The Sydney Heart Bank: improving translational research while eliminating or reducing the use of animal models of human heart disease

The Sydney Heart Bank (SHB) is one of the largest human heart tissue banks in existence. Its mission is to provide high-quality human heart tissue for research into the molecular basis of human heart failure by working collaboratively with experts in this field. We argue that, by comparing tissues from failing human hearts with age-matched non-failing healthy donor hearts, the results will be more relevant than research using animal models, particularly if their physiology is very different from humans. Tissue from heart surgery must generally be used soon after collection or it significantly deteriorates. Freezing is an option but it raises concerns that freezing causes substantial damage at the cellular and molecular level. The SHB contains failing samples from heart transplant patients and others who provided informed consent for the use of their tissue for research. All samples are cryopreserved in liquid nitrogen within 40 min of their removal from the patient, and in less than 5-10 min in the case of coronary arteries and left ventricle samples. To date, the SHB has collected tissue from about 450 failing hearts (>15,000 samples) from patients with a wide range of etiologies as well as increasing numbers of cardiomyectomy samples from patients with hypertrophic cardiomyopathy. The Bank also has hearts from over 120 healthy organ donors whose hearts, for a variety of reasons (mainly tissue-type incompatibility with waiting heart transplant recipients), could not be used for transplantation. Donor hearts were collected by the St Vincent's Hospital Heart and Lung transplantation team from local hospitals or within a 4-h jet flight from Sydney. They were flushed with chilled cardioplegic solution and transported to Sydney where they were quickly cryopreserved in small samples. Failing and/or donor samples have been used by more than 60 research teams around the world, and have resulted in more than 100 research papers. The tissues most commonly requested are from donor left ventricles, but right ventricles, atria, interventricular system, and coronary arteries vessels have also been reported. All tissues are stored for long-term use in liquid N or vapor (170-180 °C), and are shipped under nitrogen vapor to avoid degradation of sensitive molecules such as RNAs and giant proteins. We present evidence that the availability of these human heart samples has contributed to a reduction in the use of animal models of human heart failure.

Quantification of thyroxine and 3,5,3'-triiodo-thyronine in human and animal hearts by a novel liquid chromatography-tandem mass spectrometry method

Assaying tissue T3 and T4 would provide important information in experimental and clinical investigations. A novel method to determine tissue T3 and T4 by HPLC coupled to mass spectrometry is described. The major difference vs. previously described methods lies in the addition of a derivatization step, that is, to convert T3 and T4 into the corresponding butyl esters. The yield of esterification was ̴ 100% for T3 and 80% for T4. The assay was linear (r>0.99) in the range of 0.2-50 ng/ml, accuracy was in the order of 70-75%, and the minimum tissue amount needed was in the order of 50 mg, that is, about one order of magnitude lower than observed with the same equipment (AB Sciex API 4000 triple quadrupole mass spectrometer) if derivatization was omitted. The method allowed detection of T3 and T4 in human left ventricle biopsies yielding concentrations of 1.51±0.16 and 5.94±0.63 pmol/g, respectively. In rats treated with different dosages of exogenous T3 or T4, good correlations (r>0.90) between plasma and myocardial T3 and T4 concentrations were observed, although in specific subsets different plasma T4 concentrations were not associated with different tissue content in T4. We conclude that this method could provide a novel insight into the relationship between plasma and tissue thyroid hormone levels.

Plasma immersion ion implantation treatment of polyethylene for enhanced binding of active horseradish peroxidase

Robust attachment of active proteins to synthetic surfaces underpins the development of biosensors and protein arrays. This paper presents the results of experiments in which energetic ions, extracted from an inductively coupled nitrogen plasma, are used to modify the surface of ultrahigh molecular weight polyethylene (UHMWPE). The ability of the surface to bind active horseradish peroxidase (HRP) is significantly enhanced by the plasma treatment. The amide signal in infrared spectroscopy indicates an increased quantity of surface-attached protein on the modified surface. The activity of the bound HRP remains high compared with that of protein attached to the untreated surface, after repeated washing in buffer solution. Although Tween 20 was an effective blocking agent for the unmodified polyethylene surface, binding of HRP to the modified surface is not inhibited by its presence. We propose that the treatment produces new binding sites on the surface and that the function of the HRP is retained because the treated surface is substantially more hydrophilic.

[Conformational changes of actin induced by strong or weak myosin subfragment-1 binding]

Movements of different areas of polypeptide chains within F-actin monomers induced by S1 or pPDM-S1 binding were studied by polarized fluorimetry. Thin filaments of ghost muscle were reconstructed by adding G-actin labeled with fluorescent probes attached alternatively to different sites of actin molecule. These sites were: Cys-374 labeled with 1,5-IAEDANS, TMRIA or 5-IAF; Lys-373 labeled with NBD-Cl; Lys-113 labeled with Alexa-488; Lys-61 labeled with FITC; Gln-41 labeled with DED and Cys-10 labeled with 1,5-IAEDANS, 5-IAF or fluorescein-maleimid. In addition, we used TRITC-, FITC-falloidin and e-ADP that were located, respectively, in filament groove and interdomain cleft. The data were analysed by model-dependent and model-independent methods (see appendixes). The orientation and mobility of fluorescent probes were significantly changed when actin and myosin interacted, depending on fluorophore location and binding site of actomyosin. Strong binding of S with actin leads to 1) a decrease in the orientation of oscillators of derivatives of falloidin (TRITC-falloidin, FITC-falloidin) and actin-bound nucleotide (e-ADP); 2) an increase in the orientation of dye oscillators located in the "front' surface of the small domain (where actin is viewed in the standard orientation with subdomains 1/2 and 3/4 oriented to the right and to the left, respectively); 3) a decrease in the angles of dye oscillators located on the "back" surface of subdomain-1. In contrast, a weak binding of S1 to actin induces the opposite effects in orientation of these probes. These data suggest that during the ATP hydrolysis cycle myosin heads induce a change in actin monomer (a tilt and twisting of its small domain). Presumably, these alterations in F-actin conformation play an important role in muscle contraction.

Genomics, proteomics and bioinformatics of human heart failure

Unraveling the molecular complexities of human heart failure, particularly end-stage failure, can be achieved by combining multiple investigative approaches. There are several parts to the problem. Each patient is the product of a complex set of genetic variations, different degrees of influence of diets and lifestyles, and usually heart transplantation patients are treated with multiple drugs. The genomic status of the myocardium of any one transplant patient can be analysed using gene arrays (cDNA- or oligonucleotide-based) each with its own strengths and weaknesses. The proteins expressed by these failing hearts (myocardial proteomics) were first investigated over a decade ago using two-dimensional polyacrylamide gel electrophoresis (2DGE) which promised to resolve several thousand proteins in a single sample of failing heart. However, while 2DGE is very successful for the abundant and moderately expressed proteins, it struggles to identify proteins expressed at low levels. Highly focused first dimension separations combined with recent advances in mass spectrometry now provide new hope for solving this difficulty. Protein arrays are a more recent form of proteomics that hold great promise but, like the above methods, they have their own drawbacks. Our approach to solving the problems inherent in the genomics and proteomics of heart failure is to provide experts in each analytical method with a sample from the same human failing heart. This requires a sufficiently large number of samples from a sufficiently large pool of heart transplant patients as well as a large pool of non-diseased, non-failing human hearts. We have collected more than 200 hearts from patients undergoing heart transplantations and a further 50 non-failing hearts. By combining our expertise we expect to reduce and possibly eliminate the inherent difficulties of each analytical approach. Finally, we recognise the need for bioinformatics to make sense of the large quantities of data that will flow from our laboratories. Thus, we plan to provide meaningful molecular descriptions of a number of different conditions that result in terminal heart failure.

Flavivirus induces MHC antigen on human myoblasts: a model of autoimmune myositis?

Infection of human embryonic myoblasts by West Nile virus (WNV), a flavivirus, caused significant upregulation of class I and II MHC expression as determined by flow cytometry. After 48 hours at a multiplicity of infection of 5 pfu/cell, a sixfold increase in MHC class I expression was induced from initially low levels of expression. In contrast, MHC class II was induced de novo to five times the control fluorescence level. At least 70% of the cells were infected as determined using fluorescence microscopy and anti-WNV antibody labeling. Myoblasts were > 90% pure as shown by anti--Leu-19 labeling. MHC class I (but not class II) was increased threefold after exposure to virus-inactivated supernatant from 48-hour--infected cells, indicating the presence of factor(s) contributing to the MHC class I increase. These findings may be important in establishing a link between viral infection of human cells and induction of inflammatory autoimmune disease. We discuss the possibility of using WNV as an in vivo model.

Localization of the phalloidin and nucleotide-binding sites on actin

Phalloidin was found to block nucleotide exchange in F-actin, without interfering with nucleotide hydrolysis. This inhibition of nucleotide exchange occurs under conditions in which monomers are able to exchange. The distance separating a fluorescent chromophore attached to phalloidin from the nucleotide on actin was determined using fluorescence resonance energy-transfer spectroscopy. They are separated by less than 1.0 nm. Added confirmation of the close proximity of phalloidin to nucleotide was obtained by extracting a small peptide-ATP complex from an actin digest. The peptide comprises residues 114-118, which are from the same region as the residues that others have shown to crosslink to phalloidin [Vandekerckhove et al. (1985) EMBO J. 4, 2815-2818]. The results suggest that phalloidin has two major effects. It traps actin monomers in a conformation which appears to be distinct from G-actin and it stabilizes the structure of F-actin, an event accompanied by the trapping of ADP.

Actin tube formation: effects of variations in commonly used solvent conditions

Crystalline tubular aggregates of actin spontaneously assemble in the presence of certain of the lanthanide ions. These tubes are now known to contain a high degree of structural order and it has been suggested that they may be sensitive to small changes in the primary sequence. However, there have been no detailed studies of the effects of solution conditions associated with their formation. In this report we systematically examine the effects of lanthanide ion concentration, ionic radius, adenosine nucleotide concentration, divalent cation concentration, pH, KCl concentration and incubation time. The stringent control of these parameters leads to a high degree of predictability of the structural parameters of the tubes and will thus be of use in identifying actin isozymes.

Fluorescence energy transfer between probes on actin and probes on myosin

The structural relationship between F-actin filaments and the biologically active fragments of myosin (either as myosin subfragment-1 or heavy meromyosin) has been investigated using the technique of fluorescence energy transfer. Donor and acceptor probes were used to obtain the following inter- and intramolecular distances. Energy transfer was measured: (1) from the SH1 groups of the myosin 'heads' to the nucleotide sites of F-actin (in the absence of free nucleotide); (2) from the SH1 groups of myosin to multiple probes on the surface of the actin filament; (3) from the nucleotide-binding sites of F-actin to the ATPase sites of myosin; (4) from the ATPase sites of myosin to the nucleotide-binding sites of F-actin; (5) from the SH1 sites of myosin to the nucleotide-binding sites of F-actin; and (6) from the Cys-373 residues of F-actin to the nucleotide binding sites of F-actin. We observed very little energy transfer between the probes on actin and the probes on myosin (10% or less) and we observed a large transfer between the actin Cys-373 and the actin nucleotide. These data strongly suggest that both the SH1 moiety and the ATPase site of myosin are located more than 6 nm from the actin sites. When these distances are combined with similar measurements by other authors and inserted into the most recent three-dimensional reconstruction of electron micrographs of the acto-subfragment-1 complex, it is apparent that the SH1 and the ATPase sites on myosin are not located adjacent to actin and are most probably located in the half of the myosin head that is distal from actin in the actomyosin complex.

Actin monomer conformation under polymerizing conditions studied by proton nuclear magnetic resonance and circular dichroism spectroscopy

Skeletal muscle actin above a critical concentration polymerizes in physiological concentrations of KCl. Earlier studies have concluded that evidence exists for a monomeric species of actin with a conformation distinct from that of G-actin. Re-investigations of these earlier studies, however, have cast doubt on the concept of a new monomeric actin species. In this study we have adopted two methods, high-resolution proton nuclear magnetic resonance and near ultraviolet circular dichroism spectroscopy, to investigate the existence or otherwise of the putative monomer conformation variously called F-monomer, G-actin or KCl-monomer. For proton nuclear magnetic resonance spectroscopy, unmodified actin maintained below its critical concentration as well as higher concentrations of two chemically modified, unpolymerizable actin samples were studied in the absence and presence of KCl. No difference was found in the environment of even a single proton within the entire actin structure. For circular dichroism we studied actin maintained below its critical polymerization concentration and found very little change in ellipticities when KCl was added to the G-actin solution. We therefore conclude that there is no species of actin monomer with a conformation distinct from that of G-actin.

A re-investigation of actin monomer conformation under polymerizing conditions based on rates of enzymatic digestion and ultraviolet difference spectroscopy

There have been several reports which describe a conformational change of G-actin monomer in the presence of 0.1 M KCl. This altered monomer has been variously named, depending on whether the authors believed that it resembles G-actin, F-actin or has a conformation of its own. In this report we re-examine the experimental evidence for these proposals. The techniques include measurements of the rates of proteolytic digestion as well as near and far ultraviolet difference spectroscopy of actin in the presence and absence of KCl. We conclude that there is no compelling evidence for proposing a novel form of actin monomer.

Crystalline actin tubes. III. The interaction of scandium and yttrium with skeletal muscle actin

The effect of the trivalent cations scandium (Sc3+) and yttrium (Y3+) on the conformation of G-actin was examined using ultraviolet difference and high resolution 1H-NMR spectroscopy. A comparison was made with data obtained previously with the trivalent lanthanide cations (Ln3+). These results indicate that the first and subsequent Y ions (ionic radius 101.9 pm) behave exactly like Ln3+. Sc3+ is a smaller ion (87 pm) than any of the Ln3+. The first Sc3+ binds to a site on actin that is inaccessible to Mg2+, Y3+ and Ln3+. However, the second Sc3+ to bind behaves like an Ln3+. On replacing the native divalent cation (Mg2+), both Y3+ and Sc3+ mobilize the adenine ring of ATP bound to actin, thus exposing underlying residues to the solvent. When Y3+ and Sc3+ saturate their binding sites on actin, and when the ionic strength is raised to 0.1 M with KCl at pH 6.9, the actin aggregates. Y3+ binds to actin with a ratio of 6 : 1 and induces the aggregation of actin into crystalline actin tubes, whilst Sc3+ binds with a ratio of 8 : 1 and induces amorphous actin aggregates. These results are consistent with the suggestion that actin tubes are induced by trivalent cations, principally on the basis of their binding stoichiometry, which is determined by ionic radius.

Evidence for the non-filamentous aggregation of actin induced by lanthanide ions

We varied the molar ratio of added lanthanide ion to skeletal muscle actin (M3+/A) and observed their effects on the change in reduced viscosity (Nred) in the presence of polymerizing quantities of salt (0.1 M KC1). Once the concentration of the lanthanide ion exceeds the concentration of the nucleotide present (0.2 mM ATP), we noted that with M3+/A ratios up to 4: (a) there was a sharp peak in the observed Nred above the level achieved by control F-actin; (b) the magnitude of (a) was shown to be a function of the initial G-actin concentration. With an M3+/A ratio of greater than 4 we observed: (i) a sharp fall in the observed Nred; (ii) the formation of an insoluble aggregate of actin; (iii) the formation of (ii) was completely reversed by removal of the M3+; (iv) a complete inhibition of the ATP hydrolysis which always accompanies the G- to F-actin transition; (v) the number of mol of M3+ required to completely inhibit the rise in Nred (above the viscosity of G-actin) was a function of the ionic radii of the 11 lanthanide ions tested; and (vi) the effects described in (i) were not mimicked when the initial protein was in the F form. In the absence of added KCI, divalent cations (e.g. Mg2+) polymerize G-actin but this effect is not mimicked by the addition of the lanthanide ions. However, under these conditions the lanthanide ions cause the formation of an insoluble aggregate of actin. We conclude that with greater than 4 mol of lanthanide ions, G-actin aggregates in a form which contains little or no F-actin and that the lanthanide ion-induced aggregates are therefore different from the Mg2+-induced F-actin paracrystals.

Individual states in the cycle of muscle contraction

By using appropriate analogs of ATP, isometrically-held glycerol-extracted psoas fibers from rabbits are forced successively into states corresponding to molecular species in the contractile cycle. In each state measurements are made of P[unk], a fluorescence polarization parameter thought to relate to attitude of S-1 moieties of the myosin molecules. Also, the value of P[unk] is measured during active tension development. It is suggested that this value is a time-average of the P[unk] as S-1 moieties move through the various states of the cycle. Proposals are made concerning the sequence of states in the cycle.

Polarization of tryptophan fluorescence from single striated muscle fibers. A molecular probe of contractile state

Instrumentation has been developed to detect rapidly the polarization of tryptophan fluorescence from single muscle fibers in rigor, relaxation, and contraction. The polarization parameter (P( perpendicular)) obtained by exiciting the muscle tryptophans with light polarized perpendicular to the long axis of the muscle fiber had a magnitude P( perpendicular) (relaxation) > P( perpendicular) (contraction) > P( perpendicular) (rigor) for the three types of muscle fibers examined (glycerinated rabbit psoas, glycerinated dorsal longitudinal flight muscle of Lethocerus americanus, and live semitendinosus of Rana pipiens). P( perpendicular) from single psoas fibers in rigor was found to increase as the sarcomere length increased but in relaxed fibers P( perpendicular) was independent of sarcomere length. After rigor, pyrophosphate produced little or no change in P( perpendicular), but following an adenosine triphosphate (ATP)-containing solution, pyrophosphate produced a value of P( perpendicular) that fell between the contraction and relaxation values. Sinusoidal or square wave oscillations of the muscle of amplitude 0.5-2.0% of the sarcomere length and frequency 1, 2, or 5 Hz were applied in rigor when the myosin cross-bridges are considered to be firmly attached to the thin filaments. No significant changes in P( perpendicular) were observed in either rigor or relaxation. The preceding results together with our present knowledge of tryptophan distribution in the contractile proteins has led us to the conclusion that the parameter P( perpendicular) is a probe of the contractile state of myosin which is probably sensitive to the orientation of the myosin S1 subfragment.