Human pluripotent stem cell-derived cardiac stromal cells and their applications in regenerative medicine

Fusing spheroids to aligned μ-tissues in a heart-on-chip featuring oxygen sensing and electrical pacing capabilities

Over the last decade, Organ-on-Chip (OoC) emerged as a promising technology for advanced in vitro models, recapitulating key physiological cues. OoC approaches tailored for cardiac tissue engineering resulted in a variety of platforms, some of which integrate stimulation or probing capabilities. Due to manual handling processes, however, a large-scale standardized and robust tissue generation, applicable in an industrial setting, is still out of reach. Here, we present a novel cell injection and tissue generation concept relying on spheroids, which can be produced in large quantities and uniform size from induced pluripotent stem cell-derived human cardiomyocytes. Hydrostatic flow transports and accumulates spheroids in dogbone-shaped tissue chambers, which subsequently fuse and form aligned, contracting cardiac muscle fibers. Furthermore, we demonstrate electrical stimulation capabilities by utilizing fluidic media connectors as electrodes and provide the blueprint of a low-cost, open-source, scriptable pulse generator. We report on a novel integration strategy of optical O₂ sensor spots into resin-based microfluidic systems, enabling in situ determination of O₂ partial pressures. Finally, a proof-of-concept demonstrating electrical stimulation combined with in situ monitoring of metabolic activity in cardiac tissues is provided. The developed system thus opens the door for advanced OoCs integrating biophysical stimulation as well as probing capabilities and serves as a blueprint for the facile and robust generation of high density microtissues in microfluidic modules amenable to scaling-up and automation.

Chemical and mechanical activation of resident cardiac macrophages in the living myocardial slice ex vivo model

Resident cardiac macrophages (rcMACs) are among the most abundant immune cells in the heart. Plasticity and activation are hallmarks of rcMACs in response to changes in the microenvironment, which is essential for in vitro experimentation. The in vivo investigation is confounded by the infiltration of other cells hindering direct studies of rcMACs. As a tool to investigate rcMACs, we applied the ex vivo model of living myocardial slices (LMS). LMS are ultrathin ex vivo multicellular cardiac preparations in which the circulatory network is interrupted. The absence of infiltration in this model enables the investigation of the rcMACs response to immunomodulatory and mechanical stimulations. Such conditions were generated by applying interferon-gamma (IFN-γ) or interleukine-4 (IL-4) and altering the preload of cultured LMS, respectively. The immunomodulatory stimulation of the LMS induced alterations of the gene expression pattern without affecting tissue contractility. Following 24 h culture, low input RNA sequencing of rcMACs isolated from LMS was used for gene ontology analysis. Reducing the tissue stretch (unloading) of LMS altered the gene ontology clusters of isolated rcMACs with intermediate semantic similarity to IFN-γ triggered reaction. Through the overlap of genes affected by IFN-γ and unloading, we identified Allograft inflammatory factor 1 (AIF-1) as a potential marker gene for inflammation of rcMACs as significantly altered in whole immunomodulated LMS. MicroRNAs associated with the transcriptomic changes of rcMACs in unloaded LMS were identified in silico. Here, we demonstrate the approach of LMS to understand load-triggered cardiac inflammation and, thus, identify potential translationally important therapeutic targets.

Fibro-fatty remodelling in arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (AC) is an inherited disorder characterized by lethal arrhythmias and a risk to sudden cardiac death. A hallmark feature of AC is the progressive replacement of the ventricular myocardium with fibro-fatty tissue, which can act as an arrhythmogenic substrate further exacerbating cardiac dysfunction. Therefore, identifying the processes underlying this pathological remodelling would help understand AC pathogenesis and support the development of novel therapies. In this review, we summarize our knowledge on the different models designed to identify the cellular origin and molecular pathways underlying cardiac fibroblast and adipocyte cell differentiation in AC patients. We further outline future perspectives and how targeting the fibro-fatty remodelling process can contribute to novel AC therapeutics.

[Effects of two common acellular methods on the physicochemical properties of dermal acellular matrix]

At present, acellular matrix is an effective replacement material for the treatment of skin damage, but there are few systematic evaluation studies on its performance. The experimental group of this study used two decellularization methods to prepare the matrix: one was the acellular matrix which sterilized with peracetic acid first (0.2% PAA/4% ethanol solution) and then treated with hypertonic saline (group A), the other was 0.05% trypsin/EDTA decellularization after γ irradiation (group B); and the control group was soaked in PBS (Group C). Then physical properties and chemical composition of the three groups were detected. Hematoxylin eosin (HE) staining showed that the acellular effect of group B was good. The porosity of group A and B were both above 84.9%. In group A, the compressive modulus of elasticity was (9.94 ± 3.81) MPa, and the compressive modulus of elasticity was (12.59 ± 5.50) MPa in group B. There was no significant difference between group A or B and group C. The total content of collagen in acellular matrix of group A and B was significantly lower than that of group C (1. 662 ± 0.229) mg/g, but there was no significant difference in the ratio of collagen Ⅰ/Ⅲ between group B and group C. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that there was no significant difference in microstructure. Qualitative detection of fibronectin and elastin in each group was basically consistent with that in group C. Therefore, acellular matrix of group B had better performance as scaffold material. The experimental results show that the acellular matrix prepared by γ-ray sterilization and decellularization of 0.05% Trypsin enzyme/EDTA could be used for the construction of tissue-engineered skin. It could also provide reference for the preparation and mounting of heterogeneous dermal acellular matrix. It was also could be used for electrostatic spinning or three-dimensional printed tissue engineered skin scaffold which could provide physical and chemical parameters for it.

Developmental lineage of human pluripotent stem cell-derived cardiac fibroblasts affects their functional phenotype

Cardiac fibroblasts (CFBs) support heart function by secreting extracellular matrix (ECM) and paracrine factors, respond to stress associated with injury and disease, and therefore are an increasingly important therapeutic target. We describe how developmental lineage of human pluripotent stem cell-derived CFBs, epicardial (EpiC-FB), and second heart field (SHF-FB) impacts transcriptional and functional properties. Both EpiC-FBs and SHF-FBs exhibited CFB transcriptional programs and improved calcium handling in human pluripotent stem cell-derived cardiac tissues. We identified differences including in composition of ECM synthesized, secretion of growth and differentiation factors, and myofibroblast activation potential, with EpiC-FBs exhibiting higher stress-induced activation potential akin to myofibroblasts and SHF-FBs demonstrating higher calcification and mineralization potential. These phenotypic differences suggest that EpiC-FBs have utility in modeling fibrotic diseases while SHF-FBs are a promising source of cells for regenerative therapies. This work directly contrasts regional and developmental specificity of CFBs and informs CFB in vitro model selection.

Telomerase/myocardin expressing mesenchymal cells induce survival and cardiovascular markers in cardiac stromal cells undergoing ischaemia/reperfusion

Cardiac stromal cells (CSCs) contain a pool of cells with supportive and paracrine functions. Various types of mesenchymal stromal cells (MSCs) can influence CSCs in the cardiac niche through their paracrine activity. Ischaemia/reperfusion (I/R) leads to cell death and reduction of the paracrine activity of CSCs. The forced co‐expression of telomerase reverse transcriptase (TERT) and myocardin (MYOCD), known to potentiate anti‐apoptotic, pro‐survival and pro‐angiogenic activities of MSCs isolated from the adipose tissue (AT‐MSCs), may increase CSC survival, favouring their paracrine activities. We aimed at investigating the hypothesis that CSCs feature improved resistance to simulated I/R (SI/R) and increased commitment towards the cardiovascular lineage when preconditioned with conditioned media (CM) or extracellular vesicles (EV) released from AT‐MSCs overexpressing TERT and MYOCD (T/M AT‐MSCs). Murine CSCs were isolated with the cardiosphere (CSps) isolation technique. T/M AT‐MSCs and their secretome improved spontaneous intracellular calcium changes and ryanodine receptor expression in aged CSps. The cytoprotective effect of AT‐MSCs was tested in CSCs subjected to SI/R. SI/R induced cell death as compared to normoxia (28 ± 4 vs 10 ± 3%, P = .02). Pre‐treatment with CM (15 ± 2, P = .02) or with the EV‐enriched fraction (10 ± 1%, P = .02) obtained from mock‐transduced AT‐MSCs in normoxia reduced cell death after SI/R. The effect was more pronounced with CM (7 ± 1%, P = .01) or the EV‐enriched fraction (2 ± 1%, P = .01) obtained from T/M AT‐MSCs subjected to SI/R. In parallel, we observed lower expression of the apoptosis marker cleaved caspase‐3 and higher expression of cardiac and vascular markers eNOS, sarcomeric α‐actinin and cardiac actin. The T/M AT‐MSCs secretome exerts a cytoprotective effect and promotes development of CSCs undergoing SI/R towards a cardiovascular phenotype.

Modeling Precision Cardio-Oncology: Using Human-Induced Pluripotent Stem Cells for Risk Stratification and Prevention

Purpose of Review

Cardiovascular toxicity is a leading cause of mortality among cancer survivors and has become increasingly prevalent due to improved cancer survival rates. In this review, we synthesize evidence illustrating how common cancer therapeutic agents, such as anthracyclines, human epidermal growth factors receptors (HER2) monoclonal antibodies, and tyrosine kinase inhibitors (TKIs), have been evaluated in cardiomyocytes (CMs) derived from human-induced pluripotent stem cells (hiPSCs) to understand the underlying mechanisms of cardiovascular toxicity. We place this in the context of precision cardio-oncology, an emerging concept for personalizing the prevention and management of cardiovascular toxicities from cancer therapies, accounting for each individual patient’s unique factors. We outline steps that will need to be addressed by multidisciplinary teams of cardiologists and oncologists in partnership with regulators to implement future applications of hiPSCs in precision cardio-oncology.

Recent Findings

Current prevention of cardiovascular toxicity involves routine screenings and management of modifiable risk factors for cancer patients, as well as the initiation of cardioprotective medications. Despite recent advancements in precision cardio-oncology, knowledge gaps remain and limit our ability to appropriately predict with precision which patients will develop cardiovascular toxicity. Investigations using patient-specific CMs facilitate pharmacological discovery, mechanistic toxicity studies, and the identification of cardioprotective pathways. Studies with hiPSCs demonstrate that patients with comorbidities have more frequent adverse responses, compared to their counterparts without cardiac disease. Further studies utilizing hiPSC modeling should be considered, to evaluate the impact and mitigation of known cardiovascular risk factors, including blood pressure, body mass index (BMI), smoking status, diabetes, and physical activity in their role in cardiovascular toxicity after cancer therapy. Future real-world applications will depend on understanding the current use of hiPSC modeling in order for oncologists and cardiologists together to inform their potential to improve our clinical collaborative practice in cardio-oncology.

Summary

When applying such in vitro characterization, it is hypothesized that a safety score can be assigned to each individual to determine who has a greater probability of developing cardiovascular toxicity. Using hiPSCs to create personalized models and ultimately evaluate the cardiovascular toxicity of individuals’ treatments may one day lead to more patient-specific treatment plans in precision cardio-oncology while reducing cardiovascular disease (CVD) morbidity and mortality.