The Unfolded Protein Response as a Compensatory Mechanism and Potential Therapeutic Target in PLN R14del Cardiomyopathy.
Background: Phospholamban (PLN) is a critical regulator of calcium cycling and contractility in the heart. The loss of arginine at position 14 in PLN (R14del) is associated with dilated cardiomyopathy (DCM) with a high prevalence of ventricular arrhythmias. How the R14 deletion causes DCM is poorly understood and there are no disease-specific therapies. Methods: We used single-cell RNA sequencing to uncover PLN R14del disease-mechanisms in human induced pluripotent stem cells (hiPSC-CMs). We utilized both 2D and 3D functional contractility assays to evaluate the impact of modulating disease relevant pathways in PLN R14del hiPSC-CMs. Results: Modeling of the PLN R14del cardiomyopathy with isogenic pairs of hiPSC-CMs recapitulated the contractile deficit associated with the disease in vitro. Single-cell RNA sequencing revealed the induction of the unfolded protein response pathway (UPR) in PLN R14del compared to isogenic control hiPSC-CMs. The activation of UPR was also evident in the hearts from PLN R14del patients. Silencing of each of the three main UPR signaling branches (IRE1, ATF6, or PERK) by siRNA exacerbated the contractile dysfunction of PLN R14del hiPSC-CMs. We explored the therapeutic potential of activating the UPR with a small molecule activator, BiP protein Inducer X (BiX). PLN R14del hiPSC-CMs treated with BiX showed a dose-dependent amelioration of the contractility deficit of in both 2D cultures and 3D engineered heart tissues without affecting calcium homeostasis. Conclusions: Together, these findings suggest that the UPR exerts a protective effect in the setting of PLN R14del cardiomyopathy and that modulation of the UPR might be exploited therapeutically.
View details for DOI 10.1161/CIRCULATIONAHA.120.049844
View details for PubMedID 33928785
- Activation of CaMKII Signaling Pathway Contributes to the Pathogenesis of Genetic Hypertrophic Cardiomyopathy LIPPINCOTT WILLIAMS & WILKINS. 2020
- Disruption of the Genome Architecture at the PRRX1 Locus is Associated With the Pathogenesis of LMNA-related Dilated Cardiomyopathy LIPPINCOTT WILLIAMS & WILKINS. 2020
Translating Genomic Insights into Cardiovascular Medicines: Opportunities and Challenges of CRISPR-Cas9.
Trends in cardiovascular medicine
The growing appreciation of human genetics and genomics in cardiovascular disease (CVD) accompanied by the technological breakthroughs in genome editing, particularly the CRISPR-Cas9 technologies, has presented an unprecedented opportunity to explore the application of genome editing tools in cardiovascular medicine. The ever-growing genome-editing toolbox includes an assortment of CRISPR-Cas systems with increasing efficiency, precision, flexibility, and targeting capacity. Over the past decade, the advent of large-scale genotyping technologies and genome-wide association studies (GWAS) has provided powerful tools to identify genotype-phenotype associations for diseases with complex traits. Notably, a growing number of loss-of-function mutations have been associated with favorable CVD risk-factor profiles that may confer protection. Combining the newly gained insights into human genetics with recent breakthrough technologies, such as the CRISPR technology, holds great promise in elucidating novel disease mechanisms and transforming genes into medicines. Nonetheless, translating genetic insights into novel therapeutic avenues remains challenging, and applications of "in body" genome editing for CVD treatment and engineering cardioprotection remain mostly theoretical. Here we highlight the recent advances of the CRISPR-based genome editing toolbox and discuss the potential and challenges of CRISPR-based technologies for translating GWAS findings into genomic medicines.
View details for DOI 10.1016/j.tcm.2020.06.008
View details for PubMedID 32603681
A Novel Recessive Mutation in SPEG Causes Early Onset Dilated Cardiomyopathy.
2020; 16 (9): e1009000
Dilated cardiomyopathy (DCM) is a common cause of heart failure and sudden cardiac death. It has been estimated that up to half of DCM cases are hereditary. Mutations in more than 50 genes, primarily autosomal dominant, have been reported. Although rare, recessive mutations are thought to contribute considerably to DCM, especially in young children. Here we identified a novel recessive mutation in the striated muscle enriched protein kinase (SPEG, p. E1680K) gene in a family with nonsyndromic, early onset DCM. To ascertain the pathogenicity of this mutation, we generated SPEG E1680K homozygous mutant human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) using CRISPR/Cas9-mediated genome editing. Functional studies in mutant iPSC-CMs showed aberrant calcium homeostasis, impaired contractility, and sarcomeric disorganization, recapitulating the hallmarks of DCM. By combining genetic analysis with human iPSCs, genome editing, and functional assays, we identified SPEG E1680K as a novel mutation associated with early onset DCM and provide evidence for its pathogenicity in vitro. Our study provides a conceptual paradigm for establishing genotype-phenotype associations in DCM with autosomal recessive inheritance.
View details for DOI 10.1371/journal.pgen.1009000
View details for PubMedID 32925938
Stage-specific Effects of Bioactive Lipids on Human iPSC Cardiac Differentiation and Cardiomyocyte Proliferation.
2018; 8 (1): 6618
Bioactive lipids such as sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) regulate diverse processes including cell proliferation, differentiation, and migration. However, their roles in cardiac differentiation and cardiomyocyte proliferation have not been explored. Using a 96-well differentiation platform for generating human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) we found that S1P and LPA can independently enhance cardiomyocyte generation when administered at an early stage of differentiation. We showed that the combined S1P and LPA treatment of undifferentiated hiPSCs resulted in increased nuclear accumulation of β-catenin, the canonical Wnt signaling pathway mediator, and synergized with CHIR99021, a glycogen synthase kinase 3 beta inhibitor, to enhance mesodermal induction and subsequent cardiac differentiation. At later stages of cardiac differentiation, the addition of S1P and LPA resulted in cell cycle initiation in hiPSC-CMs, an effect mediated through increased ERK signaling. Although the addition of S1P and LPA alone was insufficient to induce cell division, it was able to enhance β-catenin-mediated hiPSC-CM proliferation. In summary, we demonstrated a developmental stage-specific effect of bioactive lipids to enhance hiPSC-CM differentiation and proliferation via modulating the effect of canonical Wnt/β-catenin and ERK signaling. These findings may improve hiPSC-CM generation for cardiac disease modeling, precision medicine, and regenerative therapies.
View details for PubMedID 29700394
High-throughput screening of tyrosine kinase inhibitor cardiotoxicity with human induced pluripotent stem cells.
Science translational medicine
2017; 9 (377)
Tyrosine kinase inhibitors (TKIs), despite their efficacy as anticancer therapeutics, are associated with cardiovascular side effects ranging from induced arrhythmias to heart failure. We used human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), generated from 11 healthy individuals and 2 patients receiving cancer treatment, to screen U.S. Food and Drug Administration-approved TKIs for cardiotoxicities by measuring alterations in cardiomyocyte viability, contractility, electrophysiology, calcium handling, and signaling. With these data, we generated a "cardiac safety index" to reflect the cardiotoxicities of existing TKIs. TKIs with low cardiac safety indices exhibit cardiotoxicity in patients. We also derived endothelial cells (hiPSC-ECs) and cardiac fibroblasts (hiPSC-CFs) to examine cell type-specific cardiotoxicities. Using high-throughput screening, we determined that vascular endothelial growth factor receptor 2 (VEGFR2)/platelet-derived growth factor receptor (PDGFR)-inhibiting TKIs caused cardiotoxicity in hiPSC-CMs, hiPSC-ECs, and hiPSC-CFs. With phosphoprotein analysis, we determined that VEGFR2/PDGFR-inhibiting TKIs led to a compensatory increase in cardioprotective insulin and insulin-like growth factor (IGF) signaling in hiPSC-CMs. Up-regulating cardioprotective signaling with exogenous insulin or IGF1 improved hiPSC-CM viability during cotreatment with cardiotoxic VEGFR2/PDGFR-inhibiting TKIs. Thus, hiPSC-CMs can be used to screen for cardiovascular toxicities associated with anticancer TKIs, and the results correlate with clinical phenotypes. This approach provides unexpected insights, as illustrated by our finding that toxicity can be alleviated via cardioprotective insulin/IGF signaling.
View details for DOI 10.1126/scitranslmed.aaf2584
View details for PubMedID 28202772
Harnessing the Induction of Cardiomyocyte Proliferation for Cardiac Regenerative Medicine.
Current treatment options in cardiovascular medicine
2015; 17 (10): 404-?
Adult human cardiomyocytes are terminally differentiated and have limited capacity for cell division. Hence, they are not naturally replaced following ischemic injury to the heart. As such, cardiac function is often permanently compromised after an event such as myocardial infarction. In recent years, investigators have focused intensively on ways to reactivate cardiomyocyte mitotic activity in both in vitro cell culture systems and in vivo animal models. In parallel, advances in stem cell biology have allowed for the mass production of patient-specific human cardiomyocytes from human-induced pluripotent stem cells. These cells can be produced via chemically defined differentiation of human pluripotent stem cells in a matter of weeks and could theoretically be utilized directly for therapeutic purposes to replace damaged myocardium. However, stem cell-derived cardiomyocytes, like their adult counterparts, are post-mitotic and incapable of large-scale expansion after reaching a certain stage of in vitro differentiation. Due to this shared characteristic, these stem cell-derived cardiomyocytes may provide a platform for studying genes, pathways, and small molecules that induce cell cycle reentry and proliferation of human cardiomyocytes. Ultimately, the discovery of novel mechanisms or pathways to induce human cardiomyocyte proliferation should improve our ability to regenerate adult cardiomyocytes and help restore cardiac function following injury.
View details for DOI 10.1007/s11936-015-0404-z
View details for PubMedID 26324824