scholarly journals 3444 Development of human engineered cardiac tissue (hECT)-based screening assay to explore cardiac contractile properties in response to pharmacological challenge with proarrhythmic drugs

2019 ◽  
Vol 3 (s1) ◽  
pp. 8-8
Author(s):  
Francesca Stillitano ◽  
Irene C. Turnbull ◽  
Jaydev Dave ◽  
Jean-Sébastien Hulot ◽  
Roger J. Hajjar
Keyword(s):  
Cardiac Tissue ◽  
Calcium Transient ◽  
Peak Height ◽  
Contractile Properties ◽  
Pronounced Increase ◽  
Cardiac Contractile ◽  
Pharmacological Challenge ◽  
Beat Rate ◽  
Subject Specific ◽  
Sensitive Line

OBJECTIVES/SPECIFIC AIMS: The goals of this study were (1) to evaluate the effect of proarrhythmic drugs on calcium transient and (2) to use three-dimensional human engineered cardiac tissue (hECT) technology to evaluate cardiac contractile properties in response to pharmacological challenge with proarrhythmic drugs. METHODS/STUDY POPULATION: Calcium transient was measured in subject-specific iPSC-CMs by using the IonOptix system in Sotalol treated vs. untreated conditions. We fabricated human engineered cardiac tissues (hECT) in a custom designed bioreactor using low- and high-sentitive subject-specific iPSC-CMs. Contractile function of the hECT was evaluated at baseline and after Sotalol [300 µM] administration. The change in beat rate was recorded under spontaneous beating conditions; changes in other twitch parameters, including time to relaxation, were recorded under electrical stimulation. Time to relaxation served as an indicator of action potential duration (APD), which has a temporal correlation with the QT interval. RESULTS/ANTICIPATED RESULTS: The low-sensitive iPSC-CM showed a considerable drop in overall peak height of the calcium transient, in the presence of 100 µM Sotalol. The high-sensitive line, however, showed a more pronounced drop in peak height. Sotalol treatment also induced a more pronounced increase in the exponential decay time constant (tau) in the high-sensitive line compared to the low-sensitive line. The hECT fabricated with high sensitive hiPSC-CM showed a larger decrease in spontaneous beat rate in response to Sotalol (0.41 vs 0.23 fold decrease), with a higher increase in time to relaxation (1.8 vs 1.3 fold increase), compared to hECT from low sensitive hiPSC-CM. Moreover, while the low-sensitive hECT showed a positive correlation between time to relaxation and developed force, as expected after Sotalol stimulation; the high-sensitive hECT failed to show a positive inotropic response. DISCUSSION/SIGNIFICANCE OF IMPACT: Our findings suggest subject-specific iPSC-CMs and hECT, can be used to model functional abnormalities observed in diLQTS in response to Sotalol, and offer novel insights into human-based screening assays for toxic drug reactions. Success of this study may help identify key components underlying diLQT susceptibility to ultimately develop novel therapeutic agents.

Abstract 20385: Pregnancy-Induced Cardiac Hypertrophy is Accompanied by Unique Contractile Properties Not Seen in Other Forms of Physiological Hypertrophy

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Jessica Tyrrell ◽  
Kaitlyn Kennard ◽  
Catherine Makarewich ◽  
Beth A Bailey
Keyword(s):  
Cardiac Hypertrophy ◽  
Late Pregnancy ◽  
Calcium Transient ◽  
Contractile Properties ◽  
Receptor Protein ◽  
Ca Channel ◽  
Adrenergic Stimulation ◽  
Twitch Contraction ◽  
Relaxation Phase ◽  
Near Term

Background: Cardiac hypertrophy accompanying pregnancy has generally been categorized as physiologic hypertrophy similar to that seen with exercise, however a reduction in cardiac function in late pregnancy has been suggested. Furthermore, the hemodynamic stress of pregnancy can induce a maladaptive, pathologic hypertrophy in a small number of women. This study seeks to characterize the contractile properties of late-pregnant myocardium. Methods and Results: Late Pregnancy (LP) Female Swiss-Webster mice were bred then studied at near term (Embryonic day 17-19) and compared to age-matched, non-pregnant (NP) controls. Individual cardiac myocytes were isolated using collagenase-based perfusion technique. Two-dimensional Surface Area measured in quiescent cells was elevated (p<.01) in LP myocytes (LPM) (3609± 132u 2 ) vs NP myocytes (NPM) (2736± 88u 2 ), and this increase was due to increases in both length (8.5%) and width (15.6%). Western Blot analysis showed a reduction in Ryanodine Receptor protein in LP, but no differences in L-type Ca Channel, SERCA or Phospholamban levels. Sarcomere length (light diffraction) and Ca 2+ transients (fluo-3) were measured at pacing rates of 1 Hz and at bath [Ca] of 2mM. Duration of twitch contraction was prolonged (p<.05) in LPM as measured by Time to 75% Recovery (.42 ± .02 vs .37 ±.01 sec in NPM) and Time to 90% recovery (.51 ± .02 vs .45 ± .02 sec in NPM). There were no differences in other contractile parameters measured or in the fluo-3 calcium transient properties. 10 -7 M Isoproterenol (ISO) was used to determine the responsiveness to adrenergic stimulation. ISO induced significantly enhanced contractility in both LPM and NPM, and the response was heightened in LPM such that the presence of ISO normalized the differences in the duration of twitch contraction between LPM and NPM. Conclusions: These results suggest that hypertrophied LPM have characteristics of both physiologic and pathologic hypertrophy including enhanced responsiveness to ISO and a prolonged relaxation phase. The prolongation of relaxation is not seen in physiologic hypertrophy induced by exercise and may contribute to the diastolic dysfunction reported in some pregnancies. Enhanced response to ISO suggests an increased cardiac reserve in LPM.

Regulation of calcium dynamics and propagation velocity by tissue microstructure in engineered strands of cardiac tissue

2020 ◽  
Vol 12 (2) ◽  
pp. 34-46
Author(s):  
Andrew P Petersen ◽  
Nathan Cho ◽  
Davi M Lyra-Leite ◽  
Jeffrey W Santoso ◽  
Divya Gupta ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Rise Time ◽  
Propagation Velocity ◽  
Cardiac Tissue ◽  
Correlation Coefficients ◽  
Calcium Transient ◽  
Calcium Transients ◽  
Calcium Cycling ◽  
Tissue Microstructure ◽  
Transient Rise

Abstract Disruptions to cardiac tissue microstructure are common in diseased or injured myocardium and are known substrates for arrhythmias. However, we have a relatively coarse understanding of the relationships between myocardial tissue microstructure, propagation velocity and calcium cycling, due largely to the limitations of conventional experimental tools. To address this, we used microcontact printing to engineer strands of cardiac tissue with eight different widths, quantified several structural and functional parameters and established correlation coefficients. As strand width increased, actin alignment, nuclei density, sarcomere index and cell aspect ratio decreased with unique trends. The propagation velocity of calcium waves decreased and the rise time of calcium transients increased with increasing strand width. The decay time constant of calcium transients decreased and then slightly increased with increasing strand width. Based on correlation coefficients, actin alignment was the strongest predictor of propagation velocity and calcium transient rise time. Sarcomere index and cell aspect ratio were also strongly correlated with propagation velocity. Actin alignment, sarcomere index and cell aspect ratio were all weak predictors of the calcium transient decay time constant. We also measured the expression of several genes relevant to propagation and calcium cycling and found higher expression of the genes that encode for connexin 43 (Cx43) and a subunit of L-type calcium channels in thin strands compared to isotropic tissues. Together, these results suggest that thinner strands have higher values of propagation velocity and calcium transient rise time due to a combination of favorable tissue microstructure and enhanced expression of genes for Cx43 and L-type calcium channels. These data are important for defining how microstructural features regulate intercellular and intracellular calcium handling, which is needed to understand mechanisms of propagation in physiological situations and arrhythmogenesis in pathological situations.

Parathyroid hormone acutely elevates intracellular calcium in osteoblastlike cells

1987 ◽  
Vol 253 (1) ◽  
pp. E45-E51 ◽  
Author(s):  
I. R. Reid ◽  
R. Civitelli ◽  
L. R. Halstead ◽  
L. V. Avioli ◽  
K. A. Hruska
Keyword(s):  
Parathyroid Hormone ◽  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Calcium Transient ◽  
Peak Height ◽  
Base Line ◽  
Osteosarcoma Cell ◽  
Cellular Processes ◽  
Osteoblastic Phenotype ◽  
Umr 106

Changes in cytoplasmic calcium concentration ([Ca2+]i) activate numerous cellular processes thus mediating the effects of a number of hormones, but whether this mechanism is involved in the activation of osteoblasts by parathyroid hormone (PTH) remains uncertain. To examine this question, [Ca2+]i has been measured in suspensions of UMR 106 cells, a rodent osteosarcoma cell line with an osteoblastic phenotype. Basal [Ca2+]i was 137 +/- 3.7 nM (n = 60) and after the addition of rat PTH-(1–34) [rPTH-(1-34)] there was a rapid, dose-related increase with return to base line within 1 min. Half-maximal stimulation was produced by 5 X 10(-8) M rPTH-(1-34). Complexing of intracellular calcium by EGTA addition immediately before that of rPTH did not affect the calcium transient; neither did MnCl2 (10(-4) M) nor diltiazem (10(-4) M). Verapamil (10(-5) M) reduced the [Ca2+]i peak height after rPTH to 0.48 +/- 0.14 of control (n = 7). 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoic acid and dantrolene both reduced the [Ca2+]i response to rPTH (0.65 +/- 0.08 and 0.29 +/- 0.13 of control, respectively). Forskolin (10(-6) and 10(-5) M) produced a slight [Ca2+]i transient smaller in amplitude than seen with PTH. It is concluded that PTH mobilizes an intracellular calcium pool in these osteoblastlike cells, and the predominant mechanism for this is independent of cAMP.

scholarly journals The fungicide Tebuconazole induces electromechanical cardiotoxicity in murine hearts

2021 ◽  
Author(s):  
Artur Santos-Miranda ◽  
Julliane V Joviano-Santos ◽  
Taynara Cruz-Nascimento ◽  
Diego Santos Souza ◽  
Leisiane Marques ◽  
...  
Keyword(s):  
Action Potential ◽  
Cardiac Tissue ◽  
Ex Vivo ◽  
Calcium Transient ◽  
Acute Exposure ◽  
Sodium Calcium Exchanger ◽  
Whole Cell Patch Clamp ◽  
Toxicological Studies ◽  
Qt Interval Duration

Tebuconazole (TEB) is an important fungicide that belongs to the triazole family. It is largely applied in agriculture and its use has increased in the last decade. Since TEB is stable in water and soil, long-term exposure of humans to this pesticide is a real threat. Acute toxicological studies to uncover the toxicity of TEB are limited, and there is evidence of an association between long-term exposure to TEB and damage of several biological systems, including hepatotoxicity and cardiotoxicity. In this paper, the effects of acute exposure of cardiomyocytes and murine hearts to TEB were addressed to elucidate its impact on electromechanical properties of the cardiac tissue. In whole-cell patch-clamp records, TEB inhibited both the total outward potassium current (IC50=5.7±1.5 μmol.l−1) and the L-type calcium current (IC50=33.2±7.4 μmol.l−1). Acute exposure to TEB at 30 μmol.l−1 prolonged the action potential duration as well as an induced out-of-pace action potential, and increased the sodium/calcium exchanger current in its forward and reverse modes. Moreover, sarcomere shortening and calcium transient in isolated cardiomyocytes was enhanced when cells were exposed to TEB at 30 μmol.l−1. In ex vivo experiments, TEB 30 μmol.l−1 caused significant electrocardiogram remodeling with prolonged PR, QRS, and QT interval duration. Accordingly, TEB exposure was prone to the appearance of arrhythmias. Combined, our results demonstrate that acute TEB exposure affects the cardiomyocyte's electro-contractile properties and triggers the appearance of ECG abnormalities, including conduction defects and arrhythmias.

Controlling Morphology and Functions of Cardiac Organoids by Two-Dimensional Geometrical Templates

2022 ◽  
Author(s):  
Plansky Hoang ◽  
Shiyang Sun ◽  
Bearett A. Tarris ◽  
Zhen Ma
Keyword(s):  
Stem Cells ◽  
Self Assembly ◽  
Cardiac Tissue ◽  
Spherical Shape ◽  
Cardiac Contractile ◽  
Complex Shapes ◽  
The Matrix ◽  
Specific Geometry ◽  
Induced Pluripotent ◽  
And Function

Traditionally, tissue-specific organoids are generated as 3D aggregates of stem cells embedded in Matrigel or hydrogels, and the aggregates eventually end up a spherical shape and suspended in the matrix. Lack of geometrical control of organoid formation makes these spherical organoids limited for modeling the tissues with complex shapes. To address this challenge, we developed a new method to generate 3D spatial-organized cardiac organoids from 2D micropatterned hiPSC colonies, instead of directly from 3D stem cell aggregates. This new approach opens the possibility to create cardiac organoids that are templated by 2D non-spherical geometries, which potentially provides us a deeper understanding of biophysical controls on developmental organogenesis. Here, we designed 2D geometrical templates with quadrilateral shapes and pentagram shapes that had same total area but different geometrical shapes. Using this templated substrate, we grew cardiac organoids from human induced pluripotent stem cells (hiPSCs) and collected a series of parameters to characterize morphological and functional properties of the cardiac organoids. In quadrilateral templates, we found that increasing the aspect ratio impaired cardiac tissue 3D self-assembly, but the elongated geometry improved the cardiac contractile functions. However, in pentagram templates, cardiac organoid structure and function were optimized with a specific geometry of an ideal star shape. This study will shed a light on “organogenesis-by-design” by increasing the intricacy of starting templates from external geometrical cues to improve the organoid morphogenesis and functionality.

Effect of exercise conditioning on excitation-contraction coupling in aged rats

1990 ◽  
Vol 69 (4) ◽  
pp. 1366-1371 ◽  
Author(s):  
J. K. Gwathmey ◽  
M. T. Slawsky ◽  
C. L. Perreault ◽  
G. M. Briggs ◽  
J. P. Morgan ◽  
...  
Keyword(s):  
Action Potential ◽  
Right Ventricular ◽  
Cardiac Tissue ◽  
Calcium Transient ◽  
Isometric Tension ◽  
Aged Rats ◽  
Time To Peak ◽  
Age Related ◽  
Electrophysiological Recordings ◽  
Norepinephrine Content

We studied aged (24-26 mo) Fischer 344 rats after they underwent 8 wk of moderate exercise conditioning. Right ventricular papillary muscles were loaded with the calcium indicator aequorin. Electrophysiological recordings were also performed. Time to peak isometric tension in muscles from exercised aged rats (EAR) was shorter than in those from unexercised aged rats (UAR) (126 +/- 7 vs. 167 +/- 7 ms; P less than 0.01). Time to 50% relaxation from peak isometric tension was also shorter in EAR than in UAR (88 +/- 3 vs. 119 +/- 12 ms; P less than 0.05). There was a trend toward decrease in time to peak light and a significant decrease in time to 50% decline from peak light (33 +/- 4 ms in EAR vs. 59 +/- 17 ms in UAR; P = 0.001). Action potential amplitude was smaller in EAR than in UAR (67 +/- 4 vs. 82 +/- 3 mV; P = 0.003); however, action potential duration was longer (137 +/- 6 ms in EAR vs. 100 +/- 10 ms in UAR; P = 0.005). Right ventricular-to-body weight ratios revealed no evidence of hypertrophy in EAR compared with UAR. Cardiac tissue norepinephrine content was significantly greater in EAR than in UAR (1,212 +/- 25 vs. 630 +/- 105 ng/tissue; P = 0.02). In summary, exercise reversed the age-related prolongation of isometric contraction and associated intracellular calcium transient in the aged rat while it prolonged the transmembrane action potential. In addition, exercise in aged rats resulted in an increase in cardiac norepinephrine content.

Sign in / Sign up

Export Citation Format

Share Document