Canonical Wnt signaling directs the generation of functional human PSC-derived atrioventricular canal cardiomyocytes in bioprinted cardiac tissues.

The creation of a functional 3D bioprinted human heart remains challenging, largely due to the lack of some crucial cardiac cell types, including the atrioventricular canal (AVC) cardiomyocytes, which are essential to slow down the electrical impulse between the atrium and ventricle. By utilizing single-cell RNA sequencing analysis and a 3D bioprinting technology, we discover that stage-specific activation of canonical Wnt signaling creates functional AVC cardiomyocytes derived from human pluripotent stem cells. These cardiomyocytes display morphological characteristics and express molecular markers of AVC cardiomyocytes, including transcription factors TBX2 and MSX2. When bioprinted in prefabricated cardiac tissues, these cardiomyocytes successfully delay the electrical impulse, demonstrating their capability of functioning as the AVC cardiomyocytes in vitro. Thus, these findings not only identify canonical Wnt signaling as a key regulator of the AVC cardiomyocyte differentiation in vitro, but, more importantly, provide a critical cellular source for the biofabrication of a functional human heart.

Cardiac Organoids: A 3D Technology for Modeling Heart Development and Disease.

Cardiac organoids (COs) are miniaturized and simplified organ structures that can be used in heart development biology, drug screening, disease modeling, and regenerative medicine. This cardiac organoid (CO) model is revolutionizing our perspective on answering major cardiac physiology and pathology issues. Recently, many research groups have reported various methods for modeling the heart in vitro. However, there are differences in methodologies and concepts. In this review, we discuss the recent advances in cardiac organoid technologies derived from human embryonic stem cells (hESCs) and human-induced pluripotent stem cells (hiPSCs), with a focus on the summary of methods for organoid generation. In addition, we introduce CO applications in modeling heart development and cardiovascular diseases and discuss the prospects for and common challenges of CO that still need to be addressed. A detailed understanding of the development of CO will help us design better methods, explore and expand its application in the cardiovascular field.

Emerging Roles of Inflammasomes in Cardiovascular Diseases.

Cardiovascular diseases are known as the leading cause of morbidity and mortality worldwide. As an innate immune signaling complex, inflammasomes can be activated by various cardiovascular risk factors and regulate the activation of caspase-1 and the production and secretion of proinflammatory cytokines such as IL-1ß and IL-18. Accumulating evidence supports that inflammasomes play a pivotal role in the progression of atherosclerosis, myocardial infarction, and heart failure. The best-known inflammasomes are NLRP1, NLRP3, NLRC4, and AIM2 inflammasomes, among which NLRP3 inflammasome is the most widely studied in the immune response and disease development. This review focuses on the activation and regulation mechanism of inflammasomes, the role of inflammasomes in cardiovascular diseases, and the research progress of targeting NLRP3 inflammasome and IL-1ß for related disease intervention.

Maturation of Stem Cell-Derived Cardiomyocytes: Foe in Translation Medicine.

With the in-depth study of heart development, many human cardiomyocytes (CMs) have been generated in a laboratory environment. CMs derived from pluripotent stem cells (PSCs) have been widely used for a series of applications such as laboratory studies, drug toxicology screening, cardiac disease models, and as an unlimited resource for cell-based cardiac regeneration therapy. However, the low maturity of the induced CMs significantly impedes their applicability. Scientists have been committed to improving the maturation of CMs to achieve the purpose of heart regeneration in the past decades. In this review, we take CMs maturation as the main object of discussion, describe the characteristics of CMs maturation, summarize the key regulatory mechanism of regulating maturation and address the approaches to promote CMs maturation. The maturation of CM is gradually improving due to the incorporation of advanced technologies and is expected to continue.

Single-Cell Reconstruction of Progression Trajectory Reveals Intervention Principles in Pathological Cardiac Hypertrophy.

BACKGROUND: Pressure overload-induced pathological cardiac hypertrophy is a common predecessor of heart failure, the latter of which remains a major cardiovascular disease with increasing incidence and mortality worldwide. Current therapeutics typically involve partially relieving the heart's workload after the onset of heart failure. Thus, more pathogenesis-, stage-, and cell type-specific treatment strategies require refined dissection of the entire progression at the cellular and molecular levels. METHODS: By analyzing the transcriptomes of 11,492 single cells and identifying major cell types, including both cardiomyocytes and noncardiomyocytes, on the basis of their molecular signatures, at different stages during the progression of pressure overload-induced cardiac hypertrophy in a mouse model, we characterized the spatiotemporal interplay among cell types, and tested potential pharmacological treatment strategies to retard its progression in vivo. RESULTS: We illustrated the dynamics of all major cardiac cell types, including cardiomyocytes, endothelial cells, fibroblasts, and macrophages, as well as those of their respective subtypes, during the progression of disease. Cellular crosstalk analysis revealed stagewise utilization of specific noncardiomyocytes during the deterioration of heart function. Specifically, macrophage activation and subtype switching, a key event at middle-stage of cardiac hypertrophy, was successfully targeted by Dapagliflozin, a sodium glucose cotransporter 2 inhibitor, in clinical trials for patients with heart failure, as well as TD139 and Arglabin, two anti-inflammatory agents new to cardiac diseases, to preserve cardiac function and attenuate fibrosis. Similar molecular patterns of hypertrophy were also observed in human patient samples of hypertrophic cardiomyopathy and heart failure. CONCLUSIONS: Together, our study not only illustrated dynamically changing cell type crosstalk during pathological cardiac hypertrophy but also shed light on strategies for cell type- and stage-specific intervention in cardiac diseases.

Single-cell reconstruction of differentiation trajectory reveals a critical role of ETS1 in human cardiac lineage commitment.

BACKGROUND: Cardiac differentiation from human pluripotent stem cells provides a unique opportunity to study human heart development in vitro and offers a potential cell source for cardiac regeneration. Compared to the large body of studies investigating cardiac maturation and cardiomyocyte subtype-specific induction, molecular events underlying cardiac lineage commitment from pluripotent stem cells at early stage remain poorly characterized. RESULTS: In order to uncover key molecular events and regulators controlling cardiac lineage commitment from a pluripotent state during differentiation, we performed single-cell RNA-Seq sequencing and obtained high-quality data for 6879 cells collected from 6 stages during cardiac differentiation from human embryonic stem cells and identified multiple cell subpopulations with distinct molecular features. Through constructing developmental trajectory of cardiac differentiation and putative ligand-receptor interactions, we revealed crosstalk between cardiac progenitor cells and endoderm cells, which could potentially provide a cellular microenvironment supporting cardiac lineage commitment at day 5. In addition, computational analyses of single-cell RNA-Seq data unveiled ETS1 (ETS Proto-Oncogene 1) activation as an important downstream event induced by crosstalk between cardiac progenitor cells and endoderm cells. Consistent with the findings from single-cell analysis, chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-Seq) against ETS1 revealed genomic occupancy of ETS1 at cardiac structural genes at day 9 and day 14, whereas ETS1 depletion dramatically compromised cardiac differentiation. CONCLUSION: Together, our study not only characterized the molecular features of different cell types and identified ETS1 as a crucial factor induced by cell-cell crosstalk contributing to cardiac lineage commitment from a pluripotent state, but may also have important implications for understanding human heart development at early embryonic stage, as well as directed manipulation of cardiac differentiation in regenerative medicine.

THO Complex-Dependent Posttranscriptional Control Contributes to Vascular Smooth Muscle Cell Fate Decision.

RATIONALE: Modulation of vascular smooth muscle cell (VSMC) phenotype plays a fundamental role in vascular development and diseases. Although extensive studies uncovered the roles of transcriptional regulation in VSMC-specific gene expression, how posttranscriptional regulation contributes to VSMC fate decisions remains to be determined. OBJECTIVE: To establish THO complex-dependent VSMC gene expression as a novel regulatory basis controlling VSMC phenotypes. METHODS AND RESULTS: Immunohistochemical staining against THOC2 and THOC5, 2 components of the THO complex, revealed a dramatic reduction in their expression in human arteries undergoing carotid endarterectomy compared with normal internal mammary arteries. Silencing of THOC2 or THOC5 led to dedifferentiation of VSMCs in vitro, characterized by decreased VSMC marker gene expression and increased migration and proliferation. Furthermore, RNA high-throughput sequencing (Seq) revealed that THOC5 silencing closely resembled the gene expression changes induced on PDGF (platelet-derived growth factor)-BB/PDGF-DD treatments in cultured VSMCs. Mechanistically, THOC2 and THOC5 physically interacted with and functionally relied on each other to bind to specific motifs on VSMC marker gene mRNAs. Interestingly, mRNAs that lost THOC2 or THOC5 binding during VSMC dedifferentiation were enriched for genes important for the differentiated VSMC phenotype. Last, THOC5 overexpression in injured rat carotid arteries significantly repressed loss of VSMC marker gene expression and neointima formation. CONCLUSIONS: Our data introduce dynamic binding of THO to VSMC marker gene mRNAs as a novel mechanism contributing to VSMC phenotypic switching and imply THOC5 as a potential intervention node for vascular diseases.