Speckle-Tracking Strain Analysis for Mapping Spatiotemporal Contractility of Induced Pluripotent Stem Cell (iPSC)-Derived Cardiomyocytes

Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs) hold tremendous potential for cardiovascular disease modeling, drug screening, personalized medicine, and pathophysiology studies. The availability of a robust protocol and functional assay for studying phenotypic behavior of hiPSC-CMs is essential for establishing an in vitro disease model. Many heart diseases manifest due to changes in the mechanical strain of cardiac tissue. Therefore, non-invasive evaluation of the contractility properties of hiPSC-CMs remains crucial to gain an insight into the pathogenesis of cardiac diseases. Speckle tracking-based strain analysis is an efficient non-invasive method that uses video microscopy and image analysis of beating hiPSC-CMs for quantitative evaluation of mechanical contractility properties. This article presents step-by-step protocols for extracting quantitative contractility properties of an hiPSC-CM system obtained from five members of a family, of whom three were affected by DiGeorge syndrome, using speckle tracking-based strain analysis. The hiPSCs from the family members were differentiated and purified into hiPSC-CMs using metabolic selection. Time-lapse images of hiPSC-CMs were acquired using high-spatial-resolution and high-time-resolution phase-contrast video microscopy. Speckled images were characterized by evaluating the cross-correlation coefficient, speckle size, speckle contrast, and speckle quality of the images. The optimum parameters of the speckle tracking algorithm were determined by performing sensitivity analysis concerning computation time, effective mapping area, average contraction velocity, and strain. Furthermore, the hiPSC-CM response to adrenaline was evaluated to validate the sensitivity of the strain analysis algorithm. Then, we applied speckle tracking-based strain analysis to characterize the dynamic behavior of patient-specific hiPSC-CMs from the family members affected/unaffected by DiGeorge syndrome. Here, we report an efficient and manipulation-free method to analyze the contraction displacement vector and velocity field, contraction-relaxation strain rate, and contractile cycles. Implementation of this method allows for quantitative analysis of the contractile phenotype characteristics of hiPSC-CMs to distinguish possible cardiac manifestation of DiGeorge syndrome. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Differentiation of iPSCs into iPSC-derived cardiomyocytes (iPSC-CMs) and metabolic selection of differentiated iPSC-CMs Support Protocol 1: Culture, maintenance, and expansion of human iPSCs Support Protocol 2: Immunohistochemistry of iPSC-CMs Basic Protocol 2: Time-lapse speckle imaging of iPSC-CMs and speckle quality characterization Support Protocol 3: Enhancement of local contrast of videos by applying contrast limited adaptive histogram equalization (CLAHE) to all frames Support Protocol 4: Evaluation of average speckle size Support Protocol 5: Evaluation of average speckle contrast Support Protocol 6: Determination of relative peak height, Pc(x), of consecutive images acquired from video microscopy of iPSC-CMs Basic Protocol 3: Speckle tracking-based analysis of beating iPSC-CMs Support Protocol 7: Validation of sensitivity of the speckle tracking analysis for mapping the contractility of iPSC-CMs Basic Protocol 4: Data extraction, visualization, and mapping of contractile cycles of iPSC-CMs.

Engineered models of the human heart: Directions and challenges

Human heart (patho)physiology is now widely studied using human pluripotent stem cells, but the immaturity of derivative cardiomyocytes has largely limited disease modeling to conditions associated with mutations in cardiac ion channel genes. Recent advances in tissue engineering and organoids have, however, created new opportunities to study diseases beyond "channelopathies." These synthetic cardiac structures allow quantitative measurement of contraction, force, and other biophysical parameters in three-dimensional configurations, in which the cardiomyocytes in addition become more mature. Multiple cardiac-relevant cell types are also often combined to form organized cardiac tissue mimetic constructs, where cell-cell, cell-extracellular matrix, and paracrine interactions can be mimicked. In this review, we provide an overview of some of the most promising technologies being implemented specifically in personalized heart-on-a-chip models and explore their applications, drawbacks, and potential for future development.

Modeling Cardiomyopathies in a Dish: State-of-the-Art and Novel Perspectives on hiPSC-Derived Cardiomyocytes Maturation

The stem cell technology and the induced pluripotent stem cells (iPSCs) production represent an excellent alternative tool to study cardiomyopathies, which overcome the limitations associated with primary cardiomyocytes (CMs) access and manipulation. CMs from human iPSCs (hiPSC-CMs) are genetically identical to patient primary cells of origin, with the main electrophysiological and mechanical features of CMs. The key issue to be solved is to achieve a degree of structural and functional maturity typical of adult CMs. In this perspective, we will focus on the main differences between fetal-like hiPSC-CMs and adult CMs. A viewpoint is given on the different approaches used to improve hiPSC-CMs maturity, spanning from long-term culture to complex engineered heart tissue. Further, we outline limitations and future developments needed in cardiomyopathy disease modeling.

Human iPSCs and Genome Editing Technologies for Precision Cardiovascular Tissue Engineering

Induced pluripotent stem cells (iPSCs) originate from the reprogramming of adult somatic cells using four Yamanaka transcription factors. Since their discovery, the stem cell (SC) field achieved significant milestones and opened several gateways in the area of disease modeling, drug discovery, and regenerative medicine. In parallel, the emergence of clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (CRISPR-Cas9) revolutionized the field of genome engineering, allowing the generation of genetically modified cell lines and achieving a precise genome recombination or random insertions/deletions, usefully translated for wider applications. Cardiovascular diseases represent a constantly increasing societal concern, with limited understanding of the underlying cellular and molecular mechanisms. The ability of iPSCs to differentiate into multiple cell types combined with CRISPR-Cas9 technology could enable the systematic investigation of pathophysiological mechanisms or drug screening for potential therapeutics. Furthermore, these technologies can provide a cellular platform for cardiovascular tissue engineering (TE) approaches by modulating the expression or inhibition of targeted proteins, thereby creating the possibility to engineer new cell lines and/or fine-tune biomimetic scaffolds. This review will focus on the application of iPSCs, CRISPR-Cas9, and a combination thereof to the field of cardiovascular TE. In particular, the clinical translatability of such technologies will be discussed ranging from disease modeling to drug screening and TE applications.

Human induced pluripotent stem cell-derived cardiomyocytes: insights into molecular, cellular, and functional phenotypes

Disease models are essential for understanding cardiovascular disease pathogenesis and developing new therapeutics. The human induced pluripotent stem cell (iPSC) technology has generated significant enthusiasm for its potential application in basic and translational cardiac research. Patient-specific iPSC-derived cardiomyocytes offer an attractive experimental platform to model cardiovascular diseases, study the earliest stages of human development, accelerate predictive drug toxicology tests, and advance potential regenerative therapies. Harnessing the power of iPSC-derived cardiomyocytes could eliminate confounding species-specific and interpersonal variations and ultimately pave the way for the development of personalized medicine for cardiovascular diseases. However, the predictive power of iPSC-derived cardiomyocytes as a valuable model is contingent on comprehensive and rigorous molecular and functional characterization.

New and TALENted genome engineering toolbox

Recent advances in the burgeoning field of genome engineering are accelerating the realization of personalized therapeutics for cardiovascular disease. In the postgenomic era, sequence-specific gene-editing tools enable the functional analysis of genetic alterations implicated in disease. In partnership with high-throughput model systems, efficient gene manipulation provides an increasingly powerful toolkit to study phenotypes associated with patient-specific genetic defects. Herein, this review emphasizes the latest developments in genome engineering and how applications within the field are transforming our understanding of personalized medicine with an emphasis on cardiovascular diseases.