The Importance of Mechanical Forces for in vitro Endothelial Cell Biology

Blood and lymphatic vessels are lined by endothelial cells which constantly interact with their luminal and abluminal extracellular environments. These interactions confer physical forces on the endothelium, such as shear stress, stretch and stiffness, to mediate biological responses. These physical forces are often altered during disease, driving abnormal endothelial cell behavior and pathology. Therefore, it is critical that we understand the mechanisms by which endothelial cells respond to physical forces. Traditionally, endothelial cells in culture are grown in the absence of flow on stiff substrates such as plastic or glass. These cells are not subjected to the physical forces that endothelial cells endure in vivo, thus the results of these experiments often do not mimic those observed in the body. The field of vascular biology now realize that an intricate analysis of endothelial signaling mechanisms requires complex in vitro systems to mimic in vivo conditions. Here, we will review what is known about the mechanical forces that guide endothelial cell behavior and then discuss the advancements in endothelial cell culture models designed to better mimic the in vivo vascular microenvironment. A wider application of these technologies will provide more biologically relevant information from cultured cells which will be reproducible to conditions found in the body.

Vascular permeability in retinopathy is regulated by VEGFR2 Y949 signaling to VE-cadherin

Edema stemming from leaky blood vessels is common in eye diseases such as age-related macular degeneration and diabetic retinopathy. Whereas therapies targeting vascular endothelial growth factor A (VEGFA) can suppress leakage, side-effects include vascular rarefaction and geographic atrophy. By challenging mouse models representing different steps in VEGFA/VEGF receptor 2 (VEGFR2)-induced vascular permeability, we show that targeting signaling downstream of VEGFR2 pY949 limits vascular permeability in retinopathy induced by high oxygen or by laser-wounding. Although suppressed permeability is accompanied by reduced pathological neoangiogenesis in oxygen-induced retinopathy, similarly sized lesions leak less in mutant mice, separating regulation of permeability from angiogenesis. Strikingly, vascular endothelial (VE)-cadherin phosphorylation at the Y685, but not Y658, residue is reduced when VEGFR2 pY949 signaling is impaired. These findings support a mechanism whereby VE-cadherin Y685 phosphorylation is selectively associated with excessive vascular leakage. Therapeutically, targeting VEGFR2-regulated VE-cadherin phosphorylation could suppress edema while leaving other VEGFR2-dependent functions intact.

The number of people with impaired vision and blindness is increasing in Western society due to the aging population and the increased prevalence of diabetes. This has led to eye diseases, such as age-related macular degeneration and diabetic retinopathy becoming more common. In both these eye diseases, new blood vessels grow in the retina – the light-sensitive part of the eye – to bring oxygen and nutrients to the tissue. However, these new blood vessels are leaky and allow molecules to leave the bloodstream and enter the retinal tissue. This causes the retina to swell and impair a person’s vision. The leaky blood supply also reduces the amount of oxygen that gets to the tissue, resulting in further damage to the retina.

When tissues experience low levels of oxygen, cells start making a protein called vascular endothelial growth factor (or VEGF for short). Whilst this protein is important for helping form new blood vessels, it also makes these vessels leaky. Current treatments for age-related macular degeneration and diabetic retinopathy decrease swelling in the eye by blocking the action of VEGF. However, these treatments also cause existing blood vessels and nerve cells to die, leading to irreversible damage. Now, Smith et al. have set out to find whether the effects of VEGF can be blocked without causing further damage to existing cells.

To investigate this possibility, the eyes and retinas of mice were treated with a laser or exposed to changing oxygen levels to create injuries that resembled human age-related macular degeneration and diabetic retinopathy. Each of the tested mice had specific mutations in proteins known to interact with VEGF. Fluorescent particles were injected into the bloodstream of the mice to assess how these different mutations affected blood vessel leakage: if fluorescent particles could no longer be detected outside the blood vessels, this suggested that the mutation had stopped the vessels from leaking. Further experiments showed these specific mutations affected leakage and did not prevent new blood vessels from forming.

In the future it will be important to see if drugs, rather than mutations, can also decrease the leakiness of blood vessels in the retina. Such chemical compounds could then be tested in mouse experiments. If successful, these drugs might be used to treat patients with age-related macular degeneration and diabetic retinopathy.

Administrative Data Research UK

ADR UK is helping to transform the way researchers access the UK's wealth of administrative data, enabling government policy to be informed by the best evidence available. Emma shares her insights into the ADR UK approach to making this happen, explaining why building trust is central to the ADR UK mission.

c-Src controls stability of sprouting blood vessels in the developing retina independently of cell-cell adhesion through focal adhesion assembly

Endothelial cell adhesion is implicated in blood vessel sprout formation, yet how adhesion controls angiogenesis, and whether it occurs via rapid remodeling of adherens junctions or focal adhesion assembly, or both, remains poorly understood. Furthermore, how endothelial cell adhesion is controlled in particular tissues and under different conditions remains unexplored. Here, we have identified an unexpected role for spatiotemporal c-Src activity in sprouting angiogenesis in the retina, which is in contrast to the dominant focus on the role of c-Src in the maintenance of vascular integrity. Thus, mice specifically deficient in endothelial c-Src displayed significantly reduced blood vessel sprouting and loss in actin-rich filopodial protrusions at the vascular front of the developing retina. In contrast to what has been observed during vascular leakage, endothelial cell-cell adhesion was unaffected by loss of c-Src. Instead, decreased angiogenic sprouting was due to loss of focal adhesion assembly and cell-matrix adhesion, resulting in loss of sprout stability. These results demonstrate that c-Src signaling at specified endothelial cell membrane compartments (adherens junctions or focal adhesions) control vascular processes in a tissue- and context-dependent manner.

Mapping the Potential of Zero Charge and Electrocatalytic Activity of Metal-Electrolyte Interface via a Grain-by-Grain Approach

Potential of zero charge (PZC) is a fundamental quantity that dictates the structure of the electrical double layer. Studies using single crystals suggest a polycrystalline surface should display an inhomogeneous distribution of PZC and electric field, which directly affects the electrochemical energy storage and conversion processes occurring at the electrode-electrolyte interface. Herein, we demonstrate the direct mapping of local PZC using scanning electrochemical cell microscopy (SECCM). The potential-dependent charging current upon the formation of the microscopic electrode-electrolyte interface is used to determine the PZC. Using polycrystalline Pt as a model system, correlative SECCM and electron backscatter diffraction (EBSD) images show the dependence of PZC on the local crystal grain orientation. The electrocatalytic activity can be mapped from the same SECCM experiment via local voltammetry, which demonstrates the variation of hydrogen evolution reaction (HER) activity across Pt grains. The method reported here can be readily applied to study other electrochemical interfaces, providing rich correlative information on the surface property and electrocatalytic activities.

Mapping the Nucleation of H2 Bubbles on Polycrystalline Pt via Scanning Electrochemical Cell Microscopy

Electrochemically generated bubbles are gaining increasing attention for their detrimental effects on the efficiency of electrocatalysis involving gaseous products, including hydrogen evolution reaction (HER). As a model system, bubble nucleation is also of fundamental interest. Herein, we report a single-entity approach to map the nucleation of H₂ bubbles on polycrystalline Pt via scanning electrochemical cell microscopy (SECCM). Individual H₂ bubbles (∼500 nm radius) are generated via HER in the attoliter electrochemical cell of an SECCM instrument. Nucleation and growth of a H₂ bubble results in a characteristic voltammetric peak current, which is related to the concentration and activation energy required for nucleation. By mapping the local voltammograms at various locations on the polycrystalline Pt, we found a heterogeneous distribution of energetics of nucleation for H₂ bubbles on the Pt surface. However, such heterogeneity is not correlated with crystal grains or grain boundaries.

Shear Stress and VE-Cadherin

Objective—

Vascular fusion represents an important mechanism of vessel enlargement during development; however, its significance in postnatal vessel enlargement is still unknown. During fusion, 2 adjoining vessels merge to share 1 larger lumen. The aim of this research was to identify the molecular mechanism responsible for vascular fusion.

Approach and Results—

We previously showed that both low shear stress and DAPT ( N -[ N -(3,5-difluorophenacetyl)-L-alanyl]- S -phenylglycine t-butyl ester) treatment in the embryo result in a hyperfused vascular plexus and that increasing shear stress levels could prevent DAPT-induced fusion. We, therefore, investigated vascular endothelial-cadherin (VEC) phosphorylation because this is a common downstream target of low shear stress and DAPT treatment. VEC phosphorylation increases after DAPT treatment and decreased shear stress. The increased phosphorylation occurred independent of the cleavage of the Notch intracellular domain. Increasing shear stress rescues hyperfusion by DAPT treatment by causing the association of the phosphatase vascular endothelial-protein tyrosine phosphatase with VEC, counteracting VEC phosphorylation. Finally, Src (proto-oncogene tyrosine-protein kinase Src) inhibition prevents VEC phosphorylation in endothelial cells and can rescue hyperfusion induced by low shear stress and DAPT treatment. Moesin, a VEC target that was previously reported to mediate endothelial cell rearrangement during lumenization, relocalizes to cell membranes in vascular beds undergoing hyperfusion.

Conclusions—

This study provides the first evidence that VEC phosphorylation, induced by DAPT treatment and low shear stress, is involved in the process of fusion during vascular remodeling.

Increased hippocampal tail volume predicts depression status and remission to anti-depressant medications in major depression

Studies of patients with major depressive disorder (MDD) have consistently reported reduced hippocampal volumes; however, the exact pattern of these volume changes in specific anatomical subfields and their functional significance is unclear. We sought to clarify the relationship between hippocampal tail volumes and (i) a diagnosis of MDD, and (ii) clinical remission to anti-depressant medications (ADMs). Outpatients with nonpsychotic MDD (n=202) based on DSM-IV criteria and a 17-item Hamilton Rating Scale for Depression (HRSD₁₇) score ⩾16 underwent pretreatment magnetic resonance imaging as part of the international Study to Predict Optimized Treatment for Depression (iSPOT-D). Gender-matched healthy controls (n=68) also underwent MRI scanning. An automated pipeline was used to objectively measure hippocampal subfield and whole brain volumes. Remission was defined as an HRSD₁₇ of ⩽7 following 8 weeks of randomized open-label treatment ADMs: escitalopram, sertraline or venlafaxine-extended release. After controlling for age and total brain volume, hippocampal tail volume was larger in the MDD cohort compared to control subjects. Larger hippocampal tail volume was positively related to clinical remission, independent of total hippocampal volume, total brain volume and age. These data provide convergent evidence of the importance of the hippocampus in the development or treatment of MDD. Hippocampal tail volume is proposed as a potentially useful biomarker of sensitivity to ADM treatment.

Non-syndromic bilateral ulnar aplasia with humero-radial synostosis and oligo-ectro-dactyly

Congenital anomalies of the upper limbs are rare and etiologically heterogeneous. Herein, we report a male infant with non-syndromic bilateral Type Vb ulnar longitudinal dysplasia with radiohumeral synostosis (apparent humeral bifurcation), and bilateral oligo-ectro-syndactyly who was born following an uncomplicated pregnancy, with no maternal use of prescription or illicit medication. Array CGH (60,000 probes) and chromosomal breakage analysis (DEB) were normal. Similar appearances have been reported in children exposed to thalidomide or cocaine, but sporadic patients have also been reported without a prior history of exposure to known teratogens.

Pharmacokinetic evaluation and safety of topical 1% morphine sulfate application on the healthy equine eye

OBJECTIVE

To determine if corneal epithelial cell integrity is detrimentally affected by short-term administration of 1.0% morphine sulfate. Additionally, we sought to determine if topical 1.0% morphine applied to the equine cornea would result in ocular or systemic absorption.

ANIMAL STUDIED

Six healthy horses.

PROCEDURE

Morphine sulfate (1.0%) was applied topically to one eye every four hours for 72 h before horses were euthanized. Serum samples were collected at varying time points during the study and aqueous and vitreous humor were collected immediately after euthanasia. Morphine quantification in serum, aqueous, and vitreous humor was performed by ELISA. Treated and control corneas were submitted for histopathology. Horses were monitored for adverse ocular and systemic effects throughout the study period.

RESULTS

All horses developed mild mucoid ocular discharge in the treated eye. One horse developed a fever during treatment. Morphine was detected in the aqueous humor of the treated eye for all horses with mean ± standard deviation of 165.18 ng/mL ± 87.69 ng/mL. Morphine was detected in vitreous humor of the treated eye of 5 of 6 horses with mean ± standard deviation of 4.87 ± 4.46 ng/mL. Morphine was detected in the serum of 5 of 6 horses at varying time points. Maximum systemic concentration reached in a single horse was 6.98 ng/mL. Corneal histopathology revealed no difference in microscopic appearance between morphine-treated and control corneas.

CONCLUSIONS

Topical administration of 1.0% morphine sulfate did not appear to cause any significant ocular or systemic adverse effects. Topical ophthalmic morphine application resulted in both ocular and systemic absorption.

Distance travelled to purchase alcohol and the mediating effect of price

OBJECTIVES

Little research has been done into the distance travelled by consumers to purchase alcohol, whether this is influenced by demographic characteristics or drinking levels of consumers, and the effect of price on purchase distance. This study aimed to explore distances drinkers were prepared to travel to purchase alcohol at on- and off-site outlets and how these decisions were affected by price discounting.

STUDY DESIGN

Online survey.

METHODS

The study, including 831 alcohol consumers aged 18 years and older living in Australian capital cities, was undertaken in 2012. The survey was used to gather data on the distances which participants anticipated that they usually travelled to purchase alcohol. The data provided insight into which factors influence where participants would choose to purchase alcohol and the possible effects of price discounts on purchase distance.

RESULTS

Most participants would choose to travel less than 10 km to purchase alcohol. Data indicated that price discounting might increase the purchase distance that most participants would be prepared to travel to purchase alcohol; this was more marked regarding off-site outlets and among high-risk drinking groups including young males and participants with risky drinking levels.

CONCLUSIONS

Price discounting affects hypothetical purchase distance choices, indicating the importance of price when implementing alcohol control policies. Purchase distance might be more affected by price discounting among consumers visiting off-site outlets, but less useful when exploring associations with on-site outlets.

Neoplasia in 125 donkeys (Equus asinus): literature review and a survey of five veterinary schools in the United States and Canada

A diagnosis of neoplasia was noted in 125 of 357 donkeys (35%) in our review of medical records from 5 veterinary schools in the United States and Canada. Equine sarcoid was the most common tumor in our study, accounting for 72% of all tumors and 82% of cutaneous tumors. Soft-tissue sarcomas were the second most common skin tumors. All other types of neoplasia were rare. Important differences in the occurrence of neoplasia in donkeys compared to horses included the rarity or absence of squamous cell carcinoma in any organ system and gray horse melanoma. Lymphosarcoma, the most common malignant tumor in horses, appears to be very rare in donkeys. We report several tumors in donkeys including melanocytoma, peripheral nerve sheath tumor, and gastrointestinal stromal tumor. Our data demonstrate commonalities as well as differences in neoplastic diseases of donkeys and horses. Understanding differences in carcinogenesis among these 2 closely related species can inform researchers pursuing pathogenic mechanisms of equine disease and inform veterinary diagnosticians regarding tumor prevalence.

Novel affinity binders for neutralization of vascular endothelial growth factor (VEGF) signaling

Angiogenesis denotes the formation of new blood vessels from pre-existing vasculature. Progression of diseases such as cancer and several ophthalmological disorders may be promoted by excess angiogenesis. Novel therapeutics to inhibit angiogenesis and diagnostic tools for monitoring angiogenesis during therapy, hold great potential for improving treatment of such diseases. We have previously generated so-called biparatopic Affibody constructs with high affinity for the vascular endothelial growth factor receptor-2 (VEGFR2), which recognize two non-overlapping epitopes in the ligand-binding site on the receptor. Affibody molecules have previously been demonstrated suitable for imaging purposes. Their small size also makes them attractive for applications where an alternative route of administration is beneficial, such as topical delivery using eye drops. In this study, we show that decreasing linker length between the two Affibody domains resulted in even slower dissociation from the receptor. The new variants of the biparatopic Affibody bound to VEGFR2-expressing cells, blocked VEGFA binding, and inhibited VEGFA-induced signaling of VEGFR2 over expressing cells. Moreover, the biparatopic Affibody inhibited sprout formation of endothelial cells in an in vitro angiogenesis assay with similar potency as the bivalent monoclonal antibody ramucirumab. This study demonstrates that the biparatopic Affibody constructs show promise for future therapeutic as well as in vivo imaging applications.

VEGFR2 pY949 signalling regulates adherens junction integrity and metastatic spread

The specific role of VEGFA-induced permeability and vascular leakage in physiology and pathology has remained unclear. Here we show that VEGFA-induced vascular leakage depends on signalling initiated via the VEGFR2 phosphosite Y949, regulating dynamic c-Src and VE-cadherin phosphorylation. Abolished Y949 signalling in the mouse mutant Vegfr2^Y949F/Y949F leads to VEGFA-resistant endothelial adherens junctions and a block in molecular extravasation. Vessels in Vegfr2^Y949F/Y949F mice remain sensitive to inflammatory cytokines, and vascular morphology, blood pressure and flow parameters are normal. Tumour-bearing Vegfr2^Y949F/Y949F mice display reduced vascular leakage and oedema, improved response to chemotherapy and, importantly, reduced metastatic spread. The inflammatory infiltration in the tumour micro-environment is unaffected. Blocking VEGFA-induced disassembly of endothelial junctions, thereby suppressing tumour oedema and metastatic spread, may be preferable to full vascular suppression in the treatment of certain cancer forms.

Signals through VEGF receptor 2 (VEGFR2) increase vascular permeability, promoting cancer progression. Here the authors show that a point mutation in VEGFR2 preventing its auto-phosphorylation leads to reduced metastatic spread and improved response to chemotherapy in tumor-bearing mice, without affecting tumor inflammation.

Geographical and temporal Understanding In place of Death in England (1984–2010): analysis of trends and associated factors to improve end-of-life Care (GUIDE_Care) – primary research

Background

Place of death (PoD) has been used as an outcome measure for end-of-life care. Analysis of variations in PoD can improve understanding about service users’ needs and thus better target health-care services.

Objectives

(1) To describe PoD in England by demographic, socioeconomic and temporal variables; (2) to determine how much of the variation in PoD can be explained by potential explanatory variables at the area level, and building on this to develop individual-level multivariable regression models; and (3) to evaluate factors associated with PoD and to construct risk assessment models to inform practice.

Methods

A population-based study of all registered deaths between 1984 and 2010 in England (n = 13,154,705). The outcome was the PoD. Explanatory variables included age, gender, cause of death (CoD), marital status, year of death, whether or not the death was in a holiday period (Christmas, Easter, New Year), season of death, the location of usual residence and area-level deprivation. The proportion of explained variation in PoD was estimated using the weighted aggregate-level linear regression. Factors associated with PoD were investigated using generalised linear models. The risk assessment models were constructed using the 2006–9 data; the performance was evaluated using the 2010 data.

Results

Hospital was the most common PoD in 2001–10 [overall 57.3%; range – cancer 46.1% to chronic obstructive pulmonary disease (COPD) 68.3%], followed by home [overall 19.0%; range – cerebrovascular disease (CBD) 6.7% to cardiovascular disease 27.4%] or care home (overall 17.2%; range – cancer 10.1% to neurological conditions 35.2%), depending on CoD. Over the period, the proportion of hospital deaths for people who died from non-cancer increased (57.1–61.2%) and care home deaths reduced (21.2% down to 20.0%); a reverse pattern was seen for those who died of cancer (hospital: reduced, 48.6–47.3%; care home: increased, 9.3–10.1%). Hospice deaths varied considerably by CoD (range – CBD 0.2% to cancer 17.1%), and increased slightly overall from 4.1% in 1993–2000 to 5.1% in 2001–10. Multivariable analysis found that hospital deaths for all causes combined were more likely for people aged 75+ years [proportion ratios (PRs) 0.863–0.962 vs. aged 25–54 years], those who lived in London (PRs 0.872–0.988 vs. North West), those who were divorced, single and widowed (PRs 0.992–1.001 vs. married), those who lived in more deprived areas (PRs 0.929–1.000 more deprived vs. less deprived) and those who died in autumn, winter or at New Year. We were able to develop risk assessment models but the areas under the receiver operating characteristic curve indicating poor predictive performance, ranging from 0.552 (COPD) to 0.637 (CBD).

Conclusions

Hospital remains the most common PoD, followed by home and care home. Hospices play an important role for people who died from cancer but little for other diseases. Place of death is strongly associated with the underlying CoD. The variation in PoD by region, age, marital status and area deprivation suggests that inequities exist, which services and clinical commissioning groups could seek to address.

Funding

The National Institute for Health Services and Delivery Research programme.

No socioeconomic inequalities in ovarian cancer survival within two randomised clinical trials

BACKGROUND

Ovarian cancer is the leading cause of death among cancers of the female genital tract, with poor outcomes despite chemotherapy. There was a persistent socioeconomic gradient in 1-year survival in England and Wales for more than 3 decades (1971-2001). Inequalities in 5-year survival persisted for more than 20 years but have been smaller for women diagnosed around 2000. We explored one possible explanation.

METHODS

We analysed data on 1406 women diagnosed with ovarian cancer during 1991-1998 and recruited to one of two randomised clinical trials. In the second International Collaborative Ovarian Neoplasm (ICON2) trial, women diagnosed between 1991 and 1996 were randomised to receive either the three-drug combination cyclophosphamide, doxorubicin and cisplatin (CAP) or single-agent carboplatin given at optimal dose. In the ICON3 trial, women diagnosed during 1995-1998 were randomised to receive either the same treatments as ICON2, or paclitaxel plus carboplatin.Relative survival at 1, 5 and 10 years was estimated for women in five categories of socioeconomic deprivation. The excess hazard of death over and above background mortality was estimated by fitting multivariable regression models with Poisson error structure and a dedicated link function in a generalised linear model framework, adjusting for the duration of follow-up and the confounding effects of age, Federation of Gynecology and Obstetrics (FIGO) stage and calendar period.

RESULTS

Unlike women with ovarian cancer in the general population, no statistically significant socioeconomic gradient was seen for women with ovarian cancer treated in the two randomised controlled trials. The deprivation gap in 1-year relative survival in the general population was statistically significant at -6.7% (95% CI (-8.1, -5.3)), compared with -3.6% (95% CI (-10.4, +3.2)) in the trial population.

CONCLUSIONS

Although ovarian cancer survival is significantly lower among poor women than rich women in England and Wales, there was no evidence of an association between socioeconomic deprivation and survival among women with ovarian cancer who were treated and followed up consistently in two well-conducted randomised controlled trials. We conclude that the persistent socioeconomic gradient in survival among women with ovarian cancer, at least for 1-year survival, may be due to differences in access to treatment and standards of care.