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Thrombogenicity poses a challenge to the clinical translation of engineered grafts. Previously, small-diameter vascular grafts (sdVG) composed of fibrin hydrogel microfiber tubes (FMT) with an external poly(ε-caprolactone) (PCL) sheath supported long-term patency in mice. Towards the development of an sdVG with off-the-shelf availability, the FMT's shelf stability, scale-up, and successful conjugation of an antithrombotic drug to the fibrin scaffold are reported here. FMTs maintain mechanical stability and high-water retention after storage for one year in a freezer, in a refrigerator, or at room temperature. Low molecular weight heparin-conjugated fibrin scaffolds enabled local and sustained delivery during two weeks of enzymatic degradation. Upscaled fabrication of sdVGs provides natural biodegradable grafts with size and mechanics suitable for human application. Implantation in a carotid artery interposition porcine model exhibited no rupture with thrombi prevented in all heparinized sdVGs (n = 4) over 4-5 weeks. Remodeling of the sdVGs is demonstrated with endothelial cells on the luminal surface and initial formation of the medial layer by 4-5 weeks. However, neointimal hyperplasia at 4-5 weeks led to the stenosis and occlusion of most of the sdVGs, which must be resolved for future long-term in vivo assessments. The off-the-shelf, biodegradable heparinized fibrin sdVG layer limits acute thrombogenicity while mediating extensive neotissue formation as the PCL sheath maintains structural integrity. STATEMENT OF SIGNIFICANCE: To achieve clinical and commercial utility of small-diameter vascular grafts as arterial conduits, these devices must have off-the-shelf availability for emergency arterial bypass applications and be scaled to a size suitable for human applications. A serious impediment to clinical translation is thrombogenicity. Treatments have focused on long-term systemic drug therapy, which increases the patient's risk of bleeding complications, or coating grafts and stents with anti-coagulants, which minimally improves patient outcomes even when combined with dual anti-platelet therapy. We systematically modified the biomaterial properties to develop anticoagulant embedded, biodegradable grafts that maintain off-the-shelf availability, provide mechanical stability, and prevent clot formation through local drug delivery.

Introduction: Depending on surrounding cell types, substrate mechanics, and chemical agonists, vascular smooth muscle cells (VSMCs) alternate between a contractile and synthetic phenotype. While endothelial cells (ECs) do not modulate their phenotype in this way, their behavior is highly dependent on location within the body. These variations are part of healthy vascular function, but improper phenotype has been implicated in cardiovascular disease. Atherosclerotic lesions, for example, have been found to be high in dedifferentiated, synthetic VSMCs as well as endothelial cells that have undergone endothelial to mesenchymal transition (EndMT). The overall goal of this project is to understand the effect of cross-talk between ECM and mechanical strain on vascular cell plasticity during aging. Materials and Methods: Mouse aortic smooth muscle cells (maSMCs) were isolated from C57Bl6 mice at less than 3 months (young), 6 to 10 months of age (middle-aged; MA), or greater than 15 months of age (old). Cells were then seeded onto dye-quenched (DQ) collagen type I (Col-I) substrate and measured for gain of fluorescent signal over 3 days. Human aortic endothelial cells (HAECs) were seeded onto glass cover slips or fibronectin coated PDMS chambers. Cells were further treated with or without TGF-β2 with daily media changes over 3 days. IF images were captured with a Leica Confocal microscope and quantification was performed using ImageJ. Results: ECs cultured on glass or treated with TGF-β2 show increased expression of SM22α and decreased expression of VECAD. Physiological strain (10%) did not cause changes in expression relative to static (0%). Mouse aortic SMCs isolated from older mice had significantly decreased rates of Col-I cleavage. Conclusions: maSMCs from older mice have lower Col-I turnover than their younger counterparts. This is consistent with bulk tissue behavior, as it is well known that relative collagen levels increase in the elastic vasculature as we age. HAECs on stiff substrates are more likely to show signs of EndMT – consistent with other studies. The addition of agonists such as TGF-β2 can reproduce this behavior in cells cultured on soft substrates. NASEM Ford Foundation Pre-Doctoral Fellowship and NHBLI grant R01HL148112 01 (L.S.) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Background: Pulmonary arterial hypertension (PAH) is characterized by narrowing of the pulmonary arteries, endothelial cell dysfunction, and an increased vascular cell proliferation. Increased proliferation is also accompanied by glycolytic shift, where glucose is shunted towards anaerobic respiration and production of critical macromolecules. This decreases the available glucose that can be used as a fuel in the tricarboxylic acid (TCA) cycle. To compensate for the lack of TCA cycle metabolites, there is an increase in the use of non-glucose fuels - such as amino acids and fatty acids. However, the effect of this shift on other metabolic pathways is still unknown. In this study, we investigated the levels of metabolites across the pulmonary circulation to define the metabolic shift that cells undergo during PAH. Material & Methods: We carried out metabolomic analysis on serum samples taken from the right and left ventricles (RV and LV) of rats with PAH (SU5416/Hypoxia model: SuHx) and normoxic controls. We also isolated MVECs from each group and performed both targeted and untargeted metabolomics on the cell lysates. Results: Induction of PAH resulted in increased pulmonary artery pressures and RV hypertrophy. Metabolomics of the RV serum were different in PAH versus control rats. This was driven by lower metabolite levels of several amino acids, including glutamine, phenylalanine, and valine. Normoxia- and SuHx-MVEC lysates samples were also distinct, with increased levels of lactic acid contributing significantly to the differences between animals with PAH and controls. Importantly, and in contrast to the serum, where glutamine levels were decreased, we observed increased levels of intracellular glutamine in our analysis. Similarly, intracellular levels of amino acids like phenylalanine, tyrosine and leucine were increased in these lysates. This also contrasted with the serum, where levels of these amino acids were decreased. Interestingly, LV levels of amino acids like valine, glutamine and lysine were similar in normoxic and SuHx samples. However, we did observe increased citrulline levels in SuHx LV serum samples. Comparing the LV/RV ratio in our samples revealed that increased oxidized glutathione was a major determinant of the difference between the SuHx and control groups. Conclusion: Our data suggests that decreased RV serum levels of amino acids in SuHx rats may be driven by increased consumption in the pulmonary vasculature. Given that glutamine levels in the RV are decreased, while being increased intracellularly in MVECs, we hypothesize that glutamine consumption in the lung microvasculature may be driven in part, to produce reduced glutathione. This is also supported by the oxidized glutathione gradient across the pulmonary vasculature in our experiments. These results provide the basis for a mechanistic study aimed at understanding how interrupting glutathione and/or branched-chain amino acid metabolism in MVECs contributes to PAH. NHLBI grant K08HL145132 (J.S.), NHLBI grant R01HL148112 01 (L.S), NHLBI grant R01HL151530 (K.S) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Introduction: Hypertension is a major risk factor for cardiovascular diseases including cardiac hypertrophy, stroke, and heart failure. Hypertension accelerates arterial stiffening noted with natural aging. Aortic stiffness has been shown to be both a cause and a consequence of isolated systolic hypertension. Thus, it is of high clinical interest to target arterial stiffening in the context of hypertension. We have previously identified lysyl oxidase-like 2 (LOXL2) as a potential therapeutic target for treating vascular stiffening. LOXL2 is a key enzyme in the extracellular matrix that catalyzes matrix deposition and remodeling. We have previously shown that LOXL2 depletion decelerates arterial stiffening during natural aging by modulating matrix remodeling and smooth muscle cell stiffness and contractility. Our hypothesis in this study is that LOXL2 depletion is protective against hypertension induced arterial stiffening, and this was determined via the established angiotensin II (Ang II) infusion model of experimental hypertension in LOXL2+/- mouse model. Methods and results: Ang II pumps were implanted in LOXL2+/- and WT mice for a 3-week treatment. Blood pressure and pulse wave velocity were measured noninvasively to assess hypertension and aortic stiffness. Results corroborated that Ang II infusion induced hypertension in WT and LOXL2+/- mice, and that arterial stiffening was ameliorated in LOXL2+/- mice even when Ang II-induced hypertension was present. Uniaxial tensile testing was used to test the elastic properties of the aortic rings, and wire myography was used to test their vasoreactivity. These experiments showed that the increase in arterial stiffness due to Ang II-induced hypertension was driven by both matrix remodeling and VSMC response. Histological analysis supported these findings, showing increased aortic wall thickness, interlamellar distance and collagen deposition with Ang II infusion. Elevated heart weight in mice with Ang II infusion and qPCR results revealed induced cardiac hypertrophy, which was not protected by LOXL2 knockdown. Moreover, human aortic SMC and endothelial cells were cyclically stretched, to show that the overexpression of LOXL2 in the aorta under Ang II-induced hypertension is upregulated by cyclic strain. Conclusion: Arterial stiffening is increased with Ang II infusion; however, it is ameliorated in LOXL2+/- mice compared to WT despite the development of Ang II-induced hypertension. This rise in arterial stiffness is driven by both matrix remodeling and VSMC response. Cardiac hypertrophy occurred with Ang II infusion and LOXL2 knockdown was not protective against it. Future studies will continue to 1) elucidate the mechanisms involved in the regulation of LOXL2 expression in response to Ang II-induced hypertension, 2) investigate the sex differences in in vivo stiffness and vasoreactivity, and 3) study LOXL2 as a potential therapeutic target against cardiac hypertrophy. Private foundation grant: NHLBI grant R01HL148112 01 (L.S.) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Tissue-engineered vascular grafts (TEVGs) require adequate extracellular matrix (ECM) to withstand arterial pressure. Tissue transglutaminase (TG2) and lysyl oxidase (LOX) are enzymes that cross-link ECM proteins and play a pivotal role in the development of vascular stiffness associated with aging. The purpose of this study is to investigate the expression of ECM cross-linking enzymes and mechanisms of scaffold degeneration leading to vascular stiffness in TEVG remodeling. Fast- and slow-degrading electrospun TEVGs were fabricated using polydioxanone (PDO) and poly(L-lactide-co-caprolactone) (PLCL) copolymer, with a PDO/PLCL ratio of 9:1 for fast-degrading and 1:1 for slow-degrading graft. These grafts were implanted in rats (

Olfactory receptor 558 (Olfr558) is expressed in the kidney where its functional role is unknown. Using RNAScope, we find that Olfr558 localizes to vascular smooth muscle, including the renal afferent arteriole. Thus, we measured blood pressure (BP) in Olfr558 wild-type (WT) and knockout (KO) mice. Systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP) were measured in whole-body Olfr558 wild-type (WT) and knockout (KO) via telemetry. It is known that males have a higher BP than premenopausal females in both humans and mice; indeed, we find Olfr558WT males (M) have higher BP than females (F, n=7-9 per group), including MAP (M:101.0±1.6 vs. F:89.0±0.9 mmHg, p Funding: R56DK107726 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Introduction The kidney is one of the main organs affected by microvascular damage wrought by hypertension. We developed an approach to investigate renal microcirculatory disturbance in live mice by measuring post-occlusive reactive hyperemia (PORH), a reactivity test exploring endothelial and neuro-microvascular functioning. Laser speckle-contrast analysis (LASCA) assesses microvascular blood flow; it provides real-time images of spatial and temporal blood flow dynamics. We compared basal blood flow and PORH test between control and angiotensin-II-treated mice (Ang-II) to validate the model. Objective The study objective was to develop an approach to investigate renal microcirculation, and then to compare microvascular reactivity assessed on LASCA in control versus Ang-II mice. Methods Thirty 7-week-old wild-type C57BL/6J mice were allocated into two groups. One received angiotensin-II via osmotic minipumps (Ang-II; n=15); the other served as control (n=15). Basal blood flow was measured on LASCA. The PORH test was then performed in the two groups. Results Control mice had significantly lower basal renal microcirculatory flow, expressed in perfusion units (PU), than Ang-II-treated mice (1448 ± 96 vs 1703 ± 185 PU, respectively; P < 0.05). Peak flow was lower in controls than in Ang-II mice (1617±104 vs.1724 ± 205 PU, respectively; P=0.21). Control mice had significantly higher kidney PORH than Ang-II mice (8±3 vs 1±4%, respectively; P < 0.05). Conclusion We developed an innovative technique to study renal microcirculation in mice. Ang-II-treated mice showed significantly higher basal blood flow than controls, while PORH was significantly higher in controls than in Ang-II mice.

In the ongoing search for the optimal biomaterial for tissue engineered vascular grafts (TEVGs), poly (glycerol sebacate) (PGS) has emerged as a new potential candidate. We have utilized a novel method to create unique, pore-free, extruded PGS grafts with and without a supportive exterior layer of polyglycolic acid (PGA). The 1 mm diameter by 5 mm length TEVGs were implanted in a rat model of infrarenal abdominal aorta interposition grafting. Three months after implantation, TEVGs comprised of extruded PGS with an external PGA braid demonstrated a patency rate of 9/10 (90%) with no signs of dilatation, dehiscence, or rupture. The PGS/PGA graft was remodeled into a neoartery with complete endothelialization of the neoartery lumen and formation of smooth muscle actinin multilayers as demonstrated via immunohistochemistry. Formation and maturation of extracellular matrix material were also observed, with amounts of elastin and collagen comparable to native rat aorta. No significant host inflammatory response was observed. These findings suggest the combination of an extruded PGS tube with an external reinforcing PGA braid is a promising material for small diameter TEVGs.

Evidence links osteoporosis and cardiovascular disease but the cellular and molecular mechanisms are unclear. Here we identify skeleton-secreted platelet-derived growth factor-BB (PDGF-BB) as a key mediator of arterial stiffening in response to aging and metabolic stress. Aged mice and those fed high-fat diet (HFD), relative to young mice and those fed normal chow food diet, respectively, had higher serum PDGF-BB and developed bone loss and arterial stiffening. Bone/bone marrow preosteoclasts in aged mice and HFD mice secrete an excessive amount of PDGF-BB, contributing to the elevated PDGF-BB in blood circulation. Conditioned medium prepared from preosteoclasts stimulated proliferation and migration of the vascular smooth muscle cells. Conditional transgenic mice, in which PDGF-BB is overexpressed in preosteoclasts, had 3-fold higher serum PDGF-BB concentration and developed simultaneous bone loss and arterial stiffening spontaneously at a young age. Conversely, in conditional knockout mice, in which PDGF-BB is deleted selectively in preosteoclasts, HFD did not affect serum PDGF-BB concentration; as a result, HFD-induced bone loss and arterial stiffening were attenuated. These studies confirm that preosteoclasts are a main source of excessive PDGF-BB in blood circulation during aging and metabolic stress and establish the role of skeleton-derived PDGF-BB as an important mediator of vascular stiffening.

Tissue transglutaminase (TG2), a multifunctional protein of the transglutaminase family, has putative transamidation-independent functions in aging-associated vascular stiffening and dysfunction. Developing preclinical models will be critical to fully understand the physiologic relevance of TG2’s transamidation-independent activity and to identify the specific function of TG2 for therapeutic targeting. Therefore, in this study, we harnessed CRISPR-Cas9 gene editing technology to introduce a mutation at cysteine 277 in the active site of the mouse Tgm2 gene. Heterozygous and homozygous Tgm2-C277S mice were phenotypically normal and were born at the expected Mendelian frequency. TG2 protein was ubiquitously expressed in the Tgm2-C277S mice at levels similar to those of wild-type (WT) mice. In the Tgm2-C277S mice, TG2 transglutaminase function was successfully obliterated, but the transamidation-independent functions ascribed to GTP, fibronectin, and integrin binding were preserved. In vitro, a remodeling stimulus led to the significant loss of vascular compliance in WT mice, but not in the Tgm2-C277S or TG2−/− mice. Vascular stiffness increased with age in WT mice, as measured by pulse-wave velocity and tensile testing. Tgm2-C277S mice were protected from age-associated vascular stiffening, and TG2 knockout yielded further protection. Together, these studies show that TG2 contributes significantly to overall vascular modulus and vasoreactivity independent of its transamidation function, but that transamidation activity is a significant cause of vascular matrix stiffening during aging. Finally, the Tgm2-C277S mice can be used for in vivo studies to explore the transamidation-independent roles of TG2 in physiology and pathophysiology.

Immune-mediated, drug-induced hepatitis is a rare complication of halogenated volatile anesthetic administration. IL-4-regulated Th2-polarized reactions initiate this type and other types of hepatitis, while the mechanisms that regulate the severity remain elusive. IL-33 is an innate, IL-4-inducing, Th2-polarizing cytokine that has been detected in patients with liver failure and has been associated with upregulated ST2+Foxp3+CD4+CD25+ T cells; however, roles for IL-33 in drug-induced hepatitis are unclear. We investigated IL-33 in an anesthetic, immune-mediated hepatitis modeled in BALB/c, IL-33-/- and ST2-/- mice, as well as in patients with anesthetic hepatitis. The hepatic IL-33 and ST2 levels were elevated in BALB/c mice (p 0.05) with hepatitis, and anti-IL-33 diminished hepatitis (p 0.05) without reducing IL-33 levels. The complete absence of IL-33 reduced IL-10 (p 0.05) and ST2+Foxp3+CD4+CD25+ T cells (p 0.05), as well as reduced the overall survival (p 0.05), suggesting suppressive roles for IL-33 in anesthetic, immune-mediated hepatitis. All of the mice demonstrated similar levels of CD4+ T-cell proliferation following direct T-cell receptor stimulation, but we detected splenic IL-33 and ST2-negative Foxp3+CD4+CD25+ T cells in ST2-/- mice that developed less hepatitis than BALB/c mice (p 0.05), suggesting that ST2-negative Foxp3+CD4+CD25+ T cells reduced hepatitis. In patients, serum IL-33 and IPEX levels were correlated in controls (r

Introduction Emerging research and clinical evidence suggest that severe COVID‐19 is a microvascular disease, where SARS‐CoV‐2 infection triggers a rapid inflammatory vascular response that leads to endothelial dysfunction and thrombosis. Underlying medical conditions such as obesity, type 2 diabetes and hypertension, have been associated with increased risk for severe illness. SARS‐CoV‐2 enters cells by surface spike protein binding to host cell receptor angiotensin‐converting enzyme 2 (ACE2). Isolated S protein of SARS‐CoV‐1 has been shown to induce an innate immune response. Here we investigate the cytokine response of monocytes with and without comorbidities (obesity and hypertension) exposed to SARS‐CoV‐2 spike protein, and the effects of this response on endothelial barrier function. Methods Human CD14+ monocytes (Lonza, Precision for Medicine) from two Caucasian males in their 50s, one with obesity and hypertension (HTN) and one without, were stimulated with LPS (100 ng/mL [positive control]), recombinant spike receptor‐binding domain (RBD, 10 ug/mL) or serum‐free media (negative control) for 48 hours. Monocyte conditioned media (MCM) was collected and cytokines (IL‐6, IL‐8, IL‐10, IL‐12p70, IL‐1beta, IFN‐gamma, TNF‐alpha, IL‐4) were analyzed by multiplex ELISA. Human lung microvascular endothelial cells (HLMVECs) from a healthy donor were exposed to MCM from healthy or HTN subjects. Endothelial barrier function was measured by electric cell‐substrate impedance sensing (ECIS). Briefly, HLMVECs were seeded on ECIS chambers to proliferate until impedance plateaued. Half of the media was then replaced with MCM. Differences in impedance drops were compared among various conditions. Western blotting was used to investigate Spike RBD internalization. Results Spike RBD and resulted in increased IL‐6, IL‐8, IL‐12p70, and TNF‐alpha compared to negative control (Fig1A). Monocytes from HTN subject showed increased secretion of IL‐6, IL‐8 and IL‐12p70 compared to those from the healthy subject (Fig 1B). HLMVECs showed moderate long‐term barrier disruption, when treated with Spike RBD alone and Spike RBD with MCM from healthy subjects and no difference in transient barrier disruption or recovery. HLMVECs exposed to MCM from HTN subjects showed increased long‐term barrier dysfunction, especially with Spike RBD present, and recovery of barrier function was also hampered (Fig 2). Spike RBD was observed to be internalized by both monocytes and HLMVECs. Discussion Spike RBD alone induces inflammatory cytokine secretion by CD14+ monocytes and is further increased in monocytes from the obese/HTN subject. Exposure to Spike RBD and MCM from both healthy and HTN subjects caused significant long‐term endothelial barrier dysfunction in HLMVECs with increased dysfunction seen for the obese/HTN MCM. These results are consistent with clinical experience with the development of acute respiratory distress syndrome, increased disease severity, and worse outcome in COVID‐19 patients with comorbidities. Further work is being done to characterize the cytokine profile and mechanisms of barrier dysfunction.

The lysyl oxidase family of enzymes (LOXs) catalyze oxidative deamination of lysine side chains on collagen and elastin to initialize cross-linking that is essential for the formation of the extracellular matrix (ECM). Elevated expression of LOXs is highly associated with diverse disease processes. To date, the inability to detect total LOX catalytic function in situ has limited the ability to fully elucidate the role of LOXs in pathobiological mechanisms. Using LOXL2 as a representative member of the LOX family, we developed an in situ activity assay by utilizing the strong reaction between hydrazide and aldehyde to label the LOX-catalyzed allysine (-CHO) residues with biotin-hydrazide. The biotinylated ECM proteins are then labeled via biotin-streptavidin interaction and detected by fluorescence microscopy. This assay detects the total LOX activity in situ for both overexpressed and endogenous LOXs in cells and tissue samples and can be used for studies of LOXs as therapeutic targets.

Summary Heterozygous gain-of-function (GOF) mutations of hypoxia-inducible factor 2α (HIF2A), a key hypoxia-sensing regulator, are associated with erythrocytosis, thrombosis, and vascular complications that account for morbidity and mortality of patients. We demonstrated that the vascular pathology of HIF2A GOF mutations is independent of erythrocytosis. We generated HIF2A GOF-induced pluripotent stem cells (iPSCs) and differentiated them into endothelial cells (ECs) and smooth muscle cells (SMCs). Unexpectedly, HIF2A-SMCs, but not HIF2A-ECs, were phenotypically aberrant, more contractile, stiffer, and overexpressed endothelin 1 (EDN1), myosin heavy chain, elastin, and fibrillin. EDN1 inhibition and knockdown of EDN1-receptors both reduced HIF2-SMC stiffness. Hif2A GOF heterozygous mice displayed pulmonary hypertension, had SMCs with more disorganized stress fibers and higher stiffness in their pulmonary arterial smooth muscle cells, and had more deformable pulmonary arteries compared with wild-type mice. Our findings suggest that targeting these vascular aberrations could benefit patients with HIF2A GOF and conditions of augmented hypoxia signaling., Graphical abstract, Highlights • HIF2-SMCs are stiffer than WT-SMCs and differ in contractile SMC marker expression • HIF2-SMCs and WT-SMCs differ in EDN1 production and ECM composition • HIF- 2α induces EDN1; EDNI subsequently induces SMC stiffening • Hif2A GOF mouse arterial SMCs have more disorganized stress fibers and are stiffer, Pathophysiology; Biophysics; Biomechanics

Solar energy is one of the most promising renewable energy that has accelerated and globally about 630 GW has been installed so far. And it projected to reach 8500 GW by 2050 as per IRENA. Solar photovoltaic panels have typically 15-20% efficiency in capturing the incident sunlight. And as the market is maturing, new avenues of research are focused on improving solar PV efficiency at cell level, module level and by adopting solar tracking. Solar photovoltaic panels (PV) are typically mounted at an optimum tilt angle according to the latitude and generally known as Fixed tit deployment. Solar tracking is an alternative methodology to maximize energy captured by a PV panel and is achieved by tracking the sun. This can give an efficiency gain of up to 25% w.r.t fixed tilt but at an additional capital cost of 20%. At Renkube we have developed an innovative PV panel design called MFOT (Motion Free Optical Tracking) that can increase the energy generation of module by the same quantum of 20% as physical trackers but at an additional capital cost of 5-10%. The MFOT panel uses prismatic structures that work on the principal of Total Internal Reflection to increase sunlight incident on solar cell. BDRF (Bi-Directional Reflectance Function) based mirrors is another alternative technology built at Michigan Technology University to boost the illumination on solar cells using mirrors and improve energy generation by up to 20% more. In this paper, we compare the pros and cons of BDRF and MFOT technologies and take a deep dive on various factors such as annual performance gain, geographic constraints, and highlight the seasonal improvements of these systems.

Heterozygous gain-of-function (GOF) mutations of hypoxia-inducible factor 2α (HIF2A), a significant regulator of hypoxia sensing, are associated with erythrocytosis, thrombosis and vascular complications that account for morbidity and mortality of patients with these disorders. We demonstratethat vascular pathology of HIF2A GOF mutations is independent of erythrocytosis. We generated HIF2A GOF induced pluripotent stem cells (iPSCs) and differentiated them into endothelial cells (ECs) and smooth muscle cells (SMCs). Unexpectedly, the HIF2A-SMCs, but not HIF2A-ECs, were phenotypically aberrant, more contractile and stiffer, and overexpressed endothelin 1(EDN1), myosin heavy chain, elastin and fibrillin. EDN1 inhibition or knockdown of EDN1-receptors reduced HIF2-SMC stiffness. Hif2A GOF heterozygous mice displayed early onset of pulmonary hypertension, had SMCs with more disorganized stress fibers and higher stiffness in their pulmonary arterial vascular smooth muscle cells, and more deformable main pulmonary arteries compared with wild type mice. We propose that targeting these vascular aberrations may benefit patients with HIF2A GOF and other conditions ofaugmented hypoxia signaling.

Purpose: To determine whether the absence of transglutaminase 2 enzyme (TG2) in TG2 knockout mice (TG2-/-) protect them against early age-related functional and histological arterial changes. Methods: Pulse wave velocity (PWV) was measured using non-invasive Doppler and mean arterial pressure (MAP) was measured in awake mice using tail-cuff system. Thoracic aortas were excised for evaluation of endothelial dependent vasodilation (EDV) by wire myography, as well as histological analyses. Results: PWV and MAP were similar in TG2-/-mice to age-matched wild type (WT) control mice. Old WT mice exhibited a markedly attenuated EDV as compared to young WT animals. The TG2-/-young and old mice had enhanced EDV responses (p

Despite significant research efforts, clinical practice for arterial bypass surgery has been stagnant, and engineered grafts continue to face postimplantation challenges. Here, we describe the development and application of a durable small-diameter vascular graft with tailored regenerative capacity. We fabricated small-diameter vascular grafts by electrospinning fibrin tubes and poly(ε-caprolactone) fibrous sheaths, which improved suture retention strength and enabled long-term survival. Using surface topography in a hollow fibrin microfiber tube, we enable immediate, controlled perfusion and formation of a confluent endothelium within 3–4 days in vitro with human endothelial colony-forming cells, but a stable endothelium is noticeable at 4 weeks in vivo. Implantation of acellular or endothelialized fibrin grafts with an external ultrathin poly(ε-caprolactone) sheath as an interposition graft in the abdominal aorta of a severe combined immunodeficient Beige mouse model supports normal blood flow and vessel patency for 24 weeks. Mechanical properties of the implanted grafts closely approximate the native abdominal aorta properties after just 1 week in vivo. Fibrin mediated cellular remodeling, stable tunica intima and media formation, and abundant matrix deposition with organized collagen layers and wavy elastin lamellae. Endothelialized grafts evidenced controlled healthy remodeling with delayed and reduced macrophage infiltration alongside neo vasa vasorum-like structure formation, reduced calcification, and accelerated tunica media formation. Our studies establish a small-diameter graft that is fabricated in less than 1 week, mediates neotissue formation and incorporation into the native tissue, and matches the native vessel size and mechanical properties, overcoming main challenges in arterial bypass surgery.

Background Ischemia-reperfusion injury is characterized by an increase in oxidative stress and leads to significant morbidity and death. The tyrosine kinase c-Abl is activated by oxidative stress and mediates processes that affect endothelial barrier function. We hypothesized treatment with the c-Abl inhibitor imatinib would be protective against ischemia-reperfusion injury in our ex vivo rabbit model. Methods Heart-lung blocs were harvested from rabbits and stored in cold in Perfadex (Vitrolife, Englewood, CO) for 18 hours. Blocs were reperfused for 2 hours in an ex vivo circuit with donor rabbit blood alone (untreated group, n = 7) or donor rabbit blood and 4 mg imatinib (treatment group, n = 10). Serial clinical variables measured every 15 minutes (arterial oxygen and carbon dioxide tension and mean pulmonary artery pressures) and biochemistry of tissue samples before and after reperfusion were assessed. Results Compared with untreated lungs, imatinib treatment improved physiologic parameters, including oxygen, carbon dioxide, and pulmonary artery pressures. Imatinib-treated lungs had less vascular barrier dysfunction as quantified by wet-to-dry weight ratios and bronchoalveolar lavage protein concentrations. Treated lungs showed less inflammation as measured by bronchoalveolar lavage myeloperoxidase assay, less mitochondrial reactive oxygen species production, and increased antioxidant catalase levels. Finally, imatinib protected lungs from DNA damage and p53 upregulation. Conclusions Imatinib treatment significantly improved the physiologic performance of reperfused lungs and biochemical indicators associated with reperfusion injury in this ex vivo model. Further study is necessary to elucidate the mechanism of tyrosine kinase inhibition in lungs exposed to ischemia and reperfusion.

Depressed right ventricular ejection fraction (RVEF) has clear prognostic significance in patients with pulmonary arterial hypertension (PAH). Accordingly, improvements in RVEF represent a desirable end-point in the development of PAH therapies. However, current methods for determination of RVEF require measurement of RV volume and are relatively complex and costly. Here, we validate a novel method for quantitative estimation of RVEF in rats based entirely upon analysis of readily available RV pressure waveforms that eliminates the need for simultaneous volume measurement and can be rapidly applied. Right ventricular pressure and volume (conductance catheter) measurements acquired from 15 rats (7 controls, 8 sugen/hypoxia PAH; 220–250 g) were used for the study. Over the same 10 beat interval, RVEF was directly measured from the volume signal and estimated from the pressure signal. Simultaneous measures were compared by linear regression and Bland-Altman analysis to define bias (accuracy) and precision. Measured RVEF ranged from 0.19 to 0.60 (mean 0.44 ± 0.10) and estimated from 0.19 to 0.52 (mean 0.42 ± 0.09). Across the dataset there was strong correlation (r2 = 0.813), with minimal bias (0.01) and an overall error of 20% consistent with acceptable accuracy and precision. Study results support the potential utility of a method based entirely upon analysis of the RV pressure waveform for assessing drug effects on RVEF in rat models of PAH.

Women who have had preeclampsia have increased cardiovascular disease risk; however, the mechanism(s) responsible for this association remain unclear. Microvascular damage sustained during a preeclamptic pregnancy may persist postpartum. The putative mechanisms mediating this dysfunction include a reduction in NO-dependent dilation and an increased sensitivity to angiotensin II. In this study, we evaluated endothelium-dependent dilation, angiotensin II sensitivity, and the therapeutic effect of angiotensin II receptor blockade (losartan) on endothelium-dependent dilation in vivo in the microvasculature of women with a history of preeclampsia (n=12) and control women who had a healthy pregnancy (n=12). We hypothesized that preeclampsia would have (1) reduced endothelium-dependent dilation, (2) reduced NO-mediated dilation, and (3) increased sensitivity to angiotensin II. We further hypothesized that localized losartan would increase endothelium-dependent vasodilation in preeclampsia. We assessed microvascular endothelium-dependent vasodilator function by measurement of cutaneous vascular conductance responses to graded infusion of acetylcholine (acetylcholine; 10 −7 –102 mmol/L) and a standardized local heating protocol in control sites and sites treated with 15 mmol/L L-NAME ( N G -nitro- l -arginine methyl ester; NO-synthase inhibitor) or 43 µmol/L losartan. Further, we assessed microvascular vasoconstrictor sensitivity to angiotensin II (10 −20 –10 −4 mol/L). Preeclampsia had significantly reduced endothelium-dependent dilation (−0.3±0.5 versus −1.0±0.4 log EC50 ; P P =0.006). Preeclampsia also had augmented vasoconstrictor sensitivity to angiotensin II (−10.2±1.3 versus −8.3±0.5; P =0.006). Angiotensin II type I receptor inhibition augmented endothelium-dependent vasodilation and NO-dependent dilation in preeclampsia but had no effect in healthy pregnancy. These data suggest that women who have had preeclampsia have persistent microvascular dysfunction postpartum, mediated, in part, by increased sensitivity to angiotensin II.