Phospholamban immunostaining is a highly sensitive and specific method for diagnosing phospholamban p.Arg14del cardiomyopathy

Phospholamban (PLN) p.Arg14del cardiomyopathy is associated with an increased risk of malignant ventricular arrhythmias and severe heart failure and a poor prognosis from late adolescence. It can be diagnosed in whole heart specimens, but rarely in right ventricular biopsy specimens, by PLN immunohistochemistry showing PLN-containing aggregates concentrated in cardiomyocytes in dense perinuclear aggresomes. The purpose of this study was to determine whether PLN immunohistochemistry can be used to diagnose PLN p.Arg14del cardiomyopathy using apical left ventricular myocardial specimens harvested during left ventricular assist device (LVAD) implantation. At that stage, a genetic diagnosis, which may guide treatment and referral of family members for further investigation, is frequently not established yet. Included were myocardial specimens from 30 diverse genetic cardiomyopathy cases with known variants (9 carriers of the pathogenic PLN p.Arg14del variant, 18 cases with other pathogenic or likely pathogenic variants in cardiomyopathy-related genes, and 3 with only variants of unknown significance). Immunohistochemical analysis revealed typical dense perinuclear globular PLN-positive aggregates, representing aggresomes, in all nine PLN p.Arg14del cases. In 20 non-PLN cases, PLN-staining was absent. In one non-PLN case, one of the two independent observers misinterpreted PLN staining of heavily wrinkled nuclear membranes of cardiomyocytes as perinuclear PLN aggregates. In this genetic cardiomyopathy cohort, PLN Immunohistochemical analysis in LVAD biopsies was found to be a highly sensitive (100%) and specific (95%) method for demonstration of PLN protein aggregates in PLN p.Arg14del cardiomyopathy. In clinical practice, PLN immunohistochemical analysis of LVAD specimens can be of incremental value in the diagnostic workup of this cardiomyopathy, even more so if genetic analysis is not readily available

P62-positive aggregates are homogenously distributed in the myocardium and associated with the type of mutation in genetic cardiomyopathy

© 2021 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd Genetic cardiomyopathy is caused by mutations in various genes. The accumulation of potentially proteotoxic mutant protein aggregates due to insufficient autophagy is a possible mechanism of disease development. The objective of this study was to investigate the distribution in the myocardium of such aggregates in relation to specific pathogenic genetic mutations in cardiomyopathy hearts. Hearts from 32 genetic cardiomyopathy patients, 4 non-genetic cardiomyopathy patients and 5 controls were studied. Microscopic slices from an entire midventricular heart slice were stained for p62 (sequestosome-1, marker for aggregated proteins destined for autophagy). The percentage of cardiomyocytes with p62 accumulation was higher in cardiomyopathy hearts (median 3.3%) than in healthy controls (0.3%; P <.0001). p62 accumulation was highest in the desmin (15.6%) and phospholamban (7.2%) groups. P62 accumulation was homogeneously distributed in the myocardium. Fibrosis was not associated with p62 accumulation in subgroup analysis of phospholamban hearts. In conclusion, accumulation of p62-positive protein aggregates is homogeneously distributed in the myocardium independently of fibrosis distribution and associated with desmin and phospholamban cardiomyopathy. Proteotoxic protein accumulation is a diffuse process in the myocardium while a more localized second hit, such as local strain during exercise, might determine whether this leads to regional myocyte decay