Cardiac Fibro-Adipocyte Progenitors Express Desmosome Proteins and Preferentially Differentiate to Adipocytes Upon Deletion of the Desmoplakin Gene

Abstract

Rationale Mutations in desmosome proteins cause arrhythmogenic cardiomyopathy (AC), a disease characterized by excess myocardial fibro-adipocytes. Cellular origin(s) of fibro-adipocytes in AC is unknown. Objective To identify the cellular origin of adipocytes in AC. Methods and Results Human and mouse cardiac cells were depleted from myocytes and flow sorted to isolate cells expressing platelet-derived growth factor receptor A (PDGFRA) and exclude those expressing other lineage and fibroblast markers (CD32, CD11B, CD45, Lys76, Ly−6c and Ly6c, THY1, and DDR2). The PDGFRApos:Linneg:THY1neg:DDR2neg cells were bipotential, as the majority expressed COL1A1, a fibroblast marker, and a subset CEBPA, a major adipogenic transcription factor, and therefore, were referred to as fibro-adipogenic progenitors (FAPs). FAPs expressed desmosome proteins including desmoplakin (DSP), predominantly in the adipogenic but not fibrogenic subsets. Conditional heterozygous deletion of Dsp in mouse using Pdgfra-Cre deleter led to increased fibro-adipogenesis in the heart and mild cardiac dysfunction. Genetic fate mapping tagged 41.4±4.1% of the cardiac adipocytes in the Pdgfra-Cre:Eyfp:DspW/F mice, indicating an origin from FAPs. FAPs isolated from the Pdgfra-Cre:Eyfp:DspW/F mouse hearts showed enhanced differentiation to adipocytes. Mechanistically, deletion of Dsp was associated with suppressed canonical Wnt signaling and enhanced adipogenesis. In contrast, activation of the canonical Wnt signaling rescued adipogenesis in a dose-dependent manner. Conclusions A subset of cardiac FAPs, identified by the PDGFRApos:Linneg:THY1neg:DDR2neg signature, expresses desmosome proteins and differentiates to adipocyte in AC through a Wnt-dependent mechanism. The findings expand the cellular spectrum of AC, commonly recognized as a disease of cardiac myocytes, to include non-myocyte cells in the heart.

Healthy and Unhealthy Cardiac Progenitor Cells Modify the Pathogenesis of Myocardial Diseases

“…The activation of the Wnt signaling reduced adipogenesis and normalized transcript levels of adipogenic genes. 6 This elegant study demonstrates the presence of the PDGFRA + FAPs in the adult mammalian heart and the importance of the desmoplakin gene mutation in these progenitor cells for the replacement of the myocardium with the fibrofatty tissue.…”

“…By crossing of PDGFRA + -EGFP mice with the Myh6-Cre:DspW/F mouse model of ARVD/C, the authors show that the mutation of desmoplakin in FAPs causes the formation of fibrofatty tissue leading to ARVD/C. 6 An interesting finding of the fat-mapping experiments is the expression of PDGFRA + locus by ≈20% cardiomyocytes during cardiac development. In the murine embryo, PDGFRA is expressed in the early mesoderm, including cardiac mesoderm and in cardiac neural crest directing the differentiation, migration, and function of stem and progenitor cells during embryonic organogenesis.…”

Distinct Cellular Basis for Early Cardiac Arrhythmias, the Cardinal Manifestation of Arrhythmogenic Cardiomyopathy, and the Skin Phenotype of Cardiocutaneous Syndromes

“…18, 20, 28 Custom-made and commercially available antibodies were used to detect expression of the proteins of interest, including CSPG4 and DSP in isolated cardiac myocytes, non-myocyte cardiac cells, and myocardial sections (Online Table I). …”

“…20 The tissue samples were digested with collagenase, filtered through a 40 μm cell strainer, and the cells were precipitated by centrifugation. The pelleted cells were re-suspended in a complete medium in the presence of antibiotics, and plated on plates coated with 0.1% gelatin.…”

“…They are also expressed, albeit at lower levels in the non-myocyte cardiac cells, such as the mesenchymal cells and fibro-adipocyte progenitors (FAPs). 20, 21 Cells expressing the mutant desmosome proteins, whether myocytes or non-myocyte cells, are expected to be involved in the pathogenesis of ACM. 20, 21 …”