Increased fibroblast accumulation in the equine heart following persistent atrial fibrillation.
Abstract: Fibroblasts maintain the extracellular matrix homeostasis and may couple to cardiomyocytes through gap junctions and thereby increase the susceptibility to slow conduction and cardiac arrhythmias, such as atrial fibrillation (AF). In this study, we used an equine model of persistent AF to characterize structural changes and the role of fibroblasts in the development of an arrhythmogenic substrate for AF. Methods: Eleven horses were subjected to atrial tachypacing until self-sustained AF developed and were kept in AF for six weeks. Horses in sinus rhythm (SR) served as control. In terminal open-chest experiments conduction velocity (CV) was measured. Tissue was harvested and stained from selected sites. Automated image analysis was performed to assess fibrosis, fibroblasts, capillaries and various cardiomyocyte characteristics. Results: Horses in SR showed a rate-dependent slowing of CV, while in horses with persistent AF this rate-dependency was completely abolished (CV•basic cycle length relation p = 0.0295). Overall and interstitial amounts of fibrosis were unchanged, but an increased fibroblast count was found in left atrial appendage, Bachmann's bundle, intraatrial septum and pulmonary veins (p < 0.05 for all) in horses with persistent AF. The percentage of α-SMA expressing fibroblasts remained the same between the groups. Conclusions: Persistent AF resulted in fibroblast accumulation in several regions, particularly in the left atrial appendage. The increased number of fibroblasts could be a mediator of altered electrophysiology during AF. Targeting the fibroblast proliferation and differentiation could potentially serve as a novel therapeutic target slowing down the structural remodeling associated with AF.
© 2021 The Authors.
Publication Date: 2021-07-20 PubMed ID: 34355058PubMed Central: PMC8322305DOI: 10.1016/j.ijcha.2021.100842Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research article investigates the structural changes and the role of fibroblasts, a type of cell that synthesizes the extracellular matrix, in equine hearts following persistent atrial fibrillation (AF), a common type of abnormal heart rhythm. Notably, the research emphasizes on the potential of fibroblast proliferation and differentiation as a novel therapeutic target for mitigating structural remodeling associated with AF.
Methods
- The researchers used an equine model and subjected eleven horses to atrial tachypacing until they developed self-sustained atrial fibrillation (AF); these horses were kept in this AF state for six weeks.
- Horses in sinus rhythm (SR) served as control subjects.
- In terminal open-chest experiments, conduction velocity, which measures the speed at which the heart’s electrical signals travel, was evaluated.
- Tissue samples were collected and stained from selected areas. An automated image analysis was then conducted to assess fibrosis (tissue scarring), fibroblasts (cells responsible for producing the extracellular matrix), capillaries, and various cardiomyocyte (heart muscle cell) characteristics.
Results
- Control horses in sinus rhythm demonstrated a rate-dependent slowing of the conduction velocity. However, this rate-dependency was entirely abolished in horses with persistent atrial fibrillation.
- While overall and interstitial amounts of fibrosis remained unchanged, an increased count of fibroblasts was noted in specific areas of the heart such as the left atrial appendage, Bachmann’s bundle, intraatrial septum, and pulmonary veins in horses with persistent AF.
- The percentage of α-SMA expressing fibroblasts was the same between both groups.
Conclusions
- Persistent atrial fibrillation led to an accumulation of fibroblasts in several regions of the heart, primarily in the left atrial appendage.
- The study suggests that the increased number of fibroblasts could influence the altered electrophysiology observed during AF.
- Therefore, the researchers proposed that targeting fibroblast proliferation and differentiation, through new therapeutic strategies, could potentially slow down the structural changes associated with AF.
Cite This Article
APA
Saljic A, Friederike Fenner M, Winters J, Flethøj M, Eggert Eggertsen C, Carstensen H, Dalgas Nissen S, Melis Hesselkilde E, van Hunnik A, Schotten U, Sørensen U, Jespersen T, Verheule S, Buhl R.
(2021).
Increased fibroblast accumulation in the equine heart following persistent atrial fibrillation.
Int J Cardiol Heart Vasc, 35, 100842.
https://doi.org/10.1016/j.ijcha.2021.100842 Publication
Researcher Affiliations
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark.
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Grønnegårdsvej 7, 1870 Frederiksberg, Denmark.
- Department of Physiology, Maastricht University, Maastricht, Netherlands.
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark.
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark.
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
- Department of Physiology, Maastricht University, Maastricht, Netherlands.
- Department of Physiology, Maastricht University, Maastricht, Netherlands.
- Acesion Pharma ApS, Copenhagen, Denmark.
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
- Department of Physiology, Maastricht University, Maastricht, Netherlands.
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark.
Conflict of Interest Statement
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
References
This article includes 54 references
- Margulescu AD, Mont L. Persistent atrial fibrillation vs paroxysmal atrial fibrillation: differences in management.. Expert review of cardiovascular therapy 2017;15(8):601–618.
- Kirchhof P, Benussi S, Kotecha D, Ahlsson A, Atar D, Casadei B. 2016 ESC Guidelines for the Management of Atrial Fibrillation Developed in Collaboration With EACTS.. Revista espanola de cardiologia (English ed) 2017;70(1):50.
- Schotten U, Verheule S, Kirchhof P, Goette A. Pathophysiological mechanisms of atrial fibrillation: a translational appraisal.. Physiol. Rev. 2011;91(1):265–325.
- Poulet C, Künzel S, Büttner E, Lindner D, Westermann D, Ravens U. Altered physiological functions and ion currents in atrial fibroblasts from patients with chronic atrial fibrillation.. Physiological reports 2016;4(2).
- Thomsen MB, Calloe K. Human atrial fibroblasts and their contribution to supraventricular arrhythmia.. Physiological reports 2016;4(3).
- Camelliti P, Borg TK, Kohl P. Structural and functional characterisation of cardiac fibroblasts.. Cardiovasc. Res. 2005;65(1):40–51.
- Nattel S. Molecular and Cellular Mechanisms of Atrial Fibrosis in Atrial Fibrillation.. JACC Clinical electrophysiology 2017;3(5):425–435.
- Spach MS, Boineau JP. Microfibrosis produces electrical load variations due to loss of side-to-side cell connections: a major mechanism of structural heart disease arrhythmias.. Pacing and clinical electrophysiology : PACE 1997;20(2 Pt 2):397–413.
- Ausma J, van der Velden HM, Lenders MH, van Ankeren EP, Jongsma HJ, Ramaekers FC. Reverse structural and gap-junctional remodeling after prolonged atrial fibrillation in the goat.. Circulation 2003;107(15):2051–2058.
- Verheule S, Eckstein J, Linz D, Maesen B, Bidar E, Gharaviri A. Role of endo-epicardial dissociation of electrical activity and transmural conduction in the development of persistent atrial fibrillation.. Prog. Biophys. Mol. Biol. 2014;115(2–3):173–185.
- Schotten U, Ausma J, Stellbrink C, Sabatschus I, Vogel M, Frechen D. Cellular mechanisms of depressed atrial contractility in patients with chronic atrial fibrillation.. Circulation 2001;103(5):691–698.
- Lau DH, Linz D, Schotten U, Mahajan R, Sanders P, Kalman JM. Pathophysiology of Paroxysmal and Persistent Atrial Fibrillation: Rotors, Foci and Fibrosis.. Heart, lung & circulation 2017;26(9):887–893.
- Souders CA, Bowers SL, Baudino TA. Cardiac fibroblast: the renaissance cell.. Circ. Res. 2009;105(12):1164–1176.
- Johnson RD, Camelliti P. Role of Non-Myocyte Gap Junctions and Connexin Hemichannels in Cardiovascular Health and Disease: Novel Therapeutic Targets?. International journal of molecular sciences 2018;19(3).
- Chacar S, Farès N, Bois P, Faivre JF. Basic Signaling in Cardiac Fibroblasts.. J. Cell. Physiol. 2017;232(4):725–730.
- Pellman J, Zhang J, Sheikh F. Myocyte-fibroblast communication in cardiac fibrosis and arrhythmias: Mechanisms and model systems.. J. Mol. Cell. Cardiol. 2016;94:22–31.
- Sanchez J, Gomez JF, Martinez-Mateu L, Romero L, Saiz J, Trenor B. Heterogeneous Effects of Fibroblast-Myocyte Coupling in Different Regions of the Human Atria Under Conditions of Atrial Fibrillation.. Front. Physiol. 2019;10:847.
- Haugaard MM, Pehrson S, Carstensen H, Flethøj M, Hesselkilde EZ, Praestegaard KF. Antiarrhythmic and electrophysiologic effects of flecainide on acutely induced atrial fibrillation in healthy horses.. J. Vet. Intern. Med. 2015;29(1):339–347.
- Haugaard MM, Hesselkilde EZ, Pehrson S, Carstensen H, Flethøj M, Præstegaard KF. Pharmacologic inhibition of small-conductance calcium-activated potassium (SK) channels by NS8593 reveals atrial antiarrhythmic potential in horses.. Heart rhythm 2015;12(4):825–835.
- Hesselkilde EZ, Carstensen H, Haugaard MM, Carlson J, Pehrson S, Jespersen T. Effect of flecainide on atrial fibrillatory rate in a large animal model with induced atrial fibrillation.. BMC cardiovascular disorders 2017;17(1):289.
- Vernemmen I, De Clercq D, Decloedt A, Vera L, Van Steenkiste G, van Loon G. Atrial premature depolarisations five days post electrical cardioversion are related to atrial fibrillation recurrence risk in horses.. Equine Vet. J. 2020;52(3):374–378.
- Hesselkilde EZ, Carstensen H, Flethøj M, Fenner M, Kruse DD, Sattler SM. Longitudinal study of electrical, functional and structural remodelling in an equine model of atrial fibrillation.. BMC cardiovascular disorders 2019;19(1):228.
- Buhl R, Nissen SD, Winther MLK, Poulsen SK, Hopster-Iversen C, Jespersen T. Implantable loop recorders can detect paroxysmal atrial fibrillation in Standardbred racehorses with intermittent poor performance.. Equine Vet. J. 2020.
- Leroux AA, Detilleux J, Sandersen CF, Borde L, Houben RM, Al Haidar A. Prevalence and risk factors for cardiac diseases in a hospital-based population of 3,434 horses (1994–2011). J. Vet. Intern. Med. 2013;27(6):1563–1570.
- Physick-Sheard P, Kraus M, Basrur P, McGurrin K, Kenney D, Schenkel F. Breed predisposition and heritability of atrial fibrillation in the Standardbred horse: a retrospective case-control study.. Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology 2014;16(3):173–184.
- Saljic A, Jespersen T, Buhl R. Anti-arrhythmic investigations in large animal models of atrial fibrillation.. Br. J. Pharmacol. 2021.
- Linz D, Hesselkilde E, Kutieleh R, Jespersen T, Buhl R, Sanders P. Pulmonary vein firing initiating atrial fibrillation in the horse: Oversized dimensions but similar mechanisms.. J. Cardiovasc. Electrophysiol. 2020;31(5):1211–1212.
- Fenner MF, Carstensen H, Nissen SD, Hesselkilde EZ, Lunddahl C, Jensen MA. Effect of Selective I(K, ACh) Inhibition by XAF-1407 in an Equine Model of Tachypacing-induced Persistent Atrial Fibrillation (AF). Br. J. Pharmacol. 2020.
- Adler DMT, Hopster K, Hopster-Iversen C, Fenner M, Buhl R, Jacobsen S. Thoracotomy and Pericardiotomy for Access to the Heart in Horses: Surgical Procedure and Effects on Anesthetic Variables.. Journal of equine veterinary science 2021;96.
- Winters J, von Braunmuhl ME, Zeemering S, Gilbers M, Brink TT, Scaf B. JavaCyte, a novel open-source tool for automated quantification of key hallmarks of cardiac structural remodeling.. Sci. Rep. 2020;10(1):20074.
- Xie Y, Garfinkel A, Camelliti P, Kohl P, Weiss JN, Qu Z. Effects of fibroblast-myocyte coupling on cardiac conduction and vulnerability to reentry: A computational study.. Heart rhythm 2009;6(11):1641–1649.
- Allessie M, Ausma J, Schotten U. Electrical, contractile and structural remodeling during atrial fibrillation.. Cardiovasc. Res. 2002;54(2):230–246.
- Ausma J, Wijffels M, Thoné F, Wouters L, Allessie M, Borgers M. Structural changes of atrial myocardium due to sustained atrial fibrillation in the goat.. Circulation 1997;96(9):3157–3163.
- Yue L, Feng J, Gaspo R, Li GR, Wang Z, Nattel S. Ionic remodeling underlying action potential changes in a canine model of atrial fibrillation.. Circ. Res. 1997;81(4):512–525.
- Kato T, Iwasaki YK, Nattel S. Connexins and atrial fibrillation: filling in the gaps.. Circulation 2012;125(2):203–206.
- Yue L, Xie J, Nattel S. Molecular determinants of cardiac fibroblast electrical function and therapeutic implications for atrial fibrillation.. Cardiovasc. Res. 2011;89(4):744–753.
- Burstein B, Libby E, Calderone A, Nattel S. Differential behaviors of atrial versus ventricular fibroblasts: a potential role for platelet-derived growth factor in atrial-ventricular remodeling differences.. Circulation 2008;117(13):1630–1641.
- Massagué J. How cells read TGF-beta signals.. Nat. Rev. Mol. Cell Biol. 2000;1(3):169–178.
- Olson ER, Shamhart PE, Naugle JE, Meszaros JG. Angiotensin II-induced extracellular signal-regulated kinase 1/2 activation is mediated by protein kinase Cdelta and intracellular calcium in adult rat cardiac fibroblasts.. Hypertension (Dallas, Tex : 1979) 2008;51(3):704-11.
- Ramires FJ, Sun Y, Weber KT. Myocardial fibrosis associated with aldosterone or angiotensin II administration: attenuation by calcium channel blockade.. J. Mol. Cell. Cardiol. 1998;30(3):475–483.
- Du J, Xie J, Zhang Z, Tsujikawa H, Fusco D, Silverman D. TRPM7-mediated Ca2+ signals confer fibrogenesis in human atrial fibrillation.. Circ. Res. 2010;106(5):992–1003.
- Krenning G, Zeisberg EM, Kalluri R. The origin of fibroblasts and mechanism of cardiac fibrosis.. J. Cell. Physiol. 2010;225(3):631–637.
- Freestone B, Chong AY, Lim HS, Blann A, Lip GY. Angiogenic factors in atrial fibrillation: a possible role in thrombogenesis?. Ann. Med. 2005;37(5):365–372.
- Chung NA, Belgore F, Li-Saw-Hee FL, Conway DS, Blann AD, Lip GY. Is the hypercoagulable state in atrial fibrillation mediated by vascular endothelial growth factor?. Stroke 2002;33(9):2187–2191.
- Seko Y, Nishimura H, Takahashi N, Ashida T, Nagai R. Serum levels of vascular endothelial growth factor and transforming growth factor-beta1 in patients with atrial fibrillation undergoing defibrillation therapy.. Jpn. Heart J. 2000;41(1):27–32.
- Citerni C, Kirchhoff J, Olsen LH, Sattler SM, Gentilini F, Forni M. Characterization of Atrial and Ventricular Structural Remodeling in a Porcine Model of Atrial Fibrillation Induced by Atrial Tachypacing.. Frontiers in veterinary science 2020;7:179.
- Gramley F, Lorenzen J, Jedamzik B, Gatter K, Koellensperger E, Munzel T. Atrial fibrillation is associated with cardiac hypoxia.. Cardiovascular pathology : the official journal of the Society for Cardiovascular Pathology 2010;19(2):102–111.
- Olasinska-Wisniewska A, Mularek-Kubzdela T, Grajek S, Marszalek A, Sarnowski W, Jemielity M. Impact of atrial remodeling on heart rhythm after radiofrequency ablation and mitral valve operations.. The Annals of thoracic surgery 2012;93(5):1449–1455.
- Corradi D, Callegari S, Maestri R, Benussi S, Bosio S, De Palma G. Heme oxygenase-1 expression in the left atrial myocardium of patients with chronic atrial fibrillation related to mitral valve disease: its regional relationship with structural remodeling.. Hum. Pathol. 2008;39(8):1162–1171.
- Corradi D, Callegari S, Maestri R, Ferrara D, Mangieri D, Alinovi R. Differential structural remodeling of the left-atrial posterior wall in patients affected by mitral regurgitation with or without persistent atrial fibrillation: a morphological and molecular study.. J. Cardiovasc. Electrophysiol. 2012;23(3):271–279.
- Boldt A, Scholl A, Garbade J, Resetar ME, Mohr FW, Gummert JF. ACE-inhibitor treatment attenuates atrial structural remodeling in patients with lone chronic atrial fibrillation.. Basic Res. Cardiol. 2006;101(3):261–267.
- Opacic D, van Bragt KA, Nasrallah HM, Schotten U, Verheule S. Atrial metabolism and tissue perfusion as determinants of electrical and structural remodelling in atrial fibrillation.. Cardiovasc. Res. 2016;109(4):527–541.
- Scridon A, Morel E, Nonin-Babary E, Girerd N, Fernandez C, Chevalier P. Increased intracardiac vascular endothelial growth factor levels in patients with paroxysmal, but not persistent atrial fibrillation.. Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology 2012;14(7):948–953.
- Hassink RJ, Aretz HT, Ruskin J, Keane D. Morphology of atrial myocardium in human pulmonary veins: a postmortem analysis in patients with and without atrial fibrillation.. J. Am. Coll. Cardiol. 2003;42(6):1108–1114.
Citations
This article has been cited 11 times.- Medina-Contreras JML, Balderas-Villalobos J, Gomez-Arroyo J, Hayles J, Kaszala K, Tan AY, Samsó M, Huizar JF, Eltit JM. High Burden of Premature Ventricular Contractions Upregulates Transcriptional Markers of Inflammation and Promotes Adverse Cardiac Remodeling Linked to Cardiomyopathy. Circ Arrhythm Electrophysiol 2026 Jan;19(1):e014195.
- Haugaard SL, Schneider MJ, Kjeldsen ST, Sattler SM, Bastrup JA, Saljic A, Birk JB, Hansen C, Synnestvedt JN, van Hunnik A, Sobota V, Carstensen H, Hopster-Iversen C, Schwarzwald CC, Altintaş A, Barrès R, Jepps TA, Larsen S, Kjøbsted R, Wojtaszewski JFP, Barrado Ballestero S, Roostalu U, Herum KM, Jespersen T, Nattel S, Nissen SD, Buhl R. Metformin Protects Against Persistent Atrial Fibrillation in an Equine Model. Circ Arrhythm Electrophysiol 2025 Dec;18(12):e013850.
- Nissen SD, Bastrup JA, Haugaard SL, Marion-Knudsen R, Schneider M, Kjeldsen ST, Carstensen H, Hopster-Iversen C, Nattel S, Jepps TA, Buhl R. Horse model of spontaneous atrial fibrillation share proteomic changes with humans. Sci Rep 2025 Aug 28;15(1):31694.
- Medina-Contreras JML, Balderas-Villalobos J, Gomez-Arroyo J, Hayles J, Kaszala K, Tan AY, Samsó M, Huizar JF, Eltit JM. High burden of premature ventricular contractions upregulates transcriptional markers of inflammation and promotes adverse cardiac remodeling linked to cardiomyopathy. bioRxiv 2025 May 28;.
- Nath LC, Saljic A, Buhl R, Elliott A, La Gerche A, Ye C, Schmidt Royal H, Lundgren Virklund K, Agbaedeng TA, Stent A, Franklin S. Histological evaluation of cardiac remodelling in equine athletes. Sci Rep 2024 Jul 19;14(1):16709.
- Nissen SD, Saljic A, Carstensen H, Braunstein TH, Hesselkilde EM, Kjeldsen ST, Hopster-Iversen C, D'Souza A, Jespersen T, Buhl R. Muscarinic acetylcholine receptors M(2) are upregulated in the atrioventricular nodal tract in horses with a high burden of second-degree atrioventricular block. Front Cardiovasc Med 2023;10:1102164.
- Fender AC, Dobrev D. Recent highlights on the mechanistic basis of cardiovascular remodeling from the International Journal of Cardiology Heart & Vasculature. Int J Cardiol Heart Vasc 2023 Aug;47:101248.
- Nissen SD, Saljic A, Kjeldsen ST, Jespersen T, Hopster-Iversen C, Buhl R. Cartilaginous Intrusion of the Atrioventricular Node in a Quarter Horse with a High Burden of Second-Degree AV Block and Collapse: A Case Report. Animals (Basel) 2022 Oct 24;12(21).
- Wang L, Fan J, Wang Z, Liao Y, Zhou B, Ma C. Evaluating left atrial appendage function in a subtype of non-valvular atrial fibrillation using transesophageal echocardiography combined with two-dimensional speckle tracking. Quant Imaging Med Surg 2022 May;12(5):2721-2731.
- Kjeldsen ST, Nissen SD, Buhl R, Hopster-Iversen C. Paroxysmal Atrial Fibrillation in Horses: Pathophysiology, Diagnostics and Clinical Aspects. Animals (Basel) 2022 Mar 10;12(6).
- Sánchez J, Trenor B, Saiz J, Dössel O, Loewe A. Fibrotic Remodeling during Persistent Atrial Fibrillation: In Silico Investigation of the Role of Calcium for Human Atrial Myofibroblast Electrophysiology. Cells 2021 Oct 22;10(11).
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists