Moving forward on the pathway of cell-based therapies in ischemic heart disease and heart failure-time for new recommendations?

Although substantial advances have been made in treating ischemic heart disease and subsequent heart failure, the overall morbidity and mortality from these conditions remain high. Stem cell-based therapy has emerged as a promising approach for prompting cardiac rejuvenation. Various cell types have been tested in the clinical arena, proving consistent safety results. As for efficiency outcomes,contradictory findings have been reported, partly due to inconsistency in study protocols but also due to poor survival, engraftment and differentiation of transplanted cells in the hostile milieu of the ischemic host tissue. Studies have varied in terms of route of delivery, type and dose of implanted stem cells,patient selection and randomization, and assessment of therapeutic effect.Founded on the main achievements and challenges within almost 20 years of research, a number of official documents have been published by leading experts in the field. Core recommendations have focused on developing and optimizing effective strategies to enrich cell retention and their regenerative potential. Issued consensus and position papers have stemmed from an unmet need to provide a harmonized framework for future research, resulting in improved therapeutic application of cell-based therapies for cardiac regeneration and repair.     

A high-throughput screen for the engineered production of β-lactam antibiotics

High-throughput screens and selections have had profound impact on our ability to engineer proteins possessing new, desired properties. These methods are especially useful when applied to the modification of existing enzymes to create natural and unnatural products. In an advance upon existing methods we developed a high-throughput, genetically regulated screen for the in vivo production of β-lactam antibiotics using a green fluorescent protein (gfp) reporter. This assay proved reliable and sensitive and presents a dynamic range under which a wide array of β-lactam architectural subclasses can be detected. Moreover, the graded response elicited in this assay can be used to rank mutant activity. The utility of this development was demonstrated in vivo and then applied to the first experimental investigation of a putative catalytic residue in carbapenem synthase (CarC). Information gained about the mutability of this residue defines one parameter for enzymatic activity and sets boundaries for future mechanistic and engineering efforts.     

Histone deacetylase is required for the activation of Wnt/β-catenin signaling crucial for heart valve formation in zebrafish embryos

During vertebrate heart valve formation, Wnt/β-catenin signaling induces BMP signals in atrioventricular canal (AVC) myocardial cells and underlying AVC endocardial cells then undergo endothelial-mesenchymal transdifferentiation (EMT) by receiving this BMP signals. Histone deacetylases (HDACs) have been implicated in numerous developmental processes by regulating gene expression. However, their specific roles in controlling heart valve development are largely unexplored. To investigate the role of HDACs in vertebrate heart valve formation, we treated zebrafish embryos with trichostatin A (TSA), an inhibitor of class I and II HDACs, from 36 to 48 h post-fertilization (hpf) during which heart looping and valve formation occur. Following TSA treatment, abnormal linear heart tube development was observed. In these embryos, expression of AVC myocardial bmp4 and AVC endocardial notch1b genes was markedly reduced with subsequent failure of EMT in the AVC endocardial cells. However, LiCl-mediated activation of Wnt/β-catenin signaling was able to rescue defective heart tube formation, bmp4 and notch1b expression, and EMT in the AVC region. Taken together, our results demonstrated that HDAC activity plays a pivotal role in vertebrate heart tube formation by activating Wnt/β-catenin signaling which induces bmp4 expression in AVC myocardial cells.     

Hydrodynamic in vitro comparison of a new artificial heart valve with the Bj?rk-Shiley valve (standard)

Measurements performed to compare a newly developed tilting disc valve with the Bj?rk-Shiley valve included velocity profiles downstream of the heart valves, valve-induced flow turbulence and pressure drop across the opened valves. The velocity profiles measured with pulsed Doppler ultrasound are similar, although they do not permit a quantitative comparison of the valves. The interpretation of the 90 degrees-component of Doppler signals as a measure of the turbulence permits a quantitative comparison without the need for extensive measurements. However, only large vortices are recorded, so that our turbulent shear stresses are lower than these reported in the literature. The pressure drop across the opened valve is a measure of the energy loss, and important parameters for the valve can be derived from it. The pressure drop is dependent on the test conditions, and is therefore not a characteristic constant of the valve. The transformation of the power law Q = C delta P beta into a relation between Re- and Eu-number gives a nondimensional similarity number that is characteristic for tilting disc valves. Its verification requires more investigations, involving variation of valve size and the viscosity of the test fluid.     

“The state of the heart”: Recent advances in engineering human cardiac tissue from pluripotent stem cells

The pressing need for effective cell therapy for the heart has led to the investigation of suitable cell sources for tissue replacement. In recent years, human pluripotent stem cell research expanded tremendously, in particular since the derivation of human-induced pluripotent stem cells. In parallel, bioengineering technologies have led to novel approaches for in vitro cell culture. The combination of these two fields holds potential for in vitro generation of high-fidelity heart tissue, both for basic research and for therapeutic applications. However, this new multidisciplinary science is still at an early stage. Many questions need to be answered and improvements need to be made before clinical applications become a reality. Here we discuss the current status of human stem cell differentiation into cardiomyocytes and the combined use of bioengineering approaches for cardiac tissue formation and maturation in developmental studies, disease modeling, drug testing, and regenerative medicine.     

The effects of theβ2-agonist drug clenbuterol on taurine levels in heart and other tissues in the rat

Summary The administration of a single subcutaneous dose of clenbuterol to rats altered the level of taurine in certain tissues. Taurine levels in cardiac tissue were significantly decreased 3 h after the administration of 250g/kg of clenbuterol and remained significantly depressed at 12h post-dose only returning to control values by 24h. The level of taurine in the liver increased 3 h after clenbuterol administration but was lower than the control value at 24 h post dose. Lung taurine levels were significantly lower than the control value at 12 hr post dose and remained depressed until 24h post dose. Clenbuterol caused a significant increase in taurine levels in serum and muscle at 3 and 6 hr postdosing respectively but not at other time points. Serum creatine kinase (CK), activity was slightly but significantly raised at the 12 and 24 h time point.The effects of clenbuterol on tissue taurine content were not dose-dependent over the range studied (63–500g/kg). However taurine levels in the lung were significantly reduced at all doses and in the heart were significantly lower in the treated groups at all except the lowest dose, 12h post dosing. Liver taurine levels were significantly increased at the highest dose of 500g/kg.The reduction of taurine concentrations in the heart, caused by clenbuterol, is of concern as taurine has been shown to have protective properties in many tissues especially the heart.     

Allogenic heart valve bank in the Department of Cardiovascular Surgery and Transplantology of Jagiellonian University in Cracow – 23 years experience in the treatment of aortic valve or aortic root diseases.

Allogenic aortic valves are widely used in case of native aortic valve or root disease as well as failed prosthetic valves with great success. At the Department of Cardiovascular Surgery and Transplantology of the Jagiellonian University in Cracow, aortic valve or aortic root replacement with allogenic aortic valve has been performed for 23 years. Allogenic heart valve bank was founded in 1980. In the bank we prepare both aortic allografts for adult cardiac surgical procedures and pulmonary allografts that are mostly used for repair of congenital heart disease.Allogenic aortic valves implantation was usually considered in our clinic for older patients, patients with infective endocarditis of the native or prosthetic valve, young women in reproductive age and patients with Marfan syndrome. Allografts exhibit excellent clinical performance and acceptable durability with no early failure if properly inserted. Between 1980 and 1992, allografts were obtained only from cadavers during routine autopsies. More than 10% of prepared allografts were exported to other cardiac surgery centres in Poland and foreign countries.Aortic valve replacement using allogenic aortic valves can be performed with acceptable mortality and good long-term results. The procedure although surgically more challenging has the advantage of not requiring anticoagulation therapy, hemodynamic performance of the allogenic valve is excellent, it demonstrates freedom from thromboembolism and infective endocarditis. We would like to emphasize the importance and advantages of the fact that allogenic heart valve bank is placed in the department of cardiovascular surgery and it is able to supply the department in heart valve allografts 24 h a day.     

A quantitative cytochemical method for the measurement of β-hydroxyacyl CoA dehydrogenase activity in rat heart muscle

Summary Although cytochemical methods exist for measuring dehydrogenases that act on substrates involved in the production of chemical energy from sugars, virtually no methods exist for measuring the dehydrogenases that act on fatty acids. Yet the oxidation of fatty acids accounts for over 60% of the oxidative activity of cardiac muscle. Consequently a new quantitative cytochemical method, based on a new substrate (DL-S--hydroxybutyryl-N-acetyl cysteamine), has been developed for measuring the activity of hydroxy-acyl coenzyme A dehydrogenase, which is the penultimate step of the -oxidation of fatty acids to acetyl-coenzyme A that is used in the Krebs' cycle. Menadione or phenazine methosulphate is used as the intermediate hydrogen-acceptor, with neotetrazolium chloride as the final acceptor. The medium contains nitroprusside, ostensibly to react with any cysteamine liberated by hydrolysis of the substrate. As a control, cysteamine is substituted for the substrate. The concentrations of reactants have been optimized for cardiac muscle; the reaction is linear with thickness of the sections and with time of reaction from 15 to 60 min.     

Evidence for the presence of 3′, 5′-cyclic AMP in plant tissues

3′, 5′-cyclic AMP has been highly purified by chromatography from sterile higher plant tissues and assayed by bioluminescence as well as by activation of protein kinase. Both methods give comparable results: the amount of cyclic AMP was found to vary between 30 and 200 pmoles per mg of protein nitrogen.     

Pollen as a vehicle for the escape of engineered genes?

Recent studies of pollen exchange between neighboring populations of plants have shown that interpopulation gene flow can proceed over much greater distances and at higher rates than hitherto believed. This means that the escape of engineered genes from crop plants to their wild relatives is not only possible, but also likely. The development of containment strategies, such as extra modifications for increased self-fertilization and decreased pollen longevity in engineered crop plants, will be necessary to safeguard against such escape.     

On the in vivo function of the mitral heart valve leaflet: insights into tissue–interstitial cell biomechanical coupling

There continues to be a critical need for developing data-informed computational modeling techniques that enable systematic evaluations of mitral valve (MV) function. This is important for a better understanding of MV organ-level biomechanical performance, in vivo functional tissue stresses, and the biosynthetic responses of MV interstitial cells (MVICs) in the normal, pathophysiological, and surgically repaired states. In the present study, we utilized extant ovine MV population-averaged 3D fiducial marker data to quantify the MV anterior leaflet (MVAL) deformations in various kinematic states. This approach allowed us to make the critical connection between the in vivo functional and the in vitro experimental configurations. Moreover, we incorporated the in vivo MVAL deformations and pre-strains into an enhanced inverse finite element modeling framework (Path 1) to estimate the resulting in vivo tissue prestresses \((\sigma _\mathrm{CC}\cong \sigma _\mathrm{RR}\cong \, 30\,\hbox {kPa})\) and the in vivo peak functional tissue stresses \((\sigma _\mathrm{CC}\cong 510\, \hbox {kPa}, \sigma _\mathrm{RR}\cong 740\, \hbox {kPa})\). These in vivo stress estimates were then cross-verified with the results obtained from an alternative forward modeling method (Path 2), by taking account of the changes in the in vitro and in vivo reference configurations. Moreover, by integrating the tissue-level kinematic results into a downscale MVIC microenvironment FE model, we were able to estimate, for the first time, the in vivo layer-specific MVIC deformations and deformation rates of the normal and surgically repaired MVALs. From these simulations, we determined that the placement of annuloplasty ring greatly reduces the peak MVIC deformation levels in a layer-specific manner. This suggests that the associated reductions in MVIC deformation may down-regulate MV extracellular matrix maintenance, ultimately leading to reduction in tissue mechanical integrity. These simulations provide valuable insight into MV cellular mechanobiology in response to organ- and tissue-level alternations induced by MV disease or surgical repair. They will also assist in the future development of computer simulation tools for guiding MV surgery procedure with enhanced durability and improved long-term surgical outcomes.     

A finite viscoelastic–plastic model for describing the uniaxial ratchetting of soft biological tissues

In this paper, a phenomenological constitutive model is constructed to describe the uniaxial ratchetting (i.e., the cyclic accumulation of inelastic deformation) of soft biological tissues in the framework of finite viscoelastic-plasticity. The model is derived from a polyconvex elastic free energy function and addresses the anisotropy of cyclic deformation of the tissues by means of structural tensors. Ratchetting is considered by the evolution of internal variables, and its time-dependence is described by introducing a pseudo-potential function. Accordingly, all the evolution equations are formulated from the dissipation inequality. In numerical examples, the uniaxial monotonic stress–strain responses and ratchetting of some soft biological tissues, such as porcine skin, coronary artery layers and human knee ligaments and tendons, are predicted by the proposed model in the range of finite deformation. It is seen that the predicted monotonic stress–strain responses and uniaxial ratchetting obtained at various loading rates and in various loading directions are in good agreement with the corresponding experimental results.     

Vibrational sensitivity of the wing of the pigeon (Columba livia) — a study using heart rate conditioning

Summary The vibrational sensitivity of awake pigeons was tested with the heart rate conditioning method. This method proved to be a very sensitive instrument for the behavioural measurement of the pigeon's sensitivity to mechanical stimuli.Sine wave vibrational stimuli between 50 and 2000 Hz were applied to the 1st, 7th and 16th primary feathers of the wing. The resulting threshold curves were U- or V-shaped with 3 characteristics: (i) The frequency of best response was either 800 or 900 Hz. (ii) Within the broad frequency range of vibrational sensitivity (50 to 2000 Hz) the sensitivity was extremely high at the best frequency: threshold amplitudes lay between 0.5 and 0.09 m. (iii) The threshold curves showed very sharp tuning at best frequency with bandwidths between 0.3 and 0.7 octaves (measured at best frequency 10fold above threshold). The functional meaning of the characteristic vibrational sensitivity of the wing for flight control is discussed; it is interpreted as an adaptation to special situations occurring during flight.Abbreviations CR conditioned response - CS conditioned stimulus - ECG electrocardiogram - HC(s) Herbst corpuscle(s) - UCS unconditioned stimulus All experiments were carried out at the Ruhr-Universität Bochum, Lehrstuhl für Allgemeine Zoologie