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Engineered heart slices for electrophysiological and contractile studies.

ABSTRACT: A major consideration in the design of engineered cardiac tissues for the faithful representation of physiological behavior is the recapitulation of the complex topography and biochemistry of native tissue. In this study we present engineered heart slices (EHS), which consist of neonatal rat ventricular cells (NRVCs) seeded onto thin slices of decellularized cardiac tissue that retain important aspects of native extracellular matrix (ECM). To form EHS, rat or pig ventricular tissue was sectioned into 300 ?m-thick, 5 to 16 mm-diameter disks, which were subsequently decellularized using detergents, spread on coverslips, and seeded with NRVCs. The organized fiber structure of the ECM remained after decellularization and promoted cell elongation and alignment, resulting in an anisotropic, functional tissue that could be electrically paced. Contraction decreased at higher pacing rates, and optical mapping revealed electrical conduction that was anisotropic with a ratio of approximately 2.0, rate-dependent shortening of the action potential and slowing of conduction, and slowing of conduction by the sodium channel blocker lidocaine. Reentrant arrhythmias could also be pace-induced and terminated. EHS constitute an attractive in vitro cardiac tissue in which cardiac cells are cultured on thin slices of decellularized cardiac ECM that provide important biochemical, structural, and mechanical cues absent in traditional cell cultures.

SUBMITTER: Blazeski A

PROVIDER: S-EPMC4780840 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Engineered heart slices for electrophysiological and contractile studies.

Blazeski Adriana A Kostecki Geran M GM Tung Leslie L

Biomaterials 20150417

A major consideration in the design of engineered cardiac tissues for the faithful representation of physiological behavior is the recapitulation of the complex topography and biochemistry of native tissue. In this study we present engineered heart slices (EHS), which consist of neonatal rat ventricular cells (NRVCs) seeded onto thin slices of decellularized cardiac tissue that retain important aspects of native extracellular matrix (ECM). To form EHS, rat or pig ventricular tissue was sectioned ...[more]

PMID: 25934457

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Project description:BackgroundOne third of heart failure patients exhibit dyssynchronized electromechanical activity of the heart (evidenced by a broad QRS-complex). Cardiac resynchronization therapy (CRT) in the form of biventricular pacing improves cardiac output and clinical outcome of responding patients. Technically demanding and laborious large animal models have been developed to better predict responders of CRT and to investigate molecular mechanisms of dyssynchrony and CRT. The aim of this study was to establish a first humanized in vitro model of dyssynchrony and CRT.MethodsCardiomyocytes were differentiated from human induced pluripotent stem cells and cast into a fibrin matrix to produce engineered heart tissue (EHT). EHTs were either field stimulated in their entirety (symmetrically) or excited locally from one end (asymmetrically) or they were allowed to beat spontaneously.ResultsAsymmetrical pacing led to a depolarization wave from one end to the other end, which was visualized in human EHT transduced with a fast genetic Ca2+-sensor (GCaMP6f) arguing for dyssynchronous excitation. Symmetrical pacing in contrast led to an instantaneous (synchronized) Ca2+-signal throughout the EHT. To investigate acute and long-term functional effects, spontaneously beating human EHTs (0.5-0.8 Hz) were divided into a non-paced control group, a symmetrically and an asymmetrically paced group, each stimulated at 1 Hz. Symmetrical pacing was clearly superior to asymmetrical pacing or no pacing regarding contractile force both acutely and even more pronounced after weeks of continuous stimulation. Contractile dysfunction that can be evoked by an increased afterload was aggravated in the asymmetrically paced group. Consistent with reports from paced dogs, p38MAPK and CaMKII-abundance was higher under asymmetrical than under symmetrical pacing while pAKT was considerably lower.ConclusionsThis model allows for long-term pacing experiments mimicking electrical dyssynchrony vs. synchrony in vitro. Combined with force measurement and afterload stimulus manipulation, it provides a robust new tool to gain insight into the biology of dyssynchrony and CRT.

Project description:Engineered heart tissues (EHTs) have emerged as a robust in vitro model to study cardiac physiology. Although biomimetic culture environments have been developed to better approximate in vivo conditions, currently available methods do not permit full recapitulation of the four phases of the cardiac cycle. We have developed a bioreactor which allows EHTs to undergo cyclic loading sequences that mimic in vivo work loops. EHTs cultured under these working conditions exhibited enhanced concentric contractions but similar isometric contractions compared with EHTs cultured isometrically. EHTs that were allowed to shorten cyclically in culture had increased capacity for contractile work when tested acutely. Increased work production was correlated with higher levels of mitochondrial proteins and mitochondrial biogenesis; this effect was eliminated when tissues were cyclically shortened in the presence of a myosin ATPase inhibitor. Leveraging our novel in vitro method to precisely apply mechanical loads in culture, we grew EHTs under two loading regimes prescribing the same work output but with different associated afterloads. These groups showed no difference in mitochondrial protein expression. In loading regimes with the same afterload but different work output, tissues subjected to higher work demand exhibited elevated levels of mitochondrial protein. Our findings suggest that regulation of mitochondrial mass in cultured human EHTs is potently modulated by the mechanical work the tissue is permitted to perform in culture, presumably communicated through ATP demand. Precise application of mechanical loads to engineered heart tissues in culture represents a novel in vitro method for studying physiological and pathological cardiac adaptation.NEW & NOTEWORTHY In this work, we present a novel bioreactor that allows for active length control of engineered heart tissues during extended tissue culture. Specific length transients were designed so that engineered heart tissues generated complete cardiac work loops. Chronic culture with various work loops suggests that mitochondrial mass and biogenesis are directly regulated by work output.

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Engineered heart slices for electrophysiological and contractile studies.

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Engineered heart slices for electrophysiological and contractile studies.

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