The blood flow-klf6a-tagln2 axis drives vessel pruning in zebrafish by regulating endothelial cell rearrangement and actin cytoskeleton dynamics.

Recent studies have focused on capillary pruning in various organs and species. However, the way in which large-diameter vessels are pruned remains unclear. Here we show that pruning of the zebrafish caudal vein (CV) from ventral capillaries of the CV plexus in different transgenic embryos is driven by endothelial cell (EC) rearrangement, which involves EC nucleus migration, junction remodeling, and actin cytoskeleton remodeling. Further observation reveals a growing difference in blood flow velocity between the two vessels in CV pruning in zebrafish embryos. With this model, we identify the critical role of Kruppel-like factor 6a (klf6a) in CV pruning. Disruption of klf6a functioning impairs CV pruning in zebrafish. klf6a is required for EC nucleus migration, junction remodeling, and actin cytoskeleton dynamics in zebrafish embryos. Moreover, actin-related protein transgelin 2 (tagln2) is a direct downstream target of klf6a in CV pruning in zebrafish embryos. Together these results demonstrate that the klf6a-tagln2 axis regulates CV pruning by promoting EC rearrangement.

Abnormal morphology biases hematocrit distribution in tumor vasculature and contributes to heterogeneity in tissue oxygenation.

Oxygen heterogeneity in solid tumors is recognized as a limiting factor for therapeutic efficacy. This heterogeneity arises from the abnormal vascular structure of the tumor, but the precise mechanisms linking abnormal structure and compromised oxygen transport are only partially understood. In this paper, we investigate the role that red blood cell (RBC) transport plays in establishing oxygen heterogeneity in tumor tissue. We focus on heterogeneity driven by network effects, which are challenging to observe experimentally due to the reduced fields of view typically considered. Motivated by our findings of abnormal vascular patterns linked to deviations from current RBC transport theory, we calculated average vessel lengths [Formula: see text] and diameters [Formula: see text] from tumor allografts of three cancer cell lines and observed a substantial reduction in the ratio [Formula: see text] compared to physiological conditions. Mathematical modeling reveals that small values of the ratio λ (i.e., [Formula: see text]) can bias hematocrit distribution in tumor vascular networks and drive heterogeneous oxygenation of tumor tissue. Finally, we show an increase in the value of λ in tumor vascular networks following treatment with the antiangiogenic cancer agent DC101. Based on our findings, we propose λ as an effective way of monitoring the efficacy of antiangiogenic agents and as a proxy measure of perfusion and oxygenation in tumor tissue undergoing antiangiogenic treatment.

Time-Restricted Salutary Effects of Blood Flow Restoration on Venous Thrombosis and Vein Wall Injury in Mouse and Human Subjects.

BACKGROUND: Up to 50% of patients with proximal deep vein thrombosis (DVT) will develop the postthrombotic syndrome characterized by limb swelling and discomfort, hyperpigmentation, skin ulcers, and impaired quality of life. Although catheter-based interventions enabling the restoration of blood flow (RBF) have demonstrated little benefit on postthrombotic syndrome, the impact on the acuity of the thrombus and mechanisms underlying this finding remain obscure. In experimental and clinical studies, we examined whether RBF has a restricted time window for improving DVT resolution. METHODS: First, experimental stasis DVT was generated in C57/BL6 mice (n=291) by inferior vena cava ligation. To promote RBF, mice underwent mechanical deligation with or without intravenous recombinant tissue plasminogen activator administered 2 days after deligation. RBF was assessed over time by ultrasonography and intravital microscopy. Resected thrombosed inferior vena cava specimens underwent thrombus and vein wall histological and gene expression assays. Next, in a clinical study, we conducted a post hoc analysis of the ATTRACT (Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis) pharmacomechanical catheter-directed thrombolysis (PCDT) trial (NCT00790335) to assess the effects of PCDT on Venous Insufficiency Epidemiological and Economic Study quality-of-life and Villalta scores for specific symptom-onset-to-randomization timeframes. RESULTS: Mice that developed RBF by day 4, but not later, exhibited reduced day 8 thrombus burden parameters and reduced day 8 vein wall fibrosis and inflammation, compared with controls. In mice without RBF, recombinant tissue plasminogen activator administered at day 4, but not later, reduced day 8 thrombus burden and vein wall fibrosis. It is notable that, in mice already exhibiting RBF by day 4, recombinant tissue plasminogen activator administration did not further reduce thrombus burden or vein wall fibrosis. In the ATTRACT trial, patients receiving PCDT in an intermediate symptom-onset-to-randomization timeframe of 4 to 8 days demonstrated maximal benefits in Venous Insufficiency Epidemiological and Economic Study quality-of-life and Villalta scores (between-group difference=8.41 and 1.68, respectively, P<0.001 versus patients not receiving PCDT). PCDT did not improve postthrombotic syndrome scores for patients having a symptom-onset-to-randomization time of <4 days or >8 days. CONCLUSIONS: Taken together, these data illustrate that, within a restricted therapeutic window, RBF improves DVT resolution, and PCDT may improve clinical outcomes. Further studies are warranted to examine the value of time-restricted RBF strategies to reduce postthrombotic syndrome in patients with DVT.

Hierarchical semantic composition of biosimulation models using bond graphs.

Simulating complex biological and physiological systems and predicting their behaviours under different conditions remains challenging. Breaking systems into smaller and more manageable modules can address this challenge, assisting both model development and simulation. Nevertheless, existing computational models in biology and physiology are often not modular and therefore difficult to assemble into larger models. Even when this is possible, the resulting model may not be useful due to inconsistencies either with the laws of physics or the physiological behaviour of the system. Here, we propose a general methodology for composing models, combining the energy-based bond graph approach with semantics-based annotations. This approach improves model composition and ensures that a composite model is physically plausible. As an example, we demonstrate this approach to automated model composition using a model of human arterial circulation. The major benefit is that modellers can spend more time on understanding the behaviour of complex biological and physiological systems and less time wrangling with model composition.

Alterations in cardiac output in fetuses with congenital heart disease.

OBJECTIVE: Fetuses with severe congenital heart disease (CHD) have altered blood flow patterns. Prior work to assess fetal combined cardiac output (CCO) is limited by sample size and lack of longitudinal gestational data. Our aim was to evaluate CCO in CHD fetuses to determine whether the presence of single ventricle (SV) physiology or aortic obstruction impacts fetal blood flow and cardiovascular hemodynamics. METHOD: Prospective study including singleton fetuses with CHD (n = 141) and controls (n = 118) who underwent a mid- and late-gestation fetal echocardiogram. Ventricular cardiac output was calculated using the standard computation. Combined cardiac output was derived as the sum of the right and left cardiac outputs and indexed to estimated fetal weight. RESULTS: Fetuses with two ventricle (2V) CHD had significantly higher CCO compared to controls and SV CHD fetuses. Fetuses with SV-CHD had similar CCO compared to controls. Fetuses with 2V-CHD and aortic obstruction had significantly higher CCO than fetuses with SV-CHD and aortic obstruction. CONCLUSION: Our findings suggest that the SV can compensate and increase CCO despite the lack of a second functioning ventricle, however, the degree of compensation may be insufficient to support the increased blood flow needed to overcome the hemodynamic and physiologic alternations seen with severe CHD.

Flow-induced Reorganization of Laminin-integrin Networks Within the Endothelial Basement Membrane Uncovered by Proteomics.

The vessel wall is continuously exposed to hemodynamic forces generated by blood flow. Endothelial mechanosensors perceive and translate mechanical signals via cellular signaling pathways into biological processes that control endothelial development, phenotype and function. To assess the hemodynamic effects on the endothelium on a system-wide level, we applied a quantitative mass spectrometry approach combined with cell surface chemical footprinting. SILAC-labeled endothelial cells were subjected to flow-induced shear stress for 0, 24 or 48 h, followed by chemical labeling of surface proteins using a non-membrane permeable biotin label, and analysis of the whole proteome and the cell surface proteome by LC-MS/MS analysis. These studies revealed that of the >5000 quantified proteins 104 were altered, which were highly enriched for extracellular matrix proteins and proteins involved in cell-matrix adhesion. Cell surface proteomics indicated that LAMA4 was proteolytically processed upon flow-exposure, which corresponded to the decreased LAMA4 mass observed on immunoblot. Immunofluorescence microscopy studies highlighted that the endothelial basement membrane was drastically remodeled upon flow exposure. We observed a network-like pattern of LAMA4 and LAMA5, which corresponded to the localization of laminin-adhesion molecules ITGA6 and ITGB4. Furthermore, the adaptation to flow-exposure did not affect the inflammatory response to tumor necrosis factor α, indicating that inflammation and flow trigger fundamentally distinct endothelial signaling pathways with limited reciprocity and synergy. Taken together, this study uncovers the blood flow-induced remodeling of the basement membrane and stresses the importance of the subendothelial basement membrane in vascular homeostasis.

Elevated inflammatory mediators from the maternal-fetal interface to fetal circulation during labor.

BACKGROUND: Elevated cytokines, like IL-1ßand IL-6, are known to contribute to the pathogenesis of labor. However, the change of inflammatory mediators in maternal-fetal interface to fetal circulation is obscure. STUDY DESIGN AND METHODS: We investigated the changes of inflammatory cytokines, chemokines and macrophage in maternal-fetal interface tissues and fetal circulation of women in labor vs. non-labor. Human myometrium, placenta, decidua, fetal membrane and umbilical blood were obtained from in-labor and non-in-labor women who eventually delivered live, singleton infants at term (>37 weeks gestation) by elective caesarean section. Luminex was used to measure the level of cytokines (TNF-α, IL-1ß, IL-6, IL-8) and chemokines (MCP-1, GM-CSF, MIP-1α, MIP-1ß) in each sample (tissue and umbilical blood). Macrophage infiltration was demonstrated by immunohistochemistry. RESULTS: During labor, the level of cytokines TNF-α, IL-1ß, IL-6 and IL-8 and chemokine MCP-1 and MIP-1ß in myometrium is significantly higher (p < 0.05), than those obtained from non-laboring patients. This increase coincides with the influx of macrophage into the myometrium. In addition, IL-1ß and IL-8 (p < 0.05) are also up regulated in fetal membrane during labor compared to non-labor. The cytokines do not change significantly in placenta and decidua tissue. In fetal circulation, IL-6 (p < 0.05) is up regulated in umbilical vein blood in labor group. IL-8 (p = 0.08) in umbilical vein also show an increasing trend during labor. CONCLUSIONS: There are markedly elevated inflammatory mediators in maternal-fetal interface during labor. The increased maternal inflammatory factors released into the fetal circulation through placenta circulation at the time of labor. This increase coincides with the influx of macrophage into the pregnancy tissue, suggesting that the inflammatory response might play an important role in the onset of labor.

Heterogeneous impact of hypotension on organ perfusion and outcomes: a narrative review.

Arterial blood pressure is the driving force for organ perfusion. Although hypotension is common in acute care, there is a lack of accepted criteria for its definition. Most practitioners regard hypotension as undesirable even in situations that pose no immediate threat to life, but hypotension does not always lead to unfavourable outcomes based on experience and evidence. Thus efforts are needed to better understand the causes, consequences, and treatments of hypotension. This narrative review focuses on the heterogeneous underlying pathophysiological bases of hypotension and their impact on organ perfusion and patient outcomes. We propose the iso-pressure curve with hypotension and hypertension zones as a way to visualize changes in blood pressure. We also propose a haemodynamic pyramid and a pressure-output-resistance triangle to facilitate understanding of why hypotension can have different pathophysiological mechanisms and end-organ effects. We emphasise that hypotension does not always lead to organ hypoperfusion; to the contrary, hypotension may preserve or even increase organ perfusion depending on the relative changes in perfusion pressure and regional vascular resistance and the status of blood pressure autoregulation. Evidence from RCTs does not support the notion that a higher arterial blood pressure target always leads to improved outcomes. Management of blood pressure is not about maintaining a prespecified value, but rather involves ensuring organ perfusion without undue stress on the cardiovascular system.

Histopathological study of JNK in venous wall of patients with chronic venous insufficiency related to osteogenesis process.

Chronic venous insufficiency (CVI) is one of the most common vascular pathologies worldwide. One of the risk factors for the development of CVI is aging, which is why it is related to senile changes. The main trigger of the changes that occur in the venous walls in CVI is blood flow reflux, which produces increased hydrostatic pressure, leading to valve incompetence. The cellular response is one of the fundamental processes in vascular diseases, causing the activation of cell signalling pathways such as c-Jun N-terminal kinase (JNK). Metabolic changes and calcifications occur in vascular pathology as a result of pathophysiological processes. The aim of this study was to determine the expression of JNK in venous disease and its relationship with the role played by the molecules involved in the osteogenic processes in venous tissue calcification. This was a cross-sectional study that analyzed the greater saphenous vein wall in 110 patients with (R) and without venous reflux (NR), classified according to age. Histopathological techniques were used and protein expression was analysed using immunohistochemistry techniques for JNK and markers of osteogenesis (RUNX2, osteocalcin (OCN), osteopontin (OPN)). Significantly increased JNK, RUNX2, OCN, OPN and pigment epithelium-derived factor (PEDF) protein expression and the presence of osseous metaplasia and amorphous calcification were observed in younger patients (<50 years) with venous reflux. This study shows for the first time the existence of an osteogenesis process related to the expression of JNK in the venous wall.

Late gestation predictors of a postnatal biventricular circulation after fetal aortic valvuloplasty.

OBJECTIVES: Fetal aortic valvuloplasty (FAV) for severe aortic stenosis (AS) has shown promise in averting progression to hypoplastic left heart syndrome. After FAV, predicting which fetuses will achieve a biventricular (BiV) circulation after birth remains challenging. Identifying predictors of postnatal circulation on late gestation echocardiography will improve parental counseling. METHODS: Liveborn patients who underwent FAV and had late gestation echocardiography available were included (2000-2017, n = 96). Multivariable logistic regression and classification and regression tree analysis were utilized to identify independent predictors of BiV circulation. RESULTS: Among 96 fetuses, 50 (52.1%) had BiV circulation at the time of neonatal discharge. In multivariable analysis, independent predictors of biventricular circulation included left ventricular (LV) long axis z-score (OR 3.2, 95% CI 1.8-5.7, p < 0.001), LV ejection fraction (OR 1.3, 95% CI 1.0-1.8, p = 0.023), anterograde aortic arch flow (OR 5.0, 95% CI 1.2-20.4, p = 0.024), and bidirectional or right-to-left foramen ovale flow (OR 4.6, 95% CI 1.4-15.8, p = 0.015). CONCLUSION: Several anatomic and physiologic parameters in late gestation were found to be independent predictors of BiV circulation after FAV. Identifying these predictors adds to our understanding of LV growth and hemodynamics after FAV and may improve parental counseling.

The standardized method and clinical experience may improve the reliability of visually assessed capillary refill time.

OBJECTIVE: Reliability of capillary refill time (CRT) has been questionable. The purpose of this study was to examine that a standardized method and clinical experience would improve the reliability of CRT. METHODS: This was a cross-sectional study in the emergency department (ED). Health care providers (HCPs) performed CRT without instruments (method 1) to classify patients as having normal or abnormal (≤2/>2 s) CRT. An ED attending physician quantitatively measured CRT using a chronograph (standardized visual CRT, method 2). A video camera was mounted on top of the hand tool to obtain a digital recording. The videos were used to calculate CRT via image software (image CRT, method 3) as a criterion standard of methods. Additionally, 9 HCPs reviewed the videos in a separate setting in order to visually assess CRT (video CRT, method 4). RESULTS: We enrolled 30 patients in this study. Standardized visual CRT (method 2) identified 10 abnormal patients, while two patients were identified by CRT without instruments (method 1). There was no correlation (κ value, 0.00) between CRT without instruments (method 1) and image CRT (method 3), however the correlation between standardized visual CRT (method 2) and image CRT (method 3) was strong (r = 0.64, p < 0.01). Both intra-observer reliability and correlation coefficient with image CRT (method 3) was higher in video CRT (method 4) by more experienced clinicians. CONCLUSIONS: Visual assessment is variable but a standardized method such as using a chronograph and/or clinical experience may aid clinicians to improve the reliability of visually assessed CRT.

Vascular Aspects in Glaucoma: From Pathogenesis to Therapeutic Approaches.

Glaucomatous optic neuropathies have been regarded as diseases caused by high intraocular pressure for a long time, despite the concept of vascular glaucoma dating back to von Graefe in 1854. Since then, a tremendous amount of knowledge about the ocular vasculature has been gained; cohort studies have established new vascular risk factors for glaucoma as well as identifying protective measures acting on blood vessels. The knowledge about the physiology and pathophysiology of the choroidal, retinal, as well as ciliary and episcleral circulation has also advanced. Only recently have novel drugs based on that knowledge been approved for clinical use, with more to follow. This review provides an overview of the current vascular concepts in glaucoma, ranging from novel pathogenesis insights to promising therapeutic approaches, covering the supply of the optic nerve head as well as the aqueous humor production and drainage system.

Confocal Blood Flow Videomicroscopy of Thrombus Formation over Human Arteries and Local Targeting of P2X7.

Atherothrombosis exposes vascular components to blood. Currently, new antithrombotic therapies are emerging. Herein we investigated thrombogenesis of human arteries with/without atherosclerosis, and the interaction of coagulation and vascular components, we and explored the anti-thrombogenic efficacy of blockade of the P2X purinoceptor 7 (P2X7). A confocal blood flow videomicroscopy system was performed on cryosections of internal mammary artery (IMA) or carotid plaque (CPL) determining/localizing platelets and fibrin. Blood from healthy donors elicited thrombi over arterial layers. Confocal microscopy associated thrombus with tissue presence of collagen type I, laminin, fibrin(ogen) and tissue factor (TF). The addition of antibodies blocking TF (aTF) or factor XI (aFXI) to blood significantly reduced fibrin deposition, variable platelet aggregation and aTF + aFXI almost abolished thrombus formation, showing synergy between coagulation pathways. A scarce effect of aTF over sub-endothelial regions, more abundant in tissue TF and bundles of laminin and collagen type I than deep intima, may suggest tissue thrombogenicity as molecular structure-related. Consistently with TF-related vascular function and expression of P2X7, the sections from CPL but not IMA tissue cultures pre-treated with the P2X7 antagonist A740003 demonstrated poor thrombogenesis in flow experiments. These data hint to local targeting studies on P2X7 modulation for atherothrombosis prevention/therapy.

Applications of machine learning for simulations of red blood cells in microfluidic devices.

BACKGROUND: For optimization of microfluidic devices for the analysis of blood samples, it is useful to simulate blood cells as elastic objects in flow of blood plasma. In such numerical models, we primarily need to take into consideration the movement and behavior of the dominant component of the blood, the red blood cells. This can be done quite precisely in small channels and within a short timeframe. However, larger volumes or timescales require different approaches. Instead of simplifying the simulation, we use a neural network to predict the movement of the red blood cells. RESULTS: The neural network uses data from the numerical simulation for learning, however, the simulation needs only be run once. Alternatively, the data could come from video processing of a recording of a biological experiment. Afterwards, the network is able to predict the movement of the red blood cells because it is a system of bases that gives an approximate cell velocity at each point of the simulation channel as a linear combination of bases.In a simple box geometry, the neural network gives results comparable to predictions using fluid streamlines, however in a channel with obstacles forming slits, the neural network is about five times more accurate.The network can also be used as a discriminator between different situations. We observe about two-fold increase in mean relative error when a network trained on one geometry is used to predict trajectories in a modified geometry. Even larger increase was observed when it was used to predict trajectories of cells with different elastic properties. CONCLUSIONS: While for uncomplicated box channels there is no advantage in using a system of bases instead of a simple prediction using fluid streamlines, in a more complicated geometry, the neural network is significantly more accurate. Another application of this system of bases is using it as a comparison tool for different modeled situations. This has a significant future potential when applied to processing data from videos of microfluidic flows.

Graphene-based ultrasensitive optical microfluidic sensor for the real-time and label-free monitoring of simulated arterial blood flow.

Highly sensitive, real-time and label-free sensing of liquid flow in microfluidic environments remains challenging. Here, by growing high-quality graphene directly on a glass substrate, we designed a microfluidic-integrated graphene-based flow sensor (GFS) capable of detecting complex, weak, and transient flow velocity and pressure signals in a microfluidic environment. This device was used to study weak and transient liquid flows, especially blood flow, which is closely related to heart and artery functions. By simulating cardiac peristalsis and arterial flow using peristaltic pumps and microfluidic systems, we monitored simulated arterial blood flow. This ultrasensitive graphene-based flow sensor accurately detected a flow velocity limit as low as 0.7 mm/s, a pumping frequency range of 0.04 Hz to 2.5 Hz, and a pressure range from 0.6 kPa to 14 kPa. By measuring the blood flow velocities and pressures, pathological blood flow signals were distinguished and captured by the corresponding flow velocities or pressures, which can reflect vascular occlusion and heart functions. This sensor may be used for the real-time and label-free monitoring of patients' basic vital signs using their blood flow and provide a possible new method for the care of critically ill patients.

What determines systemic blood flow in vertebrates?

In the 1950s, Arthur C. Guyton removed the heart from its pedestal in cardiovascular physiology by arguing that cardiac output is primarily regulated by the peripheral vasculature. This is counterintuitive, as modulating heart rate would appear to be the most obvious means of regulating cardiac output. In this Review, we visit recent and classic advances in comparative physiology in light of this concept. Although most vertebrates increase heart rate when oxygen demands rise (e.g. during activity or warming), experimental evidence suggests that this tachycardia is neither necessary nor sufficient to drive a change in cardiac output (i.e. systemic blood flow, Q̇sys) under most circumstances. Instead, Q̇sys is determined by the interplay between vascular conductance (resistance) and capacitance (which is mainly determined by the venous circulation), with a limited and variable contribution from heart function (myocardial inotropy). This pattern prevails across vertebrates; however, we also highlight the unique adaptations that have evolved in certain vertebrate groups to regulate venous return during diving bradycardia (i.e. inferior caval sphincters in diving mammals and atrial smooth muscle in turtles). Going forward, future investigation of cardiovascular responses to altered metabolic rate should pay equal consideration to the factors influencing venous return and cardiac filling as to the factors dictating cardiac function and heart rate.

The acute and chronic effects of resistance training with blood flow restriction on hormonal responses in untrained young men: A comparison of frequency.

The present study aimed to determine the effect of low-intensity training with blood flow restriction (BFR) on the response rate of anabolic hormones. Forty healthy and untrained young men, aged 18 to 25 years old, were randomly divided into five groups: one session of BFR training (BFR1), two sessions of BFR training (BFR2), one session of resistance training without BFR (WBFR1), two sessions of resistance training without BFR (WBFR2), and the control group (without training). BFR groups had three sets of 20 repetitions with 20-30% 1RM, and none-BFR groups had three sets of 10 repetitions with 70-80% 1RM for six weeks. Both BFR1 and WBFR1 groups trained 3day a week (1 session in a day and three sessions a week), BFR2 and WBFR2 groups trained three days a week (but two sessions a day and six sessions in a week) and Control group did not perform any training. The mean changes in growth hormone(GH), testosterone(TS), and vascular endothelial growth factor (VEGF) hormones were determined by ELISA technique before, after a first training session and after six weeks of the training program. To the analysis of data, two way repeated measures ANOVA at a significant level of P<0.05  also were used. The results showed a significant increase in GH levels in each of the four training groups as compared with the pre-test and the control group after a first training session and after six weeks of the training program (P<0.05). There was no significant increase in TS levels in each of the four training groups, as compared with the pre-test and the control group in both acute and chronic TS response (P>0.05). Only the WBFR1 group did not significantly increase in VEGF levels after the first training session (P>0.05). In chronic VEGF response, there were no significant changes observed in all training groups as compared with the control group(P>0.05). Despite the effectiveness of low-intensity BFR training, such as high-intensity resistance training on hormonal responses, two sessions per day training with the same volume does not necessarily result in larger responses in all hormones than one session per day training.

Protease-Activatable Adeno-Associated Virus Vector for Gene Delivery to Damaged Heart Tissue.

Adeno-associated virus (AAV) has emerged as a promising gene delivery vector because of its non-pathogenicity, simple structure and genome, and low immunogenicity compared to other viruses. However, its adoption as a safe and effective delivery vector for certain diseases relies on altering its tropism to deliver transgenes to desired cell populations. To this end, we have developed a protease-activatable AAV vector, named provector, that responds to elevated extracellular protease activity commonly found in diseased tissue microenvironments. The AAV9-based provector is initially inactive, but then it can be switched on by matrix metalloproteinases (MMP)-2 and -9. Cryo-electron microscopy and image reconstruction reveal that the provector capsid is structurally similar to that of AAV9, with a flexible peptide insertion at the top of the 3-fold protrusions. In an in vivo model of myocardial infarction (MI), the provector is able to deliver transgenes site specifically to high-MMP-activity regions of the damaged heart, with concomitant decreased delivery to many off-target organs, including the liver. The AAV provector may be useful in the future for enhanced delivery of transgenes to sites of cardiac damage.

Why the endothelium? The endothelium as a target to reduce diabetes-associated vascular disease.

Over the past 66 years, our knowledge of the role of the endothelium in the regulation of cardiovascular function and dysfunction has advanced from the assumption that it is a single layer of cells that serves as a barrier between the blood stream and vascular smooth muscle to an understanding of its role as an essential endocrine-like organ. In terms of historical contributions, we pay particular credit to (1) the Canadian scientist Dr. Rudolf Altschul who, based on pathological changes in the appearance of the endothelium, advanced the argument in 1954 that "one is only as old as one's endothelium" and (2) the American scientist Dr. Robert Furchgott, a 1998 Nobel Prize winner in Physiology or Medicine, who identified the importance of the endothelium in the regulation of blood flow. This review provides a brief history of how our knowledge of endothelial function has advanced and now recognize that the endothelium produces a plethora of signaling molecules possessing paracrine, autocrine, and, arguably, systemic hormone functions. In addition, the endothelium is a therapeutic target for the anti-diabetic drugs metformin, glucagon-like peptide I (GLP-1) receptor agonists, and inhibitors of the sodium-glucose cotransporter 2 (SGLT2) that offset the vascular disease associated with diabetes.

A novel roller pump for physiological flow.

Having physiological correct flow waveforms is a key feature for experimental studies of blood flow, especially in the process of developing and testing a new medical device such as stent, mechanical heart valve, or any implantable medical device that involves circulation of blood through the device. It is also a critical part of a perfusion system for cardiopulmonary bypass and extracorporeal membrane oxygenation procedures. This study investigated the feasibility of a novel roller pump for use in experimental flow phantoms. Flow rates of carotid flow profile measured directly with the ultrasonic flow meter matched well with the reference flow rates programmed into the machine with similarity index of 0.97 and measured versus programmed flow rates at specific time-points of peak systolic velocity (PSV): 0.894 vs 0.880, end systolic velocity (ESV): 0.333 vs 0.319, and peak diastolic velocity (PDV): 0.514 vs 0.520 L/min. Flow rates derived from video analysis of the pump motion for carotid, suprarenal, and infrarenal flows also matched well with references with similarity indices of 0.99, 0.99, and 0.96, respectively. Measured flow rates (mean/standard deviation) at PSV, ESV, and PDV time-points for carotid: 0.883/0.016 vs 0.880, 0.342/0.007 vs 0.319, and 0.485/0.009 vs 0.520; suprarenal: 3.497/0.014 vs 3.500, 0.004/0.003 vs 0, and 1.656/0.073 vs 1.453; infrarenal: 4.179/0.024 vs 4.250, -1.147/0.015 vs -1.213, and 0.339/0.017 vs 0.391 L/min, respectively. The novel roller pump is suitable for benchtop testing of physiological flow.