Highly integrated workflows for exploring cardiovascular conditions: Exemplars of precision medicine in Alzheimer's disease and aortic dissection.

For precision medicine to be implemented through the lens of in silico technology, it is imperative that biophysical research workflows offer insight into treatments that are specific to a particular illness and to a particular subject. The boundaries of precision medicine can be extended using multiscale, biophysics-centred workflows that consider the fundamental underpinnings of the constituents of cells and tissues and their dynamic environments. Utilising numerical techniques that can capture the broad spectrum of biological flows within complex, deformable and permeable organs and tissues is of paramount importance when considering the core prerequisites of any state-of-the-art precision medicine pipeline. In this work, a succinct breakdown of two precision medicine pipelines developed within two Virtual Physiological Human (VPH) projects are given. The first workflow is targeted on the trajectory of Alzheimer's Disease, and caters for novel hypothesis testing through a multicompartmental poroelastic model which is integrated with a high throughput imaging workflow and subject-specific blood flow variability model. The second workflow gives rise to the patient specific exploration of Aortic Dissections via a multi-scale and compliant model, harnessing imaging, computational fluid-dynamics (CFD) and dynamic boundary conditions. Results relating to the first workflow include some core outputs of the multiporoelastic modelling framework, and the representation of peri-arterial swelling and peri-venous drainage solution fields. The latter solution fields were statistically analysed for a cohort of thirty-five subjects (stratified with respect to disease status, gender and activity level). The second workflow allowed for a better understanding of complex aortic dissection cases utilising both a rigid-wall model informed by minimal and clinically common datasets as well as a moving-wall model informed by rich datasets.

Diagnosis of Aortic Graft Infection: A Case Definition by the Management of Aortic Graft Infection Collaboration (MAGIC).

OBJECTIVE/BACKGROUND: The management of aortic graft infection (AGI) is highly complex and in the absence of a universally accepted case definition and evidence-based guidelines, clinical approaches and outcomes vary widely. The objective was to define precise criteria for diagnosing AGI. METHODS: A process of expert review and consensus, involving formal collaboration between vascular surgeons, infection specialists, and radiologists from several English National Health Service hospital Trusts with large vascular services (Management of Aortic Graft Infection Collaboration [MAGIC]), produced the definition. RESULTS: Diagnostic criteria from three categories were classified as major or minor. It is proposed that AGI should be suspected if a single major criterion or two or more minor criteria from different categories are present. AGI is diagnosed if there is one major plus any criterion (major or minor) from another category. (i) Clinical/surgical major criteria comprise intraoperative identification of pus around a graft and situations where direct communication between the prosthesis and a nonsterile site exists, including fistulae, exposed grafts in open wounds, and deployment of an endovascular stent-graft into an infected field (e.g., mycotic aneurysm); minor criteria are localized AGI features or fever ≥38°C, where AGI is the most likely cause. (ii) Radiological major criteria comprise increasing perigraft gas volume on serial computed tomography (CT) imaging or perigraft gas or fluid (≥7 weeks and ≥3 months, respectively) postimplantation; minor criteria include other CT features or evidence from alternative imaging techniques. (iii) Laboratory major criteria comprise isolation of microorganisms from percutaneous aspirates of perigraft fluid, explanted grafts, and other intraoperative specimens; minor criteria are positive blood cultures or elevated inflammatory indices with no alternative source. CONCLUSION: This AGI definition potentially offers a practical and consistent diagnostic standard, essential for comparing clinical management strategies, trial design, and developing evidence-based guidelines. It requires validation that is planned in a multicenter, clinical service database supported by the Vascular Society of Great Britain & Ireland.

A proof-of-principle study on animals for a new method of anastomosing vessels using intraluminal stents.

The aim of this proof-of-principle study was to assess an intraluminal expandable stent design using an existing cardiac stent. Intraluminal stents minimise the amount of suturing necessary when performing an end-to-end anastomosis. The stent is passed halfway through the lumen on each end of the vessel to be anastomosed and is expanded using a retrievable balloon. An adequately expanded stent holds the blood vessel ends in contact without the need for sutures. This method was tested on an end-to-end anastomosis performed on the carotid vessels of two New Zealand male rabbits. The vessels were patent with good blood flow at the end of 16 days. This method has a potential use in vascular, microvascular and luminal anastomoses within various sub-specialities of surgery.

Peripheral arterial disease: a literature review.

INTRODUCTION: Peripheral arterial disease (PAD) is a common vascular condition that affects both quality of life and life expectancy with an increased risk of cardiovascular events. SOURCES OF DATA: A literature search was carried out of Pub-Med, MEDLINE, the Cochrane Library and Google Scholar from the establishment of these databases up to February 2012. The search was performed by using the keywords 'peripheral arterial disease' and one of the following words: 'management', 'investigations', 'risk factors', 'epidemiology', 'revascularization', 'cryoplasty', 'atherectomy' and 'gene therapy'. Studies were limited to those published in English language. AREAS OF AGREEMENT: Aggressive risk factors modification is needed to reduce cardiovascular-related mortality in PAD patients. AREAS OF CONTROVERSY: Choice of endovascular or surgical intervention remains controversial in an ever-evolving field. GROWING POINTS: There is a rapid expansion of endovascular technologies aiming to improve the effectiveness of this modality. AREAS TIMELY FOR DEVELOPING RESEARCH: The advances in the fields of gene therapy and therapeutic angiogenesis mean these are potential future treatments. Tissue engineering is a developing area and aims to produce grafts with similar patency and infection profiles to those of autologous material. Further elucidation of the pathophysiology of atherosclerosis is required to provide new targets for pharmacotherapy.

Comparative stability of sodium tetradecyl sulphate (STD) and polidocanol foam: impact on vein damage in an in-vitro model.

OBJECTIVES: To compare the half-life of STD and polidocanol air-based foams and the damage they inflict upon human great saphenous vein in an in-vitro model. METHODS: The time for the volume of 3% STD and polidocanol foams to reduce by 10% (T(90)) and 50% (T(50)) was recorded in an incubator at 37 °C. Segments of proximal GSV harvested during varicose vein surgery were filled with foam for 5 or 15 min. Histological analysis determined percentage endothelial cell loss and depth of media injury. RESULTS: Median (±IQR) T(90) and T(50) for polidocanol were 123.3 s (111.7-165.6) and 266.3 s (245.6-383.1) versus 102.03 s (91.1-112) and 213.13 s (201-231.6) for STD (T(90)p = 0.008, T(50)p = 0.004). Median endothelial loss with polidocanol was; 63.5% (62.2-82.8) and 85.9% (83.8-92.5) versus 86.3% (84.8-93.7) and 97.64% (97.3-97.8) for STD after 5 and 15 min (p = 0.076 and p = 0.009). The median depth and % media thickness injured were 0 µm (0-0 µm) and 0% for both assessments with polidocanol versus 37.4 µm (35.3-45.8 and 43.4 µm (42.1-46.7) and 3.5% (3.1-3.6) and 5.3% (3.7-6.0) after 5 and 15 min for STD (p < 0.01 for all comparisons). CONCLUSION: Although polidocanol foam shows greater stability than STD foam perhaps remaining in the vein for longer, endothelial cell loss and damage to the media were significantly greater with STD.

The LOX-1 Scavenger Receptor and Its Implications in the Treatment of Vascular Disease.

Cardiovascular disease is the leading cause of death. The disease is due to atherosclerosis which is characterized by lipid and fat accumulation in arterial blood vessel walls. A key causative event is the accumulation of oxidised low density lipoprotein particles within vascular cells, and this is mediated by scavenger receptors. One such molecule is the LOX-1 scavenger receptor that is expressed on endothelial, vascular smooth muscle, and lymphoid cells including macrophages. LOX-1 interaction with OxLDL particles stimulates atherosclerosis. LOX-1 mediates OxLDL endocytosis via a clathrin-independent internalization pathway. Transgenic animal model studies show that LOX-1 plays a significant role in atherosclerotic plaque initiation and progression. Administration of LOX-1 antibodies in cellular and animal models suggest that such intervention inhibits atherosclerosis. Antiatherogenic strategies that target LOX-1 function using gene therapy or small molecule inhibitors would be new ways to address the increasing incidence of vascular disease in many countries.

Assessment of the antimicrobial activity of acellular vascular grafts.

Several studies have reported biological vascular grafts to be more resistant to microbial infection than synthetic counterparts in vivo. Indeed, small intestinal submucosa (SIS) materials have previously been reported to be antimicrobial. The aim of this study was to assess the antimicrobial activity and the ability to resist biofilm formation of a novel acellular vascular graft and compare it to commercially available alternatives using a range of organisms: MRSA, MSSA, Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa and Candida albicans. This was achieved using a modified disk diffusion assay and extraction of the materials into solution followed by minimum inhibitory concentration assays. To assess resistance to biofilm formation a novel biofilm assay was developed which compared the total colony forming units (CFU) recovered from each material and identification of the percentage of CFU which were loosely attached, residing within the biofilm or attached to the biomaterial. The results indicated a lack of antimicrobial activity for all materials tested, including SIS. The biological materials were more resistant to the formation of a biofilm compared to Dacron.

Indolinones and anilinophthalazines differentially target VEGF-A- and basic fibroblast growth factor-mediated responses in primary human endothelial cells.

BACKGROUND AND PURPOSE: The potent pro-angiogenic growth factors VEGF-A and basic fibroblast growth factor (bFGF) exert their effects by binding VEGF receptor 2 and FGF receptor tyrosine kinases, respectively. Indolinones (e.g. SU5416 and Sutent) and anilinophthalazines (e.g. PTK787) are potent small molecule inhibitors of VEGFR2 and other tyrosine kinases, but their effects on VEGF-A- and bFGF-stimulated endothelial responses are unclear. Here we assess the ability of these compounds to inhibit pro-angiogenic responses through perturbation of receptor activity and endothelial function(s). EXPERIMENTAL APPROACH: We used in silico modelling, in vitro tyrosine kinase assays, biochemistry and microscopy to evaluate the effects of small molecules on receptor tyrosine kinase activation and intracellular signalling. Primary human endothelial cells were used to assess intracellular signalling, cell migration, proliferation and tubulogenesis. KEY RESULTS: We predicted that the anilinophthalazine PTK787 binds the tyrosine kinase activation loop whereas indolinones are predicted to bind within the hinge region of the split kinase domain. Sutent is a potent inhibitor of both VEGFR2 and FGFR1 tyrosine kinase activity in vitro. The compounds inhibit both ligand-dependent and -independent VEGFR2 trafficking events, are not selective for endothelial cell responses and inhibit both VEGF-A- and bFGF-mediated migration, wound healing and tubulogenesis at low concentrations. CONCLUSIONS AND IMPLICATIONS; We propose that these compounds have novel properties including inhibition of bFGF-mediated endothelial responses and perturbation of VEGFR2 trafficking. Differential inhibitor binding to receptor tyrosine kinases translates into more potent inhibition of bFGF- and VEGF-A-mediated intracellular signalling, cell migration and tubulogenesis. Indolinones and anilinophthalazines thus belong to a class of multi-kinase inhibitors that show clinical efficacy in disease therapy.

Gene therapy in the treatment of peripheral arterial disease.

BACKGROUND: Peripheral arterial disease remains a significant global health burden despite revolutionary improvements in endovascular techniques over the past decade. The durability of intervention for critical limb ischaemia is poor, and the condition is associated with high morbidity and mortality rates. To address this deficiency, alternative therapeutic options are being explored. Advances in the fields of gene therapy and therapeutic angiogenesis have led to these being advocated as potential future treatments. METHODS: Relevant medical literature from PubMed, Embase, the Cochrane Library and Google Scholar from the inception of these databases to June 2011 was reviewed. RESULTS: Encouraging outcomes in preclinical trials using a variety of proangiogenic growth factors have led to numerous efficacy and safety studies. However, no clinical study has shown significant benefit for gene therapy over placebo. CONCLUSION: Identifying the optimal site for gene delivery, choice of vector and duration of treatment is needed if gene therapy is to become a credible therapeutic option for peripheral arterial disease.

A combinatorial in silico and cellular approach to identify a new class of compounds that target VEGFR2 receptor tyrosine kinase activity and angiogenesis.

BACKGROUND AND PURPOSE: Vascular endothelial growth factor receptor 2 (VEGFR2) is an attractive therapeutic target for the treatment of diseases such as cancer. Small-molecule VEGFR2 inhibitors of a variety of chemical classes are currently under development or in clinical use. In this study, we describe the de novo design of a new generation pyrazole-based molecule (JK-P3) that targets VEGFR2 kinase activity and angiogenesis. EXPERIMENTAL APPROACH: JK-P compound series were designed using de novo structure-based identification methods. Compounds were tested in an in vitro VEGFR2 kinase assay. Using primary endothelial cells, JK-P compounds were assessed for their ability to inhibit VEGF-A-stimulated VEGFR2 activation and intracellular signalling. We tested these compounds in cell migration, proliferation and angiogenesis assays. KEY RESULTS: JK-P3 and JK-P5 were predicted to bind the VEGFR2 kinase domain with high affinity, and both compounds showed pronounced inhibition of endogenous VEGFR2 kinase activity in primary human endothelial cells. Only JK-P3 inhibited VEGF-A-stimulated VEGFR2 activation and intracellular signalling. Interestingly, JK-P3 inhibited endothelial monolayer wound closure and angiogenesis but not endothelial cell proliferation. Both compounds inhibited fibroblast growth factor receptor kinase activity in vitro, but not basic fibroblast growth factor-mediated signalling in endothelial cells. CONCLUSIONS AND IMPLICATIONS: This is the first report that describes an anti-angiogenic inhibitor based on such a pyrazole core. Using a de novo structure-based identification approach is an attractive method to aid such drug discovery. These results thus provide an important basis for the development of multi-tyrosine kinase inhibitors for clinical use in the near future.

Infections in vascular surgery.

Infections in vascular surgery are usually of multifactorial nature resulting from a complex interplay of patient, surgical and environmental factors. Preventative measures initiated from the stage of pre-operative screening, maintenance of patient homeostasis and the use of organism-directed antibiotics can contribute to reduce infection rates. Graft preservation techniques are becoming increasingly popular as a method to treat established graft infections. In this article we report on the current trends and techniques on the management of infections in vascular surgery. Ongoing studies are required to continue to accumulate data on the effectiveness of these techniques.

Chronic homocysteine exposure upregulates endothelial adhesion molecules and mediates leukocyte: endothelial cell interactions under flow conditions.

AIMS: Homocysteine upregulates expression of adhesion molecules on endothelial cells which recruits leukocytes and initiates atherosclerosis. Endothelial cells in hyperhomocysteinemic patients are continuously exposed to high levels of homocysteine. This study exposed adult endothelial cells and endothelial cells from immune naïve foetal tissue to homocysteine chronically and studied effects on cellular adhesion molecule expression under static and flow conditions. METHODS: Human umbilical vein endothelial cells (HUVEC) and human saphenous vein endothelial cells (HSVEC) were cultured in medium containing 1 mM dl-homocysteine or l-cysteine for 5-9 days. Proliferation was assessed. Cells were subjected to flowing neutrophils and numbers of tethered, rolled fixed and transmigrated neutrophils on endothelial cells were counted and compared to controls. Immunofluorescence staining with antibodies against Intercellular adhesion molecule-1 (ICAM-1), E-selectin and P-selectin were used to quantify expression. RESULTS: Chronic treatment with 1 mM homocysteine inhibited proliferation of HUVEC and HSVEC. Homocysteine treated cells showed significantly increased expression of ICAM-1, E-selectin and to a lesser extent P-selectin. In both cell types, homocysteine significantly increased interactions between neutrophils and endothelial cells under flow conditions (p < 0.05) while cysteine had no effect. CONCLUSION: Endothelial cells from adult and immune naïve foetal tissue showed similar responses to chronic treatment with homocysteine.

The impact of different concentrations of sodium tetradecyl sulphate and initial balloon denudation on endothelial cell loss and tunica media injury in a model of foam sclerotherapy.

INTRODUCTION: Recanalisation rates (20-32%) 1-3 years after truncal vein foam sclerotherapy (FS) suggest thrombotic occlusion rather than irreversible vein wall injury. This study examines the injury inflicted by sodium tetradecyl sulphate (STD) foam before and after balloon endothelial denudation (BD). METHODS: In 20 patients undergoing great saphenous vein (GSV) stripping 1.5 cm proximal GSV were harvested (controls). The next 1.5 cm were harvested after in situ BD (n = 10) or no denudation (n = 10). These test segments were filled with 1% or 3% STD foam (5 min), flushed and fixed in formalin. Percentage endothelial cell loss (ECL) and tunica media injury were determined (H&E staining) and collagen structure assessed (transmission electron microscopy, TEM). RESULTS: Controls showed no injury. 1% and 3% STD foam caused 86.3% and 92.2% ECL (p < 0.001 versus controls; 1% versus 3%, p = 0.55). Endothelial cells persisted in all sections. BD increased ECL (1%: 96.9%, 3%: 98.1%, p = 0.01) Tunica media injury (smooth muscle vacuolation) was minimal (8.9% (1% STD) and 12% (3% STD) of its depth) and not enhanced by BD (1%: 8.7%, p = 0.93; 3%: 11.3%; p = 0.86). No collagen disruption occurred (TEM). CONCLUSIONS: Balloon denudation increased ECL but did not facilitate tunica media injury. Equivalent injury was inflicted by 1% and 3% STD.

Endothelial progenitor cells as a therapeutic option in peripheral arterial disease.

BACKGROUND: Endothelial progenitor cells (EPC) are a subpopulation of bone-marrow mononuclear cells that are capable of generating new blood vessels in areas of ischaemia or infarction. This review examines the regenerative potential of EPC to ameliorate peripheral ischaemia. METHODS: An online search was done using OVID Medline Search, PubMed, and Cochrane Review Database, for all reviews and original articles in English concerning progenitor or bone-marrow mononuclear cells. RESULTS AND CONCLUSION: There are many controversies in EPC research, especially in the areas of identification, characterization, and therapeutic use. Both animal and human studies have shown benefits from using EPC to combat peripheral arterial and cerebrovascular disease. To bring EPC into wider clinical use, larger controlled clinical trials and better methods of augmenting EPC function and lifespan are required. Until then EPC should be used under robust trial conditions with ethical approval.

Short series of emergency stent-graft repair of symptomatic penetrating thoracic aortic ulcers (PTAU).

Acute penetrating thoracic aortic ulcers (PTAU) are associated with vessel rupture, particularly when intramural haematoma (IMH) is present. Although surgical repair is the treatment of choice for PTAU in the aortic arch, definitive treatment of PTAU in other locations of the thoracic aorta remains controversial, particularly in this frail cohort of patients. Recent series of elective and semi-elective endovascular stent-graft repair of PTAU of the descending thoracic aorta show comparable results with the previously advocated best medical management. We report our results from a retrospective, observational study of acute stent-graft repair of symptomatic PTAU. Between 2000 and 2005, 11 patients (seven male, four female; median age 71 years) presented with acute PTAU. CT scans demonstrated an associated IMH in six, a contained leak in three or rupture in four unstable patients. All were covered by a single endovascular stent [Gore (5), Talent (5), Zenith (1); 10 inserted via the groin and one via iliac conduit within 1 week of presentation (five < 24 h). Technical success was 90.90% (10/11) and 3/11 (27%) died within 30 days (two ARDS, one a persistent leak and rupture at 48 h). One patient developed transient paraplegia; three haemothoraces required chest drains, one of which subsequently required empyema drainage. In survivors, CT scans were satisfactory, with no further intervention required at 32.5 (6-66) months of median follow-up. In conclusion, endovascular management of acute PTAU appears effective and durable with mortality rates that are likely to be better than for open surgery. However, haemodynamic compromise at presentation remains a robust denominator of over-all survival.

Postconditioning: current controversies and clinical implications.

OBJECTIVES: Postconditioning of ischaemic tissue, via mechanical or pharmacological manipulation, offers an exciting avenue towards amelioration of ischaemia-reperfusion injury. Born from the concept of ischaemic preconditioning, postconditioning is advantageous in that prior knowledge of the ischaemic insult is not required, and thus clinical translation may be further reaching. This review explores the current evidence and controversies in both animal and human studies and multiple organ systems. METHODS: A Medline search was conducted to identify English-language articles with 'postconditioning' as a keyword. Two independent researchers scrutinised the literature search for potentially relevant articles. Reference lists from selected articles were manually searched for further relevant articles. RESULTS AND CONCLUSIONS: Postconditioning has been shown to be successful in reducing ischaemia-reperfusion injury in both animal models and clinical trials. Human studies are presently limited to cardiac studies, but there is scope for research into other organ systems with potential beneficial effects, particularly within the field of vascular surgery where ischaemia-reperfusion occurs by nature of both - the disease and the intervention.

Academia and MMC: uncomfortable bed-fellows?

In the changing times of Modernising Medical Careers (MMC), the role of research in training remains unclear. Here we discuss the merits of research in surgical training, new avenues for academia during MMC and the obstacles that trainees may face.

The physiological effects of short-term smoking cessation in claudicants.

INTRODUCTION: Smoking contributes to atherosclerosis and causes significant postoperative morbidity. New antismoking law forces short-term pre-operative abstinence. Demonstrable clinical benefit might motivate complete cessation. Our aim was to determine the effects of 24-hr smoking cessation on cardiorespiratory function and claudication distance. METHODS: Smoking claudicants were randomized to 24hr smoking or abstinence. Following these separate periods, cardiopulmonary exercise testing was performed. Pre- and post-exercise, serum lactate and ankle brachial pressure index (ABPI) were measured. During exercise, cardiorespiratory function, initial and absolute claudication (IC,AC) distances and visual analogue scores (VAS) of pain were recorded. RESULTS: 16 patients completed both tests. IC, AC and VAS were unchanged with abstinence (P = .43, .66, .96, .83). ABPI drop post-exercise was unchanged with abstinence (P = .08, .09). Cardiorespiratory function was not affected by smoking cessation. CONCLUSION: Cardiorespiratory function and claudication symptoms are unchanged following 24-hr smoking cessation. No deterioration in respiratory function is important when considering anaesthetic administration. However, lack of symptomatic improvement may discourage patients from abstaining. Further investigation should determine correlation between short-term abstinence and postoperative morbidity.

Nitric oxide specifically inhibits integrin-mediated platelet adhesion and spreading on collagen.

BACKGROUND: Nitric oxide (NO) inhibits platelet adhesion to collagen, although the precise molecular mechanisms underlying this process are unclear. OBJECTIVES: Collagen-mediated adhesion is a multifaceted event requiring multiple receptors and platelet-derived soluble agonists. We investigated the influence of NO on these processes. RESULTS: S-nitrosoglutathione (GSNO) induced a concentration-dependent inhibition of platelet adhesion to immobilized collagen. Maximal adhesion to collagen required platelet-derived ADP and TxA(2). GSNO-mediated inhibition was lost in the presence of apyrase and indomethacin, suggesting that NO reduced the availability of, or signaling by, ADP and TxA(2). Exogenous ADP, but not the TxA(2) analogue U46619, reversed the inhibitory actions of GSNO on adhesion. Under adhesive conditions NO inhibited dense granule secretion but did not influence TxA(2) generation. These data indicated that NO may block signaling by TxA(2) required for dense granule secretion, thereby reducing the availability of ADP. Indeed, we found TxA(2)-mediated activation of PKC was required to drive dense granule secretion, a pathway that was inhibited by NO. Because our data demonstrated that NO only inhibited the activation-dependent component of adhesion, we investigated the effects of NO on individual collagen receptors. GSNO inhibited platelet adhesion and spreading on alpha(2)beta(1) specific peptide ligand GFOGER. In contrast, GSNO did not inhibit GPVI-mediated adhesion to collagen, or adhesion to the GPVI specific ligand, collagen related peptide (CRP). CONCLUSIONS: NO targets activation-dependent adhesion mediated by alpha(2)beta(1), possibly by reducing bioavailability of platelet-derived ADP, but has no effect on activation-independent adhesion mediated by GPVI. Thus, NO regulates platelet spreading and stable adhesion to collagen.