Generation of microRNA-378a-deficient hiPSC as a novel tool to study its role in human cardiomyocytes

Upregulation of utrophin improves the phenotype of Duchenne muscular dystrophy hiPSC-derived CMs

Duchenne muscular dystrophy (DMD) is a genetic neuromuscular disease. Although it leads to muscle weakness, affected individuals predominantly die from cardiomyopathy, which remains uncurable. Accumulating evidence suggests that an overexpression of utrophin may counteract some of the pathophysiological outcomes of DMD. The aim of this study was to investigate the role of utrophin in dystrophin-deficient human cardiomyocytes (CMs) and to test whether an overexpression of utrophin, implemented via the CRISPR-deadCas9-VP64 system, can improve their phenotype. We used human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) lacking either dystrophin (DMD) or both dystrophin and utrophin (DMD KO/UTRN(+/-)). We carried out proteome analysis, which revealed considerable differences in the proteins related to muscle contraction, cell-cell adhesion, and extracellular matrix organization. Furthermore, we evaluated the role of utrophin in maintaining the physiological properties of DMD hiPSC-CMs using atomic force microscopy, patch-clamp, and Ca2+ oscillation analysis. Our results showed higher values of afterhyperpolarization and altered patterns of cytosolic Ca2+ oscillations in DMD; the latter was further disturbed in DMD KO/UTRN(+/-) hiPSC-CMs. Utrophin upregulation improved both parameters. Our findings demonstrate for the first time that utrophin maintains the physiological functions of DMD hiPSC-CMs, and that its upregulation can compensate for the loss of dystrophin.

Generation of human induced pluripotent stem cell line derived from Becker muscular dystrophy patient with CRISPR/Cas9-mediated correction of DMD gene mutation

Becker muscular dystrophy (BMD) is an X-linked recessive disorder caused by in-frame deletions in the dystrophin gene (DMD), leading to progressive muscle degeneration and weakness. We generated a human induced pluripotent stem cell (hiPSC) line from a BMD patient. BMD hiPSCs were then engineered by CRISPR/Cas9-mediated knock-in of missing exons 3-9 of DMD gene. Obtained hiPSC line may be a valuable tool for investigating the mechanisms underlying BMD pathogenesis.

Dysregulated iron homeostasis in dystrophin-deficient cardiomyocytes: correction by gene editing and pharmacological treatment

AIMS

Duchenne muscular dystrophy (DMD)-associated cardiomyopathy is a serious life-threatening complication, the mechanisms of which have not been fully established, and therefore no effective treatment is currently available. The purpose of the study was to identify new molecular signatures of the cardiomyopathy development in DMD.

METHODS AND RESULTS

For modelling of DMD-associated cardiomyopathy, we prepared three pairs of isogenic control and dystrophin-deficient human induced pluripotent stem cell (hiPSC) lines. Two isogenic hiPSC lines were obtained by CRISPR/Cas9-mediated deletion of DMD exon 50 in unaffected cells generated from healthy donor and then differentiated into cardiomyocytes (hiPSC-CM). The latter were subjected to global transcriptomic and proteomic analyses followed by more in-depth investigation of selected pathway and pharmacological modulation of observed defects. Proteomic analysis indicated a decrease in the level of mitoNEET protein in dystrophin-deficient hiPSC-CM, suggesting alteration in iron metabolism. Further experiments demonstrated increased labile iron pool both in the cytoplasm and mitochondria, a decrease in ferroportin level and an increase in both ferritin and transferrin receptor in DMD hiPSC-CM. Importantly, CRISPR/Cas9-mediated correction of the mutation in the patient-derived hiPSC reversed the observed changes in iron metabolism and restored normal iron levels in cardiomyocytes. Moreover, treatment of DMD hiPSC-CM with deferoxamine (DFO, iron chelator) or pioglitazone (mitoNEET stabilizing compound) decreased the level of reactive oxygen species in DMD hiPSC-CM.

CONCLUSION

To our knowledge, this study demonstrated for the first time impaired iron metabolism in human DMD cardiomyocytes, and potential reversal of this effect by correction of DMD mutation or pharmacological treatment. This implies that iron overload-regulating compounds may serve as novel therapeutic agents in DMD-associated cardiomyopathy.

Cardioprotective Effects of Hydrogen Sulfide and Its Potential Therapeutic Implications in the Amelioration of Duchenne Muscular Dystrophy Cardiomyopathy

Hydrogen sulfide (H2S) belongs to the family of gasotransmitters and can modulate a myriad of biological signaling pathways. Among others, its cardioprotective effects, through antioxidant, anti-inflammatory, anti-fibrotic, and proangiogenic activities, are well-documented in experimental studies. Cardiorespiratory failure, predominantly cardiomyopathy, is a life-threatening complication that is the number one cause of death in patients with Duchenne muscular dystrophy (DMD). Although recent data suggest the role of H2S in ameliorating muscle wasting in murine and Caenorhabditis elegans models of DMD, possible cardioprotective effects have not yet been addressed. In this review, we summarize the current understanding of the role of H2S in animal models of cardiac dysfunctions and cardiac cells. We highlight that DMD may be amenable to H2S supplementation, and we suggest H2S as a possible factor regulating DMD-associated cardiomyopathy.

Casein kinase 2 activity is a host restriction factor for AAV transduction

So far, the mechanisms that impede AAV transduction, especially in the human heart, are poorly understood, hampering the introduction of new, effective gene therapy strategies. Therefore, the aim of this study was to identify and overcome the main cellular barriers to successful transduction in the heart, using induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs), iPSC-derived cardiac fibroblasts (iPSC-CFs), and primary endothelial cells to model vector-host interactions. Through phosphoproteome analysis we established that casein kinase 2 (CK2) signaling is one of the most significantly affected pathways upon AAV exposure. Transient inhibition of CK2 activity substantially enhanced the transduction rate of AAV2, AAV6, and AAV9 in all tested cell types. In particular, CK2 inhibition improved the trafficking of AAVs through the cytoplasm, impaired DNA damage response through destabilization of MRE11, and altered the RNA processing pathways, which were also highly responsive to AAV transduction. Also, it augmented transgene expression in already transduced iPSC-CFs, which retain AAV genomes in a functional, but probably silent form. In summary, the present study provides new insights into the current understanding of the host-AAV vector interaction, identifying CK2 activity as a key barrier to efficient transduction and transgene expression, which may translate to improving the outcome of AAV-based therapies in the future.

Comparison of Two Differentiation Protocols of Human-Induced Pluripotent Stem Cells into Cardiomyocytes

Cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) offer an attractive platform to evaluate the mechanisms of cardiovascular-related incidents and to develop and test new drugs for heart diseases. This work focuses on the comparison of two hiPSC-CM differentiation protocols: the GiWi method based on temporal modulation of the Wnt/β-catenin pathway and the commercially available PSC Cardiomyocyte Differentiation Kit. We underlined the need to optimize several parameters such as cell density or small molecule concentration (CHIR-99021, IWR-1) to obtain functional hiPSC-CMs. Both protocols yield a similar differentiation efficiency; therefore, the choice of a particular procedure may depend on the preferences of the experimenter.

Compromised diabetic heart function is not affected by miR-378a upregulation upon hyperglycemia

BACKGROUND

Cardiac-abundant microRNA-378a (miR-378a) is associated with postnatal repression of insulin-like growth factor 1 receptor (IGF-1R) controlling physiological hypertrophy and survival pathways. IGF-1/IGF-1R axis has been proposed as a therapeutic candidate against the pathophysiological progress of diabetic cardiomyopathy (DCM). We ask whether hyperglycemia-driven changes in miR-378a expression could mediate DCM progression.

METHODS

Diabetes mellitus was induced by streptozotocin (STZ) (55 mg/kg i.p. for 5 days) in male C57BL/6 wild type (miR-378a+/+) and miR-378a knockout (miR-378a-/-) mice. As a parallel human model, we harnessed human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM miR378a+/+ vs. hiPSC-CM miR378a-/-) subjected to high glucose (HG) treatment.

RESULTS

We reported miR-378a upregulation in cardiac diabetic milieu arising upon STZ administration to wild-type mice and in HG-treated hiPSC-CMs. Pro-hypertrophic IGF-1R/ERK1/2 pathway and hypertrophic marker expression were activated in miR-378a deficiency and upon STZ/HG treatment of miR-378a+/+ specimens in vivo and in vitro suggesting miR-378a-independent hyperglycemia-promoted hypertrophy. A synergistic upregulation of IGF-1R signaling in diabetic conditions was detected in miR-378a-/- hiPSC-CMs, but not in miR-378a-/- hearts that showed attenuation of this pathway, pointing to the involvement of compensatory mechanisms in the absence of miR-378a. Although STZ administration did not cause pro-inflammatory or pro-fibrotic effects that were detected in miR-378a-/- mice, the compromised diabetic heart function observed in vivo by high-resolution ultrasound imaging upon STZ treatment was not affected by miR-378a presence.

CONCLUSIONS

Overall, data underline the role of miR-378a in maintaining basal cardiac structural integrity while pointing to miR-378a-independent hyperglycemia-driven cardiac hypertrophy and associated dysfunction.

Generation of human induced pluripotent stem cell lines with HMOX1 promoter polymorphism and CRISPR/Cas9-mediated deletion of exon 50 of DMD gene

Duchenne muscular dystrophy (DMD), originating from the lack of functional dystrophin, clinically manifests as devastating disease of skeletal muscles with progressive cardiac involvement. HMOX1 promoter polymorphism may reflect different activity of heme oxygenase-1 (HO-1) that may be critical for DMD progression. Here we generated human induced pluripotent stem cell (hiPSC) lines from healthy donors-derived peripheral blood mononuclear cells with different variants of HMOX1 promoter (GT repeats), and engineered by CRISPR/Cas9-mediated deletion of exon 50 of DMD gene. Such in vitro model could add to molecular understanding of DMD and verify the prognostic value of HMOX1 promoter polymorphism.

Cardiac calcium regulation in human induced pluripotent stem cell cardiomyocytes: Implications for disease modeling and maturation

Human induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) are based on ground-breaking technology that has significantly impacted cardiovascular research. They provide a renewable source of human cardiomyocytes for a variety of applications including in vitro disease modeling and drug toxicity testing. Cardiac calcium regulation plays a critical role in the cardiomyocyte and is often dysregulated in cardiovascular disease. Due to the limited availability of human cardiac tissue, calcium handling and its regulation have most commonly been studied in the context of animal models. hiPSC-CMs can provide unique insights into human physiology and pathophysiology, although a remaining limitation is the relative immaturity of these cells compared to adult cardiomyocytes Therefore, this field is rapidly developing techniques to improve the maturity of hiPSC-CMs, further establishing their place in cardiovascular research. This review briefly covers the basics of cardiomyocyte calcium cycling and hiPSC technology, and will provide a detailed description of our current understanding of calcium in hiPSC-CMs.

Adaptation of cardiomyogenesis to the generation and maturation of cardiomyocytes from human pluripotent stem cells

The advent of methods for efficient generation and cardiac differentiation of pluripotent stem cells opened new avenues for disease modelling, drug testing, and cell therapies of the heart. However, cardiomyocytes (CM) obtained from such cells demonstrate an immature, foetal-like phenotype that involves spontaneous contractions, irregular morphology, expression of embryonic isoforms of sarcomere components, and low level of ion channels. These and other features may affect cellular response to putative therapeutic compounds and the efficient integration into the host myocardium after in vivo delivery. Therefore, novel strategies to increase the maturity of pluripotent stem cell-derived CM are of utmost importance. Several approaches have already been developed relying on molecular changes that occur during foetal and postnatal maturation of the heart, its electromechanical activity, and the cellular composition. As a better understanding of these determinants may facilitate the generation of efficient protocols for in vitro acquisition of an adult-like phenotype by immature CM, this review summarizes the most important molecular factors that govern CM during embryonic development, postnatal changes that trigger heart maturation, as well as protocols that are currently used to generate mature pluripotent stem cell-derived cardiomyocytes.

Expression of Extracellular Vesicle PIWI-Interacting RNAs Throughout hiPSC-Cardiomyocyte Differentiation

Extracellular Vesicles (EV) play a critical role in the regulation of regenerative processes in wounded tissues by mediating cell-to-cell communication. Multiple RNA species have been identified in EV, although their function still lacks understanding. We previously characterized the miRNA content of EV secreted over hiPSC-cardiomyocyte differentiation and found a distinct miRNA expression in hiPSC-EV driving its in vitro bioactivity. In this work, we investigated the piRNA profiles of EV derived from key stages of the hiPSC-CM differentiation and maturation, i.e., from hiPSC (hiPSC-EV), cardiac progenitors (CPC-EV), immature (CMi-EV), and mature (CMm-EV) cardiomyocytes, demonstrating that EV-piRNA expression differs greatly from the miRNA profiles we previously identified. Only four piRNA were significantly deregulated in EV, one in hiPSC-EV, and three in CPC-EV, as determined by differential expression analysis on small RNA-seq data. Our results provide a valuable source of information for further studies aiming at defining the role of piRNA in the bioactivity and therapeutic potential of EV.

miR-378 affects metabolic disturbances in the mdx model of Duchenne muscular dystrophy

Although Duchenne muscular dystrophy (DMD) primarily affects muscle tissues, the alterations to systemic metabolism manifested in DMD patients contribute to the severe phenotype of this fatal disorder. We propose that microRNA-378a (miR-378) alters carbohydrate and lipid metabolism in dystrophic mdx mice. In our study, we utilized double knockout animals which lacked both dystrophin and miR-378 (mdx/miR-378^-/-). RNA sequencing of the liver identified 561 and 194 differentially expressed genes that distinguished mdx versus wild-type (WT) and mdx/miR-378^-/- versus mdx counterparts, respectively. Bioinformatics analysis predicted, among others, carbohydrate metabolism disorder in dystrophic mice, as functionally proven by impaired glucose tolerance and insulin sensitivity. The lack of miR-378 in mdx animals mitigated those effects with a faster glucose clearance in a glucose tolerance test (GTT) and normalization of liver glycogen levels. The absence of miR-378 also restored the expression of genes regulating lipid homeostasis, such as Acly, Fasn, Gpam, Pnpla3, and Scd1. In conclusion, we report for the first time that miR-378 loss results in increased systemic metabolism of mdx mice. Together with our previous finding, demonstrating alleviation of the muscle-related symptoms of DMD, we propose that the inhibition of miR-378 may represent a new strategy to attenuate the multifaceted symptoms of DMD.