Arrhythmogenic cardiomyopathy (ACM) is predominantly caused by mutations in genes encoding desmosomal proteins (such as plakophilin-2), however also mutations in non-desmosomal proteins like phospholamban (PLN) are found. Previous research showed that plakoglobin protein levels and localization in cardiac tissue of ACM patients is disturbed and this could be an additional tool to discriminate between non-affected family members and those being at risk of ACM. Information about plakoglobin status can only be obtained via endocardial biopsies, however, this technique has major drawbacks, and therefore an alternative is needed. A promising new non-invasive tool is the use of buccal mucosa cells (BMC), as it has been reported that effects of mutations in desmosomal proteins are reflected in non-cardiac tissues like BMC smears that do also express those desmosomal genes.
To investigate the clinical usability of BMC as tool to classify patients at risk of developing ACM by comparing controls with asymptomatic and symptomatic ACM patients, and patients carrying a PLN mutation.
BMC of 33 ACM patients (19 males, 28 with a PKP2 mutation), 17 PLN patients (6 males) and 34 controls (14 males), were collected on glass slides, fixed and labelled with anti-plakoglobin antibodies diluted 1:5.000, 1:10.000, 1:20.000 and 1:40.000, and scored for their membrane labelling.
Data revealed that for each dilution, plakoglobin protein levels at the membrane were significantly reduced in BMC obtained from ACM patients compared to controls. This effect was independent from age and sex of the patients. Dilutions 1:5.000 and 1:10.000 showed a moderate correlation with the revised 2010 Task Force Criteria Score (TFC) which are commonly used for ACM diagnosis (Rs -0.67, n=64, p <0.0001 and Rs -0.71, n=64, p<0.0001 resp.) In contrast, plakoglobin scores of PLN patients were similar to controls.
There is a significant reduction of plakoglobin protein in BMC of ACM patients but not for patients bearing the PLN mutation when compared to controls. However, for clinical diagnosis of the individual patient, this method is most likely not discriminative enough to distinguish patients from controls, because of high interindividual variability.
© 2021 Published by Elsevier Inc.