Winning Abstracts from the 2012 Medical Student Abstract Competition: Connexin 40 Remodeling In Purkinje Cardiomyocytes Post-myocardial Infarction
Author: Satara A. Brown, Medical University of South Carolina, Class of 2014
Introduction: Purkinje cardiomyocytes are specialized cardiomyoctes that connect to working cardiomyocytes to facilitate contraction of the heart muscle. Connexin 40 (Cx40) is the predominant connexin found in gap junctions of Purkinje cardiomyocytes; however, Cx43 and Cx45 are predominant in working cardiomyocytes. In working cardiomyocytes following myocardial infarction (MI), Cx43 remodeling occurs, which is indicated by lateralization of Cx43 and ensuing arrhythmias. We hypothesize that in murine Purkinje cardiomyocytes, MI will cause disorganization of Cx40 expression at gap junctions.
Methods: A Cx40EGFP/+ transgenic mouse model post-surgical ligation of the left anterior descending artery was utilized to conduct this study. EGFP, enhanced green fluorescence protein, allowed identification of Purkinje cardiomyocytes. Antibodies to detect pan-cadherin and Cx40 were used in immunofluorescence staining of tissues. Immunofluorescence and confocal microscopy were employed to image gap junctions and intercalated disks in EGFP areas. Differences in Cx40 expression, cadherin expression, and colocalization of Cx40 and cadherin in control mice and mice that have experienced MI were quantified.
Results: Cx40 remodeling was indicated by decreased Cx40 expression, decreased cadherin expression, and decreased colocalization of Cx40 and cadherin in the Purkinje cell areas. Cx40 expression decreased by 56%, cadherin expression decreased by 69%, and colocalization decreased by 24%. This indicated that gap junctions were deficient and relocated from their normal locations at intercalated disks following MI.
Conclusion: These results parallel changes that have been detected with Cx43 expression in working cardiomyocytes. Alterations in Cx40 in Purkinje cells may be responsible for life-threatening arrhythmias that can occur post-MI. These findings in the mouse model can be used to develop a treatment for post-MI arrhythmias in humans in the future
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