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Patients on continuous flow ventricular assist devices (CF-VADs) are at high risk for the development of Acquired von-Willebrand Syndrome (AVWS) and non-surgical bleeding. von Willebrand Factor (vWF) plays an essential role in maintaining hemostasis via platelet binding to the damaged endothelium to facilitate coagulation. In CF-VAD patients, degradation of vWF into low MW multimers that are inefficient in facilitating coagulation occurs and has been primarily attributed to the supraphysiological shear stress associated with the CF-VAD impeller.In this review, we evaluate information from the literature regarding the unraveling behavior of surface-immobilized vWF under pulsatile and continuous flow pertaining to: (A) the process of arterial endothelial vWF production and release into circulation, (B) the critical shear stress required to unravel surface bound versus soluble vWF which leads to degradation, and (C) the role of pulsatility in on the production and degradation of vWF.Taken together, these data suggests that the loss of pulsatility and its impact on arterial endothelial cells plays an important role in the production, release, unraveling, and proteolytic degradation of vWF into low MW multimers, contributing to the development of AVWS. Restoration of pulsatility can potentially mitigate this issue by preventing AVWS and minimizing the risk of non-surgical bleeding.

Due to the rapidly growing number of older people worldwide and the concomitant increase in cardiovascular complications, there is an urgent need for age-related cardiac disease modeling and drug screening platforms. In the present study, we developed a cardiac tissue chip model that incorporates hemodynamic loading and mimics essential aspects of the infarcted aging heart. We induced cellular senescence in H9c2 myoblasts using low-dose doxorubicin treatment. These senescent cells were then used to engineer cardiac tissue fibers, which were subjected to hemodynamic stresses associated with pressure-volume changes in the heart. Myocardial ischemia was modeled in the engineered cardiac tissue via hypoxic treatment. Our results clearly show that acute low-dose doxorubicin treatment-induced senescence, as evidenced by morphological and molecular markers, including enlarged and flattened nuclei, DNA damage response foci, and increased expression of cell cycle inhibitor p16INK4a, p53, and ROS. Under normal hemodynamic load, the engineered cardiac tissues demonstrated cell alignment and retained cardiac cell characteristics. Our senescent cardiac tissue model of hypoxia-induced myocardial infarction recapitulated the pathological disease hallmarks such as increased cell death and upregulated expression of ANP and BNP. In conclusion, the described methodology provides a novel approach to generate stress-induced aging cardiac cell phenotypes and engineer cardiac tissue chip models to study the cardiovascular disease pathologies associated with aging.

Introduction: Cardiovascular disease is the primary cause of death amongst end-stage renal disease (ESRD) patients. Though arteriovenous fistulas (AVFs) are the access of choice for hemodialysis, joining a high-pressure artery and low-pressure vein leads to cardiac volume overload acutely. Debate exists as to the cardiac ramifications of AVFs, due in part to the difficulty of recruiting ESRD patients and controls for prospective studies. Animal models have been essential in AVF studies, but their usefulness is limited by interspecies differences in physiology and other factors. Thus, we have developed a three-dimensional (3D) cardiac tissue chip with tunable pressure and stretch to model the acute hemodynamic changes associated with AVF creation. Hypothesis: In this study, we aimed to replicate the hemodynamics of murine AVF models in vitro and hypothesized that if 3D cardiac constructs were subjected to “volume overload”, they would display fibrosis and key gene expression changes seen in AVF mice. Methods: Mice underwent either AVF or sham procedure and were monitored for 28 d. Cardiac tissue constructs composed of h9c2 rat cardiac myoblasts and normal adult human dermal fibroblasts in hydrogel were seeded into devices and exposed for 96 h to 100 mmHg/10 mmHg pressure (0.4 s/0.6 s) at 1 Hz. "Systolic" pressure was generated via pneumatic pump while a hydrostatic pressure head gave rise to "diastolic" pressure. The controls were exposed to “normal” stretch while the experimental group was exposed to “volume overload”. Results and Conclusions: The in vitro model yielded similar fibrosis-related gene expression profiles (see figure) and patterns of fibrosis as the murine model.

Small-diameter arterial conduits with native physiological and biological equivalence continues to be a constant global demand posing critical challenges in fabrication. Advent of various strategies towards mimicking the structural hierarchy of a native blood vessel, often involve complex instrumentation and template-assistance with post-processing complications eventually compromising structural fidelity. In the present research, we report a template-free, facile strategy- ‘3D wet writing’ by peripheral-core differential ionic gelation to fabricate perfusable customizable constructs of any dimension, thickness and length in α-SMA) and endothelial (CD-31) cells in BLT were comparable to native hierarchical cellular organization with the multi-layered medial and mono-layered intimal layers. Further, ex-vivo dynamic studies on anastomotic interface between BLT and rat abdominal aorta clearly evidenced the functional efficacy of fabricated BLTs as physiologically relevant small-diameter vascular construct.

Cardiopulmonary bypass (CPB) results in short-term (3–5 h) exposure to flow with diminished pulsatility often referred to as “continuous flow”. It is unclear if short-term exposure to continuous flow influences endothelial function, particularly, changes in levels of pro-inflammatory and pro-angiogenic cytokines. In this study, we used the endothelial cell culture model (ECCM) to evaluate if short-term (≤5 h) reduction in pulsatility alters levels of pro-inflammatory/pro-angiogenic cytokine levels. Human aortic endothelial cells (HAECs) cultured within the ECCM provide a simple model to evaluate endothelial cell function in the absence of confounding factors. HAECs were maintained under normal pulsatile flow for 24 h and then subjected to continuous flow (diminished pulsatile pressure and flow) as observed during CPB for 5 h. The ECCM replicated pulsatility and flow morphologies associated with normal hemodynamic status and CPB as seen with clinically used roller pumps. Levels of angiopoietin-2 (ANG-2), vascular endothelial growth factor-A (VEGF-A), and hepatocyte growth factor were lower in the continuous flow group in comparison to the pulsatile flow group whereas the levels of endothelin-1 (ET-1), granulocyte colony stimulating factor, interleukin-8 (IL-8) and placental growth factor were higher in the continuous flow group in comparison to the pulsatile flow group. Immunolabelling of HAECs subjected to continuous flow showed a decrease in expression of ANG-2 and VEGF-A surface receptors, tyrosine protein kinase-2 and Fms-related receptor tyrosine kinase-1, respectively. Given that the 5 h exposure to continuous flow is insufficient for transcriptional regulation, it is likely that pro-inflammatory/pro-angiogenic signaling observed was due to signaling molecules stored in Weible-Palade bodies (ET-1, IL-8, ANG-2) and via HAEC binding/uptake of soluble factors in media. These results suggest that even short-term exposure to continuous flow can potentially activate pro-inflammatory/pro-angiogenic signaling in cultured HAECs and pulsatile flow may be a successful strategy in reducing the undesirable sequalae following continuous flow CPB.

Continuous Flow Ventricular Assist Device (CFVAD) support in advanced heart failure patients causes diminished pulsatility, which has been associated with adverse events including gastrointestinal bleeding, end organ failure and arteriovenous malformation. Recently, pulsatility augmentation by pump speed modulation has been proposed as a means to minimize adverse events. Pulsatility primarily affects endothelial and smooth muscle cells in the vasculature. To study the effects of pulsatility and pulse modulation using CFVADs, we have developed a microfluidic co-culture model with human aortic endothelial (ECs) and smooth muscle cells (SMCs) that can replicate physiological pressures, flows, shear stresses, and cyclical stretch. The effects of pulsatility and pulse frequency on EC and SMC were evaluated during (1) normal pulsatile flow (120/80 mmHg, 60 bpm), (2) diminished pulsatility (98/92 mmHg, 60 BPM), and (3) low cyclical frequency (120/80 mmHg, 30 bpm). Shear stresses were estimated using computational fluid dynamics (CFD) simulations. While average shear stresses (4.2 dyne/cm2) and flows (10.1 ml/min) were similar, the peak shear stresses for normal pulsatile flow (16.9 dyne/cm2) and low cyclic frequency (19.5 dyne/cm2) were higher compared to diminished pulsatility (6.45 dyne/cm2). ECs and SMCs demonstrated significantly lower cell size with diminished pulsatility compared to normal pulsatile flow. Low cyclical frequency resulted in normalization of EC cell size but not SMCs. SMCs size was higher with low frequency condition compared to diminished pulsatility but did not normalize to normal pulsatility condition. These results may suggest that pressure amplitude augmentation may have a greater effect in normalizing ECs while both pressure amplitude and frequency may be required to normalize SMCs morphology. The co-culture model may be an ideal platform to study flow modulation strategies.

BACKGROUND: Patients with continuous flow ventricular assist devices (CF-VADs) are at high risk for non-surgical bleeding, speculated to associate with the loss of pulsatility following CF-VAD placement. It has been hypothesized that continuous shear stress causes elongation and increased enzymatic degradation of von Willebrand Factor (vWF), a key player in thrombus formation at sites of vascular damage. However, the role of loss of pulsatility on the unravelling behavior of vWF has not been widely explored. METHODS: vWF molecules were immobilized on the surface of microfluidic devices and subjected to various pulsatile flow profiles, including continuous flow and pulsatile flow of different magnitudes, dQ/dt (i.e. first derivative of flow rate) of pulsatility and pulse frequencies to mimic in vivo shear flow environments with and without CF-VAD support. VWF elongation was observed using total internal reflection fluorescence (TIRF) microscopy. Besides, vWF level is measured from patients’ blood sample before and after CF-VAD implantation from a clinical perspective. To our knowledge, this work is the first in providing direct, visual observation of single vWF molecule extension under controlled -pulsatile shear flow. RESULTS: Unravelling of vWF (total sample size n ~ 200 molecules) is significantly reduced under pulsatile flow (P < 0.01) compared to continuous flow. An increase in magnitude of pulsatility further reduces unravelling lengths, while lower frequency of pulsatility (20 vs. 60 pulses per min) does not have a major effect on the maximum or minimum unravelling lengths. Evaluation of CF-VAD patient blood samples (n = 13) demonstrates that vWF levels decreased by ~40% following CF-VAD placement (p < 0.01), which correlates to single-molecule observations from a clinical point of view. CONCLUSIONS: Pulsatile flow reduces unfolding of vWF compared to continuous flow and a lower pulse frequency of 20 pulses/minute yielded comparable vWF unfolding to 60 pulses/minute. These findings could shed light on non-surgical bleeding associated with the loss of pulsatility following CF-VAD placement

Introduction: With the rise in the elderly population, there has been an exponential growth in cardiovascular diseases and age-related complications. This necessitates a platform for studying cardiovascular disease in the context of aging. Hypothesis: An engineered cardiac tissue model that can recapitulate critical aspects of aging can be used to study age-related diseases of the cardiovascular system. Methods: Senescence was induced in rat cardiomyoblasts using an acute low-dose doxorubicin treatment. The presence of important senescent markers in the cells like enlarged and flattened nuclei, increased ROS activity, elevated p53 production, DNA damage response foci, and increased expression of cell cycle inhibitor p16 INK4a was evaluated. These senescent cells were then used to engineer cardiac tissue, which was subjected to hemodynamic stresses associated with the pressure-volume changes in the heart. Myocardial ischemia was imposed in the aging cardiac tissue model using hypoxic treatment. Results: Under normal hemodynamic loading, the engineered cardiac tissue retained its cardiac cell characteristics and showed cell alignment along with age-related changes in structure and gene expression. The myocardial ischemic model of the tissue revealed major pathological hallmarks of the disease like increased cell death and natriuretic peptide expression. Conclusion: Our model and methodology provide an effective platform for studying the cardiovascular disease pathologies associated with aging and screening drugs against age-related complications.

Introduction: Patients implanted with Continuous Flow Ventricular Assisted Devices (CF VADs) exhibit diminished pulsatility and are at a high risk for developing acquired von Willebrand Factor syndrome (AVWS) and non-surgical bleeding. This study aimed to understand how diminished pulsatility due to CF VAD impacts unravelling and patient plasma levels of von Willebrand Factor (vWF). A microfluidic approach was used to study unravelling of vWF under normal pulsatile flow and flow with diminished pulsatility. In addition, vWF levels in CF-VAD patients was measured to determine vWF levels in circulation. Hypothesis: We hypothesized that diminished pulsatility increases vWF unravelling, likely leading to increased vWF degradation and elevated levels of low MW vWF fragments in circulation, this in turn leads to decreased endothelial vWF production in CF-VAD patients. Methods: vWF molecules were immobilized in a microfluidic device and subjected to either normal pulsatile flow or flow with diminished pulsatility (same mean flow). vWF unravelling behavior was observed using total internal reflection fluorescence (TIRF) microscopy. Patient blood samples were collected 1-2 days pre CF-VAD implant and monthly post-implant. Patient plasma vWF levels were measured using an ELISA kit. Results: TIRF imaging showed that vWF molecules undergo unravelling and significantly greater elongation (pFig.1A ). Evaluation of plasma vWF levels in patients (n=9) showed that vWF levels decreased progressively following CF-VAD placement ( Fig.1B ). These results suggest that diminished pulsatility increased unravelling of vWF and exposure of ADAMTS13 binding sites, potentially leading to enhanced cleavage of vWF into low molecular weight (MW) multimers. Review of literature suggests that both low MW multimers and diminished pulsatility cause endothelial dysfunction and decreased endothelial vWF production, which was evident in patient samples. Conclusion: Diminished pulsatility may independently promote vWF degradation and lead to decreased production of vWF, thus contributing to AVWS.

Atherosclerosis prevalence is increased in chronic obstructive pulmonary disease (COPD) patients, independent of other risk factors. The etiology of the excess vascular disease in COPD is unknown, although it is presumably related to an underlying (if cryptic) systemic immune response. Autoantibodies with specificity for glucose-regulated protein 78 (GRP78), a multifunctional component of the unfolded protein response, are common in COPD patients and linked to comorbidities of this lung disease. We hypothesized anti-GRP78 autoreactivity might also be a risk factor for atherosclerosis in COPD patients. Carotid intima-medial thickness (cIMT) was measured in 144 current and former smokers by ultrasound. Concentrations of circulating IgG autoantibodies against full-length GRP78, determined by ELISA, were greater among subjects with abnormally increased cIMT (p < 0.01). Plasma levels of autoantibodies against a singular GRP78 peptide segment, amino acids 246–260 (anti-GRP78aa 246–260), were even more highly correlated with cIMT, especially among males with greater than or equal to moderate COPD (rs = 0.62, p = 0.001). Anti-GRP78aa 246–260 concentrations were independent of CRP, IL-6, and TNF-α levels. GRP78 autoantigen expression was upregulated among human aortic endothelial cells (HAECs) stressed by incubation with tunicamycin (an unfolded protein response inducer) or exposure to culture media flow disturbances. Autoantibodies against GRP78aa 246–260, isolated from patient plasma by immunoprecipitation, induced HAEC production of proatherosclerotic mediators, including IL-8. In conclusion, anti-GRP78 autoantibodies are highly associated with carotid atherosclerosis in COPD patients and exert atherogenic effects on HAECs. These data implicate Ag-specific autoimmunity in the pathogenesis of atherosclerosis among COPD patients and raise possibilities that directed autoantibody reduction might ameliorate vascular disease in this high-risk population.

Doxorubicin (DOX, an anthracycline) is a widely used chemotherapy agent against various forms of cancer; however, it is also known to induce dose-dependent cardiotoxicity leading to adverse complications. Investigating the underlying molecular mechanisms and strategies to limit DOX-induced cardiotoxicity might have potential clinical implications. Our previous study has shown that expression of microRNA-377 (miR-377) increases in cardiomyocytes (CMs) after cardiac ischemia-reperfusion injury in mice, but its specific role in DOX-induced cardiotoxicity has not been elucidated. In the present study, we investigated the effect of anti-miR-377 on DOX-induced cardiac cell death, remodeling, and dysfunction. We evaluated the role of miR-377 in CM apoptosis, its target analysis by RNA sequencing, and we tested the effect of AAV9-anti-miR-377 on DOX-induced cardiotoxicity and mortality. DOX administration in mice increases miR-377 expression in the myocardium. miR-377 inhibition in cardiomyocyte cell line protects against DOX-induced cell death and oxidative stress. Furthermore, RNA sequencing and Gene Ontology (GO) analysis revealed alterations in a number of cell death/survival genes. Intriguingly, we observed accelerated mortality and enhanced myocardial remodeling in the mice pretreated with AAV9-anti-miR-377 followed by DOX administration as compared to the AAV9-scrambled-control-pretreated mice. Taken together, our data suggest that in vitro miR-377 inhibition protects against DOX-induced cardiomyocyte cell death. On the contrary, in vivo administration of AAV9-anti-miR-377 increases mortality in DOX-treated mice.

BackgroundHeart Failure (HF) is the leading cause of death worldwide. Myocardial fibrosis, one of the clinical manifestations implicated in almost every form of heart disease, contributes significantly to HF development. However, there is no approved drug specifically designed to target cardiac fibrosis. Nintedanib (NTB) is an FDA approved tyrosine kinase inhibitor for idiopathic pulmonary fibrosis (IPF) and chronic fibrosing interstitial lung diseases (ILD). The favorable clinical outcome of NTB in IPF patients is well established. Furthermore, NTB is well tolerated in IPF patients irrespective of cardiovascular comorbidities. However, there is a lack of direct evidence to support the therapeutic efficacy and safety of NTB in cardiac diseases.Methods and ResultsWe examined the effects of NTB treatment on cardiac fibrosis and dysfunction using a murine model of HF. Specifically, 10 weeks old C57BL/6J male mice were subjected to Transverse Aortic Constriction (TAC) surgery. NTB was administered once daily by oral gavage (50mg/kg) till 16 weeks post-TAC. Cardiac function was monitored by serial echocardiography. Histological analysis and morphometric studies were performed at 16 weeks post-TAC. In the control group, systolic dysfunction started developing from 4 weeks post-surgery and progressed till 16 weeks. However, NTB treatment prevented TAC-induced cardiac functional decline. In another experiment, NTB treatment was stopped at 8 weeks, and animals were followed till 16 weeks post-TAC. Surprisingly, NTB’s beneficial effect on cardiac function was maintained even after treatment interruption. NTB treatment remarkably reduced cardiac fibrosis as confirmed by Masson’s trichome staining and decreased expression of collagen genes (COL1A1, COL3A1). Compared to TAC group, NTB treated mice showed lower HW/TL ratio and cardiomyocyte cross-sectional area. Our in vitro studies demonstrated that NTB prevents myofibroblast transformation, TGFβ1-induced SMAD3 phosphorylation, and production of fibrogenic proteins (Fibronectin-1). However, NTB significantly altered vital signaling pathways in both, isolated fibroblast and cardiomyocytes, suggesting that its biological effect and underlying cardiac protection mechanisms are not limited to fibroblast and fibrosis alone.ConclusionOur findings provide a proof of concept for repurposing NTB to combat adverse myocardial fibrosis and encourage the need for further validation in large animal models and subsequent clinical development for HF patients.

The mechanical rotary blood pumps (RBP) have been designed to provide sufficient physiological perfusion and prevent ventricular collapse caused by suction events for the congestive heart failure (HF) patients. Various control systems could be one of the most crucial objectives for developing RBPs. Some control algorithms need implantable sensors, but they are unreliable due to sensor error, pump thrombus, or short lifespan, etc. Other sensorless control algorithms can eliminate any unreliable sensor but to date those strategies have not been successfully incorporated into the RBPs in clinical. To overcome the above limitations, in this study a new physiological control strategy for RBPs has been proposed. This method depends on a recently developed implantable wireless sensor called CardioMEMS, which can provide hemodynamic information for pulmonary artery pressure (PAP). In this algorithm, a gain-scheduled proportional-integral controller is used to maintain the actual mean PAP measurements close to a user-defined threshold to provide sufficient physiologic perfusion. The algorithm is tested in-silico with (1) reference mean PAP (MPAP) of 17 mmHg and the threshold of MPAP as 15 and 19 mmHg due to ±2 mmHg sensor drift during rest and exercise conditions with normal and increased pulmonary vascular resistance (PVR); (2) physiological state quickly changes between rest and exercise with normal PVR for (1); and (3) actual MPAP measurements with 5% and 10% uniformly distributed noise for (1) and (2). Simulation results demonstrated that with the CardioMEMS sensor the proposed control algorithm can achieve adequate physiologic perfusion with satisfied efficacy and robustness.

Objective: The rotary right ventricular assist devices (RVAD) are mechanical pumps used to provide long-term circulatory support for the patients with right heart failure, which often occurs after occurrence of left heart failure or on its own. In this study, we proposed a new sensorless and suction index (SI) based control algorithm in order to provide sufficient cardiac output and achieve suction avoidance under varying physical activities. Methods: The proposed SI control strategy used a gain-scheduled proportional-integral (PI) controller to maintain the actual calculated values of SI close to a user-defined reference value. SI was extracted based on the RVAD flow rates, which were estimated from the intrinsic pump parameter (noisy pump speed measurements) using Golay-Savitzky (GS) filters. A nonlinear model of the human circulatory system was coupled with the RVAD to evaluate performance of the SI control strategy in-silico. The proposed SI control algorithm was compared to the constant pump speed (RPM) control strategy during (1) rest and exercise conditions, and (2) a rapid 2-fold increase in vena caval resistance (VCR) for (1). Results and Conclusion: The SI control strategy effectively avoided suction events while providing sufficient cardiac output during varying physiologic conditions and was better than the constant RPM control strategy. Significance: The proposed SI control method can eliminate the unreliable and non-long-term used sensors, and can be easily applied to current pumps for suction prevention and physiological perfusion.

Blood-based liquid biopsies provide a minimally invasive alternative to identify cellular and molecular signatures that can be used as biomarkers to detect early-stage cancer, predict disease progression, longitudinally monitor response to chemotherapeutic drugs, and provide personalized treatment options. Specific targets in blood that can be used for detailed molecular analysis to develop highly specific and sensitive biomarkers include circulating tumor cells (CTCs), exosomes shed from tumor cells, cell-free circulating tumor DNA (cfDNA), and circulating RNA. Given the low abundance of CTCs and other tumor-derived products in blood, clinical evaluation of liquid biopsies is extremely challenging. Microfluidics technologies for cellular and molecular separations have great potential to either outperform conventional methods or enable completely new approaches for efficient separation of targets from complex samples like blood. In this article, we provide a comprehensive overview of blood-based targets that can be used for analysis of cancer, review microfluidic technologies that are currently used for isolation of CTCs, tumor derived exosomes, cfDNA, and circulating RNA, and provide a detailed discussion regarding potential opportunities for microfluidics-based approaches in cancer diagnostics.

Over the past two decades, rotary blood pumps (RBPs) have gained clinical acceptance and market share due to their smaller size, and increased efficiency and durability compared to pulsatile blood pumps. RBPs constitute the second and third generations of the artificial hearts. As a continuous flow system, RBP augments perfusion and provides sufficient systemic perfusion for patients, while reducing ventricular work. RBP can unload the native ventricles continuously as partial or full support device. RBP consists of a rotating impeller, which is enclosed in a housing. The impeller can be mainly classified into axial flow (AF) and centrifugal flow (CF), though mixed flow (MF) pumps have also been developed. The Archimedes screw was used to design the AF pumps, where the direction of blood flow is parallel to the central axis of the impeller. Most AF RBPs belong to second-generation pumps and can operate at speeds of 7000–50,000 rpm. In comparison, CF pumps have a flow direction that is perpendicular to the central rotational axis of the impeller. Centrifugal pumps typically are larger in diameter, smaller in length, and have higher hydraulic efficiencies and the speeds are lower than those of AF pumps. Axial and centrifugal pumps are suspended using physical bearings, hydrodynamic bearings, or are magnetically levitated. This chapter will introduce AF and CF pumps in design, performance, and the comparisons in their clinical applications.

Objective: Continuous Flow Left Ventricular Assist Devices (CFLVAD) are circulatory support devices that are implanted in patients with end-stage heart failure. We developed a novel control algorithm for CFLVAD to maintain physiologic perfusion while avoiding ventricular suction using only the intrinsic pump measurement of pump speed and without utilizing model-based estimation. Methods: The controller objective is to maintain a differential pump speed setpoint. A mathematical model of the circulatory system coupled with a model of a CFLVAD was used to test the control algorithm in silico . Robustness and efficacy were evaluated by comparing the proposed control algorithm to constant speed control, differential pump pressure control, mean aortic pressure control, and ventricular end diastolic pressure control during (1) rest and exercise conditions, (2) a rapid eight-fold increase in pulmonary vascular resistance under rest and exercise, (3) transitions from rest to exercise, and exercise to rest, (4) safe mode during left ventricular asystole, and (5) RPM measurement noise of 1% to 10% for (1) to (4). Results and conclusion: The control algorithm provided adequate perfusion while preventing ventricular suction for all test conditions. Performance did not deteriorate significantly with pump speed measurement noise of up to 6%. The safe mode successfully detected asystole and maintained adequate perfusion to sustain life even when the differential pump speed was low. Significance: Maintaining a constant differential pump speed can simultaneously achieve physiologic perfusion and suction prevention without needing unreliable, direct measurements of flow or pressure, or complex parameter or model-based estimation techniques.

Bone remodeling is a process in which bone is resorbed by osteoclasts and formed by osteoblasts. This is normally a paired process, although it can be disrupted by changes in mechanical load. One theory is that osteocytes play a key role in the cellular regulation of this process. Mechanotransduction studies, which investigate how cells convert mechanical stimuli into biophysical effects and cellular activity, offer one way to investigate this theory. Mechanotransduction work is commonly done by applying an isolated mechanical load to cells grown in vitro, and quantifying the response. While in vitro work does not fully replicate the natural environment, it does allow the study of isolated factors. In this study, a mechanical loading platform was designed, fabricated, and characterized for bone mechanotransduction studies. This platform was designed to tent cell-seeded substrates from below, loading using out of plane distension. This introduced a nonuniform strain profile, enabling the study of cells cultured under identical conditions and variable strains as a function of substrate location. An alphanumerically gridded polydimethylsiloxane well substrate was designed and fabricated for cellular loading experiments. Following initial characterization, a study was run to quantify the cellular activity of osteocyte-like MLO-Y4 cells as a function of strain field. The results indicated that regions with lower strains led to an increase in cellular activity while higher strains led to a reduction in cellular activity. This demonstrated that cells could be exposed to mechanically-induced microdamage using the microloading platform.

Induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) provide a human source of cardiomyocytes for use in cardiovascular research and regenerative medicine. However, attempts to use these cells in vivo have resulted in drastic cell death caused by mechanical, metabolic, and/or exogenous factors. To explore this issue, we designed a Biomimetic Cardiac Tissue Model (BCTM) where various parameters associated with heart function including heart rate, peak-systolic pressure, end-diastolic pressure and volume, end-systolic pressure and volume, and ratio of systole to diastole can all be precisely manipulated to apply hemodynamic loading to culture cells. Using the BCTM, two causes of low survivability in current cardiac stem cell therapies, mechanical and metabolic, were explored. iPSC-CMs were subject to physiologically relevant mechanical loading (50 mmHg systolic, 10% biaxial stretch) in either a low- or high-serum environment and mechanical loads were applied either immediately or gradually. Results confirm that iPSC-CMs subject to mechanical loading in low-serum conditions experienced widespread cell death. The rate of application of stress also played an important role in adaptability to mechanical loading. Under high-serum conditions, iPSC-CMs subject to gradual imposition of stress were comparable to iPSC-CMs maintained in static culture when evaluated in terms of cell viability, sarcomeric structure, action potentials and conduction velocities. In contrast, iPSC-CMs that were immediately exposed to mechanical loading had significantly lower cell viability, destruction of sarcomeres, smaller action potentials, and lower conduction velocities. We report that iPSC-CMs survival under physiologically relevant hemodynamic stress requires gradual imposition of mechanical loads in a nutrient-rich environment.

Increasing evidence indicates that mitochondrial-associated redox signaling contributes to the pathophysiology of heart failure (HF). The mitochondrial-targeted antioxidant, mitoquinone (MitoQ), is capable of modifying mitochondrial signaling and has shown beneficial effects on HF-dependent mitochondrial dysfunction. However, the potential therapeutic impact of MitoQ-based mitochondrial therapies for HF in response to pressure overload is reliant upon demonstration of improved cardiac contractile function and suppression of deleterious cardiac remodeling. Using a new (patho)physiologically relevant model of pressure overload-induced HF we tested the hypothesis that MitoQ is capable of ameliorating cardiac contractile dysfunction and suppressing fibrosis. To test this C57BL/6J mice were subjected to left ventricular (LV) pressure overload by ascending aortic constriction (AAC) followed by MitoQ treatment (2 µmol) for 7 consecutive days. Doppler echocardiography showed that AAC caused severe LV dysfunction and hypertrophic remodeling. MitoQ attenuated pressure overload-induced apoptosis, hypertrophic remodeling, fibrosis and LV dysfunction. Profibrogenic transforming growth factor-β1 (TGF-β1) and NADPH oxidase 4 (NOX4, a major modulator of fibrosis related redox signaling) expression increased markedly after AAC. MitoQ blunted TGF-β1 and NOX4 upregulation and the downstream ACC-dependent fibrotic gene expressions. In addition, MitoQ prevented Nrf2 downregulation and activation of TGF-β1-mediated profibrogenic signaling in cardiac fibroblasts (CF). Finally, MitoQ ameliorated the dysregulation of cardiac remodeling-associated long noncoding RNAs (lncRNAs) in AAC myocardium, phenylephrine-treated cardiomyocytes, and TGF-β1-treated CF. The present study demonstrates for the first time that MitoQ improves cardiac hypertrophic remodeling, fibrosis, LV dysfunction and dysregulation of lncRNAs in pressure overload hearts, by inhibiting the interplay between TGF-β1 and mitochondrial associated redox signaling., Graphical abstract fx1

Renal failure is significant adverse event of combat injury that increases mortality rate present in over 50% of wound related deaths. Renal replacement therapy (RRT) greatly reduces the mortality rate (> 90%). The current hemodialysis systems provide reasonable control over serum potassium levels but also require the use of large volumes of dialysate solution in a membrane contactor to replicate the function of the kidney. Hence, these devices are poorly suited for prolonged field care as they require specially trained personnel, bulky equipment that weighs ~70 lbs, and use large volumes of sterile dialysate solution. TDA research developed a compact, single-person portable, ruggedized, battery-operated, advanced filtration system for serum potassium (a bridge dialysis system) that can be used in the post traumatic care of combat casualties suffering from hyperkalemia; providing prolonged care before a patient arrives at a facility where appropriate RRT can be provided. TDA‘s bridge dialysis system uses an advanced sorbent that will remove only potassium (K+) ions from blood via highly adsorption process. This allows minimization (regeneration and re-use) or even elimination of the use of dialysate solution. UAB in collaboration with TDA has been actively involved with testing the efficiency, efficacy, and potential biotoxicity of TDA sorbents. In this paper, we detail extensive characterization of the various formulations of the TDA sorbent to estimate, potassium removal rate, selectivity for potassium over other metabolites and ions and preliminary biotoxicity evaluation of the sorbent using cell culture models. Our results demonstrate that the sorbent is indeed capable of efficient removal of potassium, is highly selective for potassium and is non-toxic to microvascular endothelial cells as evaluated using both direct contact and with medium conditioned with the sorbent. While more rigorous characterization and evaluation needs to be performed, preliminary studies confirm that Z-4 formulation TDA sorbent has great potential for RRT following combat injuries.