Nuclear plakoglobin is essential for differentiation of cardiac progenitor cells to adipocytes in arrhythmogenic right ventricular cardiomyopathy

Rationale: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disease of desmosome proteins characterized by fibroadipogenesis in the myocardium. We have implicated signaling properties of junction protein plakoglobin (PG) in the pathogenesis of ARVC. Objective: To delineate the pathogenic role of PG in adipogenesis in ARVC. Methods and Results: We generated mice overexpressing PG, either a wildtype (PG WT) or a truncated (PG TR), known to cause ARVC, in the heart; and PG null (PG -/-) embryos. PG WT and PG TR mice exhibited fibro-adiposis, cardiac dysfunction, and premature death. Subcellular protein fractionation and immunofluorescence showed nuclear localization of PG WT and PG TR and reduced membrane localization of PG TR. Coimmunoprecipitation showed reduced binding of PG TR but not PG WT to desmosome proteins DSP and DSG2. Transgene PG WT and PG TR were expressed in c-Kit +:Sca1 + cardiac progenitor cells (CPCs) isolated from the hearts of PG WT and PG TR by fluorescence activated cell sorting. CPCs isolated from the transgenic hearts showed enhanced adipogenesis, increased levels of adipogenic factors KLF15, C/EBP-α and noncanonical Wnt5b, and reduced level of CTGF, an inhibitor of adipogenesis. Treatment with BIO activated the canonical Wnt signaling, reversed the proadipogenic transcriptional switch and prevented adipogenesis in a dose-dependent manner. Moreover, c-Kit + CPCs, isolated from PG -/- embryos, were resistant to adipogenesis, expressed high mRNA levels of CTGF and other canonical Wnt signaling targets. Conclusions: Nuclear PG provokes adipogenesis in c-Kit + CPCs by repressing the canonical Wnt signaling and inducing a proadipogenic gene expression. The findings suggest that adipocytes in ARVC, at least in part, originate from c-Kit + CPCs. © 2011 American Heart Association, Inc

Detailed analysis of bone marrow from patients with ischemic heart disease and left ventricular dysfunction: BM CD34, CD11b, and clonogenic capacity as biomarkers for clinical outcomes

Bone marrow (BM) cell therapy for ischemic heart disease (IHD) has shown mixed results. Before the full potency of BM cell therapy can be realized, it is essential to understand the BM niche after acute myocardial infarction (AMI). To study the BM composition in patients with IHD and severe left ventricular (LV) dysfunction. BM from 280 patients with IHD and LV dysfunction were analyzed for cell subsets by flow cytometry and colony assays. BM CD34(+) cell percentage was decreased 7 days after AMI (mean of 1.9% versus 2.3%-2.7% in other cohorts; P<0.05). BM-derived endothelial colonies were significantly decreased (P<0.05). Increased BM CD11b(+) cells associated with worse LV ejection fraction (LVEF) after AMI (P<0.05). Increased BM CD34(+) percentage associated with greater improvement in LVEF (+9.9% versus +2.3%; P=0.03, for patients with AMI and +6.6% versus -0.02%; P=0.021 for patients with chronic IHD). In addition, decreased BM CD34(+) percentage in patients with chronic IHD correlated with decrement in LVEF (-2.9% versus +0.7%; P=0.0355). In this study, we show a heterogeneous mixture of BM cell subsets, decreased endothelial colony capacity, a CD34+ cell nadir 7 days after AMI, a negative correlation between CD11b percentage and postinfarct LVEF, and positive correlation of CD34 percentage with change in LVEF after cell therapy. These results serve as a possible basis for the small clinical improvement seen in autologous BM cell therapy trials and support selection of potent cell subsets and reversal of comorbid BM impairment. http://www.clinicaltrials.gov. Unique identifiers: NCT00684021, NCT00684060, and NCT00824005