic events, i.e., mechanotransduction, and integrate them into physiological or pathological changes remain unclear. However, seminal studies in endothelial cells over the past several decades have begun to elucidate some of these signals. These studies have been highlighted in APL Bioengineering and elsewhere, describing a complex temporal pattern where forces are sensed immediately by ion channels and force-dependent conformational changes in surface proteins, followed by biochemical cascades, cytoskeletal contraction, and nuclear remodeling that can affect long-term changes in endothelial morphology and fate. Key examples from the endothelial literature that have established these pathways include showing that integrins and Flk-1 or VE-cadherin act as shear stress transducers, activating downstream proteins such as Cbl and Nckβ or Src, respectively. In this Editorial, we summarize a recent literature highlighting these accomplishments, noting the engineering tools and analysis methods used in these discoveries while also highlighting unanswered questions.

Anemia Is a Risk Factor for the Development of Ischemic Stroke and Post-Stroke Mortality

BACKGROUND

anemia is known to be a risk factor for developing ischemic stroke in long-term follow-up studies, and it is also known to increase the risk of death in ischemic stroke patients. We aimed to determine the association of anemia with the risk of ischemic stroke and the risk of death after ischemic stroke.

METHODS

The study included patients from National Health Insurance Service cohort, from January 2005 to December 2015. Anemia patients were defined as those with confirmed diagnostic codes and related medications in the sample cohort, and patients under the age of 18 were excluded. To perform a comparative analysis with the control group, twice as many patients were extracted by propensity score matching. The effects of anemia on the development of ischemic stroke were analyzed.

RESULTS

A total of 58,699 patients were newly diagnosed with anemia during the study period. In anemia group, the rate of ischemic stroke occurring within 1 year was 0.550%, and the rate was 0.272% in the control group. The odds ratio of anemia related to ischemic stroke was 1.602 (95% confidence intervals (CI) 1.363-1.883). During the follow-up period, 175 out of 309 (56.6%) died in anemia group, and 130 out of 314 (41.4%) died in control group. The anemia group showed a higher risk of death than the control group (Hazard ratio 1.509, 95% CI 1.197-1.902).

CONCLUSION

Analysis of the nationwide health insurance data revealed that anemia is one of the risk factors for the development of ischemic stroke, and also an independent prognostic factor affecting post-stroke mortality.

Shear forces induce ICAM-1 nanoclustering on endothelial cells that impact on T-cell migration

The leukocyte-specific β₂-integrin LFA-1 and its ligand ICAM-1, expressed on endothelial cells (ECs), are involved in the arrest, adhesion, and transendothelial migration of leukocytes. Although the role of mechanical forces on LFA-1 activation is well established, the impact of forces on its major ligand ICAM-1 has received less attention. Using a parallel-plate flow chamber combined with confocal and super-resolution microscopy, we show that prolonged shear flow induces global translocation of ICAM-1 on ECs upstream of flow direction. Interestingly, shear forces caused actin rearrangements and promoted actin-dependent ICAM-1 nanoclustering before LFA-1 engagement. T cells adhered to mechanically prestimulated ECs or nanoclustered ICAM-1 substrates developed a promigratory phenotype, migrated faster, and exhibited shorter-lived interactions with ECs than when adhered to non mechanically stimulated ECs or to monomeric ICAM-1 substrates. Together, our results indicate that shear forces increase ICAM-1/LFA-1 bonds because of ICAM-1 nanoclustering, strengthening adhesion and allowing cells to exert higher traction forces required for faster migration. Our data also underscore the importance of mechanical forces regulating the nanoscale organization of membrane receptors and their contribution to cell adhesion regulation.

Unveiling the CHO surfaceome: Identification of cell surface proteins reveals cell aggregation-relevant mechanisms

Chinese hamster ovary (CHO) suspension cells are the main production hosts for biopharmaceuticals. For the improvement of production processes, it is essential to understand the interaction between CHO cells and their microenvironment. While the cellular membrane is the crucial surface barrier between the inner and outer cell compartments, the subgroup of cell surface proteins (surfaceome) is of particular interest due to its potential to react to external factors and initiate cell communication and interaction pathways. Therefore, the CHO surfaceome was explored for the first time by enriching exposed N-glycosylated membrane proteins before tandem mass spectrometry (MS/MS) analyses, identifying a total of 449 surface proteins, including 34 proteins specific for production cells. Functional annotation and classification located most proteins to the cell surface belonging mainly to the protein classes of receptors, enzymes, and transporters. In addition, adhesion molecules as cadherins, integrins, Ig superfamily and extracellular matrix (ECM) proteins as collagens, laminins, thrombospondin, fibronectin, and tenascin were significantly enriched, which are involved in mechanisms for the formation of cell junctions, cell-cell and cell-ECM adhesion as focal adhesions. As cell adhesion and aggregation counteracts scalable production of biopharmaceuticals, experimental validation confirmed differential expression of integrin β1 (ITGB1) and β3, CD44, laminin, and fibronectin on the surface of aggregation-prone CHO production cells. The subsequent modulation of the central interaction protein ITGB1 by small interfering RNA knockdown substantially counteracted cell aggregation pointing toward novel engineering routes for aggregation reduction in biopharmaceutical production cells and exemplifying the potential of the surfaceome for specified engineering strategies.

Mechanotransduction-on-chip: vessel-chip model of endothelial YAP mechanobiology reveals matrix stiffness impedes shear response

Endothelial mechanobiology is a key consideration in the progression of vascular dysfunction, including atherosclerosis. However mechanistic connections between the clinically associated physical stimuli, vessel stiffness and shear stress, and how they interact to modulate plaque progression remain incompletely characterized. Vessel-chip systems are excellent candidates for modeling vascular mechanobiology as they may be engineered from the ground up, guided by the mechanical parameters present in human arteries and veins, to recapitulate key features of the vasculature. Here, we report extensive validation of a vessel-chip model of endothelial yes-associated protein (YAP) mechanobiology, a protein sensitive to both matrix stiffness and shearing forces and, importantly, implicated in atherosclerotic progression. Our model captures the established endothelial mechanoresponse, with endothelial alignment, elongation, reduction of adhesion molecules, and YAP cytoplasmic retention under high laminar shear. Conversely, we observed disturbed morphology, inflammation, and nuclear partitioning under low, high, and high oscillatory shear. Examining targets of YAP transcriptional co-activation, connective tissue growth factor (CTGF) is strongly downregulated by high laminar shear, whereas it is strongly upregulated by low shear or oscillatory flow. Ankyrin repeat domain 1 (ANKRD1) is only upregulated by high oscillatory shear. Verteporfin inhibition of YAP reduced the expression of CTGF but did not affect ANKRD1. Lastly, substrate stiffness modulated the endothelial shear mechanoresponse. Under high shear, softer substrates showed the lowest nuclear localization of YAP whereas stiffer substrates increased nuclear localization. Low shear strongly increased nuclear localization of YAP across stiffnesses. Together, we have validated a model of endothelial mechanobiology and describe a clinically relevant biological connection between matrix stiffness, shear stress, and endothelial activation via YAP mechanobiology.

Label-free tracking of whole-cell response on RGD functionalized surfaces to varied flow velocities generated by fluidic rotation

Fluidic flow plays important roles in colloid and interface sciences. Measuring adsorption, aggregation processes and living cell behavior under a fluidic environment with varied flow velocities in a parallel and high-throughput manner remains to be a challenging task. Here a method is introduced to monitor cell response to well-defined flow with varied velocities over an array of label-free resonant waveguide grating (RWG) based optical biosensors. The arrangement consists of a circular well with an array of biosensors at the bottom surface. By rotating the liquid over the biosensor array using a magnetic stirrer bar, flow velocities from zero to a predefined maximum can be easily established over different locations within the biosensor array as characterized in detail by numerical simulations. Cell adhesion and detachment measurements on an Arg-Gly-Asp (RGD) peptide functionalized surface were performed to demonstrate i) measurements at a wide range of simultaneous flow velocities over the same interface; ii) the possibility of parallel measurements at the same flow conditions in one run; and iii) the simple tuning of the employed range of flow velocities. Our setup made it possible to analyze the magnitude and rate of cell detachment at various flow velocities in parallel and determine the critical velocity and force where cells start to detach from the RGD motif displaying biomimetic surface. Furthermore, cellular response to simultaneous mechanical (flow) and chemical stimulation was also investigated using trypsin as a model. This study opens a new possibility to investigate interface phenomena under predefined and conveniently varied flow conditions.

Lymphatic Valves Separate Lymph Flow Into a Central Stream and a Slow-Moving Peri-Valvular Milieu

The lymphatic system plays a pivotal role in the transport of fats, waste, and immune cells, while also serving as a metastatic route for select cancers. Using live imaging and particle tracking, we experimentally characterized the lymph flow field distal from the inguinal lymph node in the vicinity of normal bileaflet and malformed unileaflet intraluminal valves. Particle tracking experiments demonstrated that intraluminal lymphatic valves concentrate higher velocity lymph flow in the center of the vessel, while generating adjacent perivalvular recirculation zones. The recirculation zones are characterized by extended particle residence times and low wall shear stress (WSS) magnitudes in comparison to the rest of the lymphangion. A malformed unileaflet valve skewed lymph flow toward the endothelium on the vessel wall, generating a stagnation point and a much larger recirculation zone on the opposite wall. These studies define physical consequences of bileaflet and unileaflet intraluminal lymphatic valves that affect lymph transport and the generation of a heterogeneous flow field that affects the lymphatic endothelium nonuniformly. The characterized flow fields were recreated in vitro connecting different flow environments present in the lymphangion to a lymphatic endothelial cell (LEC) pro-inflammatory phenotype. Unique and detailed insight into lymphatic flow is provided, with potential applications to a variety of diseases that affect lymph transport and drug delivery.

Flow Rate Affects Nanoparticle Uptake into Endothelial Cells

Nanoparticles are commonly administered through systemic injection, which exposes them to the dynamic environment of the bloodstream. Injected nanoparticles travel within the blood and experience a wide range of flow velocities that induce varying shear rates to the blood vessels. Endothelial cells line these vessels, and have been shown to uptake nanoparticles during circulation, but it is difficult to characterize the flow-dependence of this interaction in vivo. Here, a microfluidic system is developed to control the flow rates of nanoparticles as they interact with endothelial cells. Gold nanoparticle uptake into endothelial cells is quantified at varying flow rates, and it is found that increased flow rates lead to decreased nanoparticle uptake. Endothelial cells respond to increased flow shear with decreased ability to uptake the nanoparticles. If cells are sheared the same way, nanoparticle uptake decreases as their flow velocity increases. Modifying nanoparticle surfaces with endothelial-cell-binding ligands partially restores uptake to nonflow levels, suggesting that functionalizing nanoparticles to bind to endothelial cells enables nanoparticles to resist flow effects. In the future, this microfluidic system can be used to test other nanoparticle-endothelial cell interactions under flow. The results of these studies can guide the engineering of nanoparticles for in vivo medical applications.

Targeting functionalized nanoparticles to activated endothelial cells under high wall shear stress

Local inflammation of the endothelium is associated with a plethora of cardiovascular diseases. Vascular-targeted carriers (VTCs) have been advocated to provide focal effective therapeutics to these disease sites. Here, we examine the design of functionalized nanoparticles (NPs) as VTCs that can specifically localize at an inflamed vessel wall under pathological levels of high shear stress, associated for example with clinical (or in vivo) conditions of vascular narrowing and arteriogenesis. To test this, carboxylated fluorescent 200 nm polystyrene particles were functionalized with ligands to activated endothelium, that is, an E-selectin binding peptide (Esbp), an anti ICAM-1 antibody, or using a combination of both. The functionalized NPs were investigated in vitro using microfluidic models lined with inflamed (TNF-α stimulated) and control endothelial cells (EC). Specifically, their adhesion was monitored under different relevant wall shear stresses (i.e., 40-300 dyne/cm2) via real-time confocal microscopy. Experiments reveal a significantly higher specific adhesion of the examined functionalized NPs to activated EC for the window of examined wall shear stresses. Moreover, particle adhesion correlated with the surface coating density whereby under high surface coating (i.e., ~10,000 molecule/particle), shear-dependent particle adhesion increased significantly. Altogether, our results show that functionalized NPs can be designed to target inflamed endothelial cells under high shear stress. Such VTCs underscore the potential for attractive avenues in targeting drugs to vasoconstriction and arteriogenesis sites.

Sonoselective transfection of cerebral vasculature without blood-brain barrier disruption

Treatment of many pathologies of the brain could be improved markedly by the development of noninvasive therapeutic approaches that elicit robust, endothelial cell-selective gene expression in specific brain regions that are targeted under MR image guidance. While focused ultrasound (FUS) in conjunction with gas-filled microbubbles (MBs) has emerged as a noninvasive modality for MR image-guided gene delivery to the brain, it has been used exclusively to transiently disrupt the blood-brain barrier (BBB), which may induce a sterile inflammation response. Here, we introduce an MR image-guided FUS method that elicits endothelial-selective transfection of the cerebral vasculature (i.e., "sonoselective" transfection), without opening the BBB. We first determined that activating circulating, cationic plasmid-bearing MBs with pulsed low-pressure (0.1 MPa) 1.1-MHz FUS facilitates sonoselective gene delivery to the endothelium without MRI-detectable disruption of the BBB. The degree of endothelial selectivity varied inversely with the FUS pressure, with higher pressures (i.e., 0.3-MPa and 0.4-MPa FUS) consistently inducing BBB opening and extravascular transfection. Bulk RNA sequencing analyses revealed that the sonoselective low-pressure regimen does not up-regulate inflammatory or immune responses. Single-cell RNA sequencing indicated that the transcriptome of sonoselectively transfected brain endothelium was unaffected by the treatment. The approach developed here permits targeted gene delivery to blood vessels and could be used to promote angiogenesis, release endothelial cell-secreted factors to stimulate nerve regrowth, or recruit neural stem cells.

Epigenetic regulators of the revascularization response to chronic arterial occlusion

Peripheral arterial disease (PAD) is the leading cause of lower limb amputation and estimated to affect over 202 million people worldwide. PAD is caused by atherosclerotic lesions that occlude large arteries in the lower limbs, leading to insufficient blood perfusion of distal tissues. Given the severity of this clinical problem, there has been long-standing interest in both understanding how chronic arterial occlusions affect muscle tissue and vasculature and identifying therapeutic approaches capable of restoring tissue composition and vascular function to a healthy state. To date, the most widely utilized animal model for performing such studies has been the ischaemic mouse hindlimb. Despite not being a model of PAD per se, the ischaemic hindlimb model does recapitulate several key aspects of PAD. Further, it has served as a valuable platform upon which we have built much of our understanding of how chronic arterial occlusions affect muscle tissue composition, muscle regeneration and angiogenesis, and collateral arteriogenesis. Recently, there has been a global surge in research aimed at understanding how gene expression is regulated by epigenetic factors (i.e. non-coding RNAs, histone post-translational modifications, and DNA methylation). Thus, perhaps not unexpectedly, many recent studies have identified essential roles for epigenetic factors in regulating key responses to chronic arterial occlusion(s). In this review, we summarize the mechanisms of action of these epigenetic regulators and highlight several recent studies investigating the role of said regulators in the context of hindlimb ischaemia. In addition, we focus on how these recent advances in our understanding of the role of epigenetics in regulating responses to chronic arterial occlusion(s) can inform future therapeutic applications to promote revascularization and perfusion recovery in the setting of PAD.

Using computational fluid dynamics (CFD) modeling to understand murine embryonic stem cell aggregate size and pluripotency distributions in stirred suspension bioreactors

Computational fluid dynamics (CFD) modeling can be applied to understand hydrodynamics in stirred suspension bioreactors, which can in turn affect cell viability, proliferation, pluripotency and differentiation. In this study, we developed a CFD model to determine the effects of average shear rates and turbulent eddies on the formation and growth of murine embryonic stem cell aggregates. We found a correlation between average eddy size and aggregate size, which depended on bioreactor agitation rates. By relating these computational and biological variables, CFD modeling can predict optimal agitation rates to grow embryonic stem cell aggregates in stirred suspension bioreactors. To examine the effect of hydrodynamics on pluripotency, mESCs cultured in bioreactors under various agitation rates were tested for SSEA-1, Sox-2, and Nanog expression. Cells maintained a minimum of 95% positive expression with no change in the intensity distribution pattern between the different bioreactor conditions. This indicates that the average level of pluripotency marker expression is independent of changes in the hydrodynamic profile and resulting aggregate size distribution. The findings here can be further extended to other cell types that grow as aggregates in stirred suspension bioreactors and offer important insights necessary to realize cell therapies.

Empagliflozin restores the integrity of the endothelial glycocalyx in vitro

The antihyperglycemic agent empagliflozin not only improves glycemic control but has also been associated with clinically meaningful reductions in cardiovascular events. Studies have shown that empagliflozin significantly reduces cardiovascular death and heart failure-associated hospitalizations. Given that endothelial dysfunction is closely linked with the pathogenesis of atherosclerotic cardiovascular disease, we hypothesized that the cardiovascular benefits observed with empagliflozin may be a result of its positive impact on the health of the endothelial glycocalyx (GCX), a critical component for the endothelium homeostasis. Human abdominal aortic endothelial cells (HAAECs) were either statically cultured or subjected to a steady wall shear stress of 10 dyne/cm². Empagliflozin (50 µM, 24 h) restored heparinase III-mediated GCX disruption and the normal mechanotransduction responses in GCX-compromised HAAECs while reducing the attachment of all-trans retinoic acid-transformed NB4 cells to HAAECs. The current body of work suggests that the cardioprotective properties previously reported for empagliflozin may in part be due to the ability of empagliflozin to preserve and restore the structural integrity of the GCX, which in turn helps to maintain vascular health by promoting an anti-inflammatory endothelium, in the presence of a pro-inflammatory environment. Further studies are needed to fully understand the mechanisms underlying the cardiovascular benefits of empagliflozin.

Deciphering Endothelial Dysfunction in the HIV-Infected Population

Cardiovascular disease (CVD), as a possible consequence of endothelial dysfunction, is prevalent among HIV-infected patients despite successful administration of antiretroviral drugs. This warrants the routine clinical assessment of endothelial function in HIV-positive patients to circumvent potential CVD events. Several different non-invasive strategies have been employed to assess endothelial function in clinical research studies yielding inconsistencies among these reports. This review summarises the different techniques used for assessing endothelial function, with a focus on proposed blood-based biomarkers, such as endothelial leukocyte adhesion molecule-1 (E-selectin), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWF), TNF-α, interleukin 6 (IL6) and soluble thrombomodulin (sTM). The identification of suitable blood-based biomarkers, especially those that can be measured using a point-of-care device, would be more applicable in under-resourced countries where the prevalence of HIV is high.

TNF-α-Induced YAP/TAZ Activity Mediates Leukocyte-Endothelial Adhesion by Regulating VCAM1 Expression in Endothelial Cells

YAP/TAZ, a transcriptional co-activator of Hippo pathway, has emerged as a central player in vessel homeostasis such as sprouting angiogenesis and vascular barrier stabilization, during development. However, the role of YAP/TAZ in pathological angiogenesis remains unclear. Here, we demonstrated that YAP/TAZ is a critical mediator in leukocyte-endothelial adhesion induced by the vascular inflammatory cytokine TNF-α. YAP/TAZ was dephosphorylated, translocated from the cytosol to the nucleus, and activated by TNF-α in endothelial cells. A specific inhibitor of Rho GTPases suppressed the TNF-α-induced dephosphorylation of YAP. Knockdown of YAP/TAZ using siRNA significantly reduced the expression of the leukocyte adhesion molecule VCAM1 induced by TNF-α. The adhesion of monocytes to endothelial cells was also markedly reduced by YAP/TAZ silencing. However, knockdown of YAP/TAZ did not affect TNF-α-induced NF-κB signaling. Overall, these results suggest that YAP/TAZ plays critical roles in regulating TNF-α-induced endothelial cell adhesive properties without affecting the NF-κB pathway, and implicate YAP/TAZ as a potential therapeutic target for treating inflammatory vascular diseases.

Stress phase angle regulates differentiation of human adipose-derived stem cells toward endothelial phenotype

Endothelial cells are subjected to cyclic shear by pulsatile blood flow and pressures due to circumferential stresses. Although most of the researches on this topic have considered the effects of these two biomechanical forces separately or concurrently, few studies have noticed the interaction of these cyclic loadings on endothelial behavior. Negative temporal stress phase angle, defined by the phase lag between cyclic shear and tensile stresses, is an established parameter which is known to have substantial effects on blood vessel remodeling and progression of some serious cardiovascular diseases. In this research, intermittent shear and tensile stresses with different stress phase angle values were applied on human adipose stem cells (ASC). The expression level of three major endothelial-specific genes, elastic modulus of cells and cytoskeleton actin structure of cells were studied and compared among control and three test groups subjected to stress phase angle values at 0°, - 45°, and - 90°. Mechanical properties of ASCs were determined by atomic force microscopy and actin fiber structure was visualized by confocal imaging through Phalloidin staining. Results described a decrease in expression of FLK-1 and VE-cadherin and rise of vWF marker expression in case of higher negative stress phase angles. The Young's moduli of cells were significantly higher and cytoskeletal actin structure was more organized with higher thickness for all test samples subjected to combined stresses; however, these features were less magnificent for applied stress phase angles with higher negative values. The results confirmed significant effects of SPA on endothelial differentiation of mesenchymal stem cells.

MicroRNA-146a Regulates Perfusion Recovery in Response to Arterial Occlusion via Arteriogenesis

The growth of endogenous collateral arteries that bypass arterial occlusion(s), or arteriogenesis, is a fundamental shear stress-induced adaptation with implications for treating peripheral arterial disease. MicroRNAs (miRs) are key regulators of gene expression in response to injury and have strong therapeutic potential. In a previous study, we identified miR-146a as a candidate regulator of vascular remodeling. Here, we tested whether miR-146a regulates in vitro angiogenic endothelial cell (EC) behaviors, as well as perfusion recovery, arteriogenesis, and angiogenesis in response to femoral arterial ligation (FAL) in vivo. We found miR-146a inhibition impaired EC tube formation and migration in vitro. Following FAL, Balb/c mice were treated with a single, intramuscular injection of anti-miR-146a or scramble locked nucleic acid (LNA) oligonucleotides directly into the non-ischemic gracilis muscles. Serial laser Doppler imaging demonstrated that anti-miR-146a treated mice exhibited significantly greater perfusion recovery (a 16% increase) compared mice treated with scramble LNA. Moreover, anti-miR-146a treated mice exhibited a 22% increase in collateral artery diameter compared to controls, while there was no significant effect on in vivo angiogenesis or muscle regeneration. Despite exerting no beneficial effects on angiogenesis, the inhibition of mechanosensitive miR-146a enhances perfusion recovery after FAL via enhanced arteriogenesis.

Alternative RNA splicing in the endothelium mediated in part by Rbfox2 regulates the arterial response to low flow

Low and disturbed blood flow drives the progression of arterial diseases including atherosclerosis and aneurysms. The endothelial response to flow and its interactions with recruited platelets and leukocytes determine disease progression. Here, we report widespread changes in alternative splicing of pre-mRNA in the flow-activated murine arterial endothelium in vivo. Alternative splicing was suppressed by depletion of platelets and macrophages recruited to the arterial endothelium under low and disturbed flow. Binding motifs for the Rbfox-family are enriched adjacent to many of the regulated exons. Endothelial deletion of Rbfox2, the only family member expressed in arterial endothelium, suppresses a subset of the changes in transcription and RNA splicing induced by low flow. Our data reveal an alternative splicing program activated by Rbfox2 in the endothelium on recruitment of platelets and macrophages and demonstrate its relevance in transcriptional responses during flow-driven vascular inflammation.

Allopurinol protects human glomerular endothelial cells from high glucose-induced reactive oxygen species generation, p53 overexpression and endothelial dysfunction

PURPOSE

Mitochondrial reactive oxygen species (ROS) overproduction in capillary endothelial cells is a prerequisite for the development of diabetic nephropathy. Inhibition of xanthine oxidase, another ROS generator, ameliorates experimental diabetic nephropathy. To test the hypothesis that the initial high glucose-induced ROS production by the mitochondria activates xanthine oxidase, which afterward remains as the major source of ROS, we cultured primary human glomerular endothelial cells (GEnC) under normal or high-glucose conditions, with or without the xanthine oxidase inhibitor allopurinol.

METHODS

ROS generation and nitric oxide synthase (NOS) activity were assessed by chemiluminescence or colorimetrically. Levels of intercellular adhesion molecule 1 (ICAM-1), p53 and phosphorylated p53 (p-p53) were assessed by western blotting.

RESULTS

Allopurinol prevented high glucose-induced ROS generation indicating that xanthine oxidase is the major source of ROS. Allopurinol protected GEnC from endothelial dysfunction since it prevented the high glucose-induced decrease in NOS activity and increase in ICAM-1 expression. Allopurinol reduced p53 and p-p53 levels induced by high glucose suggesting an axis of xanthine oxidase-derived ROS, DNA damage, p53 stabilization and endothelial dysfunction that may contribute to the pathogenesis of diabetic nephropathy.

CONCLUSIONS

Allopurinol protects GEnC from high glucose-induced ROS generation, p53 overexpression and endothelial dysfunction. These data provide a pathogenetic mechanism that supports the results of experimental and clinical studies about the beneficial effect of xanthine oxidase inhibitors on the development of diabetic nephropathy.

Chronic administration of mitochondrion-targeted peptide SS-31 prevents atherosclerotic development in ApoE knockout mice fed Western diet

Background

Oxidative stress and inflammatory factors are deeply involved in progression of atherosclerosis. Mitochondrion-targeted peptide SS-31, selectively targeting to mitochondrial inner membrane reacting with cardiolipin, has been reported to inhibit ROS generation and mitigate inflammation. The present study was designed to investigate whether SS-31 could suppress the development of atherosclerosis in vivo.

Methods

Male ApoE^-/- mice (8 weeks old) fed with Western diet were treated with normal saline or SS-31 (1 mg/kg/d or 3 mg/kg/d) through subcutaneous injection for 12 weeks. Oil Red O staining was performed to evaluate area and sizes of the plaques. DHE staining and immunohistochemical staining of 8-OHDG was performed to assess the oxidative stress. The aorta ATP contents were assessed by the ATP bioluminescence assay kit. Immunohistochemical staining of CD68 and α-SMA and Masson’s trichrome staining were performed to evaluate the composition of atherosclerotic plaque. Biochemical assays were performed to determine the protein level and activity of superoxide dismutase (SOD). The levels of CD36, LOX-1 and ABCA1 were immunohistochemically and biochemically determined to evaluate the cholesterol transport in aorta and peritoneal macrophages. Inflammatory factors, including ICAM-1, MCP-1, IL-6 and CRP in serum, were detected through ELISA.

Results

SS-31 administration reduced the area and sizes of western diet-induced atherosclerotic plaques and changed the composition of the plaques in ApoE^-/- mice. Oxidative stress was suppressed, as evidenced by the reduced DHE stain, down-regulated 8-OHDG expression, and increased SOD activity after chronic SS-31 administration. Moreover, systemic inflammation was ameliorated as seen by decreasing serum ICAM-1, MCP-1, and IL-6 levels. Most importantly, SS-31 administration inhibited cholesterol influx by down-regulating expression of CD36 and LOX-1 to prevent lipid accumulation to further suppress the foam cell formation and atherosclerotic progression.

Conclusion

Administration of SS-31 prevents against atherosclerotic formation in ApoE^-/- mice suggesting that SS-31 might be considered to be a potential drug to prevent atherosclerotic progression.

In vivo imaging of endothelial cell adhesion molecule expression after radiosurgery in an animal model of arteriovenous malformation

Focussed radiosurgery may provide a means of inducing molecular changes on the luminal surface of diseased endothelium to allow targeted delivery of novel therapeutic compounds. We investigated the potential of ionizing radiation to induce surface expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) on endothelial cells (EC) in vitro and in vivo, to assess their suitability as vascular targets in irradiated arteriovenous malformations (AVMs). Cultured brain microvascular EC were irradiated by linear accelerator at single doses of 0, 5, 15 or 25 Gy and expression of ICAM-1 and VCAM-1 measured by qRT-PCR, Western, ELISA and immunocytochemistry. In vivo, near-infrared (NIR) fluorescence optical imaging using Xenolight 750-conjugated ICAM-1 or VCAM-1 antibodies examined luminal biodistribution over 84 days in a rat AVM model after Gamma Knife surgery at a single 15 Gy dose. ICAM-1 and VCAM-1 were minimally expressed on untreated EC in vitro. Doses of 15 and 25 Gy stimulated expression equally; 5 Gy was not different from the unirradiated. In vivo, normal vessels did not bind or retain the fluorescent probes, however binding was significant in AVM vessels. No additive increases in probe binding were found in response to radiosurgery at a dose of 15 Gy. In summary, radiation induces adhesion molecule expression in vitro but elevated baseline levels in AVM vessels precludes further induction in vivo. These molecules may be suitable targets in irradiated vessels without hemodynamic derangement, but not AVMs. These findings demonstrate the importance of using flow-modulated, pre-clinical animal models for validating candidate proteins for vascular targeting in irradiated AVMs.

Strategies for Selecting Membrane Protein-Specific Antibodies using Phage Display with Cell-Based Panning

Membrane proteins are attractive targets for monoclonal antibody (mAb) discovery and development. Although several approved mAbs against membrane proteins have been isolated from phage antibody libraries, the process is challenging, as it requires the presentation of a correctly folded protein to screen the antibody library. Cell-based panning could represent the optimal method for antibody discovery against membrane proteins, since it allows for presentation in their natural conformation along with the appropriate post-translational modifications. Nevertheless, screening antibodies against a desired antigen, within a selected cell line, may be difficult due to the abundance of irrelevant organic molecules, which can potentially obscure the antigen of interest. This review will provide a comprehensive overview of the different cell-based phage panning strategies, with an emphasis placed on the optimisation of four critical panning conditions: cell surface antigen presentation, non-specific binding events, incubation time, and temperature and recovery of phage binders.

Tryptophan depletion under conditions that imitate insulin resistance enhances fatty acid oxidation and induces endothelial dysfunction through reactive oxygen species-dependent and independent pathways

In atherosclerosis-associated pathologic entities characterized by malnutrition and inflammation, L-tryptophan (TRP) levels are low. Insulin resistance is an independent cardiovascular risk factor and induces endothelial dysfunction by increasing fatty acid oxidation. It is also associated with inflammation and low TRP levels. Low TRP levels have been related to worse cardiovascular outcome. This study evaluated the effect of TRP depletion on endothelial dysfunction under conditions that imitate insulin resistance. Fatty acid oxidation, harmful pathways due to increased fatty acid oxidation, and endothelial dysfunction were assessed in primary human aortic endothelial cells cultured under normal glucose, low insulin conditions in the presence or absence of TRP. TRP depletion activated general control non-derepressible 2 kinase and inhibited aryl hydrocarbon receptor. It increased fatty acid oxidation by increasing expression and activity of carnitine palmitoyltransferase 1. Elevated fatty acid oxidation increased the formation of reactive oxygen species (ROS) triggering the polyol and hexosamine pathways, and enhancing protein kinase C activity and methylglyoxal production. TRP absence inhibited nitric oxide synthase activity in a ROS-dependent way, whereas it increased the expression of ICAM-1 and VCAM-1 in a ROS independent and possibly p53-dependent manner. Thus, TRP depletion, an amino acid whose low levels have been related to worse cardiovascular outcome and to inflammatory atherosclerosis-associated pathologic entities, under conditions that imitate insulin resistance enhances fatty acid oxidation and induces endothelial dysfunction through ROS-dependent and independent pathways. These findings may offer new insights at the molecular mechanisms involved in accelerated atherosclerosis that frequently accompanies malnutrition and inflammation.

Divergent endothelial function but similar platelet microvesicle responses following eccentric and concentric cycling at a similar aerobic power output

Endothelial function and microvesicle concentration changes after acute bouts of continuous eccentric exercise have not been assessed previously nor compared with concentric exercise at similar aerobic power outputs. This method of training may be useful among some clinical populations, but acute responses are not well described. As such, 12 healthy males completed 2 experimental sessions of either 45 min of eccentric or concentric cycling at a matched aerobic power output below the ventilatory threshold. Brachial artery vascular function was assessed throughout 5 min of forearm ischemia and 3 min thereafter, before and at 5 and 40 min of recovery following each exercise session [flow-mediated dilation (FMD)]. Venous blood samples were acquired before each vascular function assessment. FMD significantly decreased after eccentric cycling by 40 min of recovery (P < 0.05), but was unaltered after concentric exercise. No differences in peak hyperemic blood flow velocity occurred neither between modalities nor at any time point (P > 0.05). Platelet-derived microvesicles increased by ~20% after both exercise modalities (P < 0.05) while endothelial-derived microvesicles were unchanged (P > 0.05). Moderate relationships with cardiac output, a surrogate for shear stress, and norepinephrine were apparent (P < 0.05), but there were no relationships with inflammatory or acute phase proteins. In summary, eccentric endurance exercise induced macrovascular endothelial dysfunction; however, endothelial activation determined by endothelial microvesicles did not occur suggesting that this modality may induce oxidative stress but no significant endothelial damage. In addition, the increase in platelet microvesicle concentrations may induce beneficial microvascular adaptations as suggested by previous research.NEW & NOTEWORTHY Continuous eccentric cycling exercise induces substantial skeletal muscle, tendon, and bone strain providing a potentially beneficial stimulus among clinical populations. This modality also induces temporary endothelial dysfunction but no apparent damage or activation of the endothelium indicated by microvesicle production, whereas proangiogenic platelet microvesicles are released similarly following both concentric and eccentric cycling and may relate to the shear stress and catecholamine response to exercise.

Microvesicles Derived from Inflammation-Challenged Endothelial Cells Modulate Vascular Smooth Muscle Cell Functions

Purpose: Microvesicles (MV) can modulate the function of recipient cells by transferring their contents. Our previous study highlighted that MV released from tumor necrosis factor-α (TNF-α) plus serum deprivation (SD)-stimulated endothelial progenitor cells, induce detrimental effects on endothelial cells. In this study, we investigated the potential effects of endothelial MV (EMV) on proliferation, migration, and apoptosis of human brain vascular smooth cells (HBVSMC).

Methods: EMV were prepared from human brain microvascular endothelial cells (HBMEC) cultured in a TNF-α plus SD medium. RNase-EMV were made by treating EMV with RNase A for RNA depletion. The proliferation, apoptosis and migration abilities of HBVSMC were determined after co-culture with EMV or RNase-EMV. The Mek1/2 inhibitor, PD0325901, was used for pathway analysis. Western blot was used for analyzing the proteins of Mek1/2, Erk1/2, phosphorylation Erk1/2, activated caspase-3 and Bcl-2. The level of miR-146a-5p was measured by qRT-PCR.

Results: (1) EMV significantly promoted the proliferation and migration of HBVSMC. The effects were accompanied by an increase in Mek1/2 and p-Erk1/2, which could be abolished by PD0325901; (2) EMV decreased the apoptotic rate of HBVSMC by approximately 35%, which was accompanied by cleaved caspase-3 down-regulation and Bcl-2 up-regulation; (3) EMV increased miR-146a-5p level in HBVSMC by about 2-folds; (4) RNase-treated EMV were less effective than EMV on HBVSMC activities and miR-146a-5p expression.

Conclusion: EMV generated under inflammation challenge can modulate HBVSMC function and fate via their carried RNA. This is associated with activation of theMek1/2/Erk1/2 pathway and caspase-3/Bcl-2 regulation, during which miR-146a-5p may play an important role. The data suggest that EMV derived from inflammation-challenged endothelial cells are detrimental to HBVSMC homeostatic functions, highlighting potential novel therapeutic targets for vascular diseases.

Chronic Venous Insufficiency and the Therapeutic Effects of Daflon 500 mg

Chronic venous insufficiency is linked to venous hypertension and forces of shear stress on the endothelium. Venous hypertension depends upon two forces: the weight of a column of blood from the right atrium transmitted through the valveless vena cava and iliac veins to the femoral vein, and pressure generated by contracting skeletal muscles of the leg transmitted through failed perforating veins. When valve failure occurs in superficial axial veins and perforating veins, the venous pressure in the veins and venules of the skin and subcutaneous tissue is raised. The skin changes in chronic venous insufficiency are directly related to the severity of the venous hypertension. Also, pathologic changes in the valves are linked to venous hypertension and leukocyte infiltration and activation. It is hypothesized that acute venous pressure elevations cause a shift in the venous hemodynamics with changes in wall shear stress. This initiates the inflammatory cascade. Daflon 500 mg ameliorates the effects of chronic inflammation. In randomized trials, 60 days of therapy with Daflon at a dosage of 500 mg 2 tablets daily was effective, in addition to elastic compression, in accelerating venous ulcer healing. Because venous insufficiency is linked to venous hypertension and an inflammatory reaction, it appears that Daflon 500 mg 2 tablets daily shows a great potential for accomplishing blockade of the inflammatory cascade.

Platelets modulate endothelial cell response to dynamic shear stress through PECAM-1

INTRODUCTION

Both vascular endothelial cells and platelets are sensitive to blood flow induced shear stress. We have recently reported that platelet-endothelial cell interaction could greatly affect platelet activation under flow. In the present study, we aimed to investigate how platelet-endothelial cell interaction affected endothelial cell inflammatory responses under flow.

MATERIALS AND METHODS

Human coronary artery endothelial cells were exposed to normal or low pulsatile shear stress with or without the presence of platelets. Following shear exposure, endothelial cell ICAM-1 expression was measured using ELISA, Western blot and PCR; cell surface PECAM-1 expression/phosphorylation was measured using ELISA. Platelet adhesion to endothelial cells was quantified using immunofluorescence microscopy. To determine the role of PECAM-1 in platelet-endothelial cell interaction, endothelial cell PECAM-1 expression was suppressed using siRNA.

RESULTS

Pathological low shear stress induced a significant increase in endothelial cell ICAM-1 expression, at both protein and mRNA levels. Platelet adhesion to endothelial cells increased significantly under low shear stress, co-localizing with PECAM-1 at endothelial cell junctions. The presence of platelets inhibited low shear stress-induced ICAM-1 upregulation. When endothelial cell PECAM-1 expression was suppressed, platelet adhesion to endothelial cells under low shear stress decreased significantly; endothelial cell ICAM-1 expression was not affected by shear stress, with or without platelets.

CONCLUSIONS

These results suggested that PECAM-1 could mediate platelet adhesion to endothelial cells under shear stress. Platelets binding to endothelial cells interfered with endothelial cell mechanotransduction through PECAM-1, affecting endothelial cell inflammatory responses towards pathological shear flow.