Regulation of excitation-contraction coupling in mouse cardiac myocytes: integrative analysis with mathematical modelling

<p>Abstract</p> <p>Background</p> <p>The cardiomyocyte is a prime example of inherently complex biological system with inter- and cross-connected feedback loops in signalling, forming the basic properties of intracellular homeostasis. Functional properties of cells and tissues have been studied e.g. with powerful tools of genetic engineering, combined with extensive experimentation. While this approach provides accurate information about the physiology at the endpoint, complementary methods, such as mathematical modelling, can provide more detailed information about the processes that have lead to the endpoint phenotype.</p> <p>Results</p> <p>In order to gain novel mechanistic information of the excitation-contraction coupling in normal myocytes and to analyze sophisticated genetically engineered heart models, we have built a mathematical model of a mouse ventricular myocyte. In addition to the fundamental components of membrane excitation, calcium signalling and contraction, our integrated model includes the calcium-calmodulin-dependent enzyme cascade and the regulation it imposes on the proteins involved in excitation-contraction coupling. With the model, we investigate the effects of three genetic modifications that interfere with calcium signalling: 1) ablation of phospholamban, 2) disruption of the regulation of L-type calcium channels by calcium-calmodulin-dependent kinase II (CaMK) and 3) overexpression of CaMK. We show that the key features of the experimental phenotypes involve physiological compensatory and autoregulatory mechanisms that bring the system to a state closer to the original wild-type phenotype in all transgenic models. A drastic phenotype was found when the genetic modification disrupts the regulatory signalling system itself, i.e. the CaMK overexpression model.</p> <p>Conclusion</p> <p>The novel features of the presented cardiomyocyte model enable accurate description of excitation-contraction coupling. The model is thus an applicable tool for further studies of both normal and defective cellular physiology. We propose that integrative modelling as in the present work is a valuable complement to experiments in understanding the causality within complex biological systems such as cardiac myocytes.</p

Development of Microbial Analysis – Faster Detection and Business Opportunities

FMA Fast Microbial Analysis project was funded by TEKES, decision numbers 40173/13, 40174/13 and 40175/13Foodborne diseases represent a serious public health issue. For example in the USA it is estimated that the total economic impact is $50 to$80 billion annually in health care costs, lost productivity, and diminished quality of life (Byrd-Bredbenner et al. 2013). For this reason, food safety authorities around the world have realized the need for a strict regulatory framework, including an exhaustive food testing regime. In the European Union (EU) the Comission regulation (EC) No 2073/2005 on microbiological criteria for foodstuffs has been established for food pathogens including Listeria monocytogenes. According to the regulation the manufactures and other food business operators are responsible for the production and delivery of safe food. The follow up will be carried out by self-monitoring methods. Conventional methods are often sensitive, but extremely time-consuming. Depending on the target microorganism, it may take from several days to over two weeks to obtain a fully confirmed positive test result (Velusamy et al. 2010). In present food business this timescale is too long. Because of that Fast Microbe Analysis (FMA) solution was developed in this project. The target of microbiological part of the study was to shorten the lag phase time in L. monocytogenes enrichment procedure and determine the selectivity of growth media combined with IMS. It was clearly seen that it is really difficult to make remarkable improvements in shortening the lag phase time. The selectivity of growth media combined with immunomagnetic separation concluded that, the developed method is applicable in Listeria spp. detection, but not specific for L. monocytogenes detection. By combining surface enhanced Raman spectroscopic (SERS) detection with the sample concentration the detection limit of 104 CFU/ml was obtained. SERS was based on the hybrid nanoparticle and corrugated substrate configuration, while immunomagnetic bead separation and hydrophobic surfaces were utilized to concentrate samples. Business research in FMA project included indetification of market opportunities for developed FMA solution, identification of the food safety business ecosystem and the related possible ecosystem business model for the developed solution. Business opportunities for FMA solution in other industries were also analyzed.201

Altered contractility in mutation-specific hypertrophic cardiomyopathy : A mechano-energetic in silico study with pharmacological insights

Introduction: Mavacamten (MAVA), Blebbistatin (BLEB), and Omecamtiv mecarbil (OM) are promising drugs directly targeting sarcomere dynamics, with demonstrated efficacy against hypertrophic cardiomyopathy (HCM) in (pre)clinical trials. However, the molecular mechanism affecting cardiac contractility regulation, and the diseased cell mechano-energetics are not fully understood yet.Methods: We present a new metabolite-sensitive computational model of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) electromechanics to investigate the pathology of R403Q HCM mutation and the effect of MAVA, BLEB, and OM on the cell mechano-energetics.Results: We offer a mechano-energetic HCM calibration of the model, capturing the prolonged contractile relaxation due to R403Q mutation (∼33%), without assuming any further modifications such as an additional Ca2+ flux to the thin filaments. The HCM model variant correctly predicts the negligible alteration in ATPase activity in R403Q HCM condition compared to normal hiPSC-CMs. The simulated inotropic effects of MAVA, OM, and BLEB, along with the ATPase activities in the control and HCM model variant agree with in vitro results from different labs. The proposed model recapitulates the tension-Ca2+ relationship and action potential duration change due to 1 µM OM and 5 µM BLEB, consistently with in vitro data. Finally, our model replicates the experimental dose-dependent effect of OM and BLEB on the normalized isometric tension.Conclusion: This work is a step toward deep-phenotyping the mutation-specific HCM pathophysiology, manifesting as altered interfilament kinetics. Accordingly, the modeling efforts lend original insights into the MAVA, BLEB, and OM contributions to a new interfilament balance resulting in a cardioprotective effect.publishedVersionPeer reviewe

Metsänvuokraus – uusi metsäomaisuuden hoidon kokonaispalvelu : METSÄVUO-hankkeen loppuraportti

Luonnonvarakeskuksen ja Itä-Suomen yliopiston yhteistyönä toteutetussa ”Metsätilojen vuokrauksesta uusi metsäomaisuuden hoidon kokonaispalvelu” -projektissa tutkittiin ja kehitettiin metsien vuokraukseen perustuvaa verkostoituneen liiketoiminnan mallia yksityismetsiin. Tavoitteena oli jäsentää ja arvioida metsänvuokrauspalvelun ominaisuuksia sekä selvittää edellytyksiä käynnistää vuokraukseen perustuvaa uutta metsäpalveluliiketoimintaa. Projektia toteutettaessa kotimaisen puun kysynnän odotettiin lisääntyvän merkittävästi suunniteltujen investointien toteutuessa. Metsänvuokraukseen perustuva omaisuudenhoitopalvelu voisi olla yksi keino vähentää yksityismetsien puustovarantojen mobilisaatioon liittyviä epävarmuustekijöitä. Metsäomaisuuden hoitopalveluna metsänvuokraus sijoittuu luonteeltaan hoitopalvelusopimuksen ja yhteismetsän välimaastoon. Metsänvuokrauksessa tavoitellaan kokonaisvaltaista metsäomaisuuden hoitoa, josta sovittaessa metsänomistaja luovuttaa yhdellä päätöksellä metsiensä hakkuiden ja hoidon toteuttamisen määräajaksi (esim. 10 vuodeksi) vuokralaisen hoidettavaksi metsänomistajalle maksettavaa (tavallisesti vuotuista) korvausta vastaan. Vuokralainen tekee toimenpiteet itse tai teettää ne kolmansilla osapuolilla noudattaen yhdessä metsänomistajan kanssa sovittuja periaatteita ja metsänhoitomenetelmiä. Vuokralainen vastaa töiden toteutuksesta, yksittäisistä metsänkäsittelypäätöksistä, hallinnosta sekä tuloista ja menoista. Suomessa tällaista palvelua ei vielä ole, muualla maailmassakin se on harvinaista lukuun ottamatta julkishallinnon metsiä. Metsänomistajakunnan muutoksen jatkuessa ja palveluiden käytön yleistyessä kokonaisvaltaiset omaisuudenhoitopalvelut yleistynevät myös metsäalalla samalla tavalla kuin ne ovat yleistyneet pankki- ja vakuutusalalla sekä finanssivarallisuuden hoidossa. Metsänvuokraus voidaan nähdä yhtenä tapana tuottaa metsänomistajalle omaisuudenhoitopalvelua, jolloin palvelun sisällöstä vuorovaikutteisesti sopiminen ja arvon tuottaminen maanomistajalle korostuvat. Metsänvuokrauksen arvolupaukset metsänomistajalle sisältävät metsien hoidon, helppouden sekä vakaan tuoton. Palveluntarjoajille ja vuokralaisille arvolupaukset sisältävät kumppanuuden sekä luotettavan ja ammattitaitoisen yhteistyöverkon sekä mittakaavaedut. Kun vuokrametsien pinta-ala on riittävä, luo syntynyt yhteistyöverkosto aineelliseen ja aineettomaan vaihdantaan (osaamisten täydentämiseen ja vuorovaikutukseen) ja työsuorituksiin perustuvaa arvoa. Tutkimuksen kuluessa kokonaisvaltaiselle omaisuudenhoitopalvelulle tunnistettiin kolme erilaista mittakaavatasoa: paikallinen pienimuotoinen metsänvuokrauspalvelu, alueellinen hieman laajamittaisempi palvelumalli sekä valtakunnallinen malli. Paikallisessa pienimuotoisessa mallissa vuokrauspalvelu toteutuu metsänomistajan sekä tilan sijaintikunnassa toimivan toisen aktiivisen metsänomistajan tai metsäpalveluyrityksen välisenä sopimuksena. Alueellinen vuokrauspalvelu voi perustua tietyn maakunnan tai metsänhoitoyhdistyksen alueella aktiivisesti toimivan toimijan tarjoamaan palveluun, jolloin palvelua voidaan tarjota periaatteessa kaikille kyseisen alueen metsänomistajille, joiden tilat ovat kiinnostavia vuokralaiselle. Valtakunnallinen malli tarjoaa käytännössä kaikkialla Suomessa sijaitsevien metsätilojen omistajille mahdollisuuden tarjota tilojaan vuokralle. Metsänvuokraus on mahdollista toteuttaa maanvuokralain mukaisena menettelynä, ja projekti tuotti tätä varten mallisopimuspohjan, joka on toimijoiden vapaasti käytettävissä. Projektin tiivistetyt loppupäätelmät ovat: • Metsänvuokraukseen perustuva kokonaisvaltainen metsäomaisuuden hoitopalvelu voidaan toteuttaa nykyisen lainsäädännön puitteissa maanvuokralakiin tukeutuen. • Metsänvuokraukseen liittyvän kielteisen maineen vuoksi palvelulle parempi termi voisi olla esimerkiksi metsäomaisuuden hoitopalvelu. • Kokonaisvaltaisen metsäomaisuuden hoitopalvelun, jos se toteutuisi mittakaavaltaan vähänkin laajempana, vaikutukset puun mobilisaatioon, metsäyrittäjyyteen ja metsätalouden kannattavuuteen voisivat olla merkittäviä. • Monet kolmea yllä mainittua mittakaavatasoa edustavat toimijatahot ovat olleet kiinnostu-neita palvelun tarjoamista liiketoimintamahdollisuuksista, yksityismetsänomistajien aidon kiinnostuksen selvittäminen edellyttää toimivan palvelun tuomista markkinoille. • Metsävuokrauksen yleistyminen edellyttää toimijoilta yksinkertaisen ja selkeän metsänvuokrauskonseptin kehittämistä ja testaamista (pilotointia) käytännössä, joka toimisi palvelun referenssinä.201

From multiscale biophysics to digital twins of tissues and organs: future opportunities for in silico pharmacology

With many advancements in in silico biology in recent years, the paramount challenge is to translate the accumulated knowledge into exciting industry partnerships and clinical applications. Achieving models that characterize the link of molecular interactions to the activity and structure of a whole organ are termed multiscale biophysics. Historically, the pharmaceutical industry has worked well with in silico models by leveraging their prediction capabilities for drug testing. However, the needed higher fidelity and higher resolution of models for efficient prediction of pharmacological phenomenon dictates that in silico approaches must account for the verifiable multiscale biophysical phenomena, as a spatial and temporal dimension variation for different processes and models. The collection of different multiscale models for different tissues and organs can compose digital twin solutions towards becoming a service for researchers, clinicians, and drug developers. Our paper has two main goals: 1) To clarify to what extent detailed single- and multiscale modeling has been accomplished thus far, we provide a review on this topic focusing on the biophysics of epithelial, cardiac, and brain tissues; 2) To discuss the present and future role of multiscale biophysics in in silico pharmacology as a digital twin solution by defining a roadmap from simple biophysical models to powerful prediction tools. Digital twins have the potential to pave the way for extensive clinical and pharmaceutical usage of multiscale models and our paper shows the basic fundamentals and opportunities towards their accurate development enabling the quantum leaps of future precise and personalized medical software.Comment: 30 pages, 10 figures, 1 tabl

Simulation-Based Study of Control Strategies for Beating of Human Cardiomyocyte Cultures

Peer reviewe

Sex differences in heart : from basics to clinics

Sex differences exist in the structure and function of human heart. The patterns of ventricular repolarization in normal electrocardiograms (ECG) differ in men and women: men ECG pattern displays higher T-wave amplitude and increased ST angle. Generally, women have longer QT duration because of reduced repolarization reserve, and thus, women are more susceptible for the occurrence of torsades de pointes associated with drugs prolonging ventricular repolarization. Sex differences are also observed in the prevalence, penetrance and symptom severity, and also in the prognosis of cardiovascular disease. Generally, women live longer, have less clinical symptoms of cardiac diseases, and later onset of symptoms than men. Sex hormones also play an important role in regulating ventricular repolarization, suggesting that hormones directly influence various cellular functions and adrenergic regulation. From the clinical perspective, sex-based differences in heart physiology are widely recognized, but in daily practice, cardiac diseases are often underdiagnosed and untreated in the women. The underlying mechanisms of sex differences are, however, poorly understood. Here, we summarize sex-dependent differences in normal cardiac physiology, role of sex hormones, and differences in drug responses. Furthermore, we also discuss the importance of human induced pluripotent stem cell-derived cardiomyocytes in further understanding the mechanism of differences in women and men.publishedVersionPeer reviewe

Sensitivity of the Human Ventricular BPS2020 Action Potential Model to the In Silico Mechanisms of Ischemia.

acceptedVersionPeer reviewe

Arrhythmia mechanisms in human induced pluripotent stem cell-derived cardiomyocytes

Despite major efforts by clinicians and researchers, cardiac arrhythmia remains a leading cause of morbidity and mortality in the world. Experimental work has relied on combining high-throughput strategies with standard molecular and electrophysiological studies, which are, to a great extent, based on the use of animal models. As this poses major challenges for translation, the progress in the development of novel antiarrhythmic agents and clinical care has been mostly disappointing. Recently, the advent of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) has opened new avenues for both basic cardiac research and drug discovery: now there is an unlimited source of CMs of human origin, both from healthy individuals and patients with cardiac diseases. Understanding arrhythmic mechanisms is one the main use-cases of hiPSC-CMs, in addition to pharmacological cardiotoxicity and efficacy testing, in vitro disease modeling, developing patient-specific models and personalized drugs, and regenerative medicine. Here, we review the advances that the hiPSC-based modeling systems have brought so far regarding the understanding of both arrhythmogenic triggers and substrates, while also briefly speculating about the possibilities in the future.publishedVersionPeer reviewe

Vascular Endothelial Growth Factor-B Induces a Distinct Electrophysiological Phenotype in Mouse Heart

Vascular endothelial growth factor B (VEGF-B) is a potentmediator of vascular, metabolic, growth, and stress responses in the heart, but the effects on cardiac muscle and cardiomyocyte function are not known. The purpose of this study was to assess the effects of VEGF-B on the energy metabolism, contractile, and electrophysiological properties of mouse cardiac muscle and cardiac muscle cells. In vivo and ex vivo analysis of cardiac-specific VEGF-B TG mice indicated that the contractile function of the TG hearts was normal. Neither the oxidative metabolism of isolated TG cardiomyocytes nor their energy substrate preference showed any difference to WT cardiomyocytes. Similarly, myocyte Ca2+ signaling showed only minor changes compared to WT myocytes. However, VEGF-B overexpression induced a distinct electrophysiological phenotype characterized by ECG changes such as an increase in QRSp time and decreases in S and R amplitudes. At the level of isolated TG cardiomyocytes, these changes were accompanied with decreased action potential upstroke velocity and increased duration (APD60-70). These changes were partly caused by downregulation of sodium current (INa) due to reduced expression of Nav1.5. Furthermore, TG myocytes had alterations in voltage-gated K + currents, namely decreased density of transient outward current (Ito) and total K + current (Ipeak). At the level of transcription, these were accompanied by downregulation of Kv channel-interacting protein 2 (Kcnip2), a knownmodulatory subunit for Kv4.2/3 channel. Cardiac VEGF-B overexpression induces a distinct electrophysiological phenotype including remodeling of cardiomyocyte ion currents, which in turn induce changes in action potential waveform and ECG.Peer reviewe