Studying arrhythmogenic right ventricular dysplasia with patient-specific iPSCs

Abstract

Cellular reprogramming of somatic cells to patient-specific induced pluripotent stem cells (iPSCs) enables in-vitro modelling of human genetic disorders for pathogenic investigations and therapeutic screens1–7. However, using iPSC-derived cardiomyocytes (iPSC-CMs) to model an adult-onset heart disease remains challenging due to the uncertainty regarding the ability of relatively immature iPSC-CMs to fully recapitulate adult disease phenotypes. Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an inherited heart disease characterized by pathological fatty infiltration and cardiomyocyte loss predominantly in the right ventricle (RV)8, which is associated with life-threatening ventricular arrhythmias. Over 50% of affected individuals have desmosome gene mutations, most commonly in PKP2 encoding plakophilin-29. The median age at presentation of ARVD/C is 26 years8. We used Yamanaka’s methods1,10 to generate iPSC lines from fibroblasts of two patients with ARVD/C and PKP2 mutations11,12. Mutant PKP2 iPSC-CMs demonstrate abnormal plakoglobin nuclear translocation and decreased β-catenin activity13 in cardiogenic conditions; yet these abnormal features are insufficient to reproduce the pathological phenotypes of ARVD/C in standard cardiogenic conditions. Here we show that induction of adult-like metabolic energetics from an embryonic/glycolytic state and abnormal peroxisome proliferator-activated receptor-gamma (PPARγ) activation underlie the pathogenesis of ARVD/C. By coactivating normal PPAR-alpha (PPARα)-dependent metabolism and abnormal PPARγ pathway in beating embryoid bodies (EBs) with defined media, we established an efficient ARVD/C in-vitro model within two months. This model manifests exaggerated lipogenesis and apoptosis in mutant PKP2 iPSC-CMs. iPSC-CMs with a homozygous PKP2 mutation also displayed calcium-handling deficits. Our study is the first to demonstrate that induction of adult-like metabolism plays a critical role in establishing an adult-onset disease model using patient-specific iPSCs. Using this model, we revealed crucial pathogenic insights that metabolic derangement in adult-like metabolic milieu underlies ARVD/C pathologies, enabling us to propose novel disease-modifying therapeutic strategies.

iASPP, a previously unidentified regulator of desmosomes, prevents arrhythmogenic right ventricular cardiomyopathy (ARVC)-induced sudden death

“…Although the fatty infiltration was not extensive in iASPP Δ8/Δ8 hearts, it was undetectable in wild-type controls. Recently it has been suggested that PPARγ activation is important in adipogenesis and ARVC pathogenesis (38). We observed a clear increase in the protein levels of PPARγ and its target gene adiponectin in hearts from iASPP-deficient mice compared with wild-type control hearts (Fig.…”

“…S6B). PPARγ signaling previously has been implicated in adipogenesis in ARVC (38,46), and its activation also was present in iASPP-deficient hearts (Fig. S6C).…”

Inherited heart disease – what can we expect from the second decade of human iPS cell research?

“…Importantly, the human heart is composed not only of CMs but also vascular, smooth muscle and epicardial cells; to better mimic its function, we predict that 3D cardiac tissue structures will be widely implemented, especially where interactions between different cell types might underlie the disease. As an example, ARVC has been modelled in hiPSC‐CMs and these are the major cellular players in the cardiac dysfunction in this disease 30, 34, 73; however, the suspected contribution of epicardial cells to fibro‐fatty substitution and the role of inflammation could not so far be studied in two‐dimensional monotypic cultures. The expectation is that complex multicellar structures will be necessary to reflect fully the pathology of the condition.…”

Human pluripotent stem cell-derived cardiomyocyte based models for cardiotoxicity and drug discovery

“…Generating 3D micro ECTs of variable cell compositions, using human-derived cardiac cells, has been demonstrated as discussed. Moreover, varying degrees of hPSC-CM maturation have been demonstrated by means of prolonged culture [26], topographical cues [14], electrical stimulation [14], mechanical stretching [19], and/or chemical manipulation [27], as well as coculture with cardiac fibroblasts [28] and endothelial cells [25]. Yet, there are currently no robust methods of promoting the functional maturation of hPSC-CMs within a short time frame.…”

“…Alternatively, 3D micro ECTs have been generated by seeding cardiac cells suspended in a hydrogel in a platform wherein they self-organize around a pair of posts (Figure 1(d, e)) [25]. The post platform both induces alignment within the 3D ECT (Figure 1(f)) due to the static stretch applied by the posts and provides a means of directly measuring the contractility of the ECT in situ.…”