Remodeling of the peripheral cardiac conduction system in response to pressure overload.
How chronic pressure overload affects the Purkinje fibers of the ventricular peripheral conduction system (PCS) is not known. Here, we used a connexin (Cx)40 knockout/enhanced green fluorescent protein knockin transgenic mouse model to specifically label the PCS. We hypothesized that the subendocardially located PCS would remodel after chronic pressure overload and therefore analyzed cell size, markers of hypertrophy, and PCS-specific Cx and ion channel expression patterns. Left ventricular hypertrophy with preserved systolic function was induced by 30 days of surgical transaortic constriction. After transaortic constriction, we observed that PCS cardiomyocytes hypertrophied by 23% (P < 0.05) and that microdissected PCS tissue exhibited upregulated markers of hypertrophy. PCS cardiomyocytes showed a 98% increase in the number of Cx40-positive gap junction particles, with an associated twofold increase in gene expression (P < 0.05). We also identified a 50% reduction in Cx43 gap junction particles located at the interface between PCS cardiomyocytes and the working cardiomyocyte. In addition, we measured a fourfold increase of an ion channel, hyperpolarization-activated cyclic nucleotide-gated channel (HCN)4, throughout the PCS (P < 0.05). As a direct consequence of PCS remodeling, we found that pressure-overloaded hearts exhibited marked changes in ventricular activation patterns during normal sinus rhythm. These novel findings characterize PCS cardiomyocyte remodeling after chronic pressure overload. We identified significant hypertrophic growth accompanied by modified expression of Cx40, Cx43, and HCN4 within PCS cardiomyocytes. We found that a functional outcome of these changes is a failure of the PCS to activate the ventricular myocardium normally. Our findings provide a proof of concept that pressure overload induces specific cellular changes, not just within the working myocardium but also within the specialized PCS.
Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA. harrisbs@musc.edu
Brett S
BS
Harris
Catalin F
CF
Baicu
Nicole
N
Haghshenas
Harinath
H
Kasiganesan
Dimitri
D
Scholz
Mary S
MS
Rackley
Lucile
L
Miquerol
Daniel
D
Gros
Rupak
R
Mukherjee
Terrence X
TX
O'Brien
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D015153:Blotting, Western; D006332:Cardiomegaly / Q000235:genetics / Q000503:physiopathology; D002452:Cell Count; D048429:Cell Size; D017630:Connexins / Q000235:genetics / Q000502:physiology; D003250:Constriction; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics / Q000502:physiology; D004452:Echocardiography; D004562:Electrocardiography; D066246:ErbB Receptors / Q000235:genetics / Q000502:physiology; D005260:Female; D005455:Fluorescent Antibody Technique; D006329:Heart Conduction System / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007091:Image Processing, Computer-Assisted; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000502:physiology / Q000648:ultrastructure; D011312:Pressure; D011690:Purkinje Fibers / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction; D020257:Ventricular Remodeling; D000097003:Gap Junction alpha-5 Protein
D017630:Connexins; D054815:Cyclic Nucleotide-Gated Cation Channels; D066246:ErbB Receptors; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D000097003:Gap Junction alpha-5 Protein; C541485:EGFR protein, mouse