Cyclic strain has antifibrotic effects on the human cardiac fibroblast transcriptome in a human cardiac fibrosis-on-a-chip platform.

In cardiac fibrosis, in response to stress or injury, cardiac fibroblasts deposit excessive amounts of collagens which contribute to the development of heart failure. The biochemical stimuli in this process have been extensively studied, but the influence of cyclic deformation on the fibrogenic behavior of cardiac fibroblasts in the ever-beating heart is not fully understood. In fact, most investigated mechanotransduction pathways in cardiac fibroblasts seem to ultimately have profibrotic effects, which leaves an important question in cardiac fibrosis research unanswered: how do cardiac fibroblasts stay quiescent in the ever-beating human heart? In this study, we developed a human cardiac fibrosis-on-a-chip platform and utilized it to investigate if and how cyclic strain affects fibrogenic signaling. The pneumatically actuated platform can expose engineered tissues to controlled strain magnitudes of 0-25% - which covers the entire physiological and pathological strain range in the human heart - and to biochemical stimuli and enables high-throughput screening of multiple samples. Microtissues of human fetal cardiac fibroblasts (hfCF) embedded in gelatin methacryloyl (GelMA) were 3D-cultured on this platform and exposed to strain conditions which mimic the healthy human heart. The results provide evidence of an antifibrotic effect of the applied strain conditions on cardiac fibroblast behavior, emphasizing the influence of biomechanical stimuli on the fibrogenic process and giving a detailed overview of the mechanosensitive pathways and genes involved, which can be used in the development of novel therapies against cardiac fibrosis.

Pirfenidone Has Anti-fibrotic Effects in a Tissue-Engineered Model of Human Cardiac Fibrosis.

A fundamental process in the development and progression of heart failure is fibrotic remodeling, characterized by excessive deposition of extracellular matrix proteins in response to injury. Currently, therapies that effectively target and reverse cardiac fibrosis are lacking, warranting novel therapeutic strategies and reliable methods to study their effect. Using a gelatin methacryloyl hydrogel, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and human fetal cardiac fibroblasts (hfCF), we developed a multi-cellular mechanically tunable 3D in vitro model of human cardiac fibrosis. This model was used to evaluate the effects of a promising anti-fibrotic drug-pirfenidone-and yields proof-of-concept of the drug testing potential of this platform. Our study demonstrates that pirfenidone has anti-fibrotic effects but does not reverse all TGF-ß1 induced pro-fibrotic changes, which provides new insights into its mechanism of action.

Metabolic Maturation Increases Susceptibility to Hypoxia-induced Damage in Human iPSC-derived Cardiomyocytes.

The development of new cardioprotective approaches using in vivo models of ischemic heart disease remains challenging as differences in cardiac physiology, phenotype, and disease progression between humans and animals influence model validity and prognostic value. Furthermore, economical and ethical considerations have to be taken into account, especially when using large animal models with relevance for conducting preclinical studies. The development of human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) has opened new opportunities for in vitro studies on cardioprotective compounds. However, the immature cellular phenotype of iPSC-CMs remains a roadblock for disease modeling. Here, we show that metabolic maturation renders the susceptibility of iPSC-CMs to hypoxia further toward a clinically representative phenotype. iPSC-CMs cultured in a conventional medium did not show significant cell death after exposure to hypoxia. In contrast, metabolically matured (MM) iPSC-CMs showed inhibited mitochondrial respiration after exposure to hypoxia and increased cell death upon increased durations of hypoxia. Furthermore, we confirmed the applicability of MM iPSC-CMs for in vitro studies of hypoxic damage by validating the known cardioprotective effect of necroptosis inhibitor necrostatin-1. Our results provide important steps to improving and developing valid and predictive human in vitro models of ischemic heart disease.

In Vivo Retention Quantification of Supramolecular Hydrogels Engineered for Cardiac Delivery.

Recent advances in the field of cardiac regeneration show great potential in the use of injectable hydrogels to reduce immediate flush-out of injected factors, thereby increasing the effectiveness of the encapsulated drugs. To establish a relation between cardiac function and retention of the drug-encapsulating hydrogel, a quantitative in vivo imaging method is required. Here, the supramolecular ureido-pyrimidinone modified poly(ethylene glycol) (UPy-PEG) material is developed into a bioactive hydrogel for radioactive imaging in a large animal model. A radioactive label is synthesized, being a ureido-pyrimidinone moiety functionalized with a chelator (UPy-DOTA) complexed with the radioactive isotope indium-111 (UPy-DOTA-111 In) that is mixed with the hydrogel. Additionally, bioactive and adhesive properties of the UPy-PEG hydrogel are increased by supramolecular introduction of a UPy-functionalized recombinant collagen type 1-based material (UPy-PEG-RCPhC1). This method enables in vivo tracking of the nonbioactive and bioactive supramolecular hydrogels and quantification of hydrogel retention in a porcine heart. In a small pilot, cardiac retention values of 8% for UPy-PEG and 16% for UPy-PEG-RCPhC1 hydrogel are observed 4 h postinjection. This work highlights the importance of retention quantification of hydrogels in vivo, where elucidation of hydrogel quantity at the target site is proposed to strongly influence efficacy of the intended therapy.