Human-Induced Pluripotent Stem Cell-Derived Cardiomyocyte Model for TNNT2 Δ160E-Induced Cardiomyopathy.

BACKGROUND: The Δ160E mutation in TNNT2, which encodes troponin T, is a rare pathogenic variant identified in patients with hypertrophic cardiomyopathy and is associated with poor prognosis. Thus, a convenient human model recapitulating the pathological phenotype caused by TNNT2 Δ160E is required for therapeutic development. METHODS: We identified a heterozygous in-frame deletion mutation (c.478_480del, p.Δ160E) in TNNT2 in a patient with familial hypertrophic cardiomyopathy showing progressive left ventricular systolic dysfunction, leading to advanced heart failure. To investigate the pathological phenotype caused by Δ160E, we generated a set of isogenic induced pluripotent stem cells carrying the heterozygous Δ160E, homozygously corrected or homozygously introduced Δ160E using genome editing and differentiated them into cardiomyocytes (Hetero-Δ160E-, wild type-, and Homo-Δ160E-induced pluripotent stem cells [iPSC]-derived cardiomyocytes [iPSC-CMs]). RESULTS: Hetero-Δ160E-iPSC-CMs exhibited prolonged calcium decay, relaxation impairment, and hypertrophy compared to wild type-iPSC-CMs. Notably, these phenotypes were further exacerbated in Homo-Δ160E-iPSC-CMs. Overexpression of R-GECO-fused Δ160E mutant troponin T prolonged decay time and time to peak of the myofilament-localized calcium transient in iPSC-CMs, indicating that sarcomeric calcium retention with Δ160E may affect intracellular calcium concentration. High-content imaging analysis detected remarkable nuclear translocation of NFATc1, especially in Homo-Δ160E-iPSC-CMs, indicating that the Δ160E mutation promotes hypertrophic signaling pathway in a dose-dependent manner. Increased phosphorylation of CaMKIIδ (calcium/calmodulin-dependent protein kinase IIδ) and phospholamban at Thr17 was observed in Homo- and Hetero-Δ160E-iPSC-CMs. Epigallocatechin-3-gallate, a calcium desensitizing compound, shortened prolonged calcium decay and relaxation duration in Δ160E-iPSC-CMs. CONCLUSIONS: Isogenic iPSC-CMs recapitulate the prolonged calcium decay, relaxation impairment, and subsequent calcium-regulated signaling pathways caused by the TNNT2 Δ160E mutation and can serve as a human model for therapeutic development to prevent hypertrophic cardiomyopathy pathology.

Modeling reduced contractility and impaired desmosome assembly due to plakophilin-2 deficiency using isogenic iPS cell-derived cardiomyocytes.

Loss-of-function mutations in PKP2, which encodes plakophilin-2, cause arrhythmogenic cardiomyopathy (AC). Restoration of deficient molecules can serve as upstream therapy, thereby requiring a human model that recapitulates disease pathology and provides distinct readouts in phenotypic analysis for proof of concept for gene replacement therapy. Here, we generated isogenic induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) with precisely adjusted expression of plakophilin-2 from a patient with AC carrying a heterozygous frameshift PKP2 mutation. After monolayer differentiation, plakophilin-2 deficiency led to reduced contractility, disrupted intercalated disc structures, and impaired desmosome assembly in iPSC-CMs. Allele-specific fluorescent labeling of endogenous DSG2 encoding desmoglein-2 in the generated isogenic lines enabled real-time desmosome-imaging under an adjusted dose of plakophilin-2. Adeno-associated virus-mediated gene replacement of PKP2 recovered contractility and restored desmosome assembly, which was sequentially captured by desmosome-imaging in plakophilin-2-deficient iPSC-CMs. Our isogenic set of iPSC-CMs recapitulates AC pathology and provides a rapid and convenient cellular platform for therapeutic development.

Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.

Desmoglein-2, encoded by DSG2, is one of the desmosome proteins that maintain the structural integrity of tissues, including heart. Genetic mutations in DSG2 cause arrhythmogenic cardiomyopathy, mainly in an autosomal dominant manner. Here, we identified a homozygous stop-gain mutations in DSG2 (c.C355T, p.R119X) that led to complete desmoglein-2 deficiency in a patient with severe biventricular heart failure. Histological analysis revealed abnormal deposition of desmosome proteins, disrupted intercalated disk structures in the myocardium. Induced pluripotent stem cells (iPSCs) were generated from the patient (R119X-iPSC), and the mutated DSG2 gene locus was heterozygously corrected to a normal allele via homology-directed repair (HDR-iPSC). Both isogenic iPSCs were differentiated into cardiomyocytes [induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs)]. Multielectrode array analysis detected abnormal excitation in R119X-iPSC-CMs but not in HDR-iPSC-CMs. Micro-force testing of three-dimensional self-organized tissue rings (SOTRs) revealed tissue fragility and a weak maximum force in SOTRs from R119X-iPSC-CMs. Notably, these phenotypes were significantly recovered in HDR-iPSC-CMs. Myocardial fiber structures in R119X-iPSC-CMs were severely aberrant, and electron microscopic analysis confirmed that desmosomes were disrupted in these cells. Unexpectedly, the absence of desmoglein-2 in R119X-iPSC-CMs led to decreased expression of desmocollin-2 but no other desmosome proteins. Adeno-associated virus-mediated replacement of DSG2 significantly recovered the contraction force in SOTRs generated from R119X-iPSC-CMs. Our findings confirm the presence of a desmoglein-2-deficient cardiomyopathy among clinically diagnosed dilated cardiomyopathies. Recapitulation and correction of the disease phenotype using iPSC-CMs provide evidence to support the development of precision medicine and the proof of concept for gene replacement therapy for this cardiomyopathy.

Adeno-associated virus-mediated gene delivery promotes S-phase entry-independent precise targeted integration in cardiomyocytes.

Post-mitotic cardiomyocytes have been considered to be non-permissive to precise targeted integration including homology-directed repair (HDR) after CRISPR/Cas9 genome editing. Here, we demonstrate that direct delivery of large amounts of transgene encoding guide RNA (gRNA) and repair template DNA via intra-ventricular injection of adeno-associated virus (AAV) promotes precise targeted genome replacement in adult murine cardiomyocytes expressing Cas9. Neither systemic injection of AAV nor direct injection of adenovirus promotes targeted integration, suggesting that high copy numbers of single-stranded transgenes are required in cardiomyocytes. Notably, AAV-mediated targeted integration in cardiomyocytes both in vitro and in vivo depends on the Fanconi anemia pathway, a key component of the single-strand template repair mechanism. In human cardiomyocytes differentiated from induced pluripotent stem cells, AAV-mediated targeted integration fluorescently labeled Mlc2v protein after differentiation, independently of DNA synthesis, and enabled real-time detection of sarcomere contraction in monolayered beating cardiomyocytes. Our findings provide a wide range of applications for targeted genome replacement in non-dividing cardiomyocytes.

Targeted Genome Replacement via Homology-directed Repair in Non-dividing Cardiomyocytes.

Although high-throughput sequencing can elucidate the genetic basis of hereditary cardiomyopathy, direct interventions targeting pathological mutations have not been established. Furthermore, it remains uncertain whether homology-directed repair (HDR) is effective in non-dividing cardiomyocytes. Here, we demonstrate that HDR-mediated genome editing using CRISPR/Cas9 is effective in non-dividing cardiomyocytes. Transduction of adeno-associated virus (AAV) containing sgRNA and repair template into cardiomyocytes constitutively expressing Cas9 efficiently introduced a fluorescent protein to the C-terminus of Myl2. Imaging-based sequential evaluation of endogenously tagged protein revealed that HDR occurs in cardiomyocytes, independently of DNA synthesis. We sought to repair a pathological mutation in Tnnt2 in cardiomyocytes of cardiomyopathy model mice. An sgRNA that avoided the mutated exon minimized deleterious effects on Tnnt2 expression, and AAV-mediated HDR achieved precise genome correction at a frequency of ~12.5%. Thus, targeted genome replacement via HDR is effective in non-dividing cardiomyocytes, and represents a potential therapeutic tool for targeting intractable cardiomyopathy.

Switching types of drug-eluting stents does not prevent repeated in-stent restenosis in patients with coronary drug-eluting stent restenosis.

OBJECTIVES: We treated patients experiencing drug-eluting stent (DES) restenosis with plain old balloon angioplasty (POBA), implantation of the same type of DES [homogeneous drug-eluting stent (HOMO-DES)], or implantation of a different type of DES [heterogeneous drug-eluting stent (HETERO-DES)], and compared the efficacy and safety of these procedures for the prevention of repeated in-stent restenosis (ISR). BACKGROUND: In patients with de-novo coronary lesions, DES implantation is associated with a markedly reduced restenosis rate as compared with that associated with a bare metal stent and POBA. However, the optimal management strategy for patients with DES ISR remains unknown. PATIENTS AND METHODS: We identified 191 consecutive DES ISR lesions from 183 patients who required clinically driven revascularization and divided them into three groups according to the treatment: 38 lesions were treated with POBA, 38 with HOMO-DES, and 115 with HETERO-DES. RESULTS: The incidence of target lesion revascularization (TLR) was 42.1% (16/38), 15.8% (6/38), and 16.5% (19/115) in the POBA, HOMO-DES, and HETERO-DES groups (POBA vs. HOMO, HETERO-DES; P=0.002, respectively). Multivariate analysis indicated that diabetes [odds ratio (OR), 3.4], hemodialysis (OR, 7.74), nonfocal ISR patterns (OR, 3.35), previous myocardial infarction (OR, 3.26), and POBA (OR, 8.84) were independent predictors of TLR. CONCLUSION: A strategy involving repeated DES implantation was superior to POBA for preventing recurrent restenosis. Treatment with a different type or generation of DES does not appear to reduce the incidence of TLR. Moreover, we identified certain useful factors for facilitating appropriate and early triage in the patients with repeated DES ISR.

Impact of contrast-induced acute kidney injury on outcomes in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention.

PURPOSE: The purpose of this study was to identify predictors of contrast-induced acute kidney injury (CI-AKI) and the effect of CI-AKI on cardiovascular outcomes after hospital discharge in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI). METHODS AND MATERIALS: We retrospectively reviewed 194 STEMI consecutive patients who underwent primary PCI to evaluate the predictors for CI-AKI and 187 survivors to examine all-cause mortality and cardiovascular events. Outcomes were compared between patients with CI-AKI and those without CI-AKI, which was defined as an increase >50% or >0.5mg/dl in serum creatinine concentration within 48hours after primary PCI. RESULTS: CI-AKI occurred in 23 patients (11.9%). Multivariate analysis identified pre-procedural renal insufficiency as a predictor of CI-AKI, and this predictor was independent from hemodynamic instability and excessive contrast volume. Receiver-operator characteristics analysis demonstrated that patients with an estimated glomerular filtration rate (eGFR) of ≤43.6ml/min per 1.73m(2) had the potential for CI-AKI. Patients who developed CI-AKI had higher mortality and cardiovascular events than did those without CI-AKI (27.8% vs. 4.7%; log-rank P=.0003, 27.8% vs. 11.2%; log-rank P=.0181, respectively). Cox proportional hazards model analysis identified CI-AKI as the independent predictor of mortality and cardiovascular events [hazard ratio [HR]=5.36; P=.0076, HR=3.10; P=.0250, respectively]. CONCLUSIONS: The risk of CI-AKI is increased in patients with pre-procedural renal insufficiency, and eGFR is clinically useful in the emergent setting for CI-AKI risk stratification before primary PCI.