scholarly journals Fibrotic Remodeling during Persistent Atrial Fibrillation: In Silico Investigation of the Role of Calcium for Human Atrial Myofibroblast Electrophysiology

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2852
Author(s):  
Jorge Sánchez ◽  
Beatriz Trenor ◽  
Javier Saiz ◽  
Olaf Dössel ◽  
Axel Loewe
Keyword(s):  
Atrial Fibrillation ◽  
In Silico ◽  
Cardiac Tissue ◽  
Persistent Atrial Fibrillation ◽  
Distribution Patterns ◽  
Tissue Level ◽  
Resting Membrane Potential ◽  
Model Parameters

During atrial fibrillation, cardiac tissue undergoes different remodeling processes at different scales from the molecular level to the tissue level. One central player that contributes to both electrical and structural remodeling is the myofibroblast. Based on recent experimental evidence on myofibroblasts’ ability to contract, we extended a biophysical myofibroblast model with Ca2+ handling components and studied the effect on cellular and tissue electrophysiology. Using genetic algorithms, we fitted the myofibroblast model parameters to the existing in vitro data. In silico experiments showed that Ca2+ currents can explain the experimentally observed variability regarding the myofibroblast resting membrane potential. The presence of an L-type Ca2+ current can trigger automaticity in the myofibroblast with a cycle length of 799.9 ms. Myocyte action potentials were prolonged when coupled to myofibroblasts with Ca2+ handling machinery. Different spatial myofibroblast distribution patterns increased the vulnerable window to induce arrhythmia from 12 ms in non-fibrotic tissue to 22 ± 2.5 ms and altered the reentry dynamics. Our findings suggest that Ca2+ handling can considerably affect myofibroblast electrophysiology and alter the electrical propagation in atrial tissue composed of myocytes coupled with myofibroblasts. These findings can inform experimental validation experiments to further elucidate the role of myofibroblast Ca2+ handling in atrial arrhythmogenesis.

scholarly journals Persistent Atrial Fibrillation: The Role of Left Atrial Posterior Wall Isolation and Ablation Strategies

2021 ◽  
Vol 10 (14) ◽  
pp. 3129
Author(s):  
Riyaz A. Kaba ◽  
Aziz Momin ◽  
John Camm
Keyword(s):  
Atrial Fibrillation ◽  
Left Atrial ◽  
Pulmonary Veins ◽  
Treatment Strategies ◽  
Persistent Atrial Fibrillation ◽  
Posterior Wall ◽  
Cardiovascular Death ◽  
Good Effect ◽  
Complex Forms

Atrial fibrillation (AF) is a global disease with rapidly rising incidence and prevalence. It is associated with a higher risk of stroke, dementia, cognitive decline, sudden and cardiovascular death, heart failure and impairment in quality of life. The disease is a major burden on the healthcare system. Paroxysmal AF is typically managed with medications or endocardial catheter ablation to good effect. However, a large proportion of patients with AF have persistent or long-standing persistent AF, which are more complex forms of the condition and thus more difficult to treat. This is in part due to the progressive electro-anatomical changes that occur with AF persistence and the spread of arrhythmogenic triggers and substrates outside of the pulmonary veins. The posterior wall of the left atrium is a common site for these changes and has become a target of ablation strategies to treat these more resistant forms of AF. In this review, we discuss the role of the posterior left atrial wall in persistent and long-standing persistent AF, the limitations of current endocardial-focused treatment strategies, and future perspectives on hybrid epicardial–endocardial approaches to posterior wall isolation or ablation.

scholarly journals Antidiabetic activity of some pentacyclic acid triterpenoids, role of PTP–1B: In vitro, in silico, and in vivo approaches

2011 ◽  
Vol 46 (6) ◽  
pp. 2243-2251 ◽  
Author(s):  
Juan José Ramírez-Espinosa ◽  
Maria Yolanda Rios ◽  
Sugey López-Martínez ◽  
Fabian López-Vallejo ◽  
José L. Medina-Franco ◽  
...  
Keyword(s):  
In Silico ◽  
Antidiabetic Activity ◽  
Ptp 1B

Role of Scar and Rotors in Persistent Atrial Fibrillation

2021 ◽  
Vol 7 (7) ◽  
pp. 920-922
Author(s):  
Ravi Mandapati ◽  
Tahmeed Contractor ◽  
Rahul Bhardwaj
Keyword(s):  
Atrial Fibrillation ◽  
Persistent Atrial Fibrillation

Abstract P780: Myosin Light Chain Dephosphorylation by Ppp1r12c Promotes Atrial Hypocontractility in Atrial Fibrillation

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Francisco J Gonzalez-Gonzalez ◽  
Perike Srikanth ◽  
Andrielle E Capote ◽  
Alsina Katherina M ◽  
Benjamin Levin ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Molecular Mechanisms ◽  
Contractile Function ◽  
Right Atrial ◽  
Western Blots

Atrial fibrillation (AF) is the most common sustained arrhythmia, with an estimated prevalence in the U.S.of 6.1 million. AF increases the risk of a thromboembolic stroke in five-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function in AF remains unknown. We have recently identified protein phosphatase 1 subunit 12c (PPP1R12C) as a key molecule targeting myosin light-chain phosphorylation in AF. Objective: We hypothesize that the overexpression of PPP1R12C causes hypophosphorylation of atrial myosin light-chain 2 (MLC2a), thereby decreasing atrial contractility in AF. Methods and Results: Left and right atrial appendage tissues were isolated from AF patients versus sinus rhythm (SR). To evaluate the role of the PP1c-PPP1R12C interaction in MLC2a de-phosphorylation, we utilized Western blots, co-immunoprecipitation, and phosphorylation assays. In patients with AF, PPP1R12C expression was increased 3.5-fold versus SR controls with an 88% reduction in MLC2a phosphorylation. PPP1R12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF. In vitro studies of either pharmacologic (BDP5290) or genetic (T560A), PPP1R12C activation demonstrated increased PPP1R12C binding with both PP1c and MLC2a, and dephosphorylation of MLC2a. Additionally, to evaluate the role of PPP1R12C expression in cardiac function, mice with lentiviral cardiac-specific overexpression of PPP1R12C (Lenti-12C) were evaluated for atrial contractility using echocardiography, versus wild-type and Lenti-controls. Lenti-12C mice demonstrated a 150% increase in left atrium size versus controls, with reduced atrial strain and atrial ejection fraction. Also, programmed electrical stimulation was performed to evaluate AF inducibility in vivo. Pacing-induced AF in Lenti-12C mice was significantly higher than controls. Conclusion: The overexpression of PPP1R12C increases PP1c targeting to MLC2a and provokes dephosphorylation, associated with a reduction in atrial contractility and an increase in AF inducibility. All these discoveries suggest that PP1 regulation of sarcomere function at MLC2a is a main regulator of atrial contractility in AF.

Abstract P458: Myosin Light Chain Dephosphorylation By Ppp1r12c Promotes Atrial Hypocontractility In Atrial Fibrillation

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Francisco J Gonzalez-Gonzalez ◽  
Srikanth Perike ◽  
Frederick Damen ◽  
Andrielle Capote ◽  
Katherina M Alsina ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Molecular Mechanisms ◽  
Contractile Function ◽  
Right Atrial ◽  
Western Blots

Introduction: Atrial fibrillation (AF), is the most common sustained arrhythmia, with an estimated prevalence in the U.S. of 2.7 million to 6.1 million and is predictive to increase to 12.1 million in 2030. AF increases the chances of a thromboembolic stroke in five-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function in AF remains unknown. Objective: The overexpression of PPP1R12C, causes hypophosphorylation of atrial myosin light chain 2 (MLC2a), decreasing atrial contractility. Methods and Results: Left and right atrial appendage tissues were isolated from AF patients versus sinus rhythm (SR). To evaluated the role of PP1c-PPP1R12C interaction in MLC2a de-phosphorylation we used Western blots, coimmunoprecipitation, and phosphorylation assays. In patients with AF, PPP1R12C expression was increased 3.5-fold versus SR controls with an 88% reduction in MLC2a phosphorylation. PPP1R12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF. In vitro studies of either pharmacologic (BDP5290) or genetic (T560A) PPP1R12C activation demonstrated increased PPP1R12C binding with both PP1c and MLC2a, and dephosphorylation of MLC2a. Additionally, to evaluate the role of PPP1R12C expression in cardiac function, mice with lentiviral cardiac-specific overexpression of PPP1R12C (Lenti-12C) were evaluated for atrial contractility using echocardiography, versus wild-type and Lenti-controls. Lenti-12C mice demonstrated a 150% increase in left atrium size versus controls, with reduced atrial strain and atrial ejection fraction. Also, programmed electrical stimulation was performed to evaluate AF inducibility in vivo. Pacing-induced AF in Lenti-12C mice was significantly higher than controls. Conclusion: The Overexpression of PPP1R12C increases PP1c targeting to MLC2a and provokes dephosphorylation, that cause a reduction in atrial contractility and increases AF inducibility. All these discoveries advocate that PP1 regulation of sarcomere function at MLC2a is a main regulator of atrial contractility in AF.

scholarly journals Haemodynamic flow conditions at the initiation of high-shear platelet aggregation: a combined in vitro and cellular in silico study

2020 ◽  
Vol 11 (1) ◽  
pp. 20190126 ◽  
Author(s):  
B. J. M. van Rooij ◽  
G. Závodszky ◽  
A. G. Hoekstra ◽  
D. N. Ku
Keyword(s):  
Platelet Aggregation ◽  
In Silico ◽  
Platelet Rich Plasma ◽  
High Shear ◽  
Shear Rates ◽  
Flow Simulations ◽  
In Silico Study ◽  
Platelet Aggregates

The influence of the flow environment on platelet aggregation is not fully understood in high-shear thrombosis. The objective of this study is to investigate the role of a high shear rate in initial platelet aggregation. The haemodynamic conditions in a microfluidic device are studied using cell-based blood flow simulations. The results are compared with in vitro platelet aggregation experiments performed with porcine whole blood (WB) and platelet-rich-plasma (PRP). We studied whether the cell-depleted layer in combination with high shear and high platelet flux can account for the distribution of platelet aggregates. High platelet fluxes at the wall were found in silico . In WB, the platelet flux was about twice as high as in PRP. Additionally, initial platelet aggregation and occlusion were observed in vitro in the stenotic region. In PRP, the position of the occlusive thrombus was located more downstream than in WB. Furthermore, the shear rates and stresses in cell-based and continuum simulations were studied. We found that a continuum simulation is a good approximation for PRP. For WB, it cannot predict the correct values near the wall.

scholarly journals Inherited and Acquired Rhythm Disturbances in Sick Sinus Syndrome, Brugada Syndrome, and Atrial Fibrillation: Lessons from Preclinical Modeling

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 3175
Author(s):  
Laura Iop ◽  
Sabino Iliceto ◽  
Giovanni Civieri ◽  
Francesco Tona
Keyword(s):  
Atrial Fibrillation ◽  
Cardiovascular Diseases ◽  
Brugada Syndrome ◽  
In Silico ◽  
Cardiac Fibrosis ◽  
Sick Sinus Syndrome ◽  
In Vitro Models ◽  
Global Functioning

Rhythm disturbances are life-threatening cardiovascular diseases, accounting for many deaths annually worldwide. Abnormal electrical activity might arise in a structurally normal heart in response to specific triggers or as a consequence of cardiac tissue alterations, in both cases with catastrophic consequences on heart global functioning. Preclinical modeling by recapitulating human pathophysiology of rhythm disturbances is fundamental to increase the comprehension of these diseases and propose effective strategies for their prevention, diagnosis, and clinical management. In silico, in vivo, and in vitro models found variable application to dissect many congenital and acquired rhythm disturbances. In the copious list of rhythm disturbances, diseases of the conduction system, as sick sinus syndrome, Brugada syndrome, and atrial fibrillation, have found extensive preclinical modeling. In addition, the electrical remodeling as a result of other cardiovascular diseases has also been investigated in models of hypertrophic cardiomyopathy, cardiac fibrosis, as well as arrhythmias induced by other non-cardiac pathologies, stress, and drug cardiotoxicity. This review aims to offer a critical overview on the effective ability of in silico bioinformatic tools, in vivo animal studies, in vitro models to provide insights on human heart rhythm pathophysiology in case of sick sinus syndrome, Brugada syndrome, and atrial fibrillation and advance their safe and successful translation into the cardiology arena.

scholarly journals Isolation, Characterization, and Agent-Based Modeling of Mesenchymal Stem Cells in a Bio-construct for Myocardial Regeneration Scaffold Design

Data ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 71 ◽  
Author(s):  
Diana Victoria Ramírez López ◽  
María Isabel Melo Escobar ◽  
Carlos A. Peña-Reyes ◽  
Álvaro J. Rojas Arciniegas ◽  
Paola Andrea Neuta Arciniegas
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
In Silico ◽  
Cardiac Tissue ◽  
Cellular Level ◽  
Cell Behavior ◽  
Agent Based Model ◽  
Agent Based ◽  
And Migration

Regenerative medicine involves methods to control and modify normal tissue repair processes. Polymer and cell constructs are under research to create tissue that replaces the affected area in cardiac tissue after myocardial infarction (MI). The aim of the present study is to evaluate the behavior of differentiated and undifferentiated mesenchymal stem cells (MSCs) in vitro and in silico and to compare the results that both offer when it comes to the design process of biodevices for the treatment of infarcted myocardium in biomodels. To assess in vitro behavior, MSCs are isolated from rat bone marrow and seeded undifferentiated and differentiated in multiple scaffolds of a gelled biomaterial. Subsequently, cell behavior is evaluated by trypan blue and fluorescence microscopy, which showed that the cells presented high viability and low cell migration in the biomaterial. An agent-based model intended to reproduce as closely as possible the behavior of individual MSCs by simulating cellular-level processes was developed, where the in vitro results are used to identify parameters in the agent-based model that is developed, and which simulates cellular-level processes: Apoptosis, differentiation, proliferation, and migration. Thanks to the results obtained, suggestions for good results in the design and fabrication of the proposed scaffolds and how an agent-based model can be helpful for testing hypothesis are presented in the discussion. It is concluded that assessment of cell behavior through the observation of viability, proliferation, migration, inflammation reduction, and spatial composition in vitro and in silico, represents an appropriate strategy for scaffold engineering.

scholarly journals Role of mechanical cues and hypoxia on the growth of tumor cells in strong and weak confinement: A dual in vitro–in silico approach

2020 ◽  
Vol 6 (13) ◽  
pp. eaaz7130 ◽  
Author(s):  
V. Le Maout ◽  
K. Alessandri ◽  
B. Gurchenkov ◽  
H. Bertin ◽  
P. Nassoy ◽  
...  
Keyword(s):  
In Silico ◽  
Time Course ◽  
Growth Dynamics ◽  
Tumor Model ◽  
Mechanistic Modeling ◽  
Physical Factors ◽  
Factors Affecting ◽  
Numerical Studies

Characterization of tumor growth dynamics is of major importance for cancer understanding. By contrast with phenomenological approaches, mechanistic modeling can facilitate disclosing underlying tumor mechanisms and lead to identification of physical factors affecting proliferation and invasive behavior. Current mathematical models are often formulated at the tissue or organ scale with the scope of a direct clinical usefulness. Consequently, these approaches remain empirical and do not allow gaining insight into the tumor properties at the scale of small cell aggregates. Here, experimental and numerical studies of the dynamics of tumor aggregates are performed to propose a physics-based mathematical model as a general framework to investigate tumor microenvironment. The quantitative data extracted from the cellular capsule technology microfluidic experiments allow a thorough quantitative comparison with in silico experiments. This dual approach demonstrates the relative impact of oxygen and external mechanical forces during the time course of tumor model progression.

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