Abstract 14695: Ultrastructural Abnormalities in the Absence of Structural Cardiomyopathy in Plakophilin-2 Deficient Mice
Most cases of familial arrhythmogenic cardiomyopathy (AC) result from mutations in desmosomal proteins. Desmosomes are structural components of the cardiac intercalated disc, and can be visualized by electron microscopy. An early report showed that in a patient with desmosomal mutations, ultrastructural defects and electrical dysfunction preceded the onset of myocardial loss and fibrofatty infiltration, but a complete characterization was not possible. Other studies have characterized the ultrastructure of the intercalated disc in human and canine hearts affected with AC, and in murine models of desmosomal deficiency, but those observations were conducted in hearts already displaying histological and anatomical features of the disease. Here, we characterized the ultrastructural consequences of desmosomal protein deficiency in hearts that do not display overt structural disease. We combined advanced methods of tissue preservation (high-pressure freezing), data acquisition (electron tomography) and image processing (segmentation analysis and quantification). Thin sections of adult mouse ventricular tissue from control and from mice heterozygous-null for PKP2 (PKP2-Hz) were collected and imaged, and their tomograms reconstructed. Image stacks were analyzed in a 2D XY projection and in 3D. We observed a reduction in gap junction length (from 1093.92 ± 164.93 nm to 446.99 ± 80.99 nm), increased intercellular spacing in the vicinity of the gap junction (from 18.63 ± 1.14 nm to 24.22 ± 2.47 nm), increased separation between gap junctions and desmosomes (from 299.68 ± 51.07 nm to 1289.07 ± 351.36 nm), a doubling of intercalated disc surface area and an increase by a factor of 1.8 in membrane tortuosity in the samples from PKP2-Hz hearts. This is, to our knowledge, the first detailed characterization of the ultrastructural defects associated with desmosomal deficiency in the absence of overt structural changes. These defects parallel changes in structure/function of macromolecular complexes of the intercalated disc, in particular sodium channel and connexins and can serve as substrates for the occurrence of lethal arrhythmias in the absence of clinically detectable disease.
Author Disclosures: A. Leo-Macias: None. A. Gutierrez: None. F. Liang: None. M. Delmar: None.
This research has received full or partial funding support from the American Heart Association.
- © 2014 by American Heart Association, Inc.