a-cardiac-microphysiological-system-for-studying-ca2-propagation-via

A Cardiac Microphysiological System for Studying Ca<sup>2+</sup> Propagation via Non-genetic Optical Stimulation

In vitro cardiac microphysiological models are highly reliable for scientific research, drug development, and medical applications. Although widely ...

Harvard University

Children with acquired heart disease face significant health challenges, including a lifetime of strict medical management, multiple cardiac surgeries, and a high mortality risk. Though the presentation of these conditions is diverse, a unifying factor is the role of immune and inflammatory responses in their development and/or progression. For example, infectious agents have been linked to pediatric cardiovascular disease, leading to a large health burden that disproportionately affects low-income areas. Other implicated mechanisms include antibody targeting of cardiac proteins, infection of cardiac cells, and inflammation-mediated damage to cardiac structures. These changes can alter blood flow patterns, change extracellular matrix composition, and induce cardiac remodeling. Therefore, understanding the relationship between the immune system and cardiovascular disease can inform targeted diagnostic and treatment approaches. In this review, we discuss the current understanding of pediatric immune-associated cardiac diseases, challenges in the field, and areas of research with potential for clinical benefit.

The Immune and Inflammatory Basis of Acquired Pediatric Cardiac Disease.

Congenital heart disease (CHD) poses a significant global health and economic burden-despite advances in treating CHD reducing the mortality risk, globally CHD accounts for approximately 300,000 deaths yearly. Children with CHD experience both acute and chronic cardiac complications, and though treatment options have improved, some remain extremely invasive. A challenge in addressing these morbidity and mortality risks is that little is known regarding the cause of many CHDs and current evidence suggests a multifactorial etiology. Some studies implicate an immune contribution to CHD development; however, the role of the immune system is not well-understood. Defining the role of the immune and inflammatory responses in CHD therefore holds promise in elucidating mechanisms underlying these disorders and improving upon current diagnostic and treatment options. In this review, we address the current knowledge coinciding CHDs with immune and inflammatory associations, emphasizing conditions where this understanding would provide clinical benefit, and challenges in studying these mechanisms.

Congenital Heart Disease: An Immunological Perspective.

Engineered nanomaterials offer the benefit of having systematically tunable physicochemical characteristics (e.g., size, dimensionality, and surface chemistry) that highly dictate the biological activity of a material. Among the most promising engineered nanomaterials to date are graphene-family nanomaterials (GFNs), which are 2-D nanomaterials (2DNMs) with unique electrical and mechanical properties. Beyond engineering new nanomaterial properties, employing safety-by-design through considering the consequences of cell-material interactions is essential for exploring their applicability in the biomedical realm. In this study, we asked the effect of GFNs on the endothelial barrier function and cellular architecture of vascular endothelial cells. Using micropatterned cell pairs as a reductionist in vitro model of the endothelium, the progression of cytoskeletal reorganization as a function of GFN surface chemistry and time was quantitatively monitored. Here, we show that the surface oxidation of GFNs (graphene, reduced graphene oxide, partially reduced graphene oxide, and graphene oxide) differentially affect the endothelial barrier at multiple scales; from the biochemical pathways that influence the development of cellular protrusions to endothelial barrier integrity. More oxidized GFNs induce higher endothelial permeability and the increased formation of cytoplasmic protrusions such as filopodia. We found that these changes in cytoskeletal organization, along with barrier function, can be potentiated by the effect of GFNs on the Rho/Rho-associated kinase (ROCK) pathway. Specifically, GFNs with higher surface oxidation elicit stronger ROCK2 inhibitory behavior as compared to pristine graphene sheets. Overall, findings from these studies offer a new perspective towards systematically controlling the surface-dependent effects of GFNs on cytoskeletal organization via ROCK2 inhibition, providing insight for implementing safety-by-design principles in GFN manufacturing towards their targeted biomedical applications.

Differential modulation of endothelial cytoplasmic protrusions after exposure to graphene-family nanomaterials.

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that causes life-threatening arrhythmias and myocardial dysfunction. Pathogenic variants in Plakophilin-2 (PKP2), a desmosome component within specialized cardiac cell junctions, cause the majority of ACM cases. However, the molecular mechanisms by which PKP2 variants induce disease phenotypes remain unclear. Here we built bioengineered platforms using genetically modified human induced pluripotent stem cell-derived cardiomyocytes to model the early spatiotemporal process of cardiomyocyte junction assembly in vitro. Heterozygosity for truncating variant PKP2 reduced Wnt/β-catenin signaling, impaired myofibrillogenesis, delayed mechanical coupling, and reduced calcium wave velocity in engineered tissues. These abnormalities were ameliorated by SB216763, which activated Wnt/β-catenin signaling, improved cytoskeletal organization, restored cell junction integrity in cell pairs, and improved calcium wave velocity in engineered tissues. Together, these findings highlight the therapeutic potential of modulating Wnt/β-catenin signaling in a human model of ACM.

Spatiotemporal cell junction assembly in human iPSC-CM models of arrhythmogenic cardiomyopathy.

Human iPSC-derived cardiomyocytes (hiPSC-CMs) have proven invaluable for cardiac disease modeling and regeneration. Challenges with quality, inter-batch consistency, cryopreservation and scale remain, reducing experimental reproducibility and clinical translation. Here, we report a robust stirred suspension cardiac differentiation protocol, and we perform extensive morphological and functional characterization of the resulting bioreactor-differentiated iPSC-CMs (bCMs). Across multiple different iPSC lines, the protocol produces 1.2E6/mL bCMs with ~94% purity. bCMs have high viability after cryo-recovery (>90%) and predominantly ventricular identity. Compared to standard monolayer-differentiated CMs, bCMs are more reproducible across batches and have more mature functional properties. The protocol also works with magnetically stirred spinner flasks, which are more economical and scalable than bioreactors. Minor protocol modifications generate cardiac organoids fully in suspension culture. These reproducible, scalable, and resource-efficient approaches to generate iPSC-CMs and organoids will expand their applications, and our benchmark data will enable comparison to cells produced by other cardiac differentiation protocols.

Efficient and reproducible generation of human iPSC-derived cardiomyocytes and cardiac organoids in stirred suspension systems.

N-terminal-acetyltransferases including NAA10 catalyze N-terminal acetylation (Nt-acetylation), an evolutionarily conserved co-translational modification. Little is known about the role of Nt-acetylation in cardiac homeostasis. To gain insights, we studied a novel NAA10 variant (p.R4S) segregating with QT-prolongation, cardiomyopathy and developmental delay in a large kindred. Here we show that the NAA10-R4S mutation reduced enzymatic activity, decreased expression levels of NAA10/NAA15 proteins, and destabilized the enzymatic complex NatA. In NAA10R4S/Y-iPSC-CMs, dysregulation of the late sodium and slow rectifying potassium currents caused severe repolarization abnormalities, consistent with clinical QT prolongation. Engineered heart tissues generated from NAA10R4S/Y-iPSC-CMs had significantly decreased contractile force and sarcomeric disorganization, consistent with the pedigree's cardiomyopathic phenotype. We identified small molecule and genetic therapies that normalized the phenotype of NAA10R4S/Y-iPSC-CMs. Our study defines novel roles of Nt-acetylation in cardiac regulation and delineates mechanisms underlying QT prolongation, arrhythmia, and cardiomyopathy caused by NAA10 dysfunction.

Dysregulation of N-terminal acetylation causes cardiac arrhythmia and cardiomyopathy.

Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) lack nanoscale structures essential for efficient excitation-contraction coupling. Such nanostructures, known as dyads, are frequently disrupted in heart failure. Here we show that the reduced expression of cardiomyopathy-associated 5 (CMYA5), a master protein that establishes dyads, contributes to dyad disorganization in heart failure and to impaired dyad assembly in hiPSC-CMs, and that a miniaturized form of CMYA5 suitable for delivery via an adeno-associated virus substantially improved dyad architecture and normalized cardiac function under pressure overload. In hiPSC-CMs, the miniaturized form of CMYA5 increased contractile forces, improved Ca handling and enhanced the alignment of sarcomere Z-lines with ryanodine receptor 2, a protein that mediates the sarcoplasmic release of stored Ca. Our findings clarify the mechanisms responsible for impaired dyad structure in diseased cardiomyocytes, and suggest strategies for promoting dyad assembly and stability in heart disease and during the derivation of hiPSC-CMs.

Kevin Shani

Disease Biophysics Group,
John A. Paulson School of Engineering and Applied Science,
Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science

Harvard University

A Cardiac Microphysiological System for Studying Ca²⁺ Propagation via Non-genetic Optical Stimulation

Kevin Shani

Disease Biophysics Group,John A. Paulson School of Engineering and Applied Science,Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science

Harvard University

A Cardiac Microphysiological System for Studying Ca2+ Propagation via Non-genetic Optical Stimulation

Disease Biophysics Group,
John A. Paulson School of Engineering and Applied Science,
Disease Biophysics Group, John A. Paulson School of Engineering and Applied Science

A Cardiac Microphysiological System for Studying Ca²⁺ Propagation via Non-genetic Optical Stimulation