Engineered heart tissue: Design considerations and the state of the art.

Originally developed more than 20 years ago, engineered heart tissue (EHT) has become an important tool in cardiovascular research for applications such as disease modeling and drug screening. Innovations in biomaterials, stem cell biology, and bioengineering, among other fields, have enabled EHT technologies to recapitulate many aspects of cardiac physiology and pathophysiology. While initial EHT designs were inspired by the isolated-trabecula culture system, current designs encompass a variety of formats, each of which have unique strengths and limitations. In this review, we describe the most common EHT formats, and then systematically evaluate each aspect of their design, emphasizing the rational selection of components for each application.

Clinical Interpretation of Serum Troponin in the Era of High-Sensitivity Testing.

Cardiac troponin (Tn) plays a central role in the evaluation of patients with angina presenting with acute coronary syndrome. The advent of high-sensitivity assays has improved the analytic sensitivity and precision of serum Tn measurement, but this advancement has come at the cost of poorer specificity. The role of clinical judgment is of heightened importance because, more so than ever, the interpretation of serum Tn elevation hinges on the careful integration of findings from electrocardiographic, echocardiographic, physical exam, interview, and other imaging and laboratory data to formulate a weighted differential diagnosis. A thorough understanding of the epidemiology, mechanisms, and prognostic implications of Tn elevations in each cardiac and non-cardiac etiology allows the clinician to better distinguish between presentations of myocardial ischemia and myocardial injury-an important discernment to make, as the treatment of acute coronary syndrome is vastly different from the workup and management of myocardial injury and should be directed at the underlying cause.

Clinical Biochemistry of Serum Troponin.

Accurate measurement and interpretation of serum levels of troponin (Tn) is a central part of the clinical workup of a patient presenting with chest pain suspicious for acute coronary syndrome (ACS). Knowledge of the molecular characteristics of the troponin complex and test characteristics of troponin measurement assays allows for a deeper understanding of causes of false positive and false negative test results in myocardial injury. In this review, we discuss the molecular structure and functions of the constituent proteins of the troponin complex (TnT, TnC, and TnI); review the different isoforms of Tn and where they are from; survey the evolution of clinical Tn assays, ranging from first-generation to high-sensitivity (hs); provide a primer on statistical interpretation of assay results based on different clinical settings; and discuss potential causes of false results. We also summarize the advances in technologies that may lead to the development of future Tn assays, including the development of point of care assays and wearable Tn sensors for real-time continuous measurement.

Chronic diastolic stretch unmasks conduction defects in an in vitro model of arrhythmogenic cardiomyopathy.

We seek to elucidate the precise nature of mechanical loading that precipitates conduction deficits in a concealed-phase model of arrhythmogenic cardiomyopathy (ACM). ACM is a progressive disorder often resulting from mutations in desmosomal proteins. Exercise has been shown to worsen disease progression and unmask arrhythmia vulnerability, yet the underlying pathomechanisms may depend on the type and intensity of exercise. Because exercise causes myriad changes to multiple inter-dependent hemodynamic parameters, it is difficult to isolate its effects to specific changes in mechanical load. Here, we use engineered heart tissues (EHTs) with iPSC-derived cardiomyocytes expressing R451G desmoplakin, an ACM-linked mutation, which results in a functionally null model of desmoplakin (DSP). We also use a novel bioreactor to independently perturb tissue strain at different time points during the cardiac cycle. We culture EHTs under three strain regimes: normal physiological shortening; increased diastolic stretch, simulating high preload; and isometric culture, simulating high afterload. DSPR451G EHTs that have been cultured isometrically undergo adaptation, with no change in action potential parameters, conduction velocity, or contractile function, a phenotype confirmed by global proteomic analysis. However, when DSPR451G EHTs are subjected to increased diastolic stretch, they exhibit concomitant reductions in conduction velocity and the expression of connexin-43. These effects are rescued by inhibition of both lysosome activity and ERK signaling. Our results indicate that the response of DSPR451G EHTs to mechanical stimuli depends on the strain and the timing of the applied stimulus, with increased diastolic stretch unmasking conduction deficits in a concealed-phase model of ACM.

ß-Arrestin-Biased Allosteric Modulator Potentiates Carvedilol-Stimulated ß Adrenergic Receptor Cardioprotection.

ß 1 adrenergic receptors (ß 1ARs) are central regulators of cardiac function and a drug target for cardiac disease. As a member of the G protein-coupled receptor family, ß 1ARs activate cellular signaling by primarily coupling to Gs proteins to activate adenylyl cyclase, cAMP-dependent pathways, and the multifunctional adaptor-transducer protein ß-arrestin. Carvedilol, a traditional ß-blocker widely used in treating high blood pressure and heart failure by blocking ß adrenergic receptor-mediated G protein activation, can selectively stimulate Gs-independent ß-arrestin signaling of ß adrenergic receptors, a process known as ß-arrestin-biased agonism. Recently, a DNA-encoded small-molecule library screen against agonist-occupied ß 2 adrenergic receptors (ß 2ARs) identified Compound-6 (Cmpd-6) to be a positive allosteric modulator for agonists on ß 2ARs. Intriguingly, it was further discovered that Cmpd-6 is positively cooperative with the ß-arrestin-biased ligand carvedilol at ß 2ARs. Here we describe the surprising finding that at ß 1ARs unlike ß 2ARs, Cmpd-6 is cooperative only with carvedilol and not agonists. Cmpd-6 increases the binding affinity of carvedilol for ß 1ARs and potentiates carvedilol-stimulated, ß-arrestin-dependent ß 1AR signaling, such as epidermal growth factor receptor transactivation and extracellular signal-regulated kinase activation, whereas it does not have an effect on Gs-mediated cAMP generation. In vivo, Cmpd-6 enhances the antiapoptotic, cardioprotective effect of carvedilol in response to myocardial ischemia/reperfusion injury. This antiapoptotic role of carvedilol is dependent on ß-arrestins since it is lost in mice with myocyte-specific deletion of ß-arrestins. Our findings demonstrate that Cmpd-6 is a selective ß-arrestin-biased allosteric modulator of ß 1ARs and highlight its potential clinical utility in enhancing carvedilol-mediated cardioprotection against ischemic injury. SIGNIFICANCE STATEMENT: This study demonstrates the positive cooperativity of Cmpd-6 on ß1ARs as a ß-arrestin-biased positive allosteric modulator. Cmpd-6 selectively enhances the affinity and cellular signaling of carvedilol, a known ß-arrestin-biased ß-blocker for ß1ARs, whereas it has minimal effect on other ligands tested. Importantly, Cmpd-6 enhances the ß-arrestin-dependent in vivo cardioprotective effect of carvedilol during ischemia/reperfusion injury-induced apoptosis. The data support the potential therapeutic application of Cmpd-6 to enhance the clinical benefits of carvedilol in the treatment of cardiac disease.

Over half of contemporary clinical Gleason 8 on prostate biopsy are downgraded at radical prostatectomy.

INTRODUCTION: Contemporary clinical guidelines utilize the highest Gleason sum (HGS) in any one core on prostate biopsy to determine prostate cancer treatment. Here, we present a large discrepancy between prostate cancer risk stratified as high risk on biopsy and their pathology after radical prostatectomy. MATERIALS AND METHODS: We retrospectively reviewed 1424 men who underwent either open or robotic-assisted prostatectomy between 2004 and 2015. We analyzed 148 men who were diagnosed with HGS 8 on prostate biopsy. Biopsy and prostatectomy pathology were compared in aggregate and over 1 year time intervals. Chi-squared test, Fisher's exact test, Student's t-test, and Wilcoxon Rank-Sum test were used for statistical analysis. RESULTS: A total of 61.5% (91/148) of clinical HGS 8 diagnoses were downgraded on prostatectomy, with 58.8% (87/148) downgraded to Gleason 7 (Gleason 4 + 3 n = 59; Gleason 3 + 4 n = 28). Factors associated with downgrading include lower prostate-specific antigen (PSA) at biopsy (median 6.8 ng/mL versus 9.1 ng/mL, p < 0.001), number of Gleason 8 biopsy cores (median 1 versus 2, p < 0.02), presence of Gleason pattern 3 on biopsy cores (67.9% versus 44.8%, p < 0.03), pT2 staging (72.4% versus 55.1%, p < 0.04), positive margins (53.9% versus 69.1%, p < 0.04), extracapsular extension (53.4% versus 74.1%, p < 0.02), and smaller percent tumor (median 10% versus 15%, p < 0.004). CONCLUSION: The large percentage of pathology downgrading of biopsy-diagnosed HGS 8 suggests suboptimal risk-stratification that may lead to suboptimal treatment strategies and much patient distress. Our study adds great urgency to the efforts refining prostate cancer clinical assessment.

The Role of Extra-Anatomic Bypass in the Surgical Treatment of Acute Abdominal Aortic Occlusion

BACKGROUND: Aortic occlusion is rare catastophic pathology with high rates of mortality and severe morbidity. In this study, we aimed to share our experience in the management of aortic occlusion and to assess the outcomes of extra-anatomic bypass procedures. METHODS: Eighteen patients who had undergone extra-anatomic bypass interventions in the cardiovascular surgery department of our tertiary care center between July 2009 and May 2013 were retrospectively evaluated. All patients were preoperatively assessed with angiograms (conventional, computed tomography, or magnetic resonance angiography) and Doppler ultrasonography. Operations consisted of bilateral femoral thromboembolectomy, axillobifemoral extra-anatomic bypass and femoropopliteal bypass and were performed on an emergency basis. RESULTS: In all patients during early postoperative period successful revascularization outcomes were obtained; however, one of these operated patients died on the 10th postoperative due to multiorgan failure. The patients were followed up for a mean duration of 21.2+/-9.4 months (range, 6 to 36 months). Amputation was not warranted for any patient during postoperative follow-up. CONCLUSION: To conclude, acute aortic occlusion is a rare but devastating event and is linked with substantial morbidity and mortality in spite of the recent advances in critical care and vascular surgery. Our results have shown that these hazardous outcomes may be minimized and better rates of graft patency may be achieved with extra-anatomic bypass techniques tailored according to the patient.