Antisenescence Therapy Improves Function in a Human Model of Cardiac Fibrosis-on-a-Chip.

Cardiac fibrosis is a significant contributor to heart failure and is characterized by abnormal ECM deposition and impaired contractile function. We have previously developed a model of cardiac fibrosis via TGF-ß treatment of engineered microtissues using heart-on-a-chip technology which incorporates human induced pluripotent stem cell-derived cardiomyocytes and cardiac fibroblasts. Here, we describe that these cardiac fibrotic tissues expressed markers associated with cellular senescence via transcriptomic analysis. Treatment of fibrotic tissues with the senolytic drugs dasatinib and quercetin (D+Q) led to an improvement of contractile function, reduced passive tension, and downregulated senescence-related gene expression, an outcome we were previously unable to achieve using standard-of-care drugs. The improvement in functional parameters was also associated with a reduction in fibroblast density, though no changes in absolute collagen deposition were observed. This study demonstrates the benefit of senolytic treatment for cardiac fibrosis in a human-relevant model, supporting data in animal models, and will enable the further elucidation of cell-specific effects of senolytics and how they impact cardiac fibrosis and senescence.

Generation of mature compact ventricular cardiomyocytes from human pluripotent stem cells.

Compact cardiomyocytes that make up the ventricular wall of the adult heart represent an important therapeutic target population for modeling and treating cardiovascular diseases. Here, we established a differentiation strategy that promotes the specification, proliferation and maturation of compact ventricular cardiomyocytes from human pluripotent stem cells (hPSCs). The cardiomyocytes generated under these conditions display the ability to use fatty acids as an energy source, a high mitochondrial mass, well-defined sarcomere structures and enhanced contraction force. These ventricular cells undergo metabolic changes indicative of those associated with heart failure when challenged in vitro with pathological stimuli and were found to generate grafts consisting of more mature cells than those derived from immature cardiomyocytes following transplantation into infarcted rat hearts. hPSC-derived atrial cardiomyocytes also responded to the maturation cues identified in this study, indicating that the approach is broadly applicable to different subtypes of the heart. Collectively, these findings highlight the power of recapitulating key aspects of embryonic and postnatal development for generating therapeutically relevant cell types from hPSCs.

Human cardiac fibrosis-on-a-chip model recapitulates disease hallmarks and can serve as a platform for drug testing.

While interstitial fibrosis plays a significant role in heart failure, our understanding of disease progression in humans is limited. To address this limitation, we have engineered a cardiac-fibrosis-on-a-chip model consisting of a microfabricated device with live force measurement capabilities using co-cultured human cardiac fibroblasts and pluripotent stem cell-derived cardiomyocytes. Transforming growth factor-ß was used as a trigger for fibrosis. Here, we have reproduced the classic hallmarks of fibrosis-induced heart failure including high collagen deposition, increased tissue stiffness, BNP secretion, and passive tension. Force of contraction was significantly decreased in fibrotic tissues that displayed a transcriptomic signature consistent with human cardiac fibrosis/heart failure. Treatment with an anti-fibrotic drug decreased tissue stiffness and BNP secretion, with corresponding changes in the transcriptomic signature. This model represents an accessible approach to study human heart failure in vitro, and allows for testing anti-fibrotic drugs while facilitating the real-time assessment of cardiomyocyte function.

Endothelium-mediated contributions to fibrosis.

Fibrosis, characterized by abnormal and excessive deposition of extracellular matrix, results in compromised tissue and organ structure. This can lead to reduced organ function and eventual failure. Although activated fibroblasts, called myofibroblasts, are considered the central players in fibrosis, the contribution of endothelial cells to the inception and progression of fibrosis has become increasingly recognized. Endothelial cells can contribute to fibrosis by acting as a source of myofibroblasts via endothelial-mesenchymal transition (EndoMT), or by becoming senescent, by secretion of profibrotic mediators and pro-inflammatory cytokines, chemokines and exosomes, promoting the recruitment of immune cells, and by participating in vascular rarefaction and decreased angiogenesis. In this review, we provide an overview of the different aspects of fibrosis in which endothelial cells have been implicated.